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Short Gamma-ray Bursts Traced to Colliding Stars

Astervitude writes "Collisions of the cosmic kind could be the source of one of nature's most lethal explosions. Astronomers have traced the origin of short-duration gamma-ray bursts, or GRBs, to the merger of neutron stars or other dense bodies. Space.com has a report on the scientific detective work that led to the solution of what has been described as a 35-year-old mystery. "Our observations do not prove the coalescence model, but we surely have found a lady with a smoking gun next to a dead body," said Shri Kulkarni, one of over two dozen astronomers who discovered and investigated two short-duration bursts that took place last May and July. Unlike short-duration GRBs, long-duration GRBs are believed to be produced when extremely massive stars collapse and explode as supernovas."

135 comments

  1. The Science Channel by Namronorman · · Score: 4, Interesting

    The Science Channel has recently (by coincidence?) been showing a lot of programs talking about stars and the sun, and a very common topic has been Gamma Ray Bursts.

    I just think it's weird how some things seem like a trend some times.

    The idea of neutron stars colliding is a very old theory but this seems to shed new light on the possibility of it being the main cause.

    --
    $fortune
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    1. Re:The Science Channel by Zindagi · · Score: 2, Interesting

      One of the reasons that comes to mind is the launch of a new satellite for observing GRBs SWIFT. And the fact that GRB's are intrinsically intriguing - being the huge balls of energy (if you will) in the Universe

      --
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    2. Re:The Science Channel by Anonymous Coward · · Score: 0

      I've noticed this happen a lot too, but IMHO, it is purely coincidence - during your life there is so much opportunity for coincidence like this, so even with a tiny probability of it just randomly happening, it's bound to occur given enough time.

  2. article is slightly misleading... by eobanb · · Score: 0

    It should be noted that ordinary fusion reaction stars (giants, main sequence stars, and dwarfs) don't collide, because they're massive enough not to change direction easily from their usual trajectories (away from each other, as the universe expands), but not massive enough to actually have the gravitational force to be drawn towards other stars. I can only suppose that neutron stars have sufficient mass to bring about such a collision.

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    1. Re:article is slightly misleading... by eobanb · · Score: 2, Informative

      Let me add on to this and also mention that when two stars do get close to each other they tend to fall into orbit around each other instead of just colliding, obviously. In that case, you have another star in close enough proximity to keep the star in an acceleration curve.

      --

      Take off every sig. For great justice.

    2. Re:article is slightly misleading... by Capt'n+Hector · · Score: 4, Informative

      Um... ok. 1) Mass has nothing to do with a star's ability to collide. 2) the universe's expansion only effects entire galaxies over extremely long distances. Individual stars in galaxies are not affected by this. In fact, they are drawn towards each other as seen in binary+ systems. This is where colliding neutron stars comes from. We need a binary system where both stars are of sufficient size to go supernova and create two neutron stars. Now we have two neutron stars orbiting each other. While the following can be derived directly from Einstein's equations in a single college lecture, it's rather too complex to detail in a slashdot comment... essentially these two neutron stars spiral inward towards each other because with each orbit they loose enough orbital energy due to gravitational waves (energy given off by a gravitational wave is inversely proportional to orbital period and proportional to mass - or something like that) It turns out this energy is of an appreciable amount so that eventially these stars will collide in a reasonable amount of time. So yeah.

      --
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      Africus aut Europaeus?
    3. Re:article is slightly misleading... by Anonymous Coward · · Score: 0

      Is that where flux capacitors are born, when two "ordinary fusion reaction stars" collide? GREAT SCOTT!!!

    4. Re:article is slightly misleading... by Lucractius · · Score: 1

      let me just add that massive bodies of all kinds are attacted towards eachother. so your point about them drifting apart is rather misleading. the expantion of the universe on a interstellar scale is not significant compared to the gravitational bonds of the galactic core that the stars orbit.

      It is quite reasonable that stars can colide on their orbits around the galactic core. takes about 200 million years for the solar system to orbit the galactic core. 2 stars could have intersecting orbits and consequently collide at some point.

      thats just the explanation for big ones. stars regularly form binary pairs, so all of this collision stuff is fairly regular orbital mechanics. Orbits decay. End of the argument.

      --
      XML - A clever joke would be here if /. didn't mangle tag brackets.
    5. Re:article is slightly misleading... by WalterGR · · Score: 3, Funny

      ...it's rather too complex to detail in a slashdot comment.

      Dude - never talk about the space in which you would write an explanation. That's like the ultimate jinx. The last time a guy did that, it took the rest of the world 357 years to figure it out.

      ;)

    6. Re:article is slightly misleading... by jafiwam · · Score: 1

      Not gravitational waves that I know of, though they could pull energy from the system.

      Tidal forces.

      The tidal forces of the things moving around in orbit sucks energy out of the orbits (specifically, the inertia and friction overcome when the star changes shape is removed from the orbital energy).

      Eventually over a long time, objects fall inwards due to this effect. (Earth is doing it too, as the Moon will eventually crash into the Earth... both if nothing else happens first. The energy gets dissapated as heat.)

      It's counter intuitive, but the equations work out that way and there is observational evidence to support the theory.

    7. Re:article is slightly misleading... by shawb · · Score: 1

      1) Tidal forces will slow down rotation, but that is on the axis of spin, not the rotation of orbit. Eventually orbiting bodies come into lock step such that one face is always facing the other (much like how we always see the same side of the moon.)

      2) The moon is moving FURTHER away from Earth, not closer.

      If I'm not mistaken, tidal forces would INCREASE the distance between two rotating bodies, as the momentum or axis rotation is transfered to orbital momentum. The decay of orbit here happens due to gravitational waves caused by the massive density of the neutron stars.

      --
      I'll never make that mistake again, reading the experts' opinions. - Feynman
    8. Re:article is slightly misleading... by Anonymous Coward · · Score: 0

      with each orbit they loose enough orbital energy

      "lose".

  3. They explode, hence blackholes are a impossibility by LogicallyGenius · · Score: 0

    Before becoming a blackhole any star will explode explode due to fusion of heavy atoms, the heavier they are more energy they will release. like the heavy metals

  4. Correction... by Adi42 · · Score: 2, Interesting

    It's actually about colliding neutron stars...

    Anyway, it is curious that no gamma-ray bursts occured in our galaxy (yet). It is supposed that such an even would generate enough gamma rays to wipe out the ozone layer, and cause life extinction on earth.

    Wait... why dinosaurs dissapeared again? :-)

    1. Re:Correction... by Maxhrk · · Score: 0

      other theory: dinosaurs extinction due to supernova or something big

    2. Re:Correction... by fido_dogstoyevsky · · Score: 2, Funny

      Anyway, it is curious that no gamma-ray bursts occured in our galaxy (yet). It is supposed that such an even would generate enough gamma rays to wipe out the ozone layer, and cause life extinction on earth.

      Wait... why dinosaurs dissapeared again? :-)


      I thought it was because they took up smoking...

      --
      It's NOT a conspiracy... it's a plot.
    3. Re:Correction... by ThinkOfaNumber · · Score: 1

      > > Wait... why dinosaurs dissapeared again? :-)
      > I thought it was because they took up smoking...

      No, no! It's because Homer sneezed when his modifed toaster took him back in time, remember?

    4. Re:Correction... by layer3switch · · Score: 1

      Correct me if I'm wrong, but didn't dinosaurs extinct over a period of time, long enough to evolve and adapt to changing environment?

      And not only that, extinction in mass scale doesn't seem to "sanitize", but "life" seems to find its way out of harsh environment or adapt. Matter of fact, didn't theropod dinosaur survive? After all, what are all these birds doing on earth?

      --
      "Don't let fools fool you. They are the clever ones."
    5. Re:Correction... by Decaff · · Score: 1

      Correct me if I'm wrong, but didn't dinosaurs extinct over a period of time, long enough to evolve and adapt to changing environment?

      No. Many species of dinosaur became extinct of a period, but at a slow rate. The latest evidence is that the final extinction which wiped out the rest was very fast indeed.

      And not only that, extinction in mass scale doesn't seem to "sanitize", but "life" seems to find its way out of harsh environment or adapt. Matter of fact, didn't theropod dinosaur survive? After all, what are all these birds doing on earth?

      The exact relationship between birds and dinosaurs is controversial. What did seem to happen is that some extinction event (most likely an asteroid collision) wiped out most large species. Things that could burrow or hide from the heat survived, which would have included birds.

    6. Re:Correction... by Decaff · · Score: 2, Informative

      Anyway, it is curious that no gamma-ray bursts occured in our galaxy (yet).

      They may have, but not pointed in our direction.

      It is supposed that such an even would generate enough gamma rays to wipe out the ozone layer, and cause life extinction on earth.

      Wiping out the ozone layer would not cause extinction of life, after all, life survived for billions of years without such a layer.

    7. Re:Correction... by Ihlosi · · Score: 1
      It is supposed that such an even would generate enough gamma rays to wipe out the ozone layer, and cause life extinction on earth.



      If the burst occurs close enough (a few lighyears, maybe even a few tens of lightyears should do), it would essentially sterilize the side of the planet that is facing towards the source of the burst.



      Death Stars are for tourists.

    8. Re:Correction... by tabbser · · Score: 1

      Did you read the article at all ?

      This gamma ray burst was from within our galaxy !

      A GRB of this size within 10 light years would be enough to disrupt (read species die out) on earth.
      The nearest worrying sources, magnetars, around 4000-5000 light years away.

