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Measuring time vs distance

  1. Aug 8, 2011 #1
    I asked this in another thread but I may have been off topic..
    I'm not quite sure which thread to ask in..

    I was wondering if it is okay to say that you can measure an inch in any direction but you can only measure time in one direction. And if, in the same vein, is it okay to say that you can measure an inch from the same point repeatedly but that once you measure time from a point you can't return to that point to remeasure it ever again?

    I was wondering if the above is possibly wrong? I'm just curious what the position is on this?
     
  2. jcsd
  3. Aug 8, 2011 #2

    xts

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    What you say is quite far from precise speech of science, but it makes sense in commong meaning.

    but that once you measure time from a point you can't return to that point to remeasure it ever again?
    You can't travel back in time to repeat the measurement, but you may analyse the historical evidence again.
     
  4. Aug 8, 2011 #3
    Thanks xts. That's cool.

    I also wonder in the same context if we can think about the actual thing being measured in both cases.

    You can measure from one point in space to another point and repeatedly do so and use whatever arbitrary unit of measure say inches. The start point will continue to exist as will the end point and so does the stretch in between continue to exist if we are measuring something.

    For time the point in the past can no longer be measured from and we can't measure to any point in the future until it painstakingly arrives. (Unless we will be able to someday? Or, except as you say as a matter of historical evidence and precedence).

    So if we can measure from a point in space to another and the stretch in-between will still exist to be measured again, but we can't measure from a point in the past to now does that also mean - just as the point in time in the past no longer exists - that the stretch of time between the past and now does not exist because it can't be measured repeatedly to prove its existance?

    Does a stretch of time in the past exist only as evidence would suggest that it did?
    Once the stretch of time passes does it no longer exist anymore?

    Or, does it just not exist only for us because we don't have any way to access it?

    If you can't measure measure something, or access it in any way, by any foreseeable means, then does it exist? I mean we won't be able to access black holes but we all generally believe they exist. But there is some chance that something will encounter the black hole. Is there any chance that anything in existence at this moment (no matter what speed it might be travelling through time relative to us due to GR & SR) will ever be able to get to something in the past?

    Do time periods continue to exist even after they are gone? Can they ever be accessed again? Will they ever be able to be remeasured? Will we ever be able to just step back and remeasure the same time period at will - while still advancing ourselves to know that we are repeating the measurement?
     
  5. Aug 9, 2011 #4

    xts

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    As a positivist I hate ontological argumentation like yours about existing points in space, but non-existing in past. I think your questions are purely ontological or lexical, and the answers may be any you like - they depend on your meaning of the word "existence" and metaphysical taste.

    Points in space you are talking about, are not real things, but rather mathematical constructs we use to describe the World. You can't measure the distance between points. You may measure the size of your desk, or the distance between two ants walking on that desk. Does the distance between two ants measured at some time exist, or not, as ants continue their walk? I won't answer, and I don't think it is a valid question. I know what it means that ants were 4 inches apart at 11:30:15 and 3 inches apart at 11:30:18, and I am able to use such observations in my genuine theory on dynamics of ants. Even if now is 11:39 already.
     
  6. Aug 9, 2011 #5
    What's a positivist? Why the hate?

    I wasn't looking for my own answers. I was looking for the position of science on the questions I have asked.

    In another OPs post the things I am asking for clarity on are used to explain away the OPs question so can not I question the basis of the things that they use? Things should always have an explainable foundation shouldn't they? And, science should always seek to find the foundation shouldn't it especially physics which at its heart is the foundation of all sciences..
     
  7. Aug 9, 2011 #6

    xts

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    What's a positivist?
    http://en.wikipedia.org/wiki/Logical_positivism

    Why the hate?
    Because such argumentation relies on false assumption that all participants have the same clear understanding of the terms used (e.g. "existence"). Even if such terms are clarified and some definition is accepted, people still tend to asociate with them their own (different) intuitions. On the other hand results of the reasoning based on such arguments is rarely testable/falsificable in an empirical way.

    I was looking for the position of science on the questions I have asked.
    Science (in its hard meaning - physics and related sciences) has no position on such questions. Philosophy has, but, as usually in ontology and metaphysics - different philosophers have different opinions, often contradicting each other, and there is no empirical test who is right.

    Things should always have an explainable foundation shouldn't they?
    I agree. Things. The distance between two points is not a 'thing'. It is an artificial mathematical construct we use in our calculations regarding 'things'. I see little sense in assigning such properties like 'existence' to such constructs. We don't need it for any purpose, but it leads us onto minefield of intellectual paradoxes.
     
  8. Aug 9, 2011 #7
    So if two things are a fixed distance apart that is not a scientific fact? Then most of science must be an artificial mathematical construct.

    Are you suggesting that we should not bother with string theory simply because it is an artificial mathematical construct and doesn't even have any empirical testable evidence.

    At least the distance between the two points in question can be empirically tested again and again whereas we rely purely on historical memories and notes and cause and effect to validate the occurrence of previous periods of time. There is no way (presently) to retrieve those periods firsthand to recheck them. Hence why we have so much fun when it comes to trying to reconstruct the past.

    Even dimensions are an artificial mathematical construct. The universe doesn't align along three axes. It aligns to all sorts of angles. We simply set up an arbitrary grid and measure out co-ordinates from that. The dimensions don't even have to be perpendicular. You can get to any place on the Earth via and longitude, latitude and altitude. Without math you don't have science..

    Science is pretty much our artificial mathematical construct of the universe isn't it?
     
  9. Aug 9, 2011 #8

    xts

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    So if two things are a fixed distance apart that is not a scientific fact?
    It is (with respect of some idealisation, as no objects are really fixed). But in order to cope with such facts we don't need to speak about 'existence of distance'. We need good methodology to measure it and theoretical models able to calculate it.

    Then most of science must be an artificial mathematical construct....Without math you don't have science.
    Actually, it is! I fully agree.

    Are you suggesting that we should not bother with string theory simply because it is an artificial mathematical construct and doesn't even have any empirical testable evidence.
    Exactly! I fully agree with Peter Woit and his book "Not even wrong".
    There is however some difference between ST and metaphysics. String Theory may eventually have some empirical meaning, while 'existence of past points' is just meaningless. Strings have some predictions, just being very far beyond technical possibilities. Ontological claims are fundamentally non-falsifiable.

    At least the distance between the two points in question can be empirically tested again and again
    No. You have no methodology to measure distance between points. You may measure distance between corners of your desk. Or between ants. As the size of the desk is practically stable, every measurement of the distance between ants gives different result. It doesn't invalidate measurements and we may successfully use the results even if there is no way to repeat the measurement. Actually, in Quantum Mechanics no measurement is repeatable. But for this dispute - example of ants walking on the table is sufficient.
     
  10. Aug 9, 2011 #9
    'May'? OMG!

    Well I don't really have time for this anyway unfortunately so I shall leave you in peace.
    Sadly I shall remain unanswered.
    You win with your convoluted argument! Respect. You will go far.

    Ciao.
     
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