Read an Excerpt
How to Fossilize Your Hamster
And Other Amazing Experiments for the Armchair Scientist
By Mick O'Hare
Henry Holt and CompanyCopyright © 2008 New Scientist
All rights reserved.
In the Kitchen
Can you make plastic in your kitchen?
You would imagine that you'd need some pretty noxious, smelly chemicals to make plastic, but you can actually find the things you need to make malleable, doughy pieces of it in your own home. Instead of putting vinegar on some fish and chips and crying over your spilled milk, use them to become a polymer chemist.
WHAT DO I NEED?
* a pint of milk
* a saucepan
* a sieve or colander
* a spoon for stirring
* four teaspoons of white vinegar
* rubber gloves
WHAT DO I DO? Pour the milk into the pan and gently warm it. When the milk is simmering (don't let it boil), stir in the white vinegar until you notice whitish yellow rubbery lumps beginning to curdle in the mixture and the liquid clearing. Turn off the heat and let the pan cool.
WHAT WILL I SEE? First of all you'll smell the vinegary reaction, which is the key to the process at work. As the vinegar is added and stirred, the liquid gets clearer, and the yellowy rubbery lumps form. When the pan has cooled you can sieve the lumps from the liquid, pouring the liquid down the sink. Put on the rubber gloves and wash the lumps in water. You can then press them together into one big blob — they will be squishy and will feel as if they are going to fall apart, but they will stick together after some firm kneading. You can now use your artistic skills to fashion the material into the shapes of your choice — the New Scientist staff came up with balls, stars, a heart shape for a pendant, and even dinosaur footprints. Leave the material to dry for a day or two, and it will become hard and plastic enough to paint and varnish.
WHAT'S GOING ON? You have used the combination of an acid — in this case vinegar, which contains acetic acid — and heat to precipitate casein (a protein) from the milk. Casein is not soluble in an acid environment, and so when the vinegar is added to the warm milk, it appears in the form of globular plastic-like lumps. Casein behaves like the plastics we see in many objects around us, such as computer keyboards and phones, because it has a similar molecular form. The plastics in everyday objects are based on long-chain molecules called polymers. These are of high molecular weight and get their strength from the way their billions of interwoven crisscrossing molecules tangle together.
P.S. Some forms of cheese making rely on a similar technique — the name "casein" comes from caseus, the Latin for cheese. The Indian cheese known as paneer is made in a very similar way to the plastic you have just made, although in this case lemon juice is the acid used rather than vinegar. Afterward, unlike our plastic milk, it is not dried out and allowed to harden to tooth-breaking consistency, and so remains soft and edible.
Breakfast cereals often claim to be fortified with iron. Well, are they?
They are and, more amazingly, if you have a magnet you can extract it, too! So ponder the ingredients list on your box of cornflakes while you are munching breakfast, and then set about removing one of them.
WHAT DO I NEED?
* breakfast cereal fortified with iron (cornflakes work, but check on the side of the box to see what the iron content is — the higher, the better)
* a plastic cup
* a spoon or pestle to crush the cereal (better still, a blender)
* hot water
* a very strong magnet
* clean white paper
* a clear, sealable plastic sandwich bag
WHAT DO I DO? Fill the cup to about two-thirds full with cereal, and with the spoon or pestle crush the cereal into a fine powder. It is worth spending a lot of time on this stage — the finer the powder, the better. Put the crushed cereal into the sandwich bag and add hot water. Leave the mixture for about fifteen to twenty minutes. Now gently tilt the bag forward so that the cereal collects on one side, and place the magnet along the outside of the bag near the cereal, running it over the bottom, because the iron tends to sink. Tilt the bag back so that the cereal runs away from the magnet. You can also lay the bag flat on the table and stroke the magnet across it toward a single corner of the bag.
Alternatively, if you are using a blender, put the cereal straight into the blender and add hot water until the cereal is submerged. Wait for about fifteen to twenty minutes until the cereal is soft, then blend it all together. While the blender is whirring, place the magnet on the outside of the blender near the mixture, and keep it there as you turn the blender off.
WHAT WILL I SEE? The magnet will attract a black fuzz of iron. Move the magnet over the surface of the bag or blender and the tiny pieces of iron will follow it.
WHAT'S GOING ON? The black stuff really is iron in your cereal — the same stuff that is found in nails and trains and motorbikes. And it's quite heavy, which is why you need to make sure you run your magnet along the bottom of the bag. The iron is added to the mix when the cereals are being made, and you really do eat it when you devour your cornflakes.
The reason it is added in a form that you can extract is that iron ions (iron that would more easily combine with other molecules in the cereal) increase the spoilage rate of the food. Using iron in its pure metal form gives the cereal a longer shelf life.
