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Why is the universe as 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 storyline that involves the universe floating in higher dimensional space, to the “Big Splat” which depicts one such brane colliding with another to form an entirely universe. new.
1. Brane’s World
One aspect of the universe that we take for granted is that it is three-dimensional – there are three perpendicular directions in which you can move. Some theories, however, suggest another spatial dimension – which we cannot perceive directly – in another perpendicular direction. This higher dimensional space is called “mass”, while our universe is a three dimensional membrane – or “brane” – floating within mass.
As complicated as it may sound, the braneworld image solves several physics problems. For example, theoretical physicists Lisa Randall of Harvard University and Raman Sundrum of the University of Maryland have proposed a version of the brane world which explains an asymmetry of subatomic forces by suggesting the existence of other branes parallel to ours. But it’s not enough for a theory to explain facts 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 consist of measuring gravitational waves from black holes connecting one brane to another.
2. The big splash
In the distant future, galaxies will eventually drift so far apart that light from one can never reach the other. In fact, as the stars age and die, a time will come when there will be no more light or heat. The universe will be a dark, cold, empty void. It sounds like the end of everything, but according to one theory, it is actually the start of the next universe in an endlessly repeating cycle. Do you remember the brane world theory? This is what happens when one cold, empty brane collides with another – which, with enough time, will eventually do. Cosmologists Neil Turok and Paul Steinhardt believe that such a collision would generate enough energy to create a brand new universe. They call it the “ekpyrotic theory”, although physicist Michio Kaku has more evocatively nicknamed it the “Big splash. “
3. Cosmos filled with plasma
the big Bang remains the preferred theory of 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 warmer, filled with plasma shining like the sun. We can still see the end of this superheated phase in the form of a sea of radiation filling all the space. The expansion of the universe over the intervening billions of years has cooled the radiation to minus 454 degrees Fahrenheit (minus 270 degrees Celsius), but it is still detectable by radio telescopes.
The CMB looks practically the same in all directions, which cannot be explained if the universe has always expanded at its current rate. Many scientists believe he went through a brief period of “inflation“a fraction of a second after the Big Bang, whose size suddenly went from a subatomic scale to several light years.
4. The holographic universe
Think of a security hologram. It is essentially a two-dimensional object encoding a complete three-dimensional image. According to this theory, the entire three-dimensional universe can be “encoded” on its two-dimensional boundary. It may not sound as exciting as living inside a simulation, but it has the advantage of being a scientifically testable theory – a 2017 research from the Southampton University, United Kingdom, has been shown to be consistent with the observed pattern of CMB fluctuations.
5. The universe in a stationary state
The Big Bang is our best guess on how the universe started, according to Nasa. It was denser in the past, and will become less so in the future. Not all scientists were happy with this, so they found a way to keep the density constant, even in an expanding universe. This resolution involves the continuous creation of matter at the rate of approximately three hydrogen atoms per cubic meter per million years. This model fell out of favor with the discovery of CMB, which the model cannot easily explain.
6. The multiverse
In the conventional view of the Big Bang, in order to explain the uniformity of the CMB, it is necessary to postulate a first surge of ultra-rapid expansion known as inflation. Some scientists believe that when our universe came out of this inflation phase, it was just a tiny bubble in a vast swelling sea of 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, the whole constituting a “multiverse”.
The theory gets even stranger, as there is no reason other universes have the same physical laws as ours – some might have stronger laws. gravity, or a different speed of light. Although we cannot directly observe the other universes, one of them could possibly collide with our own. Scientists have even suggested that the “cold spot” in the CMB is the imprint of such a collision.
7. We were wrong about gravity
Theories of the universe depend on a precise understanding of gravity, the only physical force that affects matter on a massive scale. But gravity alone cannot explain some astronomical observations. If we measure the speed of stars on the outskirts of a galaxy, they are moving too fast to stay in orbit if the only thing holding them back is the visible galaxy’s gravitational pull. Likewise, galaxy clusters appear to be held together by a force greater than the gravity of visible matter can explain.
There are two possible solutions. The standard – favored by most scientists – is that the universe contains black matter, which provides the missing gravity. The maverick alternative is that our theory of gravity is wrong and should be replaced with something called Modified Newtonian Dynamics (MOND), scientists proposed in the 2002 journal Annual review of astronomy and astrophysics. The two options – MOND and dark matter – are also consistent with the observations, but remain to be proven. More experiences are needed.
8. Superfluid space-time
Even though space only has three dimensions, there is still a fourth dimension in the form of time, so we can visualize the existing universe in four dimensions. 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 Maximilian University, in the Physics Review Letters journal, it is not just an abstract frame of reference containing physical objects like stars and galaxies, but a physical substance in itself, analogous to an ocean of water. Just as water is made up of countless molecules, space-time – according to this theory – is made up of microscopic particles at a deeper level of reality than our instruments can reach.
The theory visualizes space-time as a superfluid with zero viscosity. A strange property of such fluids is that they cannot be made to spin globally, as an ordinary liquid does when you stir it. They break up into tiny vortices – which, in the case of superfluid spacetime, can be the seeds from which galaxies form.
9. Simulation theory
So far all the theories have come from scientists – but here is one from the philosophers. If all information about the universe enters our brain through our senses and our scientific instruments, who can say that it is not a cleverly designed illusion? The whole universe might just be an ultra-sophisticated computer simulation. It’s an idea that was popularized by the “Matrix” movies, but as bizarre as the idea may sound, some philosophers take it seriously. However, it fails the test of a true scientific theory, as there is no way to prove this to be true or false.
10. Cosmic ego-trip
The laws of physics involve a handful of fundamental constants that determine the force of gravity, electromagnetism and subatomic forces. As far as we know, these numbers could have any possible value – but if they deviated even slightly from the values they actually have, the universe would be a very different place. More importantly for us, life as we know it – including, of course, ourselves – could not exist. Some people see this as proof that the universe was consciously designed for human life to evolve – the so-called egocentric anthropic theory, proposed by Nick Bostrom in his book, “Anthropogenic bias. “
This article has been adapted from a previous version published in How It Works magazine, a publication of Future Ltd. To learn more about the wonders of the natural world, subscribe to How it works magazine.
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