Another Nobel Prize will go to the physicist who figures out why the ratio of the electromagnetic force to the gravitational force has no room for error. It must be accurate to one part in "forty tens" or there would be no star formation. It must be mathematical in some sense, because it is as precise as numbers like pi and e, the base for natural logs.
Which brings us to yet another example. The electron also enters into the tightrope act needed to produce the heavier elements. Because the mass of the electron is less than the neutron-proton mass difference, a free neutron can decay into a proton, an electron, and an anti-neutrino. If this were not the case, the neutron would be stable and most of the protons and electrons in the early universe would have combined to form neutrons, leaving little hydrogen to act as the main component and fuel of stars.
Continuing, after the discovery of dark matter and dark energy, scientists realized that ordinary matter amounted to only about 4% of the total. When they add up all the matter, however, they find that the actual density of the universe is very close to what is known as the critical density. This means that, to an accuracy of 1%, our universe happens to be what cosmologists call "flat," which means there is neither positive nor negative curvature.
http://www.site.uottawa.ca:4321/astronomy/index.html#flatuniverse
Dark Matter is known to be 23% of the universe, and there are several candidate particles, including the lightest super symmetric particle. Dark energy constitutes a whopping 73% of the universe, and its explanation will garner another Nobel Prize. It is credited with making our universe expand faster and faster, which may or not be a good thing. It might also have caused "inflation" during the first fraction of a second, which we discuss later.
This topic is red hot in physics and there is frequent news. To date they know that the current acceleration began about 5 billion years ago, and so Dark Energy might be something that comes and goes. Constructing normal physical laws for something this fickle causes physicists to scratch their heads.
http://en.wikipedia.org/wiki/Dark_matter
http://en.wikipedia.org/wiki/Dark_energy
http://map.gsfc.nasa.gov/universe/uni_matter.html
http://www.wired.com/science/space/news/2005/02/66487
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