Storm in a Teacup: The Physics of Everyday Life(39)
* This behavior is called “shear-thinning” and it’s handy for snails, as we’ll see shortly.
? Of course, there is a third option: that the snail had been an egg or a juvenile hiding inside the compost. But it was pretty large, and I couldn’t imagine it growing so big in such a short time.
? There’s a genuinely funny bit in Frost’s paper when he describes what happened when they accidentally set the treadmill to a very low speed. It’s not often that I’d quote a scientific paper for comic effect, but in this case it’s absolutely justified: “After completing the filming of a particular bird, the treadmill was inadvertently turned to a very slow setting instead of completely off as intended. After a short time we noticed that the bird’s head was slowly and progressively pushed forward until it eventually toppled over. Further observations indicated that toppling, or extreme changes in posture, could also be produced by very slow forward (opposite direction to that eliciting normal walking) treadmill movements. It appeared that the extremely slow (imperceptible to us) speed of the treadmill was not sufficient to induce walking in the bird, but was sufficient to stabilize its head even though this sometimes resulted in loss of equilibrium.”
§ When I first moved to the American southwest, I couldn’t shake off a nagging curiosity about exactly where all the water came from in this dry environment. The book that answered many of my questions (and tells the fascinating story of the battles over water supply in that area) is Cadillac Desert by Marc Reisner, and I highly recommend it. California is suffering from a severe drought as I write this, and the tough decisions about how to deal with it cannot be delayed any longer.
? There is actually another solution: Start drinking cappuccino. Having a foam layer on top dampens down the oscillations a lot, so foam-covered drinks don’t slosh as easily. This is also useful in the pub. Beer snobs may not like too much of a head, but at least it stops them from spilling their drink.
# There are also two smaller pendulums that help with this, just below the main one.
CHAPTER 5
Making Waves
WHEN YOU GO to the beach, it’s almost impossible to stand for any length of time with your back to the sea. It feels wrong, both because you’re missing out on the grandeur of the sight and also because facing the other way stops you from keeping an eye on what the ocean might be up to. And it’s oddly reassuring to watch the boundary between sea and land as it constantly renews and remodels itself. When I lived in La Jolla, California, my reward after a long day was to wander down to the ocean, sit on a rock, and watch the waves as the sun went down. Just three hundred feet off shore, the waves were long and low, difficult to see. As they rolled toward the shore they’d get steeper and more obvious until they finally broke on the beach. I could sit and watch the endless supply of new waves for hours.
A wave is something that we all recognize, but waves can be hard to describe. The ones at the seashore are processions of ridges, a wiggly shape in the water surface that is traveling from over there to over here. We can measure them by looking at the distance between successive wave peaks and the height of the peaks themselves. A water wave can be as tiny as the ripples you make when you blow on your tea to cool it, or bigger than a ship.
But waves have one quite weird feature, and in La Jolla it was the pelicans that made it obvious. Brown pelicans live all along that coast, and they look so ancient that you wonder whether they’ve just flown through a wormhole from a few million years ago. They have ridiculously long beaks that usually stay folded up against their bodies, and small groups of these curious birds are often seen gliding solemnly just above the waves parallel to the coast. Once in a while, they’d plonk themselves down unceremoniously onto the ocean surface. And this was the interesting bit. The waves that the birds were sitting on rolled endlessly toward the shore, but the pelicans didn’t go anywhere.
Next time you stand on the shore and watch waves rolling toward you, watch the seabirds sitting on the surface.* They’ll be parked quite happily, passengers being carried up and down as the waves go past, but they’re not going anywhere.? What this tells you is that the water isn’t going anywhere either. The waves move, but the thing that is “waving”— the water—doesn’t. The wave can’t be static; the whole thing only works if the shape is moving. So waves are always moving. They carry energy (because it takes energy to shift the water into the wave shape and back again), but they don’t carry “stuff”. A wave is a regular moving shape that transports energy. I think this is partly why I found sitting on the beach and looking out to sea so therapeutic. I could see how energy was continually carried toward the shore by the waves, and I could see that the water itself never changed.
Waves come in many different types, but there are some basic principles that apply to them all. The sound waves made by a dolphin, the water waves made by a pebble, and the light waves from a distant star have a lot in common. And these days, we don’t just respond to the waves that nature provides for us. We also make our own, very sophisticated, contribution to the flood, and it connects the scattered elements of our civilization. But humans consciously using waves to cement cultural bonds isn’t new. This story began centuries ago, in the middle of a gigantic ocean.
A king surfing the ocean waves probably sounds like a snapshot from a particularly weird dream. But 250 years ago in Hawaii every king, queen, chief, and chiefess owned a surfboard, and royal prowess at the national sport was a considerable source of pride. Special long, narrow “Olo” boards were reserved for the elite, while the commoners used the shorter and more maneuverable “Alaia” boards. Contests were common, and provided the central drama for many Hawaiian stories and legends.? When you live on a stunning tropical island surrounded by deep blue ocean, building a culture around playing in the sea sounds perfectly sensible. But the Hawaiian surf pioneers had something else going for them: the right sort of waves. Their small island nation in the middle of a vast ocean was perfectly placed. Hawaiian geography and physics filtered the complexity of the ocean, and kings and queens surfed on the consequences.