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Atoms Old and New, 2: From Newton to Einstein

Part 1 of this series, “Atoms Old and New: Atoms in Antiquity” can be read here.

The transition to modern thinking

“It seems probable to me, that God in the beginning formed matter in solid, massy, hard, impenetrable, movable particles… even so very hard, as never to wear or break in pieces; no ordinary power being able to divide what God Himself made one in the first creation.” So wrote Sir Isaac Newton in his 1704 work, Opticks. Apart from the reference to God, there is nothing here that Democritus would have disagreed with. There is, however, very little that the present-day scientist would fully accept. In this and later posts, I discuss how atoms reemerged as fundamental particles, only to be exposed, in their turn, as less than fundamental.

The scientific revolution and the revival of corpuscular theory – 1543–1687

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Eight basic laws of physics, and one that isn’t

Reposted from 3 Quarks Daily:

GodfreyKneller-IsaacNewton-1689

Isaac Newton, 1689

Michael Gove (remember him?), when England’s Secretary of State for Education, told teachers

“What [students] need is a rooting in the basic scientific principles, Newton’s Laws of thermodynamics and Boyle’s law.”

Never have I seen so many major errors expressed in so few words. But the wise learn from everyone, [1] so let us see what we can learn here from Gove.

From the top: Newton’s laws. Gove most probably meant Newton’s Laws of Motion, but he may also have been thinking of Newton’s Law (note singular) of Gravity. It was by combining all four of these that Newton explained the hitherto mysterious phenomena of lunar and planetary motion, and related these to the motion of falling bodies on Earth; an intellectual achievement not equalled until Einstein’s General Theory of Relativity. Read the rest of this entry

Boyle’s Law is not a principle; so does the UK Education Secretary know what a principle is?

What [students] need is a rooting in the basic scientific principles, Newton’s laws of thermodynamics and Boyle’s law. [Education Secretary Michael Gove, reported here].

He has been justly mocked for confusing Newton’s laws with the laws of thermodynamics (e.g. here and here and, by me, here). But the kind of ignorance involved in describing Boyle’s Law as a “basic scientific principle” is far more damaging.

Disclosure: I taught Boyle’s Law for over 40 years, and it gets three index entries in my book, From Stars to Stalagmites.

Bottom line: Boyle’s Law is not basic. It is a secondary consequence of the kinetic theory of gases, which is basic. The difference is enormous, and matters. Anyone who thinks that Boyle’s Law is a principle doesn’t know what a principle is. (So Gove doesn’t know what a principle is? That figures.)

Reasoning: Boyle’s Law states that if you double the pressure on a sample of gas, you will halve the volume. Boyle thought this was because the molecules of gas repel each other, so it takes more pressure to push them closer together, and Newton put this idea on a mathematical footing, by suggesting an inverse square law for repulsion, rather like his inverse square law for gravitational attraction. They were wrong.

Mathematically, the Law is simply stated, which may be why Mr Gove thinks it is basic: volume is inversely proportional to pressure, which gives you a nice simple equation (P x V = a constant) that even a Cabinet Minister can understand. But on its own, it is of no educational value whatsoever. It only acquires value if you put it in its context, but this involves a concept of education that seems to be beyond his understanding.

Now to what is basic. Boyle’s Law is now explained using the kinetic theory of gases. This describes a gas as a whole lot of molecules, of such small volume compared to their container that we can think of them as points, each wandering around doing their own thing, and, from time to time, bouncing off the walls. It is the impact of these bounces that gives rise to pressure. If you push the same number of molecules (at the same temperature) into half the volume, each area of wall will get twice as many bounces per second, and so will experience twice the pressure. Pressure x volume remains constant.

Actually, Boyle’s Law isn’t even true. Simple kinetic theory neglects the fact that gas molecules attract each other a little, making the pressure less than what the theory tells you it ought to be. And if we compress the gas into a very small volume, we can no longer ignore the volume taken up by the actual molecules themselves.

So what does teaching Boyle’s Law achieve? Firstly, a bit of elementary algebra that gives clear answers, and that can be used to bully students if, as so often happens, they meet it in science before they have been adequately prepared in their maths classes. This, I suspect, is the aspect that Gove finds particularly appealing. Secondly, some rather nice experiments involving balancing weights on top of sealed-off syringes. Thirdly, insight into how to use a mathematical model and, at a more advanced level, how to allow for the fact that real gases do not exactly meet its assumptions. Fourthly, a good example of how the practice of science depends on the technology of the society that produces it. In this case, seventeenth century improvements in glassmaking made it possible to construct tubes of uniform cross-section, which were needed to measure volumes of gas accurately. Fifthly … but that’s enough to be going on with. Further elaboration would, ironically, lead us on to introductory thermodynamics. Ironically, given the interview that started this discussion.

Educationally, context is everything, the key to understanding and to making that understanding worthwhile. A person who decries the study of context is unfit for involvement with education.

Even at Cabinet level.

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