It seemed for a while as we forged bravely into the 21st century that we were pretty smart. We thought we were figuring out the mysteries of the universe, one after another. Recently, however, there’s been a series of reports that all challenge our model of the universe, which we thought was pretty well figured out. First we find out that the sun is a lot stranger than we think it is, then we find out that the universe is more than a billion years younger than it should be. These both suggest the same thing: we’re not nearly as smart as we think we are. This is nothing new, of course. The story of humanity is in essence the surfing of the constant realization that we’re pretty dumb all the way to the stars. Which is a neat little trick.
Now there’s a third in the series of assumption defying realizations. The Hubble constant is an astrophysical value that represents the expansion rate of the universe. It was named for Edwin Hubble who, in 1924, discovered that the farther away from Earth a galaxy was, the faster it appeared to be continuing its outward trajectory. In the early 1990’s, a team led by astrophysicist Wendy Freedman calculated the Hubble Constant within 10% of it’s true value, and scientists have been trying to refine that calculation ever since.
The Hubble Space Telescope, also named for Edwin Hubble, was used to calculate the Hubble constant.
And there seems to be a pretty big problem. Wendy Freedman recently recalculated the Hubble Constant using red giant stars as mileposts—red giants are useful because they reach the same brightness late in their evolution and thus make pretty good distance markers. With her new calculation, recently accepted for publication by the Astrophysical Journal, Wendy Freedman came to an entirely different result than she and her team calculated in the 1990’s. What might this mean? Well, this is just the latest in a series of discoveries related to the age and expansion of the universe that have found serious discrepancies, discrepancies that open up the possibility that something is well and truly broken with physics.
“Alright, I admit it. I don’t understand!”
Wendy Freedman’s red giant method of calculating the Hubble constant was supposed to be a “tie-breaker” between two other competing calculation. Instead it’s a different result entirely. According to Freedman:
“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.”
“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.”
NASA is launching a brand-new telescope at some point in the mid-2020’s called the Wide Field Infrared Survey Telescope (WFIRST). This telescope will provide the same resolution as the now-defunct Hubble Space Telescope with 100 times the field of view. Astronomers hope that this new super telescope will show them where the discrepancy lies without making us re-do physics. More likely, it will probably keep showing us just how dumb we are.
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