Time Moves Forward for Obvious Reason?


by PMichaud
Tags: big bang, direction of time, time
bobc2
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#19
Jan31-12, 10:07 AM
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Quote Quote by DaveC426913 View Post
Not a medium, a dimension. You agree that things move through space, yes?
Please don't think I'm trying to be argumentative, DaveC426913, because I always appreciate your posts. Yes, I agree things move through space.

Are you intending to imply that things move through a spatial 4th dimension? Or did you mean that things move through the 4th dimension, but the 4th dimension is time, and time somehow has a property analagous to space through which things move--that is, time is some kind of medium in a sense (perhaps not capable of description)?
nitsuj
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#20
Jan31-12, 10:55 AM
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Quote Quote by bobc2 View Post
time somehow has a property analagous to space through which things move--
Wouldn't that be putting the carrige before the horse bobc2?
bobc2
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#21
Jan31-12, 11:08 AM
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Quote Quote by nitsuj View Post
Wouldn't that be putting the carrige before the horse bobc2?
Always good to have your input, nitsuj. I wasn't intending to propose a concept--just trying to understand the thinking behind what DaveC426913 was saying.
DaveC426913
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#22
Jan31-12, 12:59 PM
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Quote Quote by bobc2 View Post
Please don't think I'm trying to be argumentative, DaveC426913,
Hardly. It's a good discussion.

Quote Quote by bobc2 View Post
Are you intending to imply that things move through a spatial 4th dimension?
No.
Quote Quote by bobc2 View Post
Or did you mean that things move through the 4th dimension, but the 4th dimension is time,
Yes.
Quote Quote by bobc2 View Post
and time somehow has a property analagous to space through which things move-
Redundant. As a dimension, physical objects move through it.
Quote Quote by bobc2 View Post
-that is, time is some kind of medium in a sense (perhaps not capable of description)?
No. No medium.

Simply that one can identify its location in that dimension with a coordinate, and can measure changes of that object in that dimension by observing a change in its coordinate.
(i.e. t=1 becomes t=2).
bobc2
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#23
Jan31-12, 01:38 PM
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Quote Quote by DaveC426913 View Post
Hardly. It's a good discussion.

No.

Yes.
Redundant. As a dimension, physical objects move through it.

No. No medium.

Simply that one can identify its location in that dimension with a coordinate, and can measure changes of that object in that dimension by observing a change in its coordinate.
(i.e. t=1 becomes t=2).
Thanks for the clarification, DaveC426913.
nitsuj
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#24
Jan31-12, 01:58 PM
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Quote Quote by DaveC426913 View Post
Simply that one can identify its location in that dimension with a coordinate, and can measure changes of that object in that dimension by observing a change in its coordinate.
(i.e. t=1 becomes t=2).
That is simply put, well said DaveC426913.
zonde
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#25
Jan31-12, 11:43 PM
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Quote Quote by bahamagreen View Post
If you took a particular snapshot 4 hours after opening the bottle and reversed all the molecules, you would see the molecules all back in the bottle after four hours...


I know... the thought experiment implies lots of simplifications and assumptions.
But the point was to see that there are configurations that do lead to all of them back in the bottle - in the thought experiment the symmetric reversal of any snapshot after opening the bottle is just a way of noticing that every possible reversed snapshot throughout the remaining history of the universe after opening the bottle IS one of those snapshots that gets them back in the bottle.
If you drop the assumptions about determinism, uncertainty, and include everything (like the black body radiation, neutrino and cosmic alpha bombardment, tidal effects, the vibration of the walls etc.) you STILL have snapshots that will result in getting it all back in the bottle - those that DO include every possible influence. The symmetry reversal of getting out and getting in to the bottle was just a means of seeing this.
For example, even if you did include all effects and influences, if you observed all of it getting back into the bottle... then you could reverse those historical paths from there and they would include any and all effects and influences back to the time of opening the bottle (long time) within which would be an infinite collections of snapshots that when reversed would get to the bottle refilled result.
If you declare that you reverse everything then this thought experiment is not very interesting.
But I think it is interesting from perspective where we try to specify what are the things that we should change (invert) to get time reversed. So I am saying that reversal of motion of massive particles is not enough. And if you include electromagnetic radiation (considered systems are actually open not closed) then what is left of this entropy thing?
sahmgeek
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#26
Feb1-12, 02:12 PM
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I've been chewing on the concept of time for awhile and the best i can come up with is:

