How big is your telescope?

I love the way that scientific institutions name telescopes.

It started with the “large” telescopes like the Large Binocular Telescope (LBT), an 11.4-metre telescope (made up of two 8.4-metre mirrors) in the Pinaleno Mountains of Arizona; the Very Large Telescope (VLT), an array of four 8.2-metre telescopes in the Atacama Desert in Chile; and the Large Synoptic Survey Telescope (LSST), an 8.4-metre telescope also planned for the Chilean desert.

Large Binocular Telescope

Very Large Telescope array

After the “large” telescopes came the “giant” telescopes: the Giant Magellan Telescope (GMT) is 21.4-metre telescope under construction at the Las Campanas Observatory in Chile and the Giant Segmented Mirror Telescope (GSMT) is a planned 20-30-metre telescope.

Giant Magellan Telescope

Some of the larger telescopes, like the Thirty Metre Telescope (TMT) have disappointingly simple names; it seems that after using up “giant” they went back to “large”, but with adverbs. There’s the 42-metre European Extremely Large Telescope (EELT) and my personal favourite: the 60-metre Overwhelmingly Large Telescope (OWL).

Thirty Metre Telescope

European Extremely Large Telescope

Overwhelmingly Large Telescope

Demographics and subject choice

What does your choice of A Level subjects say about you? Could I work out what sort of school you went to, based on your choice of A Levels?

The DCSF publishes figures on the uptake of A Level courses. It turns out there are some marked differences between different school types: if you’re studying Law, Sociology and Media Studies then there’s a fairly good chance you attend a State-Maintained school or an FE College.

On average, 15.1% of A Level entries are pupils at Independent Schools, but that percentage drops to 1.1% for those studying Law, 1.8% for Sociology and 2.4% for Media/Film/TV Studies.

If you’re studying “Other Modern Languages” (i.e. not French, Spanish or German, Ancient Greek or Latin), Classical Studies and Home Economics then there’s a good chance you attend an independent school.

This graph shows all subjects:

If you’re studying A Level Physics then there’s a good chance you’re at an independent school.

There’s also some interesting data about the uptake of subjects amongst the different sexes; everybody knows that there is a massive gender imbalance in A Level Physics:

But this isn’t explained by results, girls do much better than boys:

Overall there are more male A grade physicists, but this is just down to the greater uptake.

Kinetic hydropower

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Wind is moving around the world all the time, and we use that for generating electricity. But water is moving around the world all the time too – can’t we use that to generate electricity?

A wind turbine is a device that converts kinetic energy (of the wind) into electrical energy. If you solve all the right equations you find out that the power (P) of a wind turbine is the product of the density of the air travelling through it (ρ), the cross-sectional area of the blades (A) and the speed of the wind cubed (v). (This means that if you double the speed of the wind, the power produced goes up by a factor of eight; if you triple it the power goes up by a factor of 27.)

This equation applies to any situation in which we’re using a fan-type arrangement to “catch” a moving fluid and extract useful electrical energy from its kinetic energy, so it applies just as well to moving water as it does to moving air.

Kinetic hydropower is the fancy name for putting a wind turbine underwater. Although the water in a river or sea moves much slower than the wind, the fact that it is much denser (about a thousand times denser) means that it can still generate reasonable amounts of electrical power. The low rotational speed also helps to protect marine life, which isn’t the case for wind turbines and birds.

Kinetic hydropower systems are expensive and difficult to install, and have to very sturdy to withstand the larger forces that moving water imparts; but if the engineering challenges can be overcome they have significant advantages over wind turbines, particularly in respect of their intermittency – a river’s flow is far more reliable than wind’s.