Feature image: Behold! The cosmic microwave background. It was emitted just after the universe was one big plasma. Credit: Planck HFI telescope.
Welcome to the new and improved These Vibes Are Too Cosmic. Brian Kraus and Stevie christen their new time slot of 5-7pm on Tuesdays. We introduce the new format for the show – we’re switching off taking the helm each week (next week Stevie, the week after that Brian, and so on) serving up steaming offerings of science and music.
But this week, in this new show we’re so pumped about, we decided to introduce our listeners to….ourselves. We play music we love, interview each other on our respective research fields, and take questions from listeners.
Plasma physics (Brian): I work on plasmas, which are basically electrified gases. Imagine the process of melting a solid, and then boiling a liquid: in both cases, the atoms in the material are more and more free to move around as they gain energy. In a plasma, the electrons around the atoms have enough energy to escape the atomic nucleus, and what you’re left with is a gas of charged particles: negative electrons zooming around the heavier positive ions. You’d know a plasma if you saw one: they glow, like the plasma ball to the right or the lightning during a rainstorm.
The applications of plasma are numerous – from lightbulbs to space propulsion – but the most famous reason to study plasmas is to make fusion energy. This is the nuclear process where small atoms collide together to form bigger ones, which results in a huge energy gain for fused particles. Fusion energy could become a safe source of power, driving electrical grids with energy from seawater. The main issue is plasma containment, which means we have to keep the hot plasma (often at 10 million degrees C) from melting the walls of the container we keep it in. The most common device for magnetically confining a plasma is called a tokamak, which is basically a donut that keeps particles spinning around on a racetrack as they heat up.
My own work concerns measuring properties of plasmas with probes. Since the plasma is an electrified gas, it can conduct currents and respond to voltages – which are very easy to tap into by sticking a metal wire in the middle of the plasma! By varying the bias on the metal probe (putting stronger or weaker batteries on it), I can push or pull on the electrons in the plasma. Through this general method, we can deduce the plasma’s temperature and density at many points, so we have a good map of what it’s actually doing.
You can learn a lot more about plasmas, and my work studying them, by listening to an older show where Stevie interviews me about all of this in greater detail.
Observational Cosmology (Stevie): I work on the SPIDER instrument, a telescope with the aim to measure the polarization in the cosmic microwave background radiation (CMB, the featured image up top). The CMB is, believe it or not, microwave radiation that bathes our entire universe. Not only is this radiation the oldest in our universe, it serves as a snapshot of our universe at that time it was emitted – over 14 billion years ago. Since it’s
discovery in the 1960s (a great story unto itself), we’ve learned the CMB (like our universe) is almost entirely homogeneous and isotropic, but with tiny variations that map to density perturbations in
our early universe. These perturbations were the seeds of all the astrophysical structures we see around us today. Currently, the cosmic background radiation is our richest source of information on the evolution and large scale structure of our universe.
At only 2.7 degrees Kelvin, this radiation is difficult to measure, but not impossible. It is still just light with a defined energy ( = wavelength) and polarization. Through decades of effort scientists have carefully mapped the temperature of the CMB. Now, the forefront of observational cosmology is to map the polarization. Incredibly, the patterns in the polarization of the CMB have the capacity to
tell us about our universe back before the CMB was even emitted, pushing our understanding of our universe back to a time just moments after the Big Bang.
The SPIDER collaboration manages this task by cooling polarization-sensitive detectors to
less than a degree above absolute zero, and then sending them to the edge of space for a 20 day flight in weather balloon above Antarctica. SPIDER’s first flight was last January (2015). The flight was successful. We’re currently analyzing our rich new data set and preparing for a second flight in the next few years. As a grad student on this project, I’m pretty psyched.
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