Introductory Astronomy: Chapter 18

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Big Bang
the theory that the universe originated 13.7 billion years ago from the cataclysmic explosion of a small mass of matter at extremely high density and temperature – generated the expansion of motion that we observe today
distribution of galaxies
scattered across approx. uniformly – therefore, universe is approx. the same in all directions with no apparent center
motion of galaxies
motion away from us is caused by the expansion of the Universe – no center of expansion – as the galaxy expands, wavelengths are altered and create a redshift
age of the universe
13.7 billion years old
center of the universe
we appear to be at the center, however, the Universe is expanding no matter where you are located within it
cosmological principle
on sufficiently large scales, the universe is homogenous and isotropic – matter is evenly distributed
Olber’s paradox
the argument that the darkness of the night sky conflicts with the assumption of an infinite and eternal static universe
cosmic horizon
the greatest distance it is possible to see out into the universe given its age and rate of expansion – lies at an approx. distance in ly equal to the age of the Universe
CMB (cosmic background radiation)
leftover thermal energy from the Big Bang – radiation is visible in all directions – has a temperature of 2.73 K
formation of the galaxies
believed to have formed similar to stars, but on a much larger scale – matter was uniformly spread out – dark matter clumps are critical to early formation!
origin of the universe
young Universe was extremely hot – mix of gas and radiation
Gamow’s hypothesis
universe began as fundamental particles which were then fused together into heavier elements during the Big Bang – helium should have been created by nuclear fusion
matter consisting of elementary particles that are the antiparticles of those making up normal matter – antiquark/quark, positron/electron – a particle and its antiparticle are annihilated on contact, leaving high-energy radiation
curvature of the Universe
the overall curvature of space in the Universe produced by a combination of all its matter and energy – Universe appears to be very close to critical density, aka a “flat” universe
positive curvature
a “closed” Universe – no end point
negative curvature
curvature of space in which parallel lines diverge and the sum of the angles of a triangle is less than 180° – a “saddle-shaped” universe
flat universe
no curvature – expansion slows so much it seems to have stopped – statistical fluctuations in the CMB probe the curvature of the Universe, evidence suggests the universe is _____
cosmological constant
constant introduced into the equations of general relativity by Albert Einstein in an attempt to cancel the predictions of the expanding nature of our Universe – represented by Λ
fate of the universe
measuring redshift v. distance can be used to infer the history of the scale parameter R(t) – extending redshift vs distance curve to great distances shows the universe appears to be accelerating its expansion rate [understand use of standard candle method with Type 1a supernovae for this measurement] – combining CMB measurements and high redshift observations of supernovae suggests that the universe is flat, and composed of 70% ‘dark energy’ and 30% ‘matter’ (which includes 25% ‘dark matter’).
dark energy
a mysterious force that appears to be causing the expansion of the universe to accelerate – 60% of dark matter
critical density
theoretically calculated – if the observed density is greater than the critical density, the Universe will collapse – if it is less, the Universe will infinitely expand
Categories: Astronomy