Foreword : I made a search for posts containing the word “bet” and I haven’t found any, so I hope my new topic will not appear unappropriated.

The thing: some ball-earther has defied me on producing even a single proof that the earth is actually a plane. He’s betting up to 3000€, against 1000€ of mine, and he believes that whatever I can produce won’t pass the scrutiny of an independent jury.

Which measurable, mathematical, exact proof would you bet if you were …