How Would an Astronaut Falling Into a Black Hole Die?

ananyo writes "According to the accepted account, an astronaut falling into a black hole would be ripped apart, and his remnants crushed as they plunged into the black hole's infinitely dense core. Calculations by Joseph Polchinski, a string theorist at the Kavli Institute for Theoretical Physics in Santa Barbara, California, though, point to a different end: quantum effects turn the event horizon into a seething maelstrom of particles and anyone who fell in would hit a wall of fire and be burned to a crisp in an instant. There's one problem with the firewall theory. If Polchinski is right, then either general relativity or quantum mechanics is wrong and his work has triggered a mini-crisis in theoretical physics."

Comments

Gravitational tides will kill you

[Anonymous Coward]

long before the astronaut gets to the event horizon. Both can be correct.

Re:Gravitational tides will kill you

[Anonymous Coward]

Heck, considering what we know about the environments around black holes, not only will the gravitational tides kill you before you reach the event horizon, so will the radiation.

Everybody repeat after me: "Black holes ain't yer friend. Don't try to hug them, you will die."

Re:Gravitational tides will kill you

[Anonymous Coward]

If the astronaut gets across the event horizon, then he will never die relative to us. So, there really isn't a problem here as far as I can tell.

Re:Gravitational tides will kill you

[Sarten-X]

Heck, considering what we know about the locations of black holes and the speed of manmade spacefcraft, old age will probably kill you before you get close enough to notice the gravity.

Everybody repeat after me: "Space is big. Don't mind Sarten-X, he is a jackass."

Re:Gravitational tides will kill you

[rwa2]

Yeah, that sounds about right. The last time I read about this... somewhere... it really depended upon the size of the black hole.

Approaching a small black hole, the gradient in gravitational forces closer to the black hole means that e.g. diving head-first into a black hole would mean your head would feel a stronger gravitational pull than your feet and thus your body would be stretched and ripped apart.

Approaching a much more massive black hole with a larger event horizon could reduce that gravitation gradient enough. But of course you'll be much further from the singularity point as well.

Of course, both ignore the particle soup of other things falling into black holes that would surround most actual black holes.... which is what this article is considering. As well as the fact that it's pretty difficult to dive directly into a celestial object vs. falling into it via a gradually decaying orbit (which is what most of the particle soup is doing).

Also, someone say something about frame dragging effects near such large relativistically-moving amounts of mass.

Re:Gravitational tides will kill you

[tnk1]

While yes, one of the things you would have to deal with is the incredibly hot material swirling around the event horizon which, in and of itself, should produce enough X-rays to fry you, I think this article is actually talking more about an actual characteristic of the event horizon, as opposed to what is in orbit around it, or even what is infalling.

In short, space is supposed to look the same to an observer no matter what side of the event horizon they are on. Instead, a special condition where you smack into something that is there beyond what you would expect from a black hole with infalling matter occurs. That "wall of fire" obviously consists of stuff that has entered the event horizon of the black hole, but it is structured in such a way as to form a highly energetic barrier that should not be there based on our current understanding of relativity or quantum mechanics.

Re:Gravitational tides will kill you

[Marxist Hacker 42]

Why has nobody considered the idea that Stephen Hawking might be wrong, and gravity might affect antimatter as much as matter?

Re:Gravitational tides will kill you

[TheNastyInThePasty]

Actually, according to Betteridge's law of headlines, the answer is no! Science loses! The astonaut is fine!

Re:Gravitational tides will kill you

[Penguinisto]

Heck, considering what we know about the environments around black holes, not only will the gravitational tides kill you before you reach the event horizon, so will the radiation.

...if he doesn't collide with any of the other crap being sucked in at retina-rupturing speeds first...

Re:Gravitational tides will kill you

[hawkinspeter]

I don't think that he said that gravity affects anitmatter differently to matter. I thought that gravity affects them both the same amount.

Re:Gravitational tides will kill you

[MightyMartian]

Perhaps you could cite what you are referring to. I know of no statement by Hawking that suggests gravity affects antimatter differently than matter.

Re:Gravitational tides will kill you

[tnk1]

I don't understand. The standard view of antimatter is that gravity very much does affect it in some way equal to matter.

There are a few possibilities that need to be tested, such as if antimatter can cause antigravity in equal, but opposite proportion to how matter warps spacetime to generate gravity, or that antimatter might generate more or less gravity. However, this is only because we have yet to be able to test antimatter properly. The generally accepted hypothesis is actually that antimatter does affect gravity equal to matter.

Re:Gravitational tides will kill you

[wonkey_monkey]

If the black hole is large enough, no, they won't. You could pass the event horizon and barely notice.

Re:Gravitational tides will kill you

[Marxist Hacker 42]

Then why would the particle be affected differently than the antiparticle? Why wouldn't *both* fall into the black hole equally?

Re:Gravitational tides will kill you

[Marxist Hacker 42]

From TFA,

Hawking’s argument basically comes down to the observation that in the quantum realm, ‘empty’ space isn’t empty. Down at this sub-sub-microscopic level, it is in constant turmoil, with pairs of particles and their corresponding antiparticles continually popping into existence before rapidly recombining and vanishing. Only in very delicate laboratory experiments does this submicroscopic frenzy have any observable consequences. But when a particle–antiparticle pair appears just outside a black hole’s event horizon, Hawking realized, one member could fall in before the two recombined, leaving the surviving partner to fly outwards as radiation. The doomed particle would balance the positive energy of the outgoing particle by carrying negative energy inwards — something allowed by quantum rules. That negative energy would then get subtracted from the black hole’s mass, causing the hole to shrink.

If the particle and anti-particle are affected by gravity the same, wouldn't both members fall into the hole at the same rate and recombine on the way down?

And without this effect, why would there be a firewall?

Re:Gravitational tides will kill you

[Marxist Hacker 42]

From TFA:

Hawking’s argument basically comes down to the observation that in the quantum realm, ‘empty’ space isn’t empty. Down at this sub-sub-microscopic level, it is in constant turmoil, with pairs of particles and their corresponding antiparticles continually popping into existence before rapidly recombining and vanishing. Only in very delicate laboratory experiments does this submicroscopic frenzy have any observable consequences. But when a particle–antiparticle pair appears just outside a black hole’s event horizon, Hawking realized, one member could fall in before the two recombined, leaving the surviving partner to fly outwards as radiation. The doomed particle would balance the positive energy of the outgoing particle by carrying negative energy inwards — something allowed by quantum rules. That negative energy would then get subtracted from the black hole’s mass, causing the hole to shrink.

Why would the doomed particle be treated differently by gravity than its partner in the pair? And without this effect, why would there be a firewall to begin with?

Re:Gravitational tides will kill you

[tchuladdiass]

And, on top of that, in the astronaut's time reference, the rest of the universe's time will accelerate exponentially the closer he gets to the event horizon. By the time he actually reaches / crosses it, the black hole would have evaporated due to Hawking radiation, and the rest of the universe would be zillions of years into the future. The entire trip would however only take a few minutes for the astronaut though.

Re:Gravitational tides will kill you

[The Rizz]

The idea is that the two particles form, and one is closer to the black hole than the other. One of them barely falls in, while the other barely makes it out. No difference in how gravity effects them, just a difference in initial positions.

Re:Gravitational tides will kill you

[Guppy]

Then why would the particle be affected differently than the antiparticle? Why wouldn't *both* fall into the black hole equally?

The problem stems from a misconception in your question. Hawking makes no claim that the two are affected differently, and such behavior is not necessary for his model of Hawking radiation; the emission arises from the occasional probability that one of the two virtual particles has the dumb luck to be on a trajectory not intersecting the event horizon.

Although AFAIK, there is also no solid experimental evidence that antimatter is not treated differently by gravity.

Re:Gravitational tides will kill you

[pscottdv]

That's only for small black holes. For large black holes like the one at the center of our galaxy, the tidal forces are small near the event horizon.

Re:Gravitational tides will kill you

[dissy]

The same reason a particle right next to the event horizon feels the black holes gravity stronger than a different particle, say one in your own body, which is very far away from the black hole and thus not pulled on it as much (aka at all)

Are you claiming the particle near the black hole gets pulled in, and magically the particle in your own body light years away should also get pulled in? Then why are you asking why your body particle doesn't get sucked in too?

The answer is distance. Gravity is stronger the less of it you have.

In what you quoted, the mater particle was closer and got sucked in, while the antimatter particle was further and far enough away NOT to be sucked in.

Replace either of those particles with the opposit, make them both matter, or both antimatter.. or just flip both. The exact same thing will happen. The trait of being antimatter or just matter has no effect on it.

Re:Gravitational tides will kill you

[DMUTPeregrine]

They form in slightly different locations, and sometimes one will be just closer and just get over the event horizon while the other doesn't. They're both affected by gravity in the same way.

Re:Gravitational tides will kill you

[MightyMartian]

It has nothing to do with being a matter/anti-matter pair, it has to with the QM effect that one member of the pair will evade the event horizon and the other member won't. It could the antiparticle that gets swallowed up, or it could be that the particle gets swallowed up. If you carefully read what you just quoted, which member of the pair escaped isn't stated. You're mixing up the reference to negative energy with charge and quantum spin.

Re:Gravitational tides will kill you

[not-my-real-name]

Actually this says that one member of the particle-antiparticle pair could fall into the black hole. It says nothing about which one would. Sometimes it could be the particle and sometimes the antiparticle. They are both treated the same by gravity. My understanding is that since the particle-antiparticle are separated by a tiny distance, sometimes one is inside the event horizon and is swallowed by the black hole leaving the other one to escape. Since they don't recombine, the one that is swallowed has negative energy causing the black hole to lose energy. Whether it's the particle or antiparticle is completely random, to the best of my knowledge.

Re:Gravitational tides will kill you

[CTachyon]

Then why would the particle be affected differently than the antiparticle? Why wouldn't *both* fall into the black hole equally?

Both the particle and the antiparticle are affected equally by gravity, but gravity is the weakest force in nature. Think about it: a simple chair, held together by the electromagnetic force, supports you above the ground by counteracting the gravitational attraction of the entire Earth pulling you down.

Since virtual particle pairs start from vacuum, they are always created with equal but opposite momentum. This momentum can't be very big because the attraction between the pair (usually electromagnetic) has to be strong enough to quickly counteract that initial momentum (and bring the particles back together fast enough for them to still count as "virtual"). But just because the momentum can't be very big doesn't mean it can't be big enough for one particle to escape a black hole, if the particles happen to pop into existence with one of them pointing in just the right direction to escape. Hawking predicts that the odds are 50/50 on whether it's the matter particle or the antimatter particle that does the escaping; it has nothing to do with the particles responding differently to gravity.

(Keep in mind that the escaping particle doesn't have to rocket out in a straight line at escape velocity. Instead, it can take a few swings around the black hole in a rapidly decaying orbit, until it slingshots out on a hyperbolic path. The smaller the black hole gets, the more definite the position is for every matter/antimatter particle pair, and by Heisenberg's uncertainty principle applied to position-momentum, this makes it easier for one of the two particles to escape. A smaller black hole also has the bonus that, looking out from just above the event horizon, more directions point away from the black hole, giving more chances to escape.)

You could actually make a black hole that radiates away Hawking radiation with a bias toward antimatter over matter, or vice versa. It's easy: black holes can have an electric charge, so just electrically charge the black hole! Like charges repel, so if the black hole is positively charged, it will preferentially eject positrons instead of electrons. However, the absorbed electrons neutralize the black hole's electric charge, bringing it back to neutral and making the Hawking radiation return to a 50/50 ratio between matter and antimatter.

(We suspect that the universe has a small preference for matter over antimatter, and this is why the universe is made of matter. But this mostly happens for some heavy uncharged mesons, not for lightweight simple particles like electrons. Here, "heavy" means "high energy" means "unlikely to appear in Hawking radiation". So the radiation may not strictly be 50/50, but it should be very close.)

Re:Gravitational tides will kill you

[HuguesT]

Although a common misconception, this is not correct. Please read the article. In the astronaut's frame of reference in freefall, nothing special happens at the event horizon (that is, if there is no firewall after all), and the even horizon is reached in finite time. For time to apparently accelerate like you describe, the astronaut would have to hover near the event horizon. They could not be in free fall.

Re:Gravitational tides will kill you

[HuguesT]

The particles generated at the even horizon would be essentially photons of every wavelength, which are their own anti-particle. This is because photons can have any energy, which is not the case for massive particles. Only very light black holes (with very high energy output) would be able to create anything other than photons.

Re:Gravitational tides will kill you

[RevSpaminator]

Of course, you'd have to live long enough to make the trip without old age finally catching up with you.

Re:Gravitational tides will kill you

[yndrd1984]

No difference in how gravity effects them, just a difference in initial positions.

I think they were asking why the one that escapes is always the one that ends up with positive energy, i.e. we never get 'reverse Hawking radiation' sucking up mass from the larger universe and adding it to the black hole. I vaguely know how this works, but my layman's understanding of QM isn't good enough for a decent explanation, and I don't want to lead others down the wrong path.

Re:Gravitational tides will kill you

[mysidia]

You could drop a chair from an airplane and see... marvel at that incredible force that is gravity, see how it easily defeats that feeble electromagnetic force, and turns what was once a chair into a pile of splinters, and in due time-- they will make their way into the earth...

Both the particle and the antiparticle are affected equally by gravity, but gravity is the weakest force in nature. Think about it: a simple chair, held together by the electromagnetic force, supports you above the ground by counteracting the gravitational attraction of the entire Earth pulling you down.

