And why is that?

How about the clickety-whir of a rotary dial telephone? I used to surprise people by being able to dial phone numbers using the hang-up button instead of the dial. If pressed rapidly enough, a series of 9 hang-up clicks had the same effect as dialling a "9", 8 clicks dialled an "8", and so on.

This trick continued to work long after tone dialling became the norm. For all I know it still works today; it's been a long time since I tried it.

I hadn't heard that Pythagorean example before. It really is surprising. Here's another math example that may surprise people:

Imagine that the Earth is a perfect sphere, and a rope is laid all the way around the Earth at the equator. The rope would be approximately 24,900 miles long. Now imagine that the rope is to be lifted exactly 1 foot off the ground all the way around. How much longer would the rope need to be?

Answer: A bit more than 6 feet. (2 to be exact).

They may or may not store his password as plain text. It's possible that the e-mail was generated dynamically when he entered his password in some form, while the password was in memory. They still might have used some kind of hash for permanent storage.

I'm a fan of mechanical keyboards and intentionally sought one with adjustable backlighting. My Lenovo ThinkPad also features adjustable keyboard backlighting.

Both these keyboards are hugely helpful to me for the simple reason that I often use my computers in low light or darkness. This allows me to limit my exposure to light when working late, and thus avoid disrupting my circadian rhythm due to the effect of light on the suprachiasmatic nucleus.

So, yes, seriously. Lights.