Earth Activities,Earth Matters.

The diameter of the Earth is 12,742 km across. But this number is actually an average. That's because the Earth is spinning in space. The spin of the planet cause the equator to bulge out further than the poles.

So imagine the Earth as a slightly flattened sphere. Measured from pole to pole, the diameter of Earth is 12,713 km across. And measured across the equator, the Earth's diameter is 12,756 km across. In other words, points on the equator are about 21 km further from the center of the Earth than the poles.

One interesting result of this is that Mount Everest isn't actually the tallest mountain on Earth when you consider its distance from the center of the Earth. It's the highest above sea level; however. The highest place on Earth is Mount Chimborazo in Ecuador in the Andes mountain chain – it's about 2.4 km higher than Everest.

You can read more articles from Universe Today about the Earth. For example, did know know that the Earth has an inner, inner core? And here's a nice photograph of the Earth and Moon, seen from Mars.

Here's how the diameter of the Earth was first measured, thousands of years ago. And here's NASA's Worldbook entry on Earth.