Astrophysicist Kris Sigurdson explains dark energy, one of the great mysteries of the universe
Up to 70 per cent of the universe is made up of “dark energy,” – a discovery worthy of the 2011 Nobel Prize – but scientists still know precious little about it. Kris Sigurdson, associate professor of Theoretical Physics and Cosmology in UBC’s Department of Physics and Astronomy, discusses how the study of dark energy could provide a more complete portrait of the universe.
What is dark energy?
Dark energy is a cosmic mystery. In 1998, cosmologists–to their surprise–discovered that the expansion rate of our universe has been increasing over time. Matter attracts other matter due to gravity and can act only to slow down, not speed up, the expansion rate. Presently, all evidence indicates dark energy is empirically consistent with a “cosmological constant,” an exotic substance first proposed by Einstein that reacts like a material with a large negative pressure and makes space expand at an ever-increasing rate.
Why is dark energy important in helping us understand the universe?
Recent cosmological data has made it clear that the atoms of the periodic table – the matter we and everything we see in the universe is made of – only account for 5 per cent of material in the universe today. Invisible dark matter is thought to make up 25 per cent, and the remaining 70 per cent appears to be dark energy. In short, our understanding of the universe is fundamentally incomplete.
Theoretical estimates of the density of cosmological-constant dark energy are monumentally incorrect – by a factor of 10^120. Yet the exact same theoretical framework, quantum field theory, makes astoundingly precise predictions for the behaviour of all known elementary particles from the everyday electron to the recently discovered Higgs boson. This may suggest a profound gap in our knowledge of gravity on cosmological scales, quantum mechanics, or both and there is no telling what bridging this gap may bring us.
You’re part of a team building CHIME, Canada’s largest radio telescope, to study dark energy. What do you expect to learn?
With CHIME we plan to map the universe in three dimensions and measure how fast it has been expanding over its history. We hope this measurement will be able to reveal new experimental facts about the properties of dark energy, and light the way towards a better understanding of this mystery.