The Relativity of Size and Numbers

Yesterday I received an email that contained some pictures of the relative sizes of the planets and some stars. One of the more impressive pictures was one that showed the relative sizes of Antares and Betelgeuse, two red giant stars, as compared to our own Sun. In the discussion of these images one person posed the question “so … How significant should we really be feeling, right about now?”
which set me to thinking.

I have seen statements to the effect that there are as many galaxies in the Universe as there are stars in our own Milky Way galaxy. I have seen estimates for the number of stars in the Milky Way that range from 100 billion up to 400 billion. For our purposes let's suppose that the number is closer to 200 billion
and that all galaxies average the same number of stars, realizing that any average of this type could be off by literally astronomical proportions.

So we are talking about 200 billion galaxies that average 200 billion stars each. Simple multiplication reveals that there are on the order of 4 x 1022 stars in the Universe. In more traditional form, that is 40,000,000,000,000,000,000,000 stars.

Now that's a lot of stars but consider this: I have seen estimates that a person who weighs 70 kilograms has about 7 x 1027 atoms in their body. Again that's 7,000,000,000,000,000,000,000,000,000 atoms, a whopping big number. That means that there are more atoms in my body than there are stars in the entire universe.

You can get a ballpark on the number of atoms in your body by first converting your weight from pounds into kilograms with 1 pound being equal to 0.4536 kilograms. Then all you have to do is plug your weight in kilograms into the following equation:

Atoms = (your weight in kilograms / 70) x (7 x 1027)

And as a parting shot, realize that the latest estimates are that the atoms that make up all our bodies and all the stars and all the dust and gas of the universe represent only about four percent of the “stuff” that makes up the Universe. Kind of gives you the feeling of doing a Linda Blair head spin (couldn't resist that since this is Halloween).

Ad Astra, Jim

| Return to the Blog Index | This entry was posted on Tuesday, October 31st, 2006 at 12:10 pm and is filed under Astronomy.