April 25, 2019


Hubble Hints Today's Universe Expands Faster Than it Did in the Past (Korey Haynes, April 25, 2019, dISCOVER)

In more recent years, astronomers have measured the expansion rate of today's universe using the Hubble Space Telescope. And mysteriously, the number it found for our current expansion was some 9 percent off from the expansion rate of the early universe, as measured by the European Space Agency's Planck spacecraft. At the time, astronomers said the odds were something like 1 in 3,000 that the disagreements were a fluke. But in a study released Wednesday, scientists say they've refined the Hubble measurements, doubling down on the idea that today's universe is expanding faster than it was in the past, and dropping the odds of a mistake to 1 in 100,000. At this point, something is definitely fishy, and astronomers need to understand why. [...]

[R]iess and his SH0ES team used Hubble Space Telescope observations, combined with ground-based observations, to reduce the uncertainty in the distance to Cepheid variables in the nearby Large Magellanic Cloud from 2.5 percent to 1.3 percent.

They found that the earlier measurements of the Hubble Constant in the nearby universe were spot-on. This came as a surprised to Riess and his team because it confirmed earlier disagreements with the Planck telescope. That spacecraft measures fundamentals about the early universe, mapping the cosmic microwave background and calculating the ratio of dark energy, dark matter, and normal matter.

And Riess' measurements don't stand alone, but in line with a host of other measurements from today's universe. Similarly, Planck's numbers are backed up by other measurements of the early universe in the first few hundred thousand years after the Big Bang. Neither seem likely to change at this point.

"This is not just two experiments disagreeing," Riess explained in a press release. "We are measuring something fundamentally different. One is a measurement of how fast the universe is expanding today, as we see it. The other is a prediction based on the physics of the early universe and on measurements of how fast it ought to be expanding. If these values don't agree, there becomes a very strong likelihood that we're missing something in the cosmological model that connects the two eras."

It's not clear what the solution is to make the two numbers agree. And indeed, at this point, it's not clear they will ever agree. Instead, it's looking more like a true sign that our early universe behaved differently than it does today with regard to expansion.

Posted by at April 25, 2019 6:38 PM