Ast 105 1st edition Lecture 26 Current LectureStructure of the Universe- 3 global universes we can have: flat, spherical, hyperbolic- If Puniv>Pcritical- Force of gravity will win out over kinetic energy - Universe has positive curvature ( the universe is closed)- Parallel laser beams converge (will cross)- Space is spherical - If Puniv.=Pcritical - Expansion and gravity in perfect balance- Universe has no curvature ( universe is flat)- Laser beams remain parallel - Space is flat - If Puniv.<Pcritical - Gravity will lose out to kinetic (expansion)- Universe has negative curvature - Laser beams will diverge - Space is hyperbolic- Observations of the CMBR point towards a flat universe - Inflation theory also yields a flat universeDark Energy - The last 15 years, we have noticed that instead of slowing down, the expansion of the universe is speeding up! This suggests a repulsive force that is pushing matter apart.- This measured accelerated expansion of the universe is described by: dark energy (or vacuum energy or cosmological constant)- We want to add up all the matter to see if it yields a flat universe- For a flat universe: Material Contribution of the Mass of the Universe- Hot baryonic (ex: stars) 0.05%- Cold Baryonic (ex: things that don’t 3.5%These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.shine= planets, black holes)- CMBR 0.005%- Hot dark matter (ex: neutrinos) 0.3%- Cold dark matter (ex: super-symmetric particles)23.0%- Dark Energy 73.0% (approx.) o Dark energy conveniently solves 2 problems: Accelerated expansion Required mass/energy for a flat universeo We know about 4%, but we don’t know for the other
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