Astronomy Chapter 26 Vocab- "Cosmology"

Sloan Great Wall

the largest structure known in the universe

pencil-beam survey

a measure of large-scale structure that is up to about 200-300 Mpc in size

homogeneous

consisting of parts or elements that are all the same

isotropic

the same in all directions

Olbers’s paradox

the contradiction to the theory that if the universe is homogeneous, isotropic, infinite, and unchanging, the entire sky should be as bright as the surface of the Sun; it contradicts since the night sky is obviously dark

Big Bang

an important event in space that happened around the time the universe formed (around 13.7 billion years ago); a single point in this event was where all galaxies were seen to originate

expand forever or collapse

the two known possibilities for the universe in the future, assuming that the only relevant force is gravity

asymptotical zero

when the expansion speed of the universe basically approaches zero infinitely close but never gets there

closed (leads to ultimate collapse), flat (corresponds to the density), and open (will expand forever)

the three possibilities for the universe’s overall structure

cosmological constant (vacuum energy)

the variable introduced by Einstein to prevent general relativity from predicting that a static universe (then thought to be the case) would collapse

cosmic microwave background (CMB)

was fortuitously created in 1964 when two researchers tried to get rid of the last bit of “noise” in their radio antenna; this “noise” was actually detecting photons left over from the Big Bang