      Please, please, please, do a little google searching before opening your mouth.

    9. Re:Correction... by stevelinton · · Score: 1

      No. The two GRB's they are interested in were about 1 billion light years away -- well outside our galaxy, but closer than the regaular long-duration GRBs which are several billion lys away.

      You may be confusing this with the recent outburst from (probably) a magnetar on the other side of the galaxy, which is a Soft Gamma Repeater (SGR), a different thing again.

    10. Re:Correction... by jellomizer · · Score: 1

      So with a Gamma-ray burst it caused all the Mammals into huge green invincible creatures that killed all the dinosaurs when they got angry.... Cool.

      TRex to Big mouse thinggy. I am going to eat you.
      Mouse: I am getting angrrrrrrryyy. Rarrrr! Mouse Smash!!
      THen the mouse beats up the TRex

      --
      If something is so important that you feel the need to post it on the internet... It probably isn't that important.
    11. Re:Correction... by oojah · · Score: 1

      http://geophysics.ou.edu/impacts/dinos.gif

      I'm sure that's what you were referring to. Good stuff.

      --
      Do you have any better hostages?
    12. Re:Correction... by mark_osmd · · Score: 1

      the article specifically says: "Astronomers now know the event took place on the outskirts of a faraway galaxy, a location where old stellar remnants like neutron stars are known to reside." 'Faraway galaxy' doesn't sound like it was our galaxy

    13. Re:Correction... by CaptainFork · · Score: 1

      Dinosours are huge invincible green monsters. The monster mammals must have been brown or purple or something

    14. Re:Correction... by mfrank · · Score: 1

      I've read somewhere that if one happened less that 6000 light years away, we're screwed. The half of the planet within line of sight of the event would be sterilized and the ozone on that half would disappear. Over the next few days the ozone left would disperse evenly, so whoever lived would have half the ozone layer. Crop loss, skin cancer, environmental devastation and other hilarity would ensue.

    15. Re:Correction... by dragons_flight · · Score: 1

      Anyway, it is curious that no gamma-ray bursts occured in our galaxy (yet). It is supposed that such an even would generate enough gamma rays to wipe out the ozone layer, and cause life extinction on earth.

      Where were you last December? The most luminous gamma ray event in the history of measurement occurred based on a gamma ray burst on the other side of our own galaxy. That particular event was cause by starquake and crustal reorganization of a magnetar, a rare type of event expected to explain a small precentage of short-duration gamma ray bursts.

      To have an important effect on Earth a GRB would need to be within a few tens to a few hundred lightyears (depending on absolute luminosity). Astronomers estimate such close GRBs should occur a few times per billion years. Important in the history of life, but not a large concern on the time scale of human civilization.

    16. Re:Correction... by dragons_flight · · Score: 1

      Oops, the most powerful sort of GRBs can actually be dangerous out to several thousand light years. Mea culpa.

  5. Re:They explode, hence blackholes are a impossibil by barneyfoo · · Score: 0

    The proof offered for the existence of blackholes doesn't convince me. Just because there is a solution to the GR equations doesn't make it physically real.

    Unfortunately these ideas are so institutionalized that there won't be much respect paid to challengers.

  6. Gravity Waves by williwilli · · Score: 4, Informative

    The end part of the article notes that the upcoming LIGO observatory might see the first detection of gravitational waves, corresponding with a GRB event! Evidentially Einstein modeled the emission of gravity waves during a collision between Neutron stars. This is interesting because we don't really know much about gravity; e.g. if it is a wave or a constant. More info on LIGO is available here.

    free music, games, recipes, and more!

    1. Re:Gravity Waves by Decaff · · Score: 2, Informative

      This is interesting because we don't really know much about gravity; e.g. if it is a wave or a constant.

      We are pretty sure it is a wave because we have seen the effects of gravitational radiation (of waves) in double neutron star orbits. If gravity isn't waves, then general relativity is in trouble, which is unlikely.

    2. Re:Gravity Waves by PhilRod · · Score: 3, Informative

      The paper itself suggests that observing the waves from such an event would have to wait until the "second generation" LIGOs. I assume by that it means advanced LIGO, which isn't scheduled to start taking measurements until 2013, so don't hold your breath :-). Even so, LIGO is an amazing project - the sensitivities required are enormous, (to quote the LIGO website: "These changes are minute: just 10-16 centimeters, or one-hundred-millionth the diameter of a hydrogen atom over the 4 kilometer length of the arm"), and the payoffs for theory and astronomy are potentially huge.

      As to whether gravity is a wave, that's generally agreed (as someone else pointed out, measurements of binary pulsars show this). However, the exact details of general relativity in the strong field regime - that is, near black holes, neutron stars, etc - hasn't been well tested, and there are potentially modifications of general relativity which would give the same predictions for the weak field case (eg, the solar system), but would differ for strong fields. Physics World has a nice article on it.

      --
      KDE Documentation Team: http://i18n.kde.org/doc
    3. Re:Gravity Waves by drauh · · Score: 1

      LIGO is not just "upcoming". It's already running, though not 24x7x365, and taking data. You can see some of the early papers at the preprint archive: search for "LIGO" in the author field.

      --
      This is a tautology.
  7. You're right, they're massive enough. by Spy+der+Mann · · Score: 3, Interesting

    I can only suppose that neutron stars have sufficient mass to bring about such a collision.

    Actually, that's an understatement.

    According to the wikipedia, a neutron star is about 1.5 times massive as the sun... and that would be about 1.5 × 2x10^30 kg = 3x10^30kg, but ONLY 12 miles in diameter. One can just imagine the gravitational force these things have.

    I'd appreciate it if someone made calculation: If two neutron stars are say, 10,000 km far from each other, what will be the acceleration? (remember, the greater the mass, the greater the acceleration). And what speed will they have when they collide? Finally, what will be the kinetic force at the time of impact?

    1. Re:You're right, they're massive enough. by pomo+monster · · Score: 1

      "...a neutron star is about 1.5 times massive as the sun ... but ONLY 12 miles in diameter. One can just imagine the gravitational force these things have."

      Sure, so about 1.5 times the gravitational force of the sun? ;-)

    2. Re:You're right, they're massive enough. by njchick · · Score: 1

      At the distance equal the solar raduis. Much higher on the surface.

    3. Re:You're right, they're massive enough. by layer3switch · · Score: 1

      Matter of fact, neutron star's gravitational force according to Thacker Nuclear Binding Theory of Gravity, once the nuclei are bound very tightly together, become very weak. So it wouldn't be 1.5 times of the Sun even though mass is about equal.

      --
      "Don't let fools fool you. They are the clever ones."
    4. Re:You're right, they're massive enough. by Anonymous Coward · · Score: 1

      I'm sure he means surface gravity. A neutron star has a surface gravity of about 10^11 times greater than Earth's. It also has a magnetic field strong enough to disrupt atomic nuclei. source

    5. Re:You're right, they're massive enough. by theorl21 · · Score: 1

      Its gravitational force would be much greater than our sun's. If so much mass is compressed in a 12 mile in diameter area, then imagine how much a simple teaspoon of matter would end up weighing in this star. The way I understand it, the more tightly compact mass is, the greater its gravitational effect within an ever decreasing sorrounding area.

    6. Re:You're right, they're massive enough. by The+Master+Control+P · · Score: 3, Informative
      If two neutron stars are say, 10,000 km far from each other, what will be the acceleration? (remember, the greater the mass, the greater the acceleration).
      Well, the gravitational acceleration from a point mass at a given distance is MG/R^2 (force computed by plugging a second mass in on top). 3 * 10^30 * 6.67 * 10^-11 / (10000000)^2 = 2001000 M/S^2 (I love Google Calculator), or roughly 200000G's that each star applies to the other. Total acceleration: 4002000 M/S^2.
      And what speed will they have when they collide?
      This is kinda tricky, because they don't just start from rest and fly into eachother (which would no doubt be awesome to watch from a distance). But imagine that two neutron stars just pop up 10000km from each other. Each has a gravitational potential relative to the other: mass * integral g(h) dh from 10k to 10m, where g(h) is gravity at height h (2*10^20 / h^2), or the energy to raise one star's mass from the surface of the other to 10 thousand KM. I get 5 * 10^46 joules each. As they fall, potential turns to kinetic energy: 5 * 10 ^ 46 = .5MV^2 = .5 * (3 * 10^30)V^2. V works out to 182 574 186 meters per second. This is a relativistic speed, so things get wierd and I give up. This never happens though - they spiral around each other, losing orbital speed to gravitational waves until their mutual orbit decays into impact.
      Finally, what will be the kinetic force at the time of impact?
      I don't think our knowledge of motion even applies to something this massive moving this fast, aka I don't have a clue.
    7. Re:You're right, they're massive enough. by m50d · · Score: 1
      Its gravitational force would be much greater than our sun's. If so much mass is compressed in a 12 mile in diameter area, then imagine how much a simple teaspoon of matter would end up weighing in this star. The way I understand it, the more tightly compact mass is, the greater its gravitational effect within an ever decreasing sorrounding area.

      The same amount of mass will always produce the same amount of force no matter how compressed. The difference is that you're much closer to the center on the surface, and since gravity follows an inverse-square law the force will be a helluva lot more on the surface of such a dense object than that of a huge ball with the same mass. But the force (say) 10000km from the centre will be the same.

