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• 10. All the other planets and stars we've ever seen are round

• and there's no reason to indicate that the earth should be any different.

• 9. Time Zones. Day and night happen at different times at different places on earth

• - in fact, it's always day somewhere and night somewhere else.

• 8. The Coriolis Effect means freely moving things (like cannonballs or hurricane winds) are deflected to the right -

• but only if you're north of the equator. If you're south of the equator, they're deflected left.

• 7. Triangles. If you walk 10,000km straight along the earth's surface,

• turn 90° to your right, walk 10,000km more, turn right again

• and walk another 10,000km, you will be back to where you started, having successfully made a triangle with three 90° angles.

• As any geometry student can tell you, this is impossible on a flat surface.

• 6. The sun, in general, gets lower and lower in the sky as you travel away from the equator

• and you can use this to directly measure the earth's curvature.

• Pick two places a few hundred miles directly north and south of each other

• and at noon, measure the shadows cast by a vertical meter-stick at each location.

• You can use the shadow-lengths to figure out the angle between the sticks

• and once you add in how far apart they are, you can calculate the earth's curvature.

• 5. The stars at night change as you go north or south - for example, Orion is upside down if you're in Australia!

• 4. Ferdinand Magellan (and many people afterwards) circumnavigated the earth.

• That means he left headed west, continued going west, and came back to where they started, still going west .

• (Actually, Magellan was dead, but one of his ships - led by Juan Sebastián Elcano - finished the journey.)

• If you head west and circumnavigate the earth yourself,

• you'll be able to tell because you'll observe one fewer sunrise than everyone who stays at home.

• 3. The horizon. Ships on the ocean or tall Chicago buildings viewed over Lake Michigan disappear bottom-first.

• And you can see the sunset twice if you watch it lying down and then quickly stand up.

• The simple fact is,

• if the earth were flat, there wouldn't be a horizon beyond which things could disappear

• so you'd be able to see all of Chicago from across Lake Michiganas well as the rocky mountains.

• 2. During a lunar eclipse, the shadow of the earth on the moon is curved.

• And... 1. We know the earth is round because we have photographic evidence.

10. All the other planets and stars we've ever seen are round

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B1 US earth equator west deflected curvature michigan

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