How Many Earths Can Fit in the Volume of the Milky Way?

-- | December 14, 2015

Question: How many earths can fit in one galaxy and if the earth were about the size of galaxy how many planets, moons, etc. would be able to fit on earth. — Xondra

Answer: To answer this question you need to know the volume of the Earth and a galaxy. Let’s take the Milky Way as our galaxy example. The Earth’s volume is a little over 10^(12) km^3. To calculate the volume of the Milky Way, we assume that it can be approximated by a disk with a thickness of 1000 light years and a radius of 50,000 light years. A light year is about 9.5 x 10^(12) km, while the volume of a disk is pi*(thickness)*(radius)^2. Plugging in our thickness and radius we get about 6.7 X 10^(51) km^3. Dividing the volume of the Milky Way by the volume of the Earth, you get (6.7 X 10^(51))/(10^12) =~ 6.7 X 10^(39) Earths that can fit in the volume of the Milky Way galaxy.

Jeff Mangum

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