Boomerang

A couple of weeks ago, my colleagues in the Boomerang Collaboration, spread out over the US, Italy, Canada, France and the UK, released five papers analyzing the data from the latest flight of the Boomerang instrument, over Antarctica in January 2003 (check this out for information from my fellow Boomerangers on what it's like down near the South Pole).

Boomerang is an experiment which measures the Cosmic Microwave Background, or CMB (there are some tutorials on the physics behind the CMB here, here and here). Boomerang, along with the Maxima experiment (with which I'm also fortunate to be involved) produced the first high-resolution maps of the CMB back in 2000, measuring the tiny -- one part in 100,000 -- fluctuations around the mean temperature of about 2.72 degrees above absolute zero. The pattern of these fluctuations on the sky lets us measure the geometry of the Universe (which is equivalent to asking the question, What happens to light rays that start off parallel to one another? Do they converge, in which case the universe is said to be "closed" -- curved like a ball? Do they diverge, in which case the universe is "open" -- curved like a saddle, or a Pringle's potato chip? Or, do they stay parallel, making the universe flat? In 2000, these experiments proved what had already been surmised -- the Universe is indeed flat, so parallel lines are indeed parallel forever. Since then, experiments have measured the CMB at higher and higher resolution and accuracy, and allowed us to understand even more about the origins of the Universe.

So why is our new data so exciting? First, we've made some of the most sensitive measurements of the CMB ever made -- similar to our 2000 measurements, but with error bars many times smaller.

Second, and even more exciting, we've measured the polarization of the CMB. In addition to the CMB temperature measured by the 2000 experiments, the CMB is also polarized, which means that the CMB photons tend to point more in some direction on the sky than others. This reflects some of the same properties of the Universe as the temperature, but is a completely independent (and much harder!) measurement. Although the CMB polarization has been detected by the DASI, CBI and CAPMAP experiments, these new results are the full maps of the CMB polarization (although I must disclose that they are still mostly noise; we can only see the cosmic signal by taking averages).

Links to the Boomerang papers here, and on astro-ph:

Over the next few months, stay tuned for more CMB temperature and polarization data from Maxipol, ACBAR, WMAP and more!