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Reaction time is a physiological response to stimuli, and a crucial component in dodging bullets. And before we get deeper into the science, we must request that you not experiment with bullets at home.

Dodging bullets depends on both the type of stimuli you sense and how quickly your body reacts—a skill that comes with practice, training and genetics.

Your reaction can be in response to a number of different types of sensory stimuli. You can hear something like a gun shot, see something like the flash of a camera, smell something like burning popcorn, taste something like a rotten tomato, or even feel something like a hot pan. Each of these senses can be used to trigger a response in your body.

Babies do not necessarily know what to do when they touch a hot pan, though a professional chef undoubtedly does. It comes down to training. Developing that response depends on how much time you’ve spent training and the method by which you have trained your body to respond to it.
 

Training

Although there are physiological limits to how fast humans can react, you can increase your speed with practice. Sometimes, you can react too well. In the Olympics, it is not legal for sprinters to react to the starting gun faster than 1/10 of a second. Some sprinters trained themselves to react faster, but were given “false starts” and were brought back to the starting line. Though an advantage in most time-sensitive cases, the Olympics is one place you don’t want to jump the gun.
 

Bullets

The average bullet travels at 2,500 feet per second (around 1,700 mph). If you reacted to the sound of the gun going off and required 0.20 seconds (twice that of the fastest Olympic sprinters) to react, then you would need to be at least 500 feet away to successfully dodge a bullet. The problem is that sound travels at 768 miles per hour (1,126 feet per second)—about half the speed of the bullet. In this case, the bullet would hit you before you even heard the gun fire off.
 

Arrows

The average arrow travels at about 250 feet per second. Let’s say you respond at the moment you see the shooter releasing the arrow. With a reaction time of 0.20 seconds, you would need to be 50 feet away to react and dodge the arrow.