Astronomy Unit 10

Question 1

idea that physical laws must be the way they are because otherwise we could not be here
to measure them

Answer 1

anthropic principle

Question 2

the theory of cosmology in which the expansion of the universe began with a primeval explosion (of
space, time, matter, and energy)

Answer 2

Big Bang

Question 3

a model in which the universe expands from a Big Bang, stops, and then contracts to a big
crunch

Answer 3

closed universe

Question 4

microwave radiation coming from all directions that is the redshifted afterglow of the Big Bang

Answer 4

cosmic microwave background (CMB)

Question 5

the term in the equations of general relativity that represents a repulsive force in the
universe

Answer 5

cosmological constant

Question 6

he study of the organization and evolution of the universe

Answer 6

cosmology

Question 7

in cosmology, the density that is just sufficient to bring the expansion of the universe to a stop
after infinite time

Answer 7

critical destiny

Question 8

the energy that is causing the expansion of the universe to accelerate; its existence is inferred
from observations of distant supernovae

Answer 8

dark energy

Question 9

nonluminous material, whose nature we don’t yet understand, but whose presence can be
inferred because of its gravitational influence on luminous matter

Answer 9

dark matte

Question 10

a form of hydrogen in which the nucleus of each atom consists of one proton and one neutron

Answer 10

deuterium.

Question 11

a model of the universe that has a critical density and in which the geometry of the universe is
flat, like a sheet of paper

Answer 11

flat universe

Question 12

the building of heavier atomic nuclei from lighter ones

Answer 12

fusion

Question 13

physical theories that attempt to describe the four forces of nature as different
manifestations of a single force

Answer 13

grand unified theories

Question 14

a theory of cosmology in which the universe is assumed to have undergone a phase of
very rapid expansion when the universe was about 10–35 second old; after this period of rapid expansion, the standard Big Bang and inflationary models are identical

Answer 14

inflationary universe

Question 15

the third element in the periodic table; lithium nuclei with three protons and four neutrons were
manufactured during the first few minutes of the expansion of the universe

Answer 15

lithium

Question 16

the speculative idea that our universe is just one of many universes, each with its own set of
physical laws

Answer 16

multiverse

Question 17

a model in which the density of the universe is not high enough to bring the expansion of the
universe to a halt

Answer 17

open universe

Question 18

when radiation began to stream freely through the universe without interacting with
matter

Answer 18

photon decoupling time

Question 19

(WIMPs) weakly interacting massive particles are one of the candidates for the composition of dark matter

Answer 19

weakly interacting massive particles