High in the Atacama Desert in Chile, miles away from the pale glow of light pollution, the secluded Atacama Cosmology Telescope is in the best position to search the air for answers. The question that has been on my mind lately? The age of the universe, a cosmic problem that can be answered in different ways depending on how you measure the accelerated expansion of the universe.
Recently a paper published in the Journal of Cosmology and Astroparticle Physics measured the rate of expansion, called the Hubble constant, using the National Science Foundation’s telescope in Chile.
The team found that the Hubble was constantly 42 miles per second per megaparsec – meaning that for every megaparsec, or 3.26 million light-years, the rate of expansion of the universe increased by 42 miles per second. The number found by the international team of astronomers and physicists after 730 days of observation from 2013 to 2016 was almost the same as previously reported by the European Space Agency’s Planck satellite in 2013.
‘Now we have an answer where Planck and [Atacama Cosmology Telescope] agree, ”said Simone Aiola, a researcher at the Flatiron Institute’s Center for Computational Astrophysics and co-author of the article. in a press release. “It speaks to the fact that these difficult measurements are reliable.”
There is a fairly large reason why it was worth recalculating the constant: there are a few ways to measure the rate of expansion of the universe, from which the age of the universe can be deduced. You can measure the rate based on stellar things near us, such as pulsating Cepheid stars. You can also measure the expansion by looking at the polarized light of the cosmic microwave background of the universe, the farthest perceptible radiation from the big bang, that the Atacama team did here. This faint light has a variation in the polarization, which enables scientists to measure how far the light traveled and how long the journey took. This is why the rate of expansion of the universe is important: it changes how far the light has gone, and therefore the age of everything.
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Here’s the problem: The two ways to calculate Hubble’s constant got quite different rates –one study for 2019 came up with almost 46 miles per second per megaparsec, while another from the same year found a number that divides the difference between the other two. Although the differences may sound small, the varying estimates mean a series of hundreds of millions of years to determine how old our universe is. (The higher the constant, the younger the universe).
The findings of the Atacama team place the age of the universe at about 13.77 billion years. By comparison, our solar system is about 4.57 billion years old, and Homo sapiens originated somewhere about 300,000 years ago.
The different numbers so far do not mean that any party is necessarily wrong (although the team behind the new article works with better resolution of the cosmic microwave background than their predecessors at Planck, confirmed that the math of the previous team was solid). What this all definitely means is that we are missing something when it comes to expanding the universe.
The difference between local and remote measurements of the Hubble constant can mean that ‘there is one problem with one of the types of measurements that we do not interpret correctly, and therefore there is some kind of systematic problem with one or the other measurement’ , said Michael Niemack, an astrophysicist at Cornell University and co-author of the recent article. “The more exciting possibility is that something is missing in our cosmological model.”
The best can still come for the Atacama telescope, which had its first light in 2007 and has the advantage of being on the ground, making it easier to operate than a space telescope.
“We have yet to extract all the information from the data we have already collected with the Atacama Cosmology Telescope,” Steve Choi, an astrophysicist at Cornell University and lead author of the article, said in an email. “I am hopeful that with the upcoming experiments in the Atacama, such as CCAT-prime and Simons Observatory, we will learn even more exciting physics about our universe,” referring to two emerging observatories at great heights in the desert. The CCAT-prime telescope was renamed the Fred Young Submillimeter Telescope in September, and it will look at a slew of cosmological features, while the Simons Observatory will focus its observational ability on the cosmic microwave background.
Perhaps one party judging the age of the universe is considering something in their mathematics – with the many known unknowns of space science, and the things that are completely unknown, it is possible. But according to Niemack, there could just as easily be something else in the mix that would explain the different numbers.
“It may be a hint that we are just about to discover something new and exciting that we have not known before about how our universe works,” he said.