KS3 / KS4 Physics: Sir Isaac Newton and the scientific method

The great British scientists, who have transformed our thinking about the universe and our place within it, owe much of their success to one incredible idea: the scientific method.

It’s the bedrock of modern science. A way of making scientific ideas testable by comparing them to experimental results. One of its earlier practitioners was Sir Isaac Newton.

This is Newton's death mask, it's a plaster cast of his face that would've been taken moments after he died, you think of Newton as almost an abstract set of theories, you think of his universal law of gravitation. But when you look at this you see a different Newton, you see Newton the man.

Newton was obsessive, malicious, and prone to outbursts of rage, but there was something quite extraordinary about the way that he worked. In an age when people still believed in magic Newton devised a revolutionary theoretical framework with which to accurately investigate the nature of the world.

Newton was born in 1642 into an England that was a country in transition, where science, where rational thought, where reason were beginning to flower. Now, at the time one of the great questions was about the nature of light. It was known that if you take a prism and shine sunlight through it, then it splits that sunlight into all the colours of the rainbow. The question was why.

The common explanation for the appearance of the colours was that they were impurities added by the prism to the pure white light. Newton thought that the colours were already present in the white sunlight, but what set Newton apart was the fact that he devised and performed an experiment to test his hypothesis. He shone a white source of light through a prism and as expected obtained a rainbow. But then he added a twist…

Here's the genius, he introduced a slit into that rainbow beam, and that allowed him to isolate a particular colour of light and shine that into a second prism. Then, he looked for the deflection of the coloured light onto his wall. You can see that over there.

Now, look what happens when I move the red light across the slit, to the green light. On the wall what you see is green light into the prism equals green light out. Now, that implies that the colours themselves are pure, the prism is not adding or subtracting anything. That means that Newton's hypothesis was shown to be correct. The colours themselves are the basic building blocks of light and white light is made up of all those individual colours. That's genius.

Newton was one of the first to interrogate nature using the principles of what we now call the scientific method. In other words he observed the world, came up with theories to explain what he saw, then tested them with experiments to see if he was right. The power of this approach is that it aims to remove preconceived ideas and in doing so deliver a more accurate description of the natural world.

And that’s how Newton made his incredible discoveries. Most of which he wrote in this priceless book: the Principia.

It's in here that the first time that the universal law of gravitation is outlined, it's also his laws of motion that say how objects move around in the universe. It's pretty much everything you do in the first year of an undergraduate degree in physics actually.

On the face of it, it seems baffling that the scientific method took so long to emerge. After all, Newton lived just a few hundred years ago. Part of the problem is that our world is a complicated and baffling place. But it’s much easier to understand if you simplify it. It is possible to deduce the nature of light by investigating a rainbow, but by creating a controllable, repeatable experiment, Newton was able to support his hypothesis and then transfer that understanding to the much more complex world outside the laboratory.

But powerful though the method is, a crucial in its success, seems to be extraordinary individuals, people who appear to bring something extra to the process.