Comment on trapped in the middle with u
Gloomy@mander.xyz 2 weeks agoDo time and space realy change places if you go past the event horizon of a black hole? How does that work?
Maybe not the right field of knowledge, but i heard this recently and haven’t come along anybody able to dumb it down enoth for me to understand. So I thought I might ask anyway :-)
knightly@pawb.social 2 weeks ago
As far as we can figure it, basically, yeah. Wrapping your brain around the concept
So gravity gets stronger the closer you are to a black hole, but at the event horizon things get weird. The extreme curvature of spacetime forces space itself to flow toward the singularity at its center faster than the speed of light, so on the inside there’s no “other” direction to point to, even photons emitted straight “out” can’t reach the event horizon and end up moving in the same direction as everything else. So space becomes timelike, proceeding inexorably from point A to B.
Time is more complicated, because it’s really hard to visualize. If you fall into a black hole, you’ll pass through all the outward-pointing light that’s been failing to escape since the event horizon formed, which puts all the past history of the black hole below you. Meanwhile, anything that falls into the black hole in the future can be seen above as its downward-pointing photons catch up. The entire timeline of the interior evolution of the black hole is laid out in the light coming toward you from either direction, making it spacelike.
Gloomy@mander.xyz 2 weeks ago
Thanks for your answer. The space part is easy but the time part still goes over my head.
knightly@pawb.social 2 weeks ago
It helps a bit if you think of time inside a black hole like an onion. The outer skin is the event horizon where information about the moment the black hole was created is “stored”. Going deeper leaves that past behind you and surrounds you with more recent light, and each new layer is smaller than the last because there’s less past to pass through between the moment the black hole was created and the moment you fell in. The singularity is the point at the center where there’s no more past left to see but future light can reach you from all directions.
chuymatt@startrek.website 2 weeks ago
So, would it be incredibly bright ‘above’ and absolute darkness ‘below?’
knightly@pawb.social 2 weeks ago
That depends on one’s position on the path from the event horizon to the singularity. At the event horizon you’ll pass all the outward-pointing photons that were emitted the instant the event horizon formed, making all of “down” impossibly bright. Deeper, the only light that reaches you from “down” is light that entered the black hole at an angle and looped around the singularity before you caught up to it, creating a ring of light around an circle of absolute dark. That ring grows thinner and the black circle expands as you get closer to the singularity.
Photons from above have the opposite appearance, with an expanding ring of blackness around a contracting circle of incoming light paths.
Redfox8@mander.xyz 2 weeks ago
Thanks for your reply, nice and clearly described for my amateur physicist brain to follow! ;p I’ll reply in full when I’m less tired, but intrigued by your reply about time! In summary I think of it as a way of describing how something changes, rather than time actually existing. I.e. it’s relative to the energy the object has…so is a way of describing how much energy it has. I see you talk about black holes in a reply to someone else and my first thought is - the idea that time slows as your get closer (or is that a popular misconception?) relative to my thinking is that actually the particles are loosing energy, not time actually changing - and therefore would any particles actually catch up with each other as you describe? Let alone be observable to be moving.
And thinking about your last paragraph - are you not simply describing that object A which entered the black hole before object B, is simply is closer to the centre than B at any given ‘time’ which err doesn’t exist. And neither does space come to think of it. Space is the nothingness between something, so also just a way of describing how something changes or interacts with something else. E.g. 2 particles exert a force on each other and move closer together through an exchange of energy - space is simply part of a description of how much of the interaction has been completed, similar to time, hence why they’re thought of together and also as one and the same.
The distance thing is therefore how much force, what force and how strongly a force is being exerted rather than a physical thing.
Which (now a bit of side thought I had half an hour ago!) makes me think that black holes have no centre and the singularity is rather like the surface of a sphere, at which point all matter has no energy left to move - or perhaps its better to describe it that all matter’s energy is now potential energy due to the immense forces at work, a bit like a compressed spring.
Erm ok so I replied a lot in the end! I hope it makes some sense, I could probably ramble on some more but I’d better stop fir now! though I do realise there may be some concepts that I’m ignorant of that could destroy my thinking, so feel free to deconstruct!
knightly@pawb.social 2 weeks ago
So you do have a minor misconception there in that first paragraph, time dilation is relative. The slowdown of something falling into a black hole is seen from the perspective of a distant observer, the thing falling in sees the outside universe running in fast-forward during the fall toward the horizon. Neither is losing energy, the extreme curvature of spacetime stretches out the light moving outward and compresses it in the other direction.
As to whether any particles can catch up to each other beneath the event horizon, our best theories suggest it is indeed possible. The steeply curved spacetime beneath the event horizon should still include valid paths where particles thrown in at an angle will intersect with each other as they spiral in. Velocity is relevant too, something that dives in at 99% the speed of light should be able to catch up to something that was dropped from a relative standstill just above the horizon.