Why is the universe the way it is? Over the years, scientists have explored many ideas to explain our cosmos and its future. Here are some strangest ideas, from a braneworld scenario that involves the universe floating in a higher dimensional space to the “Big Splat” that describes such a brane colliding with another to form an entirely new universe
Braneworld
Some theories, however, suggest another spatial dimension – which we can’t perceive directly – in another perpendicular direction.
- This higher dimensional space is referred to as “the bulk,” while our universe is a three-dimensional membrane – or “brane” – floating inside the bulk.
We got gravity wrong
Theories of the universe depend on an accurate understanding of gravity – the only force in physics that affects matter on a very large scale
- But gravity alone can’t explain certain astronomical observations
- One possibility is that the universe contains dark matter, which provides the missing gravity
- Another is that our theory of gravity is wrong and should be replaced by something called Modified Newtonian Dynamics (MOND)
Simulation theory
According to some philosophers, the universe is a computer-generated illusion projected into our brains.
- The entire universe might be nothing but an ultra-sophisticated computer simulation.
- However, it fails the test of a true scientific theory because there’s no way it could be proved true or false.
Cosmic ego-trip
The laws of physics involve a handful of fundamental constants that determine the strength of gravity, electromagnetism, and subatomic forces. If they departed even slightly from the values they actually have, the universe would be a very different place.
- Some see this as evidence that the universe was consciously designed in order for human-like life to evolve.
The steady-state universe
Scientists came up with a way for the density to remain constant, even in an expanding universe.
- This involves the continuous creation of matter at the rate of about three hydrogen atoms per cubic meter per million years. However, this model fell out of favor with the discovery of the CMB.
The Big Splat
In the far future, galaxies will eventually drift so far apart that light from one can never reach another.
- According to one theory, this is actually the beginning of the next universe in an endlessly repeating cycle, known as the “ekpyrotic theory.”
The multiverse
Some scientists think 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,” proposed by Paul Steinhardt, other bubble universes are constantly popping up in other parts of the inflationary sea, with the whole ensemble making up a “multiverse.”
Superfluid space-time
Space-time is made up of microscopic particles on a deeper level of reality than our instruments can reach.
- It is a superfluid having zero viscosity, and can’t be made to rotate in a wholesale fashion like fluids.
- Tiny vortices form.
Plasma-filled cosmos
Immediately after the Big Bang, the universe was much smaller and hotter, filled with a glowing plasma like the sun.
- The expansion of the universe over the intervening billions of years has cooled the radiation down to minus 454 degrees Fahrenheit (minus 270 degrees Celsius), but it is still detectable by radio telescopes.
The holographic universe
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.
