As we celebrate our newfound imagery (and accompanying scientific data) of Pluto, our quaintly controversial distant solar neighbor, we need to make certain we do not forget to ask the most important of questions. Namely, if you were to fall on Pluto, how high up would you have to be to die on impact?
Sure, Pluto only has 0.063 g (6.3% of the gravity of Earth) to attract you to its surface, but any amount of gravity can accelerate you to an unwanted demise given enough distance on which to act. Without even the aide of an atmosphere of any significance to break your acceleration, it is simply a matter of calculating the velocity of your body when it ‘lands’ on that heavenly body. Well, it is not quite that simple.
You see, the issue at hand is not Pluto, its gravity, or the improbability of your ever being under the influence of the gravity of Pluto. The issue is you. At what height, and thus relative velocity, can you survive a fall here on Earth? There are some astounding records of accidental falls from tremendous heights that some individuals have survived. There are are also plenty of records showing other individuals expiring from incredibly short falls (though mostly these latter are dependent on if they fell on their head or if they are so fragile that any fall of any kind from any height would result in some form of injury).
If we were to go with the more extreme heights possible, you could theoretically fall from very great heights indeed. On Earth. Due to terminal velocity (the atmosphere breaking our fall), our fall from a thousand feet is more or less identical to our fall at ten thousand feet. This does have a limit, however. If you were to fall from Near Earth Orbit, you would accelerate to speeds far in excess of what most people recognize as Terminal Velocity, as the thinner atmosphere at that height would offer far less resistance, and you could then puncture through the thicker gasses at lower elevations like a bullet. This is, of course, irrelevant to the current question, especially since you would likely burn up from the friction of the thicker lower atmosphere long before you hit the earth.
Assuming you are not space jumping, or surfing, into Earth’s gravity well, we can safely state that your maximum velocity upon ‘landing’ would be Terminal Velocity as it is understood in popular culture. Which at 54 m/s (177.165 ft/s or 120.795 mph) is sufficient to render most humans ex-humans, with only the rarest of exceptions. To reach that velocity on low gravity Pluto, you would need to jump from a height of 2500 m (8,202.1 ft or 1.55 miles). That is a long way down. Problem is, it is highly unlikely that you would defy statistics and survive a landing of that velocity, on Earth or Pluto.
Okay then, how do we determine the correct height? We cannot. There are too many factors, such as the softness of the ground, what position your body is in and thus what part of it impacts, if you are relaxed (or unconscious), etc… So I will use this quoted height of 10 m where you will survive with ‘very serious injuries’. At a 10 m drop, your velocity will be 14 m/s (45.95 ft/s or 31 mph). The Plutonian equivalent height you could fall from is 168.1 m (551.5 ft or one tenth of a mile). That is slightly less than the Washington Monument’s height. Or 42 elephants stacked on top of each other, or whatever other silly height equivalent you prefer to measure large numbers in.
So, in conclusion, if you find yourself suddenly ejected into raw space above the surface of Pluto, and assuming you have the basic needs of an enclosed suit with enough air to survive that locality, you had better hope you are only 551.5 feet from the surface, else you are unlikely to live. How you get emergency services to assist you upon your successful, if still likely traumatic, landing is up to you.
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