The balloon is actually just transportation for the experiment. All the science is being done by an array of six radio telescopes known as SPIDER, which is short for Suborbital Polarimeter for Inflation, Dust and the Epoch of Reionization. SPIDER will spend most of this month circling Antarctica to gather data on the cosmic background radiation. The experiment is being managed by scientists from Caltech and Princeton, who hope to detect gravitational ripples caused by inflation shortly after the big bang. This would score big points for proponents of cosmic inflation.
If this sounds familiar, there’s a good reason. SPIDER is actually the companion project to BICEP2, which made news in mid-2014 when researchers announced they had acquired data that appeared to show “curly” B-modes of polarization in the cosmic microwave background. These gravitational echos are predicted by general relativity, and are seen as solid evidence for cosmic inflation. This hypothesis holds that the universe expanded rapidly when it was just 10-36 seconds old. This would explain many of the properties we observe in the universe today, like the overall uniformity in all directions.
Shortly after the BICEP2 announcement, other scientists called into question the accuracy of the data. The team eventually conceded that the radiation patterns observed by BICEP might have been a result of dust interacting with the Milky Way’s magnetic field. This is exactly what SPIDER is designed to rule out. It’s six radio telescopes will be able to view much of the sky on its trip around Antarctica. SPIDER will observe the cosmic background radiation at two different wavelengths in order to rule out interference from dust. Thus, gravitational waves detected by SPIDER should be the genuine article.
You may be wondering why a balloon floating above Antarctica is the best way to gather this data. Getting the instrument above most of the atmosphere is imperative to having an unobstructed view. A space mission would do this as well, but launching to orbit is much more expensive than sending up a balloon. As for the location, radio telescopes work best where there is very little moisture in the air. That’s why the Atacama Desert in Chile is also a popular location for cosmology research.
When SPIDER lands in a few weeks, the team may be able to determine whether BICEP2 was onto something, or if it missed the mark. Then it will be up to the scientific community to decide what that means for cosmic inflation.