As part of the Edinburgh International Science Festival in April, the National Galleries of Scotland and Hexagon Productions organised ‘Constable’s Clouds’, a series of children’s workshops exploring the science behind the weather as depicted in some of the paintings currently on display at the Scottish National Gallery.
In this blog-post, Sian Hickson from Hexagon Productions highlights some of the weather that features in some famous paintings and reveals how this influenced the workshop activities…
In this magnificent painting by John Constable, currently on view at the Scottish National Gallery as part of the Constable & McTaggart display, you can see nimbus clouds, cumulus clouds, and a beautiful rainbow.
At the ‘Constable’s Clouds’ workshops we made our own clouds using hot water and solid carbon dioxide (‘dry ice’). Carbon dioxide is one of the substances that we breathe out, and is normally a gas at room temperature. To get it to freeze and become solid, it has to be cooled under pressure to - 78°C, which is slightly colder than the coldest place on earth in Antarctica!
The clouds were made of water vapour, exactly like real clouds in the sky. The tiny droplets of water vapour, that are always in the air around us, stuck together to form bigger droplets that we can see. This happened because we made the air cold with the solid carbon dioxide.
The sun might look yellow in the sky, but the light that comes from the sun is white. It only looks yellow to us because of dust particles in the atmosphere scattering the white light of the sun. White light is made up of all the other colours of light mixed together. In this painting, by Frederic Edwin Church, you can see the white light from the sun reflecting on the waterfall. There’s also a rainbow in the bottom-right corner.
A rainbow appears when water droplets in the air cause sunlight to ‘refract’, to split into all the different colours that make it up.
At the ‘Constable’s Clouds’ workshops, the children made their own rainbows using prisms, which split white light into different colours, exactly like water droplets do in the air. The light changed speed as it moved from the air into the glass of the prism.
The children imagined the different colours as different vehicles turning a corner. Red light was a big lorry going very slowly, whilst violet was a small motorbike going very fast. So red turned the corner at a wider angle, whilst violet turned the corner at a narrower angle, which meant the different colours ended up in different places, so appear separately.
Finally, the children at the workshops learned about snow and how it forms. Snowflakes are always hexagonal, always symmetrical and all unique; they form around tiny particles of dust in the atmosphere and can clump together to form bigger flakes. The children made their own fake snow using the same material that is used to make artificial snow for films and TV!