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    8. Re:You're right, they're massive enough. by SimilarityEngine · · Score: 1

      Diameter of sun is approx 1,400,000 km. So the gravitational field strength at 10,000 km from the centre of the sun will be considerably less than that 10,000 km from the centre of a neutron star. Also it'd be a bit warm - T-shirt and shorts weather, I think.

      ;-)

      --
      Those who can make you believe absurdities can make you commit atrocities. - Voltaire
    9. Re:You're right, they're massive enough. by Ihlosi · · Score: 1
      Also it'd be a bit warm - T-shirt and shorts weather, I think.



      Don't forget the sunscreen, either. Preferably with a LPF that ends with "e[really large number]"

    10. Re:You're right, they're massive enough. by Anonymous Coward · · Score: 0

      The neutron stars will spiral in towards each other, so before impact they will be orbiting each other with a seperation of the two radii (actually tidal forces will have torn them into a torus about the common centre by then).

      Orbital speed at that seperation will be a significant proportion of the speed of light (square root of escape velocity of the neutron star, which may approach the speed of light).

      Therefore kinetic energy is a significant fraction of the total rest mass of the two stars, i.e. the energy released will be getting on for as much as colliding a star with another one made of anti-matter. That's a big bang!

    11. Re:You're right, they're massive enough. by Anonymous Coward · · Score: 0
      square root of escape velocity

      That should have been escape velocity / root 2 of course!

    12. Re:You're right, they're massive enough. by Phanatic1a · · Score: 1

      Talk about needlessly complicating issues. Integrals? Yeesh.

      Graviational potential energy between two bodies is -G*(m1m2)/r, so that's 6.673E-11 * (3E30*3E30)/10000km, for just about 6E43 joules, so you're a few orders off. Head-on collision between two bodies of equal mass means each contributes half of that energy,
      so each one's contributing 3E43 joules. 3E30kg body would have to be moving at 4472135 m/s to do that. That's 1.49% of c, so it's not strongly relativistic, with a gamma of 1.00011113.

    13. Re:You're right, they're massive enough. by The+Master+Control+P · · Score: 1

      -G*(m1m2)/r IS the integral of m1m2G/r^2, except I was thinking that it was integrated from h1 to h2 (10km at the surface to 10000km distance) rather than from h2 to infinity

    14. Re:You're right, they're massive enough. by Decaff · · Score: 1

      Matter of fact, neutron star's gravitational force according to Thacker Nuclear Binding Theory of Gravity, once the nuclei are bound very tightly together, become very weak. So it wouldn't be 1.5 times of the Sun even though mass is about equal.

      This theory is utter nonsense. If the gravity was weak, the nucleii would not be bound together!

      Proof that this theory is nonsense is that very precise observations of the orbits of binary pulsars have confirmed Einstein's theory of gravity.

    15. Re:You're right, they're massive enough. by bwgref · · Score: 1

      And by 'binary pulsars' you really mean 'the only binary pulsar system that we've every seen'. While there are plenty (read: dozens) of examples of pulsars in binary systems that have a main sequence or giant star as a companion, there's just the one known example of a binary pulsar system (i.e. two pulsars orbiting each other). And yes, it's one of the best tests for the relatavistic corrections gravity that's every been measured (and the reason that Gravity Probe B got pushed back, again). Oh, and as to the gravity problem...even exotic objects like a one solar mass black whole with feel like a one solar mass star (i.e. the sun) from the outside of the object (go do a Wikipedia for "Guass' Law"). The composition, shape, density, color, sexuality, of the object has nothing to do with the gravitational potential.

  8. Re:As Einstein once said... by Urusai · · Score: 0, Flamebait

    Then imagine a cogent response next time.

  9. Re:They explode, hence blackholes are a impossibil by Anonymous Coward · · Score: 0

    Got a better explanation for the evidence?

  10. Don't they have to be damn close? by Quadraginta · · Score: 1

    I'd think the loss from gravitational waves would be miniscule unless they were very close to each other. Which, granted, NS can do, being small and dense and all -- but how do they get that close to begin with?? Are we thinking some hideously close binary where the two stars start out mere dozens of AU apart? Inquiring minds want to know...

    1. Re:Don't they have to be damn close? by Hays · · Score: 1

      I'm no expert, but one can imagine how it is possible for them to end up as two neutron stars relativly close to each other such that gravitational drag can pull them together within the lifespan of the universe-

      First, they don't go supernova at the same time. One becomes a neutron star, and then the other. When the relationship is asymmetrical, one neutron one star, I think they have more interaction with each other. No shockwave keeping most of their materials apart. Instead material will be spiraling onto the neutron star from the other one, and that probably has the effect of imparting drag and bringing them together. Also I don't think the supernovae necessarily impart their forces symmetrically. They might have the effect of countering a lot of the momentum of one of the stars (or rather ejected material goes one direction, neutron core goes the other)

      This is somewhat conjecture. But your point is a good one, I think. Surely their is some minimum distance at which large, supernova proned binary stars can form. And surely gravitational drag is a very slow phenomena.

    2. Re:Don't they have to be damn close? by eobanb · · Score: 1

      I don't see how gravitational drag could really have anything to do with it. The way I could concieve two neutron stars coming together would be stars A and B travelling on roughly parallel paths through the galaxy, and gravity pulls them together. Simple as that. If stars are orbiting each other, it's totally different. If you have two ball bearings on a frictionless plane that curves up on two sides, with the lowest area being a line down the centre, the bearings are going to accelerate to that low point. On the other hand, if you have some sort of plane with a single point that's the lowest (instead of a line), then the balls are just going to revolve around this point forever. The only way they wouldn't is if they had absolutely zero velocity to start with. Then they would just be pulled into the point, and that would be that. But neutron stars tend to have some sort of momentum, and they're not so likely to just happen to be heading straight into one another. Ultimately it just seems really unlikely and bizarre, but I guess it's theoretically possible, just more probable than ordinary stars colliding. It's like having a bunch of magnets floating about in a zero-G room versus ordinary objects.

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    3. Re:Don't they have to be damn close? by The+Master+Control+P · · Score: 2, Informative

      Neutron stars and other things like them do wierd things: Objects that dense and massive, spiraling around each other that fast, create gravitational waves like moving a stick through a pond. Energy is needed to create gravity waves, and it comes from the orbital motion of the neutron stars. Their existing orbits slow down; They fall closer and orbit even faster, generating more gravity waves than before.

    4. Re:Don't they have to be damn close? by Anonymous Coward · · Score: 0
      ejected material goes one direction, neutron core goes the other
      When a bomb goes off, the material inside the bomb does not move in one direction and the explosion in another. The bomb, like a star going supernova, explodes more or less evenly outwards; if it did not, and if the core did move, it would likely never collapse to a neutron star--an object in motion will remain in motion, and as the core moves away from the cloud it loses mass and thus gravitational attraction.
  11. Re:They explode, hence blackholes are a impossibil by Yahweh+Doesn't+Exist · · Score: 2, Insightful

    >The proof offered for the existence of blackholes doesn't convince me. Just because there is a solution to the GR equations doesn't make it physically real.

    people don't believe they exist just because of a GR solution.

    they were predicted before GR but believed to be a mathematical trick that would need perfect conditions to form (perfectly symmetrical mass distribution). GR just changed that by removing these conditions (the generation of gravitational waves by mass distributions with a quadrupolar moment means).

    anyway, you make it sound like it's just a case of GR for black holes. it's not - it's a huge amount of theory and observations that are all consistent. if you want respect then the first thing to do is acknowledge this work exists, and the second is to provide an alternative explanation that works at least as well.

  12. The animation NASA had was cool... by ockegheim · · Score: 1

    Would the explosion at the end have be when the majority of the neutron star mass hits the black hole's event horizon?

    --
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    1. Re:The animation NASA had was cool... by Anonymous Coward · · Score: 1, Informative

      No. In fact, nothing would be seen: the horizon is not a physical surface that a star can "smack into", but a region of space within which light can't escape. In fact, that is one of the main new ways we have found to justify the existence of black holes: when things run into them and you don't see a big flash from a collision.

  13. Get rich quick by Mathinker · · Score: 3, Funny

    The merger of two dense bodies causes gamma-ray bursts?

    Wow! Now I can get rich selling lead underwear the next time there's a Microsoft/AOL merger hoax

  14. Re:They explode, hence blackholes are a impossibil by norton_I · · Score: 2, Interesting

    There is a lot of experimental evidence for black holes, evidence not well explained by any other known theory. Even after black holes were found to be a possible solution to the GR field equations, people were hesitant to accept them as a "physical" solution. It was only a large body of evidence that has convinced us that they exist.

    Despite what you may believe, physicists will listen to challenges to almost any theory (and are proven wrong on a regular basis, science advances!). However, if you just say something can't happen because it is patently silly, without providing a compelling alternative explanation of loads of experemental results, you will be dismissed out of hand. Also, the longer and more successfully a theory has been used, the more substantial evidence against it you will need. Black holes have only been accepted for a short period of time, but if you challenge conservation of energy be prepared. Extraodinary claims require extraodinary evidence.

    Also, frequently an outsider to a field will have an alternate theory rejected immediately not because it is absurd but because the experts have already thought of it, done the calculations, and shown that that explanation is inadequate.

    Of course, scientists make mistakes, too, but not usually for long in the face of strong evidence.

