If everyone was Kung fu fighting, and their kicks really were fast as lightning, what would happen?
Short answer: Everyone would die.
Long answer: Lightning travels at about a third of the speed of light. What if people could kick this fast? Moreover, what if everyone, for whatever reason, decided to pair up and start kicking each other?
Taken at face value, everyone would die. The forces required to accelerate limbs up to a fraction of the speed of light would give human legs accelerations in the quintillions of gees. These sorts of accelerations don’t exist anywhere in the universe; neutron star surface gravity is a snail’s pace by comparison. Macroscopic objects simply don’t move this fast. I cannot emphasize more strongly how far outside the realm of ‘plausible’ we are.
But let’s be generous. Suppose the human body could withstand these accelerations. What happens when that first kick is thrown?
As your leg moves forward the nuclei in the air in front of it begin to fuse with the nuclei in your body. The body of your sparring partner also offers negligible resistance, and the kick continues to fly. Your leg is rended from your body and continues forward, becoming a shower of high energy particles. Reactions that normally only occur in high energy particle colliders occur in your leg, producing exotic particles.
And I don’t know where we’re getting the energy for this – a human would have to eat a literal skyscraper of food to get the calories. The kinetic energy of each kick is comparable to the detonation of 10 megatons of TNT. That’s the energy of about 700 Little Boys (the bomb dropped on Hiroshima) per kick.
And remember, everyone is Kung fu fighting. That means that 7 billion of these kick-bombs just went off.
Again, there is simply nothing for comparison, but I’ll do my best to give you a sense of scale here. At the peak of the Cold War, the combined nuclear arsenals of the USA and Soviet Union were in the neighborhood of 12,000 megatons of explosive power. With 7 billion kicks, we release six million times the combined energy of these bombs. Nuclear holocaust followed by nuclear winter is the only way this can go.
Or is it?
It’s obvious by now that person asking this question hates physics and wants everyone to die, so does it really matter if we make one more assumption? I say no, because I’m the disembodied voice of the author and I make the rules.
Let’s assume that humans are indestructible. Not only can we survive that first kick, but we’ll continue to kick. If everyone can kick twice per second, then the power output of mankind is now 6×1026 Watts. The earth is now the brightest star in the solar system.
asked by /u/NinjaRobotPilot
cover image credit: Wikimedia Commons
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