Scientists suspect that there may be fundamental flaws with our understanding of the universe.
This problem came to light when scientists tried to calculate and measure a value termed as the Hubble Constant for the rate at which our universe is expanding outward.
This significant value was first calculated by astronomer Edwin Hubble in 1924 when he discovered galaxies outside of our Milky Way and realized that the farther away a galaxy is, the faster it appears to be receding from us. But since then, astronomers have been meticulously observing and measuring the universe’s expansion only to arrive at different values of the Hubble Constant, none of which seem to match with one another. The discrepancy between predictions and observations calls into question not only our knowledge of how old the universe is, but also our ability to fundamentally understand the physics underlying its behavior.
University of Chicago astronomer Wendy Freedman said in a NASA press release, “Naturally, questions arise as to whether the discrepancy is coming from some aspect that astronomers don’t yet understand about the stars we’re measuring, or whether our cosmological model of the universe is still incomplete. Or maybe both need to be improved upon.”
Freedman’s team is responsible for the latest measurement of the Hubble Constant, which they calculated by establishing a new and entirely independent path to the Hubble constant using an entirely different kind of star from previous experiments. Her team measured the brightness of a very luminous kind of stars called red giant stars in distant galaxies. As these stars reach uniform size and brightness, their distance from Earth can be more readily calculated than from some other stars.
Freedman’s calculation which has been accepted by The Astrophysical Journal determines that the universe is expanding at 69.8 kilometers per second per megaparsec, as per the NASA press release.
This is a slower rate of expansion than what was computed in another recent study that focused on a different kind of star but a relatively faster rate than the value calculated in yet another study that measured light leftover from the big bang named the Cosmic Microwave Background.
Originally, Freedman had hoped her research would serve as a tiebreaker between the other two conflicting studies but instead it provided yet another possible value for the Hubble Constant for astronomers to reconcile.
Freedman said in the press release, “The Hubble constant is the cosmological parameter that sets the absolute scale, size and age of the universe; it is one of the most direct ways we have of quantifying how the universe evolves. The discrepancy that we saw before has not gone away, but this new evidence suggests that the jury is still out on whether there is an immediate and compelling reason to believe that there is something fundamentally flawed in our current model of the universe.”
According to a New Scientist article published recently, the issue is complicated further as statistical analysis has validated both of the two previous studies, even before Freedman’s study was announced. Statistically, there’s just a one-in-3.5 million chance that the other two findings came from random chance.
In the next decade, NASA intends to launch the Wide Field Infrared Survey Telescope into orbit possibly enabling scientists to more precisely measure the distance of celestial objects, according to the press release. Maybe with those readings, astronomers will be able to reconcile their various Hubble Constant values.
Duke University astronomer Daniel Scolnic told New Scientist, “The Hubble constant is the biggest problem in cosmology that we have access to right now, and the hope is that this crack in our understanding is going to lead us to some even bigger cracks like dark energy and dark matter. We just have to chase the crack.”