• Question: what was your favourite experiment

    Asked by anon-206364 to Zoe, Kai, Jose Eliel, Hannah, Hamid, Claire on 9 Mar 2019. This question was also asked by anon-206360, anon-206372.
    • Photo: Hannah Collingwood

      Hannah Collingwood answered on 9 Mar 2019:

      This experiment is rather strange and definitely outdated based on our current understanding of science, but it’s still one of the ones that I enjoyed reading about.
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      In the old days, people believed that anything that could be burnt contained something called phlogiston. When anything was burnt, the phlogiston in the material was absorbed by the air, and when the phlogiston had gone, the material couldn’t be burnt anymore. The evidence for this was that when something was burnt in a sealed container, the air could only absorb a limited amount of phlogiston, and when it couldn’t absorb any more, the reaction stopped.
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      Of course, these days we know that the process works the other way around: the material combusts with the oxygen in the air and when burning something in a sealed container, the reaction stops when the oxygen in the air runs out.
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      The experiment to disprove the phlogiston theory required metal and some scales. If the phlogiston theory were to be correct, the metal would be expected to get lighter when any phlogiston inside it was absorbed by the air. However, the scales showed that burning actually increased the mass because the oxygen in the air reacts with the metal to make an oxide.
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      This is one of my favourite experiments because of its simplicity and its importance in the journey from alchemy and chemistry. With hindsight, we wonder how the idea of phlogiston was ever considered.

    • Photo: Claire Greenwell

      Claire Greenwell answered on 11 Mar 2019:

      There’s one I think is really cool that was done in the 1940s by an astronomer called Erik Holmberg. This is before any sort of computer was available, and he managed to simulate colliding galaxies! He did it by setting up lightbulbs to represent different parts of the galaxies. He would replace each lightbulb by a detector one at a time, and measure the light power that could be detected at that point. He could use that to represent the gravitational force that would be on a mass there. The closer the detector to a bulb, the stronger light it detects – this is equivalent to a star being closer to another star and feeling more gravitational pull. After measuring this “force” at the point of each bulb, he calculated how this would cause all of the bulbs to move due to gravity, moved them all a little, then measured the light again. After a lot of repititions of this, he had a step by step simulation of how two galaxies would move together.
      It was an amazing thing to do with the technology at the time, and also shows how far we’ve come – now we can use computers to simulate many millions of parts instead of only a few.

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