Scattered throughout the vacuum of space are stars, galaxies, stellar remnants, and other objects billions and billions of years old. The age of the universe is now estimated to be around 13.8 billion years old – almost unfathomable. But how do we know this?
We can determine the age of the universe (to some extent) by analyzing light and other types of radiation from deep space, but scientists don’t always agree on how old the universe is. universe, and they continue to refine the answer as telescopes advance.
In the 1920s, astronomer Edwin Hubble found a way to determine the relationship between an object’s distance, as a function of the time its light takes to reach Earthand how fast it is moving away from us, depending on how much light from distant places has shifted to red or shifted to the lower energy (or redder) end of the electromagnetic spectrum.
This measure, now known as Hubble constant, describes the expansion of the universe to different places. According Nasa (opens in a new tab), the Hubble constant is higher for more distant objects, and vice versa, suggesting that the expansion of the universe is accelerating. A consequence of this discovery is that the estimated age of the universe is more difficult to prove.
At present, the universe is believed to be around 13.8 billion years old. This was determined by different groups of scientists who announced their findings in 2020 after re-evaluating data from the European Space Agency’s Planck spacecraft and analyzing data from the Atacama Cosmology Telescope (ACT) in Chile. This is about 100 million years older than the previous estimate, which was determined by data transmitted by the Planck spacecraft in 2013. The spacecraft and telescope had mapped the cosmic microwave background (CMB), which is the residual light of the big Bang. By combining this data with existing models of how quickly different types of matter and celestial objects would have appeared after it all began, scientists were able to estimate how far away this explosive birth of the universe occurred.
Related: What is the oldest star in the universe? And the youngest?
Scientists believe that CMB light appeared 400,000 years after the Big Bang. The universe began as a burning plasma, in which packets of light, or photons, were attached to electrons. It eventually cooled enough for the photons to break free from the electrons, leave the plasma, and disperse into space, forming what is now called the CMB. So, by measuring how far away this scattered light is, scientists get an estimate of the age of the universe.
“The greater the distance we measure to the most recently scattered photons, the older the age of the universe, because the CMB had to travel a longer distance to reach us,” said Steve Choi (opens in a new tab), National Science Foundation Postdoctoral Fellow in Astronomy and Astrophysics at Cornell University. “It would have taken longer, which means older age.”
For the new estimate of 13.8 billion years, announced in 2020, Simone Aiola (opens in a new tab)researcher at the Center for Computational Astrophysics at the Flatiron Institute in New York, led a team of scientists who re-examined the cosmic microwave background using ACT, according to their study, published in the Journal of Cosmology and Astroparticle Physics (opens in a new tab).
“Although these maps cover a smaller region than those published by the Planck team, their improved resolution allows for more precise measurements,” Aiola told Live Science. “Our observations provide an independent measurement of the CMB sky that can be compared to the measurement made by the Planck team.”
Aiola and his colleagues made a breakthrough by being able to observe the CMB on a smaller scale than ever before, so they were able to see many more details and irregularities that told what happened in the early universe. and at what distance these phenomena had occurred. This was possible because the ACT is so hypersensitive. By comparing these highly accurate maps to existing predictions of the age of the universe, the team arrived at an age of 13.8 billion years.
A similar study with the Atacama Cosmology Telescope – led by Choi, co-authored by Aiola and published in the Journal of Cosmology and Astroparticle Physics (opens in a new tab) in 2020 – also discovered that the universe is around 13.8 billion years old.
Is it possible that the universe is even older? Maybe. As telescopes become more advanced, they might be able to see further into the past than we ever imagined – and find something that changes everything we thought we knew.