eries of surprises.

"Castle/Bravo" was the largest nuclear weapon ever detonated by the
United States. Before it was set off at Bikini on February 28, 1954,
it was expected to explode with an energy equivalent of about 8 million
tons of TNT. Actually, it produced almost twice that explosive
power--equivalent to 15 million tons of TNT.

If the power of the bomb was unexpected, so were the after-effects.
About 6 hours after the explosion, a fine, sandy ash began to sprinkle
the Japanese fishing vessel Lucky Dragon, some 90 miles downwind of the
burst point, and Rongelap Atoll, 100 miles downwind. Though 40 to 50
miles away from the proscribed test area, the vessel's crew and the
islanders received heavy doses of radiation from the weapon's
"fallout"--the coral rock, soil, and other debris sucked up in the
fireball and made intensively radioactive by the nuclear reaction. One
radioactive isotope in the fallout, iodine-131, rapidly built up to
serious concentration in the thyroid glands of the victims,
particularly young Rongelapese children.

More than any other event in the decade of testing large nuclear
weapons in the atmosphere, Castle/Bravo's unexpected contamination of
7,000 square miles of the Pacific Ocean dramatically illustrated how
large-scale nuclear war could produce casualties on a colossal scale,
far beyond the local effects of blast and fire alone.

A number of other surprises were encountered during 30 years of nuclear
weapons development. For example, what was probably man's most
extensive modification of the global environment to date occurred in
September 1962, when a nuclear device was detonated 250 miles above
Johnson Island. The 1.4-megaton burst produced an artificial belt of
charged particles trapped in the earth's magnetic field. Though 98
percent of these particles were removed by natural processes after the
first year, traces could be detected 6 or 7 years later. A number of
satellites in low earth orbit at the time of the burst suffered severe
electronic damage resulting in malfunctions and early failure. It
became obvious that man now had the power to make long term changes in
his near-space environment.

Another unexpected effect of high-altitude bursts was the blackout of
high-frequency radio communications. Disruption of the ionosphere
(which reflects radio signals back to the earth) by nuclear bursts over
the Pacific has wiped out long-distance radio communications for hour