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On December 7, 1972, an astronaut aboard Apollo 17 snapped the first fully illuminated photograph of Earth from space. The Blue Marble Shot, as it came to be known, is one of the most widely published photos ever taken. Environmentalists used it to galvanize their burgeoning movement, and it has graced millions of T-shirts and Earth Day flags since. Though not the first portrait taken from space (that was in 1946), the Blue Marble touched us most deeply. It told the story of our world—vibrant, complex, and alone—and it showed unambiguously that ours is a planet of water, so far the only one known.

As a molecule, water is polar, meaning it holds a slight charge across its axis. Because of that quality, the particulars of which are singular in the chemical world, oceans don’t boil off at the slightest provocation, clouds form and rain falls, and ice floats rather than sinks. Water’s unique polarity also enables it to defy gravity, allowing it to climb upward into plants, and makes it an exceptional solvent as well as an acid or base, so it can facilitate biochemical reactions.

Water is both essential and irreplaceable for life as we know it, and here on the Blue Marble, the supply is limited. Turns out, the planet contains about 332.5 million cubic miles of water. To put that in perspective, if we gathered all the water on, in, and above the Earth into a ball, it would have a diameter of 860 miles—about the distance from New York to St. Louis. Barring a miraculous discovery, that’s all we have. And yet, scientists expect the global demand for water to rise roughly 50 percent by 2050.

If someone told me there was a substance that was essential, irreplaceable, and limited, I’d say to start banking the stuff, maybe even worship it. But for most of us in the developed world, that’s not the typical response. We water our lawns instead.

Why we take something so precious for granted is a question best asked of psychologists or economists. What can we do about it—now, that’s more suited to Popular Science. This issue, we dedicated all of our feature stories to that very question. And we came up with some fascinating answers in the fields of engineering, oceanography, medicine, energy, planetary science, and more. One innovation that exists right now could benefit millions of struggling people.

That said, none of us at Popular Science are naïve enough to believe that we can innovate away all our excesses. It will take significant political will and collective action to truly get ahead of any crisis. But technology buys us time. It allows us the space to gain understanding, save lives, and shape our common destiny. As inhabitants of the Blue Marble, shouldn’t we try to use it as wisely as we can?

Enjoy the issue.

Click here to read the June 2014 Issue.

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