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

In a letter to Physics Today Roger Musson writes that the terms "Stone Age," "Iron Age," etc. refer to the material used most commonly to construct knives. This means we are currently in the Stainless Steel Age, possibly changing to the Plastic Age. By some reasonable measure, when would the transition happen?
2009-05-28 Thursday 17:37:37
Many people have jaws too small to contain thirty-two teeth, and have to have their "wisdom teeth" extracted. When did this practice become widespread? And how common is it to have an unusual number of teeth?
2009-02-24 Tuesday 12:41:14
A black hole at the end of its Hawking evaporation radiates with some very large power. But the high-power period doesn't last very long, since the mass is so small. Apparently the overall luminosity is small enough that it'd be hard to see a radiating black hole outside the solar system. What limit can you set on the density of very small black holes knowing only that, say, there are none in the room right now?
2009-02-04 Wednesday 22:19:29
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
Among the different Nobel prizes, there is a big spread between when work is done and when it is rewarded. The physics prizes seem to go to people whose work decades ago has shaped research since, while the peace prizes seem to go to people who are actively doing notable things right now. What's the distribution of times between doing something noteworthy and winning a prize for it? What about less famous prizes?
2008-10-08 Wednesday 10:54:38
Fresh Air interviewed Katharine Jefferts Schori, the primate of the US Episcopal Church, who has a doctorate in oceanography. Are advanced degrees in the sciences more common, or less common, in the clergy than in other nontechnical fields? How does the frequency change across different denominations?
2008-10-08 Wednesday 10:27:03
If Hawking's connection between black holes and thermodynamics is right, astrophysical black holes --- for which general relativity predicts everything bizarre happens well inside the horizon, and for which there are observational evidence --- are at the zero-temperature limit. What's the "warmest" black hole for which there is observational evidence? What's the transition "temperature" where quantum gravity starts to matter?
2008-10-06 Monday 19:45:48
An observation by Consumer Reports, that breakfast cereals marketed to children aren't terribly nutritious, has gotten some evening-news press. The main contribution of the Consumer Reports release seems to be that they bought a bunch of cereal and read the nutrition labels. What's new here? Has the composition of existing products been tweaked? Have some sweeter brands been introduced to replace healthier ones? How do these sorts of news blobs correlate with sales, or with marketing spending?
2008-10-06 Monday 12:29:26
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
I have heard it repeated a few times now that, in some counting, the human body is "mostly" bacteria. Is this number of cells? biomass? genetic information? Wikipedia cites a 2005 "mini-review" in Anaerobe. How much of the human body and its function are bacterial in other interesting metrics?
2008-09-22 Monday 10:40:07