Category:Water

There’s something about water that draws and fascinates us. No wonder: it’s the most omnipresent substance on Earth and, along with air, the primary ingredient for supporting life as we know it. For starters, ocean plankton provides more than half of our planet’s oxygen. There are approximately 332.5 million cubic miles of water on Earth—96 percent of it saline. (A cubic mile of water contains more than 1.1 trillion gallons.) Water covers more than 70 percent of Earth’s surface; 95 percent of those waters have yet to be explored.

From one million miles away our planet resembles a small blue marble; from one hundred million miles it’s a tiny, pale blue dot. “How inappropriate to call this planet Earth when it is quite clearly Ocean,” author Arthur C. Clarke once astutely commented.

That simple blue marble metaphor is a powerful reminder that ours is an aqueous planet. “Water is the sine qua non of life and seems to be all over the universe and so it’s reasonable for NASA to use a ‘follow the water’ strategy as a first cut or shorthand in our quest to locate other life in the universe,” Lynn Rothschild, an astrobiologist at the NASA Ames Research Center in Mountain View, California, told me. “While it may not be the only solvent for life, it certainly makes a great one since it is abundant, it’s liquid over a broad temperature range, it floats when solid, allowing for ice-covered lakes and moons, and it’s what we use here on Earth.”

Whether searching the universe or roaming here at home humans have always sought to be by or near water. It’s estimated that 80 percent of the world’s population lives within sixty miles of the coastline of an ocean, lake, or river. Over half a billion people owe their livelihoods directly to water, and two-thirds of the global economy is derived from activities that involve water in some form. Approximately a billion people worldwide rely primarily on water-based sources for protein. (It’s very possible that increased consumption of omega-3 oils from eating fish and shellfish played a crucial role in the evolution of the human brain. And, as we’ll discuss later in the book, the seafood market is now global in a manner that could never have been imagined even a few decades ago.) We use water for drinking, cleansing, working, recreating, and traveling. According to the U.S. Geological Survey, each person in the United States uses eighty to one hundred gallons of water every day for what we consider our “basic needs.” In 2010 the General Assembly of the United Nations declared, “Safe and clean drinking water is a human right essential to the full enjoyment of life.”

Our innate relationship to water goes far deeper than economics, food, or proximity, however. Our ancient ancestors came out of the water and evolved from swimming to crawling to walking. Human fetuses still have “gill-slit” structures in their early stages of development, and we spend our first nine months of life immersed in the “watery” environment of our mother’s womb. When we’re born, our bodies are approximately 78 percent water. As we age, that number drops to below 60 percent — but the brain continues to be made of 80 percent water. The human body as a whole is almost the same density as water, which allows us to float. In its mineral composition, the water in our cells is comparable to that found in the sea. Science writer Loren Eiseley once described human beings as “a way that water has of going about, beyond the reach of rivers.”