 Often, as technology increases our ability, so does our understanding. But something interesting is happening in cosmology, when we look out at the universe it appears that most of it is missing, and we don't know why. And this is your space pod for March 30th, 2016. It's a weird problem, not actually knowing where the majority of the stuff in your universe is, but that's where the idea of dark matter comes from. No, I'm not talking about the long-awaited album from Buu Tang's Jizza. I'm talking about something that we've actually postulated for quite some time. Dutch astronomer Jacobus Kaptien proposed the existence of dark matter in the 1920s by looking at the velocities of stars. Fellow Dutch astronomer Jan Ort also proposed the idea of dark matter in the 1930s. Finally in 1933, Swiss astrophysicist Fritz Zwicky, studying galaxy clusters at Caltech, found that mass calculations based on the motions of galaxies near the edges of clusters did not line up with the expected mass of those galaxies based on how much visible light the instruments were able to detect. A staggering 400 times more mass than was visually observable. The next big advance came in the 1960s and 70s, when it was found that the speeds at which galaxies were rotating did not line up with the predicted models just using regular matter. And then in the 1980s, with the use of gravitational lensing, the bending of light behind objects with large amounts of mass, we began to nail down just what exactly to look for with dark matter. The leading consensus amongst cosmologists with dark matter is that it is composed of a not yet discovered and not yet understood subatomic particle, making it now a holy grail not just for cosmologists, but particle physicists as well. So how do we say we have an understanding of something if we can't see it? We know that dark matter doesn't emit or absorb electromagnetic radiation or what most people would call light, but there are things that it does and it influences that we can see its effects of. When we look at the velocities that galaxies rotate at, we'd expect them to obey the laws of physics. That means that the further you are from the center of the galaxy, the slower your velocity should be. This chart using actual data shows what we would predict using physics as was understood with line A. But what we actually observe is line B, that the further out you move from the center of the galaxy, the velocity of objects remains relatively the same. Dark matter supplies the missing mass, which is what allows this weird anomaly to occur. Galaxy clusters are particularly important, especially using gravitational lensing like we mentioned earlier. We can actually figure out the amount of mass that is present, because dark matter actually has a measurable effect gravitationally. And in using that, we can even begin to measure out the distribution of dark matter as well. Using the Hubble Space Telescope, NASA and the European Space Agency were able to look at a galaxy cluster, CL0024 plus 17, and map out the dark matter in it. In this image of the cluster, the dark matter is represented by the blue. Regular matter is considered baryonic. That means that it's made out of protons and neutrons. Dark matter, as we currently understand it, is non-baryonic. And honestly, we have no idea what it's made out of. But there are some experiments that are hunting to potentially find what it is. Most detectors are underground to isolate them from baryonic radiation sources that could be misinterpreted as a signal. Most are also cryogenic. They operate at extremely cold temperatures, hovering just above absolute zero, minus 273.15 degrees Celsius. Noble liquids like xenon and argon are used as well. These detectors look for a flash, indicating that a potential particle of dark matter is interacting. So far, there's been no definitive results, but the experiments still continue. There is some interest in seeing if the influence of dark matter could be detected in the form of gravitational waves. But with the existence of gravitational waves, only a recent confirmation will have to wait and see just what exactly they can be useful for. But as it currently stands in the universe, when it comes to mass energy, ordinary matter like you, I, and everything we can see, that only accounts for 4.9% of everything. Dark matter accounts for 26.8% and dark energy accounts for 68.3%. So when it comes to just matter itself in our universe, it's 84.5% dark matter. Kinda weird that 95% of our universe is in the dark. Thanks for watching this space pod. I'm Jared Head. What do you think about dark matter? Well, let me know down in the comments below. And of course, don't forget to subscribe to us across our various social media accounts. And a big, big shout out to all of our patrons on Patreon. We are so happy that you contribute to our space pods and help bring them to the entire world so that we can put science and everyone's brains a little bit at a time. If you'd like to contribute to our Patreon campaign, you can go to patreon.com slash space pod. So until the next space pod, keep exploring.