Starts With A Bang

Ask Ethan: How sure are we that the Universe is 13.8 billion years old? (Synopsis)

If you look farther and farther away, you also look farther and farther into the past. The farthest we can see back in time is 13.8 billion years: our estimate for the age of the Universe. But is it correct? Image credit: NASA, STScI, and A. Feild.

“Normal science, the activity in which most scientists inevitably spend almost all their time, is predicated on the assumption that the scientific community knows what the world is like.” -Thomas S. Kuhn

For all of human history, the biggest questions have fascinated us. Where did the Universe come from? How old is it? And what is its ultimate fate? Once relegated to the realm of theologians, poets, and philosophers, science has brought us closer than ever to the answers. But scientific revolutions have occurred before, in many cases significantly changing the answers to these and other inquiries. How certain are we that this won’t happen again?

The Sun, the Earth, and the history of life on our world all have a consistent age today, but back in the late 1800s, the evidence for the age of the Earth suggested it was significantly older than the Sun. Image credit: NASA, ESA, and ISS Expedition 37.

When it comes to the question of the age of the Universe, presently estimated at 13.8 billion years, there are many uncertainties that could come into play. Dark energy could evolve over time, fundamental constants might not be constant, or today’s fundamental particles might be broken up into smaller components. Additionally, we could have flaws in the expansion rate or composition of our Universe, or even alter General Relativity.

The four possible fates of our Universe into the future; the last one appears to be the Universe we live in, dominated by dark energy. What’s in the Universe, along with the laws of physics, determines not only how the Universe evolves, but how old it is. Image credit: E. Siegel / Beyond The Galaxy.

But it really looks like 13.8 billion years is safe, to within perhaps 2% at most. How can we be so confident? Find out on this week’s Ask Ethan!