Unit 16
The nucleus.
The energy inside the nucleus: fission and chain reactions, fusion, radioactive dating, and quarks.
Before this unit
The unit, lesson by lesson
Lessons
4 lessons · 26 practice questions · about 2 hours
Nuclear fission
A uranium nucleus that tears in two: why a neutron splits it, where the energy comes from by E = mc², the multiplication factor k, control rods that hold a chain steady, and why a growing chain multiplies itself.
Nuclear fusion
Light nuclei that join into heavier ones: the repulsion to overcome, heat that is speed, a rate that soars with temperature and with the square of the fuel density, the neutron that escapes the plasma, and why the Sun gets away with less.
Radiometric dating and the age of the Earth
A zircon crystal that sets its own clock to zero: the ratio of lead to uranium after a half-life, reading the age from the ratio, a clock that is spent and a clock that doesn't fit, lead that leaks and clocks that stop agreeing, and how we know the age of the Earth.
Particle physics and the Standard Model
What is inside a proton: quarks and fractional charges, mass that is mostly energy, a gluon string that pulls with the weight of fifteen tonnes and snaps into a new particle, and the three generations of the Standard Model.