That's really not a great argument for it. The particles in the chair are bound tightly together, a very short distance from one another.

The entire mass of the earth is not concentrated into a small piece of ground directly beneath your feet, or into a single point in space like a black hole.

Instead, the mass of the earth is distributed over a relatively great distance, and it's not all located directly beneath your feet.

The earth has a non-trivial diameter; and a non-trivial spherical volume over which its entire mass is distributed non-uniformly.

The distance is very great, and the strength of gravity decays by orders by a great amount over any significant distance.

Electromagnetic attraction also decays by a great amount over any significant distance...

Re:Gravitational tides will kill you

[TapeCutter]

barely notice

What you would notice is that you cannot point to the outside of the black hole since space is infinitely curved, meaning that all directions point toward the center (assuming there is such a thing as a singularity). Attempting to power away from the center will paradoxically get you to the center faster. On a big enough black hole you might not notice this for a while, (whatever "a while" means in that context).

Re:Gravitational tides will kill you

[grantspassalan]

Heck, considering what we know about the locations of black holes and the speed of manmade spacefcraft, old age will probably kill you before you get close enough to notice the gravity.

Everybody repeat after me: "Space is big. Don't mind Sarten-X, he is a jackass."

The trouble is that "what we know about black holes" is all theoretical and mathematical. No one has ever directly observed a black hole and thereby shown that these things even exist in the real world. Black holes were invented to explain present-day theories about the motion of stars and galaxies. The same is true of "dark matter" and "dark energy" and other dark fictions. Perhaps it is time to examine some of these widely held theories that require these mathematical fictions. At the center of these hypothetical, theoretical black holes is this mathematical entity that has been called a "singularity". This is another mathematical fiction that can't exist in the known universe.

Mathematics are very useful in describing measured experiments and observations in the physical universe. As soon as mathematics and computer simulations go beyond what is actually observed and measured, it no longer describes the real world were living in. Current cosmological theories are no better than those held by the majority of scientists in the days when everybody thought the Earth is flat and is at the center of the solar system and the universe. It is time for someone like Copernicus to bring these mathematical theorists back into the real world.

In 1929 an astronomer named Edwin Hubble discovered that "red shift" of distant galaxies. Then he made the assumption (belief, faith) about the cause of this observation. Astronomers still base their belief in the expanding universe on this assumption. Anyone who wishes to pursue this further can Google "Halton Arp" and "William Tift".

Re:Gravitational tides will kill you

[quenda]

a "singularity". This is another mathematical fiction that can't exist in the known universe.

Never mind the singularity. Yes, you might say that is a mathematical construct, and not science (quantam mechanics, relativity).
But it is perfectly reasonable to talk about the physics around the event horizon.

Then he made the assumption (belief, faith) about the cause

English not you first language? The word is "hypothesis". And it has since been thoroughly tested.

Re: Gravitational tides will kill you

[ceoyoyo]

That's not correct. The equivalence principal says you won't notice anything happening if you can't see external references. If you we're in a sealed elevator for example. For an outside observer, time stops at the ev

Re: Gravitational tides will kill you

[ceoyoyo]

Ahem, where was I before the new Slashdot mobile interrupted me?

To an outside observer, time stops at the event horizon. Nothing can ever fall through it. Someone falling in would see the universe speeding up, faster and faster, until time was progressing at an infinite rate by the time he hit the event horizon. Presumably either the black hole would evaporate or the universe would end before the infinite amount of time passed necessary for someone to reach the event horizon.

I don't really see the problem - if the firewall exists, it's located in a region of space that is forever inaccessible.

Re:Gravitational tides will kill you

[Sarten-X]

Assuming you're not trolling, that's a nice story, but that's not how science works.

The trouble is that "what we know about black holes" is all theoretical and mathematical.

Usually, the first step in science is to observe something. In the case of black holes, our knowledge of their existence can be traced back to a few experiments, which provided pretty solid evidence against the prevailing theories of aether. The observation that doesn't match the expectation means that the theories aren't right, and must be changed.

In fact, many of today's experiments are simply re-running old trials, but with more precise technology. Rather than dropping rocks off a tower, we can measure how fast individual atoms fall, giving us a more exact understanding of gravity. Usually the results are a perfect match for what's expected, but sometimes they aren't.

Black holes were invented to explain present-day theories about the motion of stars and galaxies.

Next comes the theory. Starting from the results of those experiments, Einstein hypothesized his theories of relativity, which are really little more than a collection of relationships derived from the assumption that the speed of light in a vacuum is constant. His theories explained the results of previous experiments, and importantly, provided a set of formulas that can be used to make predictions for future experiments.

Mathematics are very useful in describing measured experiments and observations in the physical universe. As soon as mathematics and computer simulations go beyond what is actually observed and measured, it no longer describes the real world were living in.

The relationships in the physical world are described with mathematics. Sometimes, when math is insufficient to easily describe a particular relationship, new mathematical forms are invented to accommodate the real world. Ultimately, though, every physicist knows that the mathematical models do not prescribe reality, but describe our understanding of it. Again, we use those models to predict the outcome of future experiments.

At the center of these hypothetical, theoretical black holes is this mathematical entity that has been called a "singularity". This is another mathematical fiction that can't exist in the known universe.

That depends on the rules of the known universe. in 1915, Karl Schwarzchild transformed Einstein's theories of relativity into a form that would require black holes. This means that Einstein's formulas can only be correct if the universe allows black holes. If the universe does not allow black holes, then Einsteins formulas must be wrong - though less wrong than the aether theory they replaced.

Perhaps it is time to examine some of these widely held theories that require these mathematical fictions.

That's what experiments are for.

No one has ever directly observed a black hole and thereby shown that these things even exist in the real world.

Black holes have been observed many times.

In 1929 an astronomer named Edwin Hubble discovered that "red shift" of distant galaxies. Then he made the assumption (belief, faith) about the cau

Re:Gravitational tides will kill you

[nschubach]

I know somehow I'm going to regret asking this...

If a black hole is immense enough to pull in light, which is radiation.. or in this case energy since it isn't radiating(?).. wouldn't the energy kill you?

Re:Gravitational tides will kill you

[grantspassalan]

All so-called "discoveries" of black holes are attributed to their supposedly enormous gravitational effects on their surroundings, but they never themselves have been found. The same is true of dark matter. The link you gave is all about how the gravity supposedly affects the surroundings of a black hole.

http://www.cfa.harvard.edu/seuforum/bh_reallyexist.htm

ALL the observations in that article can be explained by the operation of a force 36 orders of magnitude greater than gravity. This force is electromagnetism as evidenced by cosmic plasmas that can be accurately modeled not only with computers, but with real physical experiments in the lab. Most of the universe is not nicely electrically neutral, like here on earth, but consists of highly charged electrically active plasma. Most atoms in the universe don't have all their electrons nice and neatly orbiting their nuclei.

Scientists are observing immensely powerful cosmic rays and other radiation from many sources in the universe. All this radiation involves the electric force and has nothing to do with gravity. Scientists have postulated that there should be gravity waves and have spent gobs of money to try and detect these, but so far that has been money wasted since they have not found such waves. In addition, there are measurements of immense magnetic fields in space and on the sun. It is a firmly established principle of science, that magnetic fields can be generated easily by the motion of electric charges.

The large-scale universe is controlled by electrical forces that are far greater than gravity. Gravity is only a controlling factor in electrically neutral environments such as we have here in our corner of the universe. Even if only one atom in 100 billion loses one of its electrons, the force generated by this tiny charge imbalance is far greater than the gravity generated by those 100 billion atoms. You can verify that by doing an experiment right in your own home. Just pick up a few bits of Styrofoam with a charged glass or plastic rod. Charge the rod by rubbing it with a silk cloth. The electric charge on the glass rod will easily overcome the gravity generated by the entire Earth.

Re:Gravitational tides will kill you

[jandar]

That depends on the rules of the known universe. in 1915, Karl Schwarzchild transformed Einstein's theories of relativity into a form that would require black holes. This means that Einstein's formulas can only be correct if the universe allows black holes. If the universe does not allow black holes, then Einsteins formulas must be wrong - though less wrong than the aether theory they replaced.

If some (not yet understood) quantum effect would prohibit the mass-density required for a black hole, e.g. the minimum radius of a mass would be 1 ppm above the Schwarzschild Radius, general relativity would have no defect without existence of black holes.

Black holes have been observed many times.

Strong gravitational fields have been observed but no black holes. If the radii of the generating masses are 1 ppm above Schwarzschild Radii the observed effects would be the same as with black holes. There are indications for black holes but no real proof a sure observation would be.

Re:Gravitational tides will kill you

[wonkey_monkey]

What you would notice is that you cannot point to the outside of the black hole since space is infinitely curved

It's only infinitely curved at the singularity. Just because you're beyond the event horizon, that doesn't mean you can't point (or indeed see) outside.

Re:Gravitational tides will kill you

[walter_f]

Tidal forces depend on the size (and thus, on the density or compactness) of the black hole being approached.

If the black hole is a big one (i.e., not a very dense one), like the one that probably is sitting at the center of our galaxy, an astronaut falling into it would only start feeling tidal effects long after having passed the event horizon, being eventually killed already far inside the black hole..

On the other hand, if the black hole is a small (and thus a compact) one, like one having just a couple of masses of our sun, the astronaut would painfully experience the tidal forces long before he (or she) passed the black hole's event horizon, probably being killed before even having reached the horizon, still outside the black hole.

Re:Gravitational tides will kill you

[PNutts]

I'm afraid there would be no retina rupturing. I've seen a documentary about this with Dr Samantha Carter. It's also quite easy to escape the gravity. You just need a big enough explosion between the ship and the centre of the black hole.

Ejecting a few warp cores worked nicely but it still wasn't enough to escape the lens flares.

Re:Gravitational tides will kill you

[grantspassalan]

A much greater sign about how far Slashdot has "fallen" is when ACs like you resort to personal attacks, rather than coming up with decent reasons why you disagree with someone who is willing to not hide behind anonymity. Why don't you study the subject and then tell us all why you disagree with what I posted.

Re:Gravitational tides will kill you

[peawormsworth]

The trouble is that "what we know about black holes" is all theoretical and mathematical. No one has ever directly observed a black hole and thereby shown that these things even exist in the real world. Black holes were invented to explain present-day theories about the motion of stars and galaxies. The same is true of "dark matter" and "dark energy" and other dark fictions.

There doesnt seem to be a lot of good evidence yet for many of the dark fictions. But there is good evidence of a black hole at the center of our own galaxy. The stars orbit near the center of our galaxy in a strange way. To orbit in this manner, we expect to see a large mass in the center, but there is no visiable object there. Im not saying it is perfect evidence, but it really does fit the bill for now. So we do have some compelling real world evidence, where a black hole is the best possible explanation and we didnt invent the theory of a black hole to match that observation.

Re:Gravitational tides will kill you

[peawormsworth]

long before the astronaut gets to the event horizon. Both can be correct.

...or none. The event horizon of a very large black hole could be passed through without notice by an astronaut, if the black hole was the size of our universe. But if the black hole was extremely small, then you would be torn apart by tidal forces long before the event horizon is reached. Like if the black hole was the size of a golfball at your feet, then your feet would feel much stronger accelleration twords it then your head.

the size of the black hole would be relevant to the discussion

Re:Gravitational tides will kill you

[peawormsworth]

If the astronaut gets across the event horizon, then he will never die relative to us. So, there really isn't a problem here as far as I can tell.

I think you are mistaking light for present reality. Just because you could see the astronauts image falling in an dimming and red shifting out of our ability to observe it, doesnt mean that she still exists. That is like claiming that the big bang never finished, because we can still observe it red shifted on the outer regions of the observable universe.

Re:Gravitational tides will kill you

[ByteSlicer]

Instead, it can take a few swings around the black hole in a rapidly decaying orbit, until it slingshots out on a hyperbolic path. The smaller the black hole gets, the more definite the position is for every matter/antimatter particle pair, and by Heisenberg's uncertainty principle applied to position-momentum, this makes it easier for one of the two particles to escape.

Erm, that's not how orbital/slingshot mechanics work. In fact, a mass-bearing particle (from a virtual pair) could never escape a stationary black hole, because it wouldn't have enough energy to do so, and normal orbital mechanics wouldn't increase its energy.

Instead, you'd need a rotating black hole with an ergosphere. This is a weird area where space-time is dragged along the black hole faster than the speed of light relative to outer space. Here it is possible to extract energy from the black hole with what is called the Penrose process, and thus the electrons/positrons may gain enough speed to escape.

Re:Gravitational tides will kill you

[uninformedLuddite]

Your comments often send me back to my books. Thank you.

Re:Gravitational tides will kill you

[grantspassalan]

The trouble is that "what we know about black holes" is all theoretical and mathematical. No one has ever directly observed a black hole and thereby shown that these things even exist in the real world. Black holes were invented to explain present-day theories about the motion of stars and galaxies. The same is true of "dark matter" and "dark energy" and other dark fictions.

There doesnt seem to be a lot of good evidence yet for many of the dark fictions. But there is good evidence of a black hole at the center of our own galaxy. The stars orbit near the center of our galaxy in a strange way. To orbit in this manner, we expect to see a large mass in the center, but there is no visiable object there. Im not saying it is perfect evidence, but it really does fit the bill for now. So we do have some compelling real world evidence, where a black hole is the best possible explanation and we didnt invent the theory of a black hole to match that observation.

