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 of the strangest ideas from a Braneworld scenario where the universe is floating in a higher dimensional space called the “Big Splat,” which describes one brane colliding with another to form an entirely new universe.
1. Braneworld
One aspect of the universe that we take for granted is its three-dimensionality: there are three perpendicular directions in which you can move. However, some theories suggest a different spatial dimension that we cannot perceive directly, in a different perpendicular direction. This higher dimensional space is known as “the bulk” while our universe is a three-dimensional membrane or “brane” that floats inside bulk.
As complicated as it sounds, the braneworld image solves several physical problems. For example, the theoretical physicists Lisa Randall of Harvard University and Raman Sundrum of the University of Maryland propose a version of the brane world that explains an asymmetry of subatomic forces by suggesting the existence of other branes parallel to ours. But it is not enough for a theory to explain facts that we already know; it has to make new predictions that can be tested experimentally. In the case of the Randall Sundrum model, such tests could include measuring gravitational waves emitted by black holes connecting one brane to another.
2. The Great Splat
In the distant future, galaxies will eventually move so far apart that light from one galaxy can never reach another. As the stars age and die, a time will come when there is no more light or heat. The universe will be a dark, cold and empty void. It sounds like the end of everything, but according to one theory, it is actually the beginning of the next universe in an endlessly repeating cycle. Do you remember the Braneworld theory? This happens when one cold, empty brane collides with another, which, given enough time, will surely happen over time. Cosmologists Neil Turok and Paul Steinhardt believe that such a collision would generate enough energy to create an entirely new universe. They call this the “ekpyrotic theory”, although the physicist Michio Kaku called it the “Big Splat” more aptly.
3. Plasma-Filled Cosmos
The Big Bang remains the theory of choice for many scientists, supported by two key observations: the expansion of the universe and the cosmic microwave background (CMB). Immediately after the Big Bang, the universe was much smaller and hotter, and filled with radiant shine. Plasma like the sun. We still see the end of this overheating phase in the form of a space-filling sea of radiation. The expansion of the universe in the intervening billions of years has cooled the radiation to minus 454 degrees Fahrenheit (minus 270 degrees Celsius), but it is still detectable with radio telescopes.
The CMB looks pretty much the same in all directions, which cannot be explained if the universe has always expanded at its current speed. Many scientists believe that it only happened for a short time. extremely rapid “inflation” period a fraction of a second after the big bang, suddenly rising from a subatomic scale to several light years.
4. Holographic Universe
This is basically a two-dimensional object that encodes a complete three-dimensional image. According to this theory, the entire three-dimensional universe can be “coded” at its two-dimensional boundary. It might not sound as exciting as living in a simulation, but it has the advantage of being a scientifically verifiable theory: Research from the University of Southampton, U., in 2017 showed it to work with the observed pattern of CMB fluctuations.
5. The Steady State Universe
The Big Bang is our best guess as to how the universe began, according to NASA. It used to be denser and it is becoming less dense. Not all scientists were happy with it, so they devised a way to keep the density constant even in an expanding universe. This resolution involves the continuous formation of matter at the rate of about three hydrogen atoms per cubic meter per million years; this model fell out of favor with the discovery of the CMB, which the model cannot easily explain.
6. Multiverse
In order to explain the unity of the CMB, according to the conventional Big Bang view, it is necessary to postulate an early onset of super-fast expansion known as inflation. Some scientists believe that when our universe emerged from this inflationary phase, it was simply a small bubble in a vast sea of inflated space. In this theory proposed by Paul Steinhardt, called “eternal inflation”, other bubble universes keep popping up in other parts of the inflationary sea, forming a “multiverse”.
The theory gets even stranger because there is no reason why other universes should have the same laws of physics as ours – some may have stronger gravity or a different speed of light. Scientists have even suggested that the “cold spot” in the CMB is the footprint of such a collision.
7. We’re wrong about gravity
Theories of the universe depend on a thorough understanding of gravity, the only force in physics that affects matter on very large scales. But gravity alone cannot explain certain astronomical observations. When we measure the speed of stars on the edge of a galaxy, they move too fast to stay in orbit if only gravity holds them back. Similarly, clusters of galaxies appear to be held together by a force stronger than the gravity of visible matter can explain.
There are two possible solutions. The standard preferred by most scientists is that the universe contains invisible dark matter that provides the missing gravity. The idiosyncratic alternative is that our theory of gravity is wrong and should be replaced with something called Modified Newtonian Dynamics (MOON). Scientists proposed in the 2002 Annual Review of Astronomy and Astrophysics. The two options MOON and Dark Matter agree with the observations equally, but still have to be tested. Further experimentation is needed.
8. Superfluid space-time
Even if space has only three dimensions, there is still a fourth dimension in the form of time, so that we can visualize the existing universe in four-dimensional space-time. According to some theories, such as that proposed by Stefano Liberati of the International School for Advanced Studies and Luca Maccione of the Ludwig Maximilians University in the Physics Review Letters, it is not just an abstract frame of reference containing physical objects such as stars and galaxies, but a physical physical substance in itself, analogous to an ocean of water. Just as water consists of innumerable molecules, according to this theory, space-time consists of microscopic particles on a deeper level of reality than our instruments can achieve.
Spacetime as a superfluid with zero viscosity. A strange property of such liquids is that they do not swirl en mass when stirred like an ordinary liquid. They break up into small eddies, which in the case of superfluid spacetime can be the seeds from which galaxies arise.
9. Simulation Theory
So far, all the theories have come from the scientists, but here’s one from the philosophers. The universe reaches our brain through our senses and scientific instruments, who can say that everything is not an intelligently designed illusion? The entire universe could be nothing more than a sophisticated computer simulation. It’s an idea popularized by the “Matrix” films, but as outlandish as the idea sounds, some philosophers take it seriously. However, it fails the test of a true scientific theory as there is no way it can be proven true or false.
10. Cosmic Ego-Trip
Laws of physics involve handful fundamental constants that determine gravity, electromagnetism, and subatomic forces. As far as we know, these numbers could have any value, but if they were to deviate even a little from what they actually do, the universe would be a very different place altogether. The most important thing for us is life as we know it, including ourselves of course – we couldn’t exist. Some people see this as evidence that the universe was deliberately designed for the evolution of human life – the so-called self-centered anthropic theory suggested by Nick Bostrom in his book “Antropic Bias”.
This article was adapted from a previous version published in How It Works magazine