time = perceived "change" (I suppose this happens in "space") = entropy (in physics land)

if this is worthy of lockdown (or whatever you call it) I am happy to toss in an equation or something.
DaveC426913
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#27
Feb1-12, 05:11 PM
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Quote Quote by sahmgeek View Post
if this is worthy of lockdown (or whatever you call it) I am happy to toss in an equation or something.
I'm not sure if you meant that humorously but that's funny!

Can I steal it?
sahmgeek
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#28
Feb1-12, 06:12 PM
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Given my math skills at this point in time, it's extremely humorous. thank physics for change!
Passionflower
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#29
Feb1-12, 09:08 PM
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Another observation about time that some may have an interest in:

One can only count events not measure their duration because a duration is defined as a counted number of events.
bobc2
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#30
Feb1-12, 09:29 PM
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Quote Quote by Passionflower View Post
Another observation about time that some may have an interest in:

One can only count events not measure their duration because a duration is defined as a counted number of events.
That's very interesting, Passionflower. And events are only observed as spatial 4-dimensional events located on 4-dimensional objects (such as various types of clock objects).
DaveC426913
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#31
Feb1-12, 09:34 PM
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Quote Quote by Passionflower View Post
One can only count events not measure their duration because a duration is defined as a counted number of events.
I'm not sure I follow.

Just because a duration is defined as a counted number of events, how does that mean we can't measure their duration?

Say I wanted to measure the duration of the lifetime of a neutron, from its creation to its decay. I count two events. But I could compare the duration between those two events with the lifetimes of a dozen other neutrons doing the same thing.
Islam Hassan
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#32
Feb2-12, 06:01 AM
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Quote Quote by Passionflower View Post
Another observation about time that some may have an interest in:

One can only count events not measure their duration because a duration is defined as a counted number of events.
Perhaps at an arithmetical level, but then if we make these events infinitely small, don't we tend towards a smooth, continous definition of time? I take it that we can measure time in such a manner that it is not granular.

IH
nitsuj
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#33
Feb2-12, 06:23 AM
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Quote Quote by Passionflower View Post
Another observation about time that some may have an interest in:

One can only count events not measure their duration because a duration is defined as a counted number of events.
Wasn't it Wheeler that said time is what keeps everything from happening at once lol?

From the context I think your speaking from, can't the same comment be said of length.
DaveC426913
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#34
Feb2-12, 08:21 AM
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Quote Quote by Islam Hassan View Post
Perhaps at an arithmetical level, but then if we make these events infinitely small, don't we tend towards a smooth, continous definition of time? I take it that we can measure time in such a manner that it is not granular.

IH
The lower limit is the Planck time: ~10-43 second.
Islam Hassan
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#35
Feb2-12, 08:31 AM
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Quote Quote by DaveC426913 View Post
The lower limit is the Planck time: ~10-43 second.
I wonder is the lower limit of Planck time a proposition which may be subject to experimental proof? If not, if it's a universal "given", then Passionflower's comment has some substance to it...

IH
petm1
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#36
Feb6-12, 03:53 PM
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Quote Quote by DaveC426913 View Post
Say I wanted to measure the duration of the lifetime of a neutron, from its creation to its decay. I count two events. But I could compare the duration between those two events with the lifetimes of a dozen other neutrons doing the same thing.
Using this same thought for the duration of a particle’s lifetime, how about a photon, because this is a simple way to describe what I "see" as space? As for duration it is always the common denominator you can count as one.


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