Whether the standard cosmic recipe might now need to be modified — for example, to account for a new species of subatomic particles streaming through space from the Big Bang — depends on whom you talk to. Some say it is too soon to get excited about new physics sneaking through such a small discrepancy in a field noted for controversy. With more data and better understanding of statistical uncertainties, the discrepancy might disappear, they say.

“No explanation I know of is less ugly than the problem,” Lawrence M. Krauss, a theorist at Arizona State, said.

Others say this could be the beginning of something big. David Spergel, a cosmologist at Princeton and the Simons Foundation, called the discrepancy “very intriguing,” but said he was not yet convinced that this was the signature of new physics. Michael S. Turner of the University of Chicago said, “If the discrepancy is real, this could be a disruption of the current highly successful standard model of cosmology and just what the younger generation wants — a chance for big discoveries, new insights and breakthroughs.”

Dr. Riess and his colleague Stefano Casertano got roughly the same answer of 73later last summer, strengthening the claim for a mismatch of Hubble constants. They used early data from the European spacecraft GAIA, which is measuring the distances of more than a billion stars by triangulation, thus allowing astronomers to skip some of the lower rungs on the distance ladder.

They calculated that the odds of this mismatch being a statistical fluke were less than one part in a hundred — which might sound good in poker but not in physics, which requires odds of less than one in a million to cement a claim of a discovery.

“I think it’s a potentially serious issue,” said Alex Filippenko, a University of California astronomer who is part of the team. “In this line of research the devil is in the details. And after getting the details right, we’re left with a major puzzle.”