  15. Re:They explode, hence blackholes are a impossibil by The+Master+Control+P · · Score: 4, Informative

    What are you talking about? Fusion only produces energy in elements lighter than Iron, and fission only produces energy in elements heavier than Iron. Iron is the most tightly-bound nucleus (most eV / nucleon) - If you fuse it with another nucleus, the nuclear binding energy of the result will be higher than what you started with, and you lost energy. Furthermore, the energy yield from fusion is highest with hydrogen & helim and decreases rapidly as masses increase.

    If you'd like to learn more, type "nuclear binding energy" into Google.

  16. Re:They explode, hence blackholes are a impossibil by Anonymous Coward · · Score: 0

    Looks like someone hasn't done his research.

    Fusing elements heavier than iron require more energy than they release. Didn't you wonder why we've been trying to fuse light elements like hydrogen and helium, and not plutonium?

  17. Science Meets Film Noir by MooseByte · · Score: 4, Funny

    "Our observations do not prove the coalescence model, but we surely have found a lady with a smoking gun next to a dead body," said Shri Kulkarni

    Looks like the Sin City DVD has been getting a lot of play time down in the lab....

    1. Re:Science Meets Film Noir by just_another_sean · · Score: 0

      Yeah, what I want to know is why it has to be women with a smoking gun? I mean, if a man is caught with a smoking gun over a body he's "taking control of the situation", but if it's a women everyone immediately suspects the worst. Sheesh, when are we gonna get some equality people?

      --
      Creationist Textbook Stickers Declared Unconstitutional by CowboyNeal
    2. Re:Science Meets Film Noir by redheaded_stepchild · · Score: 1

      You want equality? Put the seat down your damn self!

      --
      Don't use the Troll mod just because you disagree with me.
  18. you don't say... by paran0rmal · · Score: 1

    Collisions of the cosmic kind could be the source of one of nature's most lethal explosions

    Amazing! And here I thought collisions of the microscopic kind caused the most lethal explosions...

  19. A few questions about GRBs by MAdMaxOr · · Score: 2, Interesting

    What is the typical frequency? (i.e. 1x per galaxy per 100k years)
    What is a typical duration?
    How close would you have to be to one to receive a lethal radiation dose?

    1. Re:A few questions about GRBs by tabbser · · Score: 2

      a) Not many, SWIFT detects between 30 and 300 a year, only a handful a year from our galaxy (I think)
      b) From less than a second, to a few seconds. VERY brief.
      c) A decent magentar flare or decent neutron merger within 10 light years would be enough to disrupt life (read species would die out)

      The nearest magnetars are 4000-5000 light years away.

      It does beg the question thoughL Which poor people got burned on this burst ?

    2. Re:A few questions about GRBs by imsabbel · · Score: 2, Insightful

      If there were "a few per year" from our galaxy, live would have never evolved on earth... (just think about it: a few per year over the the time earth exists is about 10 billion GRBs ....

      I dont know if we _EVER_ have observed a GRB in our galaxy, the detected ones are very isotropically distributed over the sky and in the _deep_ background. Most have a z>0.1 and are FAR away.

      And the killing ratio for a GRB would be more like 100-250 ly. 10 ly away even a normal supernova would be an extinction event.

      Just use some fermi logic:
      If a GRB is the result of the collision of 2 neutron start, than they are at least twice as rare as supernovas (somewhere those NS have to come from, plus many supernovas dont leave a neutron star).
      and after that, there has to be a situation when 2 are able to merge (which 99.9% only happens in close binary start, as 2 neutron start hitting each other has a laughably small propability).

      This alone allows to fix the rate of GRBs to at least as rare as once per millenium.

      --
      HI O WISE PRINCE. WHT TOOK U SO DAM LONG?
    3. Re:A few questions about GRBs by hde226868 · · Score: 3, Informative

      I do research in X-ray and Gamma-Ray astronomy and just wanted to confirm that so far no gamma-ray bursts have ever been observed to come from our own galaxy.

    4. Re:A few questions about GRBs by bhaak1 · · Score: 1

      And the killing ratio for a GRB would be more like 100-250 ly. 10 ly away even a normal supernova would be an extinction event.

      In this article, a GRB 6'000 ly away is assumed to have a devastating effect on Earth's lifeforms: Galactic Explosions Inhibit Life

      GRBs might also be the cause for the Non-Existence of a galactic Civilisation: An Astrophysical Explanation for the Great Silence.

    5. Re:A few questions about GRBs by dragons_flight · · Score: 1

      I do research in X-ray and Gamma-Ray astronomy and just wanted to confirm that so far no gamma-ray bursts have ever been observed to come from our own galaxy.

      Forgive me, but have you been living under a rock the last year? SGR 1806-20 gave rise to a gamma ray burst last December which was the most lumninous event recieved at Earth in the history of gamma ray astronomy, and it was only 50,000 light years away at the other side of our galaxy.

      I'll admit, magnetar star quakes aren't as sexy as high end supernova or compact object mergers, but they are expected to be responsible for some significant precentage of short duration GRBs.

    6. Re:A few questions about GRBs by hde226868 · · Score: 1
      Well, I have for sure not been living under a rock and am well aware of soft gamma-ray repeaters!

      The outburst you refer to (and the earlier ones, seen, e.g., by the Rossi X-ray Timing Explorer), however, was immediately recognized as a SGR outburst, and not as a "short gamma-ray burst". As you correctly say, there is currently a lot of debate in the community whether a fraction of short gamma-ray bursts are in fact due to SGR outbursts in nearby galaxies, however, how large that percentage is is not clear. One of the most careful studies of short gamma-ray bursts available has recently set an upper limit of 4 per cent of all short gamma-ray bursts as being caused by SGR outbursts (Lazzati et al., MNRAS 362, L8, preprint available at http://arxiv.org/abs/astro-ph/?0504308). I think we could argue whether this is a "significant percentage". To be fair, in the original Nature paper on the December outburst, Hurley et al. argue that SGR outbursts could explain a much larger fraction of short gamma-ray bursts.

      Overall, however, the debate in the community is still ongoing and therefore I think that at the moment the jury is still out and would still distinguish between SGR flares and short gamma-ray bursts. It is because of this that I stated that I am not aware of any GRB, short or long, that was ever seen from in object in our Galaxy.

      (and, yes, I indeed find anomalous X-ray pulsars (which might be magnetars) and other neutron stars with high magnetic fields very exciting objects and have published on them...)

  20. Re:They explode, hence blackholes are a impossibil by barath_s · · Score: 2, Informative
    It's not just because there is a solution ... there are cases where the observations are such that no other solution per the proven theory seems plausible

    http://www.wonderquest.com/black-holes-proof.htm
    Summarizes very neatly the default hypothesis that they exist

    This leaves aside the problem of coming up with a better theory than GR (which has been extensively tested)

    After all, the theory of black holes has been contested vigorously from its inception http://en.wikipedia.org/wiki/Chandrasekhar_limit
    http://www.newscientist.com/article.ns?id=dn6193

    Two examples of a reasonable approximation to proof:
    Massive black holes ... Here they seem to have shown that MACHOs and WIMPs do not fit the bill.
    http://www.space.com/scienceastronomy/blackhole_mi lkyway_021016.html

    And for a stellar mass black hole
    http://www.space.com/scienceastronomy/astronomy/de ath_spiral_010111.html

  21. Re:They explode, hence blackholes are a impossibil by Decaff · · Score: 2, Informative

    Before becoming a blackhole any star will explode explode due to fusion of heavy atoms, the heavier they are more energy they will release. like the heavy metals

    This is false. Fusion of atoms only releases energy if the atoms are light. Above a certain nuclear size (greater than Iron) fusion takes energy.

  22. The summary by barath_s · · Score: 2, Interesting
    I liked the FAQ :
    http://www.astro.caltech.edu/~ejb/faq.html

    especially the portion that said ...." In practice, over the few seconds that a gamma ray burst occurs, it releases almost the same amount of energy as the entire Universe! " The article posted on Slashdot is on the short and hard type

    1. Re:The summary by Decaff · · Score: 3, Insightful

      especially the portion that said ...." In practice, over the few seconds that a gamma ray burst occurs, it releases almost the same amount of energy as the entire Universe! "

      Which is, of course, nonsense. It should say 'the same amount of energy as the visible Universe'. Big (very, very big) difference!

  23. A brief history of time by marvy666 · · Score: 2, Funny

    Just been reading a brief history of time, 10th anniversary edition today. And i could swear this is spoken about in the book.

    Then again I could be wrong, a lot of it is over my head.

    1. Re:A brief history of time by meringuoid · · Score: 1
      Just been reading a brief history of time, 10th anniversary edition today. And i could swear this is spoken about in the book.

      It is. Gamma-ray bursts have been observed for a long time: they were first discovered by spysats designed to watch out for nuclear test ban violations. ISTR that it was initially thought that the Soviets were trying to evade the ban by testing in deep space, but it soon became clear that these explosions were from much further afield.

      The collision of neutron stars has always been the most popular candidate for the source of these blasts: neutron stars are an already well-known feature of the universe, and given their enormous gravity, a collision between two of them would certainly be sufficiently energetic. However, there has never been any direct evidence that they are the cause - until now, apparently.

      --
      Real Daleks don't climb stairs - they level the building.
  24. But how does this fit... by snookums · · Score: 2, Funny

    ...with the Electric Universe theory?

