The visible universe including planets, stars, asteroids, comets, and galaxies; is made up of protons, neutrons, and electrons (“Normal Matter”) bundled as different kinds of atoms. One of the great discoveries of the twentieth centuries was to find out that all this visible matter was only 5% all matter in space. This led to the discovery of dark matter and dark energy as the other 95% of the universe.
The problem of Dark Matter was first discovered in 1937 when the astrophysicist Fritz Zwicky working at the California Institute of Technology made an argument that the universe was missing mass. While working on observations of the coma cluster (a cluster of 1000 galaxies), he was surprised to find that the average velocity of these galaxies was higher than expected. Now the speed of galaxies is supposed to mathematically predict the mass. But when Zwicky and compatriots measured the mass of the galaxies it did not equate to the high speeds. In other words, some mass was missing in these galaxies to account for the speeds measured.
Astrophysicists have continued to measure the speed of other galaxies and they too have found missing mass. Over the decades nobody has come up with an answer. But the astrophysicists began to think there is some invisible mass holding the galaxies together but in some invisible form. In recent decades science gave this invisible mass the name, “dark matter”. The implication was that a new type of matter must exist, and we just haven’t discovered or defined it yet.
In 1976 the astrophysicist Vera Rubin found that in spiral galaxies the stars out on the edge of the galaxy move faster than the closer-in stars. She found that the empty regions of space have too little visible matter to produce these high star speeds. Rubin concluded that some form of dark matter must lie in these remote regions of the galaxy to produce high star speeds. Science then concluded that “across the universe, the discrepancy averages to a factor of 6: cosmic dark matter has about six times the total gravity of all matter.”
Dark matter also exerts gravity like all ordinary matter. We know that dark matter isn’t just ordinary matter that is dark – it is something else altogether. Science has no clue about what dark matter really is, but they know from their mathematical calculations to arrive at a good description of a galaxy they must take into consideration dark matter. And from these calculations we know that dark matter must make up about 26% of the mass-energy of the universe.
Particle physicists think that dark matter consists of a yet undiscovered particle that interacts with both gravity and matter. So, it is possible that we will eventually find these particles in the Large Hadron Collider in Switzerland as they continue to increase the energy in the collider for particle collisions. Using collider technology, we have found neutrinos and recently the Higgs Boson. So, it is possible they might find a dark matter particle as they continue to ramp up the energy.
Dark matter does not interact with the strong nuclear force, the weak nuclear force, or the electromagnetic force. But we do know it does exert gravity like ordinary matter. But, so far, that is all we know about dark matter.
Dark matter is displayed by its gravitational effects. Here, ‘gravitational lensing’ is revealed via the Hubble Space Telescope. It shows a distant region of space with a large amount of dark matter in a cluster of galaxies. The Dark Matter in the cluster is bending the light and distorting the image of a galaxy much further away, creating multiple images of the galaxy which are stretched out into arcs surrounding the foreground galaxy cluster.
Dark energy is even more mysterious than dark matter. In the first half of the twentieth century most scientists believed that the universe was static and that gravity would eventually slow down the expansion of the universe. In the 1990s, two different teams found that the expansion of the universe was actually speeding up. This discovery threw a wrench into the cosmic calculations and caused a shock in astrophysics.
Unlike dark matter, scientists have no good explanation of dark energy. Some scientists think it may be the fifth force in the universe in addition to gravity, electromagnetism, the strong nuclear force, and the weak nuclear force. They also call it quintessence.
The history of dark energy’s discovery goes back to o1916 when Einstein published his general relativity theory. To make his equations fit a static universe he added a cosmological constant to the theory of gravity. According to Einstein his constant would be some kind of repulsive force that countered gravity.
But in 1929 the world was rocked by the discovery by Edwin Hubble that the universe was not static – it was expanding. Einstein than said his cosmological constant was the biggest blunder in his life. But, as it turns out, his cosmological constant was correct. It explained later in the century how space-time is being stretched apart and that dark energy is actually 69% of the mass-energy of the universe. But this doesn’t explain why this new force exists in the first place. It might be a part of space-time itself, or it might be due to a misunderstanding of how gravity itself works over cosmological distances.
The idea that we live in multiple universes is an old concept whose time might have come, although it is still being debated vigorously by physicists. Physicists have struggled for years to develop a working description of what they call Quantum Gravity and what Einstein called the unified field theory. This is the marriage between Einstein’s theory of gravity and quantum mechanics. There have been many attempts to combine the two but the most practical may be string theory, which changes the micro world from small particles to very tiny energy strings. These are strings of energy that look like tiny rubber bands that are much smaller than an electron. String theory looked like an attractive solution but it failed in a world with only 3 space dimensions. To make it work String theorists needed 10 dimensions, which made the multiverse a possible reality. The multiple universe theory is supported by some of the assumptions of quantum theory.
