The radius of the universe in meters is:
15e9 years * 365.2425 days/year * 24 hours/day *
3600 seconds/hour * 3e8 meters/second

   ] r=: */ 15e9 365.2425 3600 24 3e8
1.42006e26

Its volume in cubic meters is:
   o. 4r3 * r^3
1.19953e79

The minimum size of an atom is a Bohr radius sphere:
   o. 4r3 * 5.3e_11 ^ 3
6.23615e_31

The number of atoms is therefore bounded by the 
former divided by the latter:
   (o. 4r3 * r^3) % (o. 4r3 * 5.3e_11^3)
1.92351e109

That is, if the entire universe is packed with atoms,
there'd be no more than 2e109 of them.



----- Original Message -----
From: [email protected]
Date: Thursday, April 23, 2009 13:59
Subject: Re: [Jprogramming] table of primes to 1,000,000,000 or more
To: Programming forum <[email protected]>

> I believe the estimate of 10^100 atoms is actually hydrogen
> atoms.
> 
> Anyhow, I got my estimate from wikipedia.com.
> 
> 
> ----- Original Message Follows -----
> From: Zsbán Ambrus <[email protected]>
> To: Programming forum <[email protected]>
> Subject: Re: [Jprogramming] table of primes to 1,000,000,000
> or more
> Date: Sun, 19 Apr 2009 11:29:10 +0200
> 
> >On Sat, Apr 18, 2009 at 10:10 PM, 
> >> <[email protected]> wrote: If there are ~
> >10^100 atoms in the universe,
> >
> >I think that's an underestimate, there are actually between
> >10^200 and 10^300 atoms in the universe I believe.
> >
> >Ambrus
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