AST2002 Lecture Notes - Lecture 25: Nucleosynthesis, Weak Interaction, Fundamental Interaction
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Hu(cid:271)(cid:271)le"s la(cid:449): (cid:373)ost gala(cid:454)ies ha(cid:448)e redshifts (cid:894)(cid:373)o(cid:448)i(cid:374)g a(cid:449)a(cid:455)(cid:895); if (cid:455)ou re(cid:448)erse the u(cid:374)i(cid:448)erse"s e(cid:454)pa(cid:374)sio(cid:374), (cid:455)ou"ll e(cid:448)e(cid:374)tuall(cid:455) get to the u(cid:374)i(cid:448)erse"s (cid:272)o(cid:374)de(cid:374)sed state. The early universe must have been extremely hot and dense: high temperature = lots of particles and radiation. Photons converted into particle-antiparticle pairs and vice versa: e = mc^2. Four fundamental forces between particles: strong force: binds nuclei together (holds protons and neutrons together, weak force: determines how particles remain as particles; responsible for radioactive decay, gravity, electromagnetism. Theor(cid:455): i(cid:374) its earl(cid:455) stages, the u(cid:374)i(cid:448)erse"s high te(cid:373)peratures (cid:373)a(cid:455) ha(cid:448)e (cid:272)aused the for(cid:272)es (most likely strong, weak, and electromagnetism) to combine: eventually, the forces separated, hence the existence of the known forces. Amounts of matter and antimatter are nearly equal. Elementary particles filled the universe: quarks combined -> formation of protons and antiprotons. Universe begins cooling; forming heavier nuclei -> blasts helium apart. Ele(cid:272)tro(cid:374)s a(cid:374)d proto(cid:374)s (cid:894)free (cid:272)harges(cid:895) (cid:449)ere(cid:374)"t (cid:272)o(cid:373)(cid:271)i(cid:374)i(cid:374)g; just free io(cid:374)ized parti(cid:272)les.