If gravity alone is considered as the main or even only force that controls these orbits of the stars, then yes, a massive object should be there to generate the necessary gravity. However, there is another force operative in the universe that is 36 orders of magnitude greater than gravity. It is the electric force and it acts on matter that is not strictly electrically neutral, but that carries a charge. Most of the matter in the universe or even in the solar system is composed of electrically active plasma which responds strongly to electric and magnetic fields. Any time one area of the universe carries a different charge then another, an electric current is set up which is always accompanied by a magnetic field. Scientists recognize that there are vast magnetic fields in space and on the sun. These magnetic fields are generated by the movement of charge, which by definition is an electric current. Black holes, dark matter and other dark fictions are entirely unnecessary in a charged universe governed primarily by the electromagnetic interaction rather than the much weaker force of gravity generated by mass.

If an object of 100 billion atoms loses or gains only one electron, that tiny charge will generate a force many times greater than the gravity attributable to the mass of such an object. You can do an experiment to demonstrate this for yourself. Take a glass or plastic rod and charge it by rubbing it with a silk or nylon cloth. Now bring the charged rod near some small Styrofoam pieces and watch the electric charge on that rod overcomes the gravity of the whole earth. The charge equivalent of the rod is much smaller than one electron in a hundred billion atoms.

Re:Gravitational tides will kill you

[randyleepublic]

Raw milk is the food of the gods, but sugar, in any form, is cancer causing crap!

Re:Gravitational tides will kill you

[Gen_Music]

No, the energy and radiation would be at the singularity, past the event horizon, the 'point of no return'for anything, even light. Everyone here forgets that you will die far far before the event horizon due to the immense strength of the gravity there which would 'spaghetti-fy' you. (Stretch you long and thin as the difference between terminal velocity and strength of gravity at the tip of your body and the base (relative to the hole) makes your legs accelerate faster than your head, rather painfully. Assuming you're going in feet first.)

All the radiation, heat energy etc etc would be past the even horizon or orbiting the black hole outside it at various ranges, it is possible that you could be hit by an orbiting brick or something, but that's a common problem with any celestial body, not just black holes. The radiation however is much lighter and faster and would not be able to orbit at dangerous levels further away than dust, as having no weight and high speeds means you need more gravity exerted on you to trap you in orbit.

Re:Gravitational tides will kill you

[CTachyon]

Instead, it can take a few swings around the black hole in a rapidly decaying orbit, until it slingshots out on a hyperbolic path. The smaller the black hole gets, the more definite the position is for every matter/antimatter particle pair, and by Heisenberg's uncertainty principle applied to position-momentum, this makes it easier for one of the two particles to escape.

Erm, that's not how orbital/slingshot mechanics work. In fact, a mass-bearing particle (from a virtual pair) could never escape a stationary black hole, because it wouldn't have enough energy to do so, and normal orbital mechanics wouldn't increase its energy.

Instead, you'd need a rotating black hole with an ergosphere. This is a weird area where space-time is dragged along the black hole faster than the speed of light relative to outer space. Here it is possible to extract energy from the black hole with what is called the Penrose process, and thus the electrons/positrons may gain enough speed to escape.

I was simplifying things for the audience, and wasn't even remotely about to bring up frame dragging. That said, I'm an interested layman who's never taken a physics class touching GR so correct me if I'm totally off-base, but I'm pretty sure that Hawking's conclusion was initially solved for Schwarzschild black holes, and if so the ergosphere around Kerr black holes clearly doesn't come into it. The region between the photon sphere and the event horizon has no stable orbits, but wouldn't there still be some trajectories that would send a particle out past the photon sphere? (On a more circuitous path than a straight line, I mean.) And the Wikipedia article for the photon sphere says that "[a]ny orbit that crosses [the photon sphere] from the inside escapes to infinity".

I will admit to never having plugged numbers into a tensor equation in my life, so I could be totally bullshitting here.

Re:Gravitational tides will kill you

[CTachyon]

You could drop a chair from an airplane and see... marvel at that incredible force that is gravity, see how it easily defeats that feeble electromagnetic force, and turns what was once a chair into a pile of splinters, and in due time-- they will make their way into the earth...

What's holding up the plane in the first place, giving the chair the potential energy to shatter on the ground below? Oh, right, the electrostatic repulsion of the electrons in the air pushing against the electrons in the plane's wing.

Seriously, though: gravity is 10,000,000,000,000,000,000,000,000,000,000,000,000 times weaker than the electromagnetic force.

Electromagnetic attraction also decays by a great amount over any significant distance...

Both decay 1/d^2, but the chair is electrically neutral (or very close to it), while the Earth is pulling against you with the full might of 10^24 kg of gravitational charge. Because the chair is neutral, it can only hold you up with the residual electromagnetic force, i.e. the fact that electrons and protons aren't evenly smeared throughout the atom's interior, and that's an incredibly weak effect compared to the actual electromagnetic force.

(This, by the way, is why the Electric Universe cranks inhabiting Slashdot are so off-base. Do they really think nobody would notice the un-subtle effects of a force 10^37 times more powerful than gravity?)

Re:Gravitational tides will kill you

[ByteSlicer]

Well, these may well be the most extreme regions in space-time and the maths are some of the most difficult to solve (and honestly way over my head). Plus we would have to be able to marry GR and QM to fully describe black holes.

The way I see it, the vacuum fluctuations can form many kinds of virtual pairs, and when that pair consists of photons, then there is no problem at all since they always move at c and hence can escape the gravitational well (but they will be red shifted due to the extreme gravity). So most of the Hawking radiation will always be EM radiation.

Mass-bearing particles will form with the same small/limited energy from the vacuum, and their momentum and thus initial speed will be small too. In a normal gravitational well they would almost immediately fall back towards the event horizon, due to the extreme gravitation (it requires thrust for any mass to change/leave orbit, and these are not even in orbit).

In the ergosphere of a rotating black hole, nothing can remain stationary relative to the rest of the universe because that would require faster than light movement. This means particles are forced to move, even when initially stationary, and hence they gain momentum, which in turn can lead to the particle escaping the gravitational potential.

Of course, that is when only taking into account gravitational effects. The extreme magnetic fields surrounding black holes will also accelerate charged particles, and will probably have a bigger effect than frame dragging.

Re:Gravitational tides will kill you

[t0mek]

The scientists of the day couldn't really use his system for anything productive

Don't be silly. Kepler was, by all means, a scientist and he based his "Mysterium Cosmographicum" on Copernicus' "De revolutionibus orbium coelestium". Do you really find Kepler's work non-productive?

BTW, both Kepler and Newton were wrong too.

Copernicus came up with quite blasphemous idea that the Earth was not the centre of the universe. He changed completely bonkers model of the Solar System to vaguely correct one, with the Sun in the centre. Copernicus' model predicted the observed backward movement of the planets and few other things. Kepler was one of the few scientists who did not reject the heliocentric model. Kepler refined Copernicus' model 50 years later by changing the reference point from the centre of Earth's orbit to the centre of the Sun and by making orbits elliptical. Newton corrected Kepler's big mistake nearly 100 years later, by coming up with the idea that the gravity, not geometry, is the key ingredient.Yet Newton's equations are wrong by giving the certain result rather than the probability distribution, which makes Newton's work useless for quantum physicists.

I don't get the idea why the 3 scientists came up with major milestones in science but only 2 of them are worthy.

Re:Gravitational tides will kill you

[Bengie]

There is so much wrong with what is above that I don't know where to start

All so-called "discoveries" of black holes are attributed to their supposedly enormous gravitational effects on their surroundings, but they never themselves have been found.

Entirely wrong. Not even theoretically wrong, just factually wrong. Blackholes have been discovered and proven beyond a doubt.

All this radiation involves the electric force and has nothing to do with gravity. Scientists have postulated that there should be gravity waves and have spent gobs of money to try and detect these, but so far that has been money wasted since they have not found such waves.

How are these two subject related? The first part is correct, but then the second part is completely unrelated, like it's trying to make me think the second part can't be true because of the first part. Gravity waves have not been detected directly, but that have been detected indirectly with a 99.9% confidence based on watching the orbital decay of binary neutron stars.

I have no problem entertaining ideas that could be possible, but what you just posted has factual inaccuracies and assumptions, while what seems to be attempts to confuse the reader into linking unrelated subjects,

In order to accept a a wildly new idea, its abstract idea must not conflict with anything that is known to be true. Example. Gravity waves may not be not be real, but something similar to them must be real because we see orbital degradation of binary neutron stars that match the the math near perfectly. Gravity waves are the best option currently, but if you think you can explain it at even a hypothetical abstract level using electrical forces, go right ahead. I am open to any ideas that can pass at least a sanity check.

Re:Gravitational tides will kill you

[Bengie]

We may not need blackholes to explain things, but they do exist.

You talk about how strong these electric and magnetic forces are compared to gravity, yet even in our local solar system, gravity is almost the sole force to govern our orbits. Gravity over-whelms the other forces so much so that all we need is Kepler's laws to extremely accurately model our orbits.

Not to mention that electrical and magnetic forces can be distorted and routed along their medium, which makes it incredibly weak for large distances, even compared to gravity. Actually, gravity is the driving force for many of our electric fields. Two galaxies getting pulled by gravity into each other drives some of the largest electric fields, but these electric fields cannot be stronger than gravity since these fields get their energy from the kinetic energy of the galaxies falling into each other.

What do you think creates the magnetic field of the Sun? It's rotation. What do you think causes its rotation? The matter that spiraled in on itself as gravity attracted that atoms together. So how much energy can the Sun put out from its magnetic field? None more than the energy given to it from gravity.

Lucky for you that against both the electric force caused by ions repelling and the expansion force caused by a vacuum and heat, gravity was able to overcome the both of them and condense our gas cloud into a star.

Re:Gravitational tides will kill you

[grantspassalan]

Funny, ha ha, but really why then, where does that saying come from "the land of milk and honey"?

Re:Gravitational tides will kill you

[grantspassalan]

It seems that you did not read my post very well or had trouble understanding it. The reason that scientists postulate black holes and other dark stuff, is that these fictions are necessary to explain the movement of galaxies and stars IF gravity is the only or primary controlling force that governs these motions. As soon as you add the electric force, the picture changes drastically. What you label as "factual inaccuracies" are only INTERPRETATIONS of what is actually observed based on the assumption that gravity is the only governing force responsible for the observed motions of stars and galaxies.

Re:Gravitational tides will kill you

[grantspassalan]

The ONLY reason why gravity governs our local area of space called the solar system, is that lucky for us the overall charge unbalance between the sun and between the planets is small. Another way of saying the same thing is to say that the atoms of the earth and the other planets are neutral and the overall charge differences of the planets is close to but not quite zero. Most matter in the universe however, in fact the overwhelming majority of it is NOT electrically neutral and therefore is influenced by electric forces which are overwhelmingly stronger than gravity. You can get an idea how much stronger electromagnetic forces are than gravity, by doing the experiment I suggested earlier in this thread.

Tell me about the law of physics that informs us that gravity generates magnetic fields! We KNOW that moving electric charges generate magnetic fields. Our whole modern technological civilization depends on this known law of physics. The sun rotates for the same reason that the disk in the electric meter attached to your house rotates when electric current flows through it. If you want to know more about that, look up "homo polar motor". Any time there is a charge difference between two bodies, an electric current will flow between them. The vacuum of space is a very good conductor of electricity. Man-made vacuum tubes demonstrate this quite well. The so-called "solar wind" is an immense river of electric current associated with the sun. These electric currents are guided by the Earth's magnetic field and cause the upper atmosphere to glow at the poles.

There are vast rivers of electricity flowing over immense distances of hundreds of thousands of light-years in our galaxy and others. When the current density is high enough to excite atoms along the way, these atoms emit light by the same mechanism as a neon sign. NASA has some beautiful pictures of these glowing electric discharges occurring in the vast regions of outer space.

Re:Gravitational tides will kill you

[spiralx]

The energy comes from the black hole itself - every single particle that escapes makes the black hole less massive and therefore smaller. This loss balances the energy required to escape the potential well of the black hole, leaving a grand total of zero, same as to start with.

Re:Gravitational tides will kill you

[tbid18]

long before the astronaut gets to the event horizon. Both can be correct.

Not for large (i.e., supermassive) black holes. You could pass the event horizon without noticing anything (other than possible effects on light, like lensing).

Re:Gravitational tides will kill you

[DrVxD]

Space is big. Really big. You might think it's a long way down to the shops - but that's peanuts compared with space.

We must find out for sure!

[Kenja]

Locate a black hole and start shooting monkeys at it! "Science can not progress without heaps [of monkeys]"

Re:We must find out for sure!

[Hentes]

The problem is that we won't be able to observe what happens to them inside the event horizon. If you want to be sure, you have to go yourself.

Re:We must find out for sure!

[roc97007]

That sounds like a youtube moment.

Re:We must find out for sure!

[roc97007]

"if you want to be sure"... briefly, I suppose.

Re:We must find out for sure!

[HappyHead]

One problem that I see with that, is that the event horizon is defined as the place where gravity is so strong that light can't escape - light can easily escape from 1g, so that's not the event horizon.

I suspect that you're confusing gravity with density - as the black hole's event horizon gets bigger, the density gets lower. I can't remember exactly, but if the event horizon is somewhere around the radius of our solar system, you get an average density around the same as our atmosphere. The gravity's still a heck of a lot higher than 1g at the event horizon though.

Re:We must find out for sure!

[lgw]

Hmm, working this out for myself:

The radius of the event horizon is:

R = 2GM/c^2

a = GM/R^2 = c^4/(4GM)

The units are right, so I think that's right. Setting a = g we get

M = c^4 / 4Gg ~= 3 * 10^42 kg ~= 1.5 * 10^12 solar masses

So, yeah, I was way off.

