I rarely use the tube

Living out here in the Tubeless sticks, I rarely use the Underground at all. If I do, I also get off at Kew rather than go on to Richmond - but that's because I can park the car at Kew!

Maybe a dozen trips since I lost my Oyster last New Year's night. The most recent trip was on Boxing Day when I had to go into London and there were no proper trains, so I had to trek all the way over to Colliers Wood.

Bethnal Green - Stairway to Heaven

I'm not sure the memorial is inverted - surely it's a representation of a cast of the stairwell (the hollow space), in which case the steps should be on the underside.

It was obviously not a literal cast (even if you could mould teak, you could only have taken a cast of the stairwell by temporarily filling it in)

I wouldn't be too worried about weathering - they used to build railway carriages out of teak, and they are generally left out in all weathers.

Metropolitan Line Extension

The new S8 train is a sunk cost as it has already been built and is in service.

The Air Ministry

The Air Ministry merged with the Admiralty and the War Office to become the MoD in 1964.

For some years I worked in a building (since demolished) opposite the London Weather Centre. Because our building was taller, their measurements, including whether it was a White Christmas, were made on our roof.

The definition of a White Christmas is broader now, and can mean snow falling anywhere in London. (Lying snow from a fall the previous day doesn't count).

Hounslow Barracks

Hounslow Barracks is also to close - announced in the same MoD report as Kneller Hall.

Crossrail

You don't need to wait until next December for direct trains from Farringdon to Abbey Wood.

Naming stations after streets

A station named after a street is very specific if the railway runs at right angles to the street, and completely non-specific if the railway runs along the line of that street. Early tube lines were independent entities rather than a network, so could use the New York model, but when adjacent stations became combined as interchanges it ceased to be a good idea. (Tottenham Court Road and Holborn are two modern examples: each works for one line but not the other).

Least-used stations

Chicken and egg - why did they have such a poor service (one a day, or even one a week........) in the first place, even when, as in most cases, there is a train service passing through? In most cases, these "least used" stations are in sparsely populated areas, or there is a nearby station on another line with a better service. It costs money, in fuel and wear and tear, for a train to call at a station, and adds to the journey time for everyone else. If no-one is using the station anyway, why stop there?

The two Paddington underground stations

H&C and Circle trains to and from Hammersmith use the original "Bishops Road" platforms alongside the main line station, from which the rest of the station can be reached by the walkway you mention. District and Circle trains to and from High St Kensington use the "Praed Street" platforms which are connected to the main concourse (known as the "Lawn", because the GWR always had to be different). The Bakerloo platforms are more-or-less underneath the Bishops Road platforms but have barrier-free interchange with the Praed Street station.

Stations with the same name

There were two Shepherds Bushes until a few years back, and going back into history there were two Tottenham Court Roads (one now renamed Goodge Street), two South Kensingtons (now combined), and two Gloucester Roads (also now combined).

Liverpool Central

Liverpool Central is the interchange between the two Merseyrail lines. It only has three platforms, all of them under ground.

Solar elevation

Everywhere gets the same amount of daylight over the year. But where the sun gets higher in the sky, you get more heat from it per unit area - that's why it never gets very warm at the Poles, even though you get 24 hours of daylight in the summer - the sun is never more than 23 degrees above the horizon.

The amount of heat per unit area goes as the sine of the sun's elevation, so varies more at low elevations - at 30 degrees you get half (not a third) of the intensity you get at 90. As for absorption by the atmosphere, depending on what value you use for the thickness of the atmosphere, geometry gives values of around ten times as much absorption when the sun is on the horizon compared to when it is overhead.