For those who are unaware, let me first state that Occam's razor is the principle that among competing hypotheses, the one that makes the fewest assumptions, and therefore the simplest, is most often correct. This is a very useful principle in the pseudoscience against science, or flat earth against round earth, debate. Consider the following statements:
When at sea it is possible to see high mountains or elevated lights in the distance before lower-lying ground and the mast of a boat before the hull. It is also possible to see further by climbing higher in the ship, or, when on land, on high cliffs.
The sun is lower in the sky as you travel away from the tropics. For example, when traveling northward, stars such as Polaris, the north star, are higher in the sky, whereas other bright stars such as Canopus, visible in Egypt, disappear from the sky.
The length of daylight varies more between summer and winter the farther you are from the equator.
The earth throws a circular shadow on the moon during a lunar eclipse.
The times reported for lunar eclipses (which are seen simultaneously) are many hours later in the east (e.g. India) than in the west (e.g. Europe). Local times are confirmed later by travel using chronometers and telegraphic communication.
When you travel far south, to Ethiopia or India, the sun throws a shadow south at certain times of the year. Even farther (e.g. Argentina) and the shadow is always in the south.
It is possible to circumnavigate the world.
Travelers who circumnavigate the earth observe the gain or loss of a day relative to those who did not.
An artificial satellite can circle the earth continuously and even be geostationary.
The earth appears as a disc on photographs taken from space, regardless of the vantage point.
Now, consider which of the hypotheses is the simplest. Obviously, the round earth. The flat earth "theory" states that each of these statements is either a conspiracy or a blatant lie or another convoluted means of attacking the "truth" of the flat earth.
But the truth is, the simplest hypothesis is almost always correct, and it's clear and simple that the earth is round.
I challenge any flat-earther to provide ten concrete pieces of evidence that the earth is flat, and that the earth being flat is simpler than it being round.