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knows the composition of that me- 
teoroid. 
The problem posed by deriving the 
meteoroid’s dimensions from satellite 
measurements of the intensity of 
infrared radiation was the lack of 
precedent. Since the technique has 
never been applied before, no one 
knows how reliable it is. Deductions 
made from the brightness of visible 
light, on the other hand, are based 
on the “luminous efficiency” method, 
which, although it has often been ap- 
plied, is nevertheless suspect. In this 
method, the mass of the meteoroid 
is computed from a relation between 
meteoroid mass and observed meteor 
brightness. In some cases, this rela- 
tionship has been determined by 
studying the brightness of artificial 
meteoroids fired from rockets. The pa- 
rameters that relate brightness and 
mass depend on what a meteoroid is 
made of, and they have been deter- 
mined from rather small meteoroids. 
We do not know whether the derived 
relationships can be extrapolated to 
objects as large as the 1972 meteoroid. 
Another difficulty is that although 
the August 1972 fireball was seen by 
thousands of people, its visible-light 
brightness is not accurately known. 
There was nothing suitable in the sky 
to use as a standard of comparison. 
Witnesses agreed that the fireball was 
much brighter than a full moon but 
far dimmer than the sun. This still 
leaves considerable margin for error. 
The technique of estimating mete- 
oroid mass from the rate at which 
air resistance slows a flying object is 
sensitive to the composition of the me- 
teoroid, but as mentioned above, the 
composition of the August 1972 me- 
teoroid is simply not known. Most as- 
tronomers have assumed — or guessed 
— that this meteoroid was a stone, 
since the great majority of meteoroids 
are thought to be stones. Laboratory 
measurements of meteorites, however, 
show that even the stone ones vary 
widely in density. Uncertainty over 
the actual density will affect the mass 
deduced from an observed decelera- 
tion since if two objects of the same 
mass travel the same path at the same 
speed, the less dense object, being 
larger, will suffer more resistance by 
the air. Another, less serious problem 
is that the mass of the August 1972 
meteoroid was not constant from one 
observation to the next. As shown by 
the eyewitness reports of smoke be- 
hind the fireball, it was losing mass 
along its trajectory. The smoke, a phe- 
For centuries man feared it, made 
sacrifices to it, wailed over it. Now we 
run to greet it. you are extended a 
unique invitation to witness one of 
nature's most awesome spectacles, a 
total eclipse of the sun. On July 31. 1981 
the British cruise ship, m.s. Coral Prin- 
cess will be positioned 1000 miles off 
the coast of Japan to rendezvous with 
eclipse totality. 
The ORIENT ECLIPSE cruise and expedi- 
tion is the sequel to the six previous his- 
toric VOYAGE TO DARKNESS eclipse expe- 
ditions which successfully intercepted 
totality off the coasts of Nova Scotia, 
Africa, the Caribbean, in the Pacific and 
at Montana s Big Sky eclipse expedition. 
The ORIENT ECLIPSE CRUISE adventure 
offers a distinguished staff of shipboard 
lecturers (including meteorologist Dr. 
Edward M. Brooks) scientific, cultural 
and educational programs, and tours of 
Japan, Hong Kong, Macau and China. 
Join us as we probe earth, sea and 
space for yet another exciting and 
memorable cosmic 
adventure .. 
as we sail • - — i 
into totality 
and beyond. 
ORICNT 
ecupsc 
cruise 
voyage to Darkness Vli 
Orient Eclipse Cruises. Inc. 
1080 Fifth Avenue 
New York, N.Y. 10028 
Please send me more information 
On the ORIENT ECLIPSE CRUISE 
Name 
Address 
City 
State 
Zip 
101 
