OK, so if you really take Quantum Theory to its extreme, there should be a multitude of universes where the laws of physics are different to ours. But since the laws of physics conform strictly to mathematical rules, this means that at least one of these universes would have different mathematical laws to us.

But how can the laws of mathematics be different? For example, surely 2+2=4 everywhere? How can we conceive of a universe where 2+2 didn’t equal 4 but equalled, for example, 5?

Well we could. Look at that equation above. 2+2=5. How can we prove that isn’t correct? OK, well don’t we look at the sum of the whole and compare it with the result? In other words, we count how many there are before, then how many there are after. But we have based those sums on what we observe. We could see that when 2 and 2 were brought together, the result was 4. So we created a rule to predict the result, to confirm the result, but not to ultimately know why that

*was*the result.
If we lived in a world where 2+2 did equal 5, how would we know the reason why this was happening? We would add together two 2’s, count the result, and the answer would be 5. The only way you can determine changes like this in amounts, is by comparing before and after. Even describing an addition of this kind as units moving over one at a time, so we can see the increase in numbers, doesn’t work. We can’t see a flaw, because a) we have to use the same mathematical laws to count, and the result is always the same and b) why would there be a flaw? The maths works.

You see that’s the point of the laws of mathematics being different. They still work. Adding 2 and 2 always produces 5, but nothing goes wrong as the computations get bigger and wider, because everything works. You put 200 and 200 together, you add up the result, and it’s 500. But if you add 100 and 100 together, you get 250. It all works. It looks completely illogical from “our” side, but to “them”,

*our*mathematics would look incomprehensible. To them, 2+2=4 would seem absurd, impossible, because in their universe it*doesn’t*work...because their laws of maths are different.
Of course, what’s to say that our universe of 2+2=4 is the “correct” one? Of course it isn’t. Quantum physics in our universe conforms to this equation, and Quantum physics is surely the same through all of creation, regardless of what “universe”? Well no, because any change in the laws of mathematics will directly affect Quantum physics, and make it slightly different. So our Quantum physics only applies to (and therefore describes...or is it the other way round?) our universe. Our physics cannot therefore predict what will happen in a universe with different mathematical laws.

Let’s take an extreme example.

A different universe exists where a particle took a quantum decision, say 60% probable. In our universe our Quantum Physics says this particle would be only 48% likely to take the same decision. That’s because that different universe says that 2+2=5. It is determined by, proven by, and conforms to the actual result observed each time.

Therefore there are an infinite number of these universes according to

*our*Quantum physics. But in the 2+2=5 universe,*their*Quantum Physics gives a different answer, one that our Quantum physics can’t even understand. Their answer may that there are a different infinite number of universes...but unfortunately that number does not include us.
However

*our*Quantum Physics will tell us that*their*universe can’t exist, because it doesn’t conform to our laws. Since there is no overall multi-universe yardstick for determining which law of mathematics is “correct”, therefore none of them are any more or less correct than any other. Because each universe can only use it’s own laws to investigate anything, and because the 2+2=5 universe can’t be described by our maths, how could we ever observe it, or even determine where it is and how to get to it?
To find their universe we would have to live in a universe where their laws already applied. In which case we would

*already*be living in that universe, so we couldn’t find it or observe it elsewhere. Because how would we determine if another universe we could see that was identical...actually*was*another universe, and not our own? We couldn’t, since only by it being different could we determine it was not us, but if it was*not*identical then we couldn’t observe it anyway.
Oh I know what you’re thinking. Surely we could observe universes where things were

*slightly*different, but the physical and mathematical laws were identical to our own? Yes, but those are changes in the world through the mathematics of our Quantum Physics, and since our Quantum Physics is the same as theirs, what happens is from the same set of laws. So they live in a universe where an electron went that way, and we live where it went this way? No I don’t mean that. I mean that another universe can’t have different mathematical laws than we have, and be observable by us. Our physical and mathematical laws predict that kind of universe can’t exist. But their universe’s physical and mathematical laws might predict that they can exist, and that*our*universe can’t!
So is there no way we can ever reach, or communicate with, these universes? No. We could reach a universe where President Kennedy was never assassinated, or the Gulf War never happened, or even where the US never landed on the moon...because although certain events would be different, they conform to the same physical laws as in our universe.

But the others? We can never get to them, for in order to exist, they have to be completely unreachable by us, because the laws of our universe will not provide us with a way to reach them.