We can pretty easily prove gravity. It just depends if you want to accept it or not.

As for warped space time, I'd answer with the relativistic motion of high-velocity matter.

^

We actually have pretty solid equations for that.

Let me find one.

This has happened with Scott Kelly.

Ah, right, cannot post it.

They'd probably argue that he's a liar.

Or some variation thereof.

True.

Ah, satellites!

They need to adjust internal clocks every few months due to moving at relativists speeds.

They argue those are balloons.

And are also fake.

...

I told you, it doesn't have to make sense.

They just need *some* kind of explanation.

And cognitive dissonance can do the rest.

The second commercial Spaceflight is available, I’m buying tickets for as many flat earthers as possible.

Don't.

They may want a free ticket.

Save them for family, friends...

Good point.

Ah, what the hell, I’ll wait until they’re cheaper in the far future.

If flat earthers still exist then.

(Which I doubt.)

A lot of the issues that get brought up by flat earthers is that you're simply *telling* them something is the case. In the example of satellites adjusting their internal clocks due to special relativistic time dilation, there's no observable proof that they do this - just conjecture.

For a while there were those who doubted that humans could live 1,000 feet off the ground, and insisted that pilots, balloonists or anything similar faked it all.

Well, there is observable proof of this, but the problem they have is that it comes from sources they deem unreputable.

yes, exactly. there's no way for regular people to actually observe this themselves.

Well, there is...

*But*

so, it's an appeal to authority.

You need to put down some money to do it.

Flat earthers only deem sources reputable if they agree with them.

Less of an appeal to authority, but a close tangential all the same.

Sure.

you're saying regular people can get onto a moving satellite and watch the clocks adjust for time dilation?

They can put something on a moving satellite, yes.

Or on a sub-orbital rocket.

They can conduct their own experiments with enough money.