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The Universe Just Keeps Getting Hotter. That Shouldn’t Be Happening.

And it probably doesn’t bode well for Earth.

Popular Mechanics

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Is it just us, or is it getting hot out there? Research shows our rapidly growing universe keeps heating up.

Nearly a century ago, scientists worked out that our universe is expanding. More recently, researchers discovered this rate of expansion is increasing as time ticks by. As our universe expands, the galaxies, stars, planets, and all they contain move farther and farther apart. This means our universe should be getting colder as it expands.

But that may not be the case after all. A team of international scientists compared the temperature of cosmic gas farther away from Earth (and, therefore, farther back in time) to younger gases nearer to our planet and to the present day.

According to their calculations, in the past 10 billion years, the mean temperature of these gases has increased by more than 10 times, Universe Today reports. Their analysis revealed the cosmic gas spread across our universe can reach temperatures of roughly 4 million degrees Fahrenheit. The scientists published their findings in October 2020 in the Astrophysical Journal.

What's the deal here? Astrophysicist and study author Yi-Kuan Chiang of Ohio State University broke it down in a statement:

“As the universe evolves, gravity pulls dark matter and gas in space together into galaxies and clusters of galaxies. The drag is violent—so violent that more and more gas is shocked and heated up.”

Measuring changes in our universe's temperature over the course of roughly 10 billion years isn't an easy task. The team compiled data from two missions: the European Space Agency's Planck Infrared Astronomical Satellite, which launched in 2009 and has since studied cosmic background radiation, and the Sloan Digital Sky Survey, a multi-observatory survey that's generated some of the most detailed charts of the universe to date.

The scientists measured these gases using a concept called redshift. Astronomers use redshift to study how far away certain objects are. Objects that are farther away have longer (and redder) light wavelengths than objects that are nearer to us. The scientists also developed a brand new method through which they could estimate the temperature of an object from its light.

So what does all this mean for us? Well, if the universe is getting hotter, that might mean we'll also see an increase in cosmic radiation. That doesn't bode well for us Earthlings.

Jennifer Leman is based in Easton and writes/edits articles about Earth’s many wonders and hazards. She is a graduate of Smith College and the UC Santa Cruz Science Communication Program. You can find her work in Scientific American, Nature, Science News, and The Mercury News, among other publications.

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This post originally appeared on Popular Mechanics and was published November 18, 2020. This article is republished here with permission.

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