Storm in a Teacup: The Physics of Everyday Life(82)
* The newer pennies are ever so slightly thicker because they’ve been made to weigh exactly the same as the older ones (the same mass of steel takes up slightly more space than copper). That’s why vending machines have to be changed when the Mint alters the material of the coins—different metals take up a different amount of space for a given mass. Vending machines also test that the magnetic properties are correct for the coin type.
? I’m not even joking. They’re very proud of it. Little Miss Vegetarian here was excused, but I gather it’s mostly made up of giant marine mollusks and garlic.
? Molecules are formed when electrons shift around so they’re being shared between different nuclei: This sharing forces the nuclei to stay close together, forming a single molecule made up of different atoms. The only thing that holds atoms and molecules together is that positive charges attract negative charges. Sometimes, electrons shuffle around between molecules, changing which nuclei are pinned together, and the pattern made by those nuclei. We call that a chemical reaction. Chemistry is the study of this electronic dance, and the fantastic complexity it produces.
§ There’s one more twist in the tale of the bee. Researchers from Bristol University discovered in 2013 that each flower has a slight negative charge that’s neutralized as the bee arrives. They demonstrated that bees can tell a neutral flower from a negatively charged one without landing on it. They suggested that bees might avoid neutralized flowers, because it suggests that another bee got there first and took the lion’s share of the nectar. For more on this, see the papers by Clarke et al. and Corbet et al. listed in the References section at the end of the book.
? This is all that happens in an electric heater in your home. Electrons are forced through a huge resistance, and their electrical energy is converted to heat. Every other energy conversion process is inefficient, because some energy is always lost to heat, but if heat is what you want, you can have 100% efficiency . . . perfect!
# For the pedants out there, yes, there are superconductors. But cooling things down to close to absolute zero uses huge amounts of energy and produces huge amounts of heat. So it doesn’t really help if you’re after energy efficiency.
** So it gets back to where it started 50 times each second—this is what it means to say that the UK power supply runs at 50 Hz.
?? For those who like the details: There are two steps to what the adapter does. It changes the voltage from 220V to 20V or whatever the laptop needs. And then it has to cut off half of every cycle so that it only gets the current when it’s going in one direction and not when it’s going back again. After that it smooths it out a bit to make the same sort of steady current that you get from a battery.
?? This discovery caused enormous excitement. Physicists had detected a pattern in the particles that make up our universe, a pattern they call “the Standard Model” of particle physics. But the pattern could only be correct if one very specific particle existed: the Higgs boson. It took decades to find it, and it was a tremendous boost to confidence in our understanding of our world when it was proven to exist.
§§ Or possibly two numbers that are different by 18 (09-27, for example). That’s because you can take off and land either way along the runway, but obviously your heading would be different by 180 degrees.
?? The Canadian Lawrence Morley had also proposed the same idea at the same time, but his paper had been rejected by journals for being laughably silly.
## It’s often said that it’s growing at about the same rate as your fingernails.
CHAPTER 9
A Sense of Perspective
EACH OF US relies on three life-support systems: the human body, planet Earth, and our civilization. The parallels between the three systems are powerful, because they all exist in the same physical framework. Having a better understanding of all three may be the best thing that we can do to keep ourselves alive and keep our society thriving. Nothing could be both more pragmatic and more fascinating. So this final section of the book will provide some perspective, taking each of our life-support systems in turn.
Human
I’m breathing, and so are you. Our bodies need to take oxygen molecules from the air and send carbon dioxide back out. Each one of us walks around in our own personal life-support system, a body with an inside and an outside. Our insides can do all sorts of things, but only when supplied with stuff from the outside: energy, water, and the right molecular building blocks. Breathing is just one of the supply routes. It’s ingenious: Expand your ribcage, increase the volume of your lungs, and the mob of tiny jostling air molecules close to your mouth is pushed down your windpipe by the air farther away. Take a deeper breath and your chest expands even more, making space for more of the atmosphere to rush in and touch the smallest structures in your lungs. Then, as you relax the muscles around your ribcage, your ribs are pulled downward by the Earth, pushing the air molecules in your lungs closer together until they jostle each other back to rejoin the outside. Oxygen isn’t the only molecule pulled into your lungs that your body can use. As the air passes by the sensors inside the top of your nose, some of the billions of molecules bumping into the walls will happen to collide with a larger molecule attached to the wall, one they temporarily fit into like a key into a lock. The underlying cell senses the molecular click as they fit together. That’s the start of our sense of smell—a few floating molecules of the right type bumping into the right place. Inside now has some information about what’s outside.