[net.math] History/Explanation of Polish Airliner Joke

rpw3@sri-unix (06/28/82)

The following facts, as requested:

The "Polish Airliner Joke" (recently put to net.jokes) was first
heard (by me) at a San Diego or Anaheim DECUS meeting about 8-9 years
ago. I believe it was invented by Ashley Grayson, who was a DEC edu-sales
person at the time.


******SPOILER****** ******SPOILER****** ******SPOILER****** 

For non-engineers:

The "poles" referred to are the values of complex frequency
in the s-transform or z-transform equations of input/output
for which the denominator of the equation [usually a rational
polynomial in e^(i*omega*t)] goes to zero, causing the output
to go to "infinity" ==> **CRASH**. The "plane" is the plot
of complex frequencies: -x/+x is exponentially decreasing/increasing
amplitude of response; +/- y is real frequency. For values of
a driving function on the "right half" (i.e., +x), the input
(and presumably the output) in exponentially increasing. If
all of the poles are on the right half, the system can do it
to itself (to destruction) without any input (other than
a miniscule bit of noise to get it oscillating). Enough?

wagner (06/30/82)

Help!  Why was the explanation mentioned above posted 4+ times?

Or are we the only ones who got it that way?  Are we having transmission
problems?

Michael Wagner, UofToronto Computing Services