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But Not Simpler

But Not Simpler

Thinking way too hard about science and pop-culture

You Can’t Take a Bullet for Someone Hollywood-Style, Because Physics

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No matter how many times you’ve seen the movies and the TV shows that have a protagonist leaping in the path of a bullet, physics forbids such sacrifice. Because of a bullet’s radical speed, you can’t jump in front of it, but you could get in its way. It’s not as dramatic, but it does save lives. The Secret Service saved a president that way.

Bullets move fast enough to create their own shockwaves, like a speedboat on the water.

Bullets are fast—even a 9-millimeter handgun launches lead at Mach 1. And the bigger the bullet gets, the more grains of gunpowder it carries, the faster it goes. Modern rifles can fling the small pieces of metal at half the velocity needed to escape the gravitational pull of the Moon. Our weapons are so fast, in fact, that you couldn’t get in front of a bullet even if you saw it coming.

Thanks to due diligence done by the Discovery Channel’s Mythbusters, we already have a sense of the range at which moving in response to a bullet is possible. In their testing, Adam and Jaime established a “kill zone”—the distance at which you could not dodge a bullet given human reaction time.

But to dodge (or jump in front of) a bullet in the first place, you have to see it coming. The Mythbusters estimated that you’d have to witness a bullet fired from over three football fields away in order to have enough time to dodge it. Any would-be hero with a reaction time longer than Jamie’s would need to see the bullet from further away—something that subsequent testing deemed impossible.

Hollywood makes it seem like average Joes and Janes can suddenly make that superhuman leap in front of lead for two reasons—speed and sight. But physics has no sympathy for your heroic aspirations. Optics doesn’t either. You are not that fast. You can’t see a bullet fired from that far away. If the testing that the Mythbusters did holds up, there is no way you could see a muzzle flash from much further than a hundred meters or so away. Point-blank shooters fire too close for you to even blink, and snipers worth their salt use bullets that suppress muzzle flash. Brightly flashing guns make for good shows and movies, but there is no such “take a bullet” cue in real life.

But you could stand in front of a bullet in anticipation of being a hero. It’s happened before.

McCarthy (far right) few eye-blinks before the attempted assassination of Reagan (waving). Left, in white trenchcoat, Jerry Parr, who pushed the President, body-sheltered by McCarty, into the car.

Outside of the Washington Hilton on March 30, 1981, then president Ronald Regan enters his car amid the crowd gathered to hear his speech. John Hinckley, Jr emerges not with admiration but with bullets. Shots ring out. In a motion burned into reflex, Secret Service agent Tim McCarthy shifted from his alert position into one like a baseball catcher in front of the president. One of the next shots stuck McCarthy directly in the stomach. He then defined what it was to “take a bullet.” He made a full recovery.

The Secret Service, whose agents are probably at the heart of the trope to dive in front of bullets in TV shows and movies, never stopped a bullet that way. Agent McCarthy indeed took a bullet for someone, but only after a few shots rung out and only acting as a human shield. That’s what taking a bullet really looks like. Heroes are meat shields, not stuntmen.

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Image Credits: Supersonic Bullet Shadowgraph via NASA/JPL

Screengrab from Discovery Channel’s Mythbusters

Assassination attempt photo uploaded to Wikipedia from the Ronald Regan Library Archives

The views expressed are those of the author and are not necessarily those of Scientific American.

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