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.
But humans are ingenious. Our understanding of science, medicine, engineering, and our own culture is now available to be plucked from the network of invisible waves around us. Every time we use anything from that information network, we are benefiting from the effort put in by generations of other humans.
One of the greatest advances has come from discovering how much space there is to work with if you play on size scales other than our own. The human body and the structures that fit it aren’t changing size—we consist of a hugely complex system and we need this much space to contain it. The size of beds, tables, chairs, and food won’t change, because we each live in this body. But as we learn to manipulate the world of the small, and shrink our view accordingly, humans are also learning to construct enormous factories that are too small for our bodies to see. The time taken to get things done shrinks as the size shrinks, so billions of processes can be carried out in each second. Electricity flows easily on those tiny scales. A computer is just an electronic adding machine made out of nanoscale components. Computers seems small to us, but compared with the atoms they’re constructed from, they’re vast architectural marvels, with function built into their form. Astonishment at the seeming magic of a computer is really the shock of accepting that things can happen on other time and size scales. Even now, these tiny giant adding-up factories are becoming essential tools for controlling our world, and they will become more deeply integrated into our civilization as time goes on. A more crowded civilization requires more efficient decisions, faster decision-making, and a faster flow of information to coordinate the delicate cogs of the system. Using size scales other than our own makes this possible.
Our species is currently confined to this planet and its near environs, but we have looked outward at the stars for generations. Now, for the first time in the history of human civilization, we are also looking back at ourselves. Earth observation satellites and communication satellites swarm around our planet, connecting us to each other and allowing us to watch the globe roll by beneath them. From up there, the imprint of our civilization is visible: bright city lights at night, warm air around cities in cold places, the changed color of the land from agriculture. Just one of those orbiting objects is a bubble suitable for humans: the International Space Station. Our civilization does extend into space—just. A maximum of ten people at a time can represent the rest of humanity up there, orbiting the Earth once every ninety-two minutes. The men and women who have seen their planet from orbit understand that they share a perspective on our civilization that they will never completely convey to the rest of humanity. But to their enormous credit, they try.
Above the satellites, and well outside the magnetic shield that protects our planet from cosmic rays, the signs of our civilization dwindle. Out here in space, there is no up and down. A pendulum clock won’t tick because there is no gravitational pull on the pendulum. The simplicity of things here means that everything happens either exceptionally fast by human standards, or exceptionally slowly. Rapid nuclear reactions power the Sun, but the Sun changes only slowly over billions of years. Tiny atoms interact, and the outcomes are the size of a planet or a moon or a solar system. Our messy, complex civilization on our messy, complex world sits in the middle of the size and time scales.
We are an exception in the known universe.
Humans look out at space, and maybe something out there in space is looking back. Light is still our main connection to everything that isn’t our planet, and the molecular shifts caused when starlight hits our retina link us to the rest of the universe. Here we are, a beautiful, complicated, sentient layer, a thin coating on a small rocky planet, living on the boundary between the cosmos and the Earth. Here we are, a product of our three interlinked life-support systems, shaped by the physics of the universe.
Here I am, standing outside my home, looking out at the sky as the clouds gather and hide the rest of the universe from my gaze. Here I am, a modern human with a mug made from the Earth, thinking about the complexities of the universe because I can. The patterns are all around me, and I can touch them for myself. I look into my teacup and see the swirling liquid. And then I look again and see something different. Reflected from the liquid surface is a similarly bright, beautiful, and fascinating pattern, an image of the sky above my head. Right there, in my teacup, I can see the storm.