Introduction: About the A-Bomb
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                      <CENTER><H1>ENERGY GENERATED BY THE EXPLOSION </H1></CENTER>

The atomic bomb dropped on Hiroshima generated a huge amount of energy when
it exploded. The amount of energy generated by the bomb was equivalent to
the amount of energy generated by a 15-kiloton TNT explosion.

Half of the energy was consumed when the explosion generated an ultra high
air pressure which resulted in very strong bomb blast (wind). One third of
the energy was consumed when the explosion generated heat, while the rest of
the energy was consumed when the explosion generated radiation.



<B><H1><CENTER>HEAT</CENTER></H1></B>

On the ground, beneath the explosion center(hypocenter), the temperature
rose to approximately 7,000 degrees F. On the stairway of the entrance to a
bank, which was 1/8 mile from the explosion center, a man was sitting
waiting for its opening. The surface of the stone stairway was changed by
the immense heat. The part where the man was sitting remained unchanged
because his body absorbed the heat.

Roof (ceramic) tiles on houses within 1/3 mile radius from the explosion
center melted, and gray stones which contained silicon particles became
white. The clothes which people wore were burnt by the heat within 1 1/4
mile radius from the explosion center.



<B><H1><CENTER>BOMB BLAST</CENTER></H1></B>
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An ultra high pressure was generated by the explosion. The wind velocity on
the ground beneath the explosion center was 980 miles/hr, which is five
times stronger than the wind generated by strong hurricanes. The pressure
was 3.5 kg per square centimeter which is equivalent to 8,600 pound per
square feet.

At a point that was 1/3 mile from the explosion center, the wind velocity
was 620 miles/hr; the pressure was 4,600 pound per square feet. Most of
concrete buildings inside this range were completely destroyed.

Even a mile from the explosion center, where the wind velocity was 190
miles/hr and the pressure was 1,180 pound per square feet, all brick
buildings were completely destroyed.



<B><H1><CENTER>RADIATION</CENTER></H1></B>

The explosion generated Alpha, Beta, Gamma and neutron rays. Alpha and Beta
rays were absorbed by the air and did not reach to the ground. Gamma and
neutron rays were strong enough to reach the ground; thus it was these rays
that affected people.

Within 1/16 mile radius from the explosion center, most people died within a
few hours (even in the case where they were not directly exposed to the heat
or wind). Within a half mile radius, most people died within 30 days after
the explosion.

The people who entered the area within a half mile radius from the explosion
center in the first 100 hours after the explosion were also affected by the
remaining radiation on the ground.

Fortunately it has not been observed that the long term effects of radiation
affected A-bomb survivors nor that a radiation exposure caused genetic
damage 

By the end of 1945 the estimated number of people who died as a direct
result of the bomb was 140,000.  The collection of statistics, by the
Hiroshima City Government, did not commence until 1952. For the period 1946
to 1951 the number of deaths due to the bomb was estimated at 60,000. As the
number of deaths among survivors, in the first ten years of the survey,
showed little difference from the population as a whole, it has been
concluded that the number of people who died as a direct result of the bomb
was approximately 200,000.
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