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What is time exactly

by kateman
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Shooting Star
#19
Jan11-08, 12:28 PM
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Quote Quote by DaveC426913 View Post
We can't really know that traveling backwards in time is impossible until we know what time is.
Why not? We may hit upon it by accident. Do we have to understand what goes on in our bodies to live?

Quote Quote by kateman View Post
well more assuming its probable, but not for living beings. more or less for particles instead.
Why so?

I've heard many people say that time dilation is valid for atomic time, not for biological time, whatever that means. They simply cannot accept the fact that humans may age at different rates.
Troels
#20
Jan11-08, 01:11 PM
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The British Science writer Michael Hanlon has made som very interesting comments on this question in his book "10 questions science can't answer (yet)"
DLuckyE
#21
Jan11-08, 01:20 PM
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Quote Quote by dbecker215 View Post
The idea of time being used for calculations was embedded by Newton. But he believed in a constant time, one that he derived from his theological beliefs. This was an assumption that lasted until Einstein who threw relativity at the concept of time into the picture. This where the possibility of time travel comes into play. This is another area where science meets philosophy b/c it raises the paradoxical question of if you go back in time can you kill your grandfather and therefore not exist? I personally don't think so but there is yet to be scientific or mathematical evidence for why you can't.
If time is nothing more than a 'layer' of the current spacial state of the universe then it wouldn't matter if traveling back in time was possible. Since it'd be just like rewinding a tape, everything goes backward, and same things happens again going forward. Actually then nobody would even notice time was going backwards...

For all we know time goes back & forth all the time ;)

But then again, if that was true, time dilation wouldn't make any sense...

Just ignore me, I'm rambling, but still to me a 'static' universe seems to be the most logical even though that would mean free will is just something our mind makes us believe we have ;)
nanoWatt
#22
Jan11-08, 01:45 PM
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Quote Quote by dbecker215 View Post
One of the big questions about time that must be figured out is whether time can be measured in static blocks, because we can't currently measure units time to a high enough accuracy this question is left to theorists and tends to border science and philosophy. Some believe that time is the sequence or transition of these static events.
Isn't this the same as trying to quantize time?
Kurdt
#23
Jan11-08, 02:13 PM
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Philosophically a theory of time is unresolved. Most philosophers agree that time does exist but they haven't yet been able to determine what it exactly is. Most of what is known comes from the use of time in well established physical theories such as QM and GR and the nature of time is explored by looking at what these theories demand of the time variable. Perhaps it would suffice to say that time is a set of relations between events.

Here is a good article you may like to read.

http://www.iep.utm.edu/t/time.htm#H3
dbecker215
#24
Jan12-08, 12:44 AM
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That was a good article, thanx. A lot of philosophy for one night though...

It's easy to see why time is still unresolved when so many won't even come to a common ground when trying to discuss possibilities. Philosophy's endless circles are daunting.
Shooting Star
#25
Jan12-08, 12:57 AM
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Clever old A.E. cut through the gordian knot by saying, "Time is what you measure with a clock...". It turned to be quite fruitful, too.
lightarrow
#26
Jan12-08, 05:29 AM
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Quote Quote by Shooting star View Post
Clever old A.E. cut through the gordian knot by saying, "Time is what you measure with a clock...". It turned to be quite fruitful, too.
So, I could use any clock, for example a sand glass? I don't think that's a good way to answer (infact he knew that was not an answer).
Jonathan Scott
#27
Jan12-08, 07:09 AM
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Quote Quote by lightarrow View Post
So, I could use any clock, for example a sand glass? I don't think that's a good way to answer (infact he knew that was not an answer).
A sand glass isn't a self-contained clock on its own, but a sand glass combined with a suitable planet to complete the mechanism would work as a clock for that purpose.
Kurdt
#28
Jan12-08, 07:25 AM
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I think what Einstein omitted from that quote was the word ideal or accurate.
lightarrow
#29
Jan12-08, 07:58 AM
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Quote Quote by Jonathan Scott View Post
A sand glass isn't a self-contained clock on its own, but a sand glass combined with a suitable planet to complete the mechanism would work as a clock for that purpose.
Absolutely
lightarrow
#30
Jan12-08, 08:00 AM
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Quote Quote by Kurdt View Post
I think what Einstein omitted from that quote was the word ideal or accurate.
And how do you establish if a clock is more accurate than another if you still have to define what time is?
Shooting Star
#31
Jan12-08, 08:44 AM
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Quote Quote by lightarrow View Post
So, I could use any clock, for example a sand glass? I don't think that's a good way to answer (infact he knew that was not an answer).
Even I know that's not the answer, taken literally. But if you think about it, since we don't know much about time, this utilitarian approach is the best perhaps.