    --
    Be careful. People in masks cannot be trusted.
  25. Re:They explode, hence blackholes are a impossibil by Floody · · Score: 5, Informative

    Before becoming a blackhole any star will explode explode due to fusion of heavy atoms, the heavier they are more energy they will release. like the heavy metals

    That isn't really the primary (theoretical, of course) reason that massive stars "explode" (keep in mind, this is nothing like an explosion as any human understands it). However, the continuing fusion of heavier elements, up to iron, is thought to be the reason for numerous changes a late-lifecycle star experiences.

    Once a massive star reaches the point where the majority of exothermic fusionable material consists of silicon, it has very big problem on its "hands." It's got about a day to live. silicon fuses at about 2.7e+9 K (optimimally), so that's one hell of a last day, and an unbelievable amount of iron production (thank the stars for your iron). Now, this entire time the star has been increasingly putting out more and more energy; that energy has tremendous pressure and serves to balance the star's own gravitional force which seeks to collapse it as closely to a point-source as possible (and it is, of course, theorized ... sometimes it gets its wish).

    At some very critical moment on the last minute of the last hour of that last day, there is no longer enough remaining silicon to keep the reaction going (some of the iron is fusing, but it's endothermic so it's only making the situation worse). Once this magic point is hit, fusion drops off very very rapidly, the remaining lighter-than-iron elements simply won't fuse without enough energy and once its gone ... its gone forever (for that star anyway). Suddenly, gravity has the upper-hand, and in a big way. The entire star begins to contract in on itself, approaching relativistic speeds as it nears the core. The inner core of the star is already highly dense post-fusion material, lots of iron, silicon, oxygen, neon, etc. The outer portion of the star was mostly the light and fluffy stuff: hydrogen, helium, nitrogen, ... But there's a whole lot of it. So, when all this "stuff" comes rushing back in and hits what amounts to an immovable object, it "bounces." Really really hard. So hard that the fundamental forces of nature momentarily cease to exist as we know them. So hard that the energy produced illuminates large sections of galaxies.

    The details that actually occur in those few nanoseconds and microseconds are not completely understood, but it is understood that a great many bizarre interactions take place. The closest anyone can come to understanding this by way of simulation is in a particle accelerator. For one brief moment, this former mega-sized celebrity of a star takes on the apparition of the big bang; unification of forces and other outlandish stylings that no mortal human will ever witness up-close (or would want to if you're half-sane).

    So, what really causes supernovae? Gravity winning.

  26. Re:They explode, hence blackholes are a impossibil by Decaff · · Score: 1

    there are cases where the observations are such that no other solution per the proven theory seems plausible

    There are alternatives, for example the gravastar:

    http://www.absoluteastronomy.com/encyclopedia/g/gr /gravastar.htm

    Such alternatives would yield the same observations.

    There are major problems with current black hole theory - for example, the information paradox, and the central singularity. I think it is pretty reasonable to state that current black hole theory is at the very least incomplete, if not actually wrong.

  27. Astronomy vs Science by Markus+Registrada · · Score: 1, Informative
    physicists will listen to challenges to almost any theory (and are proven wrong on a regular basis, science advances!) ... Black holes have only been accepted for a short period of time, but if you challenge conservation of energy be prepared. ... scientists make mistakes, too, but not usually for long in the face of strong evidence.

    What this implies is that astrophysics, as practiced, is no more science than, say, sociology. Whenever current astrophysical theories are falsified by observation, a fundamental law gets tossed instead. Lately we have "dark matter" (6x as much of it as the visible universe), "dark energy" (18x as much!), "inflation", and distant galaxies producing hundreds of times more light than similar modern ones. All are futile attempts to rescue the Big Bang from the oblivion it earns by being, finally, irreconcilable with observation. (E.g. light-element ratios; gravitational lensing measurements of galactic mass; fractal, filamentary arrangement of galactic superclusters; preferred direction of cosmic microwave background anisotropy; shall I go on?)

    For all the claims of evidence for the role of neutron stars and black holes in galactic-scale events, it all amounts to negative evidence: those are the only way to concentrate enough energy when the only forces you are willing or equipped to work with are gravitation, fusion, and shock waves. Even so, multimillion-degree "hot gases" in free space and 10^14 eV cosmic rays remain beyond their capacity. Current flow in interstellar plasmas easily propagates and concentrates such energies, without reliance on untestable physical laws and ghosts. However, such work can, as a rule, only be published in Plasma Science journals not read (and perhaps not readable) by astrophysicists.

    [p.s. read this quick; /. moderators prefer to prevent discussion of failures of mainstream cosmology and astrophysics.]

    1. Re:Astronomy vs Science by Anonymous Coward · · Score: 3, Insightful

      What this implies is that astrophysics, as practiced, is no more science than, say, sociology.

      You have something against sociology? It's a science too. And ALL sciences are practiced by human beings, who need to be convinced by evidence -- as they should.

      Whenever current astrophysical theories are falsified by observation, a fundamental law gets tossed instead.

      This, of course, is nonsense. The vast majority of new astrophysical phenomena find explanations within current physics.

      y. Whenever current astrophysical theories are falsified by observation, a fundamental law gets tossed instead. Lately we have "dark matter" (6x as much of it as the visible universe), "dark energy" (18x as much!), "inflation", and distant galaxies producing hundreds of times more light than similar modern ones.

      And your point is what? There is substantial evidence in favor of these theories, and all competing theories advanced so far have failed. Sometimes new physics is discovered, you know. Just because you want to stick your fingers in your ears and ignore the evidence in its favor, doesn't mean it's not there.

      All are futile attempts to rescue the Big Bang from the oblivion it earns by being, finally, irreconcilable with observation. (E.g. light-element ratios; gravitational lensing measurements of galactic mass; fractal, filamentary arrangement of galactic superclusters; preferred direction of cosmic microwave background anisotropy; shall I go on?)

      What the hell are you talking about? All of those observations SUPPORT Big Bang cosmology, rather than contradict it. (Except for one mistake on your part: there is no known preferred direction of the CMBR -- but even if there was, there are anisotropic Big Bang cosmologies with preferred directions.)

      For all the claims of evidence for the role of neutron stars and black holes in galactic-scale events, it all amounts to negative evidence: those are the only way to concentrate enough energy when the only forces you are willing or equipped to work with are gravitation, fusion, and shock waves.

      It is not negative evidence. Theories of neutron stars and black holes make specific predictions of what you will see, and those predictions are supported by observations.

      Even so, multimillion-degree "hot gases" in free space and 10^14 eV cosmic rays remain beyond their capacity.

      This turns out not to be the case. Ultra high energy cosmic rays, for one, are within the capacity of jets from supermassive black holes. One current goal is to localize the origin of these rays better to see whether they coincide with such sources.

      The bigger mystery is not whether mechanisms exist to produce them, but why these rays are appearing to exceed the GZK cutoff, which sets an upper bound on the energy of distant cosmic rays that we can detect. (Some possibilities: the experiments are miscalibrated, which is distinctly possible since HiRES and AGASA's curves look the same except one is shifted by 20%; the cosmic rays are nearer in origin than we think; there is new physics or an unaccounted effect that allows violation of the GZK prediction. All are being investigated, and new expriments such as the Pierre Auger observatory should shed light on this question.)

      Current flow in interstellar plasmas easily propagates and concentrates such energies, without reliance on untestable physical laws and ghosts. However, such work can, as a rule, only be published in Plasma Science journals not read (and perhaps not readable) by astrophysicists.

      Oh, I get it, you're a plasma cosmology crank. Well, no, you're wrong: plasma physics gets published in astrophysics journals all the time. Just look at the astro-ph arXiv. However, crank physics which purports to expl

    2. Re:Astronomy vs Science by norton_I · · Score: 1
      [p.s. read this quick; /. moderators prefer to prevent discussion of failures of mainstream cosmology and astrophysics.]

      Most /. moderators would not recognize mainstream cosmology and astrophysics if it hit them in the face, thus I suspect that systematic discrimination against challenges to it are products of an overactive, paranoid imagination.

      From what I have heard talking to several astrophysicists is that they are as uncomfortable with dark energy and inflation as the next guy (dark matter is a little easier -- we know lots of types of matter that don't radiate light -- basically everything except stars). However, they have been unable to come up with any other theories that are as successful at describing the phenomena you mentioned, so inflation is accepted as the current best theory.
    3. Re:Astronomy vs Science by Markus+Registrada · · Score: 1
      Most /. moderators would not recognize mainstream cosmology and astrophysics if it hit them in the face, thus I suspect that systematic discrimination against challenges to it are [ad hominem omitted]

      The evidence, if you bother to examine it, suggests otherwise. Certainly it's not necessary actually to know anything to moderate down criticism of the referenced articles. The timing suggests that when certain individuals get mod points, they go back and moderate down whatever they have seen recently that they disagree with. It's a toadying sort of behavior, hence the systematic bias.

      astrophysicists ... are as uncomfortable with dark energy and inflation as the next guy ... However, they have been unable to come up with any other theories ...

      Yes, that's what I said. Not being versed in plasma physics (beyond inapplicable MHD), they are not equipped to formulate or evaluate models that include it, however well such models predict the observed phenomena. Instead, they cling to models that have been repeatedly falsified, inventing new physics post hoc to cover up the failures, and carefully ignore other evidence. In the meantime, though, the ones who referee journals and sit on grants committees make sure not to allow in anything they aren't qualified to evaluate. "If we can't dance it, we can't teach it".

      It may be human nature, but it ain't science.

