Archive for the ‘science’ Category

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Lazy cat

August 15, 2008

Yesterday I had to defend my internship report; everything went better than I could’ve expected. I almost couldn’t stop talking, and my presentation was between 45-50 minutes (while 20 minutes was sufficient). Anyway, the questions afterwards were not that difficult, and all in all they were happy with the way I had worked during my internship.

Now I’m at my parents for a few days, and when I was goofing around with one of our cats, I had the chance to stare right into the belly of the beast:

Straight into the belly of the beast

Straight into the belly of the beast

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Cosmic background radiation

September 1, 2007

I finally finished my course on Quantum Optics; in the book we used was a question about the “number of photons per unit volume excited in a cavity at temperature T” (Loudon, Quantum Theory of Light). After deriving a formula for this, you can show that the cosmic background radiation contains about 4-5*10^5 photons per litre.
I always got stuck at the same point, but now I finally know how to solve this.

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Read the attached pdf if you want to know the solution.

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Hurricanes and global warming

July 19, 2007

There’s an article in Scientific American (July 2007) about the relation between global warming and hurricanes. I learned a few things from this:
A cyclone, typhoon and hurricane are the same thing; they only differ in the region where they are observed.

How do hurricanes form?

  • The sun raises the Sea Surface Temperature (SST)
  • Water is evaporated to release the excess heat
  • The moisture raises and condenses into rain
  • When raindrops are formed, latent energy is released
  • The heat goes up and creates ‘updrafts and thunderclouds’
  • Beneath this area, a low pressure zone is created which ‘sucks up’ moist air
  • Due to Coriolis forces due to the earth’s rotation a vortex is created
  • “The eye” is a low pressure area at the bottom of this vortex
  • Due to the circling hot air, the rising air dries and gains energy
  • Some of this air is absorbed again in the eye, and some of the air ‘spirals out’ over a large area (many kilometres)

How hurricanes form - Copyright Scientific American

The different seasons play a role as well:
The energy released when raindrops form heats the atmosphere

  • In winter, the heat goes up and radiates into space
  • In summer, the heat rises to higher altitudes in tropical areas

Further ingredients needed to start a hurricane:

  • high SST (>26 degrees Celsius); SST may rise due to the greenhouse effect
  • plentiful water vapour
  • low pressure at the ocean’s surface
  • weak wind shear between low and high altitudes (strong winds destroy emerging vortices)

The rising SST may (partly) originate from the greenhouse effect. However, in 2004 and 2005 we saw a lot of hurricanes, but 2006 was a quiet year.

Some scientists believe this is due to the “Atlantic Multidecadal Oscillation” (AMO), which is basically a cycle in which temperatures rise and fall. But simulation shows that this can’t be the whole story (the temperature difference is only 0.5 degrees Celsius). The models do show (as far as they are correct; which is difficult to assess) that human action is likely a cause of the rising SST. Approximately 0.6 degrees Celsius can be attributed to human action (probably without the AMO) since 1970. It is noted that this may sound small, but only one degree can change the storm’s intensity to a higher category. This may well explain the rise in the number of ‘high’ category hurricanes.

The fact that 2006 was a quiet year (in stark contrast to 2004 and 2005) is due to a different factor. In 2004/2005, El Nino warmed the ocean. La Nina cooled the ocean the subsequent year. This is explained in the remainder of the article.

The article concludes that the hurricane threats are likely to get more severe.

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An argument against tax increase on alcohol (in Russia)

June 16, 2007

Now an article from New Scientist about alternatives to alcohol used in Russia. The article opens with the following:

A shocking 43% of deaths in working-age Russian men result from drinking alcohol not meant for human consumption, such as cologne and cleaning agents, according to a new study.“, which helps explaining why Russian men have the lowest life expectancy at just 59 years!

The alternatives to alcohol are cheaper and have a higher alcohol content. On the positive side, when drinking eau the cologne, burping may give a more pleasant smell… This must be an attractive feature to the women ;).

Not surprisingly, the people that drink the ‘alternatives’ to alcohol, have a much higher risk of alcohol related death.

Finally some shocking figures:

  • Russian men who drink non-beverage alcohol have a five-times greater risk of alcohol-related death (such as liver cirrhosis and alcohol poisoning) than those who do not consume these products
  • Men who drank only non-beverage alcohols had up to a 20-times greater risk of death
  • These figures are probably higher, as the research didn’t include men who lived alone, or men who lived on the streets
  • Alcohol is linked to 72% of murders and 42% of suicides in Russia, according to 2005 figures

Bring on the Soviet-Russia jokes ;).

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Antibacterial soaps

June 16, 2007

In the category ‘Weird Science’ an article appeared on the site of Scientific American about antibacterial products. More and more antibacterial products are used, but to what avail?
Normal soaps wash away ‘nonspecifically’, “meaning they wipe out almost every type of microbe in sight—fungi, bacteria and some viruses—rather than singling out a particular variety.
On the other hand, after applying antibacterial products, conditions may arise which may actually help the resistent bacteria, because not all bacteria may be killed. In fact, “a small subpopulation armed with special defense mechanisms can develop“, so that these bacteria develop a tolerance and reproduce. This, in turn, may help the bacteria in growing resistant to certain antibiotics.
A problem that arises is that, at least in America, certain antibacterial compounds are found in “60 percent of America’s streams and rivers“, and may eventually end up in crops.
In the end, the advise is to wash your hands 3 times a day with regular soaps, and leave the antibacterial soaps at hospitals.

