How Weird is My Universe?

By now you might be scratching your head in frustration. That’s normal. The universe is easy to explain the less you know. The more you know the weirder things become. Let’s introduce two more central concepts, both of which add immeasurably to the weirdness.

English: Wave particle duality p known (Photo credit: Wikipedia)

The first is complementarity. Recall that there are bosons for carrying forces and fermions that make up matter. Photons carry electromagnetic waves like radio waves, light waves, microwaves, x-rays, gamma rays, etc.  Complementarity says that anything can act like a particle or a wave depending on the circumstances. In one classic experiment, light shines through two narrow slits onto a screen. Interference patters appear on the screen as if the waves of light are interfering like waves on a pond of water. So far so good because electromagnetic radiation is thought of as a wave and that behavior is expected in waves. But if the light source is turned way down so that the light escapes one photon at a time the interference patterns still show up, as if the photon passes through both slits and interferes with itself. Richard Feynman, one of the 20^th century’s leaders in quantum theory, said if you can explain this, you understand quantum mechanics. Then he added, “no one understands quantum mechanics.”

A second concept is the uncertainty principle. This was developed by Werner Heisenberg and bears his name as the Heisenberg Uncertainty Principle. It states that the mere act of observing something at the subatomic level changes its properties.

Think of what happens when we see something. Light reflects off whatever we are looking at, hits the retina in our eyes and is transmitted as an image by our brain. Similarly, when we observe something at the subatomic level, a wave of some sort reflects off the thing and makes an image that can be detected by highly sensitive equipment.

In order for something to reflect back an electromagnetic wave so that it can be detected the wavelength has to be much smaller than the object. That’s why police “radar guns” don’t really use radio waves; they use microwaves. Radio waves are much too long to give a good image of a car.

Electromagnetic waves of whatever wavelength carry energy. The longer the wavelength the less energy the wave has; the shorter the wavelength the more energy it has. So a radio wave, with a wavelength of one to several meters, has less energy than a light wave, which in turn has less energy than x-rays or gamma rays.

When a light wave hits a car some of its energy is transmitted to the car. Because the car is so massive and the energy of the light so small in comparison, there is no discernible effect on the car.  But when we start trying to “see” subatomic particles using very short wavelength electromagnetic waves the energy of the wave is enough to affect the particle. As soon as the wave hits the particle, it is no longer in the same position but has moved, simply because we “looked” at it. Thus we can never be certain of a particle’s position. All we can do is express its position in terms of probabilities as to where it might be.

Complementarity and the uncertainty principle are linked. Particles have a definite position while waves have a definite direction and momentum. Since anything can exhibit both “particleness” and “waviness” at the same time, trying to observe anything changes one or the other of these properties. When we determine the position, it comes at the expense of knowing its direction and momentum and vice versa.

Einstein was frustrated by this lack of certainty, which led to his famous statement that God does not play dice with the universe. However, quantum mechanics is nearly a century old and has stood the test of time. The universe is governed by probabilities, like it or not. Nothing is real until it is observed. An electron is a wave of probability until it is observed, at which time it collapses into a finite reality.

What is Stuff Made Of?

The Standard Model starts out with this simple question: what is stuff made of?  Until about 100 years ago the answer would have been “atoms.”  The very word atom comes from a Greek word meaning “indivisible.”  Scientists thought atoms were the solid building blocks from which everything else was made.  Ernest Rutherford and others showed that atoms are mostly empty space.  There was a dense nucleus made up of protons (positive electric charge) and neutrons (neutral), surrounded by the cloud of negatively charged electrons.  For a time protons, neutrons and electrons were considered fundamental particles, indivisible any further.  Then in the 1960s “atom smashers,” machines that accelerate particles to extremely high speeds and smash them into each other, showed that protons and neutrons were composed of partially charged particles called quarks.  There was also a weightless particle called a neutrino that could pass through thousands of miles of solid iron without slowing down.  But things were still fairly simple.  There were quarks, electrons and neutrinos. Quarks are incredibly tiny.  If an atom was the size of the Earth, a proton would be a football stadium and a quark would be a tennis ball.

