At each stop on the walk there will be a story and an activity. Worksheets for children to use during the walk need to be downloaded and printed off at school and brought with you.
Ernest Rutherford (1871–1937)
• Stand beside the Mond building; look at the picture of the crocodile carved on the wall
This picture of a crocodile was put here to remember Ernest Rutherford, one of the scientists who worked in the Cavendish laboratory.
I wonder what the picture tells us about his character?
Rutherford could be snappy, but the crocodile is also thought of being a good father, and Rutherford looked after his students. The crocodile is also said to be unable to look round and see its tail, and Rutherford was always looking forward to the next scientific discovery.
This is what he actually looked like:
• Show the photograph of Rutherford – Resource Card M
Didn’t he have a wonderful moustache?
• Who would like to try one on? – Artefact 14
Ernest Rutherford could be very fierce and crocodile-like, but there was a way of telling what kind of mood he was in, and whether it was a good idea to go into his laboratory. When his research was going well he would stride around singing hymns!
• Go to the Whipple Museum, or back to St Bene’t’s to hear the story
Ernest was born on a farm in New Zealand around 140 years ago [just before James Clerk Maxwell died], and he died in England just before the Second World War. He was interested in science even when he was a child. He used to use some of the things lying around on the farm to do experiments. He once made a cannon out of a brass tube from a hat stand, with a marble for a cannon ball and real gunpowder as the charge. The cannon ball didn’t hit the target, but the explosion destroyed the cannon!
When he was a university student in New Zealand, Ernest’s first experiments were with magnets [just like William Gilbert] and then he got interested in electromagnetism [like James Clerk Maxwell]. Eventually he realised that he needed to share ideas with other scientists, so he left New Zealand and travelled the world – he became a professor of physics at McGill University in Canada, then at Manchester University, and finally here in Cambridge.
Throughout his life Rutherford built his own equipment for his experiments out of things he found lying around the laboratory. He could do something that most people can’t – he could look at something really complicated and see simplicity. He saw how beautiful the world was, and how everything worked together in harmony. He never forgot the experiments he did as a boy on the farm, and saw himself as a simple man. Someone said he had simple ideas, simple apparatus (or equipment), but powerful results.
Rutherford was very interested in atoms. Atoms are the building blocks of everything in the universe. They are incredibly small, and can’t even bee seen with the most powerful electron microscope.
Rutherford helped the world of science by working out what an atom looked like – which is very tricky for something so tiny!
If you made a little dot with the tip of a sharpened pencil, and that dot was just made up of carbon atoms, then there would be about four billion billion carbon atoms in it. And what is more amazing, is that most of the atom is made up of empty space!
Optional explanation for older children:
People had worked out that there were both positive and negative charges in an atom (a bit like in magnets). But they used to think that an atom looked a bit like a plum pudding – mainly positive charge, with the negative charge scattered around like the plums in the pudding.
Rutherford designed a model of an atom using the results from an experiment where alpha particles were blasted through a piece of really thin gold foil.
• Show the diagram of the atomic models – Resource Card N
Rutherford worked out that the positive charge was concentrated in the middle of the atom, and the negative charges were all moving round the edge, with empty space between. To give you an idea of size, you could say that if the nucleus of positive charge in the centre of the atom was scaled up to be the size of a small pea, then the whole atom would be around the size of the British Isles. That’s a lot of empty space!
Once he had worked out what an atom looked like, Rutherford and two of his students worked here, in this laboratory, to split an atom – using some equipment that they had designed themselves called a particle accelerator.
Rutherford saw that a huge amount of energy was released when an atom was split, but saw that it might be possible to use the energy to do something like power a light-bulb, but he thought that it would be difficult to make enough or do it cheaply enough to be useful in everyday life.
Rutherford saw the world as something beautiful, which worked in harmony. He didn’t imagine that just over ten years later his ideas would be used to an incredibly powerful weapon – the atomic bomb – which was used to bomb Japan in the Second World War.
I wonder what Rutherford would have thought of that?
Would he have enjoyed the explosion and the huge mushroom cloud?
What would he have thought of all the destruction?
One of his friends said that he was glad Rutherford didn’t live to see it!
• Show the picture of a mushroom cloud – Resource Card O
But there have been some good uses for nuclear energy and radiation! Nuclear power stations are increasingly important for providing the world’s electricity, now that oil and gas supplies are running out. Radioactivity is also used in medicine (to cure cancer, diagnose diseases and sterilize medical equipment), in agriculture (to stop food being spoiled by insects and bacteria), and in industry (in navigation beacons and satellites, in smoke detectors, and to power space vehicles). Radioisotopes have even been used to get rid of pollution from oil and sewage spills.
Optional information for older children:
Rutherford was called the Father of Nuclear Physics, and won a Nobel prize for chemistry. When he died he was buried in Westminster Abbey near Isaac Newton – the farm boy from New Zealand had travelled the world and made a huge contribution to science. This was honoured in 1997. In chemistry the elements are arranged in groups of similar types in a chart called the periodic table. The recently created element 104 was named rutherfordium.
• Show a copy of the periodic table – Artefact 15
You are going to try to make a model of an atom. Everyone should have a strip of paper. In theory, if you cut your strip of paper exactly in half 31 times, you will end up with a piece the size of an atom!
I wonder if this is really possible?
I wonder how small you can make your paper?
Each time you cut the paper in half, you need to stick one half on the result sheet, and write down the name of an object that you think is about that size, to give you an idea of scale. Then you need to cut the remaining half exactly in half, and record the results again.
Each cut needs to be parallel to the first cut.
Can you do more than 10 cuts?
• If you manage 12 cuts, you will have a piece of paper the width of a human hair.
• If you manage 14 cuts, it will be the width of a microchip.
• If you manage 19 cuts, it will be the same width as visible light waves.
• If you manage 24 cuts, the paper will be the width of a membrane, and you would need an electron microscope to see it.
• You would still have 7 more cuts to go before you got to the size of an atom!