WHEN renowned professor Stephen Hawking died earlier this year, it seemed that the greatest of all mysteries may have died with him.

For decades, Hawking had been working on theories about the nature of the universe - the multiverse hypothesis, specifically. The idea is based on theories about the existence of multiple universes instead of just one. As humans once believed earth was at the centre of our universe and everything rotated around us, multiverse theories smash the idea that the universe we are part of is the only one.

The secrets of the multiverse may have seemed lost to us after Hawking’s death, however, the world this week got the exciting news that just ten days before he died, Hawking and co-scientist Thomas Hertog submitted a new paper – and yes, it was about the multiverse. It by no means solves the mysteries of the universe, but it furthers scientific thought and gives people plenty to think about.

So what exactly are these theories? Is it really possible, as some theories have it, that there there universes out there in which identical versions of all of us are living slightly different or wildly different lives? In one universe, you are a saint, in another a killer; in one a pauper, in another an tycoon. Is it possible that a universe exists where the dinosaurs were never wiped out? Where T-Rex evolved into an intelligent lizard? Do we live in a simulated universe? Back in the 1600s, the philosopher Rene Descartes suggested we might be living in the dream of some evil god ... today, Matrix-style, some think we might be avatars in a computer game played by a being much greater than us.

Buckle up because you are about to enter the world of mind-bending theoretical physics...


INFINITE UNIVERSES: If this theory was ever proved correct, it would mean that an identical version of you exists in an infinite number of universes. The infinite universes theory is based on combinations: the idea is that all of the molecules that make up our universe are arranged in a particular way. In other universes, they would be arranged in a slightly different way. However, even the number of molecules in the universe have a finite number of combinations, so eventually in infinite universes the combinations start to repeat themselves, creating exact copies of us. There will be another you out there, doing exactly the same as you are doing right now - scratching their head and reading another identical version of the Sunday Herald in another universe and trying to understand the multiverse theory. It is the infinite universe theory that sets up the idea that in another universe the dinosaurs are still alive.

BUBBLE UNIVERSES: This theory is rooted in something called “eternal inflation”. Basically, as the idea goes, the Big Bang caused the universe to expand rapidly in the immediate aftermath of it, like a balloon. Some of that expansion stopped, creating universes like ours, while the rest of space-time is still inflating, thus creating a picture of bubble universes. It’s a bit like imagining our universe as one of many air pockets, but on an astronomical, cosmic scale.

PARALLEL UNIVERSES: This refers to universes that exist in different dimensions. In a nutshell, think of parallel universes as being stacked on top of one another, or next to each other, but which cannot ever reach each other. This well-known theory often amplifies the frustrations about the multiverse – that amazing worlds could exist but we can never experience them.

DAUGHTER UNIVERSES: Imagine this universe shaped like a family tree. If you have to decide whether to have breakfast or not, two universes immediately exist to cater for each outcome - one for you eating breakfast, and one for you not eating breakfast. Then you decide whether or not to go to work - and two more universes form - and on it goes, the decisions made in each universes spawning more universe. This theory is the most likely one to make your head explode just thinking about it.


Mathematics as we know underlies the laws of physics and how the universe works - so it is easy to assume that mathematics is sort of pure, that the rules and laws of it are unchangeable, whether in this universe or another. This multiverse theory turns that upside down and imagines that other universes can exists with their own versions of mathematics, with different sets of laws and rules. It’s difficult to even imagine what they might be like - but one of those crazy Escher diagrams might be close.


Remember Rene Descartes worrying if he was a dream in some weird being's mind? Well, philosophers and theoretical physicists are still worrying about it. We’re well into The Matrix territory here with this theory, although it doesn’t have a huge following. In its current form the theory proffers that our universe could be part of a massive computer simulation created by some unknown being or force. Time to level up.


THE BIG BANG: This is the accepted theory about the origins of the cosmos. Crucially, the theory traces the birth of the universe back to a single point, a beginning, thought to be around 13.8 billion years ago, when everything was created in a kind of cosmic 'let there be light moment'. Though what came before? Another universe? And what comes after? Another universe?

STEADY STATE: This theory was in competition with the Big Bang theory for a time. Basically the universe has always been and always will be, and is in a constant state of creation. It became widely discredited by leading figures in science in the mid-1900s.

BRANE: Perhaps this should be called the brane-melting theory. The concept of brane universes is linked to parallel universes. While some theories claim that parallel universes exist close to each other but never interact, brane theory suggests it’s possible that they do touch - and this is what causes Big Bang type events.


Physicists will be pleased to hear that Hawking and Hertog concluded that rather than the multiverse being made up of pockets of unpredictable universes, where literally anything could be possible, it’s more likely that the different universes within the multiverse are fairly similar to one another in terms of matter. So in other words, you won't get a floating unicorn made out of x-rays in one of the other universes out there ... though you could get a unicorn. It’s possible that scientists might actually may able to test this theory ... but don’t get too excited too quickly, the work relies on assessing gravitational waves and the technology required to do it isn’t expected to launch until 2034.


The Matrix

The Matrix trilogy, starring Keanu Reeves and spanning 1999-2003, is a mindboggling exploration through the simulated universe theory – what we understand as reality is actually a computer simulation, the film suggests, and the human race has been enslaved by machines. Do you take the blue pill or the red pill, Neo?

Men in Black

Will Smith and Tommy Lee Jones brought all kinds of weird and wonderful creatures to the big screen in the 1990s with the successful MiB franchise, which bundled all kinds of cosmic theory into a good old-fashioned goodies vs baddies format.


In 2014 Matthew McConaughey took movie-goers on a truly bonkers journey through time and space when he and a group of astronauts tried to save the human race by transporting it through a wormhole. It’s perhaps not a terrible idea to jot down on the list of humanity’s options …