In the next decade, more powerful particle accelerators, capable of accelerating particles to near light speed, demonstrated hundreds of fundamental particles.  All seemed to fall into one of 12 categories of fermions, depending on their mass.  The lowest level of fermions contains normal matter:  up and down quarks, electrons and neutrinos.  The next two levels contain fermions that exist only fleetingly in particle accelerators.  Each of the 12 fermions has a corresponding antiparticle that can only be created with a sufficiently energetic collision.

English: Standard model of elementary particles: the 12 fundamental fermions and 4 fundamental bosons. Please note that the masses of certain particles are subject to periodic reevaluation by the scientific community. The values currently reflected in this graphic are as of 2008 and may have been adjusted since. For the latest consensus, please visit the Particle Data Group website linked below. (Photo credit: Wikipedia)

As a counterpart to fermions there are four bosons that carry all forms of energy.  Photons carry electromagnetic energy (light and all other wavelengths of electromagnetic radiation). W and Z bosons carry the weak force, which gives rise to radioactivity; and the strong force that binds atomic nuclei together.  Finally there is the hypothetical graviton that carries the force of gravity.  The graviton has never been observed.

The theoretical framework that describes the 12 fermions and four bosons is called the Standard Model. The Standard Model does for particle physics what Newtonian physics first did for the observable world (the world we live in) and General Relativity did for the cosmos. It explains what we see. The Standard Model predicts that the four fundamental forces, which vary greatly in their strength, will be unified at sufficiently high energy. This prediction was partially proven in the 1970s when the electromagnetic and weak forces were unified. Like Newtonian physics and General Relativity, the Standard Model is incomplete. It fails to explain why there are three levels of quarks and light particles. It leaves open the possibility that quarks may be further divisible. For a time scientists theorized another boson called the Higgs boson that gives all other particles their mass in order to preserve the Standard Model.  In July 2012 scientists using the Large Hadron Collider at CERN discovered the Higgs boson. This gave a huge boost to the Standard Model, which some felt had outlived its usefulness.

Why is this important to us? Let’s revisit the Big Bang. One millionth of a second after the explosion the universe is about the size of our solar system and is as dense as air. It’s 10,000 times hotter than the core of the sun. Particles and antiparticles appear, collide and annihilate each other at a staggering rate. By ten millionths of a second after the Big Bang expansion has cooled the universe to the point that particles and antiparticles can no longer form from the radiation. The number of particles and antiparticles is fixed and they begin a war of mutual extermination. By 100 microseconds, a twentieth of the time it takes a bee to flap its wings, it’s all over. All the particles and antiparticles have paired up like guys and gals at a dance. There are no wallflowers. All matter is extinguished and the universe contains only radiation.

But wait, you say. That would be the “nothing” universe and we already know there is “something” because we’re here to wonder how it all began. And you would be right. For some unknown reason the symmetry between matter and antimatter wasn’t perfect. It was off by one part in a billion. For every billion antiparticles there were a billion and one particles. When the last particle of antimatter paired with a particle of matter there were a billion photons for every particle left, and no antiparticles. The photons continued to spread out to be discovered billions of years later as cosmic microwave background radiation and the remaining particles combined under the force of gravity to become 100 billion galaxies, one of which contains a very ordinary star around which eight planets revolve, one of which we call home.

How big is one part in a billion? Imagine someone has laid out pennies over an area three miles on a side. All pennies show heads except one. That one penny showing tails is the one particle of matter left after the billion pennies showing heads were annihilated by another billion pennies showing tails.  It’s from those leftover tails that the universe is made.

Why is There Something Rather than Nothing?

