What about the opposite question that I asked — can you point to a proof that could lead us to know with certainty (or close to certainty, if nothing is absolutely certain) that we live on a sphere?
Using an experiment that shows changes in shadow size in different places around the world doesn’t really prove it, because it assumes the sun is large and far away. If the sun is small and close, then there will be differences in shadow even in the flat model.
As for ships disappearing over the horizon from bottom to top — we see that with a camera with a strong zoom lens, the ship returns to the field of view, which means it isn’t hidden behind curvature, but rather beyond our visual vanishing point. If it were hidden behind curvature, then even a lens with infinite zoom wouldn’t bring it back into view.
I’d be glad to know whether there is any evidence that can give us certainty regarding the shape of the world.

Nowadays, it’s funny to talk about this.
After all, there are photographs of the earth taken from space, and you can clearly see the blue and magnificent globe.

The photos are definitely not only from NASA. Anyone who flies high enough can see the curvature on the horizon. Amateurs build rockets that reach the atmosphere with GoPro cameras; YouTube is full of this. This isn’t the kind of lie that can survive if it is made up of so many liars from different countries and cultures.

There is of course a very wide variety of experiments that can be done proving the earth’s sphericity, the most famous of which is obviously the ship that sinks into the horizon. The time of sunset changes depending on the height at which you are, and so on and so on. You can simply think and come up with more and more simple empirical experiments. For those who want to go further, there are also more complex mathematical experiments that prove it. Astronomical phenomena too.
The two main arguments of the conspiracy theorists are: 1) all the documentation and the people documenting are lying. 2) you explain things to us in ways that are too complicated — that’s how people lie. Explain something simple that one can connect to, like: the earth is flat, therefore we don’t fall — boom, I explained it in a second.
Regarding 1, any reasonable person understands that the likelihood of a lie encompassing so many people, from different classes, cultures, and countries, and not being exposed, is virtually zero. Regarding 2, one has to understand that reality doesn’t owe us anything, and it is allowed to be complicated. As stated, experiments can also be carried out independently and easily.

There are many amateurs like these:

The truth is somewhere in the middle, like everything else: the earth is a perfect cube with a certain flattening in the north-south direction…
Come on… really…. this discussion is a bit bizarre, when you speak with a person on the other side of the earth (west-east wise) or on the opposite side of it (north-south), and know for certain that on the other side, say in the U.S., when it is daytime for you, it is night there, or that when it is summer for you, in Australia it is winter and the sun is on the northern side — do you have some explanation other than a round earth?

The experiment they did proves nothing. This claim was already refuted in 1870; see here on Wikipedia: https://en.wikipedia.org/wiki/Bedford_Level_experiment
And his “answer” about ships disappearing is not an answer. The claim is not that it is impossible to see them, but that first the upper part of the ship disappears and only afterward the lower part; that happens because of curvature. I saw this clearly even in a video that the flat-earthers themselves uploaded.
As for the “scientific” nature of Matan’s claims, they are not scientific at all. When he came to discuss gravity and the experiment that confirmed it, his claim was: “According to the experiment, it turns out that a feather pulls an iron block — does that sound logical to you? Pffft, not at all.” In other words, he never carried out any refuting experiment; rather, on the basis of his prior impression of the world, which is irrelevant to the issue, he dismissed an experiment that was done in the past. That is not scientific work but laziness and stupidity. As David S. wrote above, this is a shallow outlook that is incapable of dealing with a complex world and mathematical calculations; there is no science here, but rather a childish viewpoint that is unwilling to hear at all about calculations and explanations more complex than simple intuition. The absurdity is that Elon Musk is just about to fly ordinary civilians into space, and there are still conspiracy theorists claiming that it is impossible to reach space at all.

Any reasonable person who investigates the subject honestly and does not rely on the opinion of the masses will easily reach the conclusion that the earth is flat. It is very strange to me that scientists, who are supposed to be faithful to the laws of physics, blatantly ignore the simplest and most basic law of communicating vessels. Suddenly, when people start talking about the shape of the earth, there are no laws of physics and water can bend. I would expect a physicist of integrity like Michi at the very least to refute this simple argument.

Wonderful. Have you thought of submitting your candidacy in Stockholm? A brilliant argument. How did no one think of this? “Be careful with the children of the poor, for from them Torah shall go forth.” 🙂

I’m convinced!

I read the thread here around the “flat earth” theory, and I enjoyed seeing just how easy it is for us to recognize that this discussion is not scientific at all.
After all, no one is really “measuring” whether the earth is flat — the discussion is about authority. Whom do you choose to believe: scientific institutions that present observations, or intuition that seeks simplicity and feels that everyone is pulling the wool over its eyes?

People who believe this are not always stupid.
Sometimes they are simply too skeptical — they do not believe anything that has not passed through their own filter, even if they have no tools to check it.
This is a familiar phenomenon in other areas too: vaccines, 5G, weather, and even… the Talmud.

And that made me think —
Maybe we also have “flat-earthers of the Sages.”
Intelligent, critical, articulate people — who insist on dismantling every saying of the Sages and setting against it external rational principles.
And what happens when the Sages do not fit with logic?
“Oh, that’s cultural influence.”
“That’s not really from Sinai.”
“That was only a ruling for their own time.”
And so on.

And just like with the flat earth issue — here too, this is no longer a discussion about one proof or another, but about the boundary of authority you are willing to recognize.
Can you say: “It may be that I am simply not in the right place or at the right height to understand the depth of these matters”?

Just as we do not insist on building our own astronomical models — but place a limit on our own reasoning — so perhaps sometimes it is appropriate to place a limit also in spirituality and tradition.

Rationalism is important.
But skepticism without humility can turn even the roundest truth — flat.