Question

What do you think will happen if the Earth was indeed flat? Would you be able to sail all
around the world?

Answer 1

1. Gravity
Gravity is a relativistic phenomenon which occurs when there is some body existing in space-time with a huge amount of mass. But, one more thing about gravity is that no matter what is the size of the body, it will only act radially towards the center of mass of the body.
Imagining, if Earth was flat and there would have been gravity acting radially, the water on the earth had been collected at the center of the earth's surface, forming a globe of water. Also, as we move towards the edge of the earth, the gravity vector would start to incline instead of being perpendicular at every point of surface and when we reach at the cliff, it will act at an angle of zero degrees with the surface and become similar situation to that of hanging from a cliff.

2. Geotropism
This is a property of plants due to which the stem is allowed to grow in the direction opposite to the direction vector of gravity. If gravity works downwards, stem grows upwards (opposite situation for roots). If keeping a remind of this and the talk about gravity, as we move toward the edge of the flat earth, the trees will also grow in an inclined manner with respect to the gravity.

3. Day/Night cycle
Due to the curvature of the earth, when there is day on one side of the earth, other side is the night. If earth was flat the day and night would occur at the same time on whole of the earth.

Answer 2

There would be no proper day and night because the earth in flat shape cannot revolve.there would be less area