What the heck is b-mode polarization?

This has to do with the Cosmic Microwave Background. You know, that's the thermal energy that's left over from the Big Bang. The discovery of this leftover energy is proof for the Big Bang, and it has afforded cosmologists with the opportunity to test various theories about what actually happened then.

This background thermal signature isn't very hot. It's estimated to be 2.72548 plus or minus 0.00057 K. That's a very precise estimate. This energy signal is essentially weak but isotonic (uniform in all directions) microwave radiation at 180.2 GHz. It's sort of like a faint glow that's uniform all over the universe.

However, there are strange features in this background radiation. There are peaks of more intense radiation and sections where the radiation is less. These features are very faint. I won't go into the theory involved here because it's complicated and has to do with quantum effects that occurred at the time of the Big Bang.

I want to discuss the polarization of the microwave radiation. Yes, electromagnetic radiation can be polarized just like light (which is a form of electromagnetic radiation). The degree of polarization is small, a fraction of a Kelvin degree. There are two modes of polarization: E-mode and b-mode. These polarizations effects are blamed on gravitational lensing and gravitational waves from the Big Bang. In fact, part of the b-mode polarization is the result of gravitational lensing effects from across the entire universe, nearly 14 billion light years, and it's very hard to measure.

Polarization is where electromagnetic waves are aligned in one direction. Think of Polaroid sunglasses that block out glare using polarizing lenses. Think of polarization of the microwave background energy as being a subtle curl or twist in the microwave signal.

B-mode polarization has two causes. One is the initial cosmic inflation right after the Big Bang that caused gravity ripples or waves that are still flowing, and gravitational lensing from massive galaxy clusters later on.

Why is this so important? The main reason is that it provides observational evidence for the inflation theory. This is a theory that proposes that the universe inflated exponentially just a fraction of second after the Big Bang created it. This crazy inflation at greater than the speed of light created ripples in spacetime that we can still detect by means of this b-mode polarization of the cosmic background microwave energy left over from the Big Bang. You can think of this b-mode polarization as something that was imprinted onto the microwave background photons from only a tiny, tiny fraction of a second after the Big Bang. This b-mode polarization appears as slight curling of the orientation of the cosmic microwaves, which appear as density fluctuations (relative to temperature variations) in the image.

This b-mode polarization was allegedly detected in 2014 by the BICEP2, or the Background Imaging of Cosmic Extragalactic Polarization, project. This team used a telescope at the South Pole. I think that this calls for breaking out the polarized champagne, but it's probably frozen.

Thanks for reading.