PHYS 005 Lecture Notes - Lecture 18: Gravitational Lens, Cosmic Microwave Background, Baryon
5 Jul 2018
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5/16 Session 18 (Session 20)- The Shape of the Universe
Ch. 26 Sect. 6
Extra credit qs
-if the universe never cooled down, electrons would not be able to recombine with the protons and and
create light to form stars
-if light traveled instantaneously, there would be no section of the universe to observe because it would
just be the whole universe since light doesn’t take time to reach your eyes
Curvature
●Gravity curves space
○E=mc^2
■c= speed of light
■Energy also curves space & time
●Einstein’s theory of General Relativity
○Curvature of space depends on mass
○Curvature of UNIVERSE depends on DENSITY po of universe
■po= combined mass density of universe
●Matter + energy
On avg, universe is flat, but it has tiny bumps and spaces
●The universe is closed
-spherical like Earth
○latitude/longitude lines
■They are parallel, but they still touch
●Universe diverges
○Negative curvature, hyperbolic shape
Determining Curvature
●Depends on po
○We know p,- density of baryonic matter
○Determine dark matter fr x-rays of clusters of galaxies
○Gravity fr. dark & regular matter- eddington limit- equilibrium
●Cosmic Microwave Background allows us to determine density of radiation in universe
○Prad
■How much light/unit of volume- to keep universe at that temperature
●Pc- critical density is exact density
the Universe would have to be flat
○Depends on Ho- hubble constant
○Curvature- density parameter
3 possible outcomes
●If avg density is GREATER than one- universe is CLOSED
Document Summary
5/16 session 18 (session 20)- the shape of the universe. If the universe never cooled down, electrons would not be able to recombine with the protons and and create light to form stars. If light traveled instantaneously, there would be no section of the universe to observe because it would just be the whole universe since light doesn"t take time to reach your eyes. Curvature of universe depends on density p o of universe. On avg, universe is flat , but it has tiny bumps and spaces. The universe is closed -spherical like earth. They are parallel, but they still touch. We know p , - density of baryonic matter. Determine dark matter fr x-rays of clusters of galaxies. Gravity fr. dark & regular matter- eddington limit- equilibrium. Cosmic microwave background allows us to determine density of radiation in universe. How much light/unit of volume- to keep universe at that temperature.
