Time on other planets

An amazing feature at Jodrell Bank was the display of clocks in the café. The clock for Venus goes backwards because it rotates the wrong way. It is also very hard to see the second hand moving because a day lasts longer than a year on Venus,

 

The second hand for Jupiter flies round because the planet spins so quickly.

 

 

 

The clock has stopped for the black hole.

 

 

These are all so very effective. But we loved the notice below for Earth because we can see the radio aerials concerned from the back window of this house. Hello, Anthorn!

Why is a radio telescope painted white?

We went to Jodrell Bank near Manchester on Saturday. It was one of my early blog posts and it has been 4 years since we went. I'd never really thought about why they had chosen to paint it white. It turns out to be because black absorbs infra-red heat radiation from the Sun most effectively. That would make the metal expand and distort the very precise shape of the parabolic mirror. They claim that the shape of the 76m dish is out by only a few millimetres in the dish.

Fantastic images of space

We found a marvellous NASA website that gives you a different picture of space every day and explains it. Looks like a good way to learn new details about the life cycle of stars. http://apod.nasa.gov/apod/astropix.html

A sundog

It has taken me years to recognise this phenomenon but Wikipedia tells me that hexagonal ice crystals in high cirrus cloud refract the light of the Sun. It produces that bright patch to the right of the Sun which has the rainbow colours, suggesting the prism effect of refraction. That bright patch is the sundog or "mock Sun". In good conditions, you get one on either side of the Sun, and sometimes a circle around the Sun.