Monday, August 2, 2010

9) Dark Matter: Distribution of Matter

In actuality, speculation about the origins of the Universe is very often speculation about the origins of matter. The Big Bang tracks everything back to a singularity – a single theoretical point where everything that is today, at one time existed in a condensed, ethereal state, which eventually exploded and evolved into the Universe as it is now. Given our observations and reflections on the Universe, this theory seems almost, but not quite reasonable.

First, the Big Bang is essentially targeted at two fundamental and hereto unexplained features of the Universe; 1) that it is expanding and 2) that there seems to be no other reasonable explanation of its origins. Beyond these two conditions, which the Big Bang seems particularly well suited to explain, are other observations that it doesn’t address quite so elegantly.

One of the biggest problems with the Big Bang is the distribution of matter. Deep space astronomy has revealed that there is a remarkably even distribution of galaxies in the Universe, which on first blush, seems to support the notion of a Big Bang. But this first impression quickly breaks down.

Although the galaxies are very evenly distributed, matter as a whole certainly is not. The fact that matter tends to coalesce into galaxies rather than more evenly cover the emptiness of space is inexplicable in terms of the Big Bang (discounting Dark Matter, of course). Given that there appears to be only about 30% of the required matter in a typical galaxy to account for the fact that it has formed at all (as opposed to simply melting into an indistinguishable haze of hydrogen), raises the question of why they exist. Why isn’t space simply filled with a huge cloud of hydrogen rather than well formed galaxies?

Most of us are acquainted with Albert Einstein’s famous equation, E = mc2, which expresses energy/mass equivalence (more specifically, that the mass of a body is a measure of its energy content). From the launching point of this known formula of nature, physicists have constructed many other theories that have unlocked far reaching areas of natural science, from helping explain the inner workings of the sun's nuclear furnace to constructing the nuclear bomb (some contend that this is not true, but I find it difficult to believe that the principles of conservation of mass and energy did not play a large role here). Indeed, this single equation has proven foundational to much of what we have come to understand about the Universe in which we live.

The underlying premise of this equation is that the Universe contains a fixed amount of matter - whether that matter happens to take the form of mass or energy at a given point in time is, in many respects, irrelevant. The implications of this are somewhat astounding, even to those of us who have long been familiar with them. Even the speed of light as the cosmic speed limit, which on surface appearances seems to be far removed from this equation, is inexorably linked – bound by the implication that the closer in velocity any mass comes to reaching the speed of light, the more of that mass is necessarily converted to energy. So, we are left with an unfortunate speed limit that seems disproportionately slow in comparison with the otherwise huge scale of the Universe.

Special Relativity asserts that matter is not created or destroyed (conversion of mass and energy), but only changes form between mass (relativistic mass) and energy (relativistic energy) . All of this matter, it is presumed, was present in a difficult-to-understand state within the singularity that preceded the Big Bang. And, although the equation, E = mc2 has been proven within the realms of matter (with some caveats), it makes no attempts at explaining where mass and energy first came from.