Still, a trillion-solar-mass black hole could possibly exist in the universe to lob monkeys at, I'm betting on the monkeys surviving the event horizon passage for a while.

Re:We must find out for sure!

[gewalker]

If the gravity at the "event horizon" were 1g, certainly light at the event horizon could go well outside the event horizon (but not to infinity) before the gravity curved it back into the well. If I had a rocket just inside that event horizon, I should be about to fly out of the black hole as well -- my exhaust would all be trapped, but I could move the part of the total ship mass containing me outside of the event horizon by sacrificing the momentum of the exhaust.

An observer at infinity would see the rocket disappear when it dropped below the event horizon, but then reappear after it returned outside the event horizon.

If not, why not?

Re:We must find out for sure!

[lgw]

light can easily escape from 1g

Turns out it can't. Surprising, isn't it? The magnitude of gravity at the event horizon isn't why light can't escape - it's the fact that space itself is effectively rushing into the black hole. There aren't really any good intuitions to be had about conditions at the event horizon.

I'm not good enough to explain it well, but I think of it as the "time" direction points towards the singularity at the event horizon. No matter how good your engines are, you can't apply that thrust in a direction useful for escape.

Re:We must find out for sure!

[David_Hart]

Locate a black hole and start shooting monkeys at it! "Science can not progress without heaps [of monkeys]"

Isn't this how Planet of the Apes got started.... just saying... I, for one, welcome our new black hole traveling monkey overlords...

Re:We must find out for sure!

[TheLink]

Blackholes might not be that uncommon.
http://physicsworld.com/cws/article/news/2013/mar/15/micro-black-holes-could-form-at-lower-than-expected-energies
There are even some theories that some ball lightning could be due to blackholes:
http://en.wikipedia.org/wiki/Ball_lightning#Black_hole_hypothesis

Imagine a tiny blackhole with literally tons of charged particles beyond the event horizon (which is not far away for a tiny blackhole) in close very high speed orbit around it. Those particles might still be affected by magnetic fields, and how about their gravitational effect on the blackhole itself?

Perhaps some real physicists can explain what would happen in such a scenario.

Re:We must find out for sure!

[lgw]

No matter the size of a black hole, gravity at the event horizon is finite. You could always in theory build rockets more powerful than whatever it is. It won't help you.

Newtonian acceleration determines how much gravity you feel, but not how you actually move, near a black hole, because space itself is effectively rushing across the event horizon.

I'm not good enough at this to explain it well, but as I replied to a sibling post, I think of it as if the time axis has rotated to point towards the singularity. As I understand it, the event horizon is where the time axis points at 45 degrees off the center, and no matter how hard you accelerate, you can't quite change your own vector more than 45 degrees off the time axis, so you're stuck.

Maybe we'll get a physics prof to wander past and explain this better!

Re:We must find out for sure!

[Anonymous Coward]

No, light can most certainly escape from 1 G. Gravity IS the curvature of space. The Event Horizon is the point at which escape velocity = c.

Re:We must find out for sure!

[jhol13]

Last I checked, the time will slow down so much that you'd never hit the black hole (event horizon), that is, before the universe will end.

But that was "sometime bronze age" so I might be wrong.

Re:We must find out for sure!

[Baloroth]

No, light can most certainly escape from 1 G.

Not necessarily. Imagine an infinitely large gravitational field (caused by an infinite object an infinite distance away, so that all field lines are parallel to each other). It should be obvious that the "escape velocity" at any point in that field is infinite (no matter how fast you are traveling, you will always stop and start "falling" at some point less than infinity).

Of course, thats a fictional example, but it's a reasonable approximation for an extremely large mass a very long distance away (such as in the case of a supermassive black hole) and shows that escape velocity is not proportional to the gravitational acceleration.

Re:We must find out for sure!

[lgw]

No, light can most certainly escape from 1 G. Gravity IS the curvature of space. The Event Horizon is the point at which escape velocity = c.

G and g are different constants. g measures acceleration, not speed - g and c aren't comparable. Escape velocity is the minimum speed at which you'll "escape" to infinity without acceleration (from an ideal point mass), and it's a property of the mass, not your distance from the mass. Nothing to do with the event horizon.

You don't have to exceed the escape velocity of the Earth to reach the moon, if you have constant thrust. However, no amount of thrust will allow you to escape the event horizon once you've passed it.

The Newtonian acceleration due to gravity at the event horizon is basically irrelevant to escaping a black hole. It is, however, important to surviving long enough to fall that far in!

Re:We must find out for sure!

[s.petry]

The opposite of what you said is to make every variable 0, which yields invalid results just like your infinite variables yield invalid results. It's fine to speculate some numbers, but you can't use zero or infinity as those speculated numbers. It simply does not work.

Re:We must find out for sure!

[thunderclap]

Since the entire universe rotates (if galaxies rotate and super clusters do [as Our sun rotates around the center of the galaxy] then its logical that the whole freaking universe does) its at the center of the universe. Although I'd rather lob Pigs.

Re:We must find out for sure!

[thunderclap]

Conservation of Momentum if I understand it correctly.

Re:We must find out for sure!

[atouk]

Unless we can figure out how to get an LMD (Live Monkey Detector) inside the black hole before we start shooting monkeys at it, Schrodinger is going to have to stock up on banannas so the PETA crowd doesn't complain about monkey neglect.

Re:We must find out for sure!

[nightcats]

The astronaut will enter the BH and then turn into a lower middle class apartment complex. The key factor with this piece is the date tie-in: today is the 100th anniversary of Brooklyn's Ebbets Field. If the Standard Model were valid then the Dodgers would still be here in Bklyn. String theorists correctly point out that Chavez Ravine is a parallel universe at the other end of a BH. Chalk up yet another point for string man and TV star Brian Greene.

Re:We must find out for sure!

[Ironchew]

Last I checked, the time will slow down so much that you'd never hit the black hole (event horizon), that is, before the universe will end.

For an observer outside the black hole, yes. The light bouncing off of the object falling into the black hole gets redshifted more and more, and it never quite appears to fall in.

From the perspective of the thing falling in, it passes through the event horizon without the "redshifting" delay.

Re:We must find out for sure!

[Baloroth]

The opposite of what you said is to make every variable 0, which yields invalid results just like your infinite variables yield invalid results. It's fine to speculate some numbers, but you can't use zero or infinity as those speculated numbers.

Not sure what you're even talking about, setting the numbers to 0 works fine (zero gravitational field is well defined, even if it doesn't exist anywhere). And deriving equations and examples from infinite cases is a routine practice in physics. Many equations are derived from such cases (indeed, quite often you find that assuming a non-infinite field makes deriving an actual equation impossible). If you like, you can pretend the field is simply incredibly large relative to the scale you are interested in. Thats basically what is being said anyways.

Regardless, all we need is a field of such size that at some distance r from mass M escape velocity equals c. We don't even have to guess what that is, in fact, if we stipulate a_g=1G=9.8m/s^2. Swartzhschild radius is 2GM/c^2, a_g=GM/r^2, so M=c^4/(4G*a_g) or a mass of 3.1*10^42kg, about 1/2 the mass of the whole Milky Way galaxy. Larger than any black hole we know of, perhaps, or perhaps larger than a black hole could realistically form, but again: you can definitely have a gravity strength of 1G at an event horizon for a black hole, theoretically.

Re:We must find out for sure!

[painandgreed]

Since the entire universe rotates (if galaxies rotate and super clusters do [as Our sun rotates around the center of the galaxy] then its logical that the whole freaking universe does) its at the center of the universe. Although I'd rather lob Pigs.

Nope. No evidence that the universe rotates. First, there is no evidence of it rotating and people have been looking. Just read a book that talked about it.

Second, I think there is some relativity stuff going on too. For the universe to rotate, there must be something outside the universe for the universe to rotate in relation to.

Re:We must find out for sure!

[archivis]

The center of the universe is...right here. And over there.

Re:We must find out for sure!

[Pfhorrest]

No matter the size of a black hole, gravitational acceleration at the event horizon is c per Planck time. That's not "infinite", but it is maximal. Anything at the event horizon of a black hole will have its velocity increased by c toward the singularity as quickly as theoretically possible. You cannot build a rocket to put out that kind of acceleration in the other direction to keep you in place, because you cannot build a rocket to get you up to c at all, in any amount of time. Your talk about time axes sounds like it's an echo of a description of why you can't build a rocket to get up to c. It has nothing to do with black holes specifically, other than that you would need to get that fast to escape the event horizon of one.

If you were made of light, however, you would be moving at c, and you could orbit at the event horizon. If you're just above the event horizon, you could in theory get moving fast enough to orbit just outside of it. And in orbit, you don't feel any acceleration from gravity; you are free-falling around the black hole, and continually missing it. You could also have some flight path requiring 1g of constant acceleration to keep you from falling in. The size of the black hole doesn't matter for any of that; if you are anywhere outside the event horizon, you can find a flight path that will make you feel any amount of acceleration you want, for as long as you have fuel to maintain that kind of acceleration. (For an orbit, you feel zero acceleration, and so need no fuel and can maintain it indefinitely).

Where the size of a black hole does matter, and what I think you were thinking of in your earlier post about black holes of 100 solar masses or such, is tidal forces. These are the forces which pinch and stretch your body in uneven ways. Imagine you had a tetherball pole in the middle of a schoolyard. You stand far off to the east of it, facing it, with your arms outstretched. The lines from both of your hands, and your elbows, and your nose, toward the tetherball pole, are all roughly westward, so if you were to be pulled toward it, your whole body would be pulled more or less evenly. But if you stand right next to it, with your arms stretched out, your nose is pulled west, but your right hand is now north of it, and your left hand is south of it, so they get pulled south and north respectively, and the pole pulls your hands toward each other. If, like gravity, it also pulls harder the closer to it you are, it will pull your face toward it much harder than it will your hands, and make you smack your nose into it and then hit yourself as your hands fall in behind your head; while from a long ways away, all your body parts are pulled with about the same force.

Likewise with black holes. The closer you are to one, the more the different parts of your body (and spaceship, etc) are pulled in different directions and with different magnitudes. The farther you are from it, the more evenly everything is pulled. A very massive black hole has a very large event horizon, so at the event horizon, you are very far from the center of the black hole, and even though you are still experiencing the same acceleration you would feel at the event horizon of any black hole, it's all pulling you in more or less the same direction, so you could orbit there and suffer no ill effects. Around a small black hole though, even if you were orbiting just above its black hole and feeling no acceleration overall, the parts of you closer to it would need to orbit faster to maintain that effect and so would feel pulled and pinchedcompared to the parts of you further away from it, which would have more speed than they need to orbit and so tend to drift away from it. All in all you would feel pulled in every different direction and your body would be ripped apart. Around a larger black hole, even moving at the same speed to maintain orbit the same distance from the event horizon, all of you would feel roughly the same effects, so you wouldn't even notice them.

Re:We must find out for sure!

[FooAtWFU]

"in fact, if we stipulate a_g=1G=9.8m/s^2. Swartzhschild radius is 2GM/c^2, a_g=GM/r^2, so M=c^4/(4G*a_g) or a mass of 3.1*10^42kg, about 1/2 the mass of the whole Milky Way galaxy." Larger than any black hole we know of, perhaps, or perhaps larger than a black hole could realistically form, but again: you can definitely have a gravity strength of 1G at an event horizon for a black hole, theoretically.

How does this compare with estimates of the masses of the largest quasars?

Re:We must find out for sure!

[painandgreed]

One problem that I see with that, is that the event horizon is defined as the place where gravity is so strong that light can't escape - light can easily escape from 1g, so that's not the event horizon.

No, the event horizon is where the escape velocity equals the the speed of light, not where the gravitational acceleration equals the speed of light. At that point, energy will redshift infinitely before it is able to leave the influence of the black hole. Any matter could move away from the black hole at the event horizon, but it would need an infinite amount of energy to keep from falling back in.

Re:We must find out for sure!

[Baloroth]

The largest we've seen is about 1/100th of that (very roughly, estimates for the largest we know about are about 17 billion solar masses, or 3*10^40kg). So, like I say, probably there isn't a black hole that big.

Re:We must find out for sure!

[lgw]

No matter the size of a black hole, gravitational acceleration at the event horizon is c per Planck time. That's not "infinite", but it is maximal

Fair point. I calculated the mass where the Newtonian acceleration would be g at the event horizon, which won't tell you the path of a test particle but will give you an idea of the gravitational stress you would feel - but you say that farther down.

Do you know the formula for the acceleration of a free falling test particle near a non-rotating black hole?

if you are anywhere outside the event horizon, you can find a flight path that will make you feel any amount of acceleration you want

Pretty sure that would be true inside the even horizon as well.

If you were made of light, however, you would be moving at c, and you could orbit at the event horizon. If you're just above the event horizon, you could in theory get moving fast enough to orbit just outside of it.

No, the photon sphere (place where light orbits) is at 1.5 times the radius of the event horizon. Just inside the photon sphere, light pointed slightly away from tangent will fall in. As you approach the event horizon, light at an ever-steepening angle will fall in, until the horizon itself where light pointed directly away will fall in. (For a non-rotating black hole.)

You could also have some flight path requiring 1g of constant acceleration to keep you from falling in. ... For an orbit, you feel zero acceleration, and so need no fuel and can maintain it indefinitely

Right, though you can't have a circular orbit inside the photon sphere. I guess you could have an "elliptical" orbit with a closest approach between the photon sphere and even horizon, though I wonder if it would actually be an ellipse?

