ELi5: How come ants can survive almost any fall but humans can’t?

Question

I know it has to do something with mass, but i’m clueless.

In: 0

Answer 1

Reason 1: square cube law on impacts: All the weigh of the ant tries to splat the ant at impact. But the weight is very small.

If you take an ant and scale it up to be 10 times bigger, then the volume of the ant will be 10*10*10 times bigger. The weight will be 1000 times bigger. Now the scaled up ant has to take 1000 times more impact force. And this force will be spreaded on a surface that is only 10*10 bigger. So, the pressure in the impact is already 10 times more (force per square inch). There’s 10 more lenght of legs to absorb the hit, but that’s not gonna make a difference to the impact on the foot. That’s why a fall on your foot will let you uninjured in the head but the hit to the foot will break the foot or ankle or knee.

You can scale it up more and more and you see how big the difference becomes. A 100 times bigger ant has 100 times more pressure per square inch. The chances of damage go up, at that pressure the tissues will be squeezed (what happens when you take a hit and your skin becomes blue, that’s dead tissue). There’s 100 times more leg lenght to absorb the hit, but again it won’t work to save the first part that hit the ground.

Reason 2: Square cube law also affects terminal velocity.

Ant: 1 weight 1 surface to make air drag.

Ant 10 times big: 1000 weight, only 100 surface that makes drag.

Ant 100 times bigger: 1million weight, only 10k surface to make drag.

The bigger the object the more it wins versus air resistance. This gives higher and higher free fall speeds.

Conclusion: So an ant will fall slower and with less mass than a human. This give a lot less impact forces.

Of course this is all dumbed down trying to reduce the variables.

If you don’t believe me have a look to a scooter hitting a scooter at 10kmh (paint damage) and a ship hitting a ship at 10kmh (both sink). A ship hitting a ship will make a different type of crash. Cause the mass involved grow cubic while the area that takes the hit grows squared. And again the extra lenght to absorb the impact does not apply to the first contact point. It may save the parts further back, but this is possible if the first parts to hit don’t collapse.