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  • Seventy percent of our universe is made up of something so weird and so strange, it

  • continues to baffle the world's brightest minds.

  • We are absolutely still lacking great ideas.

  • It is crying out for some new breakthrough, new thinking.

  • Perhaps the greatest remaining

  • mystery in our universe.

  • Dark energy is basically our name for that thing that we don't understand.

  • Its not the colour dark its just an expression of our ignorance as to what is this stuff.

  • A genius could come up with a new theory.

  • Yeah, it is quite possible.

  • I'm kind of hoping it's me.

  • So this is clearly a huge deal in physics and raises many, many questions.

  • The obvious one to start with is:

  • Now, ever since the Big Bang, our universe has been expanding with space itself,

  • stretching, moving galaxies further apart.

  • Now, physicists used to think that the energy that was made in the Big Bang to power that

  • expansion would eventually start to run out and the expansion would start to slow down.

  • Then a Nobel Prize winning discovery turned all of that on its head.

  • Saul Perlmutter and his team measured the way the universe was expanding by comparing the

  • brightness of supernovae.

  • This is when a star runs out of fuel at the end of its life.

  • They brighten as a fireworks and fade away and they reach the same brightness.

  • And you can then use that as an indicator of how far away it is by just looking to see how

  • bright it appears to you.

  • Just like when you watch a car recede into the distance you can tell how far away it is by

  • how faint the taillights look.

  • If you can use the brightness of the supernova to tell you how far away it is, that's

  • really telling you how long ago the explosion occurred because you know how long it takes

  • for light to travel that great distance.

  • And what they discovered definitely shook the physics world.

  • Suddenly, he was saying that we lived in a universe that was accelerating.

  • I remember just being just incredible.

  • I mean, all the astronomers walking around scratching their heads saying this can't be right.

  • Surely it can't be right.

  • Now exciting as this finding was, like many things in science.

  • It raised a lot more questions than answers.

  • Once you know that the universe is actually speeding up, then you're faced with the

  • question of, well, what could make it speed up?

  • This mysterious thing that was causing this

  • newly spotted phenomena that no one could explain was immediately called Dark Energy.

  • Now, it's great to have a name for this, but it doesn't exactly explain what is driving

  • this accelerated expansion.

  • Now, just like with dark matter, which makes up twenty five percent of the universe and is

  • also currently unexplained, this weird type of energy seems to defy our laws of physics

  • and has properties that are current models just cannot explain.

  • So you can think of it as you get more space, you actually get more dark energy, which is

  • like getting something for nothing, which is clearly ridiculous.

  • The way we think about it is that it's either some new stuff in the universe, some

  • particle, or even just a new field that you put into the universe to explain the

  • properties of the universe.

  • So what is it that's changing the way our universe evolves?

  • Well, scientists differ in their thoughts of what it could be from a liquid or a brand new

  • particle like dark matter or even an unknown force.

  • Now, scientists at Berkeley in California are looking for something that they call

  • chameleon particles.

  • This is a whole new type of particle that's thought to create a force which, when it

  • interacts with other particles, changes those particle's mass.

  • By putting atoms in a vacuum.

  • They're hoping to expose these chameleons.

  • The experiment works by first collecting a cloud of Caesium atoms on top of the spheres,

  • and the atoms are free to fall, subject only to the Earth's gravity and the potential

  • chameleon force.

  • We will either discover the particle or rule it out once and for all.

  • So far, they haven't found any evidence for these chameleon particles and their elusive

  • force, but it is an idea that continues to be explored.

  • So whatever this energy is, we now know that it makes up a whopping 70 percent of our universe.

  • Now, the obvious place to start is by looking at how the universe formed and has evolved

  • with incredibly powerful telescopes.

  • One of the things that I do is try to simulate the entire universe and tie what we think

  • about the physics of the evolving universe to what we actually see with surveys like DESI

  • DESI, the Dark Energy Spectroscopic Instrument is one of these incredibly powerful

  • telescopes observing the distant universe.

  • And the further away galaxies are, the younger they appear to us.

  • That's because light takes time to travel to us.

  • It can take even a billion years to reach us here on Earth.

  • Thanks to this, we can look at the average distance between galaxies at different cosmic

  • times and look how it's changed due to the expansion of the universe and therefore figure

  • out what is the role of dark energy.

  • What we need to do that is more detail and we get more detail from more data.

  • Now, there's a lot of projects and telescopes that are mapping the universe in this way.

  • But one that we're all very excited for is the launch of the space telescope Euclid in 2022

  • It's the most powerful telescope ever created, even dwarfing the iconic Hubble Space Telescope.

  • So it could be just what we need to solve this problem.

  • These are going to be the biggest images that come down from orbit, you have an image

  • effectively of 625 megapixels. So that's roughly 300 HD television

  • screens full of data and that comes down every 10 minutes.

  • This imager takes roughly the same amount of data that Hubble has taken and will take in

  • its entire lifetime in one day.

  • The hope with Euclid is that it will be able to give us the detail that we so desperately

  • need to be able to solve this problem.

  • We have lots of theories and hundreds of models that could still fit our data.

  • When Euclid comes, lots of these can be thrown away and I could narrow down the

  • possibilities of what this dark energy is.

  • Euclid will give us a coherent data set that we can test all these theories against.

  • So dark energy remains the biggest mystery in physics.

  • But with all these great scientific minds across the world and all the projects focused so

  • desperately on figuring out what this is, it might not be long before we finally find this

  • huge missing piece of the puzzle.

  • We need teams like Euclid.

  • That's the only way you can get the data that you need.

  • But to understand that data, to give it some interpretation, to give it an idea could come

  • from one person.

  • That could be the next Einstein.

Seventy percent of our universe is made up of something so weird and so strange, it

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暗物質(What Is Dark Energy? | Space Mysteries | Earth Lab)

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    joey joey 發佈於 2022 年 01 月 04 日
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