And of course a rotating black hole has an ergosphere, which baffles me, but then I never could get my head around a rotating black hole.

Here a question I've been baffled by recently: maybe you have an answer. We have a large black hole in nearly empty space. An electron falls in. At some point the electron crosses the event horizon of the black hole. When does an electron on the far side of the black hole, near the event horizon, "notice" the charge of the black hole has changed? A black hole all has the same charge, so I'm quite puzzled by this one.

Re:We must find out for sure!

[Chas]

No, light can most certainly escape from 1 G. Gravity IS the curvature of space. The Event Horizon is the point at which escape velocity > c.

Fixed that for you.

Re:We must find out for sure!

[Anonymous Coward]

...no matter how hard you accelerate, you can't quite change your own vector more than 45 degrees off the time axis, so you're stuck.

So, that's when you eject the warp core?

Re:We must find out for sure!

[Alex Belits]

Second, I think there is some relativity stuff going on too. For the universe to rotate, there must be something outside the universe for the universe to rotate in relation to.

No.

Re:We must find out for sure!

[painandgreed]

Second, I think there is some relativity stuff going on too. For the universe to rotate, there must be something outside the universe for the universe to rotate in relation to.

No.

Hey, great. Now we have an absolute frame of reference with the axis that goes through the objective center.

Re:We must find out for sure!

[painandgreed]

Or you can check this out:

"The big bang theory assumes that when the Universe was created there was nothing outside it. Therefore, for the big bang to be rotating when it occurred suggests that it was rotating relative to something. “The simple answer is that it was spinning relative to other Universes in some larger space,” says Longo. “We could never see outside of our Universe in principle, but if we could show that the present Universe still retains the initial angular momentum within its galaxies, it would be evidence that our Universe exists within some larger space.”"

Re:We must find out for sure!

[Hentes]

It will last for the rest of your life.

Re:We must find out for sure!

[bcrowell]

No matter the size of a black hole, gravitational acceleration at the event horizon is c per Planck time.

Total nonsense, modded up to 5 on slashdot. Oh, well.

The gravitational acceleration at the event horizon can take on any value. It depends on the size of the black hole. This is determined by general relativity, which is a classical theory. Because it's a classical theory, it has nothing to say about the Planck time.

Re:We must find out for sure!

[CrimsonAvenger]

No, light can most certainly escape from 1 G. Gravity IS the curvature of space. The Event Horizon is the point at which escape velocity = c.

Escape speed is SQRT(2rg), where r is the radius and g is local gravity at that radius.

Which means that for escape speed = c and g = 9.8 m/s^2, r is somewhere around 177 light days.

Mass required to produce 1g at 177 light days is somewhere in the low trillions of solar masses.

So you'd need a honking big black hole (probably bigger than currently exists), but not an impossibly huge one.

Note that, if you're really bored, it's possible to guesstimate the event horizon of the Universe. Lot of guesswork (hundreds of billions of galaxies, hundreds of billions of stars per, average mass per star, effects of Dark Matter, that sort of thing) involved of course. Last time I tried to guesstimate, using midddle-of-the-road assumptions (which are probably wrong, since this was 30 years ago), the event horizon matched up pretty well with the age of the Universe - ~15 billion lightyears....

Re:We must find out for sure!

[Moike]

I think you are mixing your classical Newtonian physics and relativistic physics. The Schwartzschild radius equation accounts for relativistic effects, but the "a = GM/R^2" does not, so it should not be valid near the event horizon.

Re:We must find out for sure!

[Alex Belits]

Rotation requires acceleration toward the center. You don't need absolute frame of reference to detect acceleration.

Re:We must find out for sure!

[Alex Belits]

That's wrong, too.

Re:We must find out for sure!

[slick7]

Locate a black hole and start shooting monkeys at it! "Science can not progress without heaps [of monkeys]"

Better yet, start with banksters, then, politicians, lawyers, mobsters, dictators, car dealers; besides, monkeys are cute and funny. Until they rip off your face, then monkeys.

Re:We must find out for sure!

[MickLinux]

I'm sorry, I thought that spin was a quantum characteristic. have an imbalanced sum of spin quantum numbers, and I would think you'd be rotating.

In other words, you'd be rotating relative to yourself.

Or again, if rotating, you experience centrifugal force due to the centripetal acceleration. So rotation is an internal, not external characteristic. Microscopic primarily, macroscopic only secondarily.

Indeed, conservation of momentum only follows secndarily out of conservation of angular momentum.

And there are 720Â in a circle. Go through 360Â, and you'd think you're facing the same way, but you're upside down. Us macroscopic composite beings lose track of that.

Re:We must find out for sure!

[painandgreed]

If you have a center of the universe, then things are no longer relative.

Re:We must find out for sure!

[painandgreed]

What's that Monty Python skit? Contradiction is not an argument? Unless you can actually provide some sort of citation, I'm just going to have to consider you a troll.

Re:We must find out for sure!

[Dabido]

We shouldn't waste valuable monkeys. Let's shoot politicians at it instead.

Re:We must find out for sure!

[justthinkit]

You are mixing up two concepts, trying to use one to prove the other.
.

The Good -- "The Event Horizon (of a Black Hole) is the point at which escape velocity = c."

The Bad -- "light can most certainly escape from 1 G". We have no idea what the g forces are at the event horizon of a Black Hole are, until we calculate them. Gravity is proportional to the two masses involved, and inversely proportional to the distance between them. Saying that light can escape from 1 G is ignoring just about everything.

Scenario 1: On Earth, with gravity of 1 G, light can certainly escape.

Scenario 2: At some distance d from a Black Hole of mass M, a photon may or may not be able to escape. Irrespective of whether d is less than, equal to or greater than the event horizon. In short, it depends...

The Ugly -- "Gravity IS the curvature of space." This sentence is featured prominently in Brian Greene's "The Elegant Universe", with B.G. using it to proclaim how Einstein explained gravity so well. Unfortunately, the sentence explains absolutely nothing. It describes the *effect* of gravity, and otherwise leaves gravity as a black box...encouraging people to use "bowling ball on grid" explanations for the next 80 years...despite physicists (including B.G. in T.E.U.) admitting how wrong it is.

Shameless plug -- My own conjecture on gravity.

Re:We must find out for sure!

[spiralx]

This is Mach's Principle, and one of the things Einstein thought about while thinking up General Relativity. However, GR doesn't answer the question, and formulations such as Godel's universe break it in strange ways.

Quantum mechanics and relativity

[yo303]

We already know that QM and relativity can't both be true. Each theory is very good at predicting things in its realm, but they are mutually exclusive.

Re:Quantum mechanics and relativity

[Entropius]

This isn't true.

QM and *special* relativity get along just fine. When you combine them in a simple way you get predictions like antimatter, the fine structure of the hydrogen atom, and so on. If you do this in a more detailed way, using quantum field theory, you get the fantastically accurate predictions of quantum electrodynamics, the theory of quantum chromodynamics that can't be solved with pen and paper but which still gives accurate predictions when done on supercomputers, and so forth.

And there's nothing forbidding QM from playing nice with general relativity, either; we just don't know how it works yet. There are some models, like lattice quantum gravity, that seem quite promising.

Re:Quantum mechanics and relativity

[pauljlucas]

And there's nothing forbidding QM from playing nice with general relativity, either; we just don't know how it works yet. There are some models, like lattice quantum gravity, that seem quite promising.

Whatever happened to M theory (the successor to string theory)?

Re:Quantum mechanics and relativity

[jhol13]

007 destroyed his sanity.

Re:Quantum mechanics and relativity

[Entropius]

It's around and people think about it, but it's not what I would call "promising" I suppose, simply because it can predict gravity -- or many other things, just because it has so many free parameters. But it could be an answer, too.

I mentioned lattice quantum gravity as a fairly well-constrained thing: people are doing simulations on supercomputers as we speak to understand its properties and to see if it correctly reduces to GR in the classical limit.

Re:Quantum mechanics and relativity

[Livius]

And there's nothing forbidding QM from playing nice with general relativity, either; we just don't know how it works yet.

Translation: As currently formulated, at least one of quantum mechanics and general relativity is wrong, although like Newtonian mechanics or pre-relativistic optics, they will undoubtedly continue to be practical and very accurate approximations.

We knew this as soon as quantum mechanics was developed.

Re:Quantum mechanics and relativity

[MightyMartian]

We know no such thing. In fact both appear to be true, the problem being that we don't have an overarching theory that explains how that is so.

Re:Quantum mechanics and relativity

[Hentes]

But in order to be able to predict things "in their own realm" we need to separate those realms, and describe the interactions between them. The cosmic censorship hypothesis promised that both theories are only simultaneously relevant inside an event horizon, which would separate us from that contradiction. But this new calculation suggests that the contradiction escapes the black hole and creeps out to the surface of the horizon.

Re: Quantum mechanics and relativity

[meta-monkey]

I think the word you're looking for is not "wrong" but "incomplete." It's not that you try to solve the same problem, once using QM and once using GR and get two different answers, so one must be "wrong."

It's that QM explains (and by "explains" I mean "has equations that let us make accurate predications") about lots and lots of particle interactions, from EM interactions resulting in absorption spectra of atoms and molecules to weak interactions governing nucleic decay, but not gravity. Not "QM gives the wrong answers for gravity," but "doesn't mention gravity." Gravity doesn't flow from QM, can't be derived from QM and seems to be wholly unnecessary from a QM-centric view of the way the universe works.

So QM tells us most everything else particles do, but acts like gravity isn't there. But gravity is there, so something is missing from QM.

Re:Quantum mechanics and relativity

[sjames]

Actually, all we really know is that QM and relativity together are not complete because we have no bridge to get from one to the other.

We cannot yet conclude that one or the other is actually incorrect though TFA discusses work that MAY bring us to such a conclusion.

Re:Quantum mechanics and relativity

[ArsonSmith]

Too many pbrains to understand it.

Re:Quantum mechanics and relativity

[ArsonSmith]

Newtonian physics is like the user manual while general relativity is like the engineering manual. Quantum mechanics, string theory and M theory are more like the design blueprints.

Re:Quantum mechanics and relativity

[GargamelSpaceman]

I am SO unqualified to talk about stuff like this, but it seems to me, only reading what I read in TFA, that the supposed firewall arises from the energy released by severing an entanglement 'bond' between a particle and it's twin that falls into the black hole. The severing is done so that the particle can remain entangled with all the particles that fell in before it and with the rest of the universe thereby preventing information from being lost when particles fall in to the black hole.

        This severing is supposedly necessary because a particle can not be fully entangled with two independent systems at the same time. But the entanglement need not be severed if the systems are not independent.

        What constraints does being entangled with particles which are fully entangled with a sequence of particles inside a black hole place on the universe? I.E. what would the implications of this be? Why are they so attached to the innards of black holes being independent of the outsides?

Puff puff. ( eyes get red ).

Spaghetti

[puddingebola]

You would be stretched out into Spaghetti!! I saw the movie! Stephen Hawking said so himself.

Re:Spaghetti

[Takatata]

True, but this does not rule out, that the Spaghetti is burned from one end to the other.

Re:Spaghetti

[PPH]

.... becoming one with the FSM.

Re:Spaghetti

[PolygamousRanchKid]

Maybe you would get turned into Dark Matter . . . ? All that stuff that we know nothing about has to be coming from somewhere . . .

Re:Spaghetti

[Anonymous Coward]

Dark matter is made of PEOPLE... PEOPLE!!!

Re: Somebody, quick!

[Anonymous Coward]

The /. I knew and loved a decade ago is gone.

Gravitational time dilation

[PPH]

The astronaut dies of old age?

Re:Gravitational time dilation

[Motard]

Yes, because getting to a black hole will take a long time.

Re:Gravitational time dilation

[Kaptain Kruton]

Yes, because getting to a black hole will take a long time.

Your description of time is to general and relative.

Re:Gravitational time dilation

[Culture20]

The other way around: The universe dies of old age around the astronaut and black hole.

Re:Gravitational time dilation

[Anonymous Coward]

Maybe that's the joke. The astronaut never dies, everything else does. Immortality here we come!

Re:Gravitational time dilation

[WillAdams]

That's the way it was played in _Space, Above and Beyond_ --- I think this was the episode:

http://www.imdb.com/title/tt0706370/

William

Re:Gravitational time dilation

[RoccamOccam]

There was an SF short story in which an interstellar alien being was psychically-linked with a human and was helping her team study a black hole. The alien is unable to escape the gravity well and is quickly destroyed. Unfortunately, for the human, the alien's time frame is different, so the human will experience its psychic scream for her entire life.

Re:Gravitational time dilation

[Anonymous Coward]

You got that exactly backwards.

Refer to Stargate SG-1 episode "A Matter of Time" (Season 2 Episode 16): "SG-10 is stranded on planet P3W-451, which is close to a newly formed black hole. The SGC opens the gate to find out what happened, but they cannot shut it down afterwards. Soon they realize that since the planet is near to a black hole, its intense gravity is causing time dilation, so if they do not shut down the gate very soon, it will destroy the SGC, and in time, the entire planet."

People outside the base have much longer to think about what's happening inside the base. e.g. At one point Hammond spends 18 hours off base while those inside the base think he was only gone for ~20 minutes.

Re:Gravitational time dilation

[xevioso]

You mean spelling.

Re:Gravitational time dilation

[jhol13]

This reminds me of the two unknowns: how can a black hole be created if the matter falling to it can never get there? The another one is of course: how can gravitons escape event horizon and attract anything?

