What concept lies beneath the little boy?
Umm, did you know the US dropped “Little Boy” on Hiroshima on August 6, 1945?? (I guess I already used enough hook sentences 😂) Let me get to the point…
“Little Boy” was the first nuclear weapon — a uranium gun-type fission bomb — ever used in warfare, and it marked a turning point in military history because of its devastating effects. But how does it work? What concept lies beneath it?
Fission — splitting into parts — is the process of dividing the nucleus of an atom, which releases a large amount of energy.
In the 1930s Enrico Fermi showed that exposing elements to neutrons could transform them into other, often radioactive, elements. After Fermi’s work, Otto Hahn and Fritz Strassmann bombarded uranium with neutrons and found radioactive products (including a barium isotope). They concluded that slow neutrons could cause the uranium nucleus to fission — to split apart into two smaller nuclei.
When a neutron strikes a uranium-235 (U-235) nucleus, the nucleus can absorb the neutron, become unstable, and split. The split releases energy and emits additional neutrons.
Weapons-grade uranium is uranium enriched so that at least about 90% of the atoms are U-235. Btw, plutonium (most commonly Pu-239) can also be used as nuclear-weapon fuel.
In a properly functioning bomb, more than one neutron ejected by each fission causes further fissions — a chain reaction. Think of a large circle of marbles representing nucleons (protons and neutrons). If you shoot one marble — a neutron — into the circle, it hits a marble, which knocks into others, which knock into more, and so on; the effect rapidly multiplies.
P.S., Capturing and splitting happens in around 1 picosecond!
Sources:
https://physics.bu.edu/py106/notes/RadioactiveDecay.html https://science.howstuffworks.com/nuclear-bomb.htm https://www.nrc.gov/materials/fuel-cycle-fac/ur-enrichment https://www.nrc.gov/materials/fuel-cycle-fac/ur-enrichment https://science.howstuffworks.com/atom.htm https://www.britannica.com/science/nuclide https://evolution.berkeley.edu/the-nitty-gritty-on-radioisotopic-dating/