Two new studies contradict each other. Under our current model, they can't both be right.
WE CAN'T ALL BE RIGHT. For something identified as a "constant," the universe's rate of expansion sure seems awfully inconsistent.
Back in February, a team of researchers working with NASA revealed that Hubble's Constant — the rate of the universe's expansion accepted by most physicists for the majority of the past century — could be wrong.
That wasn't the only study to make the claim. Now, two new studies back it up.
TWO STUDIES. ONE UNIVERSE. One of the new studies relies on measurements of the Cosmic Microwave Background (CMB), radiation caused by the Big Bang that still remains throughout the universe. Using data from the Planck mission, one team of researchers concluded that the rate is 67.4 km/s/Mpc (kilometers per second per Mega Parsec). That's slower than the currently accepted Hubble's Constant of 70 km/s/Mpc.
The other study looks at pulsating stars in nearby galaxies to determine the universe's expansion rate. These stars have regular cycles of brightness, which makes it (relatively) easy to measure their distance from Earth. According to that analysis, the expansion rate is 73.4 km/s/Mpc — that's faster than the currently accept Hubble's Constant.
TENSIONS RISE. The problem is that both of these studies appear scientifically sound. Using our current cosmological model of the universe, that should be impossible. Either there's something wrong with one or both of these studies — maybe there's some flaw we aren't seeing, or perhaps the researchers are basing their conclusions on some statistical fluke.
Or maybe there's something wrong with our physics.
If this last situation is the case, we'll need to figure out a new physics that makes sense of all these studies. If we can do that, we could find ourselves looking at the universe through an entirely new lens.
READ MORE: The Universe's Rate of Expansion Is in Dispute – and We May Need New Physics to Solve It [Phys.org]
More on the universe's expansion: To Measure the Universe’s Expansion, We Might Need New Physics