The Story of the Atom

Possibly the earliest scientific question we as a race attempted to answer was ‘what is our world made of’. People reasoned that everything had to be made of something- all the machines and things we build have different components in them that we can identify, so it seemed natural that those materials and components were in turn made of some ‘stuff’ or other. Some reasoned that everything was made up of the most common things present in our earth; the classical ‘elements’ of earth, air, fire and water, but throughout the latter stages of the last millennia the burgeoning science of chemistry began to debunk this idea. People sought for a new theory to answer what everything consisted of, what the building blocks were, and hoped to find in this search an answer to several other questions; why chemicals that reacted together did so in fixed ratios, for example. For a solution to this problem, they returned to an idea almost as old as science itself; that everything consisted of tiny blobs of matter, invisible to the naked eye, that joined to one another in special ways. The way they joined together varied depending on the stuff they made up, hence the different properties of different materials, and the changing of these ‘joinings’ was what was responsible for chemical reactions and their behaviour. The earliest scientists who theorised the existence of these things called them corpuscles; nowadays we call them atoms.

By the turn of the twentieth century, thanks to two hundred years of chemistry using atoms to conveniently explain their observations, it was considered common knowledge among the scientific community that an atom was the basic building block of matter, and it was generally considered to be the smallest piece of matter in the universe; everything was made of atoms, and atoms were fundamental and solid. However, in 1897 JJ Thomson discovered the electron, with a small negative charge, and his evidence suggested that electrons were a constituent part of atoms. But atoms were neutrally charged, so there had to be some positive charge present to balance out; Thomson postulated that the negative electrons ‘floated’ within a sea of positive charge, in what became known as the plum pudding model. Atoms were not fundamental at all; even these components of all matter had components themselves. A later experiment by Ernest Rutherford sought to test the theory of the plum pudding model; he bombarded a thin piece of gold foil with positively charged alpha particles, and found that some were deflected at wild angles but that most passed straight through. This suggested, rather than a large uniform area of positive charge, a small area of very highly concentrated positive charge, such that when the alpha particle came close to it it was repelled violently (just like putting two like poles of a magnet together) but that most of the time it would miss this positive charge completely; most of the atom was empty space. So, he thought the atom must be like the solar system, with the negative electrons acting like planets orbiting a central, positive nucleus.

This made sense in theory, but the maths didn’t check out; it predicted the electrons to either spiral into the nucleus and for the whole of creation to smash itself to pieces, or for it all to break apart. It took Niels Bohr to suggest that the electrons might be confined to discrete orbital energy levels (roughly corresponding to distances from the nucleus) for the model of the atom to be complete; these energy levels (or ‘shells’) were later extrapolated to explain why chemical reactions occur, and the whole of chemistry can basically be boiled down to different atoms swapping electrons between energy levels in accordance with the second law of thermodynamics. Bohr’s explanation drew heavily from Max Planck’s recent explanation of quantum theory, which modelled photons of light as having discrete energy levels, and this suggested that electrons were also quantum particles; this ran contrary to people’s previous understanding of them, since they had been presumed to be solid ‘blobs’ of matter. This was but one step along the principle that defines quantum theory; nothing is actually real, everything is quantum, so don’t even try to imagine how it all works.

However, this still left the problem of the nucleus unsolved; what was this area of such great charge density packed  tightly into the centre of each atom, around which the electrons moved? What was it made of? How big was it? How was it able to account for almost all of a substance’s mass, given how little the electrons weighed?

Subsequent experiments have revealed an atomic nucleus to tiny almost beyond imagining; if your hand were the size of the earth, an atom would be roughly one millimetre in diameter, but if an atom were the size of St. Paul’s Cathedral then its nucleus would be the size of a full stop. Imagining the sheer tinyness of such a thing defies human comprehension. However, this tells us nothing about the nucleus’ structure; it took Ernest Rutherford (the guy who had disproved the plum pudding model) to take the first step along this road when he, in 1918, confirmed that the nucleus of a hydrogen atom comprised just one component (or ‘nucleon’ as we collectively call them today). Since this component had a positive charge, to cancel out the one negative electron of a hydrogen atom, he called it a proton, and then (entirely correctly) postulated that all the other positive charges in larger atomic nuclei were caused by more protons stuck together in the nucleus. However, having multiple positive charges all in one place would normally cause them to repel one another, so Rutherford suggested that there might be some neutrally-charged particles in there as well, acting as a kind of electromagnetic glue. He called these neutrons (since they were neutrally charged), and he has since been proved correct; neutrons and protons are of roughly the same size, collectively constitute around 99.95% of any given atom’s mass, and are found in all atomic nuclei. However, even these weren’t quite fundamental subatomic particles, and as the 20th century drew on, scientists began to delve even deeper inside the atom; and I’ll pick up that story next time.