Quote Quote by Jonathan Scott View Post
A sand glass isn't a self-contained clock on its own, but a sand glass combined with a suitable planet to complete the mechanism would work as a clock for that purpose.
Sand glasses or pendulum clocks or anything which works on gravity is inadmissible as a clock in GR.

After many years of research, we have come to the consensus that atomic (or maybe subatomic) vibrations keep the best time. That's why we use those phenomena to measure time; or has it simply become a matter of definition that those keep the right time?
InfinateLoop
#32
Jan12-08, 12:35 PM
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I thought time was successive intervals?
How does that not sum everything up?
Is it because of GR?

I love this topic!
Rade
#33
Jan12-08, 12:38 PM
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Quote Quote by Kurdt View Post
... Most philosophers agree that time does exist but they haven't yet been able to determine what it exactly is....
According to Aristotle, Physica, Book VI, he claims the following about time:
...time is (number of motion of a physical thing that is counted) that is intermediate between indivisible moments...

Suppose three moments, A, B, C and a physical thing {T} in motion in "space" in relation to them. From my understanding of Aristotle, the moments are indivisible and have neither motion nor rest, thus they are outside of time, yet they are the limits of past and future time, such that:
the past ~ ---- time 1 ----> |A|--- time 2 -{T}--> |B| ------- time 3 ---{T}----> |C| ---- ~ the future

In the above diagram consider the relationship of time 2 & 3 to moment |B|. There exists infinite numbers of motions of the thing {T} in space that can be counted in time #2 leading to |B| (the past) and in time #3 leading away from |B| (the future) and these motions that can be counted are "time". Thus, moment |B| is both a limit of past time (time#2) and future time (time #3), and while it can be said that |B| is in this sense, as a limit, a part of time, there is no time within the moment|B|, since time is always divisible while |B|, because it is a moment, is always indivisible. And see that while time #2 is the past of moment |B|yet also is time#2 within the future of moment |A|.

Thus, as the concepts "odd" and "even" are within number, so the concepts "past" and "present" and "future" (moments) are within any time. So, time will never fail to exist if there is motion of a thing in space that exists, for where there is motion, there is always a beginning to time.

Now, Aristotle also holds "space" = "that which is intermediate between existents". Thus, it is possible to suggest that Aristotle would claim that;
"space-time" = that which is intermediate between moments of existents.

Applying the above diagram, suppose two existents {E1} and {E2}, and they are in motion at two different moments |A'| and |B'| in space-time:

the past ~ ---- time 1 ----> |A|--- time 2 -{E1|A'|}--> |B| ------- time 3 ---{E2|B'|}----> |C| ---- ~ the future

So, here we see that "space-time" is that which is intermediate between {E1|A'|} and {E2|B'|} as these two existents relate to the three moments A, B, C and their respective concepts of past and future time.

This is my understanding of what Aristotle may claim about the philosophic question..."what is time" as relates to physical things that exist that follow the laws of nature.
pervect
#34
Jan12-08, 01:55 PM
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OK, given that we are now talking about Aristotle, and given the title of the topic, I think it's time (probably past time) that I move this to the philosophy forum.
Shooting Star
#35
Jan12-08, 02:47 PM
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I was about to suggest to a mentor to lock the thread, but you, being the expert, have taken better care of it. A bit rough on Aristotle, who, by the standards of his day and two millennia after, is considered to be one of the greatest minds in recorded history.
Kurdt
#36
Jan12-08, 02:47 PM
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I think in summary then Rade, Aristotle would consider time as the interval between events. Its interesting his use of the term indivisible moments. Does this imply Aristotle thought there was a minimum 'duration' (i.e. interval between events) in which one could not have any smaller duration. In essence a quantum theory of time.


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