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Relativity of unit of measurement

  1. May 16, 2003 #1
    Einstein's theory of relativity was all about the relativity of measurement.

    I will present here an extention to this idea, the relativity of unit of measurement.

    At first, anyone agrees that the laws of physics don't change one bit, if we would use one day instead of the meter stick any other unit of length. This is a very profound principle of physics.

    At first this looks rather trivial. Nature does not have preferred units of measurement, so all choices for units are more or less arbitrary.

    The outcome of General Relativity was that we need to think of the cosmos as expanding.

    Suppose now, we would choose a unit of length, that was exactly proportional to the expansion of space. So, in other words, in this new measuring unit system, the expansion of space would not be a known phenomena. Since speed of light still is constant, this would also mean we need to have a new time unit. In this new time unit we have to adopt the idea that the age of the universe is infinite.

    It is clear then that in more then one way, we have a new phyics, just be choosing a new measuring unit of length, and changing other units of measurement accordingly!
    Physical phenomena would not be the same. The expansion of space would be an unknown phenomena. On the other hand a new phenomena would occur, the contraction of all material forms (from galaxies to atoms and below).

    Does this change of physical behaviour mean that Nature does have a preferred set of measuring units?

    Is the physics of the new measuring units an - although different - but still valid form of physcis?

    If so, what would these new physcis laws be like?
  2. jcsd
  3. May 16, 2003 #2
    That would be not a unit of length, but a unit of speed.
  4. May 16, 2003 #3
    Re: Re: Relativity of unit of measurement

    The new unit of length would be expanding when measured in the old units of length and time.

    But in the new measuring unit system, it would of course not be expanding.

    I know we are too much used to the old measuring unit system to be able to drop it in an easy way. Because it feels like measuring in plain empty space, where no measurements can be made...

    But please describe me then in the old measuring unit system what you mean with "expansion of space"... This is an equal ridiculous concept, cause only "things in space" i.e. material objects can be said to shrink or expand, not space itself.
  5. May 16, 2003 #4
    Material objects are made of atoms (and other particles), and neither size of atom nor distance between atoms depend on space. "Size" of atom is nothing else but a strength of e/m force between proton and electron. Thus, it only depends on such things as two fundamental constants: speed of light c and Plank constant h.

    As long as these constants stay put, atom sizes and interatomic distances (say in meter stick) stay put too.
  6. May 16, 2003 #5
    Heu - ya totally messed your idea up. It's a good idea but poorly explained. Try to sum it up shorter and don't mistake length for acceleration or time or speed. Then I will commmend you on a neat idea, and post my thoughts.
  7. May 17, 2003 #6
    How did we find these constants? Yes! They have been measured and are explained in terms of certain basic units of measurements.
    I would agree that lightspeed c would stay the same, but a value of h could be dependend on other things, i.e. it would no longer be a constant. But on earth we have no way of meausuring any difference in h.
  8. May 17, 2003 #7
    We are not limited by Earth. We have telescopes.
  9. May 17, 2003 #8
    Yes, but the change in metrics due to the space expansion is too little to be measured directly (we don't measure an increase in distance to far away galaxies, only the redshift).
  10. May 18, 2003 #9
    What do you mean? In telescopes we see atoms to be of the same size in faraway galaxies as atoms here on Earth.
  11. May 18, 2003 #10
    Yes. And? This does not contradict with anything here, cause you use the normal units of measurement, so how could you expect any difference?

    Nevertheless, when reasoned from this new system of measuring units, we are entitled to conclude that atoms shrink in size in the course of time. Even when this sounds absurd, it's a viable conclusion.
    It's ass relative as claiming that an object is at rest, while all others objects are moving.

    However, when reasoning from this new measuring unit system, we have in fact to built up a whole new physics, which is in many ways different compared to the one we are used. How to explain for instance that atoms shrink in size?
  12. May 19, 2003 #11
    Physics will not be differet, just reference system will be different.

    And what is unusual about shrinking sizes of everything if the system of reference unit is expanding?

