Storm in a Teacup: The Physics of Everyday Life(87)
Energy passes through, but the Earth itself is constantly recycled. Almost all the aluminum, carbon, and gold that make up our planet has been here for billions of years, shifting from one form to another. It might seem that after this long, these different substances should all be jumbled up, mixed together in a giant planetary soup. But the physical and chemical processes around us are continually sorting the pile, so that pockets of similar atoms group together. Gravity allows liquids to drain through porous solids, so that water soaks into the soil and joins vast underground aquifers while the soil stays where it is. When vast blooms of tiny calcium-based marine creatures live and then die at the ocean surface, it’s gravity that coaxes them downward so that they drift toward the ocean floor. The vast marine cemeteries that sometimes form as a result in shallow seas compress, shift, and become distinctive white limestone. Salt deposits are formed because water molecules will evaporate easily to become a gas when they are given more energy, but salts won’t. The lava produced at volcanic mid-ocean ridges is far more dense than water, so it stays on the ocean floor, building new crust. And life itself is constantly plucking materials from the world around it, reshaping and reorganizing them, and then leaving the detritus to be reused when it dies.
On a dark night, looking up at the sky, we see waves that have traveled across our solar system or our galaxy or our universe to reach our eyes. For millennia, light waves were our only connection to the rest of the universe, the only reason we knew that there was anything else out there. A couple of decades ago, we started to observe the thin streams of matter that reach us: neutrinos and cosmic rays. And then gravitational waves came along, only the third way that we have of touching the rest of the universe. In February 2016, it was finally confirmed that catastrophic astronomical events like the merging of black holes also send out waves, ripples in space itself. Gravitational waves have been passing through all of us our entire lives, and we’re finally about to discover what we’ve been missing out on. The light and gravitational waves whooshing past our planet weave a rich tapestry that lets us map out our universe and then add an arrow labeled: “We are here.”
But on an average day on Earth, there are more immediate considerations. Standing outside our home and watching the world go by is a reminder of the gigantic system that we’re part of. We are a small sliver of the life that keeps the system running in its current configuration. When Homo sapiens first emerged, each human only had two life-support systems: a body and a planet. But now there is a third.
This planet has been altered by many species, but only in the past few thousand years has a single species knowingly rebuilt its environment to suit itself. It is almost a single organism now, a sprawling planet-sized web of interconnections between individual consciousnesses. Each individual is almost entirely dependent on others in the system for survival, but still has its own contribution to make. An understanding of the laws of physics is one of the pillars holding up our society, and we could not manage our transport, resource management, communication, or decision-making without it. Science and technology make possible the greatest ever collective human achievement: our civilization.
Civilization
A candle and a book. Portable energy and portable information, available on demand but with the potential to last for centuries. These are the threads that stitch individual human lives together to build something much bigger: a cooperative society that is always building on the work of the previous generation. Energy must keep flowing through our civilization, so the candle can be stored almost indefinitely but can only be used once. Knowledge accumulates, so one book may stimulate many minds. There were candles and books two thousand years ago and there are still candles and books now. They are simple technologies, but they work. We have built the modern world by storing energy and sharing information about what to do with it.
We associate civilizations with cities, but they are always founded in the fields. It takes energy to build, to explore, to try and fail and try again, and so humans had to marshal the plants to harvest solar energy in order to fuel their efforts. Humans can move soil and water and seeds, but we need plants to convert light waves into sugar. We learned how to put our own green dam in place to divert a tiny part of the torrent of solar energy, and we reaped the rewards. As it trickled through Earth’s system, that temporarily diverted energy fed us, fed our animals, and gave us the capacity to alter our world.
We think of ourselves as living in a modern society, but that’s only partly true. We rely on infrastructure built by previous generations, sometimes decades ago, sometimes centuries ago, and sometimes millennia ago. Those roads and buildings and canals are still useful because they are the conduits that connect the distant and disparate parts of our society. Cooperation and trade bring enormous benefits, and these networks give each individual access to far more than their own solitary strength and intelligence could bring them.
A city is a forest of buildings, each with a different function and a different design. But underneath them all runs a huge web of thick copper cables. The copper tendrils branch as they run into individual buildings and then branch again and again, hidden in the walls and floors until the tip of one offshoot finally becomes visible at each power socket. As soon as something is plugged in, a loop is completed and electrons are free to shuffle around it, linking the outward-branching structure with the merging return structure. If you could see only the cables and not the city, you’d see the arteries of modern life, feeding us with energy from the massive power generation facilities elsewhere. The network extends across each country, a metal network of linked routes, connecting up the huge range of energy sources capable of collectively feeding the monster. We are surrounded by drifting electrons doing our bidding.