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Black Holes 'Do Not Exist,' Contends Physicist
SpaceAdmiral writes "Nature reports that, according to a physicist at the Lawrence Livermore National Laboratory in California, 'It's a near certainty that black holes don't exist.' George Chapline argues that the collapse of massive stars is more likely to lead to dark energy stars. These dark energy stars behave somewhat like a black hole outside of the surface, but the negative gravity inside could cause matter to 'bounce back out again.'"
Here is his actual article (PDF).
They created something that behaves like a black hole. If the theory about dark energy stars is right, it could have been a ball of dark energy instead.
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No, "dark energy" denotes energy which is in a form which does not interact with most of the universe, or interacts very weakly. Just like "dark matter" (eg neutrinos) interacts very weakly, with zillions of them passing through the earth with little effect.
Daniel
Carpe Diem
They were not even sure that it was really a black hole at all and it lived for quite a few orders of magnitude shorter than seconds. Femtosecs, IIRC.
Cause small ones are unstable. No. Yes.
There is an enormous amount of work that makes Quantum Mechanics play well with relativity.
The problem with quantum mechanics and relativity is that the theory of quantum mechanics only works well when gravity is so weak that it can be neglected. Particle theory only works when we pretend gravity doesn't exist. On the other hand, general relativity only works when we pretend that the Universe is purely classical and that quantum mechanics is not needed in our description of nature.
The solution is string theory. This website has a nice list of expirements that have been done in favor of string theory.
No. The event horizon is the distance at which the escape velocity is the speed of light - you can't travel at the speed of light, so it's impossible to escape. (That's something of a simplification, but it will do) I suppose you could have an electric version of a black hole (not magnetic though, it would have to be a magnetic monopole [magnet with only one pole, rather than the usual north and south poles] which are thought not to exist). An object with sufficent charge that no charge object could escape it. Neutral opjects would still be able to leave, of course, and the event horizon would be different depending on the charge of the object trying to leave...
He says that electron-positron anihilation could account for the radiation observed at the center of the galaxy. The radiation produced when an electron collides with a positron is of a very specific wavelength - I think someone would have noticed if the radiation at the centre of the galaxy was at that wavelength, rather than a distribution of wavelengths in the way you would expect from a very hot object (superheated plasma in this case).
You're making a very dangerous generalized assumption there. Both forces go like 1/r^2. Both forces get multiplied by something to determine its strength. In normal lab conditions, you aren't going to be able to gather enough mass to exceed the magnetic fields we are able to create. However, it's much harder to create a magnetic field that can, say, carry enough force to make the moon orbit the earth. Remember, to form a magnetic field you need a huge number of charges moving roughly in unison. To form a gravitational field you just need a big hunk of matter. With a black hole, you're talking quite a lot of mass, and it would be very difficult for a man-made device to move enough charge to create a field anywhere close to the magnitude of a black hole.
Plus, say you can create a strong enough magnetic field. What are you going to push/pull against? Some star out in the middle of nowhere? It probably doesn't have a strong enough magnetic field of its own? The black hole itself? Now you're getting into all kinds of other problems.
One final thing to note about your idea - gravity affects electromagnetic radiation, and hence it's affecting magnetic fields. Ever heard of gravitational lensing? Ever heard the statement that the event horizon is the point after which "even light can't excape"? It's not as simple as trying to create a bigger force, as the gravity of the black hole itself would be distorting the magnetic field you are trying to create.
fast as fast can be. you'll never catch me.
One thing that is wrong with black holes vis a vie quantum mechanics...
Such a silly mistake from a Real Scientist(tm). Vis-a-vis, perhaps?
Tiller's Rule: NEVER use a word that you've only heard and never read. You WILL look like a fool.
Tiller's Rule: Never use a word in written form that you've only heard and never read. You will end up looking foolish.
Could a physicist around here explain how these proposed dark energy stars could explain the expansion of the universe if they behave exactly like black holes outside the event horizon?
I am not a physicist, but I RT PDF paper. The guy isn't trying to explain the expansion of the universe, we already have several explanations for that using dark matter and energy. He is trying to integrate general relativity with quantum physics.
