Summary of How Many Multiverses Are There?

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00:00:00 - 01:00:00

This video discusses the various theories about the nature of the universe, including the theory of inflation and the new theory of the ecpirotic universe. It also discusses the work of Paul Steinhardt and Neil Turock in proposing a new level two multiverse.

00:00:00 The European Space Agency estimates that there are approximately 106 stillion stars in the observable universe. These stars form huge filaments and clusters, but on a more personal level, have you ever wondered what the night sky looked like when you were born under lucky stars? You can buy a personalized star map from lucky stars that shows what the stars were like on a day and time you choose.
00:05:00 In 1920, two prominent astronomers debated the size of the universe. Harlow Shapley argued that the stars of the milky way were the entire universe, while Heber Curtis argued that there were many more galaxies beyond the edge of the milky way. Hubble later discovered Cepheid variables within Andromeda's fuzzy light, confirming that they were extremely luminous stars far outside the Milky Way.
00:10:00 Hubble discovered that Andromeda is a galaxy in its own right and that other nebulae seen through telescopes must also be galaxies at immense distances, the great debate was settled when Curtis was correct and Shapley's response was here is the letter that destroyed my universe. The clouds parted and our cosmos suddenly became much bigger. In measuring distances millions of light years became billions of light years but was there a limit to how far we could see? In 1964 a chance discovery of a hiss of radio emission from all over the sky marked the limit of our observations and the cosmic microwave background radiation whose light has been traveling for 13.7 billion years marked the boundary of the map, a boundary between the observable universe we can see and what we cannot. This of course leads us to ask just what is beyond the observable universe. Through the 20th century telescopes got bigger and astronomers saw further but with their paper and pens the theorists were also hard at work building on the insights of einstein and friedman astronomers now had a mathematical description of the cosmos. Belgian cleric georges lemaitre realized that the universe was not infinitely old but had been born at a finite time in the past and had been expanding from a single point but if the cosmic equations are correct and
00:15:00 Astronomers estimate there are about two trillion galaxies in our observable universe. If we could travel at the speed of light, we would never visit these distant worlds, but we can use a logic to deduce their properties. In the simplest picture, there is an infinity of space in all directions and the universe over the horizon is just more of the universe we have here. In this universe, each individual universe is roughly the same size, contains similar numbers of atoms, planets, stars, and galaxies, but with an infinity of space to play with. Strange things can happen in these other universes, some of which are identical to ours. There is also a version of you watching this video. Such a situation would be vanishingly rare, with most universes being only roughly similar to our own. However, a vanishingly rare percentage of infinity is still infinity. How far away is this doppelganger? Max Tegmark estimates something like 10 to the power of 118 meters, which is much larger than the roughly 10 to the 27 meter diameter of our universe. And, of course, they are causally disconnected so you will never interact with them. However, they would be out there in the infinite along with every possible variation. Anything that has a chance of happening
00:20:00 This video discusses the theory of inflation, which suggests that the laws of physics in our universe were determined by a very early burst of rapid expansion. The theory has been met with some criticism, as it is difficult to imagine how inflation could be synchronized across the entire cosmos within this tiny window of time. However, the theory is still too attractive to simply abandon, and by the 1980s a flurry of activity gave birth to the new theory of inflation. This new inflation embraces the messiness of the original inflation, as the cosmos inflates instead of ending everywhere individual universes continuously crystallize out of the inflation. Our level 1 infinite multiverse is just one of countless separated by ever inflating space and time, and so we sit at the center of our observable universe across the horizon there is more universe that we can never explore.
00:25:00 The video explains that there are multiple universes, levels of universe, and theories of universes. The level 1 universe is one of the lucky few that can host complexity and life, and the apparent fine-tuning of our physical laws is little more than a statistical fluke. However, there is another level 2 multiverse that has been proposed that would require a multiverse of which our level 1 existence would only be a part, and in fact, Paul Steinhardt who developed the new theory of inflation in the 1980s plays a key role in a completely different idea. In Hindu cosmology, the universe is without beginning or end, and each cycle lasts for four million three hundred and twenty thousand years. Each universe starts with rebirth and perfection, and then ages the universe degenerates and decays before ultimate destruction and eventual rebirth. The physical universe could also be in a cycle, but there is a lingering problem with entropy. At the end of time, the disorder will be greater than at the start, and there is no way to escape and so if a universe is just part of an endless cycle, this entropy is passed from parent to child every cosmos beginning burdened with the disorder from all the universes that existed before. Although sometimes it is hard to completely kill a
