Lead Pencils : a big waste!

One repeats the following process with lead pencils.

A. Sharpen to a cone pointed tip.

B. Flatten the head through use.

So if you divide the "cylindrical" lead structure in the pencil along the length into mini cylinders. Then you basically remove 67% the volume by sharpening the mini cylinder and using the conic remainder.

So you lose at least 67% of the lead in the pencil by sharpening. You can save unnecessary waste of wood and lead by not using lead pencils.

TIP: A cylinder has 3 times the volume of a cone of the same base and height.

Why have Fingerprints?

Some ideas:

1. Friction and increased surface area.
2. DNA coded unique for each human specimen
3. Increased sentitivity due to blood flow.

In fact this post on NPR suggests fingerprints may not aid in friction and in fact reduce contact area. The study mentioned in the post still leaves most possibilities open to scientific debate.

Total Solar Eclipse

making sense of the absurd

If you have time on your hands, then the following piece is recommended for reading; Making Sense of the Absurd. It sort of goes through a list of things that starts to blur the line between absurd, right and wrong. It isn't making the case that religion isn't absurd, but that we probably take too many scientific statement for granted. for instance:

7. Parallel lines never meet.
8. The sum of the interior angles of a triangle is 180°.

Well, these aren't quite accurate. There's an implicit constraint on these statements that they are true only in euclidean (planar) geometry. In non-euclidean geometry, these statements can take wild turns. For example, on the surface of a sphere like our own planet, we can start at the north pole, walk south 1 mile, east 1 mile and north 1 mile and return exactly to our starting point. Our turns were approximately right angles and our return also consists of a right angle, meaning that the triangle we walked had interior angles summing up to almost 270° (to the nit-picky, this isn't strictly true--in order to get exactly 270°, we'd need to walk all the way down to the equator, but I'm too lazy to walk that far). And while we're talking about the globe, we can observe the long parallel longitudinal lines to see that they can indeed meet twice: once at each pole. In other more intriguing spaces, such as lobechevskian space whose shape is often compared to that of a saddle, we can find parallel lines that intersect exactly once. And if the real-world example of the globe isn't enough to discredit the universality of propositions 7 & 8, we could look at the math supporting Einstein's theory of special relativity which relies on non-euclidean math to derive its results.

profiling shooter?

livescience.com you can't profile school shooters

One of the problems, they say, is : There are far too many people who are depressed and lonely are not mass-murderers. And how ever finely you make up a profile, the number of false-positives* will be more than true mass-murderers that fit that profile. This reminds of the Bayesian estimation "paradox" that Arunn on Nanoscience posted a while back.

Example: False positive in a medical test (example taken from [1])

A “false positive” in medical terminology is a situation when ... a person not actually having a particular disease or conditions may be returned a positive result in a test. ... Suppose that a test for a disease generates the following results.

(1) If a tested patient has the disease, the test returns a positive result 98% of the time, or with probability 0.99
(2) If a tested patient does not have the disease, the test returns a negative result 96% of the time, or with probability 0.96.

Suppose also that only 0.1% of the population has that disease, so that a randomly selected patient has a 0.001 prior probability of having the disease. The question now is what is the probability that a positive test results in a false positive?

from back of the envelope calculations:

If there are 1000 people, 1 person has the disease. of the 999 people only 96% were detected. so 39.96 were detected positive, but don’t have the disease. So only 1 in 40 people detected to have the disease really do have the disease.

equality indeed (joke alarm)

Kurt quipped on the CT forum: "We have been a horrible animal. after the Spanish inquisitions, the two world wars, Hiroshima, Roman games. Its clear the earth is trying to get rid of us." Joyce Carol chimed in the middle with the question "But which sex is doing this stuff?" without a second thought Kurt Vonnegut made the snarky comment "Women are no good at doing science, you know? We discovered that at Harvard." (see the video)

I thought this was a nice short exchange for more reasons than one. Kurt may have meant that - In Cat's cradle Kurt talks about the detachment of scientists from the impact their discoveries have on the world, however disastrous they may be. Especially that this is independent of gender. But if you twist his statement it could also mean "If Women claim they can do the most wonderful discoveries just as well as men have in the past, they should accept with calm deference that they are capable of committing the very same horrors as well."

History has shown only few contributions of significance from women. Naturally so. So why would anyone search history to point to the potential of women or the capacity of women to be creative as evidence? Rather, why not believe in the inherent equality of men and women as the basic hypothesis of natural law? Desmund Tutu described of man (and women) "he(she) is capable of most evil acts as he(she) is of the most elevated."