Cause or effect in the multiverse?

[God wonderer]

if the multiverse or many worlds theory exist how do we know that our is not just a reaction to an activity of another universe. In a multiverse who is the cause and who is the effect?

 

[PeroK]

This forum is only for you to introduce yourself. You should post any questions in the relevant forum. That said, I'm not sure where your question fits. There are several (mostly speculative) multiverse theories, so you will need to be more specific. And, given that multiverse theories are speculative, any question that begins "how do we know" is unlikely to have an answer.