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How many cubic planck lengths are in the observable universe?

  1. May 1, 2015 #1
    If you take the size of the observable universe can you find out how many cubic plank lengths can fit in the observable universe and it doesn't have to be exact just approximation.Also the math and formulas would be helpful too.
  2. jcsd
  3. May 1, 2015 #2
    Err... is there anything more to this than "volume of universe divided by volume of Planck unit cube"?
  4. May 1, 2015 #3
    Technically the amount of strings in the universe would be greater but the amount of strings in the universe in unnecessary and meaningless because most of space is empty(there are virtual particles, gravitational field, electromagnetic fields etc. but it doesn't occupy any real space and those things are for another forum) and strings don't have a definite size and by that I mean a plank length is 1.61619926 × 10^-35 meters and you can't say a string is exactly this small because plank length is a unit of measurement and a string is a theoretical object.
  5. May 1, 2015 #4
    I'm not sure I follow how strings fit into the OP question, which is just a "how many things of volume X fit into volume Y" question.
  6. May 1, 2015 #5
    Because, strings are smaller than cubic plank lengths so, if you use strings to find out how many of them fit in the universe it would be more than cubic plank lengths and as you said "volume of universe divided by volume of Planck unit cube" which is what I am asking about and if you then do "volume of universe divided by the volume of a string" which would be greater than your original statement in turn answering your question.
  7. May 1, 2015 #6
    Because, since strings are smaller than a cubic plank length you can fit more them in a volume so, in your original statement "volume of universe divided by volume of Planck unit cube" (which is what I am asking about) would be lets say "ƒ" and if you that the "volume of the universe divided by volume of a string" would be greater than "ƒ" and lets call it "β" so β>ƒ. Which answers your statement and in turn answers your question.
  8. May 1, 2015 #7


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    Staff: Mentor

    Google will tell you what the volume of the observable universe is and what the Planck length is. That's should be enough to allow you to calculate the value that you're looking for.
  9. May 3, 2015 #8
    Thank you so much! I work out that there should be 9.47491416160062548455633952329712e+184 or 9474914161600625484556339523297120000000000000000000-00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 cubic plank lengths in the observable universe!
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