Delicious_Wrap4944 t1_j9ng8wk wrote
It’s relative to gravity/speed time is slower on the space station than on the earth surface. It’s only really noticeable on the extreme scales of gravity or speed such as 99% the speed of light or a blackhole.
Siliskk t1_j9ngcw0 wrote
Assuming galaxies spin around their black holes, wouldnt a planet closer to the center move alot faster and therefore experience time alot faster?
Nerull t1_j9nh2oj wrote
A planet near the black hole would experience time much slower, not faster. Being in a gravity well slows down time relative to a point far away from it.
Delicious_Wrap4944 t1_j9ngjm6 wrote
Yes but again it’s really only noticeable towards to unimaginable extremes with things like that we are talking only a few seconds maybe different for an entire year max. You probably can’t get to or will not survive anything that’s in the extremes
Siliskk t1_j9ngs4u wrote
Sorry for the continued questions but would this apply to galaxies further out towards the edge of the expanding universe considering the universe is expanding so fast that galaxies are moving away from us at (cant remember the exact speed) lets say lightspeed? Appreciate your time, just a boggling thought
Delicious_Wrap4944 t1_j9nhcwe wrote
To the observer us say a galaxy moving away at the speed of light time would stop for them as we view it because the light would no longer be able to reach us as they are traveling away just as fast as light. They out there on the other hand would kinda see the same thing of us time would stop as they are moving away to fast even though it would appear we are moving away to fast because everything is moving away from everything else all at the same time.
Siliskk t1_j9nii82 wrote
Makes sense, i hope we find more answers soon! Very captivating stuff
DudeWithAnAxeToGrind t1_j9npceg wrote
Those galaxies moving away from us are not moving through space. They are carried away by expanding space. That's a very important difference. A lot of this stuff applies only to things moving through space.
ptglj t1_j9nrvv1 wrote
We are "the edge of the expanding universe" from the perspective of the galaxies you are mentioning. Any given location in our universe looks like it's the center, so the edges of our own observable universe would not be experiencing anything different than ourselves.
Siliskk t1_j9nh507 wrote
Another thing to note is the interstellar movie, where on the planet 1 hour is 7 years on earth. If a civilization lived on a planet like this but opposite, where 1 hour on earth is 7 years on their planet, or perhaps more, it could be very likely
apple-pie2020 t1_j9nkovy wrote
It’s been a while since I saw the movie. I believe the one hour on the other planet created a +7 year earth time for the astronauts because an hour on that planet plus the trip home at near light speed was what caused the time. It’s a function that accounted for the delayed trip home and the travel at near light speed
[deleted] OP t1_j9npflu wrote
I think you may be misunderstanding the movie...(or I'm misunderstanding you...) There was no lightspeed travel. It was a wormhole. The time dilation was solely due to the proximity to the blackhole.
apple-pie2020 t1_j9owp0d wrote
Ok. It’s probably me. It’s been a good five years since I saw it. I’ll rewatch it, it was entertaining
DudeWithAnAxeToGrind t1_j9nrtvc wrote
It was very over exaggerated in the movie. The effect is real. There's time dilation due to both special relativity (the speed of satellite) and general relativity (how deep in the gravity well the satellite is).
The time dilation in the movie is so extreme, that I'm not sure a planet could even exist so close to the event horizon. There is such thing as innermost stable orbit around black hole; I wouldn't be surprised if for such extreme time dilation, a planet would need to orbit closer than innermost stable orbit (which would be impossible).
The clocks are slowed down by orbital speed, and also slowed down by how "deep" in gravity well they are. This means anything in orbit will experience its clock slowed down depending how fast it moves. Further away, the slower it moves, the less the clock in the satellite is slowed down compared to the surface of the body it orbits. However, the further away the satellite is, higher in the gravity well it is, and faster its clock ticks compared to the clock on the surface of the body it orbits. In case of Earth, there is an orbit where these two effects cancel each other. See this graph https://en.wikipedia.org/wiki/Gravitational_time_dilation#/media/File:Orbit_times.svg
DudeWithAnAxeToGrind t1_j9q4l6z wrote
Here's where somebody actually did the math:
TL;DR For such extreme time dilation, the planet would need to orbit just outside of photon sphere. There are no stable orbits that close to the event horizon; the planet would either fall into the black hole, or it'd be flung out into space.
The photon sphere is a sphere around the black hole where gravity is so extreme, photons are orbiting black hole in circles.
The black hole would need to be supermassive. Because anything smaller (e.g. solar mass black holes), the tidal forces that close to the event horizon would be so large, they'd shred the planet into tiny pieces... Or basically anything else, such as spaceship or a human.
For entire solar system to be so deep in the gravity well to experience time dilation as extreme as in the movie, and not be either destroyed or stripped of its planets, the black hole would need to be many orders of magnitude larger than anything we have ever observed. From what we know, no such black hole can exist. There was simply not enough time since Big Bang for any to grow that large, and due to the expansion of universe, no black hole will ever be able to grow to such a large size.
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