Skip to main content

Science and truth

Image by Ben Collins from Unsplash
I was reading for review a book called The Joy of Science by Jim Al-Khalili recently and was struck by what seemed to me an odd statement. Al-Khalili said 'A physicist like me tries to uncover ultimate truths...' Let that sink in for a moment while I tell you a story.

Many years ago, a work colleague described being at a dinner party where he heard a remarkable tale. The storyteller had heard that someone was in the centre of the smallish town of Sunningdale and saw a man walking his dog. The town centre is unusual in that a railway line runs across the main road, so there's a level crossing there. The dog walker was picking up a takeaway from the tandoori restaurant right by the level crossing. He had clearly not thought this through before setting out. He couldn't take the dog into the restaurant while he collected his food. So he tied the dog's lead to the level crossing barrier and nipped inside. He was only going to be gone a minute.

What the dog walker hadn't noticed is that the barriers were in the down position because a train was about to pass by. Moments later, the train rumbled through and the barriers opened. Leaving the dog dangling from its lead high in the air, to the bewilderment of the emerging dog walker. Everyone at the dinner party thought this was hilarious. So did my colleague - even more so than the rest of them, for reasons we will explore in a moment.

If you heard that story, would you believe it was true? There's an old saying in science that the plural of anecdote is not evidence. You need something stronger than a tale or two told at a dinner party to think that something is a fact. Of course, plenty of anecdotes are true, but just because we hear a story like this is not sufficient to start accepting something. No one at the dinner table had seen this happen - the teller of the tale had heard it from someone else. There was no corroborating evidence, such as a photograph of the dangling dog. Again, this wouldn't enough in itself - it can be faked easily enough - but it would be a contribution to the balance of likelihood. And there was no way of finding out more, especially in those pre-internet days.

As it happens, my colleague knew something the others present didn't. When he was at a dinner party and the conversation was a little dull, he had a habit of throwing a fictional tale into the mix. Some months before, he had made up the story about a dog being tied to the Sunningdale railway barrier. This story had spread from person to person - and now he was hearing it back from someone who hadn't been present when he told it, as if it were fact. His fiction had taken on a life of its own.

When we were thinking about what we need to make it likely that the story was true, we were, in a loose way, indulging in the scientific method. If this had really happened it would have been true. A truth. And assuming we weren't there, whether or not we accepted that truth would depend on the quality of evidence supporting the assertion.

So isn't this exactly what Jim Al-Khalili was saying? Why do I consider it odd? This is because science works at two levels, something highlighted in a cruel but amusing fashion by the great physicist Ernest Rutherford, who is said to have remarked 'All science is either physics or stamp collecting.' This is clearly intended as a humorous jibe against sciences other than physics - and like most people with a physics background, it makes me grin. But if we take away the subject rivalry, there is a serious underlying point. Science involves two different things. One is to establish what happens. This is the stamp collecting part. It's vital. This is where we find the facts. The truth about what is observed. But arguably it's not the interesting part of science. Science only takes off when it attempts to establish how or why something happens. And there, we usually don't establish a truth, but rather develop a best theory given the present evidence that makes testable predictions and that may change in the future.

Al-Khalili gives as an example of a truth the value of the acceleration due to gravity on the Earth's surface. This is an easily established fact. Or even simpler, there is the fact that things with a positive weight fall to the Earth if we let go of them in mid-air. But the interesting science is where that value for acceleration comes from, or why things fall in the first place - and there we usually need to have a theory.

Take another example - it is an observational fact that galaxies appear to rotate faster than they should be capable of doing without flying apart. Leaving aside the possibility that there could be an error in the calculation of how fast a galaxy can rotate and remain stable (this has been suggested), it appears to be true. However, what we can't do is make the leap from this fact to saying that it's true that dark matter exists. Dark matter is a theory to explain what is happening. As it happens, there are other theories such as MOND based on modified gravity that explain the observations without resorting to the existence of dark matter. Some evidence supports dark matter better, other evidence supports modified gravity. So it is absolutely not a scientific truth that dark matter exists. The stability given the rotation speed is what happens (subject to the proviso above), but dark matter (or modified gravity) is an explanation of why it happens - this is the really interesting science, but it's not an absolute truth.

Note that this does not mean that we can treat all theories equally. Just as is the case with the dog at the level crossing, we need to examine the evidence. If we aren't able to do that personally, it makes sense to rely on experts to examine that evidence for us (just as it's better to have an expert undertake brain surgery on you, or to fly a plane). And in many cases (unlike dark matter), there is a widely supported theory that is the best we have, unless and until new evidence comes up. Human-created climate change is a good example of this. Although it's fine to continue to look for new evidence which may reinforce or disprove it, the only sensible course is to go with the current theory that is most widely supported by subject experts.

Science, then, is not about uncovering ultimate truths, but concerns something more subtle. And, I would suggest, is all the better for it.

See all of Brian's online articles or subscribe to a weekly digest for free here


Popular posts from this blog

Is 5x3 the same as 3x5?

The Internet has gone mildly bonkers over a child in America who was marked down in a test because when asked to work out 5x3 by repeated addition he/she used 5+5+5 instead of 3+3+3+3+3. Those who support the teacher say that 5x3 means 'five lots of 3' where the complainants say that 'times' is commutative (reversible) so the distinction is meaningless as 5x3 and 3x5 are indistinguishable. It's certainly true that not all mathematical operations are commutative. I think we are all comfortable that 5-3 is not the same as 3-5.  However. This not true of multiplication (of numbers). And so if there is to be any distinction, it has to be in the use of English to interpret the 'x' sign. Unfortunately, even here there is no logical way of coming up with a definitive answer. I suspect most primary school teachers would expands 'times' as 'lots of' as mentioned above. So we get 5 x 3 as '5 lots of 3'. Unfortunately that only wor

Why I hate opera

If I'm honest, the title of this post is an exaggeration to make a point. I don't really hate opera. There are a couple of operas - notably Monteverdi's Incoranazione di Poppea and Purcell's Dido & Aeneas - that I quite like. But what I do find truly sickening is the reverence with which opera is treated, as if it were some particularly great art form. Nowhere was this more obvious than in ITV's recent gut-wrenchingly awful series Pop Star to Opera Star , where the likes of Alan Tichmarsh treated the real opera singers as if they were fragile pieces on Antiques Roadshow, and the music as if it were a gift of the gods. In my opinion - and I know not everyone agrees - opera is: Mediocre music Melodramatic plots Amateurishly hammy acting A forced and unpleasant singing style Ridiculously over-supported by public funds I won't even bother to go into any detail on the plots and the acting - this is just self-evident. But the other aspects need some ex

Which idiot came up with percentage-based gradient signs

Rant warning: the contents of this post could sound like something produced by UKIP. I wish to make it clear that I do not in any way support or endorse that political party. In fact it gives me the creeps. Once upon a time, the signs for a steep hill on British roads displayed the gradient in a simple, easy-to-understand form. If the hill went up, say, one yard for every three yards forward it said '1 in 3'. Then some bureaucrat came along and decided that it would be a good idea to state the slope as a percentage. So now the sign for (say) a 1 in 10 slope says 10% (I think). That 'I think' is because the percentage-based slope is so unnatural. There are two ways we conventionally measure slopes. Either on X/Y coordiates (as in 1 in 4) or using degrees - say at a 15° angle. We don't measure them in percentages. It's easy to visualize a 1 in 3 slope, or a 30 degree angle. Much less obvious what a 33.333 recurring percent slope is. And what's a 100% slope