Why does thunder rumble? Acoustic professor Trevor Cox explains that it has to do with the way lightning is a jagged line. "Each little kink is actually generating the sound, and the reason thunder rumbles is because the sound takes different time to come from different kinks because they're all slightly different distances from you," he says.
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Most of us have never been submerged under more than a few feet underwater. But just a few meters down, the water compresses the tissues of your body so that you become more dense. At that point, "You're more likely to sink than float," says Dr. Kevin Fong.