Built on Facts

Probably not.

I had an interesting question posed to me recently: how frequently does the sun emit photons with an energy greater than 1 TeV? All of you know about the experiments going on at the LHC, where particles are accelerated to an energy which is equivalent to an electron being accelerated through a potential difference of…

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…

Quick, hit the brakes!

A reader emailed me a fun question from a physics exam he took, along these lines: A car driver going at some speed v suddenly finds a wide wall at a distance r. Should he apply brakes or turn the car in a circle of radius r to avoid hitting the wall? My first thought…

A review of an odd but beautiful pop-physics book.

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…

Gun Control Debate with Mark, Pt. 2

Gun violence is bad. Gun laws have very little to do with it.

The Physics of the Ponytail

The first major computer-animated film was Toy Story. It had a few human characters, most prominently Andy (who spends most of the film wearing a hat) and Sid (who sports a buzz cut). The focus of the film is on the plastic toys. One of the major reasons for this is the fact that toys…