by Cate Montana

The nature of the void, the nature of emptiness is just teeming, brimming with unmanifest energy.

John Hagelin

WTB – 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 weight 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. A little bit like hidden sector matter does but for different reasons. 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.

WTB – 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.

WTB – 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.

WTB – 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.

WTB – 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. The reason it’s accelerating and it’s expansionist is because for a while, including today, we have this expansionary influence from the dark energy, and we also have an attractive influence from the sun and the stars and the galaxies. Matter is attractive, even so-called energies like light are gravitationally attractive. Only this completely unmanifest, transcendental dark energy is gravitationally repulsive. So until now the universe has been held together, so to speak, by its matter. But the universe is expanding still. And the matter is going to get more and more diluted as the space stretches and the stars are slowly pulled apart and the galaxies become few and far between. And all that will really be left, eventually, is just the dark energy which continues to eternally pervade space and time.

So when that force takes over completely, the universe will expand and expand at an ever accelerating pace to the point where our planets are torn apart, our cells are ripped apart, our molecules are torn apart, our atoms are torn apart, the nuclei are torn apart, and protons and neutrons within the nucleus get ripped apart, the quarks within our protons and neutrons get ripped apart. That will be the extraordinary rate of acceleration of the expansion of space. So dark energy is quite a mysterious thing.

The most mysterious thing about it for me as a quantum cosmologist, is that it exists and yet is so small. I don’t want to understate this mystery.

If something exists at all, then it can be very difficult to understand why it could be so infinitesimally small. And that’s a long argument that would take a while to develop. But it’s a genuine mystery. Let’s put it this way. The natural scale of these vacuum fluctuations is much, much greater. For example, the calculable jitterbugging, the calculable zero point energy, the calculable vacuum fluctuation energy from a bose field like the photon of electromagnetism - any one field - is rather large. Those fluctuations really are so large that the gravitational influence of those could tear the universe apart immediately, one would naively calculate. And at the same time, if you throw the photino into this calculation and calculate the quantum fluctuation energy of the photon supersymmettric partner, the phototino, it’s also enormous, but it has the opposite sign of the photon’s vacuum fluctuation energy. And the two contributions tend to cancel. That is a clue as to why the total vacuum energy is really such a small effect in the world today. You could have a cancellation due to supersymmetry between all the bosons of the universe that contribute to this energy with a positive sign, and all the fermions in the universe that contribute to this dark energy with a negative sign, and you would achieve a cancellation between these large positive and these large negative contributions, which if it were exact cancellation, which is mathematically possible, would explain why dark energy wasn’t discovered long ago.

However the cancellation – if the cancellation is not exact - it’s a real mystery to understand why it is almost exact, leaving such a small predominance of leftover dark energy that the universe has survived to this date. So these are kind of heady things and they’re a little bit difficult to describe.