The universe is expanding faster than it used to, meaning it’s about a billion years younger than we thought, a Nobel Prize winner’s study said. And that’s sending a shudder through the world of physics, making astronomers rethink some of its most basic concepts.

At issue is a number called the Hubble constant, a calculation for how fast the universe is expanding. Some scientists call it the most important number in cosmology, the study of the origin and development of the universe. Using NASA’s Hubble Space Telescope, Johns Hopkins University astronomer Adam Riess concluded in Astrophysical Journal that the figure is 9% higher than the previous calculation, which was based on studying leftovers from the Big Bang.

The trouble is, Riess and others think both calculations are correct. Confused? That’s OK, so are the experts.

They find the conflict so confounding that they are talking about coming up with “new physics,” incorporating perhaps some yet-to-be-discovered particle or other cosmic “fudge factors” like dark energy or dark matter. “It’s looking more and more like we’re going to need something new to explain this,” said Riess, who won the 2011 Nobel in physics.

Both calculations make sense and “nobody can find anything wrong at this point,” said University of Chicago astrophysicist Wendy Freedman. If that’s the case, astrophysicists need to make adjustments in Einstein’s general relativity theory.

“You need to add something into the universe that we don’t know about,” said Chris Burns, an astrophysicist at the Carnegie Institution for Science. “That always makes you kind of uneasy.’

In the past, astronomers added hard-to-fathom dark energy and dark matter to explain why calculations didn’t add up, borrowing from a once-discarded Einstein theory. They said they need to do something similar again.

It could be there’s an extra “turbocharge” from a past odd pulse of dark energy — an unseen expansion force that fits well in Einstein’s theories — that caused the speeded-up expansion, Riess said.

Or there could be a new particle of matter that hasn’t been discovered, Burns said.

NASA astrophysicist John Mather, another Nobel winner, said this leaves two obvious options: “1. We’re making mistakes we can’t find yet. 2. Nature has something we can’t find yet.”