He uses the dark energy to get ride of the event horizon of the black holes. The existence of event horizons breaks QM. He is also not proposing a QM gravitational theory, just an alternative explanation for black holes.
Rethinking email
Einstein's work explaining the photoelectric effect formed a foundation of quantum electrodynamics, from which spawned quantum mechanics. He opposed Bohr's estimate of what quantum mechanics meant to science (that reality at the quantum level can be explained only by probabilities, not by strictly measured and predictable outcomes), but his belief was not that quantum mechanics was wrong. He instead believed that there was another set of rules underlying quantum mechanics that would allow for predictability at the quantum level.
Naked.
They created something that behaves like a black hole. If the theory about dark energy stars is right, it could have been a ball of dark energy instead.
IAAP (I am a physicist), and I'm annoyed that this is modded "Informative".
The RHIC collaboration at Brookhaven has fewer pion jets than their complicated Monte Carlo simulations say should exist. One possible (and highly attention-getting) explanation is analogous to a black hole, in the same way that "slow light" experiments can create something analogous to an event horizon. Neither experiment is actually creating a black hole , in the sense of a quantity of matter compressed to a region smaller than its Schwarzchild radius.
Regarding the original article, it's interesting speculation, but without any evidence to support it yet. For those interested in some of its underlying ideas (e.g. the vacuum as a superfluid), I strongly recommend Bob Laughlin's new popular book (readable by nonphysicists!) on the subject, A Different Universe: Reinventing Physics from the Bottom Down.
No. An object does not have to reach escape velocity to escape a planet's gravitational pull. Escape velocity is the speed with which a ballistic (unpowered) object has to be launched from the surface of the planet in order to escape its gravitational field. You calculate it by setting the initial kinetic energy (given by (mv^2)/2, a half the mass times the square of the veloicty) equal to the gravitational potential energy (given by GM/r^2, where G is the gravitational constant, M the mass of the planet, and r^2 the square of the radius of the planet).
That gives a figure for the escape velocity of
v = sqrt(2GM/m(r*r))
However, for a rocket (or other powered device) to escape a planet's gravitational pull, as the GP said, all it has to do is provide enough vertical thrust to provide a positive acceleration. That acceleration does not have to accelerate it to the escape velocity - in fact, you could adjust it to compensate for the falling gravitational pull and so maintain a constant velocity of whatever you want, and (if you have sufficient power/fuel) you'll still escape.
That doesn't work for a black hole because all of that is based on Newtonian mechanics, which do not apply in the large gravitational fields close to the event horizon. There, you must use General Relativity, which is counter to our everyday common sense view of the world (precisely because on our scales, it's irrelevant). I don't know enough about GR to demonstrate why this is, however.
It's official. Most of you are morons.
The solution is string theory. This website has a nice list of expirements that have been done in favor of string theory.
String theory may or may "be the solution". But let's not kid ourselves; there have been *no* experiments done that support string theory. The site linked is just playing "let's pretend".
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Four pages is all it should take to briefly introduce a new theory, which is what George is doing.
p.s. George Chapline is very a bright fella with a history of suggesting contrarian theories. At least one of those theories has led to a entire branch of nuclear physics.
They mention being cault up in a black hole in "Tomorrow is Yesterday". Its the first time they use the sling-shot time travel method.
Warping away from the black hole caused the Enterprise to pass beyond Warp 10, which evidently caused it to go back in time (though passing Warp 10 sometimes doesn't). They wind up on earth in the 1960's and have some dealings with the USAF.
I don't think it was the fist time they did the time warp, there was also an early episode where it occured because the had to "hard start" the warp drive.
Cool art gallery, if you're into that sort of thing.
You seem to be a very skeptical person, or perhaps you have not looked very far, In 1971, experiments were carried out using four caesium beam atomic clocks (The Hafele-Keating Experiment). Two of the atomic clocks were put on commercial jets and flown in opposite directions around the world. The predicted time dilation matched up to the difference in the atomic clocks.
I find it rather unlikely that this is a coincidence. What are the chances that two pairs of atomic clocks would fail, and fail by exactly the same amount as theory predicts. Pretty slim.
