Friday, February 24, 2006

Scian Melt Nominations

The next Melt will be hosted on this blogspot page on March 1st. You can find more about The Melt here. If you have written a blog page on Science and/or India, you can make your nominations to melt [at] thescian [dot] com. The previous one, the 13th one, is hosted here.

The following places also carry further announcements and information: at shallow thgts and at Scian


12:NeoSagredo, 11:Shallowthgts, 10:Kyun, 9:Reflections, 8 and 7:Scian, 6:Geomblog, 5:Patrix, 4:Tiffinbox, 3:Sel.Amnesia, 2:Rathod, 1:Scian

Tuesday, February 21, 2006

Being Human and Science : Linkspress

Being Human can be tough. Especially in medieval times. Because of this, we came out for the better and turned out to be most social of animals, anthropologists say.

Now it is time for us to get back at them; the species in our neighborhood. Humans perceive animals, insects as sources of threats or infections. It turns out, we have been making the wildlife sick!
"With emerging infectious diseases of wildlife today there's almost always some human component," say Dr. Lewis, an NSERC-funded mathematical ecologist in the mathematics and statistics department at the University of Alberta, Edmonton, Canada.

in a landmark paper, he helped document how commercial salmon farms off Canada's British Columbia coast are a breeding ground for sea lice, a parasite that then infects young wild Pacific salmon. The research was the first to document the parasitic impact of commercial salmon farms on wild salmon in the Pacific Northwest.

When it comes to emerging infectious diseases of wildlife, Dr. Lewis says that public perception and policy needs to move beyond seeing "special cases" to seeing the constant role that people play.
Unlike the research above popular science need not be of good quality as much as having a wring of currentness to it (the be hip mantra!). Perhaps the blame lies with the schools and the science teachers for not being able to convey the pleasure of science. Here is a nice article about that.

Added 2/22:
Ice Ice Baby If you thought you knew why ice is slippery, think again! Even the scientists are not sure what the reason is, says a nicely written NY Time piece.

Science off the tap! To bring the science fervour to the public, Cafe Scientifique started in Leeds and slowly spread to other places including its now popular home in Denver, CO. People gather to disucss about all science topics that affect their life from genetics to cancer research.

Monday, February 20, 2006


Just to have fun with orientation, try making a Moebius strip. If you have a normal rectangular strip of paper, you can join one short end to the other to make a simple closed strip. IF you twist one end (by 180 degrees) first before joining with the other end, you have a Moebius Strip. The ants in the picture are actually on the same side of the strip, even though they appear to be on two sides. An ordinary strip has two sides (an inside and an outside), but a Moebius strip has only one side!

Think about that! :)

Take the normal rectangular strip and join the long ends to make a long cylinder. Just as in the case of the rectangular strip above, close the circles in the two ends of the cylinder in a simple way to make a hollow doughnut (a torus). What is the analogue of the Moebius Strip for the long cylinder? It is a Klein Bottle! A hollow doughnut has an inside and an outside, but a Klein Bottle does not. So it cannot hold any water as inside is also outside :P

Caveat: Klein Bottle does not physically exist in 3-dimensions (but in 4 dimensions!), so the picture is an illusion. I don't want you to get all cross-eyed looking at it. :P

Friday, February 17, 2006

Being on Cloud Nine

What would it be like if you were in the middle of a cloud? Can you Imagine millions of droplets of water floating around you? These droplets are very small, and they float around you without touching each other. This is how it would be to be among the clouds.[1] So is it all just water? Why don't they fall down? We can wonder what goes on up among those clouds, sitting here on the ground beneath our feet. (read my earlier blog to know about supercooling and crystallization).

The water droplets are so small that they can be kept afloat by small wafts of upward wind, more like a feather in the air that will float and float and float but will never fall to the ground. The droplets are kept from running into each other by the same air, which acts more like a foam cushion that keeps a high-jumper from bumping into the floor. You can imagine these droplets danced around by the wafts and yet not bumping into each other.

There is something more to clouds. Clouds are also very cold. So cold that it can be below -40 deg C (now you are having second thoughts about being in the cloud). You must have read my earlier blog and wonder: how can water remain unfrozen? The answer also lies in the same blog. For water to freeze, it needs points of crystallization. Up in the clouds these are provided by suspended particles (dirt) in the air. But as you can imagine, a cloud living so high is also far from the dust and dirt of the Earth![2] So it is very hard to find such dirt that can make crystallization to happen. So water droplets remain water droplets but at temperatures much below zero.

