Time Theory in Astrophysics: How Is It Possible?

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Discussion Overview

The discussion revolves around the concept of time in astrophysics, particularly the idea that "all time is happening at one time" and its implications in the context of an expanding universe. Participants explore theoretical frameworks, including imaginary time, and engage in clarifying the meaning of various terms related to time perception and relativity.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants mention the idea that "all time is happening at one time," questioning its feasibility given the universe's expansion.
  • There is a request for credible sources to support the claim regarding time, indicating skepticism about its validity.
  • Imaginary time is introduced as a concept where all time occurs in the present, allowing for movement in different directions through time, although the meaning of "left or right" in this context is debated.
  • One participant suggests that time can be viewed as "NOW" slices, where past, present, and future coexist, leading to the assertion that the past and future may be illusions within space-time.
  • Another participant challenges the notion of "NOW slices," emphasizing constraints on simultaneity and referencing concepts from relativity, such as the relativity of simultaneity and light cones.
  • There is confusion about the terminology used to describe movement through time, with participants questioning the meaning of "left or right" in relation to time.
  • Some participants express a desire to avoid conflating scientific concepts with portrayals in science fiction, indicating a preference for grounded discussions.

Areas of Agreement / Disagreement

Participants exhibit a mix of agreement and disagreement, particularly regarding the interpretation of time and the validity of the "NOW slice" concept. There is no consensus on the meaning of "left or right" in time or the implications of imaginary time.

Contextual Notes

Limitations include varying interpretations of time concepts, dependence on definitions of simultaneity, and unresolved questions about the implications of imaginary time. The discussion reflects a range of perspectives without definitive conclusions.

Hunter Brandon
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I'm new to Astrophysics but some scientists say that all time is happening at one time. How is this possible if the universe is still expanding
 
Astronomy news on Phys.org
What scientists? Do you have a credible source for this claim?
 
The statement "all time is happening at one time" doesn't seem to make any sense. As Chronos asked, please post a reference.
 
Hunter Brandon said:
I'm new to Astrophysics but some scientists say that all time is happening at one time. How is this possible if the universe is still expanding
Are you referring to imaginary time? All imaginary time occurs in the present. If you think of regular time, where you can move forward into the future, or backward into the past, then imaginary time would allow you to move left or right through time, but only in the present.
 
|Glitch| said:
Are you referring to imaginary time? All imaginary time occurs in the present. If you think of regular time, where you can move forward into the future, or backward into the past, then imaginary time would allow you to move left or right through time, but only in the present.
What does "left or right through time" mean ?
 
That is if you consider time as every "NOW" slice; then the PAST, PRESENT and FUTURE exists at any moment. Someone who is, suppose 1 million light years away, just suppose, and is moving towards us / away from us, then THEIR "NOW" slice will be directed at our PAST or FUTURE. Therefore from this you can conclude theoretically that every slice of time is in a "NOW" slice and that the PAST and FUTURE is just an illusion which works within space-time, and everything is in "NOW" or PRESENT state, and including PAST and FUTURE that we believe.
 
phinds said:
What does "left or right through time" mean ?
Something like Interstellar? I admit, I'm equally confused.
 
PWiz said:
Something like Interstellar? I admit, I'm equally confused.
I haven't seen Interstellar, and I don't take my physics from movies so that doesn't clear things up.
 
I think "left or right" as in past and future?
 
  • #10
Shafat Hasan said:
I think "left or right" as in past and future?
No, that's forwards and backwards. I don't think "left and right" has any meaning regarding time, which is why I asked glitch what he means
 
  • #11
phinds said:
I haven't seen Interstellar, and I don't take my physics from movies so that doesn't clear things up.
Yeah, I was just saying that "left" and "right" in time doesn't make much sense to me either (I wasn't asking you to borrow flawed sci-fi physics:P ).
 
  • #12
PWiz said:
Yeah, I was just saying that "left" and "right" in time doesn't make much sense to me either (I wasn't asking you to borrow flawed sci-fi physics:P ).
OK, gotcha.
 
  • #13
Shafat Hasan said:
That is if you consider time as every "NOW" slice; then the PAST, PRESENT and FUTURE exists at any moment. Someone who is, suppose 1 million light years away, just suppose, and is moving towards us / away from us, then THEIR "NOW" slice will be directed at our PAST or FUTURE. Therefore from this you can conclude theoretically that every slice of time is in a "NOW" slice and that the PAST and FUTURE is just an illusion which works within space-time, and everything is in "NOW" or PRESENT state, and including PAST and FUTURE that we believe.

That's not quite right, as there are some constraints on what events can be placed in a space-like surface of simultaneity (what you're calling a "NOW slice"). There are many ways of slicing spacetime up so that unrelated events that are simultaneous to one observer but not another (google for "Einstein train relativity of simultaneity" to see how people moving at different speeds relative to one another have different NOWs) but no way of slicing it up so that an effect can ever precede a cause. If you google or search this forum for phrases like "light cone", "timelike", "spacelike", you'll find much good stuff.
 
  • #14
phinds said:
What does "left or right through time" mean ?
Think of it as moving through different dimensions of time. It is also not a concept from any science fiction movie, but rather based upon Special Relativity and quantum mechanics.

Imaginary Time - Wikipedia

Wikipedia's example describes imaginary time as moving left into the past or right into the future, with imaginary time being up and down (the opposite of what I described), but the point of both our examples is that imaginary time moves perpendicular to regular time and is rooted in the present.
 

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