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posted by martyb on Thursday June 18 2015, @11:27AM   Printer-friendly
from the two-steps-forward-and-there's-no-turning-back dept.

Are black holes the ruthless killers we’ve made them out to be? Samir Mathur says no. According to the professor of physics at Ohio State University, the recently-proposed idea that black holes have “firewalls” that destroy all they touch has a loophole.

In a paper posted online to the arXiv preprint server, Mathur takes issue with the firewall theory, and proves mathematically that black holes are not necessarily arbiters of doom. In fact, he says the world could be captured by a black hole, and we wouldn’t even notice.

More than a decade ago, Mathur used the principles of string theory to show that black holes are actually tangled-up balls of cosmic strings. His “fuzzball theory” helped resolve certain contradictions in how physicists think of black holes.

But when a group of researchers recently tried to build on Mathur’s theory, they concluded that the surface of the fuzzball was actually a firewall.

According to the firewall theory, the surface of the fuzzball is deadly. In fact, the idea is called the firewall theory because it suggests that a very literal fiery death awaits anything that touches it.

Mathur and his team have been expanding on their fuzzball theory, too, and they’ve come to a completely different conclusion. They see black holes not as killers, but rather as benign copy machines of a sort.

https://news.osu.edu/news/2015/06/16/​fuzzyhologram/


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  • (Score: 4, Insightful) by pTamok on Thursday June 18 2015, @01:31PM

    by pTamok (3042) on Thursday June 18 2015, @01:31PM (#197793)

    The event horizon is the surface around a black hole defined by the property that at any point on that surface, the escape velocity exceeds the speed of light.

    However, for a sufficiently large black hole, you will not notice transitioning the event horizon, blood will still flow from your feet back to your heart; nerve impulses will still reach your brain from the 'other side' of the event horizon. It is just that any trajectory you follow that starts at or below the event horizon will always end up back in the black hole, eventually. It is not a hard border.

    Think of firing cannonballs from the surface of the earth. For low velocities, the cannonball will follow a parabolic path and end up back on the surface. As you increase the muzzle velocity, the highest point reached by the cannonball gets higher and higher, but it still comes back. Evenually, you fire the cannonball fast enough (roughly 7 miles a second) that it never comes back. That is the escape velocity.

    For a black hole, the escape velocity at the event horizon is the speed of light. This means that you cannot fire a cannonball fast enough to never come back. But it can still rise a long way above the event horizon before returning. For a very large black hole, the gradient of the force of gravity can be arbitarily small, so you don't notice 'going through' the event horizon. You can throw a ball upwards with no problem, and it will come back. The point is, you can't throw a ball upwards fast enough for it to never come back.

    ...that's how I understand it, anyway, but I'm not a physicist, and I'm very happy to be corrected! There might be some odd relativistic behaviour to do with gravity and time I am not taking into account...

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  • (Score: 1, Informative) by Anonymous Coward on Thursday June 18 2015, @02:32PM

    by Anonymous Coward on Thursday June 18 2015, @02:32PM (#197814)

    However, for a sufficiently large black hole, you will not notice transitioning the event horizon, blood will still flow from your feet back to your heart; nerve impulses will still reach your brain from the 'other side' of the event horizon.

    While you indeed won't notice passing the horizon (at least as far as general relativity is concerned; what happens if you add quantum mechanics in the mix is exactly what's the point of the firewall debate), it is not true that your blood will flow back up beyond the horizon. Rather you'll fall through the horizon quickly enough that even a photon starting at your foot that somehow remains unaffected by all the matter of your body would not reach your head before the head also passed through the horizon.

    • (Score: 4, Informative) by pTamok on Thursday June 18 2015, @04:13PM

      by pTamok (3042) on Thursday June 18 2015, @04:13PM (#197870)

      I don't know if you are right, but having discussed this with a wandering astrophysicist, my simple explanation above is wrong, starting with my overly simplistic definition of the event horizon. I am sorry for having mislead people. Please moderate my previous posting down, so people are not misinformed.

      There are some seriously weird physics around black holes, so my description didn't take into account relativistic complications that frankly, I don't understand.

      Once you are below the event horizon, there is no trajectory that takes anything that has mass, or zero mass back above the event horizon, even temporarily.

  • (Score: 1, Disagree) by dak664 on Thursday June 18 2015, @07:06PM

    by dak664 (2433) on Thursday June 18 2015, @07:06PM (#197929)

    My take is, as light and matter is sucked in, the interior of a so called black hole is going to get progressively hotter, until plasma boils through the so called event horizon and emits enough radiation to balance the incoming energy.

    You could make a similarly silly argument about photons never being able to escape from the center of the sun because they are certain to be absorbed before reaching the corona. True if multiple interactions are hypothesized away, but unphysical in the extreme.