New Page at the Top!

So there’s been something I’ve been wanting to start for a while, but waited until I learned more about how WordPress works (I am clearly not a web designer yet). You’ll notice a new link at the top titled “Trivial Explanations” (and also a new blog category with that name). In addition to posts where I look at science or its applications in the news, I also want to start giving some explanations of the concepts that are commonly referred to in science/tech journalism stories without much explanation. For instance, in the post on masers, many of the articles I linked to mentioned that masers could be good amplifiers for cell phones but didn’t explain why, while I briefly mentioned the relevant property was stimulated emission (the SE in LASER or MASER). I also plan on explaining things that might not be relevant to further off applications, but just appear in lots of papers anyway, to build up your background in seeing how things might be related (for example many materials are “doped”, but that is almost never explained in news pieces because it’s a basic step in the process). If you follow XKCD, think of it as a more practical (or less awesome) version of What If?

With that in mind, I need things to explain! So if you can think of anything you hear about in the news or in your life that you don’t understand, please send me your requests for desired explanations. For now, leave a comment on this post. I’ll try to come up with a better system in the future. (I’m a bit paranoid about linking my email)

The Gift of Knowledge

As a belated Christmas gift to readers of my blog (thank you!), I thought I would help answer what is probably one of the nerd sniping-est comics from XKCD.  It turns out the answer is more biology than physics.  The girl in the comic is right in questioning her mother’s answer; violet is a shorter wavelength than blue (if you remember your Roy G. Biv acronym ordering the colors of the rainbow, you’ve also listed the colors in order of decreasing wavelength).  It actually turns out that indigo and violet light is scattered well in the sky.  You just don’t see it because your eyes aren’t ideal detectors of light wavelength.  The reason you can observe different colors is because you have different cone cells in your eye, and each one reacts to a different part of the visible spectrum.  We only have three though, and they don’t respond to all the colors equally.

Response of cone cells to light, each curve is a different kind of cone cell

The blue curve which represents the cone that picks up short wavelengths is really sensitive to light at around 450 nm.  This wavelength represents the shorter end of what we consider “blue”, which goes up to about 500 nm.  The shorter wavelengths are “violet”.  As you can see, the response drops off really quickly on the shorter end.  This means that while there might be violet in the sky, you register the blue more in a mix of purple and blue.   The Georgia Tech researchers in the MSNBC article actually say you perceive a mix of blue and violet the same as a mix of blue and white.  The article the graph comes from also talks more about how the combination of different color sources affects your perception.

How we see color is actually a very complicated subject and isn’t just a straight up application of optics.  Spectroscopy is a branch of physics that studies how different wavelengths of light interact with matter.  Photometry and colorimetry are branches of science that study how people can actually perceive these wavelengths.  This includes factors like the structural aspects of your eye (like the chemical/physical behavior of the cone cells) as well as processes that go on in your brain, as seen in the famous checker shadow illusion.