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

I A basic question about units

  1. Dec 31, 2016 #1
    This is a really basic question about units. I have been reading a paper about supernova rates and the units are given as:

    SN rate per yr MPC^3. h_70^3 (10^ -4)

    Could someone tell me what the h subscript 70 to the power of 3 means?

  2. jcsd
  3. Dec 31, 2016 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member
    2017 Award

    It is a dimensionless number denoting the current rate of expansion. It is equal to the current hubble rate divided by 70 km/s/Mpc.
  4. Dec 31, 2016 #3
    To the power of 3?
  5. Dec 31, 2016 #4
  6. Jan 1, 2017 #5


    User Avatar
    Science Advisor
    Gold Member

    A dimension is just another reference frame
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted