Science In Real Life

Home, they say, is where the heart is. So what better place to really get in touch with science? Yes, the cutting edge of science is full of expensive machinery and delicate arrangements, but there are about a gajillion (± a zillion) simple experiments you can do right in your own home to illustrate scientific principles both simple and complex. This essay marks the beginning of an occasionally appearing N-part series, where N is some large and as yet undetermined number.

Electricombly Charged

Let’s begin with your hair. Really, it does need a combing. Head on over to the bathroom and whip out your trusty plastic comb. Start a small stream of water running. Bring the comb near the water without touching it. The result should be a profound lack of change. The water is as unmoved from its downward trajectory as whatever football team it’s fashionable to insult this year. Now pass the comb through your hair – a dozen or so passes should be sufficient. This time when you approach the water, it bends towards the comb like it suddenly has a pressing appointment in your toilet bowl. The more you pull the comb through your keratinous knots, the more you are able to pull the water stream.

What’s going on? Electrostatic buildup. The friction between your hair (which actually looks fine, I promise) and the comb is violently ripping electrons away from the atoms atop your cranium, resulting in a buildup of electrons on the tooth-based hair manipulation system. That is one negatively charged comb which, being made of an excellent insulator such as plastic, gives the newly arriving electrons nowhere to go. All of this would be for naught, of course, if it weren’t for the other phenomenon at work here; and so we enter the nominal “discovery” phase of this experiment. Water, most of the time, is electrically neutral. So why the repulsion? Because of a little thing called polarization.

Each water molecule, thanks to having one electron-hungry oxygen atom and two less electron-hungy hydrogen atoms, has a slight electrical imbalance. With the water flowing sans comb, the molecules are oriented every which way, slipping and sliding this way and that on their way down. But along comes the negative charge, and now they are lined up like soldiers on parade. The molecules turn so that all the positive sides are towards the comb. Against the protests of the negative sides, the positive ends then rush as hard as they can towards the comb. Presto chango, one bent stream of water. In addition, it so happens that tap water contains minerals that conduct electricity very well. These also produce a polarization effect.

A Light Snack

Well, all of that water bending has certainly worked up an appetite. Let’s get something to eat. For this experiment, you’ll need a microwave oven, a ruler, a flat tray or plate, and a bag of marshmallows. Stand all the marshmallows on end so that they form a uniform layer on the plate one marshmallow high. Insert this arrangement into the microwave oven – being sure to first remove the rotating platform if there is one – and let it do its thing until you see several distinct melted spots in the marshmallow array. Take the plate out and get ready to do some science.

Carefully, without getting gooey gelatin on your ruler, measure the distances between each melted spot. You should observe that they are all approximately the same. Find a friend who is good at math or a calculator, and average the distances. This is our measurement. But before we use the measurement to calculate something I bet you didn’t know you could measure in your kitchen, let’s figure out why we have discrete gooey spots and not one mass of melted ‘mallow. Inside your microwave oven is a device called a magnetron, which apart from sounding like a Bond villain’s latest attempt to fry Seattle is how the device turns electricity into microwaves. How it does this is another essay altogether – for now just imagine a magical gnome pumping microwaves into the chamber like it’s his job. Microwaves, remember, are just ordinary light waves at a lower frequency than the light we can see.

So the microwaves pour into the chamber and start bouncing off the walls. Then they meet up with the microwaves that came in while they were playing rumpus room. What happens when two waves meet? Anyone? Anyone? Bueller? They interfere with each other. The parts where they oppose go to zero and the parts where they agree get amplified. Soon what you have is called a standing wave, as in the cooking chamber is packed and there is standing room only. That means that there are regions of high and low amplitude that don’t move relative to the chamber. The former are what produced the gooey spots.

Now, it so happens that the distance from one high amplitude spot to the next is what we call the wavelength. That’s what we measured before. We’re almost there; look on the back of the oven to find where the manufacturer listed the frequency of the microwaves, it will be a number followed by Hz. Multiplying wavelength by frequency means dividing distance by time, so using the measurement you took before you can calculate … yes, that’s right: the speed of light. All 300 million meters per second of it. Now quickly grab some graham crackers and chocolate and enjoy your smores of science.