Starts With A Bang

Hey Shaq? Here’s How You Can Figure Out The Earth Is Round For Yourself (Synopsis)

NASA's famed Blue Marble image composite, from 2001-2002, using data from the MODIS instrument gave this fantastic two-hemisphere view of the Earth from space. Image credit: NASA.

“I drive from Florida to California all the time, and it’s flat to me. I do not go up and down at a 360-degree angle, and all that stuff about gravity, have you looked outside Atlanta lately and seen all these buildings? You mean to tell me that China is under us? China is under us? It’s not. The world is flat.” -Shaquille O’Neal

Perhaps the reason so many of us don’t quite believe the Earth is round is because we can’t directly see it for ourselves. At any point we happen to be on the Earth’s surface, when we look around in all directions, it appears to be flat. On his great sea voyage, Magellan and his crew never once perceived the Earth to be round, yet they circumnavigated the entire globe after enough distance had been traveled.

As ships sail farther away, a larger fraction of their hulls, sails and masts become obscured by the horizon, due to the curvature of the Earth. Image credit: stealth_sly of Pixabay.

Shaq may never have noticed the Earth’s curvature at any point along his I-10 drive from Florida to California, but if he had just gone a little farther — into the ocean — he could have seen it for himself. The effects of Earth’s curvature will cause buoys to appear more distant, closer to the horizon, and eventually to slip over it, depending on your height above sea level and your distance to the buoy.

When you’re at the optimal distance to measure the Earth’s curvature, a buoy’s bottom will be visible right on the horizon line. For a human at sea level, that will never be as much as six kilometers from the buoy. Image credit: mark_az of Pixabay.

Measure those two things correctly, and you’ll not only know that the Earth is round, you’ll be able to deduce the size of our world. Come find out how!