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What Are UFOs?

What Are UFOs?

Season 52 Episode 1
53:43
Extreme Airport Engineering

Extreme Airport Engineering

Season 52 Episode 2
53:40
Dino Birds

Dino Birds

Season 52 Episode 3
53:35
Egypt's Tombs of Amun

Egypt's Tombs of Amun

Season 52 Episode 4
53:40
Pompeii's Secret Underworld

Pompeii's Secret Underworld

Season 52 Episode 5
53:40
Baltimore Bridge Collapse

Baltimore Bridge Collapse

Season 52 Episode 6
53:32
Revolutionary War Weapons

Revolutionary War Weapons

Season 52 Episode 7
53:39
Secrets of the Forest

Secrets of the Forest

Season 52 Episode 8
53:41
Ultimate Crash Test: Countdown

Ultimate Crash Test: Countdown

Season 52 Episode 10
53:29
NOVA Season 52

Ultimate Crash Test: Impact

Season 52 Episode 11
53:27
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NOVA

Oklahoma's Deadliest Tornadoes Preview

On May 20, 2013, a ferocious EF5 tornado over a mile wide tore through Moore, Oklahoma, inflicting 24 deaths and obliterating entire neighborhoods. It was the third time an exceptionally violent tornado had struck the city in 14 years. Yet predicting when and where these killer storms will hit still poses a huge challenge. Why was 2011—the worst ever recorded tornado season?