All Questions
22
questions
1
vote
2
answers
71
views
How do I interpret the time axis in a diagram with multiple light cones?
Light cones are often drawn on a spacetime diagram that has a directional time axis like the fourth one on this page:
There is a time axis, and all of the light cones are align with it because this ...
- 113
-1
votes
1
answer
55
views
Since we observe stars, galaxies, etc in their past - is it correct to say that our present is only present for us but is in the past from afar? [closed]
So - I know that when we observe galaxies, we are observing their past. And that if the same past-them were to be looking at us, they would see our past. But when we look at their past - that is a ...
1
vote
1
answer
111
views
Topology of Time
I came across the concept of topology of time and causality in Reichenbach book, "Philosophy of Space and Time". It would be nice to have list of references of recent developments of the ...
0
votes
1
answer
114
views
Why is causal order not related to directionality of time?
Hans Reichenbach argues for the causality and causal chain to define a topological coordinative definition of time order. Here is an excerpt from his textbook, The Philosophy of Space and Time, Dover(...
- 625
1
vote
2
answers
107
views
Temporal Ordering in Special Relativity [duplicate]
Not a physicist: but want to use the temporal ordering of events in special relativity as an example for something, and need to answer the following question to do so.
Suppose we have three events, a, ...
- 11
1
vote
0
answers
90
views
Any problem creating a global time function given known spacetime topology?
Gödel says the absence of a global time function
seems to imply an absurdity. For it enables one e.g., to travel into the near past of those places where he has himself
lived.
But is it not true ...
- 383
1
vote
0
answers
73
views
Should time be a loop or a line?
It's interesting to see that torus was so popular in physics, that it worked so well. There was famous Gauss–Bonnet theorem which stated basically
$$\oint_S K dS= 2\pi \chi(S)$$
where K was the ...
- 3,256
1
vote
1
answer
85
views
How to describe ‘when’ a black hole actually is? [closed]
If I look at any point in space I can think of it as being in the future because it takes me time to travel there. I can go there and an observer can watch me go there.
When I look at a black hole I ...
- 740
1
vote
1
answer
101
views
Does general relativity predict that it's possible to watch a process playing backwards?
My question is
Let's say you have an object moving through space locally at less than the speed of light. Is it possible to watch that object playing backwards like a record spinning the wrong ...
- 1,668
6
votes
6
answers
1k
views
What is the role of the laws of physics in a block universe?
Definition of a block universe - The idea that the whole universe exists simultaneously and time doesn’t flow.
For those who favor this kind of theory (the few of you), what is the role of the laws of ...
- 187
0
votes
2
answers
583
views
Special Relativity can my past be in someone's future
My question is the following:
Is it possible that an event which is in my past light cone is currently in another observer's future light cone?
(i.e. for an observer sitting at a point in the set of ...
- 46
0
votes
2
answers
73
views
Is space and time consecutive in physics, like frames in cameras? [duplicate]
Is time consecutive in physics? Here is my deeper explanation of what I mean.
Are frames for example in a camera a good metaphor with the concept that time also has "frames" in the space of ...
- 3
-4
votes
1
answer
380
views
Aging while traveling faster than speed of light? [closed]
theoretically, if organic matter was able to travel faster than the speed of light, without becoming "pure energy", and since theoretically traveling faster then the speed of light would travel ...
1
vote
1
answer
185
views
Chronology protection: current status
I am looking for some fresh references on the Chronology Protection Conjecture. I am aware of this question, but the answer there seems to resort to energy conditions.
But, weren't they shown violated ...
- 204
0
votes
1
answer
150
views
How does going faster than light cause going backward in time? [duplicate]
I have read in many places that some virtual particles can "travel faster than light (1)" and thereby "go backwards in time (2)".
My question is about the connection between these two. I have always ...
- 171