The hydrochloric acid and other chemicals in your stomach dissolve some of this iron, and it is absorbed through your digestive tract, although much of it remains untouched and is excreted.
P.S. Humans need iron for many important bodily functions. Red blood cells carry hemoglobin, of which iron is a key constituent. Hemoglobin transports oxygen through the blood to the rest of the body by binding oxygen to its iron atom and carrying it through the bloodstream. As our red blood cells are being replaced constantly, iron is an essential part of our diet.
Can you maintain the fizz in champagne overnight if a teaspoon is suspended in the neck of the bottle?
I have included this experiment not because it is spectacular or even because it actually works, but to illustrate the use and importance of controlled conditions when attempting to prove or disprove a theory. For any experiment in this book, you can add a control for comparison to test whether a particular ingredient is the cause of the reaction you are observing.
WHAT DO I NEED?
* at least two bottles of champagne
* a fridge
* a teaspoon
* champagne flutes
WHAT DO I DO? Open two bottles of champagne. Drink some from each, then place a teaspoon into the neck of one of the bottles, with the handle dangling downward and with no part of the teaspoon touching the liquid. Drink a little more if it is. The other bottle should be left open. To maintain a true control, keep the amount of champagne in each bottle equal. Now place both in the fridge and leave them overnight. Test them at regular intervals, noting how fizzy each bottle is and whether there is any significant difference between the two. I suggest you test them the following morning, lunchtime, and evening, and again on subsequent days, until the champagne in both bottles has lost all its fizz.
WHAT WILL I SEE? You'll need to be objective in your assessment of the fizz quotient of each bottle, but you will find, especially if you repeat the experiment as any decent scientist would, that both bottles are equally fizzy at each stage of testing. As an objective measure you could see how much champagne needs to be added to the champagne flutes for the bubbles to reach the rim, but for this to work you'll have to make sure you pour all glasses at the same rate.
WHAT'S GOING ON? This question is a classic example of being misled by uncontrolled experiments.
Because people rarely have two bottles open at the same time, if they have stored an unfinished bottle with a suspended spoon in its neck they attribute the following day's unexpected longevity of fizz to the spoon. However, in your tasting experiments you will have found that the truth of the matter is that champagne — surprisingly — keeps its fizz for three days or more, with or without the teaspoon.
The opened bottle without the teaspoon acts as a control against which you are able to gauge the fizziness of the bottle with the teaspoon in its neck. Both bottles decrease in fizziness at exactly the same rate.
It's not uncommon to attach significance to apparently linked events when there is no control data to compare them with. Often you'll hear people saying things like, "How incredible, I was just thinking of you when the phone rang and it was you." Telepathy is not involved here. We merely ignore the huge number of times we think of people and the phone does not ring.
P.S. If your budget doesn't stretch to champagne, the experiment will work just as well with cava, Asti Spumante, or a domestic sparkling wine.
If a strand of dried spaghetti is held at both ends and bent, why does it always break into three or more pieces?
This is, indeed, a strange phenomenon. Surely holding a strand of dried spaghetti at both ends and bending it until it breaks should produce just two pieces, but it hardly ever does — usually three or even more pieces are the result. This conundrum first appeared in New Scientist in 1995 and was repeated in 1998. Even so, we didn't get to the bottom of it until 2006. It's a problem that has taxed greater minds than ours, including that of the Nobel Prize–winning physicist Richard Feynman.
WHAT DO I NEED?
* strands of dried spaghetti
* something to catch them in
WHAT DO I DO? Hold a strand of spaghetti at both ends and bend it until it breaks. Count the pieces. Repeat with the other strands.
WHAT WILL I SEE? In nearly all cases the spaghetti will break into three or more pieces. Even on the rare occasions when it seems to break into only two you'll often find a stray shard or splinter has flown off into the nether regions of your kitchen.
WHAT'S GOING ON? Back in 1998, a New Scientist reader tried to come to grips with the issues involved and came very close to solving the problem.
First, when you bend a piece of spaghetti, it does not usually break at the apex of the bend where the stresses are highest, because failure in the spaghetti is controlled by defects in the pasta. The first break occurs at a point near the apex where the combination of stress level and defect size reaches a critical value. This breaks the original piece into a long and a short piece. After the break, as the longer piece snaps back, the whipping action sends the tip beyond the neutral point (the original straight state of the piece of spaghetti) and activates the next defect on what was the long side. This defect has already been opened up on the outside of the curved spaghetti by the first bending, so it doesn't take much to finish off the crack by bending it in the other direction.
