As a New Scientist article relates, NASA’s Cosmic Microwave Background Explorer (COBE) recorded the the cosmic microwave background–the faint afterglow of the Big Bang–across the whole sky for the first time in 1992. It revealed minute temperature variations that were the seeds of the galaxies we see today. Since then, astronomers have mounted more sophisticated detectors on mountaintops and on balloons over Antarctica, to measure those density variations in more detail, but for small regions of the sky. These findings confirmed that the Universe is expanding at an ever-increasing rate.
Now, the MAP probe, nestled in the L2 Lagrange point of gravitational balance between the Earth, Moon and Sun, 1.5 million kilometres from Earth, has measured the cosmic microwave background across the entire sky, with 35 times the resolution of COBE. “We’ve captured the infant Universe in sharp focus, and from this portrait we can now describe the Universe with unprecedented accuracy,” said Chales Bennett of NASA’s Goddard Space Flight Center. Before MAP, the Universe was estimated to be 12-15 billion years old. Now MAP has pinned that age down to 13.5-13.9 billion years.
As for the fate of the Universe, MAP has shown that 4 percent of the Universe is composed of ordinary matter, 23 percent is an unknown type of dark matter and 73 percent is dark energy, a mysterious force that accelerates the Universe’s expansion. It is the predominance of this dark energy in the Universe which guarantees that the universe will continue to expand, ever more rapidly, until the stars eventually fade, and all that remains is a diffuse, cold gas.
Given that we have no good idea what this “dark energy” is, in particular what properties it may have, it’s basically impossible to predict what it will do on time-scales longer than the 10 billion years or so we can see right now. There are still a few too many coincidences (how does it happen to be that dark matter and dark energy are the same order of magnitude? Not something you would really expect, for example, since it should change radically as the universe ages) to be sure the simplest explanation is the right one. Or even what the simplest explanation really is. For example, the “quintessence” proposals seem to allow for oscillations of some sort… anyway, the current acceleration is definitely worrying for anybody who thinks our local group of galaxies is too confining!