There are so many cool things in this article, but I’ve struggled to understand it so I’ve held it for 2 months…

Posted bychrisdolan 13 Comments on There are so many cool things in this article, but I’ve struggled to understand it so I’ve held it for 2 months…

There are so many cool things in this article, but I’ve struggled to understand it so I’ve held it for 2 months before sharing it. Bear with me, because I’m still not sure I understand it correctly…

Why does polarization matter? The light we detect from the Cosmic Microwave Background has been traveling unimpeded through space since shortly after the Big Bang. The polarization has barely changed in those billions of years. Polarization is caused by asymmetric reflection or scattering of light off the last thing it hit, so if the CMB light is polarized, it’s because matter was asymmetric in the earliest days of our universe. The degree and types of polarization tells us details about the asymmetry.

Detecting polarization We usually do this by using reflecting materials that cancel out one kind of polarization but let another kind through. By using such a filter twice (or more) at different angles and measuring the difference in measured brightness, we can infer the degree of polarization. If the two measures have the same brightness, the light we measured was unpolarized. The best way to do this is two reflecting surfaces that are exactly quarter of a wavelength separated from each other. Light reflected off the top reflector can cancel light reflected from the bottom reflector. (mumble something about why this affects just one polarization…)

B-mode polarization I really don’t understand what this is… Originally I thought it was related to linear- vs. circular-polarization but now I’m not sure. What I do know is that it’s hard to measure, and it doesn’t work with quarter-wave-plate technique. However, it can be useful for measuring a different type of Big Bang asymmetry from what can be measured with “E-mode” polarization, somehow…

Magnetic mirror Regular mirrors reverse the polarization of light, which I think is why the quarter-wave technique works. Magnetic mirrors (which are really nanoscale engineered surfaces) don’t reverse polarization so you can cancel (and thus measure) a different form of polarization efficiently. How does the nanoscale structure prevent flipping the polarization? I really don’t understand that part. But it sounds cool!

https://phys.org/news/2016-12-magnetic-mirror-gravitational-early-universe.html

13 replies on “There are so many cool things in this article, but I’ve struggled to understand it so I’ve held it for 2 months…”

  3. Joe Carter thanks, yes, I had found that one. “B” is the usual physics variable for magnetic field vs. “E” for electric fields. And mathematically I understand that the distinction is zeroing out grad or curl, but what I lack is an intuition what creates B-mode polarization, and none of the articles I read explained it shallowly enough to help.

  4. Gravity oh so strange a frequency, so what about objects that have 0 empty space in them even at a quantum scale or objects that are moving faster than one mile every flank second. What havent thought on this hum well black holes and singularities do have an enormous role in all of this. You will have to accept that the speed of light is only the speed limit for the “visible” universe and that there is nothing that says objects cant move faster than light.

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