First off, you can easily depict that the Earth is not flat without using a satellite to prove it; an example of one sort is basically when:
1. Go to the harbor:
A ship sails off toward the horizon, it doesn't just get smaller and smaller until it's not visible anymore. Instead, the hull seems to sink below the horizon first, then the mast. When ships return from sea, the sequence is reversed: First the mast, then the hull, seem to rise over the horizon.
Knowing this, The explanation relies on assuming that the sequential disappearance is simply an illusion brought on by perspective. I'd encourage you to all do the following: to prove to yourself that perspective isn't the reason for boats disappearing hull-first and returning mast-first, bring a telescope or binoculars on your trip to the harbor. Even with vision enhancement, the ship will still dip below the curve of the Earth.
2. LOOK AT THE STARS:
Greek philosopher Aristotle (I think Aristotle?) figured out this one in 350 B.C., and nothing's changed. Different constellations are visible from different latitudes. Probably the two most striking examples are the Big Dipper and the Southern Cross. The Big Dipper, a set of seven stars that looks like a ladle, is always visible at latitudes of 41 degrees North or higher, yes? Meanwhile, in the Southern Hemisphere, there's the Southern Cross, a bright four-star arrangement. That constellation isn't visible until you travel as far south as the Florida Keys in the Northern Hemisphere. These different stellar views make sense if you imagine the Earth as a globe, so that looking "up" really means looking toward a different sliver of space from the Southern or Northern hemisphere.
3. Take a round-the-world flight:
If you get lucky enough to get an unobscured view of the horizon and a high enough commercial flight, you might even be able to make out the curvature of the Earth with the naked eye. According to a 2008 paper in the ournal Applied Optics, the Earth's curve becomes subtly visible at an altitude of around 35,000 feet, as long as the observer has at least a 60 degree field of view (which may be difficult from a passenger plane window).
Now, on the fact on how Earth and planets get their spherical shape is simple:
According to the National Aeronautics and Space Administration (NASA) "The force of gravity, pulled this molten material inwards towards the planet's center into the shape of a sphere. Later, when the planets cooled, they stayed spherical. Planets are not perfectly spherical because they also spin." With NASA stating such clear facts, I'd like a comment on behalf of a flat earther to discuss why they think so and how I can change their opinion.
-LogisticSpeak