Nowadays, the fastest fastballs top out at around 106 miles per
hour. Writing at his blog “What If?” (“Answering your
hypothetical questions, with physics, every Tuesday”), Randall
Munroe takes the quest for speed to its logical conclusion: What
would happen, he asks, if you pitched a baseball at 90 percent
of the speed of light—around 600 million miles per hour? A ball
traveling that fast, it turns out, would never reach home plate.
Instead, its high-speed collisions with air molecules would
create a growing wave of fusion reactions. As the ball
disintegrated, the energy released would turn the surrounding
air into super-heated plasma. For obvious reasons, the batter
would never see it coming. In the end, Munroe writes, “The shell
of X-rays and superheated plasma expands outward and upward,
swallowing the backstop, both teams, the stands, and the
surrounding neighborhood—all in the first
microsecond....Everything within roughly a mile of the park is
leveled, and a firestorm engulfs the surrounding city.” The