Thanks again for taking the time to post your Stump the Scientist questions on GE’s Facebook page! We had some great questions submitted this week, hope you enjoy this one!
This week, GE’s facbook fan Eli asked, “has evidence of dark energy ever been discovered?
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Response from Chief Scientist Jim Bray:
Yes, Eli, evidence of Dark Energy has been seen. In fact, it was this evidence that caused physicists to invent the term “Dark Energy”. In the standard model of the beginning of the universe, it “exploded” in its beginning in a “Big Bang” around 14 billion years ago. Since all the universe’s parts have gravity, physicists expected that the parts would attract each other as they flew apart from the initial Big Bang, and this gravitational attraction would cause the expansion to slow down over time. Physicists and astronomers can see the speed of expansion by studying the light from distant stars, which is shifted toward the red, with more shift the faster they are expanding away from us; this is called the Doppler shift. Imagine their surprise when they looked at the observed numbers and saw that the speed of expansion is increasing in recent times, not decreasing as expected from the effect of gravity. To explain this observation, physicists postulated a new force pervading all the universe called Dark Energy, which causes the objects in the universe to repel each other and therefore speed up their expansion away from each other. This theory is still somewhat speculative, and the details are still being worked out and checked; other ideas can still be the correct ones.
