The earth does exist and has a shape or form that has nothing to do with what you or anyone else happens to believe in. There is no bias when it comes to the way things are in nature. They are what they are despite your belief.
And there is a difference between the way they are in nature, and the questions you ask about it.
Asking how to prove Earth is flat starts with the assumption that Earth is flat, and goes about trying to prove it.
Bias can be a quite significant issue in science and you need to be careful to ensure you don't allow bias to influence the experiments.
People are inherently biased, and will frequently look for things to support their own beliefs. Veritasium did a video on this:
People form an idea in their head, and then look for things to support it; rather than looking to try and answer what the real question is.
This can lead them to ignoring evidence which challenges their position, because they see it as non-definitive.
That could be well the case if you were to examine a situation where the answer was unknown and in some doubt.
i.e. all the time in science.
With science there is always some doubt.
This is because it extrapolates from evidence to build models.
It is religion that has no doubt, even though it doesn't know anything.
They don't have doubt, because rather than fallible humans obtaining knowledge by looking at the world and extrapolating from that; they believe their knowledge was given to them by an infallible being who created the universe.
As I have said many times, you are trying to turn science into religion.
Scientists in the past have had similar issues, with people coming up with all sorts of ridiculous BS for the aether, because they "knew" that light was a wave and that waves need media to propagate.
Except those scientists that "knew" that light was a particle, not a wave, and thus didn't need a medium.
Until someone decided to reject both assumptions and consider other options and we got the wave-particle duality of light, where light is a particle, and like all particles, exhibits the characteristics of waves.
And just like the ancient people who "knew" Earth must be flat, because a round surface couldn't contain the water or that people would fall off the bottom, and modern FEers who "know" Earth is flat, from looking out their window.
Arrogantly believing something is known beyond any possible doubt, that it could never be overturned; that they are beyond any possible debate and instead should simply be taken as facts, with no questioning and no attempt to verify them by anyone, even going as far as attacking those who request ways to verify it; takes you out well of the realm of science and places you firmly in the realm of religion.
You are here preaching religion. You are not promoting science. You are just as bad as all the FEers claiming to know that Earth is flat, yet refusing to justify their position.
Going back to the issue. An experiment of course asks a question. In this case, the shape of the earth
Yes, notice how the unbiased (or at least the less biased) question is asking what is the shape of Earth.
Asking for evidence that shows it is flat is biased, as it is assuming it is flat and only wanting evidence that it is.
Asking for proof, also takes you out of the realm of science.
in reality no farther investigation are required.
Likewise, your presence here is not required at all. Yet you keep on coming and offering extremely little of value.
Just because there is already mountains of evidence showing that Earth is roughly an oblate spheroid doesn't mean people can't ask for evidence.
You arrogantly suggesting that Earth is known to be a sphere beyond any doubt is not helpful or constructive at all.
If you don't want to answer questions or justify your position, why are you here at all?