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Magic Numbers Make the Universe or The Miracle of Stars and Why We Are Michael Bass, Professor Emeritus CREOL, The College of Optics and Photonics University of Central Florida Orlando, FL 32816 © M. Bass Cosmologies are how we understand the universe Biblical and Mythical. Then God said “let there be light” and there was light Aristotle’s universe of spheres with the earth at the center. Copernicus’ sun centered universe. Newton’s universe of absolute motion. © M. Bass Einstein, relativity and the Big Bang –Today’s Cosmology Einstein’s universe of relative motion. Einstein plus quantum mechanics and the Big Bang Universe. © M. Bass Hubble Telescope Ultra Deep Field Image – all spots are galaxies and all galaxies have many, many stars! Just in case you didn’t believe me this image shows a few of the 100s of billions of galaxies in the universe. A cosmology has to account for all of this and more. © M. Bass A scientific cosmology must explain The night sky is dark. The universe can not be static. Hubble’s law of galaxies rushing apart. The 2.7 K (loosely called the 3 degree) black body radiation that fills the universe. The fact that there is 1 helium atom for every 10 hydrogen atoms in the universe. © M. Bass More Facts to Explain There are stars, galaxies, clusters of galaxies, clusters of clusters, and other structures in the universe. Dark matter and dark energy. There are novas and super novas and places in galaxies where stars are continually formed. There are planets and on at least one there is US! © M. Bass The Big Bang The outward rush of the galaxies from one another can be run backwards to an initial beginning. About 13.7 billion years ago the universe was no bigger that a sub atomic particle, it was very, very hot and it started to expand. Everything that we see around us was determined in this moment of creation. Thanks to George LeMaitre a Catholic priest who saw this solution in Einstein’s general relativity. © M. Bass Big Bang Nucleosynthesis This is a big name for the cooking of atoms during creation. The Big Bang model explains many observed features of the universe - the He:H ratio, the 2.7 K black body radiation, the Hubble law and so on - but it only explains atoms of H, He, D and Li These were formed in the first 3 minutes. For all the other atoms we need stars!! Thank you Fred Hoyle even though you distracted us with the steady state universe you got star evolution right. © M. Bass The formation of stars As the universe expanded turbulences formed as they must. These gave rise to stars and galaxies of stars. The first stars were probably supermassive, lived fast, died young and seeded the next generation. The question we want to address is what does it take to get the kind of stars we need to cook the other atoms that we need to get us. To do so requires a universe with some very special properties. Stars forming in small protrusions from the Eagle Nebula © M. Bass How do stars cook up elements? The first stars were formed by the hydrogen (plus a little helium) gas produced in the Big Bang. Gravity pulled the gas in on itself and collisions heated up the gas. When a certain temperature was reached nuclear fusion began and so called stellar burning got going. The end products of nuclear fusion reactions were higher atomic number elements. © M. Bass Star burning The rate with which a star burns its hydrogen fuel increases with its mass. Massive stars burn up fuel much faster than smaller stars - makes you glad the sun is a very average star, not a giant. In such burning stars can produce all the elements through iron that includes carbon, oxygen, nitrogen, calcium ... © M. Bass The next step To get past iron you must have temperatures much higher than just stellar burning nuclear fusion allows. Thus, to get higher atomic number atoms you must have super novas. So, stars burn, crash, spew out their remains into the galaxy and seed the formation of newer stars. WITH DIFFERENT COMPOSITIONS © M. Bass The next generations So one generation of stars seeds the next and produces new stars containing more than just Big Bang elements. So too does the residue of new star formation. Therefore, so do the planets that form around the stars, and therefore so do we. We are star stuff. Spinning cloud flattening into a disk and condensing into a star and planets © M. Bass What is required? We have pronounced the sequence of events but haven’t explained why it occurs exactly as it must for us to exist. To do this we will employ our knowledge of modern physics - particularly the Standard Model of Modern Physics The current versions of the theories of Quantum Mechanics and Gravitation (You do not have to know quantum mechanics or general relativity to follow this discussion.) © M. Bass Fundamental Constants The Standard Model demands that certain constants be just what they are. We have theories that agree with observation if the constants have certain values. About 20 numbers giving such things as the gravitational constant, the charge on the electron, the speed of light, and etc. If they aren’t, things don’t happen the way we observe that they do. We don’t know why these constants are what they are, just that they have to be what they are. © M. Bass A needle standing upright on its point Why these constants must be exactly what they are is asking why our universe is like a needle standing upright on its point. The random probability that the several of the 20 constants that must have the precise values needed to explain us is unbelievably small. About one chance in 10234 The anthropic view, the one that says ours is a universe designed for our existence, assumes that a God set the values of the constants just exactly right and then let things go. © M. Bass We must have stars so what constants are needed? Stars are made of - protons, neutrons, electrons and neutrinos. They also need photons to balance their energy. These interact through four forces - gravity, electromagnetism, weak nuclear and strong nuclear (in order of increasing strength) Forces are characterized by strength, range and type