A common estimate of the number of particles in the observable universe is 10 to the power of 80-less than a googol, and less than the number of zeroes in a googolplex. (Admittedly, this estimate does not include photons and dark matter.) Carl Sagan once said that writing out googolplex would be impossible, because the known universe simply doesn't have enough space.
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Key Facts In This Video
A googol is 10 raised to the power of 100—in other words, a 1 with 100 zeroes after it. 00:33
A googolplex is 10 raised to the power of googol. 02:53
A universe that was a googolplex meters across would likely contain repeated versions of yourself. 03:56