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Comment by kinai | Hacker News Reader

There is a misconception: Light cannot escape a black hole for gravitational reason (not to mention that gravity does not exist, it is a not a force, read up General Relativity). The real reason is that the space-time curvature does simply not provide a way for the light to go back. Same reason you can't go to the end of the universe if the universe would be a sphere.

Also if someone likes to talk about black holes it is good to remind people that it is not a hole...as the article mentions its a region, to be more precise it is a region in space-time that is cut off from ours. The whole issue is not just spacial but also temporal, that is usually the point when your brain gives up understanding the whole problem.

A good description would be: a black hole is the collection of events that do happen outside our space-time/universe. This also explains some of the paradoxes near the event horizon.

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> The real reason is that the space-time curvature does simply not provide a way for the light to go back. Same reason you can't go to the end of the universe if the universe would be a sphere.

Or the same reason you can't travel to yesterday - there are simply no directions in which to point yourself in order to get there.

So basically it's impossible to know what is "inside" a black hole because it's not part of this universe ? But aren't black hole formed by stars that collapsed under their own mass ? So black holes are created from objects that belong to this universe right ?

I get the idea that black holes aren't like a sink. However all that matter or light that get "trapped" into it must go somewhere, in some form .

Yep. Black holes aren't phenomena of matter, they are formed initially from matter but they are phenomena of space-time. The event horizon is basically a one way door, there's no way, no route in space-time, to cross it and return.

But black holes evaporate?

The curvature is the cause of the event horizon, the mass or energy is the cause of the curvature. Remove energy and you remove curvature, remove the curvature and you remove the event horizon.

Only if you go beyond general relativity.

Once you include quantum physics there are some strong indications that black holes must somehow evaporate (although this hasn't been observed directly), but that model is still incomplete.

Yup, and that's a problem that hasn't been fully worked out yet.

So, it's an 'information' black hole, right? But matter, energy, whatever is trapped inside it with very high density and does not simply vanish right? .. Or am I completely wrong?

Not necessarily.

https://en.wikipedia.org/wiki/Black_hole_information_paradox

> Information is stored in a baby universe that separates from our own universe

I like this idea, but then it means that there is no universe but multiverses, yet these multiverses need to be part of a greater structure or container, right ? do we have clues that strongly suggest the multiverse theory ?

http://www.independent.co.uk/news/science/black-holes-are-a-...

We have many theories but little evidence of any of the theories having to do with black holes.

From a practical point of view, the baby universe theory is no different than the “information is lost” theory. Although it might be satisfying to think that information is not “really lost”, there is no way in which we -- in our universe -- would be able to tell the difference. The distinction is philosophical, not physical.

There is a different theory not mentioned prominently on that page that in my opinion provides the most useful resolution: Black Hole Complementarity. In a sense it is not a satisfying resolution, because it basically states “the paradox is not a paradox”. It is very counter-intuitive, but that is a problem with intuition. The wave-particle duality of light, which is nowadays not really considered a paradox any more although it was ~110 years ago, is a good analogy. As always happens with questions like these, in the end the answer is “that is a nonsensical question to ask”.

Black holes have always fascinated and terrified me, don't know why. Just something mysterious about them.

Is not gravity just what we call the effects of the curvature of space-time and more or less equivalent?

Not really.

My personal belief is gravity is directly proportional the amount of space between particles. An object with extreme particle density will correspondingly have extreme gravity and vice versa. This has been observed in neutron stars, which are tightly packed.

Extrapolating out this theory, I think black holes are so gravimetrically attractive because they feature a kernel of maximum-density matter at their core.

If one consider that exactly opposite is true - gravity actually do exist as a "function" of a matter, but space-time doesn't (especially a curved one) being a conditioning of our "serialized", self-centered perception, everything, it seems, falls to its places.

I'm pretty sure this doesn't make any sense. How are you explaining away spacetime?

Gravity is not a function of matter, and proving that curved space-time is real is trivial. So not sure where you are going with that idea...

Could you, please, give me a link for the proof of existence of time. Not some processes in the Universe, but time itself.

You can find a wealth of information at https://en.wikipedia.org/wiki/Time

I am afraid I don't quite understand you, my friend. Are you trying to suggest that existence of this particular page or any part of its content constitutes the proof of existence of time as an independent from an observer phenomena?

May be it somehow related to Kantian view mentioned there about time as a mode of perception, being, as he said, prior to all perceptions, as a condition, but not of observable phenomena, but of sequential mode of perceptual machinery of an observer?

But, as far as I know, in Russia "Kant - lokh".

It was painful, but there was a time when they actually defined equations for the earth being the center of the solar system which matched observations. The equations were a mess, but they managed to force the math into their hypothesis. Then Copernicus came along. Do you still believe the earth is the center of the solar system?

I'm sure you can twist the math upside down and get the same results defining gravity as a function of matter instead of as curved space time using some modified newtonian mechanics or such, but do you really believe that's correct?

Which experiment proves existence of time (apart from some physical process), especially its slowdown and acceleration, like in famous theoretical example with accelerated clocks?

As far as I remember, in the philosophy of science a single contradiction is enough to refute a hypothesis and is the reason to check one's premises..

Some himera made out of math and popular but unproven theories is a himera nevertheless.

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