This question has puzzled philosophers for at least 300 years, ever since Gottfried Leibniz wrestled with it.  Leibniz postulated that “nothing” was a simpler state than “something;” therefore it was natural that there should be nothing.  However, since there is something (because, if there were nothing, he and we would not be here to ask the question), there must be a creator in there somewhere.  With the current state of humanity, some would argue that Leibniz’s value judgment that something is better than nothing, old Gottfried was on to something (no pun intended).  His question is profound and poses a challenge for deists and atheists alike: the necessity to explain creation out of nothing.

Let’s take a closer look at the “something.”  You can get something in two flavors, light (radiation) and matter.  In physics, light and matter “particles” are called bosons (light) and fermions (matter) after the two scientists who described their properties statistically (we will soon see that nothing is real, it is just a matter of probability).  Fermions are aloof and individualistic.  In terms of their probability, no two fermions are exactly alike.  Bosons, on the other hand, are promiscuous.  Bosons are the carriers of all the forces in nature.  Photons, which carry light, can have the same energy and occupy the same space.

The universe has far more bosons than fermions and this discrepancy bothers physicists.  After all, what little matter (fermions) there is was enough to make billions of galaxies and stars.  Now if the number of fermions is only a small fraction of the number of bosons, imagine how many bosons (or, how much energy) there must be.

In addition to this puzzle, in the 1920s Paul Dirac, an English physicist working on the new theory of quantum mechanics, made a prediction for the existence of antimatter.  Dirac solved the fundamental equation that explains the behavior of the electron and found two solutions.  One solution involved the square root of a positive number, the other included the square root of the same negative number.  Generations of college calculus students have grappled with this notion of the square root of a negative number, since any two numbers that are either both positive or negative, when multiplied together yield a positive number.  In mathematics there is the imaginary number i, which is the square root of negative one (i x i = -1).  Many math problems have these two solutions, one real and one imaginary, but when it comes to “real world” solutions, the imaginary solution is usually discarded.  Rather than discard it, Dirac left it in his paper.

Four years later Carl Anderson was watching cosmic rays in his cloud chamber.  A cloud chamber is where scientists can observe particles interact with a supersaturated vapor.  By applying a magnetic field to the chamber the particle can be made to curve.  The vapor trail left by the particle registers the passage of the particle.  Anderson was observing electrons and noticed that, while most of the vapor trails curved in the expected direction, a few curved in the opposite direction.  This meant that a few particles had the same mass as electrons but had the opposite charge, positive rather than negative.  Anderson called these “positrons” for positive electrons.  In the context of Dirac’s work, positrons are the particles predicted by the solution to the problem that involves the imaginary number.

Paul Dirac (Photo credit: Wikipedia)

It turns out that the existence of antimatter is far less than the existence of matter, which is a good thing.  If the number of fermions of the antimatter variety were roughly equal to the number of fermions of the matter variety, it is likely there would be “nothing” rather than “something.”  While this difference should be comforting to us in the sense that we need not fear being annihilated by our antimatter counterpart, to scientists this discrepancy is troubling.

In terms of Einstein’s E = mc² that shows how energy and matter are interchangeable, matter and antimatter are on equal footing.  Quantum theory predicts that every particle has an antiparticle.  But antimatter particles don’t survive very long while matter particles do.  In Dan Brown’s novel Angels and Demons, the bad guys steal half a gram of antimatter and high-tail it to Rome to make a bomb.  The mark of good fiction is to cause “the willing suspension of disbelief,” that is, to make the reader willing to ignore the little voice in her head that says “that would never happen.”  By that criterion, Brown is a master of fiction because his premise, that half a gram of antimatter could exist, is outrageous.  At current production rates it would take 10 million years to create half a gram of antimatter.  The cost to create one-billionth of a gram of antimatter is about a billion dollars.

To understand particle physics and the extreme rarity of antimatter we need to understand, at least a little bit, what physicists call the Standard Model.  To do this, we have to lay some groundwork that includes a Laplace transformation of a Calabi-Yau manifold across a chronosynclastic infindibulum.  I made that last part up but that’s the kind of language particle physicists speak.

Projection of a Calabi-Yau manifold, one of the ways of compactifying the extra dimensions posited by string theory (Photo credit: Wikipedia)