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:
o
o
o
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

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Older questions

"When you get down &mdash and you will &mdash about the state of society or the level of intellectual attainment in the modern helter-skelter culture of so much of America, take heart from the fact that there are still more public libraries in this country than there are McDonald's."
— David McCullough, Commencement 2001, University of Delaware
Is this on track to change? When?
2009-06-05 Friday 07:52:43
I can make a partially deflated helium balloon neutrally buoyant by trimming bits off its string. How big are the variations in the "right" counterweight in an ordinary room?
2009-04-22 Wednesday 12:52:43
Computers have fast storage with limited space (RAM) and slower storage with fewer overall limits. How could this set of constraints change and make computing fundamentally different? How would similes about how "your brain is like a computer" change? Is there a better model for the brain?
2009-02-23 Monday 15:23:33
There's a theorem in control theory that sets limits on how quickly the gain of a feedback system can change with frequency without driving oscillations. This is the logic behind using the integral and/or the derivative of the feedback signal in mechanized control systems. One factor in the current financial disaster is tension between short-term and long-term risk, a problem that also appears in smaller-scale "markets." Suppose this tension were reduced by, say, paying fund managers with investments less liquid than cash, in some quantifiable way. Are cash commissions guaranteed to have boom and bust oscillations? Do oscillation-free commission schemes exist?
2008-12-31 Wednesday 10:03:07
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
Supposedly volcanism on Io is caused (or enhanced) by tidal heating from Jupiter. What power does tidal heating dissipate in the Earth-Moon system?
2008-10-23 Thursday 13:03:59
What makes glassy smooth patches on the surface of a larger body of water? Why are the patches partially stable against rippling from outside?
2008-10-23 Thursday 06:05:41
The Economist claims that some 1200 people have died crossing from Mexico to the US since 1990, compared to about 300 killed trying to cross the Berlin Wall during the 28 years it was up. Fatalities per mile? Fatalities per legal crossing? Estimates of successful crossings?
2008-10-11 Saturday 09:54:20
Suppose I wanted to check the accuracy of an ensemble of weather forecasts (e.g. "30% chance of rain tonight"). What's the right metric for doing this?
2008-10-09 Thursday 10:35:34