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June 2, 2009 | by  | in Opinion | [ssba]




To prove a point that science is the guiding light that has and will continue to deliver us from the murky depths of human ignorance. Oh, and also to measure the wavelength of light using a fine diffraction grating.


Science and the core concepts of science—experimentation through gathering observable, empirical and measurable evidence subject to specific principles of reasoning, logic, rationality and critical thinking—are the most important ideas that humans have devised. Oh, and that light travels in waves.


Fine diffraction grating (about 300 lines/mm)
Metre rulers, 2
Lamp in holder, 12V 36W
Green filter
Power supply, low voltage, variable, able to supply 6A
One Salient Editor


You only have to look around you to see the wonders of science. From the paracetemol on the desk in front of me, the plastic it is wrapped in, to the green ink on the foil that spells out Panadol.

We know why I get headaches and need paracetemol. The simple chemical reaction of ethanol turning into acetaldehyde and then acetic acid. How that affects my liver and leads to dehydration. The special isotonic formula of Powerade. The enzyme-blocking, pain-relieving properties of paracetemol. All developed and explained logically by science and the people who devote their lives to science.

Here is a simple—YET VERY DANGEROUS—experiment that you could do at home—if you were really stupid. If you do, you are really stupid and Salient takes no responsibility for any damage you do to yourself.

Set up a 12V 36W line-filament lamp high so you can see it clearly. Place a green filter in front of the lamp.
Hold a metre ruler straight out in front of you towards the lamp, with the near end of the ruler at your face. Hold the diffraction grating against the near end of the metre ruler and look at the lamp through it.

Ask the Salient Editor to place another metre ruler at 90° to your metre ruler at its far end.

The Editor should hold a pencil vertically above their metre ruler and move it along until you see it in the green region of your bright spectrum. Note the distance, x, along the Editor’s ruler from the pencil to the far end of your ruler.

Record the observation.


I have a cellphone that transmits data at a certain wavelength and I understand how life evolved on earth and how the universe started. We can even play remote control cars on another planet.

It wasn’t so long ago that everyday life was dominated by mystical beliefs. God, pixies, Kratos, Flying Spaghetti Monster, Mr Tumnus—fictional creations used to explain things that happened: scapegoats for ignorance and misunderstanding.

Divide x by the length of your ruler. This gives you tan A, where A is the angle between the line of direct white light and the light to the green in the spectrum marked by the pencil. From tan A, use your calculator to find the angle A, and from this find sin A.

Use the formula d sin A = wavelength to calculate the wavelength of green light. You will need the value of d, spacing, i.e. distance from one ruling to the next. If the grating has 300 lines / mm then the spacing is 1 / 300,000m.


Is there anything other than science? Well yes there is, but nothing gets the same results as science. Everything from where life came from to the atomic structure of a jellybean can be explained—perhaps we haven’t found a way to explain it adequately. When Mendel wrote about inheritance he never suspected that 90 years later Rosalind Franklin would photograph the very units of genetic inheritance he could only dream about.

This is a good thing. With ignorance comes fear. When you know how something works—lightning, weather patterns, earthquakes—you’re less inclined to attribute supernatural properties to the phenomena and devise effective strategies to minimise the risk posed by them.

As shown in the experiment, things aren’t always as they seem. But there is a logical explanation. In this case that light travels in waves and that wavelengths in white light can be separated.


Science isn’t about being right. It is about having an idea and proving. It is about testing a hypothesis and then finding the most logical explanation for whatever happened. That is why the theory of evolution and the big bang theory are called theories. There is observable data to back them up and there is a logical process behind them. If another theory were to come up that explained both phenomena better I then that would critically reevaluate. A scientist will never believe that their research is the end. It isn’t.

Our microscopes will continue to examine new and different microbes, our atom-smashers will smash more atoms and our telescopes will peer further into the past than our minds can imagine. Science is not only a way of understanding the world around us but translating what we have into ever more effective systems and products.
The National government’s move to support research and development are interesting. Will they work? Possibly more so if they realise research and development needs security over decades. Also it would be nice if they gave tertiary education the funding it needs. Without well-funded tertiary education institutions there will be no graduates to staff the labs of tomorrow.

Science is cool. Try it. I’ll have the equipment for this experiment in the Salient office on the first week back from the break.


About the Author ()

The editor of this fine rag for 2009.

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