What are some things to tell a flat earther to convince them the earth is round?
Here are some arguments you can use to prove that the Earth is round.

• The Earth's shadow on the moon during a lunar eclipse is round. If the Earth were flat, its shadow on the moon would be a straight line.

• Different constellations are visible in the night sky from different parts of the world. This is only possible if the Earth is a sphere.

• When ships sail over the horizon, they do not simply shrink until they are out of sight. Instead, they slowly disappear hull first, which is only possible if the Earth curves away from the observer.

• The Earth's gravity pulls equally from all sides. This would not be possible if the Earth were flat.

• There are thousands of photographs and videos of the Earth from space that show it is a sphere. These images have been taken by astronauts, satellites, and even weather balloons.