4 ms·

Because, according to special relativity, your plane of simultaneity (how the universe is "changing" from your perspective) would differ from that of someone wa

Because, according to special relativity, your plane of simultaneity (how the universe is "changing" from your perspective) would differ from that of someone walking right past you. See the Andromeda paradox: https://en.wikipedia.org/wiki/Rietdijk%E2%80%93Putnam_argument https://en.wikipedia.org/wiki/Rietdijk%E2%80%93Putnam_argume...

TheOtherHobbes 8y ago
I hesitate to disagree with Penrose, who has forgotten more about relativity than I'll ever know, but... I'm not seeing the paradox. There is no absolute simultaneity in relativity. So the Andromeda Paradox only becomes a problem if you invent a magical FTL chronovisor that allows you to bypass causality and see what's happening anywhere in the universe at your idea of the present time. There's no reason to believe such a device could ever exist. So I don't see why there's any confusion. Both hypothetical observers discover events that happened in the past when the light cone of the events intersects their position in space time. Events in the past aren't uncertain, they're simply unknown in the reference frames of the observers. And because the observers have no causal influence on distant events, they have to watch them unfold passively. It's no different to an incredibly laggy online game. If you're well behind the action, events happen before you can influence them. The fact that someone may suffer twice the lag you do doesn't make the events any more philosophically ambiguous, mysterious, or acausal.
- antidesitter 8y ago
  I’m a bit confused by your response, especially the lag analogy, so I’ll try to ask a clarifying question: is there a fact of the matter as to whether the Andromedean space fleet has already set off on its journey?
amelius 8y ago
By the way, here's a nice video on the topic of simultaneity. https://www.youtube.com/watch?v=wteiuxyqtoM https://www.youtube.com/watch?v=wteiuxyqtoM

TheOtherHobbes 8y ago

I hesitate to disagree with Penrose, who has forgotten more about relativity than I'll ever know, but... I'm not seeing the paradox. There is no absolute simultaneity in relativity. So the Andromeda Paradox only becomes a problem if you invent a magical FTL chronovisor that allows you to bypass causality and see what's happening anywhere in the universe at your idea of the present time. There's no reason to believe such a device could ever exist. So I don't see why there's any confusion. Both hypothetical observers discover events that happened in the past when the light cone of the events intersects their position in space time. Events in the past aren't uncertain, they're simply unknown in the reference frames of the observers. And because the observers have no causal influence on distant events, they have to watch them unfold passively. It's no different to an incredibly laggy online game. If you're well behind the action, events happen before you can influence them. The fact that someone may suffer twice the lag you do doesn't make the events any more philosophically ambiguous, mysterious, or acausal.

antidesitter 8y ago
I’m a bit confused by your response, especially the lag analogy, so I’ll try to ask a clarifying question: is there a fact of the matter as to whether the Andromedean space fleet has already set off on its journey?

amelius 8y ago

By the way, here's a nice video on the topic of simultaneity. https://www.youtube.com/watch?v=wteiuxyqtoM https://www.youtube.com/watch?v=wteiuxyqtoM