What is the fastest way to disprove a flat earth?

Here is the one that works best, out of about half a dozen. You ask the question: do you believe in satellites? You know, those things that go above the earth, weather satellites, the ISS, space stations, thousands of them. If he says no, he is a flat earther, and you say, okay, end of discussion. Why? Because a weather satellite 22,000 miles above the equator is going to show you a spherical earth, and there is no picture of a flat earth anywhere. That is why they do not believe in satellites, because satellites take pictures of the earth that are round. So if he says there are no satellites, then he is ready for the looney bin, and you walk away. Try that next time you get into a discussion.