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Ringfinger response

June 2, 2007

From one “research“:

Kids with longer ring fingers compared to index fingers are likely to have higher math scores than literacy or verbal scores on the college entrance exam, while children with the reverse finger-length ratio are likely to have higher reading and writing, or verbal, scores versus math scores.

From different “research“:

The research, done at the University of Alberta and announced Wednesday, found a connection between the length of the male index finger relative to the ring finger and the tendency to be aggressive.
No such connection was found in women.

Testosterone promotes development of mathematical and spatial skills. On the other hand, more estrogen promotes development of verbal skills, which lengthens the index finger.

On the same page it is mentioned that the longer the ringfinger is, the larger the amount of testosteron during the pregnancy. More testosteron results in more agression (at least, it makes it more likely; nothing can be said about individuals, only about groups). So this perfectly explains why you see all the agressive bald mathematicians, with those leather jackets, tattoos with hearts of “Mama”, scars and such at the G8 demonstrations.

Remember though, that other things like “flawed brain chemistry, brain damage, genetic defects, an unhealthy psychological environment” all contribute to the behaviour, so one needs to be careful about deducing characteristics from future lovers.

Oh yeah, my ringfinger is approximately 13 mm longer than my indexfinger. Nothing unexpected, as people know me as a highly agressive vegetarian listening to 60s music, enjoying math.

(The reason the word “research” is between quotes, is because I’m not too confident in these types of research. There may be a correlation, but that doesn’t mean  there’s a connection (in the form of causation) between the two. I have to admit I didn’t read the original articles (which were published), but my expectations are too low to be bothered with it. Also, the amount of test-subjects in both “researches” is pretty low; add some statistics, and you can easily produce true lies.)

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Think more, get less

May 30, 2007

There’s an article in the June 2007 episode of Scientific American, also published on their site.It is written by Kaushik Basu.
It’s about the curse of rational choices when playing the “Traveler’s Dillemma” game:

“Lucy and Pete, returning from a remote Pacific island, find that the airline has damaged the identical antiques that each had purchased. An airline manager says that he is happy to compensate them but is handicapped by being clueless about the value of these strange objects. Simply asking the travelers for the price is hopeless, he figures, for they will inflate it.Instead he devises a more complicated scheme. He asks each of them to write down the price of the antique as any dollar integer between 2 and 100 without conferring together. If both write the same number, he will take that to be the true price, and he will pay each of them that amount. But if they write different numbers, he will assume that the lower one is the actual price and that the person writing the higher number is cheating. In that case, he will pay both of them the lower number along with a bonus and a penalty–the person who wrote the lower number will get $2 more as a reward for honesty and the one who wrote the higher number will get $2 less as a punishment. For instance, if Lucy writes 46 and Pete writes 100, Lucy will get $48 and Pete will get $44.

What numbers will Lucy and Pete write? What number would you write?”The point is, when you don’t think much about it, you’d choose $100. However, when you start thinking more, you’d write down $99: because if you write down $99, and the other person will write down $100, you will get $101, while the other only gets $99. Then you start wondering if the other person thinks the same… and you obviously don’t want the other person to have more money. So you reduce your amount to $98 (thinking the other person will write down $99), so you’ll get $100, and the other person only $96. And so on. In the end, you’ll arrive at $2. In this way, you earn a lot less then the naively chosen $100.

This problem is the same, the article explains, as the Prisoner’s Dilemma: “… in which two suspects who have been arrested for a serious crime are interrogated separately and each has the choice of incriminating the other (in return for leniency by the authorities) or maintaining silence (which will leave the police with inadequate evidence for a case, if the other prisoner also stays silent).”

A Nash equilibrium, is when there’s no benefit (put simply) to change your strategy: in this case the equilibrium is at $2 (the absolute minimum of choices). This is what Game theory predicts; but it conflicts with our intuition.

In experiments, the choice people make depends on the reward: when the reward is low, the choice will on average be higher. On the other hand, when the reward is high, the choice will be lower. This makes sense, because when the reward is high relative to the choice, it’s more advantageous to lower your choice. For example, if the reward is not $2, but $50, you wouldn’t want your choice to be too high: the penalty you’d get would severely impact your profits.

Then why do we make these choices, based on our expectations that the other person will choose a high number? The article suggests:
“Perhaps altruism is hardwired into our psyches alongside selfishness, and our behavior results from a tussle between the two. We know that the airline manager will pay out the largest amount of money if we both choose 100. Many of us do not feel like “letting down our fellow traveler to try to earn only an additional dollar, and so we choose 100 even though we fully understand that, rationally, 99 is a better choice for us as individuals.”

The moral: sometimes it’s good not to think too extensively about seemingly simple questions.