by Mary Avant

For starters, dark matter is physically undetectable. You can’t see dark matter, touch it, or measure it – yet. While elusive, dark matter and dark energy are currently believed to constitute up to 96% of our universe – a stunning concept. The beautiful night sky, with stars twinkling on a backdrop of “empty space” above us, is apparently a vision that may soon have to be radically revised.

Swiss astronomer Fritz Zwicky deduced the existence of dark matter over 70 years ago as an explanation for the inexplicable, yet powerful, gravitational pull that seems to bind clusters of galaxies together. In seems there just isn’t enough matter in the universe to account for the gravitational effects that are seen. In addition to holding the galaxies clumped together, dark matter may well be the reason that stars and constellations and galaxies formed in the first place. Without the gravitational boost of dark matter, some scientists speculate that the hot gases that were created in the Big Bang would never have coalesced to form regular matter in the first place.

In August 2006 NASA announced that a study of the collision of two distant galaxies has now provided solid proof that dark matter does indeed exist. But knowing it exists doesn’t mean anybody has a handle on what it really is or how it manifests. Physicists are now arguing whether the “cold dark matter” they’ve been searching for is really “hot dark matter.” And apparently a recent discovery of a potential link between dark matter and the nature of the Big Bang indicates that dark matter may satisfy the Second Law of Thermodynamics while Cold Dark Matter cannot. But hot or cold, it’s still a mystery to most of us. To help the layperson out, here is a brief interview with former CERN physicist Dr. John Hagelin about the nature of dark matter.

TGI – So what is dark matter?

JH – Dark matter is matter. They are massive particles and let me pause to say, everything is relative. So when I say massive, I still mean very light in comparison to a grain of salt. I mean a massive particle that will weigh several times the proton mass. So dark matter consists of massive particles that weigh, perhaps, several times the proton mass, but are dark because they only interact weakly with ordinary matter.

Dark matter is electrically neutral and therefore is immune to the force of electromagnetism; is transparent with respect to light. Dark matter does not participate in the nuclear force either, and is immune to nuclear forces and nuclear interactions of matter. It only interacts therefore, by process of elimination, via the weak force or radioactive force, or gravity. Under most circumstances gravity is irrelevant, and the principle means of interaction between dark matter and normal matter is therefore via the weak radioactive force. And that’s pretty weak. For that reason you could take a piece of dark matter, just as a neutrino is a normal type of matter that interacts only weakly, and this type of matter can drift through solid lead for centuries without interaction. It will eventually bump into it, but it takes a long time because its interaction is that weak. And it’s dark in that it doesn’t shine, it doesn’t twinkle like light.

TGI – If we can’t see it, or interact with it, how do we know it exists?

JH - There are several reasons we know dark matter exists. One is purely theoretical. Today’s unified field theories based on the superstring, and even previous unified field theories, require the principle of supersymmetry. Supersymmetry is a symmetry principle, in nature, of a bizarre type; one that was only proposed about 20 years ago.

Supersymmetry says that for every particle of any given spin type, let’s say the spin 1 photon, (a photon is an elementary particle of light and has an intrinsic spin equal to one unit of Planck’s Constant). That particle will have a mirror particle, or so-called super-symmetric partner of a different spin. In this case a spin ½ photino. A spin 1 photon, by the way, is a boson; a spin ½ photino is a fermion. Because integral spin 1 particles: spin 0, spin 1, spin 2 are called bosons; Half integral spin particles, like spin ½ and spin 3/2 are called fermions. And bosons and fermions have such fundamentally different properties that we give a name to one major category, a boson, and the other major category fermion. And never the twain shall meet. And they really have diametrically opposed properties.

Therefore it was radical to suggest there might be some unifying principle that could link a fermion, like a spin ½ photino, to a boson, like the spin 1 photon, of electromagnetism. But such a symmetry does exist. And that would predict that for every type of particle we know, including the photon, the graviton etc., there will be a mirror particle with a different spin. Bosons will have a fermionic mirror particle; fermions will have a bosonic mirror particle and the photon, for example will have a photino mirror particle. We haven’t found one yet. They’re a little too heavy to have been produced in the laboratories so far. But we expect to produce these supersymmetric particles in the relatively near future in the laboratory. And that will be a spectacular confirmation of this unifying principle of supersymmetry that unites diametrically opposite types of particles and forces in nature.