Schrodinger Wave Equation - About the same time as Einstein’s great discovery, a man named Schrodinger invented a mathematical Wave Equation that measured possibilities in an experiment. It is not worth explaining here how the wave equation works except that it leads to a statistical probability. This is a big deal in Quantum mechanics because things at the sub atomic level cannot be measured accurately – they can only be measured in terms of probability. For instance, scientists might say where a particle might land in 4 different quadrants, which can only be summarized as a 75% probability that it will land in Quadrant A.
The Many Worlds Theory: In addition, the Schrodinger Wave Equation generates an endlessly proliferating number of possibilities. This can be interpreted by physicists as also generating an endlessly proliferating number of different branches of reality. This theory is called the Many Worlds Interpretation of Quantum Mechanics. For instance, how can science explain the fact that a photon could be measured as landing in 2 places at the same time? Quantum Theory says that it can be in both places because of the “many worlds theory of reality.”
This is the beginning of further experiments that prove multiple dimensions of reality. “The Many Worlds theory defines any particular branch of reality which might actualize to us as a result of an interaction of an observed system with an observing system as merely one way of decomposing the wave function which represents them both. According to this theory, all of the other states which “could have” resulted from the same interaction did happen, but in other branches of reality. Each of these branches of reality is real, and, together they constitute all the different ways in which we can decompose the universal wave function. If this is just a bunch of mumbo jumbo to the reader then it can be better explained by a simple thought experiment.
Schrodinger is also famous for an experiment he did called the Schrödinger’s Cat. The experiment was to put a cat in a box with poison gas triggered by the decay of a radioactive substance, which is based on a probability. Classical physics says when you open the lid; the cat will either be dead or alive. Quantum Mechanics says the fate of the cat is not determined until we observe it. Many Worlds interpretation says that reality splits into 2 worlds where in one reality you find the cat alive and in another reality, you find it dead. It says different editions of us live in many worlds simultaneously and all of the worlds are real.
Another way of expanding multiverses is by using the big bang when the universe was expanding very fast in a period science calls inflation. During this period called inflation, the universe expanded from a small speck to an entity as large as the solar system in a fraction of a second. At the end of inflation, the energy driving the expansion erupts into a fireball of particles and radiation. And, in this fireball there are microscopic bubbles that were also expanding. These bubbles are actually universes and we live in one of them but cannot see the others.
This picture of the universe is called the multiverse and it suggests there are other universes and dimensions in space-time. For the theoretical multiverse to work there must be some kind of pressure energy density in the vacuum of space. This pressure is called dark energy.
To confirm that dark energy and dark matter exist, science has recently measured both of them accurately in the European space craft called Plank. The measurements accurately fit the expected magnitude of the equations, and proved that the concept of the multiverse is probably correct. In fact, the Plank space craft measured dark matter as 26.8% and dark energy at 68.3 % of the mass of the universe. Adam Riess, a Nobel Winning physicist, says “I have no clue what dark energy is. Dark energy appears to be enough to push the entire universe – yet its source is unknown, its location is unknown, and its physics are highly speculative.” But dark energy appears to be the only force capable of forcing the universe 20 % faster than 5 billion years ago.
However, to date, there is no experimental evidence that exists that proves that a multiverse exists, even though the mathematics shows that both dark energy and a multiverse must exist.
Testing the theory
In an article in The Conversation in September 2015, the author Eugene Lim said, “The universes predicted by string theory and inflation live in the same physical space (unlike the many universes of quantum mechanics which live in a mathematical space), they can overlap or collide. Indeed, they inevitably must collide, leaving possible signatures in the cosmic sky which we can try to search for.”
The exact details of the signatures depend intimately on the models – ranging from cold or hot spots in the cosmic microwave background to anomalous voids in the distribution of galaxies. Nevertheless, since collisions with other universes must occur in a particular direction, a general expectation is that any signatures will break the uniformity of our observable universe.
These signatures are actively being pursued by scientists. Some are looking for it directly through imprints in the cosmic microwave background, the afterglow of the Big Bang. However, no such signatures are yet to be seen. Others are looking for indirect support such as gravitational waves, which are ripples in space-time as massive objects pass through. Such waves could directly prove the existence of inflation, which ultimately strengthens the support for the multiverse theory. In the summer of 2017 actual gravity waves were measured by the new LIGO system at Hanford. WA and in Louisiana.
Multiple universes have been hypothesized in cosmology, physics, astronomy, religion, philosophy, transpersonal psychology and literature. In religion, the proof of multiple universes might enhance religion’s claim there is a heaven. Proof might also help physicists unify relativity and quantum mechanics.
From a personal point of view, I kind of lean toward eventual proof of dark energy and a multiverse because it is supported by the “many world’s theory” of quantum mechanics which so far has never been proven wrong. All of this study of multiverse theory has reminded me of a science fiction story I read when I was 15 years old called “BEYOND THE STARS” by Ray Cummings. The story tells of a crew on a rocket that goes beyond light speed and eventually passes atoms and then molecules to emerge on a glass slide under a microscope in a parallel universe. It seems that the idea of multiple universes has something for everybody.