Hi all, I didn’t know how to formulate the question in a non stupid way so I’ll explain.
If the light we see from stars in the sky are actually “the past” as they’ve left their source light years ago, from another point in the universe another planet sees our Sun’s light the same way, correct?
If that’s the case, if there was an “universal year” or an “Universe’s current year”, would all the stars and planets be living in the same year?
Maybe I am 5, I feel 5 right now.
Thanks 🙂
In: 466
No there is no standard universe time. Things happen when they are experienced or interacted with. We say the light left millions of years ago ….but did it? The only information we have is when the light arrived. We extrapolate backwards in time from our point of view but everything meaningful about that distant star is happening right now. It’s gravity it’s light all are “now” to us,
Unless we develop faster than light travel. Then there could be a universal time
One thing is reality, and another thing is information. Photons (light particles) forming a pattern that your eyeballs+brain can interpret is nothing but information. The actual photon is in the present, not the past
So no, the past doesn’t exist, but clues about what it looked like do exist, all around the universe.
It’s mind-blowing to think about, but if we consider that light from stars is the past and they see our Sun’s light the same way, then it’s possible that all stars and planets could be living in the same “universal year.” Time in the universe is fascinating! 💫
Yes it exist at the same time but we don’t perceive it as so. Say you and a friend are on opposite sides of a pool and you jump in. The wave occurs as you jump in but across the pool your friend wouldn’t notice until it reaches them.
Light from the sun takes a little over 8minutes to reach us so when you look at the sun you see it as it was 8minutes ago.
If you really want to go down the rabbit hole you can look up an effect known as gravitational lensing which we can sometimes use to see different points of time due the the bending of light by gravitational forces.
Two people roll a ball to you at the same time. One is a bit further away and takes longer to get to you. This doesn’t mean they weren’t released at the same time. The timing just looks different from your point of view.
Ps. The ball is a metaphor for light
There should be an absolute frame of reference.
The universe seems to change its entire structure all at once.
This is why em fields collapse everywhere all at once when its photon particle interacts with something else.
In simple terms: Yes.
Mmm, in simpler terms
The light we see from the stars may be from the past, but seeing the said light is a form of observation.
I think you can state that all objects “exist” right now and that maybe there’s a universal concept of “time” as X arbitrary units away from a beginning point in time.
At this current point in time, stars and planets exist all at the same time X (assuming X is some billion something years from the big bang, if you believe that theory). The light that they emitted reaching our eyes can also be posited to exist as a photon (light particle) in a specific location in space and time.
Just… yeah, the observable universe is very human-bound, and while things exist, it may not necessarily be what you can observe.
The concept of “at the same time” or “simultaneously” doesn’t really work across interstellar distances like you’re used to from normal everyday experiences on earth, because at those scales and the speeds that things tend to move at through space, the amount of time that each end of the distance experiences as having passed is not necessarily the same.
If we observe light emitted from something 4 light-years away, we might say it was emitted 4 years ago, but that’s not necessarily true at the place where the light was emitted from. More or less than 4 years might have passed there since then, depending on how fast whatever emitted emitted the light was moving relative to us, and how much more or less it was affected by gravity. Sure, we like to say that it was emitted 4 of our years ago anyway for our own ease of understanding, but there’s not really anything useful we can do with that information.
Instead, the only thing we can really rely on is that the order that we observe things happening in will be the same order that anyone elsewhere in the universe will observe those same things happening in (assuming faster-than-light travel is impossible). They might experience more or less time happening between the events they observe than we did, but the order will be the same.
Visualize a graph with two axes. One axis shoots upwards, representing speed (or gravity, since they can have equivalent effects). The other axis stretches to the right, representing time.
This graph illustrates your personal perception of time. No matter what, you’ll always feel one second passing as one second. But to an outside observer, your position on this graph dictates how they perceive your passage of time.
Consider this: you’re always moving at the speed of light. But this movement is shared between relative motion (or gravitational effect) and the passage of time.
Imagine you could travel at the exact speed of light (remember, this is just theoretical because mass can’t achieve this speed). All your “movement” is on the speed axis, and to an observer, you’d appear frozen in time, even though they couldn’t technically see you due to your swift motion.
Similarly, near black holes, if you approached one, an observer would see your movement slow until you appeared to freeze at the event horizon. Even though you’ve already crossed inside, the observer would witness your seemingly stationary image gradually redshifting to black.
Conversely, if you could remain entirely motionless, all your “movement” would be dedicated to the time axis. In this state, an observer would see you engaging in activities, like knitting or whatever, at an accelerated pace, but you wouldn’t be moving in space.
There are a few key things to remember:
1. In reality, mass cannot achieve the speed of light; this example was just for illustrative purposes.
2. Absolute stillness in space is impossible. There’s no fixed point to gauge movement against. Everything is in constant motion, everywhere. Hence, it’s impossible to discern if you’re hurtling through space or if space is moving around you. This concept is at the heart of “Relativity”—everything is observed relative to something else. If you’re moving at a constant speed, it feels just like being still.
For most practical purposes, we’re not venturing high up the speed axis; our primary experience is with the passage of time. So, visualize yourself positioned low and to the right on our graph. A GPS satellite, on the other hand, would be a smidge higher and to the left. While you could see it zoom past, an astronaut aboard would experience time just a tiny bit slower than you, though this difference is so minuscule, it’s almost imperceptible.
Hi!
[SpaceTime](https://en.wikipedia.org/wiki/Spacetime) refers to any **mathematical model used to describe** the combination of time and 3D space into one “continuum”
It is about math, and not really ELI5.
With that said:
* we all experience a time we call the present.
* If I am far enough away from something, **it takes a measurable amount of time for the light from that thing to reach me**. For the moon, it is 1.3 seconds for the light to reach me. Almost instant. For the sun it is around 8.3 minutes. For Alpha Centauri it is just over 4 years.
* The present is experienced by me, and all these places, but I can only see light from them at some later time.
Think of it like experiencing things at the same time as others, but then sending them a postal letter that takes time to inform them of what you did.
We are in the same time.
It takes time for notification to reach us.
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