of particles they affect. Particles participate in forces through coupling constants mass for gravity charge for electromagnetism © M. Bass Gravity It is the only universal interaction. every particle having mass feels gravity. Its range is infinite. Its strength is proportional to the product of the masses that interact. The proportionality constant, G, is incredibly small, in units of proton masses, it is 10-38. © M. Bass The importance of G If this constant were any larger stars would live much shorter times than they do they would not last long enough for us to evolve If this constant were any smaller stars would not collapse, ignite, and fuse H into He and other necessary elements © M. Bass You need nuclear reactions As gravity causes the gases of a star to collapse nuclear reactions must take place without nuclear reactions the internal pressure of the gases can not compete with gravity and the whole mess would collapse immediately into a black hole. For nuclear reactions to proceed as they must to cook up the elements the proton and neutron can differ in mass by only 2 parts in a thousand and the electron must be ~1800 times less massive than the proton © M. Bass n, p, e and n Any larger differences and protons and neutrons would not stick together in atoms under the effects of the weak nuclear force. There would be no atoms, no chemistry, no biology and the universe would be very boring. Neutrinos are particles essential to conserve momentum in nuclear reactions. It turns out that the neutrino mass can not exceed ~10-9 of a proton mass. © M. Bass The scale of the universe The universe must be big enough to accommodate us. To do so the mass density of the universe, must be no larger than 10-40 per m3 in units of proton mass. If it were any larger the universe’s expansion would not have happened. If it were any smaller the universe would have already expanded out of sight. © M. Bass There must be light Electromagnetism is the force that governs the radiation of light. It must be present exactly as it is in order to carry energy away from stars so that stars stay in equilibrium long enough to cook the elements and warm our planet. This balance of gravitational collapse, nuclear burning, and electromagnetic radiation enables stars to last billions of years. © M. Bass e, h and c The demands for electromagnetic radiation to maintain the energy balance of stars requires that the charge on the electron be no more and no less than 1.60217657 × 10-19 Coulombs, Planck’s constant be exactly 6.62606957×10−34 J-sec., and the speed of light be 2.99792458 x 108 m/sec. Any more or less and stars don’t make it. Any more or less and there is no biology. © M. Bass The probabilities if these numbers occurred randomly For the existence of particles with the necessary masses: the proton =1 part in 1019 the neutron =1 part in 1022 the electron =1 part in 1022 the neutrino =1 part in 1027 For the cosmological constant (density of empty space) =1 part in 1060 For the ranges of the forces =1 part in 1080 For the strength of the forces =1 part in 104 © M. Bass Add ‘em up The total probability of all of these numbers randomly being just what they must be to have us is the product of all the probabilities or 1 part in 10234 This is so astonishingly small that we are forced to seek some deeper understanding of how so special a universe could come about. What we have so far is a theory that fixes these numbers so that it agrees with observed facts. What we don’t have is a theory that explains these numbers. © M. Bass Possibilities Some say it is God’s doing. Some suggest multiverses with cosmological natural selection where universes that generate many universes generate universes like themselves. Some suggest simply that in the infinite multiverse, we exist in one universe in which we could exist. Infinity is a big number and in it there are an infinite number of universes just like this one. © M. Bass The Standard Model This is the model of physics in which the very small and the very large are taken together. It has been tested many times and has yet to fail. The Higgs Boson was where it was supposed to be. However, it demands that the numbers be what they are. A suggestion of why arises from String Theory. © M. Bass String Theory In 1984 John Schwarz and Michael Green published a paper in which they showed that by allowing fundamental particles to be tiny vibrating strings, not points, some amazing things could be deduced. The differences between particles was determined by the differences in how the strings vibrated – masses, charge, spin and so on. Most exciting was that one of the vibrating strings had the properties of the graviton – the force carrier for gravity. Maybe string theory could unify gravity and quantum mechanics!!! Before we go on String Theory is just that. No experiment has been suggested that can test it. © M. Bass More work on String Theory To be mathematically consistent it required 11 dimensions. Then it required these dimensions had to have certain shapes that corresponded to the numerical values of the constants in the universe. But, then it turns out there can be an innumerable number of shapes. (In one treatment 10+500.) So if you believe string theory we exist in one of the infinity (very large number) of universes that has the right set of shapes for us to exist in. © M. Bass String Theory and the Multiverse The multiverse is the infinity of universes allowed by string theory. If there are an infinity of universes there are an infinity of universes just like ours. So it is not so surprising that we exist in a universe that allows us to exists. Maybe everything is just good luck and the numbers demanded by the Standard Model or that correspond to some as yet unknown shapes of hidden dimensions in String Theory are really not so unlikely as we think. © M. Bass Final thoughts We have only just begun to have a scientific cosmology based on observation, experimentation and tested theory. This universe is the only one we will ever have so it is the only one we can try to understand. Whatever cosmology we come up with has to include us. © M. Bass