Saturday, November 26, 2016

If there are (roughly) [math]1.33\times10^{50}[/math] atoms in Earth how are there [math]10^{78}[/math] to [math]10^{80}[/math] atoms in the universe?

Only is an interesting word to use in reference to a number like 10^80.

That’s a big number. Let’s write it like one:

100,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000

How much bigger is that number than 1.33x10^50? 10^80 divided by 1.33x10^50 equals:

800,000,000,000,000,000,000,000,000,000

That means the universe could contain that many Earths.

The Sun is as massive as 333,000 Earths. If we divide that big number with an 8 at the front by 333,000, we get:

2,000,000,000,000,000,000,000,000

That’s how many stars like our Sun could exist in the universe. There are about 200,000,000,000 stars in our galaxy. If we divide the number of stars by the number of stars in the galaxy, we get:

10,000,000,000,000

If every galaxy was made up of 100,000,000,000 stars, each the size of our Sun, we would need 10 trillion galaxies to come up with 10^80 atoms.

Now, I’ve made a lot of simplifications. There are other sources of mass. At the center of our galaxy, for example, is a black hole that is as massive as 4.6 million stars the size of our Sun. The most recent estimates of the number of galaxies in the universe is 2 trillion, making my back of the envelope guesses off by a factor of five.


Don’t look at the numbers in the exponents and make the simple comparison of their difference. That difference between 80 and 50 of 30 is misleading.

10^1 and 10^2 look very close together, but the latter is 10 times as big as the former. 10^3 is 100 times as big as 10^1. 10^4 is 1,000 times as big as 10^1 even though the difference between 4 and 1 is only 3.



Read other answers by Robert Frost on Quora: Read more answers on Quora.

from Quora http://ift.tt/2gKS86v

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