How can you prove that the Earth is round without traveling around it, or flying over it?

Question

I'm talking about direct physical observations that can be made locally...

Thanks, Answerer #1-I now see one thing that I have to change in my question-let's change "round" to "sphere". That's what I meant.

Bravo-wildgirl! Beat that, guys...

How about the difference bet. high tide and low tide? That's a hint...

Answer 1

I think that the proof (or evidence, anyway) that Columbus himself relied on (apparently simply observed as a child),
is still the best observational proof available. Sitting on the docks in Genoa, on the Mediterranean, he saw that the ships that sailed away to distant ports did not simply get smaller and smaller and then disappear (as they would on a flat surface). Instead, they diminished but part of them disappeared altogether as they went farther away. It was the BOTTOM of the boat that disappeared, while the top was still visible as a tiny image. More and more of the sails disappeared (working from the bottom up). Until finally, the TIP of the ship sunk down. The impression in his mind, was unmistakably that the entire ship SUNK DOWN, as if it were going downhill, or sinking. Yet the ship eventually came back, and knew nothing of the sinking he saw. The conclusion was that the earth is not flat, but round (or spherical).

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His second conclusion, that he could reach India by going West, however, turned out to be less accurate.

Answer 2

Go to the beach with some binoculars and watch a boat disappear over the horizon. The top part of the boat will be visible while the bottom is obscured. Or, get on an boat and sail away from shore; from the boat, tall buildings on land will still be visible while shorter buildings are not. This can only happen if the Earth has a curved surface. You can also try watching the North Star, Polaris at night. While all other stars move in an arc throughout the night, this star stays put. Take careful note of its position. Now travel south, about 60 miles or more. You will find that Polaris's altitude above the horizon has shrunk. If you go as far south as the Equator, Polaris will be sitting right on the horizon. This simply would not be the case if the world were flat; if the world were flat, the altitude of the pole star would be the same from any location. Finally, watch the Moon during a lunar eclipse. This is when the Moon passes directly though the Earth's shadow, which happens about twice each year. The Earth's shadow on the Moon is always circular. This effect could only happen if the Earth is a sphere.

Answer 3

Wait until the next lunar eclipse. There are two every year. They occur when the Earth passes directly between the Sun and the Moon, casting a shadow on the Moon which turns it red from scattered light. The shape of that shadow is always round, no matter where you are on Earth. So that would tell you that the Earth always casts a circular shadow from any angle - so it must be a sphere. Many ancient cultures new this, actually.

Answer 4

Measure the angle of a shadow cast by the sun at noon in two points along a meridian on the same day. From that (and the distance between the points) you can extrapolate the size of the earth and triangulate the distance to the sun.

The ancient egyptians did this.

Answer 5

Observe a lunar eclipse. You will see that Earth's shadow on the moon is rounded. This can only happen if Earth is spheroidal.

Answer 6

Are you allowed to call helpers on the phone and have them measure the angle from the horizon to the position of the sun in the sky all simultaneously? Or is that not 'local' enough?

Answer 7

Look at shadow of Earth on Moon.

Answer 8

By looking at pictures..haha I'm not sure