View From On High

I always try to get a window seat when flying so that I can watch the ground or sea seven miles below. It is easy, when doing this, to pretend that one is in a spaceship looking at the same surface 200 miles below.

But the reality is very different as I discovered from the free website http://earth.jsc.nasa.gov/, an archive of 375,000 pictures taken by space shuttle astronauts of the Earth's surface.

An increase in distance by a factor of 30 makes a stunning difference. When looking down at cities from an aircraft one can make out individual buildings, but the same cities are almost undetectable from low Earth orbit when one is using (as the astronauts were) camera lenses without magnification.

London, for example, is barely detectable amidst the huge swathes of vegetation that surround Greater London.

The site gives users a choice of low and high resolution. A low resolution picture, typically of about half a megabyte, can be downloaded in a few seconds. But a high-resolution image, which may be 50 megabytes or more, can take up to an hour to download.

It is sometimes worth doing this. I discovered when looking at London through high resolution that its most distinctive feature is not Canary Wharf Tower, as I had imagined, but the Serpentine, bisected by West Carriage Drive, its water shining in the Sun.

I toured the world through the eyes of the astronauts, and everywhere natural features were far more evident than the works of man. Lake Geneva was hugely prominent, but to locate Geneva itself I needed an atlas.

Man-made reservoirs are visible enough, but they are impossible to distinguish from natural lakes since one cannot see the dams that hold them in place.

While it is fashionable to say that man is altering the face of the planet, there is little evidence of this from space. True, from signs of agriculture one can infer the existence of an intelligent species down there, but there is nothing to suggest that this species possesses advanced technology.

Cameras further out would not even detect an intelligent species! In the early days of the space programme, when some people still believed there might be an intelligent civilisation on Mars, a spacecraft camera surveyed the Martian surface from a distance of 10,000 miles. It saw nothing artificial, and scientists concluded that this was because there was nothing artificial to see.

Carl Sagan, however, pointed out that unmagnified pictures of Earth taken from the same distance would also reveal an apparently uninhabited world. Astonishment greeted this claim, but space photographs proved he was right.

Man, in short, has become so swollen by his self-importance that he sees his works as the dominant feature of the planet. They are nothing of the kind. Earth, although only a blue dot if seen from the orbit of Jupiter, is unimaginably huge on the human scale. It takes the astronaut's pictures to make us realise that we relate in size to our world as atoms relate to us.