Astro 123 quizzes post midterm 2

In the current epoch, roughly what percent of the mass and energy contents of the universe is made up of ordinary (atomic) matter? a. 5 percent b. 10 percent c. 50 percent d. 95 percent e. astronomers have no way of estimating this percentage

a.

When we determine the age of the universe using the Hubble Time (1/H0), what important simplifying assumption goes into our calculations? a. that the expansion of the universe has been happening at the same rate - neither speeding up or slowing down b. that all the galaxies are moving away from us at exactly the same speed, no matter how far away they are c. that the cosmological principle doesn't hold: the universe is not isotropic and homogeneous d. that we have accounted correctly for the effects of dark energy e. that the universe is actually contracting instead of expanding

a.

Based on many surveys of the average density of matter and energy in the universe, astronomers now conclude that the average density of the universe is a. less than the critical density b. exactly equal to the critical density c. more than the critical density d. essentially equal to zero e. so great that the universe will experience a "big crunch" before the Sun becomes a red giant

b.

Based on many surveys of the average density of matter in the universe (regular matter and dark matter), astronomers now conclude that the average density of the universe is a. less than the critical density b. exactly equal to the critical density c. more than the critical density d. essentially equal to zero e. so great that the universe will experience a "big crunch" before the Sun becomes a red giant

b.

How does a period of extremely fast inflation very early in the history of the universe explain the observation that the geometry of the universe looks flat (not curved) to us? a. during inflation a lot of the mass drained out of the universe, leaving its gravity much weaker b. inflation increased the size of the universe so much that the resulting universe looks flat from any point of view c. inflation led to the production of so much dark matter that the universe got pulled into the shape of a black hole d. inflation caused the temperature of different parts of the universe that can't see each other still be the same e. The universe is actually highly curved and not flat

b.

If the universe consisted only of matter and its density were equal to critical, the universe would a. continue expanding, then slow down and contract, ending in a "big crunch" b. continue expanding, eventually slowing down to zero c. continue expanding, eventually speeding up d. continue expanding at a reduced rate e. not expand at all

b.

In our modern view of the expansion of the universe, we understand that it is space that is stretching; individual galaxies don't speed away from each other as if they were rockets. In that case, why do galaxies show a redshift? a. as galaxies age, they get redder and redder b. as space stretches, the waves of radiation in space also stretch and their wavelength increases c. as space stretches, the presence of dark matter slows down the light between galaxies d. as time goes on, waves in space encounter more and more dust, and get redder e. astronomers cannot think of any good explanation for the red-shift if it's space that expands/stretches

b.

In our modern view of the expansion of the universe, we understand that it is space that is stretching; individual galaxies don't speed away from each other as if they were rockets. In that case, why do galaxies show a redshift? a. as galaxies age, they get redder and redder b. as space stretches, the waves of radiation in space also stretch and their wavelength increases c. as space stretches, the presence of dark matter slows down the light between galaxies d. as time goes on, waves in space encounter more and more dust, and get redder e. astronomers cannot think of any good explanation for the redshift if it's space that expands/stretches

b.

Recent observations indicate that the universe is expanding faster today than it was a few billion years ago (that, in other words, the expansion of the universe is accelerating.) What kind of observations have led astronomers to this surprising conclusion? a. the measurements of cepheid variables in the galaxies of the Local Group b. the measurement of galaxy distances using Type Ia supernovae c. the discovery of large amounts of dark matter in the halo of the Milky Way d. the measurements of the amount of deuterium in the universe e. the fact that galaxies today are getting a lot more speeding tickets than they used to

b.

Why did Einstein introduce the cosmological constant into the equations of his General Theory of Relativity when describing the universe? a. Einstein did not realize that black holes would exist at the centers of galaxies and pull everything into them b. Einstein's equations required the universe to expand or contract; he could not imagine or accept it doing either one, so he put a factor in to stop it from moving c. Einstein talked to Hubble and learned about Hubble's observations of the expanding universe, which made him so uncomfortable that he decided to change his equations d. Einstein had a hunch that the universe was accelerating (speeding up its expansion) back in 1918 and so introduced the constant into his equations to describe that e. Einstein liked cups of tea in the afternoon, and his constant was a comment on that habit

b.

In describing the universe using his equations of general relativity, Einstein assumed that it was isotropic (the same in all directions.) What recent observations have confirmed that the universe is isotropic on the large scale? a. the discovery of pulsars b. the discovery of cannibal galaxies c. measurements of the cosmic microwave background radiation d. measurements of neutrinos from Supernova 1987A e. the discovery that there is really nothing very good on TV, no matter which way you point your dish (antenna)

c.

The reciprocal of the Hubble constant (1/H0) is a rough measure of the: a. the period of a typical Cepheid variable b. the distance to the last galaxies that formed c. the age of the universe d. the luminosity of a type I supernova explosion e. the cost of building a telescope in space

c.

Factoring in everything we currently know about the history of the universe, our best estimate for the age of the universe is a. 4.6 billion years b. about 100 billion years c. roughly 2 million years d. about 13.8 billion years e. the age of the universe is infinite; there was no beginning

d.

Measurements of the cosmic microwave background provide strong evidence that the overall geometry of space is a. trapezoidal b. spherical, or positive curvature c. hyperbolic, or negative curvature d. flat, or zero curvature e. circular

d.

Roughly what percent of the mass and energy contents of the universe is made up of dark matter plus dark energy? a. 5 percent b. 10 percent c. 50 percent d. 95 percent e. astronomers have no way of estimating this percentage

d.

The model of the universe that involves an enormous increase of size during a very short time in the early universe is called: a. the flat universe model b. the oscillating universe model c. the primeval atom model d. the inflationary universe model e. the cosmic burp model

d.

The redshift observed in the light emitted by distant galaxies is due to a. the Doppler shift of the galaxies moving away from us through a fixed space b. the Doppler shift of the galaxies moving towards us through a fixed space c. the gravitational redshift of the galaxies' immense mass d. the expansion of space e. radio-bright quasars

d.

When do astronomers now think that the "dark energy" began to accelerate the expansion of the universe? a. right after the Big Bang (after the first three minutes or so) b. a few million years after the Big Bang c. 380,000 years after the Big Bang d. a few billion years ago e. about a billion years in the future

d.

If you want to check on what conditions were like in the universe a few hundred thousand years after the Big Bang, what sort of instrument would it be best to use: a. a gamma-ray or high-energy x-ray telescope in orbit b. a tank of chlorine deep inside the Earth c. a small refractor (which gathers visible light) on a college campus, but pointed in just the right direction d. an ultra-violet telescope in orbit around Jupiter e. a satellite with infrared and microwave telescopes on board

e.