The first officer saw a bright object ahead of the plane -- the planet Venus -- and mistook it for the approaching C-17.

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And the infinite emptiness of the brilliant sky above means that on the rare occasions when an object, such as a plane or a hot-air balloon, does pass through, the bright contrast lends it such a fierce intensity that it confuses the eye.

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Mach is a measure of the ratio of the velocity of an object, in this case a plane, to the velocity of sound, which equals Mach 1, or 761.2 miles per hour.

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But the first officer, still believing that the object in the sky above him was the cargo plane, initiated a dive to avoid the perceived imminent collision -- sending the jetliner toward the Air Force plane.

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It works by scanning a laser beam across an object and manipulating the reflected light to produce an extremely narrow focal plane.

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