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Age of a particle and related considerations

  1. Oct 23, 2006 #1

    During the life time of an unstable particle, can it be said that this particle ages? Can the relativistic muons that zip through the atmosphere be considered to age slowlier wrt the Earth, or should a different concept be used?

    If age does make sense when speaking of a particle, is it theoretically possible to attribute a relativistic age to each stable particle that exists since the big bang depending on the trajectory and the various speeds and gravitational influences the particle has undergone?
  2. jcsd
  3. Oct 24, 2006 #2
    yes and no

    theoretically it is possible to put a an age on a particle but the problem is "in relation to what?" We, as people, use minutes, years, weeks, months, years, etc... to standardize time. Like in relativity, the question is "who can you truly have a reference towards?" Particles that travel at different speeds have different ways to measure time, and thus, it becomes difficult to standardize everything. Particularly when speed changes do things get messy.

    So, "yes" it is possible to say that muons, for instance, age slower than that of the earth and it's ape-like inhabitants but "no" because of velocity and acceleration, things have had different systems to measure time and thus things like age, for everything in the universe (especially when a person lacks info on a particle's history) does it become impossible to put an age on everything. (Using all of these individual systems to measure age would give you an "infinite mess" of math :)
  4. Oct 25, 2006 #3
    Thanks for your explanations, pibomb.

    Of course one should pick a preferred frame before one attempts to calculate the age of any particle. In spite of the practical impossibility, I wondered what kind of result we could expect for the average age of all particles in the universe. I suppose it would be less than the estimated age of the universe, due to the fact that everything moves around and thus ages slowlier. But now that I think of it, when we speak of the age of the universe, with respect to which frame of reference do we express it? That's tricky...
  5. Oct 25, 2006 #4
    For the observable universe select the frame of reference that give the minimum summed momentum vector and angular momentum.

    I suspect that this will approximate the rest frame of the big bang.

    Observationally the Cosmic Microwave Background should give the minimum total momentum.

    Classically then one could then calculate the total time dilation (special and general relativity) of a total world line of a particle.

    In quantum mechanics with particle indistinguishably and the wave function traveling all paths the calculations is more problematic.
  6. Oct 25, 2006 #5
    Thanks Larry
    Yes, it is really problematic, but it was some kind of thought experiment.:smile: Maybe we could discover some kind of universe-wide equilibrium in the age of the particles, classically or quantically, since everything seems linked up by way of various symmetries. If the universe was composed of only two particles, they would influence each other to the point that maybe they would move symmetrically and age equally.
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