So all these droplets go as clouds from one place to another, to another. When do they ever come down as rain? Will they fall on me? The first question is easier than the second. So, we will answer the first.

As we understand it, supercool water (water below zero deg C) becomes unstable as the temperature decreases. Only the slightest disturbance is needed for it to freeze. So lower the temperature the less impurities are actually needed to cause the disturbance. After all, even in the clouds there are impurities, though not as many as on the surface of the Earth.

We know that warm currents and cold currents all have a thing going of their own, independent of the clouds. Where they come from, how they come, we don't care. But if enough cold winds come to make the supercool water droplet's temperature drop below -40 deg C, then crystallization can start. So droplets turn to ice and slowly the surface of ice (flake rather) becomes the source of further disturbance and the crystallization spreads through the cloud. There is an additional effect that happens here. There are wafts of wind blowing between the droplets. This air is rich in moisture (it contains water vapors) and on meeting ice, the moisture in the air, condenses and then freezes to form more ice.

We remember well that the droplets are floating away from each other. So, as the ice starts to form, the cloud does not become a block of ice but a cloud of snow flakes, all ready to fall. As they fall, they melt and drop as rain droplets, only much bigger ones than the ones in cloud. How so? The air added more ice to them from the moisture it was carrying, remember?

Most of the drops evaporate as the fall down, due to the resistance from the air, just the same resistance we feel when riding a bike on the road. The clouds contained in a cube of one kilometer for each side, weight about a few hundred tonnes, so heavier the clouds the more drops that actually fall down on it, heavier the rain.

So that is the story of rain. You may prefer to stand in the rain than to be among the clouds.

We can tweak science to create rain in places that don't traditionally receive rainfall. If you remember the relation between supercool water and disturbance needed for crystallization, we needed a lot of cold drafts because there was not much "dirt" up above. Now this is the reason why clouds pass by without raining. So what scientists propose is to introduce "dirt".

What I cannot explain well is that one kind of "dirt", when introduced, can actually trigger crystallization at a higher temperature than some other "dirt". Silver Iodide can do this at -20 deg C where as usual crystallization needs well below -40 deg C. The process of introducing Silver Iodide in clouds to create the rain formation artificially is called seeding the clouds. Silver Iodide needs to be sprinkled fairly well inside the cloud, so crystallization will be uniform. Or rather, the upward drafts must help mix silver iodide fairly well in the clouds. There are hundreds of factors that need to go right so rain can be formed from the clouds. Here is two important ones

1. If the cloud isn't precisely downwind from the target area, the rain will fall in the wrong place anyway.
2. If the seeding is done at the wrong time, or on the wrong cloud, it may cause "cratering," or large holes in the cloud that cause it to fall apart. So an errant effort can destroy the clouds that might otherwise produce rain.

[1] Its not all water. There is some ice too. But not so many that can induce crystallization. But mostly water.
[2] The reason why dirt and dust are less at higher levels is rather simple. Anything to rise to that level against gravity must have really small weight, or can be vaporised in gas form. Most dirt don't become gas, and as the threshold of weight becomes smaller, fewer kinds of dirt can qualify.
[3]Stratus, Cirrus, Cumulus are three common varieties of cloud.

I spare you from reading this rather longish article, by quoting some interesting excerpts from it:

The researchers have found: Rainfall from seeded clouds lasted longer than rain from unseeded clouds, the rainfall covered a larger area, and total precipitation was higher, sometimes even doubled. And in many cases results began just 20 minutes after the seeding.

Mr. Bruinties is now in the United Arab Emirates conducting a three-month feasibility study to determine whether conditions there are right for a cloud seeding program. Remember, not all clouds can be seeded.

Only certain clouds, early in their formation, are useful, and timing is everything.

Other seeding agents have been researched for the last 40 years, along with the importance of other conditions that help seeding to arrive at a better understanding of the process.

This resource provided the most material for the above write up. The following is another excellent very understandable discussion on everything there is to know about clouds. Recent News on Cloud seeding in Wyoming (Jan '06), and other ones in Australia, South Africa, Texas, and Israel.

