No, the Earth is not flat.
The shape of Earth is an oblate spheroid, a sphere flattened along the axis from pole to pole such that there is a bulge around the equator. For the last 50 years, we’ve been able to view pictures of the Earth from space, which might seem like all the proof you need to see that our planet is in fact round.
Compare shadows of sticks in the ground at different locations. In one spot where the sun is directly overhead, there will be no shadow. In a spot a few hundred miles away, for example, the stick will have a shadow. If the earth were flat, both sticks would have no shadow because they would be at the same angle toward the sun. That was good enough for the ancient Greeks, who used it to calculate the circumference of the earth with 90% accuracy in 250 B.C.
You can also tell that our planet is spheroid-shaped by noting the differences between the views of space from the northern and southern hemispheres, which are totally different because they are facing in different directions. If the Earth was flat, both hemispheres would have the same view.
If these points still haven’t convinced you, send a camera up to the edge of the atmosphere or hope onboard an intercontinental flight to take pictures of the curvature of the planet.
If this helps even one person challenge their belief that the Earth is flat, it’s a remarkable win for knowledge, common sense and Humankind.