In the period immediately following the Big Bang, all matter was hot. An explosive cloud of light and elementary particles moved outward and, after the first few hundred thousand years, began to cool. This is mostly a product of the spreading out of matter, and as the universe expanded the matter that made it up cooled further and further. This process was accompanied by the release of intense radiation in the microwave range, and much of that radiation is still hurtling through space. When it falls on Earth we can collect it, and a full accounting of the so-called Cosmic Microwave Background Radiation (CMBR) can give us a snapshot of what the universe looked like in those early aeons of cooling.
The South Pole Telescope, which collects this information, is aptly named. It was placed at one of Earth’s coldest extremes to avoid water vapor in the air; only Antarctica’s dry atmosphere will allow enough of the roughly 2 millimeter radiation to reach the collector. The dish itself is more than 30 feet across, bouncing microwaves to a camera built from the ground for this telescope’s research team. The detector is built around a superconducting thin film which loses superconductivity when heated. Even just the impact of a CMB ray imparts enough heat to cause a noticable change in conductivity.
The CMBR has actually been mapped several times already by projects like the Cosmic Background Explorer, or COBE, and is now known in exquisite detail. What the South Pole Telescope does is look at this information to answer much more modern and specific questions than ever before. Specifically, what can the state of the early universe tell us about dark matter and dark energy?
They’re hoping, quite a lot. Very little concrete information is known about these two quantities, which together are estimated to comprise 95% of the universe. But one thing that is known is dark energy can affect the formation of galaxy clusters and super-clusters.
These mega-features of the universe have shifted the path of the CMBR rays as they have traveled these past several billion years. By studying the characteristic shift in the microwave radiation signature, these researchers hope to be able to infer something about the dark energy that caused it.