I’m trying to wrap my head around this. I perceive time as though the present moment is a wave I’m riding through space and experience. Does Spacetime, as presently understood, suggest that time is more likely an ocean that exists and is “real” stretching off towards the horizons? In other words, is the present the only thing that is real as we traverse the dimension of time? Or do the distant past and future also exist, despite my inability to experience them, just as distant points in space do?
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The past and future exist relative to your current place in space and time. Your specific version of time, relative to you, is all you’ll ever experience. You cannot travel time in the sense that you can visit your own past or future, but you can visit someone else’s future, but that will still be your present.
Think of time and space as two fabrics interwoven. Different, yet effecting each other.
Time is tracked via movement in space over a period. Originally our own orbit around the sun, now the vibrations of a specific isotope of Cesium atom.
Movement is tracked as a change in position over time. You move from point a to point b and it takes “time” to get there.
One cannot quite exist without the other, yet, they are distinct.
Spacetime then is a term much like “electromagnetic” in which it refers to the points where each are affected and act as one thing. For instance, gravity causes or is caused by distortions in spacetime.
Changes in gravity will make time run differently and applies accelleration to objects in space. Since it effects space and time, we lump them together into “spacetime!”
As for the existance of time in the future and in the past… the short answer is yes, maybe. It is theorized that all possible futures exist and you merely collapse into the observed future upon making a choice or observation etc. A part of many multiverse theories and I think touching most on “stringʾ theory. “
Yes, space and time are equal dimensions in our universe. What we don’t have are processes that go “back” in time. In the three spacial dimensions have processes that allow you to choose to go either way.
When you want to find something, you must know its position with respect to all three spacial coordinates, but also time. Time is like a fourth direction things can move in, but one in which, for as of now uknown reasons, we are only able to move one way. Never the other, though it can be distorted and dilated by gravitational fields just like the other spacial dimensions.
Using the word “simultaneously” here is tricky because by its very definition it invokes time. When two things happen simultaneously, they are happening at the same time. Naturally if two things are separated by time, lets say past and future relative to us, they cannot be simultaneous.
It’s easier to understand if we extrapolate to a spacial dimension. Imagine some random direction axis and two objects placed on it, so that they are not in the same place. This axis represents time, and the two objects exist at different times. To say they exist simultaneously would be to say they occupy the same place on that axis, but we can clearly see they do not.
No, because simultaneously means “at the same time”. You might as well ask if two simultaneous events opposite sides of the world are happening in the same place.
Similarly, “exist” is a present tense verb. The past existed, the present exists, the future will exist.
You know e=mc^2 ?
c really represents the speed of causality. Light is the only known thing that travels through the space part of spacetime at the speed of causality, so c is pretty much just called ‘the speed of light’. But everything moves through spacetime at the speed of causality. It’s just for us, we travel very slowly through space, and so the rest of that speed is spent traveling through time.
That’s why, in examples describing relativity, an object moving close to the speed of light has time slowed down- since it’s approaching the speed of causality in space, it’s speed through time slows. Because nothing can exceed the speed of causality in spacetime.
Thanks for the thoughtful and helpful answers! I think I have a better understanding that we can see backwards in time, but only travel forwards. And the opposite, to the best of our understanding, is not possible. That makes perfect sense, but the conceptual and semantic challenges are a lot for my tiny primate brain to grasp. Thanks everyone for taking the time to reply!
[That is one interpretation](https://en.wikipedia.org/wiki/B-theory_of_time), yes. But there’s no widely held consensus about whether it’s actually correct or not.
I don’t know enough to say how it’s different than the general theory of space time, but the specific idea you’re referring to is block universe. That more specific term might be helpful in finding more info.
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