00:30:00 Paul Steinhardt and Neil Turock propose a new level two multiverse, the ecpirotic universe, which develops out of string theory. This theory has gained widespread attention in recent years, but is still met with skepticism by many physicists. Ed Whitton followed a rather unconventional path on his way to becoming a professor of physics, eventually completing a PhD in fundamental physics and exploring how the universe works. While most physicists are searching for a single theory that encompasses everything we know about the universe, Whitton has set his sights on a much larger goal-a single theory that encompasses all the physics of the universe.
00:35:00 According to the mathematics of superstrings, there should be strange alter egos for electrons, selectrons for quarks, and squawks for other particles in addition to the familiar ones. However, superstrings theory failed to match the universe we inhabit, and eventually it fell by the wayside. In 1984, superstring theory was born in the minds of Michael Green and John Schwartz, with the key idea of strings being that all fundamental particles are really the same thing - just vibrations on a loop of stringy stuff. However, the mathematical complexity grew and ideas splintered, with there being five different versions of string theory following five different paths towards enlightenment by the mid-1990s. Frustration reached boiling point at the 1995 string theory conference, when Ed Whitton put forward the idea that the five differing theories of string theory were not so distinct after all - they were all the same theory intrinsically linked. This revelation was named "m theory" and the second superstring revolution was begun. Nobody really knows what the m in m theory stands for, with some saying it's mystery, and others suggesting it stands for membrane reflecting how the one-dimensional strings of string theory are drawn out into sheets or brains within the higher dimensions. However, once again our supposedly fine
00:40:00 Thomas Young's 1801 experiment showed that light is a wave, not a collection of particles. This discovery had far-reaching consequences, one of which was the realization that humans can potentially extend their lives via the use of light therapy. Young's level 3 multiverse is a place where immortality is guaranteed.
00:45:00 The key message of quantum mechanics is that the universe of classical physics is actually quantized, with tiny particles we now know as photons. However, this left scientists with a problem: how could they explain young's observation of an interference pattern between light waves, which is strange because light is supposed to be a particle? This problem was first proposed by Max Born in 1926, and it was Werner Heisenberg who first put a solution on the table, proposing that the wave function should be interpreted as a wave of probability. Many experiments over the last century have borne this out, but there is a problem with the Copenhagen interpretation: nowhere in successful mathematics is the mechanism for the wave function to collapse. This problem will eventually lead to our only level 3 multiverse, in which every particle exists in a wave form.
00:50:00 Quantum mechanics is a strange and mysterious field of physics that has been up for debate among physicists for years. Some claim that the wave function collapse is an unavoidable outcome of observation, while others argue that it is just an inconvenience. One of the more controversial aspects of quantum mechanics is the so-called Heisenberg cut, which determines the division between the micro and macroscopic worlds. In 1954, Hugh Everett proposed that the wave function also encodes all possible universes, and that the act of observation disrupts the coherence between them. This theory is known as the Copenhagen interpretation.
00:55:00 In the level 3 multiverse, every branching universe can be its own level 1 multiverse or even level 2 infinity. This creates an endless sea of parallel universes. Some physicists dismiss many worlds theory as exceedingly wasteful and believe that consciousness is too mysterious to understand. However, Everett's insights were largely ignored during his lifetime, and after receiving the cold shoulder from much of the physics community, he went on to work as a computer programmer and die of a heart attack at the age of just 51.

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This video discusses the idea of multiple universes, which may be found by cracking into parallel worlds. Some suggest that patterns may be written into the sky in the cosmic microwave background, which may be evidence of multiverse existence. However, contact or evidence of these alternate worlds is still unknown.