On 18 Dec 2006 13:19:33 -0800, "dpb" wrote:


DK wrote:
You need to know the story about the cat that walked across the
suspension bridge. The harmonics of the footsteps were amplified and
destroyed the bridge.
...

_I'd_ like to know about that one...
Here you go:

How Resonance Can Break a Bridge

The power of resonance goes beyond shattering a glass or torturing
eardrums with feedback; it can actually destroy large structures.
There is an old folk saying that a cat can destroy a bridge if it
walks across it in a certain way. This may or may not be true, but it
is certainly conceivable that a group of soldiers marching across a
bridge can cause it to crumble, even though it is capable of holding
much more than their weight, if the rhythm of their synchronized
footsteps resonates with the natural frequency of the bridge. For this
reason, officers or sergeants typically order their troops to do
something very unmilitary—to march out of step—when crossing a bridge.