The first thing I did when I got to university was measure the charge mass ratio of the electron. Well, actually, the first thing I did was to take off my top hat and start messing my room up, but the first thing I did in labs was that. I then proceeded to spend four years peering indecently closely at the components of nature, either measuring them, calculating with them, or cursing their discoverers. After that, I fear I may have got a bit blasé about minute measurements. You know you've got a problem when you consider 100 nanometres to be 'quite big, really', an additional nanosecond a day to be worth worrying about, and a 0.1 degree difference to affect your cooking.
As part of my new job at the European Synchrotron Radiation Facility, I read a fair amount of papers and hear a good deal of technical specs for the deathrays — sorry — X-ray beams. It was during the course of a presentation about how something-or-other had a 100nm resolution that I caught myself thinking 'Bit crap, isn't it?' (I did not mention this for fear of getting deathray'd). This is, I think, because in 2007 I spent several mind-numbing weeks imaging individual atoms (as a rule of thumb, atoms in solids are about 0.3 nm apart) using a very small bit of wire. So a beam as wide as 3000 of the buggers seems huge.
I'm particularly inclined to overestimate things when they are described as 'the width of a human hair' — which is, in regular 'number' format, approx 1000nm depending on hair type. While this is pretty small, there are mites that live in the hairs that are about this size — this photo shows a dog hair next to the mite that lives on it. 'If you can get a whole organism into that width, is it really that small?' I ask myself... By the way, these mites live on humans as well as dogs. They particularly enjoy burying themselves head-first into eyelash follicles and chowing down on skin secretions. Yum!
After a brief period of mental realignment, though, I realised that 100nm is still only a quarter of one wavelength of blue light, and I still think of lightwaves as being really very small. Like Einstein, I feel light is a sensible thing to measure other things by.
Speaking of Einstein, I then read an article in New Scientist which said that we now ask so much from our clocks we have to consider the effects of relativity if we want to keep them accurate. According to general relativity, the presence of large lumps of matter in space-time distorts the space, and time, around them — meaning that time runs slower, and length is shorter, in a gravitational field. So if you start two stopwatches at the same time, send one into space, and then bring them back together, the one in space will be out of step with the one that stayed on Earth. Yes, it's non-intuitive, and yes, it's slightly worrying that space and time aren't just the theatre in which stuff happens, but actually change in response to what's going on — but every experiment so far conducted shows that this is the way things are, and the maths and explanations behind it are damn beautiful.
Now that we regularly launch clocks on satellites into space, and rely on precision measurements of the time taken to receive signals from them to, eg. locate ourselves on the Earth's surface using GPS, relativity has progressed from the realms of theoretical physics to the land of engineering problems. To explain how accurate these measurements and clocks need to be, the article mentioned that every day, the skin cells on your scalp are a nanosecond older than those on your toes, due to the different in the gravitational field between your head and feet. Eep — we do experiments that require nanosecond timing! These are real differences!
I was briefly worried about a prematurely ageing scalp, until I did a bit of comforting maths and realised that over my lifetime, that will make my scalp 1 second older than my feet. Probably not worth investing in super strong moisturiser, then.
On the other hand, height does make a difference when you're cooking. A while ago I saw some footage of water boiling at 60 degrees C on a high Nepalese plateau, demonstrating unequivocally the relationship between height and boiling point to any unbelieving Sherpas. This is due to gravity again — since the pressure depends on the weight of the air above you, the lower down you are, the more air is piled up and the more squishing you get. And pressure affects state changes like boiling and melting. What I didn't realise was that this pressure difference is noticeable between the top and bottom of a ten storey building, and therefore the boiling point of water is different depending on the height of your kitchen.
Using back of the envelope calculations, a m³ cube of air weighs 1.2kg. A 10 storey building is about 30 metres high, so you get 36kg of extra weight per m² on the bottom floor. Not something I'd want to carry round with me all day, but tiny compared to the weight of all the air in the atmosphere that you normally have pushing down on you at sea level — which weighs literally tons.
This pressure difference will reduce the boiling point at the top of the building by about 0.1 degrees — small, but measurable, and presumably important to the Heston Blumenthals amongst us. In fact, it was molecular gastronomists (scientific cooks — I approve) who got me worrying about this in the first place, when I read about an investigation they had conducted to see what the point of adding salt to boiling vegetables was. They concluded that there wasn't one, since most people can't taste the difference, it doesn't help maintain the colour, and the change in the boiling point is negligible compared to the effects of your altitude (all reasons which people gave to justify why they do it like their mum did).
But as a scientist first and a cook second, I am concerned about 0.1 degree differences. This could affect an experiment! Luckily all experiments done on phase transitions (changing from solid to liquid to gas or to other exciting things) that are not conducted by schoolchildren or chefs are done in pressurised chambers. Phew.
Becoming a scientist, or just thinking scientifically, can make it really hard to keep a grip on normal, regular life in the face of nano-scale systems, filaments that dwarf galaxies, and grant applications. But given how important science is for humanity, it seems that if there's one thing that we can't afford to have, it is a sense of proportion.