HOW COME? World's fastest feats

What animal is the fastest on Earth? asks a readerThe fastest human, so far, is Jamaican runner Usain Bolt, who ran at a top speed of nearly 28 mph during a 100-meter dash in Berlin in 2009. But if there were a Land Animal Olympics, cheetahs would break the tape long before us in the sprint-length events. In just 3 seconds, the average cheetah can accelerate from statue-still to the freeway-worthy speed of 60 mph.

For short distances (up to about 1,000 feet), a cheetah can race ahead at 71 mph. Such speeds come in handy for chasing a gazelle across the African veld, since gazelles can reach top speeds of about 50 mph. (By contrast, top lion speed is about 36 to 50 mph.)

In a land-animal sprint, the Pronghorn antelope would take second place, clocking in at a top speed of about 60 mph. But in a distance event these North American antelopes might grab first: Pronghorns are built for endurance and can gallop along at 40 mph for more than 30 minutes. While the fastest human has run a 26.2-mile marathon in about 123 minutes, a Pronghorn could finish the Boston Marathon in a mere 40.

The fastest feat in flying is awarded to the peregrine falcon. After soaring high into the sky, the falcon can take a controlled nosedive for a tasty mouse at speeds of more than 240 mph. Of course, falcons have the benefit of gravity. Fastest at flapping forward are the appropriately named swifts; needle-tailed swifts can reach speeds of 105 mph. Meanwhile, some hummingbirds can zip along at a dizzying 61 mph.

In a race involving Earth's tinier animals, a dragonfly could flit through the air at 36 mph. Australian tiger beetles may be the fastest runners; one variety was clocked at 5.6 mph, or about the speed of a human jogging. (For its tiny size, the beetle is more than 100 times faster than the average human.)

Swiftest in water is the sailfish, which can speed away from a pursuing boat at nearly 68 mph. Swordfish might be right behind, at an estimated top speed of about 60 mph.

If extinct land animals were brought back to compete, all bets would be off. Although no one knows for sure which dinosaur was the fastest runner, most scientists think it would be one of the Ornithomimosaurs.

Also known as the ostrich dinosaurs, these short-armed lizards are thought to have been cheetah-fast, running at speeds of up to 70 mph. Since most of the "bird-mimic" dinosaurs were probably plant-eaters, their top speed probably came in handiest for escaping the clutches of big meat-eaters like T. rex -- which may have run at speeds of 11 to a scary 45 mph.