    4. Re:Astronomy vs Science by Markus+Registrada · · Score: 1
      You have something against sociology? It's a science too.

      Ha ha. Most sociologists remain Marxists.

      All of those observations SUPPORT Big Bang cosmology, rather than contradict it.

      Only if you ignore the evidence. Light-element isotope ratios were once trumpeted as supporting the Big Bang. Now that they don't match current models, they aren't discussed at polite conferences. Galactic gravitational lensing puts a strict upper limit on mass, leaving no place to put the dark matter. (Unless... yes! Dark energy at work? Or ... maybe supermassive black holes?) You could put your dark matter out in those unaccountable megaparsec-wide voids, except you need it in galaxies to explain why their rotation doesn't match gravitational orbital dynamics (but does match laboratory plasma phenomena).

      ... there is no known preferred direction of the CMBR -- but even if there was, there are anisotropic Big Bang cosmologies with preferred directions.

      This is a capsule example of the phenomenon. Big Bang can't be falsified, because all evidence can be reinterpreted, post hoc, in its favor. There have been other pseudo-scientific regimes like that: Marxist economics, Freudian and Skinnerian psychology, Lysenkoist genetics; lately, Intelligent Design has support in high places.

      Theories of neutron stars and black holes make specific predictions of what you will see, and those predictions are supported by observations.

      Two words: "post hoc"

      Ultra high energy cosmic rays, for one, are within the capacity of jets from supermassive black holes. ... Some possibilities: the experiments are miscalibrated ... there is new physics or an unaccounted effect ...

      Another rich example. The "supermassive black hole", like dark matter, stands ready to rescue any failed model. But if necessary, observations can be discounted, or we can call up even more spirits from the vasty deep. Heaven forfend learning some of the physics of stuff we know exists, and applying it, but that's work. Worse, it's risky because you can make embarrassing mistakes. With Dark Matter (etc.) you never have to admit you're wrong, because it always has exactly the properties you need just when you need them (and not a moment before).

      Oh, I get it, you're a plasma cosmology crank.

      Ah, yes, and the obligatory ad hominem remark. I wondered when he would get around to that.

    5. Re:Astronomy vs Science by Anonymous Coward · · Score: 0

      Light-element isotope ratios were once trumpeted as supporting the Big Bang. Now that they don't match current models, they aren't discussed at polite conferences.

      Uh huh. And the citations?

      Galactic gravitational lensing puts a strict upper limit on mass, leaving no place to put the dark matter.

      Now what are you babbling about? Gravitational lensing is consistent with estimates of dark matter, not contradictory to it.

      This is a capsule example of the phenomenon. Big Bang can't be falsified, because all evidence can be reinterpreted,

      More nonsense. You can't get solutions to the Einstein equation to replicate any observation.

      Two words: "post hoc"

      Idiot. Predictions of ISCOs, event horizons, etc. were made well before any astrophysical evidence of those phenomena were observed. You explain why matter accreting onto the surface of objects the mass of black holes simply disappears instead of producing explosions like it does when it accretes onto the surface of objects the mass of neutron stars. Then look at neutron star phenomenology. Theories of their behavior don't have arbitrarily many free parameters to adjust to whatever you like, you know. Yet the theories still make predictions of their observed behavior, including the once-mysterious glitches.

      Another rich example. The "supermassive black hole", like dark matter, stands ready to rescue any failed model.

      Idiot. Dark matter can't produce ultra high energy cosmic rays, for one. It only has bearing on gravitational phenomena. And completely independent observations of different phenomena highly constrain the allowed dark model theories: we have evidence from stellar orbits in galaxies, the motions of satellite dwarf galaxies, the gravitational lensing you mention, measurements of galactic gas temperatures (depends on the local gravitational neighborhood), anisotropies in the CMBR, the rate and structure of large-scale structure formation, etc.

      The only single model so far proposed that can account for all of those phenomena is dark matter (although its closest competitor, MOND, comes close on some of them, but not so great on others). This isn't because astrophysicists love dark matter, either; most of them hated it. For decades. It just explains too much, is all. And not because it can "explain anything": it's extraordinarily difficult to come up with a model that can account for all observations, and the vast majority of dark matter models in fact -- far from being "unfalsifiable" -- already been falsified. The type, quantity, and distribution of dark matter necessary to explain galactic rotation curves is the same necessary to explain the CMBR anisotropies, is the same necessary to explain hot gas X-ray emissions, etc. etc. There is no a priori reason why that should be the case. That is the hallmark of a strong scientific theory, not "post hoc unfalsifiable fudging".

      Likewise, supermassive black holes cannot "explain anything". (They can't explain the need for dark matter, they can't explain the CMBR anisotropies, they can't explain the supernova luminosity/redshift relations, etc. etc.) But they can explain the existence of enormously energetic particles, and we have extremely good evidence that supermassive bodies exist: we know that compact masses of millions of solar masses exist within spaces of less than a light year. This is an observational fact regardless of whether or not they are black holes or "something else", and the mere existence of compact masses of that scale is sufficient to produce ultra high energy jets.

      (I notice you backed off from claiming that UHECR's are "beyond the capacity" of galactic scale black holes, to merely saying the mechanism is "post hoc".)

      Ah, yes, and the ob

    6. Re:Astronomy vs Science by Anonymous Coward · · Score: 0

      Not being versed in plasma physics (beyond inapplicable MHD), they are not equipped to formulate or evaluate models that include it,

      The astrophysics community has members well versed in plasma physics, certainly well versed enough to discard your plasma cosmology nonsense, much as you would like to believe otherwise. After all, how else can you justify the Scientific Conspiracy necessary to account for why nobody accepts your favorite theory?
      Instead, they cling to models that have been repeatedly falsified, inventing new physics post hoc to cover up the failures, and carefully ignore other evidence

      No, they favor new models that have not been falsified, such as cosmologies without dark matter, MOND, or alternative mechanisms to account for observations. This is how science is done: you replace what doesn't work with something that does. The fact that you, personally, simply don't like the new theories, and carefully ignore the evidence in their favor, says far more about your scientific incompetence than theirs.
  28. You should be ashamed...! by Anonymous Coward · · Score: 0

    "A *LADY* with a smoking gun..."? Why a lady? You're saying that only women are killers? That's sexist and you're a pig!

  29. So... Colliding stars, eh? by hey! · · Score: 1

    How long do you think before God posts the MPEGs on his web site?

    Actually I have a pretty good idea of what's on his site looks like. They'll be somewhere between pages about playing with metallic sodium and his beer recipes.

    --
    Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
  30. Re:They explode, hence blackholes are a impossibil by Anonymous Coward · · Score: 1, Informative

    Fission splits up big atoms into smaller (lower atomic number) ones, so you can't get heavy elements from fission. Fusion is the only process that creates heavy elements. True, fusion to create elements heavier than iron loses energy, but that's why stars die after they start such reactions.

  31. Re:They explode, hence blackholes are a impossibil by barneyfoo · · Score: 1

    My statement wasn't clear. I don't mean that GR is the is the only thing supporting black holes.

    Your demands are very high. Providing alernative theories/explainations for observational data most physicists don't know exist is quite out of my reach. (after all physics has gone under the same brutal specialization that other fields have)

    By the same token, I could criticize your statements as dubiously adherent to an entrenched model that you probably know far less about than you're letting on.

  32. Re:They explode, hence blackholes are a impossibil by barneyfoo · · Score: 2, Informative

    Conservation of energy is already violated according to current annihilation theory. When a positron and electron "annihilate" the energy of the outgoing photons does not include the intrinsic angular momentum energy of the electrons. It dissapears, supposedly.

  33. Re:You're right, they're massive enough. F!=a. by PoorLenore · · Score: 1

    The greater the mass, the greater the force, not the acceleration. Go and get a cannon ball and a ping-pong ball and drop them from the top of the Leaning Tower of Pisa. (Caveats: blah, blah, air resistance, blah, blah, higher order relativistic effects, blah, blah, apocryphal story, blah, blah...)

  34. Re:You're right, they're massive enough. F!=a. by SimilarityEngine · · Score: 1

    Force of attraction = G * m_1 * m_2 / r^2

    Thus, acceleration of first body = G * m_2 / r^2 which is proportional to the mass of the second body. Similarly the acceleration of the second is proportional to the mass of the first. I think this is what the GP meant - heavier stars, more accn.

    --
    Those who can make you believe absurdities can make you commit atrocities. - Voltaire
  35. I don't know about you by ValuJet · · Score: 1

    Astronomers have traced the origin of short-duration gamma-ray bursts But I'd be pretty warry about making anyone from that region of space angry.

  36. Re:They explode, hence blackholes are a impossibil by DavidTC · · Score: 1
    Oh, that's easy to explain.

    It doens't disappear, it just pushes the universe. ;)

    --
    If corporations are people, aren't stockholders guilty of slavery?
  37. Re:They explode, hence blackholes are a impossibil by DavidTC · · Score: 1
    Erm, the problem with gravstars is we know there is no 'quantum gravity' theory even slightly likely to appear in a reasonable amount of time.

    Or did you miss the recent discovery that gravity does not exhibit quantum effects? It was actually posted on here a few months ago.

    That's not to say we will never have a quantum gravity theory, but simple 'gravitons' seem unlikely. Gravity just does not work like the electronuclear forces.

    A lot of people have built a quantum gravity house of cards, but those people seem likely to be disappointed.

    And the information paradox has, as far I know, has been solved by Hawking's discovery that black holes can 'emit' energy.

