Ant strength

Discussion in 'Physics & Math' started by domesticated om, Jun 4, 2006.

  1. domesticated om Interplanetary homesteader Valued Senior Member

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    3,231
    There is something that's been bothering me about the strength claims for ants.
    - People say that the ant is considered strong because they can naturally lift up to 5 times their own body weight. If scaled to relative human size, a 150 lb ant carrying a 750 lb object doesn't seem right somehow. The reason it seems wrong to me is because of earth's gravity- if you dropped miniscule ant out of an airplane, it wouldn't really reach a terminal velocity that could kill it. If the ant weiged 150 lbs however, it's impact to scale would be alot worse (would hit the ground at around 120-150 mph, and make a really horrific 'splat' sound when it landed). I'm thinking that there is something to the earth's gravitational pull that's absolute, and isn't taken into consideration when people talk about ant strength.......but I have no idea what it is.

    I am terrible with math, and this question is really just a hunch, but am I on to something?
     
  2. DaleSpam TANSTAAFL Registered Senior Member

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    1,723
    You are right, the strong ant thing is simply wrong. The reason is related to the so-called Square-Cube Law. Basically, the amount of force a muscle can generate is proportional to the square of the size (the cross sectional area of the muscle) but the weight is proportional to the cube of the size (the volume). This means that every time you double the ant's size you would multiply its strength by 4 and its weight by 8. So it would get relatively weaker as it gets bigger.

    That ant that lifts 5 times its body weight, if scaled up 350 times to be human sized, would not even be able to lift 2% of its weight, its own weight would suffocate it. That is largely the reason why even the largest insects are still rather small. On the other hand, the human that can lift about half of his body weight, when scaled down to the ant size, would be able to lift 175 times his own weight, not just 5 times.

    So why don't we see mammals that are the size of ants? Wouldn't they have a competitive advantage being so much stronger. It turns out to be another square-cube law. The amount of heat generated by and the amount of water in an animal is proportional to the cube of the size of the animal while the rate of heat loss and water loss is proportional to the square of the size. So our ant-sized human would die of dehydration in about 12 min (instead of about 3 days) and would easily die of hypothermia.

    -Dale
     
    Last edited: Jun 4, 2006

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