More tea please.

How small is small?

Disclaimer: This is a bit of an opinion post. No real work here!

Throughout my Electronic Engineering degree, I was often presented with information about sub-micron and sub-nanometre structures. Initially, I thought that these things were really small. I didn’t really stop to think exactly what these sizes meant. As my degree continued, I became more at home with talking about things that are this sort of size — despite never really coming close to actually building them.

So what does this small stuff actually mean? Take a ribosome as an example. These structures are found in basically every cell on the planet. They’re approximately 20nm across. These things are responsible for piecing together every protein in living things. They take in instructions in the form of messenger RNA (mRNA) and follow them to build proteins of a given structure by connecting amino acid building blocks together. That all fits within something that’s around 20nm by 20nm by 20nm.

Let’s assume that ribosomes are actually 20nm cubes. They’re not — they’re actually a much more complex shape — see the pictures on the Wikipedia page. Let’s make this assumption because it makes it much easier to consider their volume.

It’s extremely common to find articles comparing things to the width of human hair. I guess this comparison is often made because people know what hair is like. Whether it’s a useful comparison is a different matter. Wikipedia tells us that a European’s hair is usually between 57 and 90 microns in diameter. Let’s take 60um, as it makes our numbers more pleasant. That means that it’s possible (given the right tools) to line up 3000 ribosomes across a human hair. That seems like a lot of ribosomes, doesn’t it?

How big is three thousand? What can that be compared to that makes sense? Well consider that there are one thousand millimetres in a metre (duh). Most people are comfortable with that. Now think of three metres. That’s three thousand things.

Now ribosomes don’t seem as small as they once did, do they? Maybe they do to you, who knows. They don’t to me.

The technology to manufacture our own machines of this scale doesn’t exist yet. The technology to build planar devices that have features on this scale does exist. It’s unbelievably expensive, but technically possible.

I think it’s a shame that one doesn’t really get to interact/manipulate with things that are this size from an early age. We don’t even get to interact with things that are 1000 times larger. Hopefully, my dreams will come true soon and it will become feasible for anyone to construct nanometre-scale devices for approximately no money.

Maybe this will come as part of the promised “desktop manufacturing revolution”.

Posted at 8:00 am on Tuesday 13th January 2009

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