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Probably not.

Everything in Pi… maybe.

George Takei posted the following thing to Facebook recently: It got reposted by a bunch of people and provoked a tremendous amount of discussion (for a math topic, anyway), much of which was somewhere in the continuum between merely wrong and psychedelically incoherent. It’s not a new subject – a version of the image got…

Why are clouds white?

Why is the sky blue? It’s a classic question – probably the classic question of the genre of explanatory popular physics. The famous short version of the answer is that Rayleigh scattering by air molecules affects short-waveength light more than long-wavelength light, and so blue light tends to get scattered in random directions to create…

Light from a Hairbrush

Question from a reader: Pick up a comb, rub it with your hair and you have got some electric charge. Now shake it and you are generating an electromagnetic wave. Am I right? Yes indeed. So why don’t we see light emitted when we brush our hair? Let’s run some numbers. If you wiggle around…

The human eye is sensitive to a portion of the electromagnetic spectrum that we call visible light, which extends from around 400 to 700 nanometer wavelength, peaking in the general vicinity of greenish light at 560 nanometers: Here’s the intensity (formally: power per area per unit solid angle per unit wavelength – whew!) of the…

Ok, so this isn’t really physics as such, but it’s pretty fascinating. There’s a very large online community called Reddit in which users submit links which interest them. These links come with two little arrows beside them, and the users can vote the link up or down. Here’s a screenshot of how the website looks…

Less Than Absolute Zero

I’m sitting in a hotel in Utah at the PQE 2013 conference.  As I write this, the temperature is a rather brisk 19F. (For everyone else in the world, -7.2C) That’s not cold at all to some of you, but some of you didn’t grow up in south Louisiana. Either way, on the Kelvin scale…

Why calories can be complicated.

The Shadow Knows

On shadows, when they work, and when they don’t.

Interference – on the moon!

Wow, lots of moon posts these days.  This one is going to talk about a question left by commenter ppnl a couple posts back: ppnl: So could you use a pair of one meter telescopes a kilometer apart to create a point of constructive interference on the moon as small as what would have been…