The only questions that round earthers REALLY need to fear are the questions of what is gravity? And what is a nature of suns light? Because their claims are provable hence are not physics as such. Its just theorizing what would fit their puzzle.
what is gravity? Definition; the force that attracts a body toward the center of the earth, or toward any other physical body having mass. For most purposes Newton's laws of gravity apply, with minor modifications to take the general theory of relativity into account.dumbed down: Big dense mass attracts more mass. a small representation of this is if you have a steady flow of water (out of your sink perhaps) and place an object close to it. (not under it) the waters path will no longer be straight down but rather askew tward the object. (different objects dhow this better)
what is a nature of suns light? Not sure what you mean by nature of sunlight. sunlight (or rather any light) is composed of the different colors of the spectrum of light. light is also pure energy thus meaning heat. sunlight also carries light that we cannot perceive with the naked eye, this light (UV for instance) is irradiated. when light hits an object light is absorbed and other light is reflected. the light reflected is what gives us color. for instance black absorbs all light. (why black items get hot because it holds the light) thus reflecting no light meaning that we perceive it as black. there are some objects that reflect nearly all light these are reflective for instance a mirror or moon dust. then there are objects that are see through that allow light to not be absorbed or reflected. these are transparent like windows or air. however sometimes not all light can be passed through and some colors appears more prominently such as mirrors have a very slight green tint to the reflections. water also can be transparent but in vast quantities it becomes clear that it can also reflect light. such as the ocean reflecting the blue in the sky. The sky is blue because molecules in the air scatter blue light from the sun more than they scatter red light. When we look towards the sun at sunset, we see red and orange colors because the blue light has been scattered out and away from the line of sight.
Edit im just going to leave this here (https://www.inverse.com/article/10770-people-who-think-the-earth-is-flat-are-wrong-but-flat-earthers-aren-t-nuts)
