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!

I need help with a calculation please

  1. Jul 8, 2006 #1

    I was thinking about Cosmology and Omega-Matter. The critical density of the Universe is equal to about 6 Hydrogen atoms/ meter cubed. If we were to smear a human body out to fit it to this density, how big a volume would the human body smear out to be?

    Assume, the human body occupies a volume of ~1 meter cubed

    Assume, the average Mol. in the human body is 6,6-Carbon

    Can anyone figure this out? It seems like a fun way to gain perspective on just how undense the Universe is.

    P.S. Really our best WMAP data says the Universe's matter density is closer to 0.27 x 6 Hydrogen atoms. If we exclude dark matter, this number gets even smaller and becomes 0.04 x 6 Hydrogen atoms/ meter cubed.
  2. jcsd
  3. Sep 12, 2006 #2
    'any ideas folks?'
  4. Sep 19, 2006 #3


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    'A cube of side about 3 light-seconds (10^9m).'
  5. Oct 17, 2006 #4
    'I guess no one likes this idea, lol.'
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook