The Dark Energy Telescope That Sees Into The Past
Scientists have built an extremely powerful telescope to shed light on Dark Energy, which makes up 68% of our universe, but there's a catch - we can't see it and we don't know what it is.
Want to read more about space? Check out this Super-Earth that has 617 days in a year.
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We all know about the Big Bang theory - not the series, the explosion that created the universe, Earth and us. This theory predicted that the universe would gradually stop expanding, like a spilled carton of milk would eventually stop spreading over the kitchen floor once all the milk had been released. It makes sense, right? But in 1998, astronomers discovered something shocking: the universe was continuing to expand, and at an accelerated rate. Like there was a limitless supply of milk.
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Since then, the most widely understood explanation is that the thing counteracting the pull of gravity coming from each planet is called Dark Energy. Dark Energy is a mysterious thing that can't be seen by any of our instruments on Earth, yet we know it exists. In fact, Dark Energy makes up 68% of our universe, with Dark Matter making up 27% and the remaining 5% is visible matter. That means that all the incredible things out there in the universe - stars, planets, asteroids, suns, moons, space junk, black holes, supernovae - is only 5% of what's actually out there!
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One of the reasons scientists know that Dark Energy exists is because of the way it interacts with other things. Dark Energy counteracts gravity, making the universe expand at an increasing rate (if Dark Energy wasn't in the picture, the universe would be shrinking). Right now, scientists know how Dark Energy acts, but they don't know what it is. And that's where DESI comes in.
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DESI stands for Dark Energy Spectroscopic Instrument, and it's the first of its kind. DESI's job is to examine Dark Energy. But is it possible to see something that can't be seen? Scientists think that the answer to this is yes. Inside DESI are 5,000 optical fibres, each acting as a mini-telescope. This means that DESI can capture the light from 5,000 different galaxies at once, mapping their distance from Earth and gauging how much the universe has expanded as this light traveled to Earth. Ideally, DESI can see a new set of 5,000 galaxies every 20 minutes.
The further DESI looks into space, the father back in time DESI sees. This is due to the time it takes light to reach the Earth (traveling at the speed of light). DESI can see 10 billion light years away, which means it can see 10 billion years into the past. Pretty impressive.
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Although this isn't the first time scientists have tried to investigate Dark Energy, DESI is able to cover a much larger volume of space. It's also three times more accurate than any instrument used before. Once completed, DESI will have created a 3D map of the universe spanning to 11 billion light years away. DESI is planned to continue mapping the universe for five years, until it has detailed the precise measurements of the universe's expansion rate. As the experiment began in early 2020, we'll have to wait until 2025 to find out the truth about Dark Energy.
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