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

[none]

Older questions

Arguments about the safety of high-energy experiments sometimes cite the rate of high-energy few-particle collisions when cosmic rays hit the moon. What's the production rate for making transuranic elements from this process? What fraction of the universe's element 118 was made in earthbound accelerators?
2009-06-11 Thursday 15:34:41
Children's medicines come suspended in goopy liquids. Some part of the medicine always stays behind in the measuring spoon. Do dose estimates like "3/4 teaspoon twice daily" include a correction for the left-behind part of each dose? Do different types of dosing cups make a difference? Or do other factors introduce more uncertainty?
2008-12-29 Monday 19:14:27
CSX has been advertising that they "move a ton of freight 400 miles on a gallon of fuel," or suchlike. This seems extreme, like a cherry-picked statistic. Where does it come from? (more)
2008-11-20 Thursday 10:11:10
My fan-driven humidifier makes my house feel colder. How much heat does it pull to vaporize the water it does?
2008-11-14 Friday 16:59:35
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
If you pull two connected blobs of Silly Putty apart slowly, the thread between then stretches plastically; if you pull them apart quickly, it fractures cleanly. What sets the threshold? How sharp is it?
2008-10-20 Monday 16:16:27
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
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
What's the pressure inside an unopened soda bottle (or can)? What's the rate at which CO2 comes out of solution at ambient pressure? How much does the bubbling change the temperature of the liquid?
2008-09-23 Tuesday 19:19:09