4 ms·

> The resolution is that this only holds for non-accelerated motion. Flying in a loop around the galaxy requires not just high speed but also a constant acceler

> The resolution is that this only holds for non-accelerated motion. Flying in a loop around the galaxy requires not just high speed but also a constant acceleration, giving you the additional effects of general relativity, which complicates the situation by quite a lot, but resolves the paradox. Very interesting response! Thank you for that. I do see why my comment was misleading now. If you don't mind, could you clarify a few things? I'm just really interested in the subject. I understand your point about travelling in a straight line: If a traveller were to travel at the speed of light speed away from a theoretical stationary point then both the observers at the stationary point and the observer within the travelling vessel would appear to eachother as frozen (assuming the traveller had equipment to measure the place they left from), because light wouldn't be able to catch up in either direction. That makes sense. When I said "From the inside looking out, the universe would move much faster" I shouldn't have used the term "looking out", that was definitely misleading now that you've mentioned it. > However, an inhabitant on a star moving at relativistic speed through the universe still falls under the original case - the inhabitants on the star will see the rest of the universe moving in slow motion, while the rest of the universe will see them also moving in slow motion. Your last statement got me thinking... so let's say there are two equally sized vessels that are somehow able to communicate instantaneously (for arguments sake, let's say the travellers are immortal wizards who have a telepathic link). Let's say that one of the vessels is caught in the orbit of a black hole and is travelling at nearly the speed of light, and is constantly accellerating as it gets closer to the singularity (ignoring that tidal forces would destroy the vessel, because of it's wizard shielding). The other vessel is lacadaisically making it's way around a star the size of our own. And let's say that the star and the black hole are slowly drifting away from eachother. My question is this: Will the wizard inside of the vessel travelling around the black hole age more slowly than the wizard travelling around the normal star? Keep in mind that they will never meet (i.e. never share the same world line), but they do still have a telepathic link and can compare their clocks.

deleted 5y ago
[deleted]
dumpsterdiver 5y ago
To expound upon my point, consider that we currently believe that our own solar system is rotating around a supermassive black hole, and in fact all large galaxies are believed to contain supermassive black holes at their center. Our solar system is subject to gravitational time dilation from those black holes, and so while our world lines may never meet with a galaxy far away with its own supermassive black hole, objective time differences will absolutely be present.
user-the-name 5y ago
The thing is, instantaneous communications do not and can not exist in our universe. In fact, there is no such thing as two things happening "at the same time" if they are in different locations. If you observe two things happening at the same time from where you are standing (say, you are see two stars exploding at the same time and you know they are both at the exact same distance from you, so you know light took the same amount of time to reach you), another person who was passing you at high speed at the same time will say that you are actually wrong, those two stars exploded at completely different times, after doing the exact same measurement as you. We talk about the "speed of light" being a constant, but this is misleading. The "speed of light" is actually the "speed of causality". Breaking the speed of light, with some theoretical instant communication, would be breaking causality. In the earlier example, if those two stars each had an emergency beacon that sent you an instant message just as they exploded, you would receive both simultaneously. But the person travelling past you would be very confused about how that could happen, since he clearly observed them exploding at different times.
- dumpsterdiver 5y ago
  > The thing is, instantaneous communications do not and can not exist in our universe. In fact, there is no such thing as two things happening "at the same time" if they are in different locations. I do understand what you're saying, and while I agree that observations differ based on the location of the observers, there's one thing that still baffles me. Quantum entanglement. Let's say that we replace the wizards in my example with a pair of entangled particles, and in fact, for this thought experiment let's pretend that humans and "observers" don't even exist anymore - there is noone left in the universe to observe what is happening anywhere. Wouldn't our current understanding state that the wave function would be identical between the particles regardless of where those particles are located in spacetime? In effect, wouldn't the wavefunction be "happening at the same time"? Mind you, I'm not suggesting that the particles are communicating, simply that their waveforms are identical. It's really baffling to me that one particle could be in an area subjected to massive gravitational distortion while the other is not (a completely different world line), and yet they are always in sync. Thoughts?
  - 5y ago

deleted 5y ago

[deleted]

dumpsterdiver 5y ago

To expound upon my point, consider that we currently believe that our own solar system is rotating around a supermassive black hole, and in fact all large galaxies are believed to contain supermassive black holes at their center. Our solar system is subject to gravitational time dilation from those black holes, and so while our world lines may never meet with a galaxy far away with its own supermassive black hole, objective time differences will absolutely be present.

user-the-name 5y ago

The thing is, instantaneous communications do not and can not exist in our universe. In fact, there is no such thing as two things happening "at the same time" if they are in different locations. If you observe two things happening at the same time from where you are standing (say, you are see two stars exploding at the same time and you know they are both at the exact same distance from you, so you know light took the same amount of time to reach you), another person who was passing you at high speed at the same time will say that you are actually wrong, those two stars exploded at completely different times, after doing the exact same measurement as you. We talk about the "speed of light" being a constant, but this is misleading. The "speed of light" is actually the "speed of causality". Breaking the speed of light, with some theoretical instant communication, would be breaking causality. In the earlier example, if those two stars each had an emergency beacon that sent you an instant message just as they exploded, you would receive both simultaneously. But the person travelling past you would be very confused about how that could happen, since he clearly observed them exploding at different times.

dumpsterdiver 5y ago
> The thing is, instantaneous communications do not and can not exist in our universe. In fact, there is no such thing as two things happening "at the same time" if they are in different locations. I do understand what you're saying, and while I agree that observations differ based on the location of the observers, there's one thing that still baffles me. Quantum entanglement. Let's say that we replace the wizards in my example with a pair of entangled particles, and in fact, for this thought experiment let's pretend that humans and "observers" don't even exist anymore - there is noone left in the universe to observe what is happening anywhere. Wouldn't our current understanding state that the wave function would be identical between the particles regardless of where those particles are located in spacetime? In effect, wouldn't the wavefunction be "happening at the same time"? Mind you, I'm not suggesting that the particles are communicating, simply that their waveforms are identical. It's really baffling to me that one particle could be in an area subjected to massive gravitational distortion while the other is not (a completely different world line), and yet they are always in sync. Thoughts?
- 5y ago