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"It was as unbelievable
as a cannon ball shot on a paper bouncing back."
Ernest Rutherford, Nobel Prize winner in 1908
This was the shocking results of testing he described.
Another cosmos, the atom
“All matter is made of atoms.”
- Ancient Greek philosopher Democritus
The atom means it cannot be further divided.
Atom: comes from the Greek word “atomus,” meaning “cannot be divided”
However,
Joseph John Thomson discovered an “electron” inside an atom in 1897.
Thomson thought of a round-shaped atom
wherein oval electrons are embedded here and there.
After Thomson’s discovery of the electron,
many actively researched the structure of an atom.
Because an electron that is a part of an atom has negative electricity,
while an atom is neutral,
scientists thought something with positive electricity would exist.
University of Manchester, United Kingdom, in 1909
Thomson’s student, Rutherford, took interest in an atom’s structure.
“If so, how is negative electricity distributed in an atom?”
Rutherford’s tested by shooting small particles at a speed of 16,000 km
towards atoms composing a thin metal foil.
Shot at a film several hundred times thinner than paper
At a speed several thousand times faster than a bullet
Rutherford thought most particles would pass through the atom.
However, some particles bounced back.
“Electrons make particles shot at an atom bounce back?”
“But the mass of an electron is up to 8,000 times smaller than a particle.”
“It was as unbelievable
as a cannon ball shot on a paper bouncing back.”
“Is there then perhaps something very firm at the center of an atom?”
Thus, an atom’s nucleus was discovered.
Although it takes up most of an atom’s mass, it is 10,000 times smaller than an atom.
An atom model was thus later created.
“A nucleus is at the center of an atom and electrons rotate around it.”
What if an atom were as large as the dome of St. Peter’s Cathedral?
Then, its nucleus is as small as a grain of salt.
What if an atom were as big as a baseball field of a radius of 100 m?
Then, its nucleus is as small as a coin of a radius of 1cm.
Rutherford discovered that a nucleus is 10,000 times smaller than an atom.
If we were to leave only one sentence among all the scientific knowledge
gained by humanity to future generations,
it would be “all matter is made of atoms.”
- 20th century physicist Richard Feynman