This is the memorial monument for Hiroshima City Girls’ High School.
It is located southeast of Peace Memorial Park, but it was built before the Park was constructed.
Please take a look at this photo. In the relief on the front of the monument, the girl in the center is holding a box with the furmura “E=MC2“.
The Tragedy
This school suffered the greatest loss among all schools in Hiroshima.
On August 6, 1945, 544 students and 7 teachers were mobilized for building demolition work near the hypocenter.
All of them lost their lives. Including those at oher work sites, the school lost 676 students and teachers.
The Reason for E=mc2
The monument was originally built in 1948 on the school grounds. At that time, Japan was under Allied occupation. Because of the press code enforced by GHQ (General Headquarters, the Supreme Commander for the Allied Powers), people were not allowed to write about the atomic bomb. Therefore, they engraved E=mc2 instead as a way to remember the tragedy.
The Science
Einstein’s formula, E=mc2, is famous. However, I didn’t know what it meant.
This formula shows the amount of energy produced by the loss of mass.
In Hiroshima, 0.7 g of mass was lost as a result of the atomic bombing.
Presicely, about 64 kg of uranium-235 was used, and only 1 kg underwent nuclear fission. The mass lost in this process was just 0.7 grams—roughly the weight of a single paper clip.
Using Einstein’s formula (E=mc2):
Mass (m): 0.0007 kg
Speed of light (c): 300,000,000 meters /second
Energy(E): 0.0007 × 300,000,000×300,000,000 = 63 trillion joules
According to the formula, this 0.7 g of lost mass created 63 trillion joules of energy—equivalent to 15 kilotons of TNT. The formula reminds us that an almost invisible loss of mass created unimaginable destruction.
Standing in front of this monument, I am deeply struck by the thought of the immense tragedy brought about by the mass of a single paper clip.
コメント