    You are asking the following question: "-Look at this distant quazar which is moving away from us at speed 0.999c. But what if we pick quazar's system of reference? Everything will be different then ! We will be moving at the speed -0.999c !! Whoa !!! Whole new physics on Earth!!!!"

    Really? I don't see any measurable difference between these "two physics". Do you? If so, then what is the difference?
  13. May 19, 2003 #12
    The physical world as such, is indifferent to our choice of measuring units. But physical law deal with physical phenomena.
    Now the expansion of the universe is a physical phenomena in one system of measuring units, while it is not a physical phenomena in the alternative system of measuring units. Same for the shrinking of matter.
    I mean, the physical explenations are different, although they all relend on the same, and indifferent physical world.

    That IS different physics, alltogether! It is also something, which can be thought of as an argument against this new measuring unit system.
    It is clear that not all systems of measuring units can be chosen arbitrarliy. For instance , think of the weird physics, if we would say that a iron bar of 1 meter at 20 degrees celcius, would be under all circumstances our unit of length.
    Then explain all the phenomena, as the temperature risis, while the iron bar does not increase in length.
    This is an example of invalid unit of measurement.

    So, the question still remains, and is the major topic of discussion, if this new 'space expansion proportional' unit of measurement for length, is a valid option, or not.

    I have so far not read any conclusive arguments pro and against.
    The most profound one I have heard are the Planck length, as it provides 'absolute measurement' , and the fact that an atoms size can be expressed in terms of constants of nature only (e.g. c and h) which would then be regarded as constant.

    Nevertheless, several physicist dig into the issue wether the constants of nature are true constants. There are propositions in which for example light speed is not invariant (for example time dependend) and so on.

    So the debate is still completely open...
    Last edited: May 19, 2003
  14. May 20, 2003 #13


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    Staff: Mentor

    Heh. Only until you accept that you are wrong and quit.
  15. May 20, 2003 #14
    Ok, I don't understand what Heusdenis is saying, so I admit that I am wrong, surrender and wanna quit.
  16. May 20, 2003 #15
    In what way do you think I am wrong.

    Although this is a not too well thought over idea, and might be wrong, it is clear that even professional scientist put forward hypothesis that might require a change from measuring units, and which also messes with long believed thoughts, like constants as G, c, and h, that eventually might be not constants....

    There is a major shift and breakthrough in physics in the air...

    read for example https://www.physicsforums.com/showthread.php?s=&threadid=1465" on Theory development about Double Special Relativity.
    Last edited by a moderator: Apr 20, 2017
  17. May 20, 2003 #16
    Heus, you get SAME physics but expressed by DIFFERENT mathematical equations - just because you introduced DIFFERENT quantities to describe/derive SAME phenomena.
  18. May 21, 2003 #17
    It is arguable however that some phenomena do not exist in one system, but do in the other, and vice versa.

    In the new measuring unit system "space expansion" does not exist.
    In the normal measuring unit system "matter contraction" does not exist. These form complements.
  19. May 22, 2003 #18
    Of course if you change a system of reference some phenomena disappear. All phenomena are mathematical objects and thus their existence depends on their definition. They exist in one system and vanish in another.

    Say, a speeding bullet has plenty of kinetic energy and can kill stationary body. But pick a system of reference which is moving with same speed as a bullet - and bullet's energy vanishes. But now we have fast moving body (in opposite direction) and this body can be killed if it hits stationary bullet.

    So some phenomena (say, energy) vanish, while some other (say, interaction of bullet with body) stay.
  20. May 22, 2003 #19
    Exactly. They form complementary physics.

    Not the targer is to explain using new units of measurements, how atoms and other material objects seem to be contracting, for instance.

    Although, it might be still different, cause I reasoned that speed of light was constant in both systems, of course this does not have to be the case. We believe of constants as c, h, and G as universal constants (in all frames of references at all times and all places).

    But this is not necessarily the case.
  21. May 22, 2003 #20
    Atoms are contracting simply because your meter stick is expanding. Contraction of atoms and expansion of meter stick is same phenomenon in you length unit system.
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