Blowin' in the wind Flapping flags may shed light on how fish
school and birds flock OFTEN it pays not to be leader of the
pack—just ask a racing cyclist or a Formula One driver.
Conserving energy by following the leader, a trick known as
slipstreaming, can give a rider or driver that extra bit of
juice to pull ahead at the very last moment. In the natural
world, however, bodies are more likely to be flexible, like a
fish's, rather than rigid, like a car's. In these systems, as a
recent paper in Physical Review Letters reports, it is the
leader that enjoys a significant dynamic advantage over the
followers. Jun Zhang of New York University came to this
conclusion obliquely, by examining one of life's burning
questions: why is it that flags flutter in a breeze? Flags are
good analogues of birds and fish because all three change their
shape as they move through a fluid. In 2000 Dr Zhang did some
experiments to study the motion of thin silk filaments (standing
in for flags) in flowing films of liquid dishwashing