I think good theorists can answer both - I cannot either.

Re:Gravitational time dilation

[dpidcoe]

This was the mechanism for FTL travel in the book, "Forever War". While the ship entering the black hole is ripped apart from the observers reference frame, to the ships reference frame that hasn't happened yet and it pops out the other side.

Re:Gravitational time dilation

[IndustrialComplex]

The good news is that due to the psychic-doppler effect the frequency of the scream shifted so much it was in-psychic-audible.

Re:Gravitational time dilation

[rroman]

Yes. If the blackhole is supermassive, the spaghettification wouldn't take blace before entering the event horizon. The fun fact is, that from a distant observer, the astronaut would never go across the event horizon (due to time dilatation). And by never I mean do mean never. Until the end of time the astronaut will not cross the event horizon.

The next fun fact is, that because of hawking radiation, every blackhole will eventually evaporate. This means, that the astronaut can't actually cross the event horizon. Never.

Re:Gravitational time dilation

[Anonymous Coward]

But that is pretty much what would happen according to all theory, that is what the idea was based on.
Most of SG series is based on working and partial theories, and a few controversial ones too. (like man vs machine consciousness in that life has soul where machine does not)

Re:Gravitational time dilation

[geekoid]

"how can a black hole be created if the matter falling to it can never get there?"

that's not even wrong.

" how can gravitons escape event horizon and attract anything?"
A) They are purely hypothetical. There is no proof of their existence.

B) These hypothetical bosons have no mass.

I am not making an assertions to their existences at this time.

Re:Gravitational time dilation

[BlueLightning]

The good news is that due to the psychic-doppler effect the frequency of the scream shifted so much it was in-psychic-audible.

Well, psych me!

Re:Gravitational time dilation

[newslash.formatblows]

B) what exactly does lack of mass have to do with anything? Light (which can't escape either) is a massless boson.

Re:Gravitational time dilation

[skegg]

Regarding your first point: it wasn't always a black hole. At one point in its life it was already a super-massive object, so perhaps that helps. (?)

Re:Gravitational time dilation

[Anonymous Coward]

Kyrie by Poul Anderson 1969 nebula nominee http://www.isfdb.org/cgi-bin/title.cgi?41235

Re:Gravitational time dilation

[jemmyw]

The another one is of course: how can gravitons escape event horizon and attract anything?

I assume that you don't need a graviton to interact with the gravitational field in the same way that you don't need a higgs boson to interact with the higgs field. The particle is an excitement of the field, it doesn't carry the effect.

Re:Gravitational time dilation

[Anonymous Coward]

How can anything get to somewhere, if somewhere is nowhere? How can something fall into nothing? Black holes and the "singularity" supposedly at their center are a mathematical construct that does not exist in the physical universe. No one has ever seen, heard, touched, or smelled a black hole, except possibly at the rear of some of these theorists that waste taxpayer money running expensive supercomputers that grind out esoteric fictional results that have no semblance to reality. The brains of these taxpayer wasting theorists are composed of dark matter and they are stark naked like that Emperor. I am posting as an AC, because otherwise I would be modded into oblivion by the majority /. crowd that actually believes these esoteric fictions.

Re:Gravitational time dilation

[Sussurros]

The story is called "The Planck Drive" and the author is Greg Egan (the man without a photo ). The story can be found in the book "Luminous" among other places and I highly recommend it.

Re:Gravitational time dilation

[__aawavt7683]

Interesting. You've provoked a response from me, a theoretical hobbyist. :-)

Matter reaching a black hole: by the laws of relativity, which I only know in a casual sense, the matter should become ever close to the event horizon, where all the disassembly and modification will occur. As the matter hits the speed of light, either while orbiting or sinking through the event horizon, the relativistic effects mean that the matter will require an infinite amount of time to change _internally_ -- but externally, from our view, it reaches the speed of light and proceeds into the block hole.

So basically, whatever particle that's entered the event horizon or met the speed of light just before it will not change after it's inside the black hole. But at that point it's pure energy, anyway -- what happens at this matter -> energy conversion stage, who knows. (Does the energy contain a complete snapshot to be able to return to exactly the same state of matter should it be slowed down?) The more interesting result here, I think, is that a black hole is made of dense _energy_, not matter. At least, it was converted to energy at the event horizon and perhaps mashed back to matter at the singularity. Probably a quasi big bang soup-like-state, if anything.

Second, gravitons escaping: I came across an article recently, which I can't find now. It went over subatomic particles, how they interact, what they interact with, etc. Photons are force-carriers that do not interact with other photons. But photons _do_ interact with electrons and other subatomic particles and force carriers. Gravity interacts with basically everything, including the Higgs and photons. It's probable that gravitons do not interact with gravitons, and so there is nothing restricting gravity from exiting a black hole.

More interestingly, if gravitons interact with everything _except_ gravitons, then how are gravitons not blocked after they interact with _one_ thing, such as how we can put up basically anything as a wall against photons? The denser the item, the more photons are blocked. I believe this would apply to anything -- like with neutrinos, put a denser block, and you capture more of them. Except with gravity. It seems to hit the object, interact, and keep on going. (Maybe they just interact far more weakly than any known neutrino, and so many, many, MANY interact, and many magnitudes of order more make it through the object. Perhaps we _could_ place a wall against gravitons. I fear the resultant energy exerted on such a wall.)

SINCE gravitons interact with the matter _and_ energy in the black hole, it would seem the gravity, too, should never be able to escape -- but it does. But then, it feels like the gravity holding a planet together should interact with the planet, and never escape. But it does. Something feels wrong with the graviton.

My personal conundrums: the LHC creators said that any black holes created by the LHC would instantly evaporate. How? If nothing can escape a black hole, then the only energy that can be emitted from a block hole is the gravitons. But how can you get so many gravitons from even a small black hole that it will dissipate in a short time? It sems like even for infintessimally small black holes, it would remain around long enough to interact with _something_ -- and if it interacts with _anything_, then it has that much longer to achieve what it already has -- interaction with something else. Clearly this did not happen, which to me would suggest that there are no black holes. But how can they say that the black holes would evaporate?

Complimentarity Shlomplimentarity

[TechyImmigrant]

The smart money is no-firewall and complimentarity is bunkum.

But I'm not smart, Polchinski is.

They're all Wrong!

[Anonymous Coward]

As my advisor would say, all models, all theories are wrong... the only question is: Are they useful?

Newton is wrong, but the models he developed for large body dynamics are still the foundation of a great deal of stuff. Pick your model from any field, chemistry, biology, physics, genetics, etc... they are all "wrong" ... they are all missing something, but as long as you know the limitations of the model you can still use it to design, predict and understand small pieces of the world.

Re:They're all Wrong!

[Entropius]

This doesn't mean that they're wrong; it means that the region of their applicability is bounded. Dealing with such bounds wasn't done in any formal way in Newton's time, but now we have an entire field of study, of "effective field theories", that are a rigorous way to understand how a complicated model behaves in some limit or other. (The example I am most familiar with is "chiral perturbation theory", which consists of pretending the world is made of protons, neutrons, and pions at low energy, knowing full well that those guys are made of quarks once you squint hard enough but not caring. It turns out that chiral perturbation theory is very useful and powerful.)

Re:They're all Wrong!

[harrkev]

In this case, you have two different theories predicting two different things. It is guaranteed that one of them (or maybe both) are wrong. The only question is: "which one is it?"

Re:They're all Wrong!

[harrkev]

Actually, it is also possible that there is no such thing as a black hole - but cetain parts of the universe just suck. I have known some towns like that.

Re:They're all Wrong!

[blue trane]

Are you claiming that even within the region of applicability, you really know with absolute certainty what is going on? I suspect you are guilty of confirmation bias. The post to which you are responding didn't say theories can't be useful, just that at some level, all models are just that, models.

Disney knew this in 1979

[The Grim Reefer]

Hell is in the black hole. And pray you don't go there with a psychotic red robot.

Bad headline

[SirGarlon]

TFA is an interesting article about a physicist apparently discovering an inherent contradiction between general relativity and quantum mechanics. The "black hole" stuff is really just the context that led to the apparent contradiction: the real issue is much deeper than that. It's depressing that the real underlying hypothesis isn't considered newsworthy, and the editor feels the need to lead with the "black hole" stuff.

Re:Bad headline

[bluefoxlucid]

Polchinski is actually correct, sort of. Everything approaching a black hole is being compressed; you'd be exposed to the burning energy of a hundred thousand million thermonuclear explosions before reaching the event horizon.

Re:Bad headline

[DerekLyons]

That contradictions exist between Newtonian physics, relativity, and quantum mechanics is pretty much old news.

Re:Bad headline

[kakaburra]

Everything approaching a black hole is being compressed; you'd be exposed to the burning energy of a hundred thousand million thermonuclear explosions before reaching the event horizon.

The high temperatures is produced not by things getting compressed, but because breaking bonds between a pair of entangled particles is highly exothermic. Also Polchinski says things get burned at event horizon, not compressed.

Re:Bad headline

[Hatta]

Everything approaching a black hole is being compressed

Really? Don't you accelerate faster as you approach the black hole? Wouldn't that mean your feet would travel faster than your head, pulling you apart like taffy, instead of compressing you?

Re:Bad headline

[geekoid]

There are no contradictions. There are refinements.

Re:Bad headline

[bluefoxlucid]

Black holes draw a lot of shit toward them because gravity. Cosmic gasses are drawn in and compressed, which causes super-heating. Also objects--big space rocks--are drawn through this compressed gas, causing friction and more compression and super-heating. If you drop shit in a black hole, you get an explosion 20 times bigger than the biggest thermonuclear bombs we've built. That's why black holes glow so fucking bright even though they suck in everything up to and including light.

Re:Bad headline

[archivis]

I'm guessing lots of papers get written, as a layman :)

wow

[roc97007]

That would certainly change the end of the movie.

no one escapes the Black Hole

[pezpunk]

i agree the reversed lower playfield can be a bit disorienting at first, but let's not get melodramatic -- since there are no outlanes in the gravity well, a quick SDTM drain is really the only way to die down there, and completing either bank of drop targets opens the re-entry gate anyway.

Re:no one escapes the Black Hole

[dpidcoe]

One of the few posts I've found worth modding that hasn't been modded already, and I'm out of modpoints.

Why Waste an Astronaut?

[avandesande]

Shouldn't we use a convicted murderer or something?

Re:Why Waste an Astronaut?

[pezpunk]

well, technically, wouldn't the convicted murder BECOME an astronaut by definition the moment we shot him into space?

slashdot is really provoking the deep questions today.

Re:Why Waste an Astronaut?

[avandesande]

not according to wikipedia: "An astronaut or cosmonaut is a person trained by a human spaceflight program to command, pilot, or serve as a crew member of a spacecraft."
I wouldn't waste resources training the person.

Re:Why Waste an Astronaut?

[Culture20]

Shouldn't we use a convicted murderer or something?

They behave differently in a vacuum.

Re:Why Waste an Astronaut?

[decipher_saint]

"Just settle down out there, you'll get your $20"
~Cave Johnson

Re:Why Waste an Astronaut?

[hawguy]

Shouldn't we use a convicted murderer or something?

I think there would be plenty of volunteers for a one-way trip to a black hole -- volunteers more willing to make scientific observations than a death-row inmate forced to go.

Besides, what if the inmate banished from earth finds himself released by an atomic shockwave from a planet that his prison-ship flies near and he goes to that planet and finds that he has superpowers granted by the planet's sun, and he wreaks havoc on that planet as a super-villan until someone on the planet with super-powers to match the criminal manages to stop him?

Re:Why Waste an Astronaut?

[brianerst]

Don't worry, I can fix that...

Now, Wikipedia says "In addition, a convicted murderer shot through space toward a black hole for experimental purposes."

Re:Why Waste an Astronaut?

[cdrudge]

I wouldn't waste resources training the person.

Without minimum training, the question as to how they would did wouldn't be answered as they likely would be dead before completely leaving our atmosphere. Instead, we should give them minimal training: Hold your breath.

Re:Why Waste an Astronaut?

[geekoid]

Current definitions include any person who goes into space.Change from specifically trained persons about a decade or so ago.

So you can't go to space and NOT be an astronaut.

Re:Why Waste an Astronaut?

[Quirkz]

What happens then? They make a sequel, of course.

Painfully

[onyxruby]

At this point all we have in conjecture as actually studying what would happen is for all intents and purposes impossible. Are you crushed, burned alive by everything else, toasted by radiation, spaghettified, or some other horrible fate?

The only thing that we /really/ know is that any possible fate you would have from falling into a black hole would be painful. Unless you are killed so quickly your body never has a chance to transmit the signals for excruciating pain. The bottom line is that we really don't know and this is something that is necessarily always going to be a theory.

Re:Painfully

[Livius]

Are you crushed, burned alive by everything else, toasted by radiation, spaghettified, or some other horrible fate?

My guess is all of the above, we just don't know in what order.

Re:Painfully

[VanessaE]

My guess would be toasted by radiation, then burned alive, then spaghettified, then crushed, then some other horrible fate, in that order.

My theory

[Algae_94]

Unicorns would stampede the astronaut as he enters the event horizon. There's one problem with the unicorn theory. If I'm right, then either general relativity or quantum mechanics is wrong.

Re:My theory

[alphatel]

Unicorns would stampede the astronaut as he enters the event horizon.

I think we can all agree the astronaut would die.

Re:My theory

[WillAffleckUW]

Unicorns would stampede the astronaut as he enters the event horizon. There's one problem with the unicorn theory. If I'm right, then either general relativity or quantum mechanics is wrong.

