When you are trying to solve one of the biggest conundrums in cosmology, you should triple check your homework. The puzzle, called the Hubble Tension, is that the current rate of the expansion of the Universe is faster than what astronomers expect it to be, based on the Universe’s initial conditions and our present understanding of the Universe’s evolution. Astronomers using the NASA/ESA Hubble Space Telescope and many other telescopes consistently find a number that does not match predictions based on observations from ESA’s Planck mission. Does resolving this discrepancy require new physics? Or is it a result of measurement errors between the two different methods used to determine the rate of expansion of space?
One of the scientific justifications for building Hubble was to use its observing power to provide an exact value for the expansion rate of the Universe.
Prior to Hubble’s launch in 1990, observations from ground-based telescopes yielded huge uncertainties. Depending on the values deduced for the expansion rate, the Universe could be anywhere between 10 and 20 billion years old.
Over the past 34 years, Hubble has shrunk this measurement to an accuracy of less than 1%, splitting the difference with an age value of 13.8 billion years.
This has been accomplished by refining the so-called ‘cosmic distance ladder’ by measuring important milepost markers known as Cepheid variable stars.
However, the Hubble value does not agree with other measurements that imply that the Universe was expanding faster after the Big Bang.
These observations were made by ESA’s Planck satellite’s mapping of the Cosmic Microwave Background (CMB) radiation.
The simple solution to the dilemma would be to say that maybe the Hubble observations are wrong, as a result of some inaccuracy creeping into its measurements of the deep-space yardsticks.
Then along came the James Webb Space Telescope, enabling astronomers to crosscheck Hubble’s results.
Webb’s infrared…
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