Oskaloosa.com

CNHI/Southeast Iowa

April 22, 2013

Slate: 15 facts about our planet

It's easy to take Earth for granted, since we see it every day. It becomes — it is — part of life's background.

But when you see the world through the eyes of science, nothing is mundane. We live on the surface of this great giant space-borne water-laden spinning rock, separated from the rest of the Universe beneath a thin veil of nitrogen and oxygen molecules. Even though you're immersed in its influence, what do you really know about the Earth?

Here are some facts about our planet for you to ponder.

1. There are a lot of different ways to measure how long it takes the Earth to go around the Sun, but if you say it takes pi x 10 million seconds, you'll only be off by a half a percent.

2. The Earth has a volume of about one trillion cubic kilometers. Can you picture a cube 1000 meters high, 1000 meters deep, 1000 meters across? Now picture a trillion of them. That's the Earth.

Actually, if you were that big, it would be easy.

3. The Earth has a mass of 6,000,000,000,000,000,000,000,000 kilograms, or, if you prefer, 6 sextillion tons. In pounds, that's actually . . . 0. Nothing. Mass is a measure of how much stuff an object contains, but weight is how hard gravity pulls on that mass. The Earth is in space, orbiting the Sun, so it's in freefall. It has mass, but no weight at all.

4. The Earth isn't a perfect sphere. It spins, so it's a flattened at the poles a little bit. The diameter through the poles is 12,713.6 kilometers (7882.4 miles), but it's 12,756.2 kilometers (7908.8 miles) through the equator. That difference of 43 kilometers is only about 0.3 percent, though, so really we're pretty close to a perfect sphere.

5. Not only is it flattened, but the gravitational forces of the sun and moon (what we call tides) distort its shape even more, pulling bulges out from it. The Earth is lumpy! Out in the deep ocean, the bulge of water due to the sun and moon can have an amplitude (change in height from minimum to maximum) of about a meter (40 inches). The solid Earth deforms due to the tides, too, with an amplitude of roughly 50 centimeters (20 inches). Even the air is affected by tides; though there are several factors that greatly complicate it (like expansion due to heating from the sun during the day, and, simply, weather).

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