Trivia: The Arctic ground squirrel hibernates at a body temperature below freezing--and yet doesn't freeze. The ground squirrel is able to do this because before hibernation it goes through a sort of internal purification that gets rid of any particle that might seed the freezing process. Liquids require such a particle (sometimes called a nucleus) in order to freeze. By purging itself the squirrel avoids becoming an ice cube, even if the temperature drops below freezing. (Link to Source Courtesy: Pradzie)

« As Light Leads us from Earth to the Sun

Warm your hands with Supercool Liquids »

Mirror Mirror ...

I found this problem in No Ordinary Genius by Christopher Sykes. It's pretty easy.

You look in a mirror, and let's say you part your hair on the right side. You look in the mirror, and your image has its hair parted on the left side, so the image is left-to-right mixed up. But it's not top-to-bottom mixed up, because the top of the head of the image is there at the top, and the feet are down at the bottom. The question is: how does the mirror know to get the left and right mixed up, but not the up and down?

--Question Posted by Richard Feynman

Check out Disoriented? to become really disoriented.

Thursday, February 16, 2006

how small are atoms?

Why are atoms so small? To begin with, they are very small indeed. Every little piece of matter handled in everyday life contains an enormous number of them. Many examples have been devised to bring this fact home to an audience, none of them more impressive than the one used by Lord Kelvin: Suppose that you could mark the molecules in a glass of water; then pour the contents of the glass into the ocean and stir the latter thoroughly so as to distribute the marked molecules uniformly throughout the seven seas; if then you took a glass of water anywhere out of the ocean, you would find in it about a hundred of your marked molecules
--Erwin Schrodinger 'What is Life?'(1944)ISBN:0521427088

Of Many Worlds in this World

Just like as in a Nest of Boxes round,
Degrees of Sizes in each Box are found:
So, in this World, may many others be
Thinner and less, and less still by degree:
Although they are not subject to our sense,
A World may be no bigger than Two-pence.
NATURE is curious, and such Works may shape,
Which our dull senses easily escape:
For Creatures, small as Atoms, may be there,
If every one a Creature's Figure bear.
If Atoms Four, a World can make, then see
What several Worlds might in an Ear-ring be:
For, Millions of those Atoms may be in
The Head of one small, little, single Pin.
And if thus small, then Ladies may well wear
A World of Worlds, as Pendents in each Ear.

-Margaret Cavendish (1623-1673)

Saturday, February 11, 2006

Warm Your Hands with Supercool Liquid

Keywords: Supercooling, Hand warmers, Crystallization.

If you hold on to the thread till the end, you might actually learn something. As a teaser: The title is sorta accurate. Read on to find out.

My friend and I went that evening to the sports store to do some ski gear shopping. As we left the store for another to do some price comparison, we entered into a chat with the guy at the counter. He said he was going to buy ski mittens instead of ski gloves. Minnesota cold meant mittens, which offer additional warmth for fingers (as they are next to each other). Mittens are also convenient for using hand warmers in them (these are heating pads inserted in the back of the gloves for additional warmth).

Hand Warmers: So our discussion turned to reusable hand warmers (see picture. the metal is at the bottom of the pouch). He showed us a small plastic pouch of liquid with a penny sized metal plate inside it. When the metal is bent, the liquid slowly starts to turn solid and white, and releases a lot of heat while solidifying.

The liquid, it turns out, is sodium acetate, which is a very specially suited liquid for use in hand warmers. The process of releasing energy it turns out is due to two other very special processes called supercooling and crystallization. These can be observed by performing experiments which you can do yourself either by buying an handwarmer pouch or even with water (you have to work extra hard for this).

Cooling and Crystallization: Supercooling is the principle that lies at the bottom of this heat release. Cooling, as we know it, is a process by which temperature of a liquid (think water) is reduced. As the temperature goes down slowly the liquid starts to turn into solid. What is really happening here is that liquid starts to go through a change in phase (from liquid to solid) as the temperature goes down.

In fact you can see that until the temperature reaches zero, the water remains water. No ice. When temperature reaches zero, the process called crystallization starts (nobody really understands how this works). Around an impurity or a surface with irregularities (even smooth surfaces have a small amount of irregularities), the water molecules find the source for some kind of a disturbance to their liquid state. At these crystallization points, water begins to crystallize (that is, becomes ice), right when temperature hits zero. Slowly as crystallization spreads, the surface of the ice thus formed becomes a natural site for further crystallization of the uncrystallized water that remains. Water placed in an ice cube box becomes ice much faster than if kept in a vessel: because the amount of surface irregularities for potential crystallization is larger in the ice box. The temperature at which the liquid crystallizes to solid is called the freezing point temperature. So that is the short primer on cooling and formation of ice for you.

