Here are some thoughts gathered as I was searching for information on the recent direct evidence of gravitational waves found by the BICEP2 collaboration. I may first define a few terms though. Also, since this is for the benefit of sharing only with friends, I outright steal sentences from other articles. I aim to reference them though.

First, I here is the best article I found for the layman, which links to this nice article in Sky and Telescope magazine.

Cosmic Microwave Background (Sources: 1, 2)

"... among the most carefully examined piece of evidence for the Big Bang is the existence of an isotropic radiation bath that permeates the entirety of the Universe known as the "cosmic microwave background" (CMB). In 1964, two young radioastronomers, Arno Penzias and Robert Wilson, accidentally discovered the CMB using a well-calibrated horn antenna. It was soon determined that the radiation was diffuse, emanated uniformly from all directions in the sky, and had a temperature of approximately 3 Kelvin (2.73K). Initially, the two young scientists were bereft of a satisfactory explanation for their observations, and considered the possibility that the CMB may have been due to some undetermined systematic noise. However, it soon came to their attention through Robert Dicke and Jim Peebles of Princeton that this background radiation had in fact been predicted years earlier (1948) by George Gamow, Ralph Alpher, & Robert Herman as a relic of the evolution of the early Universe."

Reference 2 above gives a beautiful description of the temperature fluctuations in the CMB. "This lumpiness affects the CMB largely because of gravitational redshifting. Radiation emitted from a dense spot in the sky has to fight against a bit of extra gravity as it heads toward our detectors. When it leaves that gravity well, the radiation will be a little less energetic than radiation emitted from a less-dense region, so that spot of the sky will appear to be a little colder. A map of the apparent temperature of the CMB across the sky thus gives you a map of the density of matter in the early universe." (emphasis added)


Gravitational Waves

Polarization (Sources: 1, 2)


Polarization refers to a light wave that prefers to vibrate in a particular orientation rather than randomly. Any polarization pattern can be described by two distinct components. These two polarization modes are convenient because they are independent of the choice of a coordinate system. One mode of polarization 

Circular polarization of light
Linear polarization of light