To you, what is the most incredible science experiment ever performed?

Someone determining that cow's milk could be tolerated by (most) humans.

Science is defined an an hypothesis confirmed by experiment. This is why the "Big Crunch" is still on the table as an ultimate state of the physical universe, even though the heat death hypothesis us considered more likely, as neither can be confirmed by experiment. We don't know how dark matter and energy will behave when the only sources of "normal" matter and energy are black holes, and neither do we know for certain that those black holes will "dissipate". So-called "Hawking radiation" has never been detected, so we have not the slightest evidence that it even exists. This post was edited by Slartibartfast at May 18, 2022 8:48 AM MDT

 

  Mayonnaise eradication.
~

That would be the "stout" experiment performed by James S. Auftinrong in 1984.  Mr. Auftinrong wanted to see what would happen if, when asked, actually told his wife that her jeans DID make her look fat.  The result was his immediate "launch" into space.  Despite decades of attempts to locate him, no one has yet (that's the real reason NASA launched the hubble telescope).