Storm in a Teacup: The Physics of Everyday Life(3)

Because of all this, I think that playing with the physical toys in the world around us is more than “just fun,” even though I’m a huge fan of fun for its own sake. Science isn’t just about collecting facts; it’s a logical process for working things out. The point of science is that everyone can look at the data and come to a reasoned conclusion. At first, those conclusions may differ, but then you go and collect more data that helps you decide between one description of the world and another, and eventually the conclusions converge. This is what separates science from other disciplines—a scientific hypothesis must make specific testable predictions. That means that if you have an idea about how you think something works, the next thing to do is to work out what the consequences of your idea would be. In particular, you have to look hard for consequences that you can check for, and especially for consequences that you can prove wrong. If your hypothesis passes every test we can think of, we cautiously agree that this is probably a good model for the way the world works. Science is always trying to prove itself wrong, because that’s the quickest route to finding out what’s actually going on.

You don’t have to be a qualified scientist to experiment with the world. Knowing some basic physical principles will set you on the right track to work a lot of things out for yourself. Sometimes, it doesn’t even have to be an organized process—the jigsaw pieces almost slot themselves into place.

One of my favorite voyages of discovery started with disappointment: I made blueberry jam and it turned out pink. Bright fuchsia pink. It happened a few years ago, when I was living in Rhode Island, sorting out the last bits and pieces before moving back to the UK. Most things were done, but there was one last project that I was adamant about fitting in before I left. I had always loved blueberries—they were slightly exotic, delicious, and beautifully and bizarrely blue. In most places I’ve lived they come in frustratingly small quantities, but in Rhode Island they grow in abundance. I wanted to convert some of the summer blueberry bounty into blue jam to take back to the UK. So I spent one of my last mornings there picking and sorting blueberries.

The most important and exciting thing about blueberry jam is surely that it is blue. I thought so, anyway. But nature had other ideas. The pan of bubbling jam was many things, but blue was not one of them. I filled the jam jars, and the jam really did taste lovely. But the lingering disappointment and confusion followed me and my pink jam back to the UK.

Six months later, I was asked by a friend to help with a historical conundrum. He was making a TV program about witches, and he said that there were records of “wise women” boiling verbena petals in water and putting the resulting liquid on people’s skin as a way of telling whether they were bewitched. He wondered whether they were measuring something systematically, even if it wasn’t what they intended. I did a bit of research and found that maybe they were.

Purple verbena flowers, along with red cabbage, blood oranges, and lots of other red and purple plants, contain chemical compounds called anthocyanins. These anthocyanins are pigments, and they give the plants their bright colors. There are a few different versions, so the color varies a bit, but they all have a similar molecular structure. That’s not all, though. The color also depends on the acidity of the liquid that the molecule is in—what’s called its “pH value.” If you make that environment a little more acidic or a little more alkaline, the molecules change shape slightly and so their color changes. They are indicators, nature’s version of litmus paper.

You can have lots of fun in the kitchen with this. You need to boil the plant to get the pigment out, so boil a bit of red cabbage in water, and then save the water (which is now purple). Mix some with vinegar, and it goes red. A solution of laundry powder (a strong alkali) makes it go yellow or green. You can generate a whole rainbow of outcomes just from what’s in your kitchen. I know: I did it. I love this discovery because these anthocyanins are everywhere, and accessible to anyone. No chemistry set required!

So maybe these wise women were using the verbena flowers to test for pH, not bewitchment. Your skin pH can vary naturally, and putting the verbena concoction on skin could produce different colors for different people. I could make cabbage water go from purple to blue when I was nice and sweaty after a long run, but it didn’t change color when I hadn’t been exercising. The wise women may have noticed that different people made the verbena pigments change in different ways, and put their own interpretation on it. We’ll never know for sure, but it seems to me to be a reasonable hypothesis.

So much for history. And then I remembered the blueberries and the jam. Blueberries are blue because they contain anthocyanins. Jam has only four ingredients: fruit, sugar, water, and lemon juice. The lemon juice helps the natural pectin from the fruit do its job of making the jam set. It does that because . . . it’s acid. My blueberry jam was pink because the boiled blueberries were acting as a saucepan-sized litmus test. It had to be pink for the jam to set properly. The excitement of working that out almost made up for the disappointment of never having made blue jam. Almost. But the discovery that there’s a whole rainbow of color to be had from just one fruit is the sort of treasure that’s worth the sacrifice.

This book is about linking the little things we see every day with the big world we live in. It’s a romp through the physical world, showing how playing with things like popcorn, coffee stains, and refrigerator magnets can shed light on Scott’s expeditions, medical tests, and solving our future energy needs. Science is not about “them,” it’s about “us,” and we can all go on this adventure in our own way. Each chapter begins with something small in the everyday world, something that we will have seen many times but may never have thought about. By the end of each chapter, we’ll see the same patterns explaining some of the most important science and technology of our time. Each mini-quest is rewarding in itself, but the real payoff comes when the pieces are put together.