The earth is round. Magellan's voyage around the world has long proved it. But why is the ground we see flat?
That's because the earth is too big. Its volume is trillions of times that of our individual human beings. It's impossible for us to see the whole earth In this way, when we are placed at a certain point on the earth's surface, the place that our line of sight can reach is nothing to the radian of the earth. The earth we see is flat This is why ancient people thought the sky was round. Only in modern times, when human steps can spare the earth a circle, can we find that the earth is round. It can also be seen that the earth is round after a considerable distance from the earth in space.
If the references are different, different results are obtained. In space, the earth is used as the reference, so it is round. You use the ground as the reference, so your conclusion is flat.