How real is the multiverse?

Imagine setting off in a rocket and leaving Earth. Leaving the solar system. Leaving our galaxy. Breaking through the edge of the observable universe and leaving our cosmos behind (which would be impossible, as you’d have to go faster than the speed of light, but work with me here).

Now you are cruising through the unfathomable void for eons, only to come upon another universe, with another galaxy inside it, with another solar system, another Earth … and another you, sitting there, reading this article.