[RobC (OP)]

Both possess beliefs that I find unconvincing.
The former harder to prove erroneous than the latter.

[Kryptid]

It is a little different. It's very much possible to show that the Earth isn't flat, but it isn't possible to show that parallel universes don't exist. There are some reasons to believe that parallel universes could be plausible. It could explain why our universe has the right laws of physics to allow life to exist, it springs up naturally from certain intepretations of quantum mechanics, and I believe inflation models predict them (in a sense). I, however, am not convinced of their reality either. Could they exist? Certainly. I'll wait until some good verifiable evidence shows up first before I'll believe, though.

[Bored chemist]

There is  an important difference between impossible and possible.

[evan_au]

Have a listen for yourself.

Sean Carroll is a researcher approaching quantum physics from the 'many worlds' viewpoint.
- He happily admits that the underlying hypothesis is unprovable
- But suggests that it requires fewer assumptions than some other interpretations of quantum physics
- He engages rationally with people who hold other interpretations of quantum physics

Podcast: https://www.preposterousuniverse.com/podcast/
I suggest you start with this episode: https://www.preposterousuniverse.com/podcast/2019/03/04/episode-36-david-albert-on-quantum-measurement-and-the-problems-with-many-worlds/

If you think you understand quantum mechanics, you don't understand quantum mechanics.

[Petrochemicals]

Maybe theres a flat earth in an alternate universe at a different time in history.

But yes, its a load of junk inmyopinion. But then again so seems most of relativity, wormholes, pretty much all of theoretical physics, they just seem to be chasing there tail.

[Kryptid]

But then again so seems most of relativity, wormholes, pretty much all of theoretical physics, they just seem to be chasing there tail.

At least relativity has a massive amount of experimental evidence supporting it.

[Halc]

Both possess beliefs that I find unconvincing.
The former harder to prove erroneous than the latter.

The latter has abundant falsification tests. The latter, like any valid quantum interpretation, has none.
I think that rates the flat Earthers on a different level of crazy than the MWI people.

FYI, Everett's interpretation does not posit parallel universes, despite that popular spin on it by the pop media.

Sean Carroll is a researcher approaching quantum physics from the 'many worlds' viewpoint.
- He happily admits that the underlying hypothesis is unprovable
- But suggests that it requires fewer assumptions than some other interpretations of quantum physics

Of all the quantum interpretations, I do believe Everett's hypothesis hold the record for fewest assumptions:

"All isolated systems evolve according to the Schrodinger equation"

That's it.  No more. No positing of parallel universes.
I'm not an MWI guy, but I respect the simplicity of that.

[Malamute Lover]

Both possess beliefs that I find unconvincing.
The former harder to prove erroneous than the latter.

The latter has abundant falsification tests. The latter, like any valid quantum interpretation, has none.
I think that rates the flat Earthers on a different level of crazy than the MWI people.

FYI, Everett's interpretation does not posit parallel universes, despite that popular spin on it by the pop media.

Sean Carroll is a researcher approaching quantum physics from the 'many worlds' viewpoint.
- He happily admits that the underlying hypothesis is unprovable
- But suggests that it requires fewer assumptions than some other interpretations of quantum physics

Of all the quantum interpretations, I do believe Everett's hypothesis hold the record for fewest assumptions:

"All isolated systems evolve according to the Schrodinger equation"

That's it.  No more. No positing of parallel universes.
I'm not an MWI guy, but I respect the simplicity of that.

BTW, the many worlds in the Many Worlds hypothesis are not parallel, Technically they are perpendicular.

[alancalverd]

"Many  worlds" is a predictive model of reality. The flat earth is not. The difference is that the flat earth is obviously supported by turtles resting on elephants, and is therefore based on a pile of sh1t, whilst the manyworld model has no physical basis at all.

[Petrochemicals]

But then again so seems most of relativity, wormholes, pretty much all of theoretical physics, they just seem to be chasing there tail.

At least relativity has a massive amount of experimental evidence supporting it.

That can be read as denser gravitational areas having differing effects (suprise or light having mass, or energy being affected by gravity like momentum. After reading Einstein saying he had disproved the aether and then proved it  i stopped really caring, lots of other examples.

[Kryptid]

After reading Einstein saying he had disproved the aether and then proved it

Citation needed.

[Petrochemicals]

After reading Einstein saying he had disproved the aether and then proved it

Citation needed.

I am trying to find it. Also another unsubstantiated claim by me is newton hypothesised gravity acting by way of some sort of string connecting bodies, trying to find that one too.