Braneworld, the Multiverse and other theories of the origin of the universe

First, something about the theory that most current astrophysicists consider to be the most likely. The traditional Big Bang theory assumes that the universe began singularity – a point with infinite density and temperature, the essence of which is difficult for our reason to understand.

The idea of ​​a singularity comes from Einstein’s general theory of relativity. The universe had an extremely high temperature and density in the beginning. Since the Big Bang, our universe has been continuously expanding. In order for it to expand to its current size in 13.8 billion years, the Inflationary Theory is used. This theory tells us that there was a phase in the early universe where space expanded exponentially. This expansion took place at a speed greater than the speed of light. The theory is verified by measuring relict radiation, the cosmic microwave background.

But this theory does not work in the quantum world, so it may not be true.

The brilliant British scientist Stephen Hawking said a few years ago: “According to Einstein’s general theory of relativity, space and time are connected in a space-time continuum that is not flat but curved by the contained matter and energy.” And he added two more dimensions to our universe. By this he explained that our universe has no boundaries. Hawking says: “In other words, that Euclidean space-time continuum is a closed surface without end, much like the surface of our planet.”

Good. Current science leans towards this. But there are still many theories of the origin of the universe that cannot be challenged just because most people believe in the Big Bang.

Thus, for example, McCullen Sandora, a scientist at the Blue Marble Space Institute of Science, claims: “The greatest proof of the multiverse is that there is intelligent life capable of making cosmological observations. Certain aspects of our universe appear to be special and important for supporting life, such as the longevity of stars, the abundance of carbon, the availability of light for photosynthesis, and the stability of complex nuclei. But all of these properties usually don’t apply if you’re presented with a random universe. The multiverse offers one explanation for why all these features are favorable in our universe, and that is that there are other universes, but we observe ours because it is capable of supporting complex life.”

In other words, so many things had to line up in our universe that if there were only one universe, there would probably be no life in it. But in the multiverse, there is enough “chance” for life to appear in at least one of the many universes.

However, this theory is not particularly convincing, so most scientists remain skeptical of the idea of ​​a multiverse.

The theory assumes another spatial dimension that we cannot directly perceive, in another perpendicular direction. This higher dimensional space is referred to as “matter”, while our universe is a three-dimensional membrane – or “gate” – floating within matter.

Does it seem complicated? But this theory explains the asymmetry of subatomic forces by suggesting the existence of other gates parallel to ours. However, verification of this theory is lacking.

In the distant future, the galaxies will eventually grow so far apart that light from one will never reach the other. In fact, as the stars age and die, there comes a time when there is no light or heat left. The universe will be a dark, cold, empty void. It sounds like the end of everything, but according to this theory, it’s actually the beginning of another universe in an endlessly repeating cycle.

One cold, empty gate collides with another, which, given enough time, must eventually happen. Cosmologists Neil Turok and Paul Steinhardt believe such a collision would generate enough energy to create an entirely new universe. Physicist Michio Kaku called it the Big Bang.

Imagine a security hologram. It is essentially a two-dimensional object encoding a full three-dimensional image. According to this theory, the entire three-dimensional universe can be “encoded” at its two-dimensional boundary. It may not be as exciting as living inside a simulation, but it has the advantage of being a scientifically testable theory – research from the University of Southampton in the UK in 2017 showed it was consistent with the observed fluctuation.

We return to the multiverse at the beginning of the article.

Some scientists believe that when our universe fell out of the inflationary phase, it was just one small bubble in the vast sea of ​​the inflating universe. In this theory, called “perpetual inflation” proposed by Paul Steinhardt, other bubble universes keep popping up in other parts of the inflationary sea, the whole ensemble forming a “multiverse”.

But this theory disproves the McCullen Sandory theory because there is no reason why other universes should have the same physical laws as ours. Others may have, for example, a different speed of light, or perhaps stronger gravity, etc.

Although we cannot observe other universes directly, one of them could collide with our own. Scientists even hypothesize that the “cold spot” in the CMB (relic radiation) is the imprint of such a collision.

It is possible. All theories about the universe depend on an understanding of gravity. It is the only physical force affecting matter on large scales. But it has a few catches. Gravity alone cannot explain astronomical observations. If we measure the speed of the stars at the edge of the galaxy, they are moving too much to remain bound to the galaxy; it’s just weird that it doesn’t fly away. Like galaxy clusters, they are held together by a greater force than would be held by gravity alone.

So far, there are two solutions: The universe contains dark matter, which makes up for the missing gravity from visible objects. Or there is the rather wild theory that our theory of gravity is wrong and must be replaced by modified Newtonian dynamics. This was suggested by scientists in 2002 in the journal Annual Review of Astronomy and Astrophysics. Both possibilities are consistent with observations, but evidence is still lacking.

Something rather fantastic at last, this time not from scientists, but from philosophers.

If all the information about the universe comes to our brains through our senses and scientific instruments, who is to say that it is not all a cleverly constructed illusion?

The entire universe may be nothing more than an ultra-sophisticated computer simulation. It’s an idea popularized by the movie The Matrix, but as bizarre as the idea sounds, some philosophers are taking it seriously. But it is not even a false scientific theory because there is no way to prove whether it is true or false.

The laws of physics include several basic constants that determine the strength of gravity, electromagnetism and subatomic forces. Although these numbers can be any value, this would mean that life as we know it cannot exist in our universe. Some people see this as evidence that the universe must have been designed this way by someone or something. This is called the self-centered anthropic theory (not entropic, the similarity of the name to the second law of thermodynamics is misleading), proposed by Nick Bostrom in his book “Anthropic bias”.