Dark Energy

It’s been almost a century since astronomers discovered that the universe is expanding — a result of the Big Bang in which it was born. But the details of that expansion are still being uncovered. In particular, astronomers are studying a phenomenon that appears to make the universe expand faster as it ages. It’s known as dark energy, and figuring it out is one of the great challenges of modern-day physics.

Astronomers discovered dark energy by measuring the speeds at which distant galaxies are moving away from us. That allowed them to plot how fast the universe was expanding at different times. They expected to find that the expansion rate was slowing down — the result of the gravitational pull of all the galaxies and dark matter.

Instead, they found that things are actually speeding up — the universe expands faster as time goes by.

So far, the cause of that faster expansion is still a mystery. Dark energy could be caused by an energy from the vacuum of space itself. It could also mean that our understanding of gravity is wrong — or at least incomplete. Or there could be some other explanation.

Several experiments are studying how the universe is expanding to try to solve the mystery. That includes a project at McDonald Observatory. HETDEX — the Hobby-Eberly Telescope Dark Energy Experiment — is measuring galaxies that are billions of light-years away, when the universe was young. We’ll have more about that tomorrow.

Script by Damond Benningfield