Of course, this was an experiment done on the macroscopic scale. In particle accelerators, time dilation directly affects the half-life of particles such a muons. Thousands of experiments have confirmed that the half-life of particles is affected by velocity in the exact way that Einstein predicted. Again, this is very hard to chalk down to coincidence.
Furthermore, experiments with the speed of light show that the speed of light is constant. Albert Michelson and Edward Morley tested the speed of light parallel to the Earth's velocity, and perpendicular to it; there was no difference in the results. From this we can conclude that either the experiment, and all the hundreds similar experiments performed after, were fundamentally flawed in precisely the same way (a stretch of the imagination). That the earth does not move around the sun. Or that the speed of light is independant of one's velocity. Indirectly, if these experiements are correct, this proves time dilation.
How? Consider a man on a spaceship travelling at high speeds. Upon the floor of his spaceship is a laser, a light sensor, both connected to a very accurate stopwatch. Upon the ceiling is a mirror. When the man presses a button, the laser beam is fired up at the mirror, and the stopwatch starts timing. The laser beam will bounce off the mirror, hit the light sensor, and the stopwatch will stop. Thus, the man will now know the time it takes for a laser beam to cover the distance between the laser beam, the mirror, and the light sensor.
With me so far? The problem comes when an observer upon the earth watches the spaceship zip past. To the man inside, the laser beam heads straight up and down, taking a purely vertical path. To the observer on earth, the spaceship moves horizontally whilst the experiment takes place, so to the observer, the laser-beam takes a longer, diagonal path. Because light is a constant speed, to the observer, the light beam travels at the same speed for both the observer and the man in the spacecraft. However, for the observer, the light beam travels a further distance than for the man in the spaceship, and therefore takes a longer time. So to the observer, the whole event takes a longer time than it does for the man inside the spaceship. That's time dilation.
And it has nothing to do with the type of clock. We've measured clocks in zero-G moving and not moving, or, at least, moving much slower. They're different. What's more, they're different in a way that's identical to what was predicted 90 years ago. The whole 'Yes, but it might be weird clocks' worked when it was one experiment. We've got thousands for satellites in orbit, and all of them demonstrate time dilation, at least all the ones that are accurate enough to measure it and can be allowed to let their clocks get out of sync.
And unless you have a better theory of why Mercury is rotating with 43 extra acrsecs a century, perhaps you better be quiet. For those of you who don't know, Mercury is suffering spacetime distortion from the sun. It's got slightly less time and slightly more space than we do, and thus our measurements of it are 'wrong'. If we measured it from Mercury it would be right and all the other planets would be in weird orbits.
I don't know where people get crazy ideas that all of physics is some absurd pie-in-the-sky shit. This isn't philosophy....if a scientific theory isn't disprovable, it's not a fucking scientific theory. Relativity is disprovable, and repeated experiments have demonstrated that it works reasonable well.
If corporations are people, aren't stockholders guilty of slavery?
Actually "Tomorrow is Yesterday" mentions a "black star" not a "black hole". "Tommorow is Yeserday" was first aired in Jan 1967 and AFAIK produced in 1966. As previously mentioned, John Wheeler coined "black hole" in late 1967. So it predates the existance of the term "black hole" by a small but important amount.
The idea of a black hole existed in the 1960s. IIRC the German astronomer Karl Schwarzschild developed the concept of the black hole durring World War I. There were other names for it, and AFAIK none of those names was "black star".
Names that I am aware of include:
Dark Star
Frozen Star (Soviet Union)
Spherical Singularity (Schwarzschilds name)
Collapsed Star
The concept of the black hole came from a german physicist, Karl Schwarzschild, while stationed in the russian front during World War I. What he did was take the physics of Einstein's gravitational theory to a logical (although quite abstract) conclusion.
In 1929, the hindu astrophysicist Subramanyan Chandrasekar figured out the amount of mass that dooms a star to eventually collapse into a black hole; known as the Chandrasekar limit, it is 1.4 times the mass of our sun.
The first detected candidate for black hole status (in the early seventies, I believe) is a massive x-ray source named Cygnus X-1, and coincides with the known position of a binary star system in the constellation (surprise) Cygnus.
However, as to the origin of the term "black hole", I do not know.
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