That's a fine experiment but there are quite a lot of other stuff that confirms the Earth is spherical.
1. The Coriolis effect
2. Leon Foucault's pendulum
3. Stars: If you are in the southern hemisphere, you can't see the same stars as in the northern hemisphere
4. You can go to the North pole and take time lapse photo of the stars. They rotate counter-clockwise. From the south pole, they will rotate clockwise.
5. Earthquakes : When an earth quake happens one side of the globe, it takes a while but the vibrations reach the other side of the globe. However, a dead zone becomes visible. Scientists have determined that the cause is a radically, high density sphere that composes the Earth's core. It reflects the vibrations. So, a shadow region appears on the other side of the globe.
6. Plenty of other reasons.
6. When measuring the sun's position in the sky from multiple locations you're able to do the math and see that all measurements point to a distant sun, not a local one. When put on a model of a flat earth, the measurements do not meet up at one location. When put on a model of a spherical earth, the measurements do meet up, and are all (nearly) parallel with each other.
7. Distances between locations, as we have measured them, can only work on a spherical earth. The flat earth model does not allow for accurate distances in the southern hemisphere. The round earth model does.
8. The moon cannot work on a flat earth. The moon is either flat or round. If flat, then when viewing it from any angle other than directly underneath, it will appear as an ellipse, rather than the circle we constantly see it as. If the moon is round on a flat earth, then we should be able to see much more than just one side. If the moon circles right above the equator, those in the northern hemisphere will see the "near side", and those in the southern hemisphere will see the "far" side. This does not, EVER, happen.
9. The sun and moon's angular sizes in the sky are always the same. The sun and moon never shrink or grow.
10. The sun and moon's angular speeds in the sky are always the same. If the the earth was flat, then their speeds in the sky would change. As the sun/moon got nearer to you, they would appear to be moving faster and faster, and vice versa for when they move away.
11. Sunsets are not possible on a flat earth. The sun will never physically go below any horizon if earth was flat.
12. Parallax measurements with stars are not possible on a flat earth. In reality, because Earth orbits the sun, it moves quite a distance throughout the year. We area able to use this movement to determine the distance of stars. The process is parallax. We can measure stars' position in the sky at one time, then again 6 months later, and use the measurements to calculate the distance. This is not possible in a non-moving Earth.
13. If Earth is flat and gravity is nonexistent, there should be no differences in the weight of an object when measuring it at different locations on the Earth. This is not the case. An object's weight will differ on different locations on Earth, depending on its altitude, latitude, coordinates, etc.
14. A 24 hour sun in the antarctic is not possible on a flat earth.
15. There's no reason for a flat earth to have a lower atmospheric pressure as you go higher up. We can observe and measure this phenomenon, and can explain it using gravity. Flat earthers cannot, because if the Earth was surrounded by a pressurized dome, then there should be no change in pressure.
16. Satellites cannot orbit above a flat earth. We can observe satellites, take photos of them, track them, etc. They're real.
There's more, obviously. Feel free to add on.