You have to look at the situation differently depending on whether you’re observing from a great distance or actually falling into the black hole. The event horizon isn’t a physical object or wall that you cross – if you were falling in, you wouldn’t necessarily notice any difference as you crossed the event horizon. You wouldn’t turn into light or anything like that at all – you might be killed by tidal forces or something, depending on what kind of black hole it is, and in fact (I believe) could theoretically get all the way to the center intact depending on the conditions. (and yes, you would eventually reach it.)
Who fell into black hole and sent back the information that yes, you will eventually reach the center/surface of whatever it is behind the event horizon?
I'll admit again that I don't really know the mathematics of general relativity space-time, but conceptually I [think I] have a pretty strong grasp on what is happening to the space and time when they are affected by gravity.
The discrepancy between the observations of static and falling observers is pretty much the only thing in relativity that doesn't add up to me. It's the classic question between whether physical reality or our observations and interpretations of them are affected by the relativistic effects.
There is a difference between the relatively [pun absolutely intended] simple differences of time and length based on relative speed in special relativity, but the effets of mass/energy as described in general relativity are, in fact, not very relative at all when you look at things like the clocks in GPS satellites going faster than the same clocks on Earth, and the gravitational lens effects caused by massive objects in space. Mass really does affect the passage of time at different locations, and it really affects the relative volume of the space close to itself.
I know that event horizon isn't any kind of physical object, but it
is a boundary of sorts - when you approach it, you wouldn't reach it because the local volume of space around the horizon increases a lot... the most notable change would be that the amount of space would increase... there would also be other effects such as straight arks of papers bending into curved shapes, and if you had a straight piece of paper and drew a triangle on it, it's angles would sum up to something more than 180 degrees. And pi being smaller than 3.14159265.... As a more alarming side-effect, the volume of space limited by your normal shape would increase, which would cause your internal pressure to decrease (same amount of tissue in increased volume equals less pressure), and eventually you would resemble a deformed and crumpled scarecrow... or if you somehow forced your body to stay in same shape, you would suffer from extreme decompression sickness.
Conversely, the passage of time would result in the clock of the falling observer going slower and slower as the event horizon approached. That too would be just as real as the gravitational time dilatation that causes global positioning satellites' clocks to go slower than clocks lower on the gravitational potential (closer to mass concentration).
This would actually cause the universe to end in a slow thermal death before the falling observer had enough time (literally) to reach the event horizon.
Obviously, considering the observations made by the falling observer, he or she wouldn't notice anything out of ordinary as far as passage of time were concerned - as the observer's velocity increases, he or she would just reach the pulses from a clock at static "altitude" reach the faller with more and more gap in them. However, I suspect that as the gravitational time dilatation caught up to doppler effect, the beacon would start to send the pulses faster and faster, so the situation would appear as nominal [all f***ed up of course] to the observer. Until being splatted by the changed geometry of space-time around and inside him or her...
People often use a river analogy to describe this: if you’re being carried along by the current, and it’s gradually accelerating, you don’t necessarily notice the point where you can no longer swim against it. At one point you could turn around and go back upstream if you wanted, and at the next you might just find yourself swimming in place without actually going anywhere. But if you just go with the flow you wouldn’t be able to tell the difference.
Doesn't really apply here, because it's more like you're floating in a river that looks like it has constant width, but instead as you float along, you would notice the river is wider and wider as you approached the event horizon (dare I say waterfall?
), and you would end up floating in an ocean, going towards a waterfall at the end of the world but you would still never reach it...
A distant observer would see the fall as infinite, because the coordinate system that describes the curvature of space near massive objects no longer applies at the event horizon (you end up with a whole lot of divide-by-zeros). To the person falling into the black hole, nothing appears to change once this boundary is crossed, but the distant observer would see the faller "frozen" on the event horizon until the he’s redshifted out of the visible spectrum and vanishes.
That business with div by zero error is partially what makes me thing that the event horizon isn't just an arbitrary line drawn in the space-time continuum as the escape velocity c -mark, but rather when that kind of escape velocity appears, the space-time forms a V amount of space inside the event horizon, separate from the outside apart from gravitational effects and Hawking radiation. I don't know how it actually makes it - though possibly if you think along the rubber plane analogy, the plane would curve into a toroidal form after the event horizon, coiling into itself and forming a continuous, boundless but finite space.
As to whether anything would change for an observer falling through the event horizon, it's kinda hard to swallow that nothing would change when the General Relativity pretty much states that you end up with a lot of div by zeroes when you try to as much as describe the space beyond the red line (happens sometimes with
the other one too...
), and then people try to say you wouldn't notice anything different in space itself...
...let's just say I am not convinced with that line of reasoning and be done with it.
Poll
more tests on it before we activate it