1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Understanding conservation of momentum

  1. Mar 27, 2012 #1
    Is conservation of momentum a fundamental thing? For example :- conservation of energy is basic, its fundamental, it has no answer of why it is conserved. Its just a rule of nature

    So in the same way, is conservation of momentum a rule of nature or does it have a deeper reason?
    And newtons laws are basically derived from conservation of momentum right?
  2. jcsd
  3. Mar 27, 2012 #2


    User Avatar
    Science Advisor

    It sure does have a deeper meaning. Conservation of momentum can be derived from translational symmetry of the universe, based on Noether's theorem. Translational symmetry means that the laws of physics at one point in space are the same as the laws of physics at another point in space. This is a cosmological principle-- an assumption that we are not at a special place in the universe, and every place in the universe is equally special. Noether's theorem states that for every symmetry, you get a conserved quantity having to do with motion along the direction of symmetry. We also get conservation of angular momentum from rotational symmetry of the universe (physics don't depend on which way you are facing) and conservation of energy from time translation symmetry. (It's harder to explain why energy is motion in time.)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook