5 strange theories about the universe

1. The Big Splat 

In the far future, galaxies will eventually drift so far apart that light from one can never reach another. In fact, as stars get old and die, there will come a time when there’s no light – or heat – left. The universe will be a dark, cold, empty void. It sounds like the end of everything, but according to one theory, it’s actually the beginning of the next universe in an endlessly repeating cycle. Remember the braneworld theory? What happens when one cold, empty brane collides with another – which, given enough time, it’s bound to do eventually. Cosmologists Neil Turok and Paul Steinhardt believe such a collision would generate enough energy to create a whole new universe. They call this the ‘ekpyrotic theory’, though physicist Michio Kaku has more evocatively dubbed it the ‘Big Splat’.

2. The holographic universe

Think of a security hologram. This is basically a two-dimensional object encoding a full three-dimensional image. According to this theory, the whole three-dimensional universe may be ‘encoded’ on its two-dimensional boundary. It may not sound as exciting as living inside a simulation, but it has the advantage that it’s a scientifically testable theory – research in 2017 showed it was consistent with the observed pattern of CMB fluctuations.

3. The steady-state universe

The Big Bang is an evolutionary theory in which the universe changes in appearance as it expands. It was denser in the past, and it will become less dense in the future. Not all scientists were happy with that, so they came up with a way for the density to remain constant, even in an expanding universe. It involves the continuous creation of matter at the rate of about three hydrogen atoms per cubic metre per million years. This model fell out of favour with the discovery of the CMB, which it can’t easily explain.

4. The multiverse

In the conventional view of the Big Bang, in order to explain the uniformity of the CMB, it’s necessary to postulate an early spurt of superfast expansion known as inflation. Some scientists believe that when our universe dropped out of this inflationary phase, it was just one tiny bubble in a vast sea of inflating space. In this theory, called ‘eternal inflation’,
other bubble universes are constantly popping up in other parts of the inflationary sea, with the whole ensemble making up a ‘multiverse’.

The theory gets even stranger, because there’s no reason other universes should have the same laws of physics as ours – some might have stronger gravity, or a different speed of light. Although we can’t observe the other universes directly, it’s conceivable one of them could collide with our own. It’s even been suggested the ‘cold spot’ in the CMB is the imprint of such a collision.

5. Simulation theory

So far, all the theories have come from scientists – but here’s one from the philosophers. If all our evidence about the universe comes into our brains via our senses and scientific instruments, who’s to say it isn’t all a cleverly designed illusion? The entire universe might be nothing but an ultra-sophisticated computer simulation. It’s an idea that was popularised by the Matrix movies, but as outlandish as it sounds it’s taken seriously by some philosophers. However, it fails the test of a true scientific theory, because there’s no way it could be proved true or false.