Introductory Astronomy: Chapter 18

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

scattered across approx. uniformly – therefore, universe is approx. the same in all directions with no apparent center

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

13.7 billion years old

we appear to be at the center, however, the Universe is expanding no matter where you are located within it

on sufficiently large scales, the universe is homogenous and isotropic – matter is evenly distributed

the argument that the darkness of the night sky conflicts with the assumption of an infinite and eternal static universe

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

leftover thermal energy from the Big Bang – radiation is visible in all directions – has a temperature of 2.73 K

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!

young Universe was extremely hot – mix of gas and radiation

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

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

a “closed” Universe – no end point

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

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 _____

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

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’).

a mysterious force that appears to be causing the expansion of the universe to accelerate – 60% of dark matter

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