Tertiary Source

Ice tray stalagmite

2010-02-21 20:19:22
Look! I had a stalagmite in my ice cube tray.
an ice cube tray
what is that?
it sticks out against a card

Eleventy-one thousand eleventy-one

2009-08-14 09:08:00
Here's a million-to-one photo I took yesterday:
odo: 111111, 44 mph

Remember the significance of the three circles!

2009-07-10 14:57:28
When I was a freshman I took Philosophy 110. It was a big lecture, and the professor had a habit of rambling (which I mostly found entertaining); there was the customary falloff in attendance as the term went on. During one lecture the professor was working up to making three points and put some bullets on the whiteboard:
He then promptly distracted himself with a tangent about how boring people drive Fords, and whenever you see a Ford it's being driven by a boring person. After a couple minutes of this he turned back to the board and said, "I have no idea why I made these three circles. They must mean that boring people drive Fords." This got a chuckle out of the class, and he added, "Remember that! It'll be on the final."

Vaccine fears and risk tradeoffs

2008-12-26 11:28:25
This weekend's This American Life included interviews with some of the participants in this summer's measles outbreak. I learned about the outbreak from a somewhat overblown reaction from Phil Plait. From memories of Plait's older material, I expected a little lesson in conditional probability. Not finding one, I did an analysis of my own. I reached the surprising-to-me conclusion that, even with this summer's outbreak, the risk tradeoff between measles exposure and vaccine side effects is not totally unbalanced. My writeup at the time got lost in comment noise, so I'll condense it again here.

A duck from the Economist

2008-12-08 10:32:10

Here's a nice duck from the Economist. It's interesting that coups d'etat have become less common in recent years. It's also interesting that these commandos are reaching through the grid lines to pat the data.

Coups and attempted coups worldwide

Rail fuel economy

2008-12-05 01:04:24

Dylan Foley pointed out to me that my question about CSX's advertised fuel efficiency has previously gotten attention from FactCheck.org.

Musical Doppler self-sonar

2008-11-14 18:42:18

If you stand reasonably close to a road, the sounds of passing traffic get Doppler shifted: they start off high and end up low, "wheeeee-oooooom." Professional and amateur musicians have sophisticated training in recognizing frequency ratios. (Though, explicitly mentioning the relationship between frequency/wavelength ratios and intervals is more common when players of string instruments experiment with making harmonics.) How accurately could you estimate the speed of a passing vehicle by the sound it makes?

What's the antimatter content of a banana?

2008-10-21 11:06:37

Antimatter is strange, exotic stuff, right? Only produced in dangerous physics experiments? Leads to complete annihilation with ordinary matter?

Sort of. It's a question of quantity.

Recent questions


Older questions

Venoms have evolved independently in several different vertebrate lineages: in snakes and lizards, and in the platypus, and in one other mammal. What are the transitional stages for venom to appear? How would the appearance go in, say, a population of people?
2009-04-01 Wednesday 17:41:46
The Greenland and Antarctic landmasses are under a mile of ice. Supposedly if this weight were removed the landmasses would "rebound" out of the mantle. How high would they go?
2009-02-27 Friday 23:30:51
To an outside observer, an object dropped onto a black hole never actually crosses the horizon; it approaches the horizon asymptotically and light from it becomes more and more redshifted. Suppose I drop a room-temperature blackbody in a hole. How long does it take before the redshifted temperature is colder than the Hawking temperature of the horizon?
2009-02-27 Friday 23:24:26
Yesterday's solstice was the day when the northern hemisphere gets less solar irradiance than any other. In most countries this is "midwinter," but in the United States it's "the first day of winter." When did this label change?
2008-12-22 Monday 06:58:50
New "open" signs at restaurants, with bright red and blue LEDs, bring out some chromatic aberration in my glasses: viewed peripherally, the different-colored parts don't line up. Quantify? Why have I only just started to notice this?
2008-11-11 Tuesday 09:44:38
Passing traffic makes Doppler-shifted noises ("wheeee-oooom"). Useful trick: map between musical interval of the shift and the speed of the traffic? (maybe)
2008-11-11 Tuesday 09:38:19
Suppose I replace an incandescent light bulb with a more expensive, more energy-efficient, longer-lived light — a CFL, an LED, whatever — based on the expectation that it'll cost less over its life. How old does my incandescent bulb have to be before I actually save anything?
2008-10-28 Tuesday 21:42:08
When using χ2 minimization to estimate parameters from some data set, what fraction of the fits stop converging in the "wrong" place?
2008-09-28 Sunday 16:55:01
You can't interact with a physical system without disturbing it, though you can ignore the disturbance in the limit where ħ is small. Similarly, you can't interact with a market for some product (by asking or buying or offering or selling) without affecting the "market price" seen by others, but you can neglect that change unless your exchanges comprise a large fraction of the market. There is some correspondence here. Clearly it'd be easy to take this correspondence as justification for saying some really dumb things. Are there any useful insights there?
2008-09-26 Friday 14:50:23
Parity nonconservation in weak interactions can interfere with strong or electromagnetic interactions to produce parity-forbidden transitions or correlations. Without some unusual enhancement, the approximate statement "strong and electromagnetic interactions do not have pseudoscalar observables" is accurate to 10-7. What similar statement can one make about CPT conservation?
2008-09-21 Sunday 14:21:05