Sunday , April 18 2021

Hubble's measurements confirm that there is something strange about how the universe has expanded

Large Magellanic Cloud with Hubble close range.
Image: NASA, ESA, Adam Reyes and Palomar survey for digitized sky

The new results from the Hubble Space Telescope have deepened one of the greatest mysteries in astronomy.

Astronomers know that the universe is expanding, and expansion is accelerating. Sometimes you will hear news stories that the universe is spreading "faster than we thought". But that's not exactly what's happening. The rate of expansion, called the Hubble constant, is the subject of an important difference: its value varies based on how scientists are trying to weigh it. The new results from the Hubble Space Telescope have now "raised the discrepancy that is above the credible level of happiness," according to the newspaper published in the Astrophysical Journal.

As the distance between stars and galaxies grows, scientists have invented several ways to measure the rate of expansion. One method calculates the expansion based on the farthest radiations our experiments can see, called the cosmic microwave background. Others use supernova data to calculate the rate. Both methods measured the expansion rate of about 67.7 kilometers per second per megaparsec, which means for every 3.26 million light years, the Universe is increasing another 67.7 kilometers per second faster.

But other measurements do not agree. Scientists using the Hubble Space Telescope have calculated the permanent Hubble by using a recent measurement of the distance to the neighboring satellite galaxy called the Great Magellanic Cloud, as well as new observations of 70 cepheid variables, a kind of pulsating star. The rate of peptidation of the cepheids and the brightness is closely related to the fact that their distance can be calculated. Combined with other improvements, they calculated the expansion of the Universe at 74 kilometers per second per megaparse.

Basically, when scientists look further, the universe seems to be spreading slower than when seeing the local Universe.

The new measurement officially makes the discrepancy meaningful enough that it's incredible that it comes from random statistical fluctuations in the data. Moreover, it seems that other tests show that the difference is not caused by errors in any of the measurements. This means that experiments can measure a feature of the universe that is not explained by the most widely accepted theory of cosmology.

It's hard to say what's really going on, but the next step is clear. "Continue execution in precision in determining [the Hubble constant] is … needed to move from revealing the difference to the diagnosis of its source, "the authors of the study write.

Scientists are already implementing new ways of measuring the Hubble constant, especially using collisions with neutrons that collide and gravitational waves that produce them in the space itself. By calculating the distance to the collision by means of gravitational waves and the speed at which the stars move away using the light of the collision, physicists will have another way to calculate the value of the Hubble constant.

So, again, it's not that the Universe is spreading faster or slower than we previously thought. Instead, discrepancy in these measurements can ultimately reveal a completely new aspect of the universe for which scientists are currently in darkness.

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