    --
    If corporations are people, aren't stockholders guilty of slavery?
  38. Re:They explode, hence blackholes are a impossibil by Anonymous Coward · · Score: 1, Informative

    This is not correct. Both total energy and total angular momentum are conserved in particle-antiparticle annihilation.

  39. Re:They explode, hence blackholes are a impossibil by Decaff · · Score: 1

    Erm, the problem with gravstars is we know there is no 'quantum gravity' theory even slightly likely to appear in a reasonable amount of time.

    That is like saying that electrons can't exist because we don't understand what they are! Just because we don't have a theory of quantum gravity does not mean that gravity does not exhibit quantum effects.

    Or did you miss the recent discovery that gravity does not exhibit quantum effects? It was actually posted on here a few months ago.

    I did. URL?

    That's not to say we will never have a quantum gravity theory, but simple 'gravitons' seem unlikely. Gravity just does not work like the electronuclear forces.

    This statement is directly contradicted by the most popular approaches to unification - loop quantum gravity and string theory. String theory states explicitly that there are simple gravitons and they do work like the electromagnetic, strong and weak forces - they are simply different string vibration modes.

    And the information paradox has, as far I know, has been solved by Hawking's discovery that black holes can 'emit' energy.

    That is not even published, and many are doubtful. Hawking has been wildly wrong many times before.

  40. Re:They explode, hence blackholes are a impossibil by arodland · · Score: 1

    By the same token, I could criticize your statements as dubiously adherent to an entrenched model that you probably know far less about than you're letting on.

    You could, but you'd still be in the uncomfortable position of finding (if you ever bothered to do your own investigation into the matter) that GP's theories fit very well with our current understanding of the universe, and that you don't have a better alternative. It's a "put up or shut up" kind of deal.

  41. Re:They explode, hence blackholes are a impossibil by kmac06 · · Score: 1

    Stars don't ever really start such reactions in the first place. I believe there can be trace amounts of nuclei heavier than iron produced in a star, but almost all heavier nuclei are created in a supernova, when atoms are hit with a ton of neutrons. So production of the heavy elements (ie supernova) has little to do with the burning that goes on prior to it.

  42. Re:They explode, hence blackholes are a impossibil by kmac06 · · Score: 1

    According to the notes I took in Astrophysics a couple days, ago, when the core collapses, it goes from R ~ 7000km -> R = 50km in under a second. Pretty quick contraction...

    I never thought I'd use physics notes for a post on /....

  43. Re:They explode, hence blackholes are a impossibil by kmac06 · · Score: 1

    I think the anon poster above me is right. Do you have a link stating this?

  44. Re:They explode, hence blackholes are a impossibil by Decaff · · Score: 1

    And the information paradox has, as far I know, has been solved by Hawking's discovery that black holes can 'emit' energy.

    Sorry for previous comment - I assumed you meant Hawking's recent conjecture that black holes can emit information.

    The emission of energy does not help the information problem, as the energy emitted bears no relationship to the material that made up the black hole.

  45. No friction! by Quadraginta · · Score: 1

    The way I could concieve two neutron stars coming together would be stars A and B travelling on roughly parallel paths through the galaxy, and gravity pulls them together.

    Not possible! If they are not aimed squarely at each other -- which is damn unlikely -- then they are in a mutual orbit. Could be a closed orbit, circle or ellipse, or it could be an open orbit, e.g. one executes a parabola or hyperbola about the other. But the important point is that every possible orbit is perfectly symmetrical about periastron (point of closest approach). If star A comes from light-years away to pass near star B, then star A must fly away to light-years away after the passage. There's no way that Newtonian gravity by itself can turn an open orbit into a closed orbit, i.e. for star A to fly in from far away and "spiral into" star B.

    See, this happens on Earth because friction can slow one object down, and cause one object to spiral into another. I suspect you're unconsciously assuming friction. But there isn't friction in outer space. Except for -- and this is what we're talking about -- gravitational waves, which indeed are a form of "friction" associated with orbital motion.

  46. Re:They explode, hence blackholes are a impossibil by norton_I · · Score: 1

    That just isn't true. Electric fields can and do contain angular momentum as well as linear momentum and energy. In the paraxial apprximation, the circular polarizations are angular momentum eigenstates, and higher order modes can carry additonal angular momentum. Decay of positronium conserves total angular momentum, which includes the intrinsic (spin) angular momentum of the leptons as well as the orbital angular momentum about their common center of mass.

    Furthermore, angular momentum and energy are two different conserved quantities (though they are strongly linked in relativity), so in the unlikely event that angular momentum was found to not be conserved, it would not necessarily violate conservation of energy.

  47. Re:They explode, hence blackholes are a impossibil by RobertB-DC · · Score: 1

    Great post. But I had to look twice near the end:

    The details that actually occur in those few nanoseconds and microseconds are not completely understood, but it is understood that a great many bizarre interactions take place.

    I misread "interactions" as "incantations", and imagined the resulting neutron star looking something akin to the eye of Sauron...

    --
    Stressed? Me? Of course not. Stress is what a rubber band feels before it breaks, silly.
  48. magnetars by halfelven · · Score: 1
    magnetars are way cool:

    A magnetic field above 10 gigateslas is strong enough to wipe a credit card from half the distance of the Moon from the Earth. A small neodymium based rare earth magnet has a field of about a tesla, Earth has a geomagnetic field of 30-60 microteslas, and most media used for data storage can be erased with a millitesla field.

    The magnetic field of a magnetar would be lethal at a distance of up to 1000 km, tearing tissues due to the diamagnetism of water.
  49. Re:They explode, hence blackholes are a impossibil by rhombic · · Score: 1

    "By the same token, I could criticize your statements as dubiously adherent to an entrenched model that you probably know far less about than you're letting on."

    If you get tired of posting here, I'm sure the ID'ers would welcome your support.

    Simple fact is, theories that get entrenched tend to do so for a reason-- they fit the currently available data, and nobody's come up with a better explaination yet. If you don't like the current explaination (presence of ether circa 1901, black holes, evolution, etc), feel free to propose an alternative theory that accounts for current data, can make positive predictions of future experimental or observational results, and can be negated. Contrary to a lot of the BS I hear from electric universe/ID/etc folks, when an alternative theory that fulfills these conditions is brought forward (i.e. special & general relativity), it tends to take off like lightning after a few years, not beaten away by the establishment forever.

    --
    1984 was supposed to be a warning, not an instruction manual.
  50. Re:They explode, hence blackholes are a impossibil by DavidTC · · Score: 1
    I can't seem to find the slashdot article, slashdot does not seem to have any useful search function at all.

    However, the basic concept was that they had figured out a way to cancel out normal graviational effects, so could measure the gravity of tiny objects. Even past the normal scale of quantum effects exhibited by other forces, they didn't notice any quantum effect for the gravity.

    Sadly, I can't seem to find this anywhere. Grumble.

    --
    If corporations are people, aren't stockholders guilty of slavery?
  51. Re:They explode, hence blackholes are a impossibil by DavidTC · · Score: 1
    The emission of energy does not help the information problem, as the energy emitted bears no known relationship to the material that made up the black hole. ;)

    However, I think too early to to figure out what happens inside a blackhole/gravstart, which as far as I can tell is the only difference between the two.

    --
    If corporations are people, aren't stockholders guilty of slavery?
  52. Animation Worth a Thousand Words by awildman · · Score: 1

    The Chandra X-ray Observatory http://chandra.harvard.edu/ priovides a wealth of information and help visualizing these phenomena. While the following link depicts orbiting white dwarfs (not as massive as neutron stars) swirling closer together, traveling in excess of a million miles per hour producing gravity waves...
    Animation of White Dwarf Gravitational Wave Merger
    http://chandra.harvard.edu/photo/2005/j0806/animat ions.html

    --
    "Open Source: The difference between trust and antitrust."
  53. Re:They explode, hence blackholes are a impossibil by Decaff · · Score: 1

    The emission of energy does not help the information problem, as the energy emitted bears no known relationship to the material that made up the black hole. ;)

    No sorry - it definitely bears no relationship at all - it is purely an interaction between the vacuum and the warped space of the event horizon. It is entirely and provably random.

  54. Re:They explode, hence blackholes are a impossibil by Anonymous Coward · · Score: 0

    You're almost certainly misinterpreting something. There is still no experimental evidence for or against quantum gravity. At best, you might be thinking of the large-extra dimension experiments.

  55. Re:They explode, hence blackholes are a impossibil by Anonymous Coward · · Score: 0

    Erm, the problem with gravstars is we know there is no 'quantum gravity' theory even slightly likely to appear in a reasonable amount of time.

    Quantum gravity is largely irrelevant to the formation of gravastars. The problem with them is that they require stellar matter to behave in a very specific and peculiar way upon compression, and we have no reason to believe that it actually behaves that way.

    Or did you miss the recent discovery that gravity does not exhibit quantum effects? It was actually posted on here a few months ago.

    There was no such discovery, if by "exhibit quantum effects" you mean "exhibit quantization of the gravitational field". (Well, of course gravity doesn't exhibit quantization on any observed scale, because it's not expected to show up until the Planck scale, which we can't reach. A sub-Planckian experiment isn't going to establish whether or not gravity is quantized, because it's not sensitive enough to detect quantum gravity effects.)

