The Mystery Of Dark Energy

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Going out into nature hiking paddling looking up at the stars has always helped me center myself. It reminds me that I'm just Madeleine Kelly via one human among millions of critters and trees and galaxies that don't care about me or acknowledged me at all. I'm just a group of random atoms matter taking up space. In it turns out that matter as we normally think of it is a tiny tiny portion of the universe meaning your genes, the ocean trees, computers, all the stars, and planets. All of that is only five percent of the universe and the rest of the stuff is dark matter and dark energy right? which is wild. That's so. Much. That's too much of it. Honestly. Yeah. It's like a very uncomfortable place to be in when you think about. We study the universe and theoretically we understand. You know on some scale, how the universe works, and then all of a sudden you're like Oh wait we actually do not understand like over ninety five percent of our universe what the large majority of our universe is made up of this mysterious thing called I kid you not. Dark Energy. In get this it's how we know that our universe is expanding. I learned about dark energy honestly like three weeks ago and it blew my mind dark energy is intrinsic to the fabric of Space Time that is somehow pushing galaxies apart. This is Sarafina Nancy's Day job. I am a PhD student at UC, Berkeley, studying, Supernova, and cosmology Supernova meaning an exploding star that can help us understand how our universe is changing. You know no big deal. It's a really phenomenal thing in sort of the scale of the universe to see something change, and that's this class of astronomy called transients where things change in the night sky and you can learn about them through their changes. So today we explore one of the universe's biggest mysteries dark energy from the days of Einstein Stein to the exploding stars that help us understand the very fabric of our universe. So Okay Serafina, to really understand dark energy, we have to go back to to Einstein right. Yes. So Einstein came up with this theory of general relativity, which is basically his version of gravity in the early nineteen hundreds and. The only way to make his equations work. And satisfy what he thought was a static universe. He introduced this. Fudge factor in his words called cosmological constant. So Einstein actually thought that the universe was static, not not that it was expanding. That's right and over the next ten years people. Sort of manipulated these equations and tried to find solutions and started hinting at perhaps the universe wasn't static. Well it's nice to see that Einstein could get things wrong. That's cool. So. The funny thing is this cosmological constant he called his biggest blunder. Honestly Nice to hear Einstein. Say I messed up you know what I? Can. act. The Fun fact is that he ended up actually being right So it turns out that that cosmological constant is exactly what we think dark energy is necessary to actually describe our universe. I feel like that's classic. Einstein him being wrong being more right than I've ever been in my entire life exactly. Yes. Okay. So After. Einstein introduces this idea that that the universe is static. We figure out actually that the universe is expanding, right? Yes. So in one, thousand, nine, hundred, twenty, nine, Hubble Edwin Hubble. Showed that the universe is not static it's actually expanding. what he did is he measured basically galaxies and how far away they are, and he found that galaxies are actually moving away from us. So that means that the universe is not static. It's in fact expanding in at this point, we think that the universe is expanding but that that expansion is slowing down, is that correct? Exactly. So we think that the expansion comes from the Big Bang and it comes from inflation, which was right after the Big Bang which this rapid expansion of space. But because there's gravity universe and there's mass universe we would think that gravity starts to take over and the expansion decelerating because gravity starts to pull things back at and then in in the late nineties, we get turned on her head again, right there's another big discovery and we're like Oh way way way. Maybe she's not slowing down. That's right. So in one, thousand, nine, hundred, Ninety, eight, and in one thousand, nine, hundred, nine, two teams that were studying a specific type, of Supernova, and they found that these supernova that were super far away from us were fainter than what we would have expected if the universe was in fact expanding but decelerating expansion. And the only way to explain away dot faintness is if the universe was instead accelerating its expansion. Wild we went from the university static. Okay. It's not static it's expanding, but it's slowing down that expansion. Two Way Way Way not only is it expanding, but it's expanding faster than we thought it was and it's speeding up in. In in the explanation for that is dark energy you killed it. That's right. Nailed it. Okay. So so yes, we have finally gotten to the point where I can ask you Sarafina what is dark energy? So. I think the only answer to that question is we don't know Oh, come on Sarafina you all the way here. You told me I'm showing story and we don't know I know it's it's really uncomfortable to sit with. We can see dark energy through its effects on the expansion of the universe, but we don't actually know what it is. Wow. I. Don't even know I. don't even know what to say about that. That's so. Because it's it's wild. We don't know what dark energy is, but we know it exists. Yes. In was what are you doing over there astronomers were. Four to five percent no. So that I mean that's that's wild in the amount of dark energy is staying the same right. So. That's that's an interesting question. So I liked to kind of describe dark energy and the expansion of the universe in The way that I think about it is sort of picture a loaf of bread and picture a bunch of reasons and the bread. And the reasons are like our universes galaxies and the bread itself is like Space Time Okay and so as you bake the bread, the bread rises and the raisins get farther and farther apart they're sort of carried along the fabric of space time, which means that the distance between. Galaxies increases with time. Okay, I'm with you I'm with you and the introduction of dark energy is like imagine you have the special type of yeast that you can put into a bread and the breads starts to rise with the East and then all of a sudden it starts to rise all lot and it gets bigger and bigger and bigger over time, and that's dark energy.

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