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The Age of Reason

Science is a wonderful thing- particularly in the modern age where the more adventurous (or more willing to tempt fate, depending on your point of view) like to think that most of science is actually pretty well done and dusted. I mean, yes there are a lot of the little details we have yet to work out, but the big stuff, the major hows and whys, have been basically sorted out. We know why there are rainbows, why quantum tunnelling composite appears to defy basic logic, and even why you always seem to pick the slowest queue- science appears to have got it pretty much covered.

[I feel I must take this opportunity to point out one of my favourite stories about the world of science- at the start of the 20th century, there was a prevailing attitude among physicists that physics was going to last, as an advanced science, for about another 20 years or so. They basically presumed that they had worked almost everything out, and now all they had to do was to tie up all the loose ends. However, one particular loose end, the photoelectric effect, simply refused to budge by their classical scientific laws. The only person to come up with a solution was Max Planck who, by modelling light (which everyone knew was a wave) as a particle instead, opened the door to the modern age of quantum theory. Physics as a whole took one look at all the new questions this proposed and, as one, took a collective facepalm.]

In any case, we are now at such an advanced stage of the scientific revolution, that there appears to be nothing, in everyday life at least, that we cannot, at least in part, explain. We might not know, for example, exactly how the brain is wired up, but we still have enough of an understanding to have a pretty accurate guess as to what part of it isn’t working properly when somebody comes in with brain damage. We don’t get exactly why or how photons appear to defy the laws of logic, but we can explain enough of it to tell you why a lens focuses light onto a point. You get the idea.

Any scientist worth his salt will scoff at this- a chemist will bang on about the fact that nanotubes were only developed a decade ago and will revolutionise the world in another, a biologist will tell you about all the myriad of species we know next to nothing about, and the myriad more that we haven’t discovered yet, and a theoretical physicist will start quoting logical impossibilities and make you feel like a complete fool. But this is all, really, rather high-level science- the day-to-day stuff is all pretty much done. Right?

Well… it’s tempting to think so. But in reality all the scientists are pretty correct- Newton’s great ocean of truth remains very much a wild and unexplored place, and not just in all the nerdy places that nobody without 3 separate doctorates can understand. There are some things that everybody, from the lowliest man in the street to the cleverest scientists, can comprehend completely and not understand in the slightest.

Take, for instance, the case of Sugar the cat. Sugar was a part-Persian with a hip deformity who often got uncomfortable in cars. As such when her family moved house, they opted to leave her with a neighbour. After a couple of weeks, Sugar disappeared, before reappearing 14 months later… at her family’s new house. What makes this story even more remarkable? The fact that Silky’s owners had moved from California to Oklahoma, and that a cat with a severe hip problem had trekked 1500 miles, over 100 a month,  to a place she had never even seen. How did she manage it? Nobody has a sodding clue.

This isn’t the only story of long-distance cat return, although Sugar holds the distance record. But an ability to navigate that a lot of sat navs would be jealous of isn’t the only surprising oddity in the world of nature. Take leopards, for example. The most common, and yet hardest to find and possibly deadliest of ‘The Big Five’, everyone knows that they are born killers. Humans, by contrast, are in many respects born prey- we are slow over short distances, have no horns, claws, long teeth or other natural defences, are fairly poor at hiding and don’t even live in herds for safety in numbers. Especially vulnerable are, of course, babies and young children, who by animal standards take an enormously long time to even stand upright, let alone mature. So why exactly, in 1938, were a leopard and her cubs found with a near-blind human child who she had carried off as a baby five years ago. Even more remarkable was the superlative sense of smell the child had, being able to differentiate between different people and even objects with nothing more than a good sniff- which also reminds me of a video I saw a while ago of a blind Scottish boy who can tell what material something is made of and how far away it is (well enough to play basketball) simply by making a clicking sound with his mouth.

I’m not really sure what I’m trying to say in this post- I have a sneaking suspicion my subconscious simply wanted to give me an excuse to share some of the weirdest stories I have yet to see on Cracked.com. So, to round off, I’ll leave you with a final one. In 1984 a hole was found in a farm in Washington State, about 3 metres by 2 and around 60cm deep. 25 metres away, the three tons of grass-covered earth that had previously filled the hole was found- completely intact, in a single block. One person described it as looking like it had been cut away with ‘a gigantic cookie cutter’, but this failed to explain why all of the roots hanging off it were intact. There were no tracks or any distinguishing feature apart from a dribble of earth leading between hole and divot, and the closest thing anyone had to an explanation was to lamely point out that there had been a minor earthquake 20 miles ago a week beforehand.

When I invent a time machine, forget killing Hitler- the first thing I’m doing is going back to find out what the &*^% happened with that hole.