Splattering your brain all over meaning

In a book I'm reading there is a sentence like this

This is difficult to imagine without splattering your brains all over the person next to you as you read this

Here is the situation:

But how can an infinite universe be consistent with what we see? Can a universe be infinite and expand from a Big Bang? Yes, but only if you don’t assume the Big Bang started from a single spot. Imagine a Big Bang that happened everywhere at the same time. This is difficult to imagine without splattering your brains all over the person next to you as you read this, but it’s also totally consistent with what we observe.

My question is what does Splattering your brain all over the person mean?

I have searched in many dictionaries and google but I couldn't find the phrase "splatter sth over sb" there.

Please explain to me.

Thanks.

from the accepted idiom: blow someone’s mind free dictionary

to impress someone; to overwhelm someone. "This whole business just blows my mind".

use of splatter used as adj: free dict

4. characterized by gory imagery

Splattering your brains ... just adds an element of a gore.