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Classical mechanics and specific relativity

  1. Dec 14, 2003 #1
    i was asked to calculate the time that the neutrons from the sun reach the earth. i had no problem with that but my problem comes from the 2nd part.

    i was asked "would you expect a solution based on classical mechanices to differ significantly from one based on special relativity and why?"

    what i thought is: there's no difference since the speed of light is the same in the inertial frame since light travel through the vacuum to reach the earth without being affects by gravity.

    is that thought valid? i dun have much knowledge in relativity.

    also, i was asked to predict what will happen to the neutrons that reach the earth with their full initial energy and then slow down to thermal equilibrium with atoms in the atmosphere.

    my answer: neutrons slow down due to the decrease in temperature and decay since its halflife is just 10.25 minutes and it took 8.3 minutes to reach the earth.

    again, is that reasonable?

    thanks for your help. appreciate that
  2. jcsd
  3. Dec 14, 2003 #2

    Doc Al

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    Staff: Mentor

    Generally, if the speed of the particle is a significant fraction of the speed of light then special relativity is needed for an accurate answer. For slow (compared to light) speeds, classical mechanics works just fine. How fast were the neutrons going compared to the speed of light?
  4. Dec 14, 2003 #3
    no, the speed of the neutron is not given and i assumed the neutron travel at the speed of light to earth. is it reasonable?

    so i guess the answer won't differ too signigicantly since the law of physics works under different frame and just the classical mechanics is not that good dealing with light speed? is that valid?

    thanks for your help.
  5. Dec 15, 2003 #4

    Doc Al

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    Staff: Mentor

    I don't understand your statement. As I said earlier, the closer the speed is to that of light, the more you need to apply special relativity to get accurate results.
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