In 1903, they conquered both gravity and the critics by becoming the first humans to fly a motorized vehicle.

The mere challenge of the heavens was more than enough incentive for the industrious Ohio brothers, who were natural tinkerers and inventors. Wilbur, born in 1867, and Orville, born in 1871, were the sons of a minister who had a keen interest in science and a mother who had a passion for things mechanical. The two boys eagerly followed their breeding and their instincts.

Although not college educated, their aptitude in science and mechanics quickly brought them success. In the 1880s, they built their own hand press and established a printing house. In the 1890s, they opened their own bicycle shop, selling bikes of their own design.

But the Wrights became fascinated by the concept of flight. Not dissuaded by (and perhaps motivated by) the failure of others to master the skies, the brothers began exploring concepts in aerodynamics, testing their early notions with kites and gliders. Around 1900 in North Carolina, they built what is believed to be the first wind tunnel and tested theories based on critical assessment of the work of other engineers, the most prominent of which were French.

Having assessed their gliding techniques, the Wrights began building a gasoline engine featuring a new design for a propeller. They believed they had the vehicle they needed to achieve flight.

On Dec. 17, 1903, the Wrights tested their flyer before five witnesses at Kitty Hawk, N.C. Orville flew the vehicle 120 feet in 12 seconds -- a modest excursion but enough to qualify as the first true motorized flight by man.

Doubters sprung up immediately. In particular, the French, who had been able to achieve flight for only a few seconds, questioned the legitimacy of the Wrights' achievement. Their subsequent failure to match the brothers' success fueled their demand for proof: It took the French four years to equal the duration of Orville's 12-second flight.

For years, the Wrights refused to fly their vehicle after the 1903 flight, raising even more skepticism. But in 1908, when a French pilot was able to fly for 20 minutes, the brothers -- perhaps moved by the new challenge before them -- signed a contract with the U.S. Army and began to exhibit their flying prowess. Wilbur bettered the French by engaging in a two-hour flight that reached an altitude of 360 feet. The French aviators graciously acknowledged the superiority of the Wright brothers -- then promptly mimicked their designs. As did the rest of the world.

By 1910, the Wrights' designs became the standard for flying, and fragile but working airplanes soon dotted the skies.

Just 10 years after those shaky flights in France, flying machines were employed as a staple weapon of World War I. The world of flight had grown up quickly.