I am genuinely curious about this. I *kind of* understand that gravity, like light, moves at the speed of light (right?). So then would our solar system, and millions of other star systems, just continue orbiting what USED to be the super massive black hole in the center of our galaxy, if said black hole just suddenly (hypothetically) collapsed/vanished? How does that not violate the laws of physics?
Furthermore – let’s say a star… a hundred light years away went supernova. We’re still receiving it’s light for a hundred years right? It would just look totally normal to us in the sky, for the next hundred years. Well let’s say that supernova was so awesomely powerful as to truly push our planet out of orbit from our sun. What happens first? Does that star’s supernova explosion light up in the sky, or does that impact from this supernova hit us and cause catastrophic damage? What’s faster – the impact or the supernova?
I really want to understand distance/time better as it relates to astrophysics, I just can’t comprehend the insane distance and the deltas between distance + time = what we experience on earth. It’s truly humbling.
In: Physics
>If the center of our galaxy […] hypothetically collapsed on itself
Ain’t nothing hypothetical about it, the center of our galaxy has collapsed on itself. We are very confident [there is a supermassive black hole](https://en.wikipedia.org/wiki/Supermassive_black_hole#In_the_Milky_Way) at the center of our galaxy. In that article is a black and orange image; that’s an image of a supermassive black hole in another galaxy – I believe ours is still too hard to image since we’re looking at it on end with a spiral galaxy (our own) in the way. The black hole in the middle of that image is just larger than our solar system.
>…we wouldn’t know for tens of thousands of years. So then in the meantime, what exactly is our solar system orbiting, if it no longer exists?
Nothing moves faster through space than causality, which is why light moves at that speed. So do gravitational waves.
Let’s reduce this scope to something more manageable. If our sun collapsed into a black hole, right now. we wouldn’t see the effects for 8 minutes. Then, suddenly, the lights would go out. In the mean time, while we’re waiting for the light of the event to reach us in 8 minutes, we would continue to orbit as normal.
And after? Ostensibly, we would continue to orbit as normal! Gravity is the effect of mass over distance. The further away you get from something massive, the less the significance of gravity. If you parked a space ship at the same distance from the black hole as the “surface” of the sun once was, you would feel the same amount of gravity act on your body as though you were standing on the surface of the sun. It’s only when you start getting closer to that infinite well of gravity does the effects of a black hole we talk so much about actually come into play. If the sun collapsed into a black hole, it would be no more than 6 kilometers across – the entire mass of the sun in that little space. Don’t wander too close…
In contrast, as you go underground and get closer to the center of the Earth, you get lighter. Scales with 3 or 4 places of precision need to be calibrated depending on where they are on Earth, because their distance from the center, and the amount and composition of rock underneath them will influence the precision of the scale, including going down into the deepest mine shafts.
Now if all these things just *vanished*, then in 8 minutes, we would go from orbiting the sun to being cast off at some trajectory, into the darkness.
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