Aug 20: National Physical Laboratory

Today we went on an excursion to the National Physical Laboratory (NPL). The institution's main field of study is the science of measurement: standardizing measurements, conducting measurements, and studying new ways to achieve greater accuracy and precision. It's incredible to find out what goes on behind the scenes to develop everyday technology and the measurement that is needed. The process of creating an accurate, sensible measure for something like a light-bulb is more involved than I thought!

 Here are some of the main attractions:

Welcome to Jurassic... uh, the National Physical Laboratory.

Pow.

Glasses with diffraction grating... huzzah! If you look at the light from an incandescent bulb you will see a continuous distribution of all the visible colours. If you look at a fluorescent bulb, on the other hand, you will see discrete bands of all the colours. 

Inside this little chamber is the UK's standard kilogram. I believe it's made of platinum. So cool to see!

Two more standard kilograms. Once or twice a year the three standards are removed from their storage and weighed against one another to record relative shifts in their mass due to hydrocarbon reactions at their surfaces.

 Other standards of measurement (length, time, etc) have been derived from fundamental physical phenomena (e.g. a second can be defined by microwave resonances in a specific material). No such standard exists for the kilogram, however, and we are left with only the hunk of platinum and iridium in France that is (arbitrarily) defined as 1.0kg. The actual mass (the amount of material it contains) of this standard, the Standard Kilogram, is not constant and so neither is the kilogram (silly, right?) So the kilogram itself is not a constant quantity. So the gentlemen at NPL are trying to improve things a bit: 

This is a very nearly spherically symmetric mass of silicon that is a prototype for a new standard of the kilogram. The sphere will be used to count up the number of atoms of silicon it takes to make up the current kilogram and then this number will be put to rest as the new definition of 1.0kg (which will not change... assuming the laws of physics remain constant in time). More on this here.

A  new method that NPL has developed to clean the standard kilograms with UV light, opposed to the (still current) method of wiping them with a cloth...

I don't know what this does, but it looked cool, so I took a picture of it.

This is me standing in front of the actual bullion balance used by Poynting to measure the universal gravitational constant G, and subsequently the mass of the Earth. I was so tickled to see it! And it's just chilling out in the front lobby of the NPL. I heard the story of that experiment a long time ago and it's still one of my favourites.

That's all for now!