I went into that simply to point out that we are relatively confident that photinos exist. And if they do, they would have been produced in the Big Bang and will continue to survive from the Big Bang, as leftover relics. And there will be lots of dark matter out there; matter that we don’t see because it’s dark and weakly interacting. But matter which, it turns out, has very important astro-physical and cosmological effects.

TGI – Why important?

JH – Dark matter is important because it is far more prevalent in the universe in terms of its mass, than normal matter. There’s probably 20 times, 10-20 times as much dark matter in terms of the total mass of the universe in comparison to normal matter. And that makes it very important gravitationally. In fact, now that we understand it, it’s the dark matter that seeds galaxy formation. Dark matter, being the majority of the mass of the universe, starts to clump first, starts to gravitationally self-attract; gravitationally coalesce. So we have dark matter galaxies, which are really just big lumps of dark matter. And on the basis of that gravitational lump, normal matter stars start to also get gravitationally attracted and coalesce to form the galaxies that we see. So the dark matter clumping seeds galaxy formation. And galaxies today, when you look out into the sky, what you’ll see is the observable matter in the form of luminous stars mostly – plus a few black holes. But surrounding these normal galaxies like a big halo will be this, what’s called, dark matter halo which comprises about 90%, maybe even 95% of the mass of the galaxy. And that’s got to be there, or A) the galaxies wouldn’t have formed as early as they did; and B) because their continued presence, these dark matter haloes, affect today the orbital dynamics of galaxies, in particular the orbits of the stars around the galactic core. And the presence of this big surrounding halo of dark matter changes the gravitational dynamics of the orbits of the stars in predictable ways and allows us to understand things like why stars orbit the centers of their galaxies at the rates they do.

TGI – So what is dark energy and how does it differ from dark matter?

JH – Dark energy is the most mysterious category of all, even more mysterious really than hidden sector matter. Dark energy really consists of vacuum fluctuations, which means it is a completely unmanifest, transcendental form of matter/energy. Devoid of physical content in that there are no particles whatsoever associated with it; no forces associated with it. It is present in a pure vacuum. And it is, in essence, the energy of vibration of emptiness; the energy of the quantum fields fluctuating in a completely unmanifest way. Sometimes this is called zero point energy. Sometimes it’s called the zitterbewegung – jitterbugging you could say - of the abstract quantum fields in vacuo. So it’s a completely transcendental, unmanifest form of energy and matter which you wouldn’t think, intuitively, should have anything to do with the world of manifest matter.

TGI – Would you say dark energy would correlate to the Void of Biblical terms?

JH – Yeah. It’s the fabric of the Void. It’s the irremovable liveliness, or dynamism, within the abstract Void. But amazingly, according to Einstein’s equations, he debated whether or not to include this term in his general relativistic field equations, because although logically plausible, the term made little intuitive sense to Einstein that pure emptiness could have a physical impact on the physical universe. But, nevertheless that term – there is a term – in Einstein’s general relativistic field equations governing gravity which says that this completely, unmanifest transcendental form of matter/energy, of dark energy, that has an influence not directly upon matter, but upon gravity - upon the curvature of space. Gravity really is just a side-effect of the curvature of the space/time geometry in which we live.

So the presence of these abstract, unmanifest, transcendental fluctuations is to produce an influence on gravity – space/time curvature – of a particular, predictable type. And that influence is one of gravitational repulsion of space. Let’s call it the gravitational self-repulsion of space, causing space to expand away from itself at an exponentially increasing speed. Very similar to what happened in the early universe during in the so-called inflationary epoch. And it refers to the first billionth of a second of the universe where the universe rapidly emerged and underwent a process of exponential runaway inflationary expansion.

So that same influence present in the early universe in this so-called inflationary epoch is still there today, because these vacuum fluctuations, this energy of the Void, has never gone away and continues to cause the universe to expand away from itself; and in principle will continue to expand and accelerate in its expansion forever.