PROFESSOR MOORE - 6/8/94
Q: He was unsuccessful?
A: He was unsuccessful.
Q: What method did he employ?
A: Low frequency microphones on the ground. Are you
familiar with the Krakatou measurements?
Q: No.
19
A: In 1883, Krakatou, near Java, made an enormous
explosion and the pressure wave from that went around the world.
seven times, and was picked up and ••• There was a report, a big
analysis by Lord Railey and others •••
Q: A volcanic eruption?
A: Volcanic eruption. Here are the isocomes of the
pressure waves from Krakatou as it went out. From the time it
took the signal to go out and come back, he went to the antipode
which is around Colombia or Venezuela, and came back as a big
spherical wave. It went back and forth around the earth. The
British investigators were able to show that there was a duct up
around the tropopause, and the speed of sound, as I remember, was
something like 310 meters per second instead of the regular 334
that we had at sea level. From that they could deduce the
temperature of the medium in which the sound was propagating and
it was something like minus 25.
Q: How was this detected as a pressure wave in that time
frame?
A: Barograph.
Q: What year?
A: 1883. This is what prompted Ewing.
Q: I'm familiar with barometer-type measurements being
used to measure that pressure wave and the fact that it traversed
the earth, you said seven times.
A: Maurice Ewing had been an oceanographer at Woods Hole
and had found a similar acoustic duct in the ocean. You may be
familiar with what's called Sofar. In 1945 he wrote a letter to
Spaatz suggesting this might be useful in detection of Soviet
activity.
Q: The 1945 letter was kind of the initiative as a means
of detection.
A: That's correct. That caused the Army Air Force to
begin this research.