Measuring Up Size Comparisons

After such a long, serious, and scientific post on genetics and disease yesterday, I thought it was time to post a slightly less serious, shorter, but hopefully useful item on length. As a science journalist, I often need to explain the scale of nanometres, picometres, and very, very rarely yoctometers (okay never) to a non-scientific audience in my writing. Similarly, visitors to this site often ask questions relating to size and the relative scale of something like a femtometer. For more on the definitions of the prefixes you can check out this earlier article on yotta to yocto. Meanwhile, here’s a digest of some of the more common size comparisons:

One metre (1 m), that’s about the length of our dog, the height of a two-year old toddler, or roughly the length of a six-foot adult male’s arm, give or take a couple of inches.

One millimetre (1 mm) a sheet of fairly stiff, but plain, cardboard is about 1 mm. A pinhead measures up to approximately 1.7 mm.

One micrometre (1 um, the u should be a Greek letter mu) is the size at which things start to get a bit tricky. Because of the “micro”, these things are by definition microscopic: a grain of pollen, a red blood cell, are 1 micrometre across. A human hair is about 200 micrometres thick, for comparison.

One nanometre (1 nm). Now comes the really interesting bit, a nanometre is a billionth of a metre, viruses are on this scale as to are the breadth of a strand of DNA. Cell membranes too are about one nanometre thick. However, when researchers talk about nanotechnology, the scale of the objects they are discussing can stretch from this very large molecule size all the way up to several hundred nanometres…which strictly speaking is probably better thought of as a few tenths of a micrometre instead.

The Sense of Scale site has some additional comparisons, although they seriously let themselves down by talking of flourine, as opposed to fluorine atomic nuclei. Nevertheless, they do offer some interesting size comparisons, such as 260 nm being the length of the smallest transistor in a Pentium 3 chip. A Pentium 3 chip, you say? Well, presumably the site was produced when those chips were cutting edge and long before 65 nm and 45 nm processes in microelectronics had become reality. A grain of salt is about 100 micrometres, meanwhile, which given it is a near-perfect cube means it is a million cubic micrometres.

All of this relates, of course, to the orders of magnitude primer on Sciencebase some time ago, which is visualised very well in the FSU’s Powers of Ten movie. The interactive clip stretches from 100 attometres (10 to the minus 16 metres) to 10 million light years (10 to 23 metres, which is a tenth of a yottametre).

Of course, I’ve only touched on length in this post. Sometimes I need size comparisons for mass, time, density, in fact most physical properties. If you have any good indicators, leave a comment to tell us about them.

8 thoughts on “Measuring Up Size Comparisons”

  1. Interesting posts for viewers who are interested to know something about tiny measurements. Nice to walkthrough your post you have used right from pinhead to pentium 3chip as an example for your measurements.Happy to visit .I will be more happy if you have used mass comparision.

    Paul allan.

    Size 28 Clothing

  2. Mike, you’re right. Law enforcement would be the only way. Unfortunately, the European Union just caved in to pressure from UK retailers that means they can continue to use pounds and ounces instead of being legally obliged to use kilos and litres. The Arabic system is base 10, but the Babylonian system on which time is measured is base 60 is it not, and all digital (ironically) is base 2. Maybe the real solution is to move everyone to base 1, we wouldn’t have to worry about counting or anything then!

  3. The only way we will ever graduate to the metric system is to pass laws that require that all measurements in industry, consumer products, etc. be expressed only in metric terms. Only a few years would be required for everyone to become familiar with the metric system once forced to do so. It woudl also go a long way in improving communications. Our arabic mumber system is base 10. Why shouldn’t everything else be base 10? As a scientist, I will admit that I still have to convert measurements mentally. After all, when I go to buy lumber or a carpenters rule, they still come in inches and feet. These antiquated measurments based on such as the length of arms etc. need to be abandoned and everyone get on the same scale!

  4. It’s funny that you should describe it as the English method. The majority of Brits are still stuck in thinking which inches and pounds too, despite the fact that the metric system was introduced in the nineteenth century and has held sway across Europe, Canada, and elsewhere for decades. It’s probably a myth but didn’t the NASA engineers who lost that Mars probe think the Brits used metric so converted all their feet (which were actually already metres) into meters?

  5. Having grown up using inches and pounds as my measurement system, I still have to mentally convert anything in metric to the English method. You’d think I’d have gotten over that after so many years in science!

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