Astronomers of the 19th century noticed that the planet Uranus was straying from the orbit predicted by Newton’s laws. The French mathematician Urbain Leverrier suspected that the deviation was caused by the gravitational pull of a previously unseen planet, and he used the same laws to predict where in the sky such a planet should be.
The planet Neptune was thus discovered in 1846, by the German astronomer Johannes Galle. We could argue that this was the first detection of “dark matter” — matter that was not discovered by its light emission, but rather by its gravitational effects.
Applied on a much larger scale — that of galaxies and clusters of galaxies — similar methods allow us to estimate the amount of dark matter present by observing its gravitational effect on visible objects nearby. These methods have revealed that there is at least five times more dark matter than ordinary matter (the stuff that planets, stars, and galaxies are made of) in the universe. Understanding the precise nature of dark matter, which has more gravitational pull on the cosmos than anything else in it, is one of the major goals of modern astrophysics.
No wonder, then, that the Space Telescope Science Institute decided to organize an international symposium on this topic in the spring of 2011. The idea behind these symposia is to bring together researchers in astrophysics, who discovered the existence of the dark matter and can determine its spatial distribution on large scales, with particle physicists, who attempt to determine the nature of the subatomic particles that are thought to be the constituents of dark matter.
After many weeks of deliberations, the Scientific Organizing Committee of the symposium has just about completed an exciting list of invited speakers. It can be seen at:
The topic is currently so “hot” that we can perhaps hope that some major discovery will be announced during the symposium. How galaxies form, what they look like, and the nature of the large-scale structure of the universe all depend on the nature of dark matter and its behavior. Clearly, we cannot get very far without shedding some light on dark matter.