All that we can see, regardless if it is with our own eyes on Earth or throughout space using our telescopes, all of it is made up of just three subatomic particles – protons, neutrons and electrons. Combined, they form the atoms of the plants and animals, oceans, mountains and deserts, the planets, stars and even galaxies. These however form only a miniscule part, around 5%, of the total mass of the universe. Everything else is one of the biggest mysteries surrounding modern science.
At the end of the last century scientists stumbled on a remarkable and unexpected discovery. Everyone used to think that because of the gravitational pull of all of the objects in the universe, the rate at which it was expanding would eventually slow down and, at some point in the distant future, collapse back together. However, when they went out to measure exactly how much was this deceleration, they discovered exactly the opposite. The universe was actually expanding, and the rate was accelerating. Unable to find a reasonable explanation, scientists came up with three different theories: the first one revolved around an older version of Einstein’s gravitational theory, where he included a “cosmological constant” – a strange, unexplainable force counteracting gravity. The second assumed the theory of gravity was wrong altogether. And finally, some assumed that there is some kind of energy filling up the empty space like a fluid. They called this dark energy. Nobody really knows where this strange force comes from. Some think it may be a fifth fundamental force, called quintessence. Others, that it may be a result of the quantum theory, where all of space is constantly filled with particles, which flicker in and out of existence and that they may in some way influence gravity. Or that it may be an unknown property of empty space altogether. In any case, as the universe expands, its effect seems to be increasing.
As strange and powerful as dark energy appears, it does not explain all of the weird effects of gravity that we know of. Another strange behavior that doesn’t fit our current models revolves around our galaxies. According to physics, the stars at it outer edges should be spinning much slower than those near the center. This however isn’t what we have observed so far – stars seem to orbit at the same speed, regardless of their position. As yet, this could only be explained by the gravitational effect of an invisible halo of mass surrounding our galaxies. This same gravitational pull could explain why the light from even more distant objects appears to bend in places where it shouldn’t. Scientists have named this dark matter and by current estimations it makes up around 25% of our universe, leaving the rest 70% as dark energy.
One of the fundamental assumptions about dark matter is that it moves much slower than normal particles. According to this theory, there should be clumps of dark matter in all sorts of sizes, however until now there were no evidence of any small concentrations in the universe. That is until last week, when astronomers from UCLA and NASA presented the first such discovery. During observations of distant quasars – regions around black holes, which emit massive amounts of light, they detected distortions, indicating the presence of dark matter with mass of only 1/10,000th to 1/100,000th that of the Milky Way’s own dark matter halo.