Fairly certain the Space Chipmunks would get him first.

Re:My theory

[Entropius]

Miniature giant space hamsters, actually. They're quite ferocious, and especially fond of eyeballs.

Re:My theory

[brianerst]

Does it have to be an invisible pink unicorn?

Re:My theory

[geekoid]

I can not agree to any such thing.
I have the opinion that it is likely that the astronaut would die; however without know the properties of unicorns, We can't say what would happen.

Re:My theory

[ArsonSmith]

Good riddance, I hate astronauts.

Re:My theory

[SpeedBump0619]

Does it have to be an invisible pink unicorn?

If it's invisible it can't be pink.

I would buy Pink or Invisible Unicorns though, as long as their hooves are crunchy!

Actually I believe both invisible and pink is a logical necessity: If it's at the event horizon light wouldn't be able to escape. Also, I can't imagine a way a unicorn would kill an astronaut that wouldn't involve blood-shed. I'd have to imagine that the unicorn would be covered in a fine mist of blood. So, indeed: Killed by an invisible pink unicorn.

Re:My theory

[Darby]

my guess is that you're talking about an stampede of Unicrons.

Now that post was just unicorny.

He would die of shock

[WillAffleckUW]

Shock at being in a black hole in the first place.

Shock at the radiation that blasted away her face plate.

Shock that we were able to afford to get her that far from Earth, when we're shutting down airports right now.

And then her body would be torn asunder.

Re:He would die of shock

[sideslash]

He would die of shock [...] And then her body would be torn asunder.

So you think a black hole would accomplish a gender change on the subject? Interesting theory.

Re:He would die of shock

[WillAffleckUW]

Well, for all we know, the astronaut had an XXY or XYY change in chromosomes 25 and 26.

Sorry, autocorrect on the subject line.

Re:He would die of shock

[Black Parrot]

Shock at being in a black hole in the first place.

Shock at the radiation that blasted away her face plate.

Shock that we were able to afford to get her that far from Earth, when we're shutting down airports right now.

And then her body would be torn asunder.

Shock at the amount of poop accumulating in your spacesuit.

Re:He would die of shock

[geekoid]

Shock at the amount of poop coming out of everywhere except her butt.

My new hobby

[tfocker4]

Bringing up old physics thought experiments in order to throw the quantum mechanics community into an intellectual crisis.

Re: Somebody, quick!

[Anonymous Coward]

The /. we all knew and loved a decade ago was gone by 1997.

So the consensus is still

[HermDog]

try to avoid falling into a black hole

Re:QM vs Relativity is not a new mini crisis.

[TechyImmigrant]

Right, but this finding gives theoreticians something they can get to grips with in a much more tangible way than the hand-wavey incompatibility of QM and GR.

You may cross alive

[little1973]

I once read that if the black hole is big enough tidal forces will be minimal and you can actually cross the event horizon alive.

This theory has some merit as the universe itself is a black hole from a certain point of view.

Re:You may cross alive

[Anonymous Coward]

It involves a lot of weed.

Re:You may cross alive

[hawkinspeter]

Well, no-one gets out alive.

Re:You may cross alive

[walter_f]

This theory has some merit as the universe itself is a black hole from a certain point of view.

Care to explain this a little better?

One of the top experts in the field (maybe Leonard Susskind?) put it once that some of the most essential characteristics of a black hole the size (and the mass etc.) of the universe would be exactly the same as those of the universe itself.

So, to paraphrase Arthur C. Clarke, maybe one could say:

"A black hole the size of the universe would be indistinguishable from the universe itself."

Re:Black hole argument

[Anonymous Coward]

I thought that black holes were still theoretical. Or have they been scientifically proved, and I'm just an asshat?

They've been observed - just because there's theoretical work being done about something doesn't mean it hasn't been shown to exist.

Magnetic radiation

[ackthpt]

He'd be dead before got close to the thing.

only small BH rips you apart

[peter303]

Due to the tidal grdient across your length. A large BH would have a midel tidal gradient. I dont know the size, but I think its over a trillion solar masses.

Re:Somebody, quick!

[hawguy]

Leave your crappy sitcom references at the door and let the adults talk.

Take the time to read too, you might learn something that isn't some comic book fantasy.

Besides, if anyone knows the answer, it's Dr. Hans Reinhardt.

Re: Somebody, quick!

[Entropius]

That's more than a decade ago. But, in the Slashdot of yore, nobody could do math, so it's all good.

You can't have infinite density

[Viol8]

Infinite density = zero size and something with zero size no longer exists. If something has a presence in spacetime it will have some form of dimension. You can't have "something" that isn't actually there.

Re:You can't have infinite density

[Sardak]

This has always bugged me, too. If, for example, you take the black hole at the center of our galaxy, assume all of its mass is located in a singular location and that it is roughly a sphere with a diameter of one Planck length, you get a density of about 3.88 * 10^141 kg/m^3. Very high, but a far cry from infinite.

Re:You can't have infinite density

[Black Parrot]

Infinite density = zero size and something with zero size no longer exists. If something has a presence in spacetime it will have some form of dimension. You can't have "something" that isn't actually there.

Not everyone thinks the mathematical singularity exists as a reality.

I'm guessing that some quantum effect limits how far it can collapse. Or maybe some kind of time dilation keeps it from ever completing.

Re:You can't have infinite density

[Black Parrot]

I'm also curious how the gravity gets *out*.

Re:You can't have infinite density

[geekoid]

"You can't have "something" that isn't actually there."

Prove it. You do not need to depend on a coordinate system

Re:You can't have infinite density

[geekoid]

Gravity doesn't get anywhere. The black hole bend space towards itself, like any body.

Re:You can't have infinite density

[aled]

Gravity doesn't get anywhere. The black hole bend space towards itself, like any body.

I think that the black hole mass bends spaces.

To an outside observer he'd never die

[TheGoodNamesWereGone]

... He'd just red-shift more and more forever

Re:To an outside observer he'd never die

[Jherico]

This depends on the size of the black hole. The larger the black hole, the smaller the tidal forces at the actual event horizon, in which case you're correct, he just seems to slow down and redshift from an outside observer. However, for a small enough black hole he'll be ripped apart and quite dead long before he reaches the event horizon. If it's small enough to have a hot accretion disk (whether the disk is there or not).

Re: Somebody, quick!

[Jeremiah Cornelius]

How would he die?

Of old age, on the multimillion year journey to the nearest black hole, I suppose.

But don't let me be the one to interrupt your little rec time, on the holodeck. ;-)

If Polchinski is right...

[fahrbot-bot]

Umm... He's a string theorist, so...

Listen to Zombie Feynman kids: Unscientific:

• "I hunger for Braaaaaiiiinns!"
• Uh, try the Physics lab next door.
• "I said brains. All they've got are string theorists."

Q: How Would an Astronaut Falling Into ... Die?

[fnj]

A. Very painfully

Re:Black hole argument

[Hatta]

Yes, black holes have not only been observed, but super-massive black holes have been discovered at the center of every galaxy we've checked.

Well...

[Impy the Impiuos Imp]

I read a different account 20 years ago -- the event horizon was not some infinite destruction area, it was just a one-way door. For supersized black holes the size of the solar system, the gravity gradient was so small you could easily fall in without being ripped apart.

Even larger ones at galactic cores should be even more gentle, from a gravity point of view anyway.

Wait, wait, I can answer this one

[waddgodd]

The astronaut would die of starvation or hypoxia long before they got to the Black Hole, given that the farthest we've sent an astronaut is 250,000 miles (a bit more than one light-second), and the nearest black hole is 1600 light years away, or 5E+10 times as far.

Re:Black hole argument

[meerling]

They've found numerous stellar objects of various sizes that conform to the preditions of black holes. (Mass, diameter, etc) Though none have been directly observed, their 'feeding' does generate a lot of energy that is detected when something falls in. Just recently one that had been relatively quiet for some time gave of a nice 'burp' of radiation as it apparently 'ate' a planet.

Have we been to a black hole? No.
Have we taken photos of an actual black hole? No.
Have we seen gravitational effects that look exactly like what a black hole should have? Yes.
Do those gravitational effects calculate out as something of several to millions of solar masses in a tiny volume that can't exist in any non-black hole way that we are aware of? Yes.
Have we seen the radiation from an accretion disk falling into and being destroyed by a black hole as predicted? Yes.
Is a black hole what astrophysicists think it is? Probably.
Is a black hole what non-scientists (hollywood, general public, dentists, etc) think it is? Probably not.
Do you really exist? This is about black holes, but your existence is only a bit less theoretical than that of a black holes, though some of the specifics of either may not be what is generally thought about them.

And no, a black hole is not god dividing by zero. It's more likely an alien mad scientist multiplying by the square root of negative zero. :D

Misleading

[phorm]

The whole "what would happen to an astronaut" is the misleading sensationalist that's been pollution this site lately. It seems they're really going from "News for Nerds" to "Fox News for people who may buy computer and sciency stuff from places like Thinkgeek" (though thinkgeek is awesome BTW) in order to gain bigger audience.

End result is it drives away the core audience that used to make this site awesome, as it dumbs down the really interesting science parts beyond recognition.

Re:Misleading

[khallow]

The whole "what would happen to an astronaut"

...is part of a collection of classic thought experiments by real scientists which predate the internet. Your concerns are misplaced.

Re:Misleading

[phorm]

It appears there are still some real geeks here (who know more than I).

Thanks for the correction/enlightenment!

Re:Both?

[wierd_w]

(Joke!)

Don't be silly! You become a sheodinger's fireball!

Much like the alive and yet also dead cat of infamous repute, our stalwart and jaunty astronaught is in the *perfect* unobserved/unobservable condition!

He is both alive, and dead, at the same time! The schrodinger's cat is also alive, and dead from poisonous gas!

As such, he can simultaneously survive, be burned to a crisp, or be pulled apart like stringcheese, all at the same time!

Re:Both?

[xevioso]

Unless, of course, one's soul can exist in mere ashes, in which case the second option would be necessary for "you" to die.

Send a probe or a manned flight to a black hole

[AragornSonOfArathorn]

We should test this with hotdogs and marshmallows, and see how they taste.

Re: Somebody, quick!

[Anonymous Coward]

That was when Slashdot IDs were negative numbers. Ahhh... I was so much older then, I'm younger than that now.

Baked by heat and other forms of radiation.

[flayzernax]

Long before any gravitation effect.

Size Matters

[rossdee]

If you fall into a big enough black hole, you die by running out of air in your spacesuit.
Not only is the tidal stress less, but supermassive black holes tend to clear the vicinity of stuff, so if its not 'feeding' there is no radiation to fry you either.

Re:Size Matters

[Penguinisto]

If you fall into a big enough black hole, you die by running out of air in your spacesuit.

Depends on the speed you get up to, right before you cross it. If you travel fast enough, relativity accumulates its vigorish; while you will certainly die as you described, relative to the rest of us it'll take a few million years before your air tank runs dry.

Relativity is wrong

[Myopic]

We all know that general relativity is wrong -- or, not perfectly right. We know that we live in a quantum universe and relativity is not a quantum theory, therefore it is "wrong" in the same way that Newtonian laws of motion are "wrong". It's an unbelievably difficult problem which science is working on. Next question.

Re:Relativity is wrong

[geekoid]

"We all know that general relativity is wrong -- or, not perfectly right"

Oh? care to give an example?

You need to look up what the word wrong is, and then you'll be embarrassed to have used it some incorrectly. i.e. you are wrong.

Re:Relativity is wrong

[Myopic]

"wrong, adj (1) not correct or true"

Relativity is not (quite) correct, hence relativity is (a little bit) wrong. What part of that do you have a problem with? I think I made my good point well.

Leonard Susskind

[Fuzzums]

First answer: Alone.

But I saw this rather interesting video of a lecture by Leonard Susskind : http://www.youtube.com/watch?v=pf0D8A0jRiY
It will probably not answer your question, but it's about black holes and they're very cool! Or hot. Depending on the observer ;)

Re:Leonard Susskind

[Quirkz]

Peacefully in his sleep, not terrified and screaming like his passengers.

Wait, I'm confusing my astronaut jokes and my grandfather jokes again.

Comment removed

[account_deleted]

Comment removed based on user account deletion

Re: Somebody, quick!

[nucrash]

That was quite a while ago. I can't even remember that far back.

Re:There is only one answer

[Black Parrot]

Only from his own perspective.

How can you die from your own perspective? You can be about to die, surely going to die, ... but your perspective doesn't get to make the actual transition.

Re:Black hole argument

[rock_climbing_guy]

If I'm not mistaken, you would have to assume that you are a point-mass in order for this to make sense.

Old Age

[geekoid]

duh. Eventually his bodt would be shredded.

Re: Somebody, quick!

[mooingyak]

Nostalgia ain't what it used to be.

Re:Somebody, quick!

[Penguinisto]

Pfft! Amateur - Dr. Neil deGrasse-Tyson would be the man to call!

After all, he eliminated the planet Pluto, so this black hole business should be only slightly more work for him to do.

Immortal Astronaut FTW

[Qliphah]

I don't believe either theory is right. When falling into a black hole one would be stretched along with space/time. To a corporeal 3rd dimensional being it would be near imperceptible. Much like a 2D drawing on a piece of paper the subject wouldn't feel the bending or stretching if a higher being were to crumple it, tearing would of course be catastrophic on all dimensions but up till that point the astronaut would feel nothing has changed as long as the fabric hasn't been distorted beyond the bounce back point. As the black hole condenses and forces time to slow the astronaut would be trapped in an ever slower and darker situation, provided he had air or a ship he would live indefinitely.

