eli5 Is it correct to think of events happening on the far side of the universe or in a different galaxy as occurring “at the same time”?
In: Physics
Yes two events on opposite side of the galaxy can happen at the “same time”, meaning simultaneously, but that does not mean you will observe them happening at the same time where you are. You will see the one farther from you happen later due to the light from the event having to travel farther.
From your perspective…Yes. From the distant object/incident’s perspective…Yes. From somewhere in between…No.
Based on the distance and amount of time it’s takes to travel that distance …. No.
An easier way to imagine it…. Sound travels slower than the speed of light. Imagine The sound of thunder versus the lightning bolt. You see the lightning but hear the sound later. Did they happen when you saw it, or only when you heard it?
Think of a thunderstorm. We know that the lightning and thunder occur “at the same time”, however we on earth observe the lightning first, and the thunder a few seconds later depending on how far away it originated.
It’s all relative.
You have probably noticed that there are a lot of answers here. Yes, No, Maybe, and Depends are all here. Most of them are right, given a certain way of looking at things.
Let me ask you this: suppose something happens somewhere, and you never know. In fact, this event affects literally nothing, even theoretically, about your life. Further, it never will affect anything, and I do mean *anything* about your reality.
Did it happen?
This is the “if a tree falls…” question, but turned to 11.
I personally answer this with “no”. As such, it makes no sense to talk about events having happened until they actually affect you. But then, all those “distant” events are really happening to you, at that moment you are in, in that place you are standing. Other people will receive that information at different times with slightly different perspectives, so you won’t even be able to agree with them after the fact how to assign the time values to distant events. If you move, you might even end up not agreeing with yourself anymore. So what was the point of assigning arbitrary time values again?
This is really difficult to “eli5”, because it gets at the very nature of the universe. Good analogies don’t really exist except to give the most vague outline of what is going on.
Merely changing the direction you are walking can have drastic implications about how the “nows” all line up at distant locations. If you stick to a single frame of reference, you can make it work, but the moment you change references, you get completely different answers.
For all these reasons, I don’t think it is generally useful to consider such distant events happening at the same time in any meaningful way. For a certain reference frame you can make a definition like that work, but that frame is fleeting, making the entire exercise moot.
(as an aside, I love the way the word “moot” sounds. Moot. moot. moooooooot. Great word.)
Time is relative to the observer. Some say that time isn’t how you perceive it, but rather that everything is happening at once. If you look at a supernova for 1000 light-years away, that explosion isn’t happening now as you watch it. It happened 1000 years ago but you are just now seeing it.
Yes. When we observe a supernova always acknowledge that it has already occurred, because it has. We never discuss it as though it was just happening, only that we are just now able to observe it.
Check out The Order of Time, by Carlo Rovelli. He does an amazing job of addressing a lot of this and how we got from Aristotle’s view of “time” all the way through the modern physics definition with respect to relativity and quantum mechanics. (It also debunks some of the flat-out wrong assertions in a lot of the other comments.)
As you can see, it’s hard to answer this question without bringing up topics such as ‘observer’ and ‘relativity’.
The answer is yes, with the contingency that you could never prove or get outside verification that these events occurred at the same time (within a reasonable time frame)
Clearly things are happening at this moment on the other side of the universe. We can just never know or verify what those things are (until the light reaches us)
Time is relative. It happened at the time you perceived it so, yes, it happened at the same time as where you are.
If you were closer, you would perceive it differently.
Time is relative. Someone hits a baseball. Light travels very fast so you see it almost instantly at our scale. Sound is slower so you don’t hear the crack until later.
Your mind perceives these things as instantaneous, yet they have time delay. A Cell phone call has time delay. Time is a cruel mistress.
The answer is, events are based on perception.
Time is irrelevant because it has no baseline. Time is dilated due to speed. Nothing matters. You hear yourself talk to yourself in your ear on the phone. You burn your toe but you don’t feel it for a bit. Gravity distorts space time. Speed distorts space time.
Nothing matters. So, yes, what you see is what you get is the easiest way to manage it. God never made a start point or a ticker for time.
Think too much about it and you’ll want to pull the covers up to your neck, tuck in your toes, and try not to think about infinity.
Short answer? No, it doesn’t. “Over there” and “right now” are two concepts that cannot be mixed.
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