    That's not to say we will never have a quantum gravity theory, but simple 'gravitons' seem unlikely

    Simple gravitons are unlikely for purely theoretical reasons, although any theory of quantum gravity must behave approximately like a theory of gravitons at low energies. This has little to do with any experimental tests of quantum gravity and less to do with gravastars.

    And the information paradox has, as far I know, has been solved by Hawking's discovery that black holes can 'emit' energy.

    I've heard this result discussed by a number of eminent quantum gravity researchers, and they're very skeptical of Hawking. Not only is his "proof" within the context of an approximation (semiclassical) to a theory (Euclidean quantum gravity) that most people already regard as failed, but he also introduces a small negative cosmological constant as a regulator, which doesn't address the zero CC case of GR or the positive CC of the accelerating universe.
  56. Re:They explode, hence blackholes are a impossibil by DavidTC · · Score: 1
    I didn't say that was evidence for or against quantum gravity. It's just not at the same scale as everything else, which introduces a rather large hurdle to any theory of it.

    And, no, I'm not misinterpeting something. And I found it! Summary here, article here.

    They were trying to measure the quantum effects of gravity, and discovered it didn't appear to have any.

    --
    If corporations are people, aren't stockholders guilty of slavery?
  57. Re:They explode, hence blackholes are a impossibil by DavidTC · · Score: 1
    The problem with them is that they require stellar matter to behave in a very specific and peculiar way upon compression, and we have no reason to believe that it actually behaves that way.

    Huh? The reason it would behave that way would presumably be explained by quantum gravity.

    Hence theorizing about gravstars is silly without such a theory. And such a theory seems extremely unlikely to appear out of nowhere all the sudden unless another Einstein shows up.

    As for information theory, I don't think that's an insurmountable argument against blackholes, whether or not Hawking is right.

    --
    If corporations are people, aren't stockholders guilty of slavery?
  58. Re:They explode, hence blackholes are a impossibil by Anonymous Coward · · Score: 0

    Huh? The reason it would behave that way would presumably be explained by quantum gravity.

    No. Quantum gravity is not even remotely relevant at the energies and densities present in gravastar formation. That's the whole point of gravastars: that their black hole-like behavior is governed by condensed matter effects, not gravatation.

    Hence theorizing about gravstars is silly without such a theory.

    No. Go read the original gravastar paper. Quantum gravity doesn't enter into it.

    And such a theory seems extremely unlikely to appear out of nowhere all the sudden unless another Einstein shows up.

    There are at least three major approaches to quantum gravity that have made significant progress (string theory, loop quantum gravity, and causal dynamical triangulations). A theory of quantum gravity doesn't need to "appear out of nowhere".

    As for information theory, I don't think that's an insurmountable argument against blackholes, whether or not Hawking is right.

    I have no idea what this means. Who said that information theory was an insurmountable argument against black holes?

    And from your other response:

    They were trying to measure the quantum effects of gravity, and discovered it didn't appear to have any.

    This is meaningless. With or without this experiment, quantum gravity effeects were undetectable, because we can't reach the Planck scale. This experiment adds nothing to what is already known, namely that all observations of gravity below the Planck scale obey classical general relativity.

    In fact, that experiment is largely irrelevant to quantum gravity. It only applies to theories, like large extra dimension models (which are not even theories of quantum gravity), which predict microscale deviations in Newton's law.
  59. Re:They explode, hence blackholes are a impossibil by iamlucky13 · · Score: 1

    For the record, intelligent design does not intrinsically deny the validity of any of the current leading theories or observations regarding the formation of the universe, evolution, or whatever else. It simply asserts that some underlying order (God) is behind the functioning of the universe. Think of it as either an alternative to the anthropic principle (the universe is how it is because we wouldn't be here observe that it is if it were otherwise) or else a rather poor articulation of religious beliefs. Sadly, the loudest proponents do, as I gather you've noticed, seem to share much in common with the electric universe crowd.

    Personally, although I see the concepts of intelligent design a feasible and very attractive union of my religious beliefs and modern scientific observation, I don't understand the need to discuss it in public school curricula. Discussing the universe from the viewpoint afforded by scientific observation and theory presents no threat to theology.

  60. Re:They explode, hence blackholes are a impossibil by rhombic · · Score: 1

    I've heard several formulations of Intelligent Design, and I've yet to hear one that doesn't come into conflict w/ basic physics, much less the tons of data we have on cosmology or evolution. The only exception is the purely theistic formulation, that an external Designer set up whatever existed pre-big-bang to such exacting tolerances that it produced, as designed, the universe we observe today. Without getting into the violations of the uncertainty principle in the early universe, this formulation is o.k., in that it's restricting itself to metaphysics and not actually saying anything about how our universe actually works.

    As soon as you start allowing the Designer to tinker with the universe in motion (designing Humans, apes, and other such forms of life) you run into serious basic physics issues-- where is the designer? If the Designer is designing the whole universe, how is the Designer transmitting the designs to various places without violating c? What particles transmit the forces from the Designer to the designed? At what energy would be expect to see such particles in collider experiments, and why have they not been observed? If the designer is interacting with matter (i.e. atoms in DNA), and the interaction is not being transmitted by particles, how are the changes being effected? If you can't posit a rigorous theory, can you at least suggest a theoretical framework?

    When I've asked these questions of those who have suggested ID to me as an alternative theory to our current physical and evolutionary theories of how our universe works, I've only gotten blank stares, or a bunch of mishmash that 1)is non-negatable and 2)progresses from a complete lack of understanding of basic physics and molecular biology. I would truly, truly love to see a formulation of ID that isn't in basic disagreement with the observed way the universe works, but what I've read and heard so far is completely lacking along those lines. I'd be thrilled to be shown to be wrong, please do so if you can.

    --
    1984 was supposed to be a warning, not an instruction manual.
  61. Re:They explode, hence blackholes are a impossibil by iamlucky13 · · Score: 1
    As soon as you start allowing the Designer to tinker with the universe in motion (designing Humans, apes, and other such forms of life) you run into serious basic physics issues-- where is the designer? If the Designer is designing the whole universe, how is the Designer transmitting the designs to various places without violating c?


    I might not consider intelligent design in quite the same fashion as many of it's other proponetns, but, if you're willing to accept my stepping out onto the metaphysics branch, I'd suggest that the Designer, whom I know as God, is Himself independent of the universe He created. Essentially, He exists outside of it and is not bound to it's order, which is part of His creation. In regards to C, my unverifiable conjecture is that it's part of His creation. Remember here, most devout Christians consider God to be omnipotent, which is a pretty dramatic concept. If He can create the rules of physics which govern our lives, why shouldn't He also be able to break them or work around them? And if He's omniscient, neither should uncertainty principle pose any problem?

    As far as proposing a rigorous theory, much less some wonderful proof of God's existance, I can't. I really like the line of reasoning about how the existance of a clock hints at the existance of a clockmaker, but it still requires faith. I can point to all sorts of stories in the Bible or modern times about miracles, but those who haven't experienced them will always be able to come up with an alternative explanation. I will, however, paraphrase one Bible verse, from Mark if I remember right, about life that seems to speak directly to this issue: "The truth is given to those who willing to seek it, but it is kept secret from those who don't." We can grab at little strands of the truth all thoughout life, but ultimately, I believe there's a lot more behind it than many people are willing to accept.
  62. Re:They explode, hence blackholes are a impossibil by logpoacher · · Score: 1
    Thanks! That's such a great post, I had to read it to my family.

    Cheers!

  63. Re:They explode, hence blackholes are a impossibil by rhombic · · Score: 1

    I have absolutely no problem at all with going to metaphysics-- my opinion has always been that science has no place in religion, and vice versa. The formulation you're presenting (i.e. God is omnipotent and omniscient, he (or she ;) is capable of instantaneous action at any point in the universe, and no measuring device we can make can detect his actions) has nothing to do with intelligent design; it's the classical religious formulation of God. I do not and have not ever had any problem with anyone who chooses to believe in God. I'm a scientist (Ph.D. in biochemistry, amateur interest in physics) and I do not and will not get into religious discussions with other scientists; God by whatever name, or the lack thereof, is outside the realm of science and therefore pointless to talk about in a scientific context.

    My issue with ID, electric universers, etc. is that they're disagreeing with current scientific theories, and attempting to promulgate alternative conjectures that are non-negatable, make no positive predictions, and fail to account for all of the current data in hand. When the holes in their conjecture (these formulations are NOT theories by any scientific standard, for the reasons above) are pointed out, the usual response is that the critic is holding onto the old entrenched theory because of inertia, or an unwillingness to seriously consider something new. Not so! General relativity is accepted as a theory because tens of thousands of physicists have been working for a hundred years, and have yet to poke a major hole in it. Believe me, it's not for lack of wanting to. The first physicist who discovers a fundamental contradiction that negates GR is going to have his or her career made in one moment.

    Tens of thousands of evolutionary and molecular biologists have spent over a hundred years taking Darwin's original ideas, and working them into the current theory (that, down deep, has very little to do with Darwin's original hypothesis) that gives us a really good explaination as to how things could have evolved to the current state, and has made very powerful predictions on things like speed of genetic drift & etc. None of these things say anything about religion, though. When religion wants to talk about how things have and continue to work in the real universe we live in, it had better be prepared to back those statements up with some explainations. Otherwise, it's just gonna sound like a first grader's science fair project-- cute, amusing, has potential, but to someone who has worked in the field and is familiar with the currently available data, fundamentally silly.

    --
    1984 was supposed to be a warning, not an instruction manual.