When the Hindenburg airship approached its dock in Lakehurst, N.J., on May 6, 1937, the blimp that held the passenger decks aloft was filled with hydrogen. This element, the simplest -- and most abundant -- in the universe, has one proton with a single electron revolving around it. Hydrogen also weighs the least of all the elements atomically. It can pack quite a punch, creating vast amounts of energy when oxygen and an ignition source are introduced. When the Hindenburg exploded, the world witnessed the power of hydrogen.

Hindenburg disaster
AFP/Getty Images
The Hindenburg explosion on May 6, 1937, at Lakehurst,
New Jersey.

As the Hindenburg was docking that May evening, the blimp's outer skin was exposed to a static spark. In a matter of seconds, flames tore across the airship, reducing it to a ball of flames and twisted metal. Thirty-six people lost their lives in the disaster [source: National Archives]. And as fast as the Hindenburg burned, so, too, did the public's opinion of hydrogen. For many decades following the disaster, hydrogen was viewed with skepticism and even alarm. A "hydrogen fear factor" developed regarding the element [source: Edwards].

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Today, as concerns grow about a possibly dwindling global supply of oil -- and increasing emissions of pollutants from that oil -- energy researchers are reconsidering hydrogen as a source of fuel. It certainly has a tremendous amount of promise: Hydrogen emits little or no greenhouse gases (GHGs). Its major byproducts are water vapor and heat. Hydrogen has the highest energy output by weight of any fuel [source: CECA]. And it's plentiful; hydrogen can be produced by a number of sources, from natural gas to water itself.

But the question still remains: Is hydrogen fuel a safe source of energy for our cars? How can hydrogen even be used as fuel? There's a quick primer on the next page.

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