Last week, the science media was abuzz with reports that dark energy might not exist.
The astrophysics community has largely rejected the study behind the headlines, which argues the original evidence behind dark energy is flawed. This latest dark energy kerfuffle doesn’t necessarily reveal a problem with the physics, but it does reveal the widening gulf between what our theories say the universe should be and what we actually observe.
The universe needs dark energy, the enigmatic substance that accounts for nearly 70 percent of the total energy in the cosmos and causes the universe to expand at an accelerating rate, to explain one of the most surprising discoveries of the 20th century. Two separate 1998 studies of distant supernovas found that the universe was not just expanding but that the expansion was actually accelerating, with three of the physicists involved winning the 2011 Nobel Prize for their efforts.
But that discovery didn’t fit with our understanding of gravity, which should very gradually begin to pull the matter in the universe back together. There needed to be something previously unknown that was resisting gravity and speeding up cosmic acceleration, and that something is dark energy. It could be something hardwired into the fabric of the universe – what’s known as the cosmological constant – or it could be an as yet undetected force or substance. Whatever it is, dark energy defies easy explanation.