Getting perspective

On the train the other day, I got asked a question by a mature lady about things in the sky. She wanted to know what the white things were. Although my first thought was clouds, I quickly realised that she was referring to the contrails that could be seen criss-crossing the sky. This was a surprise to me as I assumed pretty much everybody new what a contrail was.

Nevertheless, I explained to her that they were caused by the heat from jet engines. She didn't buy it as she claimed never to have seen them when on a plane. Contrails tend to become visible some way behind the engine so she is probably right about not seeing the trails from the plane you are on. You can still see trails from other planes though. As further evidence for a non-aviation cause, she pointed out that they went down to the ground. It took me a second or to to realise that she was having a problem with perspective; the contrails going into the distance look as though they are getting closer to the ground. The plane and ground are still the same distance apart, just further away. This comment reminded me of a line in the classic sit-com Father Ted:

"Now concentrate this time, Dougal. These (pointing to plastic cows on table) are very small. Those (pointing out of the window) are far away".

Anyway, I was quickly able to demonstrate that the mysterious white lines were, in fact, due to jet engines. I simply pointed out a trail forming behind a plane visible from the other side of the train. Suggesting a theory and supporting it with observational evidence. Now that is science in action!

Posted in astro blog by Stuart on Sunday 15th May 2005 (00:19 UTC) | Permalink
[an error occurred while processing this directive]
[an error occurred while processing this directive]