Earth IS bigger than Mercury.
More Info: Mercury is notably smaller than the Earth. You may be wondering just how much smaller it is compared to Earth and there are several different ways to compare the two. To truly grasp the vast differences between the two planets, we’ll incrementally go down the many possible comparisons. That way, you’ll be able to truly grasp and appreciate just how more massive our home world is compared to Mercury.
The diameter of a planet is a great way to understand basic size. Diameter is measured by imagining a line that perfectly bisects the planet. Mercury’s diameter is roughly 38% that of Earth’s. This means that if you were to line up three Mercuries, you would find that this combined diameter is just barely larger than a single Earth’s.
Of course, size isn’t everything in the cosmos. The largest, most destructive single objects in the universe (black holes) are caused by some of the smallest things in existence. The difference is that these object’s masses are gargantuan.
Mercury, however, isn’t. According to NASA (the National Aeronautics and Space Administration), Mercury has roughly one-twentieth the mass of Earth. If you were to do the math, you would find that this means its mass if about 5% of ours.
Not only does this combination individually demonstrate Mercury’s diminutive status compared to our home world, the combined measure adds light to just how small it is.
If you know the size of an object (easily calculated from its diameter) and it’s mass, you’ll be able to find its density. This is the measure of how much mass is stuffed into the amount of space available. Objects with a high density includes neutron stars, certain asteroids, and some planets.
Mercury, however, is not one of them. The density of the planet is still less than of the planet Earth.
“Mercury Compared to Earth.” Universe Today RSS. N.p., n.d. Web. 16 Jan. 2013. <http://www.universetoday.com/22150/mercury-compared-to-earth/>.
Planetary Fact Sheet – Ratio to Earth Values.” Planetary Fact Sheet. N.p., n.d. Web. 16 Jan. 2013. <http://nssdc.gsfc.nasa.gov/planetary/factsheet/planet_table_ratio.html>.