Re:Well....

[geekoid]

"astronaut" - Someone on who has gone into space.
"fall" - 'to descend under the force of gravity"
"Into" - "to the inside of"; Also "toward or in the direction of:"
"black hole" - "an object in space so dense that its escape velocity exceeds the speed of light"
"die" - "to cease to live; undergo the complete and permanent cessation of all vital functions; become dead."
Or possible in this case: "to cease to exist" literally.

"Ass" - You.

Re:Black hole argument

[93 Escort Wagon]

Except for those made by Samsung

Have you ever opened one and checked?

Re:Somebody, quick!

[dragon-file]

Technically speaking Pluto is still there doing the same things its been doing for thousands upon thousands of years. All Dr. Neil deGrasse-Tyson did was reclassify it. Politicians do that all the time. Nothing special.

Incorrect

[geekoid]

You should have read the rest of the paragraph, now you just look like a dumb shit.
I'll put the relative bits here since you son't seem to know how to use Wikipedia:

An astronaut or cosmonaut is a person trained by a human spaceflight program to command, pilot, or serve as a crew member of a spacecraft. While generally reserved for professional space travelers, the terms are sometimes applied to anyone who travels into space, including scientists, politicians, journalists, and tourists.[1][2]
Until 2002, astronauts were sponsored and trained exclusively by governments, either by the military, or by civilian space agencies. With the sub-orbital flight of the privately funded SpaceShipOne in 2004, a new category of astronaut was created: the commercial astronaut.

How does it feel to now even be able to use the most rudimentary modern technologies? Stupid. I would imagine.

Re:Incorrect

[avandesande]

The whole thread was meant to be tongue in cheek, not to mention that wikipedia is a crap reference anyway. You need a drink!

Re: Somebody, quick!

[Jeremiah Cornelius]

My Back Pages.

You get Dylan and Byrds points.

Did they carry the sign correctly?

[caywen]

I did the same calculation, and I came to the conclusion that the black hole would burn to a crisp as soon as it touches the astronaut.

Re:Somebody, quick!

[Penguinisto]

/facepalm

Re: Somebody, quick!

[geekoid]

No, it's still the same. You've just matured to realize it's and actually dog face loon you've been sleeping with, not the hot chick you picked up when you were drunk.

Re: Somebody, quick!

[roman_mir]

To parallel TFS at hand, the Dice Holdings Inc. is the black hole and /. hit a firewall?

Re: Somebody, quick!

[Bengie]

When I started reading /., there were links to Ars talking about how CPU pipelines and cache levels work.

Re: Somebody, quick!

[newcastlejon]

Ah, Ars. People who complain about /. going downhill just need to look at what happened there to be truly grateful for what we still have here.

Re:There is only one answer

[deadweight]

Can you prove this?

Checkbox D

[Empiric]

Or, assuming the Everett Interpretation, the answer to how they would die might be "none of the above"...

http://en.wikipedia.org/wiki/Quantum_immortality

The notion in brief being that for any given situation, however probable death may be, there is some branch in which death does not occur, which consciousness would be compelled to "switch to". Though the physics depth would probably be well beyond me, I'd love to see a detailed analysis incorporating all three of these scenarios.

Welcome to the new Slashdot

[Delirium Tremens]

Slashdot : Fox News for Herds. Stuff that mattered.

Re: Somebody, quick!

[Phase Shifter]

No it isn't gone, it just takes longer to reply because it's crawling back from chasing kids off the lawn.

(Seriously, wait longer before browsing the comments and you'll see it's true).

It's still the same old /. with no proper character support, worse editing, worse stories, worse comments, worse trolls, worse jokes, worse whining, and worse moderation --just like ten years ago! :D

Cptn. Obvious says: "It was 2003 ten years ago". Thanks captain.

It's lacking something--something like overly long JonKatz articles where the "facts" are entirely made up in a thinly-veiled attempt to hide the author's ignorance of which he speaks.

...this screws Disney's black hole ending.

[martiniturbide]

http://en.wikipedia.org/wiki/The_Black_Hole This is why we never get a sequel.

Re: Somebody, quick!

[Zeromous]

Would kill for FIRST POST!!!

Oh I saw the TV adaptation of that

[Zynder]

That was in a Futurama movie- LOVE THE TENTACLE!

(I'm being fecetious, but really why won't you all love the tentacle?)

Okay, why don't we simplyfy it?

[Chas]

"Falling into a Black Hole would be a Really Bad Thing"

'nuff said.

Frederik Pohl's Heechee Novels

[OldManCoyote]

I believe "Beyond the Blue Event Horizon" (1980) explored a situation where a space craft was caught in the event horizon of a black hole.

I'm sure falling in isn't all bad.

[AbRASiON]

http://threewordphrase.com/blackhole.htm

The firewall paradox is already refuted?

[aled]

This article suggests that this theory is already refuted. Perhaps the Nature article has been several months in the pipeline and isn't up to date.
Any physicists can comment?

on todays Mythbusters we look at blackholes

[Joe_Dragon]

on todays Mythbusters we look at blackholes

Re:Black hole argument

[melikamp]

Have we taken photos of an actual black hole? No.

Lensing effects in visible light should count as a photo of a blackhole, IMHO, since the event horizon is theoretically invisible.

And no, a black hole is not god dividing by zero.

Could easily be a god dividing by every real number other than zero, which would be good enough.

Re:Well....

[RevWaldo]

"Joke" - what you don't get.~

.

Re: Somebody, quick!

[TheEffigy]

It's because there are too many kids on the /. lawn these days. Although I recall there were a couple of years I felt the same and left altogether. Perhaps this is a cyclical thing.

slashdot curve in action

[NemoinSpace]

The thing i like most about Slashdot, is the easy access to totally unqualified opinions, whose distribution around the correct answer is an inverted bell curve.

Re:slashdot curve in action

[aled]

The thing i like most about Slashdot, is the easy access to totally unqualified opinions, whose distribution around the correct answer is an inverted bell curve.

You are wrong, like most people in Slashdot... mmh, wait a second...

That's easy

[slick7]

By boredom.

Re: Somebody, quick!

[demonlapin]

The forums are still pretty good. I made the mistake of loading up the front page the other day, though... what a mess.

Incidentally, if you've been around that long, what are some good sites to check out? Don't skip any - even if they're well-known to you and everyone you know, they might be new to me. (I know reddit but would be interested in good sub-reddits, for that matter).

Re:Black hole argument

[grantspassalan]

All present-day theories, including black holes, dark matter, dark energy and other theoretical "stuff" depend on gravity as the controlling force in the large-scale development and operation of the universe. There are some scientists that have come up with a theory that the universe is controlled by a force that is 36 orders of magnitude greater than gravity. It is a force that we are much more familiar with and are able to manipulate to our advantage.

These theories don't require any of the esoteric mathematical inventions, such as black holes and all the rest that the gravity only model needs to explain current observations. These theories depend on plasma physics which allows experiments to be done right here on earth that mimic many of the features we see in the solar system and in the furthest reaches of space.

For example, we to see intense radiation, x-rays specifically, from certain spots in outer space. The conventional INTERPRETATION is as you said attributes it to matter falling into a black hole. Here on earth we can generate similar radiation in x-ray machines and accelerators, by using the electric force acting on charged particles of matter.

Anybody can PROVE to you that they exist by doing a simple experiment. They can accelerate the fist at the end of their arm and smash it into your nose. This device is called a nose smasher. The pain that you experience is registered in your pain detector (brain) and will convince you that they very much exist.

If you want more information on these alternate theories, you can begin your research here:

http://www.thunderbolts.info/wp/eg-contents/

One thing is certain ...

[quax]

... the people watching from the outside would die of boredom.

Re:Black hole argument

[miroku000]

Have we taken photos of an actual black hole? No.

To test whether or not we have photos of black holes, I tried doing a Google image search for "black hole", but I was surprised by the lack of porn on the first page of results and got bored and stopped looking.

Easy way to test

[HeadlessNotAHorseman]

Why don't we send an astronaut into a black hole, but tie a rope onto him or her first? Once they cross the event horizon and make some observations, we just pull the rope and drag them back to the mothership. We could make the rope out of carbon nanotubes or something to give it infinite strength.

Re: Somebody, quick!

[coastwalker]

http://www.perimeterinstitute.ca/video-library
http://www.perimeterinstitute.ca/

I cant find a lecture on the firewall theory right now as the site is down for maintenance but these fine folk can probably tell you all about it,

Though you might want to follow Leonard Susskind's primers on YouTube first

https://www.youtube.com/watch?v=JRZgW1YjCKk

https://www.youtube.com/watch?v=JzhlfbWBuQ8

you're welcome

You're all stupid

[Angrywhiteshoes]

You can't fall in space.

How would the astronaut die?

[tzot]

Painstakingly quickly.

Re: Somebody, quick!

[OeLeWaPpErKe]

Actually the thing that "crushes" the astronaut is the gravity differential over the length of the astronaut. In a "small" (let's say football-sized) black hole that difference is huge, and so the astronaut will get torn apart.

However with a supermassive black hole (and there's never been any other kind detected, they may exist briefly, but that makes the chances of encountering one very small), the differential at the event horizon is tiny.

As for the astronaut, you might think he might have trouble sending nerve impulses from his feet (beyond the event horizon) to his head (outside), however he's guaranteed to fall in faster than any signal can propagate outward, so this is not true. The astronaut will not notice anything (except -maybe- hawking radiation, which will be very weak for large black holes too).

So what do you see when you cross an (realistically sized, ie. huuuuuuuuuuge) event horizon ? Why ... nothing at all. You will see a very, very slight natural luminescence, probably deep in the radio frequence (ie. not visible). Everything will still look normal, exactly like it looked before.

There is also a reason why black holes "look like" the end of time. What does an outside observer see when you fall into a black hole ? Well he sees you slow down, due to time slowing down. An outside observer will never see you actually cross the event horizon, and whatever light you reflect you will reflect "slower" the closer you are to the even horizon. So the light reflecting off of you will fade, but very very slowly. Even hundreds of years after you fell into a black hole, a very sensitive telescope will still be able to construct an image of you and it remains theoretically possible until the end of time (it's going to become damn hard though).

There is also the question of what exactly the edge of the universe is. Objects near the theoretical edge of the universe move away from us at nearly light speed ... which might be what you'd expect to see if these were objects that had just fallen through an event horizon. It makes a kind of sense. The edge of the universe is moving away from us at light speed, but a large black hole would pull in exactly enough space so that any light moving away would travel the distance, and yet still remain just inside the event horizon.

He'll be eaten by

[Puppet Master]

A Grue!.

Re:Somebody, quick!

[Geoffrey.landis]

Sheldon Cooper would probably point out that they are wrong.

Hawking radiation is an effect of the accelerated frame-- it's Unruh radiation, with gravity substituted for acceleration. In a freefall frame, there's no radiation from the event horizon-- in fact, in the freely falling frame, there's nothing particular about the event horizon, it's not different in any way from any other part of space.

If you drop into a black hole, you may get stretched to spaghetti... but you won't get cooked.
(At least, not by quantum effects. The accretion disk, on the other hand, is another story.)

Re: Somebody, quick!

[MouseTheLuckyDog]

Great site, but I always download my videos ( generally to /tmp ) before viewing. Gives a better viewing "experience" [1].
Firefox/Download Helper don't work can you make a suggestion?

[1] I hate that word using it makes me sound like Gates or Jobs selling something.

Re:Somebody, quick!

[dougisfunny]

I don't watch television. In fact, I don't even own one.

Re: Somebody, quick!

[DirtyLiar]

While reading this thread? Of boredom!

A proper astronaut would die of embarrassment

[idommp]

for having gotten into this situation in the first place. Any jury of your peers will rule your death a suicide. Your life insurance isn't going to pay off. When you call home and say, "Houston, We have a problem." they're going to say,"No, we have a cancled program. You have some free time on your hands. Enjoy the ride."

rubbish really rubbish !

[dschinn1001]

there are now black holes ! it is a paradoxon. also when there is a black hole there hast be a white hole visible too ! this is a double paradoxon ! Prove is: astronomers are only watching into their electricity cable ! no matter, if they have mirror lenses or optical lenses . . .

I would think...

[DiEx-15]

...that the amount of radiation and heat black holes would create would burn the person up long before they ever got anywhere near the event horizon.

Assuming that they even survived that, the gravity pull alone would crush them like a grape a long distance away from the event horizon.

space time?

[Meyaht]

Wouldn't time slow down for the person, leaving him to starve to death?

Thought experiment.

[DarthVain]

If one could remotely create an identical sized black hole equidistant from your current location in an event horizon but with a counter rotation, would the forces cancel each other out allowing for a "stable" location preventing you from being sucked into either one?

Additionally if they are rotating in the same direction would you be catapulted out of the event horizons at those a fore mentioned spectacular speeds?

I am I guess making the assumption that these things actually rotate as I don't really know. I am also sort of curious about what would determine the direction of rotation in the first place, the whole toilet flush in NA VS Aus. example comes to mind...

Gravity Drive

[DarthVain]

Or it folds space and opens a portal to another dimension that resembles Hell very much.

Either way, you are going to Hell...

Pull the plug

[DarthVain]

More like God poking holes in the universe, and it draining from high to low pressure. It is probably pretty boring after awhile.

Heyyy...

[GPS Pilot]

My dentist happens to know 104% more about black holes than you, insensitive clod!