What is the best description of the Many-worlds interpretation using colloquial language and-or analogies?

Answer 1

Basically, the MWI denies the reality of wavefunction collapse.

What that means is rather simple.

Before the MWI we thought that the entire reality is a single, gigantic, unfolding "history"

According to the MWI, the reality can be compared to a gigantic branch with many, many side branches.

Imagine two different events. They can be virtually anything.

Let Ev.1 be you getting up early tomorrow. Let Ev.2 be you getting up early in two weeks time. There can be only two outcomes (you either get up early or you don't).

Let's assume that Ev.1 happened, but Ev.2 didn't.

Before the MWI, we thought that is the end of the story. Ev.2 could have happened, but it didn't.

According to the MWI, all the possible outcomes have happened ( Ev 1 happened, Ev.2 didn't, Ev 1 didn't, but Ev.2 did, both events happened, none of them happened), but all of them happened in their respective universes.

Each of the universes can be compared to a side branch of a gigantic branch I've already written about.

In fact, everything that could have happend in the past, but did not, has occured in the past of another universe.

Therefore, in the past of some other universe, Hitler won the WWII. And in the past of another universe, you have asked the same question, on the same website, on exactly the same planet, but someone else answered it.

MWI violates some of the most important principles of physics (eg. conservation of energy), and that is why it is not fully accepted.