The common-sense rules of physics that we use every day may make sense to us, but at very small scales common sense breaks down altogether.

At the quantum level, the empty vacuum of space is boiling with tiny particles constantly popping in and out of existence.

At a quantum level, the vanishingly tiny particles that make up the building blocks of everything don’t even have a set location, just a smear of possible positions dictated by complex rules of probability.

And theoretical physicist Sean Carroll is entirely happy with that. He says that the fact that tiny particles like electrons and photons don’t have one set place in the universe is evidence that there are many parallel universes.

“But there’s a lot more going on,” he told News.com.au. “Not every world you imagine actually comes true.

(Image: Sean Carroll)

“There are still equations, physical rules, patterns that must be obeyed. Some possible alternate worlds can come true. But not all of them.”

Carroll has put forward groundbreaking, controversial theories on topics such as the Big Bang and the nature of time.

He has said that the universe didn’t start in a huge explosion, and most people now believe, but is an infinitely old, constantly inflating entity in which time can run "both forward and backward".

He says that we will soon have the tools we need to explore the quantum realm: "Technology has improved. Maybe things are going to change.”

For Carroll, the weirdness of quantum physics is not something to be fixed or built into a wider, simpler, theory of everything.

“As far as we currently know,” he writes, “quantum mechanics isn’t just an approximation to the truth; it is the truth."

Show more

“Physics is stuck trying to understand the fundamentals of nature and the Big Bang,” he says.

“It’s time to take a step back and understand its foundations. It’s time to tackle our understanding of the quantum world.”

He says that we need to forget classical ‘common sense’ physics embrace the weirdness of the quantum realm: “We see our world, and we have an idea of what’s going on,” he says.

“We demand our theories of physics respect that. But that’s really not the right way to think. It’s the other way around.”

And, in the universe next door, according to Carroll, there’s another version of you already thinking that way.