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The presumed Invariance of the atom

  1. Nov 11, 2009 #1
    The physics building is based on the invariance of the atom.
    Is there any principle or law or experiment ?
    I think that we only presume.
    What if there is no foundation for our 'truth' ?
    Last edited: Nov 11, 2009
  2. jcsd
  3. Nov 12, 2009 #2


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    If you are asking whether all atoms of a given element have identical properties (mass, charge, etc.), there are numerous experiments verifying that. For example the use of cesium atoms in atomic clocks, because of the precise frequency of one of the transitions in cesium.

    We do not just "presume" in physics. The laws of physics do get tested experimentally, in fact performing these experiments is how many physicists earn a living.
  4. Nov 12, 2009 #3
    All experiments are done in a local lab frame. Testing the general 'invariability' of the rulers we made with that atom can not be done from a local lab.
    I agree with you that all atoms of a definite isotope that we can compare, at the same excitation level, seems fairly equal.

    How can we be sure that an atom (H to simplify) from the distant past is 'equal' to the lab H?

    What I think is that we use to apply the rulers to all times and positions, and I do not know a law/principle that validates the practice.
  5. Nov 12, 2009 #4


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    There is no law that says atoms in the distant past or at distant places are physically the same. There are theories that fundamental constants may vary with time or position. Does that make you happy? All you can do is make measurements to try to detect this variation. As far as I know, all of them, so far, come up negative.
  6. Nov 13, 2009 #5
    What is not writen can be very important.
    And there are a natural trend to disregard what is left outside the papper.

    All of the tests you mention are like:
    There are 'tests' on the possible variation of 'c', 'G', 'alfa', and the test results are negative. None has achived a construction of a stable universe based in 'laws' where those constants (one at a a time ?, or combined,..) could be 'not constants'.

    The exercise of varying things is pertinent because we have 3 basic physical equations and have more incognits (quantities M,L,T, and 'constants' epsilon,alfa,G,c)
    The quantities are related to 'objects', say atoms, and constants are related to space (the way the space let thinghs go).

    The 'tests' based on the quantities are doomed to fail, as they did, because there is something not writen in the equations that matters:

    We can not vary independently one or two of the quantities M,L,T, as they did in those tests. They can only vary at the same time because they are 'attached' to the 'atom scale'. It is so because it is the way we make 'rods', or rulers.

    We will have a large/small 'metre' definition [L], and by 'c' constraint a larger/small time unit [T], naturally a 'large/small atom' will have a grater mass [M].

    But this test was already made and claims to fit both local and cosmic data, with no break of known physical laws.

    I think that those tests are mainstream physics, independent of the outcome 'fit/no fit', in particular if there is no break of laws.
  7. Nov 13, 2009 #6


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    This sort of thing really doesn't belong in the Homework Help section. Why did you feel a need to put it here?
  8. Nov 13, 2009 #7


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    At which university? Do you know who was the architect?
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