1. If you had to prove the earth was round how could you do it
If you had to prove the earth was round how could you do it? The Flat Earth Theory Video: President of Flat Earth Interview

2. There’s 5 main observations you could use to theorize that the earth is not flat
1.) Ships seem to disappear into the horizon. This is caused by the curvature of the earth’s surface

3. 2.) Observations of the movements of planets and stars
The sun appears to move across the sky as do the constellations and moon in the sky at night

4. 3.) The changing altitude of Polaris

5. Wait, where is Polaris?
Polaris is located over the North pole, but its visual altitude changes depending on where in the world you are

6. Polaris/North Star’s position changes with latitude.
A person at the equator will see the north star at the horizon (the earth’s surface), & as he travels north, it will rise in the sky
*The altitude of Polaris= your Latitude!

7. 3.) Lunar Eclipses
During a lunar eclipse, the earth's shadow cast on the moon is in the shape of an arc (only spheres cast circular shadows)

8. At North Pole (Lat. 90º N), Polaris is 90º above horizon

9. New York City (41º N), Polaris is 41º above horizon

10. Equator (Lat. 0º), Polaris is 0º above horizon

11. Back to other reasons we KNOW the Earth is not flat…

12. 4.) Measurements of Gravitational Pull
Gravity is measured to be roughly the same everywhere on the planet +/- 1% . If the earth were not a sphere, it would change

13. Wait…what did you say about gravity?
If our planet were a PERFECT sphere, gravitational pull would be the SAME everywhere, so what is this +/- 1%?

14. Earth is a Oblate Spheroid
-Earth “bulges” about 40 (km) at Equator; gravitational pull is less (further from the core)
Which means you actually weigh less at the equator than at the poles!
(~0.5% less)
1 N= lbs F g=9.81 m/s-2  9.780 m·s−2 at the equator to about m·s−2 ,
the speed of an object falling freely near the Earth's surface will increase by about 9.81 metres (about 32ft) per second every second

15. 5.) Direct Observation
Technology NOW allows us to make a direct observation that the earth is a sphere ; obviously best evidence

16. You may have made your own direct observations…I did 