Grist to the Mill

27 January, 2006

WORDS

This is a great crop of words. They just sound so spacey. First came across them in A Level Geography but had forgotten them until recently.

Troposphere: the most dense part of the atmosphere; it contains 75% of all the atmosphere’s gases along with vast quantities of water and dust. The temperature is warmest at ground level but drops to –60 C higher up. All weather is in this region. It is thickest at the equator and thins out towards the poles, varying from 5 – 9 miles high. Also known as ‘the lower atmosphere’.

Tropopause: separates the troposphere from the next layer.

Stratosphere: its outer reaches extend 31 miles above the earth. It contains little water vapour and is less dense. It is calm in this layer and the movement of gases is slow. The greater the height in this layer, the greater temperature – which increases again to a maximum of about 5 C because of the absorption of uv radiation. The stratosphere contains the ozone layer.

Stratopause: where the stratosphere meets the next layer.

Mesosphere: its upper boundary is 50 miles above the ground. The gases here are too thin to absorb much heat, although the air is still thick enough to slow down meteorites. The temperature at the furthest extent of the mesosphere drops to –120 C. The mesosphere and stratosphere constitute the middle atmosphere.

Mesopause: the arbitrary division between the mesosphere and the next layer.

Thermosphere
: extends to 372 miles. Temperatures increase with altitude and can reach 1,727 C. Chemical reactions are much faster here than on the surface of the earth. This layer is the upper atmosphere.

Ionosphere: part of the thermosphere. It is made of electrically charged (ionised) gas particles, which get their charge from UV rays. The ionosphere bounces radio signals transmitted from earth.

Exosphere
: the outermost layer of the atmosphere which drifts off into space some 430–500 miles above the ground. Hydrogen and helium are the prime components but are present at extremely low densities.

All well and good, but I like the sound of the words more than the technical information. It’s just about possible to envisage a context in which to use them, too. Such as when the moon is full and also at (in? how does it collocate?) its perigee. Which would thereby allow you to point out the magnifying effects of the troposphere on the full and enormous moon, when the line of vision cuts through at an oblique angle. As happened last June.

Also, what about these maths terms:

A deviant frustum
A curve of pursuit

Can’t possibly imagine when these would come in. A curve of pursuit sounds like the waxing then waning energy one might put into a relationship.

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