British experiments that changed the world

During British Science Week, take a look back at investigations that shaped science, providing the fundamental knowledge we rely on today

1. Cavendish weighs the world

(Image credit: Ed Crooks)

Not only did the solitary and eccentric Henry Cavendish discover hydrogen, but he also successfully measured the weight of the world. His ambitious experiment used a special piece of equipment called a torsion balance, and in 1798 he reported his results. By measuring the gravitational attraction between two different sized lead spheres, he calculated the Earth’s density.

The apparatus consisted of an 1.8-metre wooden rod that had a 0.73-kilogram lead sphere
attached to each end, suspended from a wire. A separate system of two larger 159-kilogram lead balls were placed close to the smaller balls. This exerted enough gravitational force so that when the weights were tugged slightly the rod twists (a telescope was used to observe this). Cavendish performed his experiments in a dark and wind-proof to prevent any external air currents and temperature differences affecting his results. 

He was able to calculate the Earth’s density by using the ratios of the forces between the spheres and the gravitational attraction of the Earth to the spheres. Incredibly, his results were very accurate, and his great experiment meant we could also calculate the mass of the Sun and the Moon and even other planets in our Solar System.

2. Fleming's accidental discovery of penicillin

(Image credit: Isizawa)

In 1928, at St Mary’s Hospital in London, Alexander Fleming was busy investigating the bacterium, Staphylococcus aureus. The bacteria had been wreaking havoc, causing fatal infections, and there was no medicine at the time to treat them.

On one occasion, Fleming forgot to put one of his Petri dishes into an incubator. While he was away on a two-week holiday the bacteria multiplied, and on his return he noticed something unusual in the rogue Petri dish. There was an area where the bacteria could not grow, and instead left a ‘mould juice’ to form a clear zone around itself. He investigated and found that the mould Penicillium notatum had contaminated the dish, inhibiting the growth of the bacteria. 

In the late 1930s, scientists Howard Florey and Ernst Boris Chain had managed to isolate and purify penicillin, and the antibiotic was available as an injection by 1941. It is estimated that this discovery has saved up to 200 million lives to date.

3. Rutherford strikes gold

(Image credit: Ed Crooks)

It was previously believed that the structure of the atom was a sphere of positive charge housing smaller negatively charged electrons within it, like plums within a pudding. To test the accuracy of this ‘plum pudding’ model — under the direction of Ernest Rutherford — Hans Geiger and Ernest Marsden performed a series of experiments between 1908–1913 to prove Rutherford’s theory of an atomic model, which resembled planets orbiting the Sun.

The physicists used a radioactive substance to bombard a thin piece of gold foil with positively charged alpha particles. The majority of particles passed through the foil without any deflection, suggesting that atoms had a great deal of open space. However, some were deflected off the gold foil at different angles, which meant that those particular particles had hit something with the same charge. This meant that rather than a positive charge engulfing electrons, a smaller positive charge was held in the dense middle, thus heralding the discovery of the atomic nucleus.

4. Lind cures sailors' scurvy

(Image credit: Clker Vector Images)

Bleeding gums, your teeth dropping out, weak limbs, swollen legs and nasty patches of blood under your skin – a pirate’s life probably wouldn’t have been ideal for most of us. Scurvy was one of the diseases that plagued pirates and sailors in the early days of seafaring.

We know today that the disease is caused by a serious lack of vitamin C, something we need to form collagen, a vital component in structural and supportive connective tissue. Without enough collagen, the blood vessels and bones of those with scurvy break down until they suffer a slow and painful death. But in the time of Scottish physician James Lind, there was no knowledge about these tiny nutrients. People thought that scurvy might be contagious or caused by madness. In 1747, Lind started one of the world’s first clinical trials.

He suspected that acids could help stop the putrefaction of the body, and he devised a trial to test different ways of introducing certain acids into people’s diets. He divided a group of 12 scurvy-ridden sailors into six groups of two, all of which were to eat the same diet as one another but with the addition of an acidic supplement. Each group was treated with either a quart of cider, 25 drops of elixir of vitriol, two spoonfuls of vinegar, half a pint of seawater, two oranges and one lemon, or a spice paste, every day. After six days most of the sailors eating the fruit had made an almost complete recovery. While Lind was on the wrong track about the cause of the disease, he had found the cure.

This article was originally published in How It Works issue 112

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