Density is a measure of how much mass is within a volume. Find out about the general relation that exists between a planet's size and its density with help from an educational professional in this free video clip.

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Density is a measure of how much mass is within a volume. Find out about the general relation that exists between a planet's size and its density with help from an educational professional in this free video clip.

Part of the Video Series: Outer Space

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Hi. My name's Eylene Pirez, and I'm an astrophysicist and this is "What General Relation Exists Between a Planet's Size and Its Density?" So, the first thing that I want to talk about is the concept of density. Density is a measure of how much mass is within a volume. Let's say that you have two boxes of identical size and here you have only, say, one person. That's a fairly empty room so that has a low density of people because that person for that entire volume is actually a low density. If you were to have, let's say, six people in the same room, it will feel a little more tighter, so then there is more mass for that exact volume. So, the same thing is happening in stars. So, generally, the bigger the star is, the more mass that it has, also the bigger the volume. So, generally, it tends to be a little more dense than usual. So, the general relationship is that this symbol Rho for density is the mass divided by the volume. So, let's say, like, we have planet Earth, the core of the planet is made out iron and nickel and, therefore, it has a lot of mass, so that mass for the volume is very dense. As we move to a higher layer, this material is not as massive and, therefore, when you divide it by the volume, you get a low density. So, the density keeps dropping as the mass with the volume. My name is Eylene Pirez and I'm an astrophysicist and this the relationship between mass and volume and the density of a planet.