Ancient light from the Big Bang has revealed a new accurate estimate for the age of the universe: 13.77 billion years, plus or minus 40 million years.
The new estimate, based on data from a series of telescopes in the Chilean Atacama Desert, also influences one of the most important disagreements in astrophysics: how fast is the universe expanding? Described in two scientific articles, the new result gives a significant boost to one side of the disagreement, although physicists were unable to prove that the other side of the dispute is wrong.
Here’s the problem: Physicists need to understand the rate of expansion of the universe to make sense cosmology – The science of the past, present and future of our entire universe. They know that a mysterious substance called dark energy it’s causing the universe to expand (at an ever increasing rate) in all directions … But when astronomers point their telescopes into space to measure Hubble constant (H0) – the number that describes how fast the universe is expanding at different distances from us or another point – they come up with numbers that disagree with each other, depending on the method they use.
A method, based on measurements of how quickly nearby galaxies move away from the Milky Way, produces an H0. Another method, based on the study of the oldest light in space, or the cosmic microwave background (CMB), produces another H0. This disagreement has left scientists wondering if there is any significant blind spot in their measurements or theories, like Live Science earlier reported. These new results seem to show that there were no measurement errors on the CMB side.
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“We found an expansion rate that is in Planck’s satellite team estimate,” which is another WBC study, Cornell University astrophysicist Steve Choi, lead author of one of the two new articles, said in a statement. “This gives us more confidence in the measurements of the oldest light in the universe.”
Data from the Planck satellite, launched in 2018, were the most important measurements of the CMB before now. With an unprecedented level of precision, they showed how sharply the CM0 measurements of H0 disagree with the measurements based on the motion of nearby galaxies.
These new results recalculated the CMB measurement from scratch using a completely different set of data and calculations from the telescope, and yielded very similar results. That doesn’t prove that the CMB measurement of H0 is correct, there could still be a problem with the physical theories used to make the calculation, but it suggests that there are no measurement errors on that side of the disagreement.
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Based on data from the Atacama Cosmology Telescope (ACT) in the Atacama Desert in Chile, the researchers tracked weak differences between different parts of the CMB, which appears to have different energy levels in different parts of the sky. The CMB, which was formed when the universe cooled down after the Big Bang, is detectable in all directions in space as a microwave glow. They are more than 13 billion light years away, a relic from the time before stars and galaxies formed.
By combining theories about how the CMB was formed with accurate measurements of its fluctuations, physicists can determine how fast the universe expanded at that time. Those data can be used to calculate H0.
ACT methodically scanned half the sky between 2013 and 2016, particularly looking at microwave light. The researchers then spent years cleaning and analyzing the data with the help of supercomputers, removing other microwave sources that are not part of the CMB, to put together a complete map of the CMB. All the while, they “blinded” themselves to the implications of their work, they wrote in their documents, meaning they didn’t see how their choices affected H0’s estimates to the end. Only when the complete CMB map was completed, did the researchers use it to calculate H0.
The new CMB map also offered a new measure for the distance between Earth and the CMB. That distance, combined with a new measurement of how fast the universe has expanded over time, allowed for an accurate calculation of the age of the universe.
“I had no particular preference for any specific value; it was going to be interesting in one way or another,” Choi said.
It is still possible, as Live Science has previously done. reported, that some error in those theories is ruining the calculation. But it is not clear what the error would be.
The other approach to calculating H0 is based on pulsating stars known as Cepheids, which reside in distant galaxies and pulse regularly. That timed pulse allows researchers to make precise calculations of its motion and distances from Earth.
With those direct speed measurements, it’s pretty easy to come up with an H0 measurement. There are no complicated cosmological theories involved. But it is possible some scientists have proposed that our region of the universe is strangely empty and not representative of the entire universe. It is even possible that there are measurement problems with Cepheids, and that these cosmic measuring sticks may not work as expected by physicists.
For now, the true H0 remains a mystery. But CMB investigators have more ammunition on their side of the disagreement.
Both new articles describing the new analysis were published July 14 in the prepress database. arXiv and submitted for formal peer review.
Originally published in Live Science.
