July 18 , Lecture 5 Continuation, AST201H1
Sun does not burn. To get particles to overcome their mutual repulsion, they have to
have a lot of energy and be very hot. Gas is hydrogen. Need to bind them, bring them
close, electromagnetic force (same charge) so will try to repel. Two protons will try
to repulse each other.
At low speeds, electromagnetic repulsion prevents the collision of nuclei.
At high speeds, nuclei come close enough for the strong force to bind them together.
Sun’s core is more than 15 million Kelvin. Need this to bring those protons together.
Start off with four protons, combine together, what is produced is a new nucleus
that has two protons and two neutrons.
This fusion reaction is called the proton-proton or the “p-p” chain.
Nuclear fusion- smashing nuclei together to form larger nuclei. Two nuclei of
hydrogen to make helium. Can only happen in the universe, centers of stars. Or
explosions called supernova explosions. Don’t have enough energy to make this
happen on Earth.
Nuclear fission- breaking nuclei apart to form smaller nuclei. Same as nuclear plants.
The p-p chain has several intermediate steps.
Step 1: two protons fuse to make a deuterium nucleus (1 proton and 1 neutron).
Heavy hydrogen. These anti-electron, will react something else and will produce
Step 2: Other Protons come in to make Helium-3. Two protons and one neutron.
Step 3: Smash Helium-3 together to make Helium-4 and return the protons.
Neutrino shooting through our bodies. Only interact weakly with gravi