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The Bottom of the World

Writer's picture: Mishkat BhattacharyaMishkat Bhattacharya

Talking to some of my colleagues who work there, I recently became curious about the continent of Antarctica. This post is divided into two sections, both of which consider why Antarctica is of interest to a physicist. The first section describes the remarkable physical attributes of 'the last continent'. The second section talks about the physics investigations that are being carried out there.


Physical attributes (and accessibility)


The temperatures in the Antarctic interior are about -70F. Technically, Antarctica is a desert, because it receives less than 10 inches of precipitation per year. Antarctica is very dry, with relative humidity of about 0.03%. It is the highest continent - the average height above sea level is more than 8000 feet. Some of these characteristics make Antarctica an ideal location for certain kinds of physics experiments.


One can get to the coastal regions of Antarctica, in the three months of summer (October to February), by flying from Christchurch (New Zealand) to McMurdo Station (Antarctica) or from Cape Town (South Africa) to Wolf's Fang Camp (Antarctica), for example. A second flight can take you to the South Pole, where the airstrip is made of ice. Apparently these trips are now available commercially.


The rest of the year, during the winter, the South Pole is inaccessible. This means those who choose to stay are pretty much physically cut off from the rest of the planet.


Experiments


Near the physical south pole is the Amundsen-Scott South Pole Station. Amundsen was the first person to reach the South Pole. He returned alive to receive many honors. Scott reached the Pole shortly after and died on the return journey. He received his honors posthumously.


The Station is a building which hosts researchers who carry out various experiments at the Pole. It is a few meters from the geographic South Pole which is indicated by a marker and flags of the twelve countries who were the original signatories to the Antarctic Treaty. The Treaty agrees that Antarctica should be used for peaceful purposes only, etc.


Some of the important physics experiments running at the South Pole (this list is neither comprehensive nor in any order of importance):


i) The South Pole telescope is looking at the Cosmic Microwave Background (CMB) that permeates the universe. The CMB consists of the light that was created at the Big Bang, but which could only travel throughout the universe after the temperature came down (around 400,000 years after the Bang).


The CMB is important to study as it represents the farthest we can go back in time using light signals. The CMB distribution over the observable universe is not uniform (a Nobel prize was awarded in 2006 for related work) and can be used to test different theories of the early universe.


One such theory is inflation, a theory that the universe experienced a period of rapid expansion soon after the Big Bang. Some years ago, the BICEP (Background Imaging of Cosmic Extragalactic Polarization) experiment was in the news with reference to inflation type observations. These observations eventually turned out to be due to galactic dust.


The advantage of situating a telescope at the South Pole is that the place offers very little humidity or clouds (easier to detect signals), is at a high elevation (less atmosphere between the telescopes and the sky), and the night lasts for 6 months (!).


ii) The IceCube (not an acronym) detector is looking for high energy neutrinos. Such detection events could help identify sources of high energy cosmic radiation, provide indirect signatures of dark matter, and help warn of supernovae.


IceCube actually consists of thousands of detectors buried a kilometer and a half into the ice (see this video for more about the detectors). Neutrinos pass through most matter, but once in a while they interact with water molecules. This interaction can produce a flash of light, which is what the IceCube detectors look for.


The advantage of having a neutrino detector at the South Pole is that a large amount (a cubic kilometer - hence IceCube) of clear and stable ice is naturally available to act as a detector for the neutrinos.


iii) Other important labs at the South Pole include ARO (Atmospheric Research Observatory) and SPRESSO (South Pole Remote Earth Sciences Seismological Observatory). The ARO takes advantage of the fact that the South Pole has the cleanest air on the planet.


Seismically, the Pole offers a very interesting opportunity. When events like large earthquakes happen, they cause the earth to ring, like a bell. These vibrations contain information about the constitution of the planet.


Elsewhere, the vibrations are complicated by the rotation of the earth about its own axis. The South Pole, which contains the axis of the planet rotation, is immune to these complications. It's a good place to 'listen' to the earth.


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