What's the difference between Proper time and Coordinate time

  • #1
I was reading up on the nature of time and found this: "
In one sense, "time" is the time that is in the equations of physics. That's the t in the equations of the paper, it's the parameter that describes how the states of all systems in the universe change."
Does this explain coordinate time?

And this:
"However, actual measurements from within the universe cannot measure "t". All they can do is look at the correlation between the state of one thing - say, the hands of a clock - and the state of another thing - say, the conditions of a chemical reaction. So when we actually measure time, what we're measuring is these correlations."
Does this explain proper time?

If not, what are the difference between them, in layman's terms?
 

Answers and Replies

  • #2
PeterDonis
Mentor
Insights Author
2020 Award
32,949
11,438
I was reading up on the nature of time
Where? Please give a specific reference. We can't discuss out of context quotes from an unknown source.
 
  • #3
Where? Please give a specific reference. We can't discuss out of context quotes from an unknown source.
It was on physics stack exchange, I asked about the nature of time and that was their answer, are they describing coordinate time and proper time, or are they wrong?
 
  • #4
PeterDonis
Mentor
Insights Author
2020 Award
32,949
11,438
It was on physics stack exchange
Which page? Give a link.

I asked about the nature of time and that was their answer, are they describing coordinate time and proper time, or are they wrong?
Again: we cannot discuss out of context quotes from an unknown source. Either give a specific link to the actual discussion you're asking about or this thread will be closed.
 
  • #6
PeterDonis
Mentor
Insights Author
2020 Award
32,949
11,438
what are the difference between them, in layman's terms?
Coordinate time is a coordinate label that you put on events in spacetime (more precisely, one of four coordinate labels that you put on each event, assuming you are using appropriate coordinates).

Proper time is the time elapsed on a clock between two events on the clock's worldline.
 
  • #7
Ibix
Science Advisor
Insights Author
2020 Award
7,397
6,483
Proper time is the "distance" along a timelike worldline. If you arrange a set of parallel inertial (i.e. straight) timelike worldlines, this is one direction of a grid. If you agree a zero on all of the lines (preferably so that the zeros form a line orthogonal to each timelike line) then you have coordinate time.

It's exactly like the distinction between the length of any old line and the length along a set of parallel straight lines (which you'd call a y-coordinate) in Euclidean geometry.
 
  • Like
Likes Cryo
  • #8
PeterDonis
Mentor
Insights Author
2020 Award
32,949
11,438
Then what is the person who replied talking about?
Not coordinate time or proper time. So if you were hoping to get information about what those are, that StackExchange thread is not the way to do it--nor is the paper linked to there.

The experiment wants to show that time emerges from quantum entanglement, he states only measured time is, and parametric time isn't, what is he talking about?
In quantum mechanics (more precisely, non-relativistic QM), the time ##t## is a parameter; the state of the overall quantum system is a function of this parameter, but the parameter is just imposed by the theory, it has nothing to do with anything that's measured or anything physical.

"Measured time" in the paper is the change in the correlations between the subsystems of the overall quantum system as measurements are made on them, interpreted as evidence of "time flowing", as part of a proposal made by the authors of the paper on how we, as individual subsystems in the universe, could perceive time to be flowing (or, to put it another way, things to be changing), when, if you try to apply non-relativistic QM to the whole universe and assign the whole universe a quantum state, the Hamiltonian you get out of it says the state of the whole universe never changes at all as a function of the parameter ##t##.

As above, none of this has anything to do with either coordinate time or proper time as those concepts are used in relativity. A discussion of the paper and the StackExchange thread really belongs in the QM forum, not here, if that's what you want to ask about. But such a discussion has nothing to do with coordinate time or proper time.
 

Related Threads on What's the difference between Proper time and Coordinate time

Replies
23
Views
2K
Replies
78
Views
9K
  • Last Post
2
Replies
26
Views
18K
Replies
45
Views
2K
  • Last Post
Replies
1
Views
2K
Replies
6
Views
2K
Replies
42
Views
2K
Replies
330
Views
18K
  • Last Post
Replies
22
Views
1K
Top