Why do birds fly and not Humans?

On May 2, 8:10*am, Sanny wrote:

I know in 1800 many experiments were done but all failed and many
people die. But if we use Strong Fibres made of Nanotube May be that
will be very light and help us fly.

Can that be done using recent advances in Material sciences.

Can that happen using better Physics?

Insofar as human-POWERED flight, it was done 30 years ago with the
Gossamer Condor. See -
http://www.youtube.com/watch?v=sp7yv67B5Sc

It was made possible not only by advanced materials, but by computer
analyses to determine the size of the wing needed to fly on the
available power.

oc I know you fly model planes,and you know I also fly model planes
that need no remote control or engine,and can fly at 30mph and never
crash. Humans are mammals and I can think of only one type that flies
In insects the manatee is the best fryer In birds I think the falcon or
the humming bird are the best. Horse flies the fastest. Bee is the
smartest. Mosquito most deadly Chicken best for food Birds and fish
relate well for they need the medium they are immersed in to stay up..
Well I left out albatros(gooney birds Go figure Bert