Supercooling: If you cool a liquid very quickly and much below the freezing point temperature, the liquid can avoid crystallization and remain liquid. But, now it remains liquid at a temperature lower than the freezing point temperature. For this process, it is important that as the liquid is cooled it remains still and undisturbed. Even slight disturbances can provide a site for crystallization to start.

Crystallization and Heat: So when this supercooled liquid is disturbed, it immediately begins to crystallize. But then, when it crystallizes its temperature is restored to freezing point temperature. So all this energy that comes from crystallization (called latent heat) is released outside. If you must know, this kind of reaction where energy is released outside is called exothermic (exo=out, therma=heat).

Back to Hand Warmers: So this is what is happening with sodium acetate. It is naturally in the liquid form above 54 degC. On cooling, it will freeze at 54 degC. When I found this liquid pouch of sodium acetate at room temperature (25-30 degC), it is liquid at a temperature clearly below its freezing point temperature. But this pack is shaken, transported in trucks and sold in shops. How is it possible? Well, it turns out sodium acetate is special. It is very stable as a supercooled liquid. It needs heat to be supplied to disturb its condition and induce crystallization.

This is precisely the point of the metal piece inside. When the metal piece is bent, it produces a very small amount of heat; Heat that is good enough to make sodium acetate crystallize. Then sodium acetate freezes and restores itself to 54 degC. We find that it is heating up our hand because our outside body temperature is 25-30 degC.

So this is the cool story of how supercooling, crystallization, and sodium acetate come together to make our hands warmer.

Actually there is more unexpected stuff. You will have to wait until next week to find out, and this time you don't get to choose the liquid, but the metal.

Additional Notes:
[1] I never told you why the hand warmers were reusable. So what needs to be done with frozen crystallized sodium acetate is a careful process of boiling and cooling back to room temperature (remember that this is below the freezing point temperature of sodium acetate). So place this pouch in hot water and make sure every crystal is melted to liquid. Then let it cool without any disturbance. Since sodium acetate is quite stable it will supercool to room temperature nicely. Then you can reuse it by bending the metal plate again. You can do this experiment with water. However, though cooling water below zero degC (say to -2 or -3 degC) is possible, you have be sure that the container remians undisturbed throughout the experiment. And remember, water is not as stable in the supercooled state as sodium acetate.

Some >links<
How hand warmers work (scroll down), wiki on hand warmers and an experiment (.pdf file) with handwarmers. How supercooling might be useful in metal treatment and hydrogen fuel cells Understanding exothermic and endothermic reactions from pbs A demonstration of supercooling in water

[1] During the Korean war (circa 1924), Japanese soldiers mixed warming powder (a mixture of iron, water, cellulose, vermiculite, activated carbon and salt) with water to generate heat to help keep soldiers warm in the bitter cold of the wartime battlefield.
[2] Rusting of Iron produces heat, but the process is so slow that you don't notice it.

« Being on Cloud Nine

Tuesday, February 07, 2006

$100 Laptops and Newton's Dog

Massachusetts Institute of Technology has been working on a new kind a laptop: one that costs $100, works on opensource Operating System and software, run by a 500MHz processor and has a 1GB Flash RAM instead of a hard drive. It is said that the target price is likely to come down once the product goes into production. The laptops will not be available for the general public to purchase.

Kofi Annan, while unveiling the first prototype in the World Summit on the Information Society, said "It holds the promise of major advances in economic and social development. But perhaps most important is the true meaning of 'one laptop per child.'"

MIT Tech Talk covers the lap-top project (pdf file)

The project website

The World Summit Coverage on MIT press

This is old news, but something worth covering. Also in the same vein I would like you to check out: Newton and the Walking Dog by Balaji for more than one reason. It takes a non-text-bookish approach to understanding the Newton laws (what is there to know about it?). The presentation is aimed at secondary school children, but it has surprises irrespective of the "level" of the reader. It costs only Rs. 150. The author is one of the finest people I have met. He also leads the AID India team. I will post a review soon (watch this space!)