Physicists have come up with a bold new idea to explain the enduring mystery of our expanding Universe – we might actually be living in a ‘bubble’ between other five-dimensional spaces.
If that makes your brain hurt, don’t worry, it’s supposed to. But we can break this down.
Our Universe as we know it has four dimensions: the three dimensions of space (up and down, left and right, back and forth), and one dimension of time that keeps us all ticking along.
But this new solution from physicists at Uppsala University in Sweden suggests that are other types of space that are five dimensional, and where two of those spaces come together, the junction forms an expanding bubble.
“It is conceivable that there are more bubbles than ours, corresponding to other universes.”
It’s pretty crazy stuff, but there’s an incredibly important goal here – to try and finally explain what’s going on with ‘dark energy‘, the theoretical force responsible for our Universe’s constant expansion.
It emerged from early efforts to add dimensions to general relativity, suggesting that properties of matter like charge and spin are a consequence of single-dimensional ‘strings’ wiggling multiple dimensions.
Those strings can behave in a huge variety of ways, depending on how many dimensions you add or other constraining properties, resulting in some 10^500 solutions, of which our Universe’s mix of features is just one.
The problem is it’s becoming increasingly clear that string theory is also wrong, and incompatible with what we observe in the Universe.
And where it’s not even wrong, it’s impractical, if not impossible to test. So why bother?
Well, there is more than one way to be wrong in science. Some wrongs are worse than others, and while it has major problems, string theory is like an old car that no longer runs but has plenty of scrap left in it.
Take this whole expanding space thing.
For a while now, we’ve blamed this on a force called dark energy – a phenomenon that sees more space being added without ripping up stuff floating inside it.
So we can ditch the whole string idea or throw out the de Sitter model we’ve all come to know and love.
But now the Swedish researchers have come up with a new solution that keeps both string theory and the de Sitter Universe solution.
It’s based on another idea that emerged around 20 years ago. Back then, American theoretical physicists Lisa Randall and Raman Sundrum proposed alternative models of the Universe based on different kinds of 5D spaces meeting at a point called branes, aiming to solve the problem of why gravity is so much weaker than other forces.