How Would an Astronaut Falling Into a Black Hole Die? 412
ananyo writes "According to the accepted account, an astronaut falling into a black hole would be ripped apart, and his remnants crushed as they plunged into the black hole's infinitely dense core. Calculations by Joseph Polchinski, a string theorist at the Kavli Institute for Theoretical Physics in Santa Barbara, California, though, point to a different end: quantum effects turn the event horizon into a seething maelstrom of particles and anyone who fell in would hit a wall of fire and be burned to a crisp in an instant. There's one problem with the firewall theory. If Polchinski is right, then either general relativity or quantum mechanics is wrong and his work has triggered a mini-crisis in theoretical physics."
Re:Bad headline (Score:5, Interesting)
Re:We must find out for sure! (Score:4, Interesting)
Hmm, working this out for myself:
The radius of the event horizon is:
R = 2GM/c^2
a = GM/R^2 = c^4/(4GM)
The units are right, so I think that's right. Setting a = g we get
M = c^4 / 4Gg ~= 3 * 10^42 kg ~= 1.5 * 10^12 solar masses
So, yeah, I was way off.
Still, a trillion-solar-mass black hole could possibly exist in the universe to lob monkeys at, I'm betting on the monkeys surviving the event horizon passage for a while.
Re:We must find out for sure! (Score:4, Interesting)
light can easily escape from 1g
Turns out it can't. Surprising, isn't it? The magnitude of gravity at the event horizon isn't why light can't escape - it's the fact that space itself is effectively rushing into the black hole. There aren't really any good intuitions to be had about conditions at the event horizon.
I'm not good enough to explain it well, but I think of it as the "time" direction points towards the singularity at the event horizon. No matter how good your engines are, you can't apply that thrust in a direction useful for escape.
Re:Gravitational time dilation (Score:5, Interesting)
Re:We must find out for sure! (Score:4, Interesting)
Blackholes might not be that uncommon.
http://physicsworld.com/cws/article/news/2013/mar/15/micro-black-holes-could-form-at-lower-than-expected-energies [physicsworld.com]
There are even some theories that some ball lightning could be due to blackholes:
http://en.wikipedia.org/wiki/Ball_lightning#Black_hole_hypothesis [wikipedia.org]
Imagine a tiny blackhole with literally tons of charged particles beyond the event horizon (which is not far away for a tiny blackhole) in close very high speed orbit around it. Those particles might still be affected by magnetic fields, and how about their gravitational effect on the blackhole itself?
Perhaps some real physicists can explain what would happen in such a scenario.
Re:We must find out for sure! (Score:5, Interesting)
No matter the size of a black hole, gravity at the event horizon is finite. You could always in theory build rockets more powerful than whatever it is. It won't help you.
Newtonian acceleration determines how much gravity you feel, but not how you actually move, near a black hole, because space itself is effectively rushing across the event horizon.
I'm not good enough at this to explain it well, but as I replied to a sibling post, I think of it as if the time axis has rotated to point towards the singularity. As I understand it, the event horizon is where the time axis points at 45 degrees off the center, and no matter how hard you accelerate, you can't quite change your own vector more than 45 degrees off the time axis, so you're stuck.
Maybe we'll get a physics prof to wander past and explain this better!
Re:Gravitational tides will kill you (Score:5, Interesting)
While yes, one of the things you would have to deal with is the incredibly hot material swirling around the event horizon which, in and of itself, should produce enough X-rays to fry you, I think this article is actually talking more about an actual characteristic of the event horizon, as opposed to what is in orbit around it, or even what is infalling.
In short, space is supposed to look the same to an observer no matter what side of the event horizon they are on. Instead, a special condition where you smack into something that is there beyond what you would expect from a black hole with infalling matter occurs. That "wall of fire" obviously consists of stuff that has entered the event horizon of the black hole, but it is structured in such a way as to form a highly energetic barrier that should not be there based on our current understanding of relativity or quantum mechanics.
Re:Gravitational time dilation (Score:4, Interesting)
This reminds me of the two unknowns: how can a black hole be created if the matter falling to it can never get there? The another one is of course: how can gravitons escape event horizon and attract anything?
I think good theorists can answer both - I cannot either.
Re:Gravitational tides will kill you (Score:5, Interesting)
All so-called "discoveries" of black holes are attributed to their supposedly enormous gravitational effects on their surroundings, but they never themselves have been found. The same is true of dark matter. The link you gave is all about how the gravity supposedly affects the surroundings of a black hole.
http://www.cfa.harvard.edu/seuforum/bh_reallyexist.htm [harvard.edu]
ALL the observations in that article can be explained by the operation of a force 36 orders of magnitude greater than gravity. This force is electromagnetism as evidenced by cosmic plasmas that can be accurately modeled not only with computers, but with real physical experiments in the lab. Most of the universe is not nicely electrically neutral, like here on earth, but consists of highly charged electrically active plasma. Most atoms in the universe don't have all their electrons nice and neatly orbiting their nuclei.
Scientists are observing immensely powerful cosmic rays and other radiation from many sources in the universe. All this radiation involves the electric force and has nothing to do with gravity. Scientists have postulated that there should be gravity waves and have spent gobs of money to try and detect these, but so far that has been money wasted since they have not found such waves. In addition, there are measurements of immense magnetic fields in space and on the sun. It is a firmly established principle of science, that magnetic fields can be generated easily by the motion of electric charges.
The large-scale universe is controlled by electrical forces that are far greater than gravity. Gravity is only a controlling factor in electrically neutral environments such as we have here in our corner of the universe. Even if only one atom in 100 billion loses one of its electrons, the force generated by this tiny charge imbalance is far greater than the gravity generated by those 100 billion atoms. You can verify that by doing an experiment right in your own home. Just pick up a few bits of Styrofoam with a charged glass or plastic rod. Charge the rod by rubbing it with a silk cloth. The electric charge on the glass rod will easily overcome the gravity generated by the entire Earth.