Science Questions

Could a bee the size of a person fly?

Tue, 22nd Mar 2016

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Question

Ultraviolet Keating asked:

If a japanese honey bee was as large as a person, could they fly? And how much heat could their wings produce?

Answer

Chris Basu, expert in animal biomechanics, answered Ultraviolet's question... Bumblebee - Bombus terrestris

Chris Basu - Yes, itís a great question.  Just the imagery you know, imagining a bee the size of a person, itís great.  But we do have this problem when we talk about scaling small animals up to larger sizes.  If you imagine a cube, if you double the size of that cube, you actually increase itís weight by eight times and thatís just a generalised law of scaling.  When you scale up a bee to the size of a human, if you keep the shape and size of the wings the same, the wings actually become too small for the bee to get enough lift to get off the ground.  The muscles are too small and also the material properties are just not good enough any more.  The wings might become overly heavy, they might just break before anything actually happens; thereís no way theyíd be able to get off the ground.  But thereís fundamental problems as well; bees donít actually have lungs.  They rely on the normal diffusion of air going from the outside into the inside of the body through a network of tubes and if you scale a bee upÖ

Chris - But arenít we the same?  Donít we have a network of tubes that carry air from the outside into the inside of the body?

Chris Basu -   We do, but weíre active breathing, so we actively draw air into our chest and then weíve got circulation which distributes the oxygen around our body but bees donít really have that so thereís a size limitation that they can get to before they would just suffocate.  So, if you imagine a bee the size of a human, it wouldnít last long at all, it would just fall over and die very quickly.

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A bee the size of a person couldn't breathe. Bored chemist, Tue, 2nd Feb 2016

The largest known flying insect is a dragonfly from the Carboniferous period, with a wingspan of over half a meter.
It is thought that the oxygen content of the air was higher at that time.
See: http://en.wikipedia.org/wiki/Meganeura

The oxygen content can't get very much higher than the current 20%, as many substances become flammable when the oxygen content of air is above 50%.

But if we are talking wild speculation (like human-sized bees), consider what might be possible on a planet with a low gravity and a dense atmosphere. After all, dolphins are similar in size to a human, and they manage to stay afloat without too much in the way of wings. evan_au, Tue, 2nd Feb 2016



In the Carboniferous period atmospheric oxygen peaked at 35%.
yellowcat, Sat, 28th May 2016

There's an old saying in aviation: "A piano will fly if you put a big enough engine on it". And a rocket-powered airplane can indeed fly with the tiniest of wings. The problem is to match the engine power to the wing loading. You need about 0.5 horsepower to lift 1 lb/sq ft of wing area. Man-powered aircraft have flown, with wing areas of 300 sq ft or more, because a human can generate up to 0.3 horsepower for a short time, but an insect the size of a human can't consume oxygen fast enough to match that - you need active lungs rather than passive spiracles. Whilst the power/weight ratio of an insect  is much higher than a human, the engine doesn't scale up to large sizes. Dogs and birds, however, have a much larger continuous power/weight ratio than humans thanks to their very large chests. alancalverd, Sat, 28th May 2016

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