The highest G-force a human can stand

Even when life seems up in the air, gravity has a way of keeping you grounded. But occasionally it just weighs people down. The same holds true of G-forces (short for gravity forces), which can increase your perceived weight when you accelerate. In fact, subjecting your body to extreme G-forces will not only make you feel both fast and fat; it can knock you unconscious

The knockout power of G-forces first became worrisome to experts during the first World War, when pilots would faint in the middle of dogfights, according to Nova. So when Snoopy bested the Red Baron in aerial combat, he might have had some assistance from G-forces. What's the highest G-force that Snoopy or — better yet — a non-cartoon human can take before the Sandman comes knocking? The answer depends on a number of factors, so let's start by clarifying a few things. 

Gizmodo explains that 1 G amounts to "the pressure applied to the human body [by Earth's gravity] at sea level." This is the same amount of force that causes falling objects to accelerate at approximately 32 feet (9.8 meters) per second squared. A sneeze, by contrast, generates nearly 3 Gs, or three times the force of gravity. If your body accelerated at the rate of a sneeze, you would be roughly 3 times as heavy as you are now.

Your ability to withstand G-forces depends heavily on their direction. Here, it's important to distinguish between positive and negative Gs. Positive G-forces push your innards from front to back when you accelerate forward or force blood from your head to your feet when you accelerate upward. By contrast, negative G-forces push your insides from the back to the front when you accelerate backwards or send blood from your feet to your head when you accelerate downwards. 

Negative Gs are a real doozy for humans, particularly when they cause blood to rush to your head. It only takes negative-2 or negative-3 Gs to put out your lights like a candle in a windstorm.  Positive G-forces that send blood from your head to your feet won't put you to sleep quite as easily. The average person will go night-night when they hit 4 or 5 positive Gs, and a fighter pilot can be trained to endure up to 9 Gs. 

For years, experts believed a pilot couldn't endure more than 18 Gs before their soul hit the eject button on their body, and the pilot promptly died. But this conclusion was based on plane crashes. In the 1940s, Air Force physician John Stapp surmised that the pilots were dying from crash-related "mangling" rather than G-forces themselves. 

Stapp tested his theory with rocket-powered sleds, which eliminated complicating factors like the twisted metal and mutilation that came with plane wrecks. In the 1950s, he subjected his body to an unprecedented 46.2 Gs, which made "his 168-pound frame [feel] like it weighed just over 7,700 pounds." In the 1970s, Air Force Major John Beeding topped that record, withstanding a jaw-dropping 83 Gs. In both cases, the key was keeping the exposure time at a minimum. Beeding, for example, only endured the ordeal for .04 seconds. Battering your anatomy with that kind of force for extended periods of time would do serious damage.