Granted, it might not seem like such a big deal when astronomers find some of the missing mass in the universe, since there's very little that isn't missing. Roughly 95 percent of the cosmos is either dark matter or dark energy. About five percent of the universe is made up of the normal mass we're familiar with—baryonic matter. Yet by adding up the known stars and galaxies and gas, astronomers have only accounted for about half of that five percent.

Not much in science is more of a mind-bender than thinking about the size and fate of the known universe (except for quantum mechanics and string theory, which also has a lot to do with the size and fate of the universe, albeit on the opposite end of the size spectrum). When we first developed theories about the universe, the model which resulted depicted all of space as static and unchanging, infinite in depth in any direction. Then Einstein posited general relativity and suddenly a whole host of universes were theoretically possible: static, dynamic, infinite, and finite.

Today marks the 18th anniversary of the launch of the Hubble Space Telescope, and to celebrate, NASA has released a collection of 59 new Hubble images (under the fantastic title "Galxies Gone Wild!") that present galaxies in all of their volatile wonder.

Ultra-high-energy cosmic rays carry more energy than any known particles in the universe, so we should probably all take it as good news that scientists have confirmed that they don't originate in our cosmic neighborhood. In fact, the majority of these rays—which are mostly hydrogen and helium—lose most of their juice on their way towards Earth because they interact with the cosmic microwave background radiation, the energetic leftover of the Big Bang.