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Earth view from Apollo 11
The Earth is the 3rd planet, or the third rock from the Sun if you don’t mind a pun. No surprise there, but what do you really know about the planet that you live on? Here are a few quick trivia facts that you can stump your friends with.
How long does it take the Earth to rotate on its axis and around the Sun? Twenty four hours on its axis and a year around the Sun, right? Nope. The Earth rotates on its axis in less than 24 hours. It is actually 23 hours, 56 minutes and 4 seconds. This is the sidereal day. We orbit the Sun every 365.2564 days. It’s this extra .2564 days that creates the need for leap years. That’s why we tack on an extra day in February every year divisible by four unless it’s divisible by 100 (1900, 2100, etc)… unless it’s divisible by 400 (1600, 2000, etc). Huh?
How many moons does the Earth have? Come on, everyone knows we only have one moon, or do we? Technically, there is only on true Moon, but there are two co-orbital satellites. These satellites are the asteroids 3753 Cruithne and 2002 AA 29. Cruithne is sometimes called Earth’s second moon because it is in synchronized orbit with our planet. 2002 AA 29 is much smaller and has a horseshoe orbit around the Earth that brings it close to the planet every 95 years. In about 600 years, it will appear to circle Earth in a quasi-satellite orbit.
The 3rd planet, like all of the others, is perfectly round!?!? There is not a perfectly round planet, or any other celestial object, in our solar system. Rotation and gravitational perturbations make most objects slightly oblate spheroids. Earth bulges at the equator and is 43 km shorter than it is around.
There are enough facts about the 3rd planet to fill volume after volume. I would recommend you start with these few and research a few more each day.
We have written many articles about the Earth for Universe Today. Here are interesting facts about the Earth, and here’s an article about why the Earth rotates.
If you’d like more info on Earth, check out NASA’s Solar System Exploration Guide on Earth. And here’s a link to NASA’s Earth Observatory.
We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.
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