Why Does Time Expand? Spacetime Explained

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Discussion Overview

The discussion revolves around the nature of time, particularly the concept of time "expanding" or "flowing" into the future, and its relationship to spacetime and change. Participants explore philosophical and scientific perspectives on why time seems to progress and whether it can be compared to the expansion of space.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification
  • Philosophical

Main Points Raised

  • Some participants question why we perceive ourselves as constantly traveling into the future, suggesting this might imply an expansion of spacetime.
  • Others argue that a given spacetime does not change under General Relativity, challenging the notion of time expansion.
  • A participant suggests that the term "flow" may be more appropriate than "expansion" when discussing time, while acknowledging that this topic may lean towards philosophical inquiry.
  • There is a discussion about the nature of time as a mental representation of change, with one participant asserting that the question of why change occurs is inherently circular and thus meaningless.
  • Another participant introduces the concept of the "arrow of time," linking it to symmetry breaking at the Big Bang, although this is not universally accepted in the discussion.

Areas of Agreement / Disagreement

Participants express differing views on whether time can be considered to expand or flow, with no consensus reached on the terminology or the underlying reasons for the progression of time. The discussion remains unresolved, with multiple competing perspectives presented.

Contextual Notes

Some arguments rely on philosophical interpretations of time and change, while others attempt to ground the discussion in physical theories. The lack of consensus on definitions and the nature of time contributes to the complexity of the discussion.

epkid08
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Why are we constantly traveling into the future? Doesn't this suggest that not only space is expanding, but spacetime is expanding as a whole?
 
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epkid08 said:
Why are we constantly traveling into the future? Doesn't this suggest that not only space is expanding, but spacetime is expanding as a whole?
No it does not. A given spacetime does not change under GR.
 
That wasn't my question. Why are we constantly traveling into the future?
 
epkid08 said:
That wasn't my question. Why are we constantly traveling into the future?
Perhaps such a "why" question is better asked in the philosophy section of the forum.

At any rate this has nothing to do with "expansion" of time.
 
I used the word expansion to describe the motion of time moving into the future; There has to be some accepted theory of why time continues to expand, isn't there?
 
Just choosing to use the word doesn't make it right - it isn't an arbitrary choice. You suggested a comparison to the expansion of space. That's not a valid comparison. Time doesn't expand. A better word is flow. Time flows. Why? Dunno. As said, that may just be a matter of philosophy.
 
Flow sounds right because its been used in the context of describing time before. You could just as well describe the movement of time as expanding. (You're not thinking of it in the right way anyways, but that's not the point)

It's hard to believe that there are no theories on this, considering all of the other theories out there; In reality it's not a matter of philosophy.
 
I'm moving this to philosophy, since the topic is not related to Cosmology. You might want to have a read of, say, The River of Time by Igor Novikov: it's quite a good book on the nature of time.
 
Time is a mental representation of change; some say that time is a "measurement" of change. The complete absence of any change anywhere in the universe would mean no time, so a more fundamental question is: why does change happen?

The question "why" asks for a cause. But if a cause for change ever existed then it would be the cause for a change from the universe going from a state of "no change" into a state of "some change". Of course, this would already be a change, so the cause would not really be a cause of change since such a change is already assumed in the question. This circular assumption invalidates the question. A cause of change cannot be stated, so a cause for time cannot be given either. The question simply does not apply to change (and time).

See a similar discussion about https://www.physicsforums.com/showthread.php?t=171193" Asking for the cause of existence asumes that such a cause could exist already, which makes this question meaningless as well. Existence and change are both undeniable and "why-proof" realities.
 
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epkid08 said:
Why are we constantly traveling into the future? Doesn't this suggest that not only space is expanding, but spacetime is expanding as a whole?

What you are referring to is the "arrow of time".

Acc. to some physicists this is caused by the breakdown of a symmetrie which happened at the big bang.
 

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