MadSci Network: Astronomy

Re: How many Earths can fit inside Jupiter?

Date: Sat Jun 4 03:01:43 2005
Posted By: Neil Saunders, Research fellow
Area of science: Astronomy
ID: 1116368207.As

Hi James,

We can try to calculate an answer to your question. Let's go to the Nine Planets website, which is a very good place to find out all about the solar system. If we look at the page for Jupiter, it says that the diameter of Jupiter is 142 984 km at the equator. On the Earth page, we see that the diameter of the earth is 12 756 km.

Now, we are going to pretend that both Earth and Jupiter are perfect spheres, shaped like a soccer ball. In fact this is not quite true - because they are spinning, the planets get a little bit squashed at the top and the bottom (as though you sat on the soccer ball). But we will ignore this for now.

To calculate the volume of a sphere, we use an equation. The volume of a sphere is:

4/3 * Π * r3
Π is a special number called pi (its value is about 3.14) and r stands for the radius of the sphere, which we cube (that means r * r * r). Now, we have the diameter of Earth and Jupiter so we have to divide that by 2 to get the radius. If we put those numbers into our equation we get some very large numbers:

Wow! The volume of Earth is more than 1000 billion cubic kilometres, but Jupiter is huge - over 1000 trillion cubic kilometres. Now we can answer your question if we divide the volume of Jupiter by that of the Earth. We get about 1400 - so about 1400 Earths could fit inside Jupiter. When other people do this calculation, they use more accurate numbers and so the number is closer to 1300. That might explain why you found a few different answers.

I hope you enjoy your studies. I also wanted to be a scientist when I was 7 years old and now I am!


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