Anywhere 77-83 light years away would (theoretically) observe WWII happening if they looked at the Earth. Everything we see is in the past due to the finite speed of light, and also due to thought and perception not being immediate either.
It’s harder to say that the present exists in a meaningful sense than the past.
There is no present or future; only the past, happening over and over again, right now. (Eugene O’Neill)
The existence of the past exists in many ways, and the past can’t be changed (yet). We can’t fully discern the present and everything we think exists now is in the past when we try to observe it. So is the present any different from the past? If not then the past must exist or nothing exists. And if nothing exists there can be no future either. YMMV.
The past is in the rear view mirror, and this car hasn’t got a reverse gear.
Yes, but that’s just because the information about the events took time to get there.
Likewise, if I filmed something in WWII and then sent the film to you by snail, when you eventually watch it you will be seeing the past. But that’s not particularly relevant to anything. Only if FTL travel existed would you be able to use spacetime to travel back in time. But since FTL doesn’t, it’s irrelevant.
The film is a representation of the past. When you look at it you see the film in the present. Beings 77-83 light years away visually observing earth would be observing photons that emanated from earth during WWII. Everything we ‘see’ is an image from the past because it takes time for light to reach our eyes. The principle is the same whether you catch the light in a nanoseconds or light years. Seeing a near past when you can still act on the information is clearly advantageous though.
I have a very shaky understanding of relativity, but I have heard (maybe on this board?) that for any two events in spacetime, there is some POV from which they occur at the same time, and some other POV from which they occur at the same place. Is this correct, or close to correct? If so, it seems like it’s talking about something weirder than just the fact that light from very distant sources takes a significant time to reach us.
The problem with understanding what is known as space/time is that we still view both things as separate when they are really just one thing. Even the words space/time reinforce our probably incorrect view of this thing, which is one thing, space and then something we call time.
Until we can understand that this one thing is not two things we will not understand. Perhaps the expansion of what we think of as space is time. If the expansion stopped or slowed down would time stop or slow down?
So in regard to the OP question, it was Mark Twain who said that time is what keeps everything from happening all at once. Maybe everything did/is happening all at once. In that case the past must still exist as does the future.
In that case, the answer to this question (and almost all others) has been/will be/is answered and we can close this thread.
Maybe, maybe not. An analogy:
Here on Earth there’s a great similarity between east/west vs north/south. It’s pretty seamless while driving around in an empty parking lot to switch from one to the other. But the third dimension, up/down, is quite different. Try turning “up” in your car and see what happens.
Even in an airplane, helicopter, or submarine, going “up” is quite different from going “east”.
Without going too far, I think it’s fair to say that time is a fundamentally different thing than is space. They’re allied and neither is found without the other. But they are not the same.
Kinda like what Maxwell had to say about electricity and magnetism: they’re deeply intertwined but are not the same.
Both space/time and electricity/magnetism may in fact be dual different manifestations of some underlying something-or-other. But so far nobody has won a Nobel for explaining what that underlying something is.
It’s gone forever. IMO if the past still exist then we would be able to go back and correct the mistakes we made in the past.
The past still existing in the sense of eternalism doesn’t mean anyone is capable to travel a trajectory from their event to that event.
Just because you can’t change the past doesn’t mean it doesn’t exist. You can’t change the present either, you’re not fast enough to change anything before it becomes the past. And your ability to change the future is still open to debate.
My mother passed away August 24 2022. Can I bring her back to life? No I can’t, but I wish I could! As far as I am concerned the past is the past and does not exist in reality but only a memory of the past exists, which is tearing me up right now!
Both of these are not true for two events. If the space time interval is time-like, then in all reference frames they occur in the same order (and not at the same time). If the space time interval is space-like, then there is a reference frame in which they are simultaneous.
The space-time interval is equal to (space distance)^2 - c^2(time interval)^2 where space distance and time interval is to be measured in a given frame of reference, but the space-time interval is the same in all frames of reference.
How long is now? Does it even have a duration?
In the sense I’m using the term, it doesn’t really make sense to attach a duration to ‘now’, as it is an indexical rather than temporal quantity—it picks out a particular time, but isn’t a (a duration or instant of) time in itself. Similarly, there’s no meaning to asking ‘how big is here’.
That said, there is the notion of the specious present, originating with William James, I believe. This is a temporal concept, and denotes the fact that our awareness doesn’t solely depend on what’s happening now, but on a particular duration. Consider how a note may sound right or wrong depending on the preceding notes: the perception of that note right now is colored by its temporal surroundings. But that’s a different sort of thing.
Yes.
I, at least, think of now as the line dividing past and future, having no dimension. Even saying the word takes way too much time. When my voice - or thought - reaches the O, the N is already in the past. Assigning a duration would maybe mean that time, and by extension the universe, is quantized.
We’re living in the past. “Now” for us may be different for other conscious beings. It would be interesting to interact with an alien being whose perception of “now” is completely and significantly out of sync with ours. What the heck would that be like?