Second, the sequence of events can be determined by looking at the broken ends of the spaghetti pieces. When a break occurs, the fracture starts cleanly on the stretched convex side and ends slightly raggedly on the compressed concave side where a small splinter — or spicule — is usually torn away from one side of the break. Additionally, careful inspection of the ejected middle piece of spaghetti will reveal evidence of spicule formation at both ends and that these are on opposite sides. This shows that the two breaks that generate the middle piece occur while the spaghetti is bending in opposite directions, which is consistent with the dynamics of linear spaghetti structures.
While being very much on the right track, the reader's observations only partly answered the conundrum. It took Basile Audoly and Sébastien Neukirch to verify what was going on in their paper "Fragmentation of Rods by Cascading Cracks: Why Spaghetti Does Not Break in Half," published in Physical Review Letters (volume 95, number 9, December 22, 2004, page 95505).
Audoly and Neukirch broke strands of spaghetti of varying thicknesses and lengths by clamping one end and bending them from the other. They found that the unexpected three-part breakage occurs because of what are known as flexural waves. When the curvature of the spaghetti reaches a critical point, the first break appears. The shock of this causes a flexural wave to ripple down each of the two resulting lengths of pasta at high speed and amplitude.
The two halves formed by the initial break do not have time to relax and straighten before being hit by the flexural wave, which causes them to curve even further and suffer more breaks, leading to a cascade of cracks in the pasta. Often more than three pieces are created when this happens.
While spaghetti snapping is in itself a rather humdrum if fun pastime, Audoly and Neukirch's work also provides important information about failures in other elongated, brittle structures, including human bones and bridge spans.
P.S. In No Ordinary Genius, the illustrated biography of Richard Feynman published in 1994, Danny Hills describes his and Feynman's experiments with spaghetti: "If you get a spaghetti stick and break it, it turns out that instead of breaking in half, it will almost always break into three pieces. Why is this true — why does it break into three pieces? Well, we ended up at the end of a couple of hours with broken spaghetti all over the kitchen and no real good theory about why spaghetti breaks into three." This seems to have been a common occurrence — apparently visitors to Feynman's home were often presented with sticks of spaghetti and asked to help solve the problem.
There is, therefore, a delicious irony in the fact that while this puzzle drove Feynman, a Nobel Prize winner, in physics, to distraction, those who discovered the reason why it happened were awarded the antithesis of Nobel fame, the Ig Nobel Prize for Physics in 2006, forty-one years after Feynman won his Nobel Prize. Nobel Prizes are awarded for supreme achievements in scientists' chosen fields, while Ig Nobels, from the opposite end of the research spectrum, are awarded for success in the areas of improbable research, humor, and, quite often, silliness.
WANT TO READ MORE? A video of breaking spaghetti can be seen at http://www.lmm.jussieu.fr/spaghetti/index.html, where you can also find out more about Audoly and Neukirch's research.
No Ordinary Genius (1994) was edited by Christopher Sykes and published by W. W. Norton & Company.
What's the best way to store bananas to keep their skins from turning brown quickly?
This is counterintuitive to those of us brought up to believe that chilling foodstuffs slows decay, but a simple experiment will show us if it's true or not.
WHAT DO I NEED?
* two or more bananas (and possibly some fresh banana skins)
* a fridge (or a domestic freezer)
* lemon juice
WHAT DO I DO? Place one banana in the fridge and leave the other at room temperature (approximately 68°F). Observe each banana three or four times a day and note the relative discoloration of the skins. As a side experiment, rub a third banana with lemon juice before subjecting it to the fridge conditions.
WHAT WILL I SEE? The banana in the fridge will brown or blacken faster than the one at room temperature. However, a banana rubbed with lemon juice and placed in the fridge will not decay at the same rate as the untreated one.
WHAT'S GOING ON? While many fruits are stabilized by refrigeration, most tropical and subtropical fruits, and bananas in particular, exhibit chill injury. Tests show that the ideal temperature for long-term banana storage is 56°F. Below 50°F, spoilage is accelerated because their cells' internal membranes are damaged, releasing enzymes and other substances. Banana skin can blacken overnight as it softens and breaks down.
The membranes that keep separate the contents of the various compartments inside a cell are essentially two layers of slippery fat molecules or lipids. Chill these membranes and the molecules get more sticky, making the membranes less flexible. Bananas adjust the composition of their membranes to give the right degree of membrane fluidity for the temperature at which they normally grow. They do this by varying the amount of unsaturated fatty acids in the membrane lipids: the greater the level of unsaturated fatty acids, the more fluid the membrane at a given temperature. If you chill the fruit too much, areas of the membrane become too viscous, and it loses its ability to keep the different cellular compartments separate. Enzymes and substrates that are normally kept apart therefore mix as the membranes collapse and hasten the softening of the fruit flesh.
Excerpted from How to Fossilize Your Hamster by Mick O'Hare. Copyright © 2008 New Scientist. Excerpted by permission of Henry Holt and Company.
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