Launched in November 1989, NASA’s Cosmic Background Explorer (COBE) took precise measurements of radiation across the sky. The mission operated until 1993.
Although NASA’s Hubble Space Telescope is probably best known for its astounding images, a primary mission was cosmological. By more accurately measuring the distances to Cepheid variables, stars with a well-defined ratio between their brightness and their pulsations, Hubble helped to refine measurements regarding how the universe is expanding. Since its launch, astronomers have continued to use Hubble to make cosmological measurements and refine existing ones.
Thanks to Hubble, “If you put in a box all the ways that dark energy might differ from the cosmological constant, that box would now be three times smaller,” cosmologist Adam Riess of the Space Telescope Science Institute said in a statement. “That’s progress, but we still have a long way to go to pin down the nature of dark energy.”
NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) was a spacecraft that operated from 2001 to 2010. WMAP mapped tiny fluctuations in the cosmic microwave background (CMB), the ancient light from the early universe, and determined that ordinary atoms make up only 4.6 percent of the universe, while dark matter makes up 24 percent.
“Lingering doubts about the existence of dark energy and the composition of the universe dissolved when the WMAP satellite took the most detailed picture ever of the cosmic microwave background,” said cosmologist Charles Seife in the journal Science.
The European Space Agency’s Planck space mission ran from 2009 to 2013 and continued the study of the cosmic microwave background.
The ESA is currently developing the Euclid mission, which should fly by the end of the decade. Euclid will study dark matter and dark energy with greater precision, tracing its distribution and evolution through the universe.
“At the heart of the mission is one of the billion pound questions of physics,” the ESA’s David Parker said in a statement.
Common cosmological questions
What came before the Big Bang?
Because of the enclosed and finite nature of the universe, we cannot see “outside” of our own universe. Space and time began with the Big Bang. While there are a number of speculations about the existence of other universes, there is no practical way to observe them, and as such there will never be any evidence for (or against!) them.
Where did the Big Bang happen?
The Big Bang did not happen at a single point but instead was the appearance of space and time throughout the entire universe at once.
If other galaxies all seem to be rushing away from us, doesn’t that place us at the center of the universe?
No, because if we were to travel to a distant galaxy, it would seem that all surrounding galaxies were similarly rushing away. Think of the universe as a giant balloon. If you mark multiple points on the balloon, then blow it up, you would note that each point is moving away from all of the others, though none are at the center. The expansion of the universe functions in much the same way.
How old is the universe?
According to data released by the Planck team in 2013, the universe is 13.8 billion years old, give or take a hundred million years or so. Planck determined the age after mapping tiny temperature fluctuations in the CMB. “Patterns over huge patches of sky tell us about what was happening on the tiniest of scales in the moments just after our universe was born,” said Charles Lawrence, the U.S. project scientist for Planck, in a statement.
Will the universe end? If so, how?
Whether or not the universe will come to an end depends on its density — how spread out the matter within it might be. Scientists have calculated a “critical density” for the universe. If its true density is greater than their calculations, eventually the expansion of the universe will slow and then, ultimately, reverse until it collapses. However, if the density is less than the critical density, the universe will continue to expand forever.
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