Cosmology in an Snowy Desert

Since we arrived and settled in here at the pole, things have gotten busy fast.   Originally, we had about 12 days planned to take calibration measurements before the next team of SPT people arrived.  That was before travel delays in McMurdo, and so our schedule has been tight.   The receiver team is supposed to arrive this evening, so we only have a couple days left.   Their job is to remove the instrument from the inside of the telescope and upgrade the detectors inside, so we have to finish before they can begin.  We've been working on the calibration source and trying to understand the preliminary data we've taken with it.

In my last post, I promised to write a bit about the what and why of SPT,  so here is the beginning! 

Objects in the universe (such as stars, galaxies, gas, and dust) emit and absorb light at different wavelengths.  For example, we see the sun at 'visible' wavelengths but other hotter stars are seen instead in the ultra-violet.  Things that are hot emit shorter wavelength light and things that are cool emit longer wavelengths.  The South Pole Telescope observes millimeter wavelength light (think microwaves).   We're looking for relic radiation (light) from the very early universe that is now only a few degrees above absolute zero (2.73 Kelvin to be exact).   Measuring the intensity of this light across the sky, we can determine what the early universe was made of, how much of each part there was, and how it evolved into today's universe.  

The current leading theory of cosmology (the study of the evolution of the universe) suggests that the universe started with a Big Bang.  This very young universe was so hot and dense that all of the protons, electrons, and photons were constantly interacting with each other and no atoms or molecules could form.   But immediately after the Big Bang, the universe began to expand.  As it expanded, it cooled down, eventually to the point where atomic hydrogen could form (about 380,000 years after the Big Bang).   Suddenly, without electrons everywhere to scatter off of,  the photons were able to travel freely through space.  Cosmologists refer to this as the time of recombination or the surface of last scattering.   These photons, known as the Cosmic Microwave Background or CMB, continued to travel through space interacting very little with the universe around them.  Therefore, the spatial distribution of the photons is still basically the same as it was then when we look at it now.  Because the photons, protons and electrons were coupled together before recombination, the CMB is a fingerprint for the size and location of structures in the early universe.   For now, the CMB is the oldest light in the entire universe that astrophysicists can actually observe and its everywhere in space.  If you have an old TV with an antenna, about 1% of the fuzzy noise you get in between channels is from the CMB!

SPT has been observing the sky for several years now, and has made beautiful measurements of the total intensity of the  CMB.   The current challenge is to measure the polarization of the light.  I'll write more about this next time.  In the meantime, here are two pictures of me investigating the marker of the geographic South Pole.  They make a new one every year and install it in the correct spot taking into account the few meters that the ice sheet moves every year.   The station where we live is in the background.