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Number of atoms in the OU

  1. Jul 31, 2010 #1
    What's up everybody,

    I have a curiosity that struck me today and I figure some people here could probably provide some insight on. Today I was reading the book Broca's brain by Carl Sagan, and in it he pegs the number of atoms in a grain of salt to be around 1018. However, in the same passage, he provides the number of "elementary particles" to be around 1080. I think he may have meant atoms by that, since i've seen numbers very close to that considered to be the number of atoms in the OU. I'm not extremely adept at math, but how are these two numbers compatable? Wouldn't the universe then necessarily be comprised of only about 4 grains of salt?

    I know that this book was written about 30 years ago or so, and that a lot has changed in the interim, but I asked my dad (who works as a chemist for AstraZeneca), and he said that Sagans estimate of atoms in salt was basically on point. The 1080 estimate is also found here: http://en.wikipedia.org/wiki/Observable_universe (last paragraph in the intro). So, what gives?
  2. jcsd
  3. Jul 31, 2010 #2


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    Gold Member

    I may have mis-understood what you said, but if you're suggesting that 1018 * 4 = 1072, this isn't true at all. By Sagan's estimation, and if the number of atoms in the universe is 1080, then the universe has 1062 more atoms than there are in a grain of salt.
    Last edited: Jul 31, 2010
  4. Aug 1, 2010 #3
    Nah, you understood. Exponential notation is strange animal to me, lol.
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