Storm in a Teacup: The Physics of Everyday Life(88)

Overlaid on top of the power network there are other networks, also reaching up into the buildings and into our lives. Earth has its own planet-sized water cycle, linking oceans with rain and rivers and aquifers. Energy from the Sun provides the energy to evaporate water, to move it through our atmosphere, and to deposit it somewhere else. We humans build local diversions, funneling water out of the natural cycle and pumping it through our civilization before releasing it back to the world. Rain that has collected in a reservoir is held back, prevented from following gravity’s call directly into rivers and then the ocean. Shuffling electrons provide power to pumps that send water through pipes 3 feet in diameter, out from the reservoir, branching and branching as they travel out along our roads, into our buildings, and finally up to our taps. When we have used it, it travels back through drains and sewers, through pipes gradually increasing in size as they join together on their way to a water treatment plant or a river. When we turn on a tap, we see the tip of the network, a small link in a giant loop. Then the water runs away, out of our sight, back into the concealed tunnels. Gravity keeps it in check; as long as we do the initial work to lift it up, putting in the energy to push the water away from equilibrium, gravity will always take over to guide the onward flow down again. The drain is just the place where the resistance against gravity temporarily disappears.

A city is the place where these networks and others are all compressed together because in these places the humans are compressed together, relying on the networks to live. There are other networks overlaid on the familiar city scene: systems of food distribution, human transport, and trade to share resources. And these are just the ones that are visible if you know where to look.

Fire was the start of the human adventure with artificial light. Instead of relying on light waves from the Sun, we learned to make our own. Candles meant that we could see even when our side of the Earth had rotated around to face away from the Sun. A hundred and fifty years ago, a city at night was lit up by the light waves given out by burning candles, wood, coal, and oil. Today, the sky is filled by light that we can’t see, shining all day and all night. If we could see radio waves, we’d see that our planet hasn’t been dark at those wavelengths for a century. But these new waves are more than illumination. Radio waves, television broadcasts, Wi-Fi and phone signals form a tightly coordinated network of information, constantly rippling through our surroundings and ourselves. Anyone standing in the midst of our civilization with an electronic device that can listen in to precisely the right type of wave immediately has access to visual news broadcasts, shipping forecasts, reality TV shows, air traffic control, ham radio, and the voices of friends and family. The waves are streaming around us all the time, and the wonder of the modern world is that it’s so easy to listen in and to contribute. The flow of information ties our world together. Farmers can plan harvests based on what the supermarkets want this week. News of natural disasters touches the rest of the planet in real time. Planes can reroute to avoid bad weather up ahead. A trip to the shops can be postponed because the rainclouds will arrive overhead in ten minutes’ time. The system works because the waves are coordinated by humans cooperating with each other, because our species agreed on global rules for some waves and national rules for others. For most of human history, there were waves but no network. In only the past five generations, humans have constructed the wave-based information network that we now all find indispensable.

In the past, humans have been limited geographically by heat, cold, or the lack of resources. If the molecules around us have too little heat energy or too much, the molecules that make up our own bodies follow suit. If the careful balance between molecular activity and stasis in our bodies is lost, we start to suffer. But these geographical limits have been almost entirely lifted. We construct buildings, walkways, vehicles, and barriers and alter the inside of each structure so that it has the right energy level for us to be comfortable. Air-conditioning in Dubai and central heating in Alaska give us habitable bubbles where none existed before. We forget about the inconvenience of the real world, and take our protective bubbles for granted. Human habitations on other planets are still a long way off, but humans have developed some of the technologies required to make more of our own planet habitable. The principle is the same: manipulating an environment until it fits our strict conditions for survival. The supply of water, molecular building blocks, and energy must all be just right. When we have built one bubble, we build another, creeping across our planet and extending our survival networks wherever we go.

As our civilization grows, we face challenges. The larger the human population is, the more resources and space are required to support us. We have discovered that our use of the fuels that powered the Industrial Revolution and the dramatic growth of the developed world comes at a cost. At the same time as humans were growing plants to harvest the Sun’s energy, building a green energy reservoir that could be manipulated as required, most of our energy came from another source. Earth already had an energy reservoir formed from the torrent of solar energy, one that had collected over hundreds of millions of years, and we supped from that. Over eons, a small fraction of the plants that have trapped the Sun’s energy were themselves trapped, buried and compressed deep underground. The slow accumulation of captured solar energy built up a huge subterranean store, stashed away safely as the flow of solar energy to and from the planet continued at the surface. We call these ancient energy stores fossil fuels, and the energy is easily released and put to work. Using the energy itself isn’t a problem; it’s just stored solar energy which is finally being released back out into the universe. Knowing what to do with the packaging is a nightmare. Plants take in carbon dioxide to grow, and as the energy from their fuel is released, carbon dioxide is also re-formed and given back to the atmosphere. These individual gas molecules drift out into the air, changing how waves pass through the atmosphere. The consequence is that the planet overall becomes a slightly bigger reservoir for the Sun’s energy. After burning through the energy stores of millions of years, humans have heated the planet up slightly. Learning to deal with the new equilibrium state of our planet will take considerable ingenuity.