Since humans started getting in finding out more details about outer space, a recurring mystery has been clouding their discoveries. The rate of cosmic expansion is still unknown, as different methods of measurement show mixed results. The value, called the Hubble constant, is still an issue for scientists nowadays, and the situation has even been declared a “crisis.”
The Hubble constant is named after the American astronomer Edwin Hubble, and it describes the rate at which the universe is expanding. According to data gathered by ESA’s Planck satellite, the Hubble constant is 46,200 mph per million light-years (or 67.4 kilometers/second per megaparsec). However, calculations based on But pulsating stars show that the value is 50,400 mph per million light-years (73.4 km/s/Mpc).
In both cases, the value has some consequences. If the first option is correct, then scientists might have been measuring distances to distant objects in the universe wrong for a long time. In the second case, scientists might have to accept the possibility of new physics existing.
To further the discussion of the Hubble constant, Live Science interviewed Barry Madone, an astronomer from the University of Chicago. According to him, the first cause of the discrepancy is Edwin Hubble himself. In 1929, Hubble noticed that more distant galaxies were moving away from Earth at a faster rate than galaxies situated closer to our home planet. He determined a direct connection between the distance of an object from Earth and the speed at which it is receding.
What Is The Right Value Of The Hubble Constant?
Madore said: “That means something spooky is going on. Why would we be the center of the universe? The answer, which is not intuitive, is that [distant objects are] not moving. There’s more and more space being created between everything.”
Hubble realized that the universe was expanding at a constant rate. According to his calculations, the Hubble constant is 342,000 miles per hour per million light-years (501 km/s/Mpc), which is ten times larger than what modern scientists measure.
Even more, Madore explained that, in the late 1990s, astronomers found that distant supernovas were farther away than anticipated. Which meant the expansion of the universe was accelerating. Lacking an explanation, astronomers blamed this phenomenon on something they named dark energy.
Madore recently conducted a research based on the light of red giant stars. The results were published in July, providing a value of the Hubble constant of 47,300 mph per million light-years (69.8 km/s/Mpc). These results are the closest to the results provided by the Planck satellite.
However, scientists are not quick to declare this is the correct value of the Hubble constant. A lot more research needs to be done before they can agree on a precise value. “A lot of froth has been put on top of this by people who insist they’re right,” Madore said. “It’s sufficiently important that it needs to be resolved, but it’s going to take time.”