Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Normalization of Four velocity

  1. Jun 7, 2015 #1
    The scalar product of four velocity u with u gives -1. This is said as normalization of four vector.
    But how does the scalar product yield -1 and whats normalization of four vector.
    Immediate help required:oldconfused::oldconfused::oldconfused:
  2. jcsd
  3. Jun 7, 2015 #2


    User Avatar

    Staff: Mentor

    Write down the velocity four-vector using coordinates in which the object in question is at rest, then calculate its scalar product with itself. What do you get?

    Be aware that the magnitude of the result will depend on the units you use - it only comes out to be one if you use units in which the speed of light is one.

    If you get the wrong sign, that will be because you're using a different sign convention for the metric: you can write ##ds^2=-dt^2+dx^2+dy^2+dz^2## or ##ds^2=dt^2-dx^2-dy^2-dz^2##; they both work as long as you're consistent and you'll see them both used.

    If none of what I just said makes sense, you're missing some prerequisites - google for "four-vector" to learn about four-vectors.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Normalization of Four velocity
  1. Meaning of four-velocity (Replies: 58)

  2. Four velocity in GR (Replies: 16)