astronomy - the universe

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 measurement of galaxy distances using Type Ia supernovae b. the discovery of large amounts of dark matter in the halo of the Milky Way c. the measurements of cepheid variables in the galaxies of the Local Group d. the measurements of the amount of deuterium in the universe

a

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

a

What is meant in cosmology by "critical density"? a. The density that determines whether the Universe expands forever or re-collapses. b. The density needed to create the Universe. c. The density of galaxies in rich clusters that prevents then escaping. d. The density needed to make a quark.

a

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: [To answer this, think about the role an increase in density (and thus gravity) has on the expansion of the universe] a. less than the critical density b. essentially equal to zero (density is super low) c. exactly equal to the critical density d. so great that the universe will experience a "big crunch" before the Sun becomes a red giant e. more than the critical density

b

How many galaxies show a red-shift? a. only a few of the most distant galaxies b. nearly all of them c. only the galaxies closest to us d. zero

b

If the universe were decelerating, our calculated age of the universe would be: a. greater than 1/H b. less than 1/H c. equal to 1/H d. there is no way to know

b

The rate of expansion of the universe is? a. constant b. accelerating c. zero d. decelerating

b

Today, we believe that only a small number of elements were actually formed during the Big Bang. Which of the following was NOT one of these: a. lithium b. carbon c. hydrogen d. you can't fool me, all of the above were definitely formed during the big bang e. helium

b

What have scientists suggested is causing the Universe to expand faster? a. Antimatter b. Dark Energy c. Baryonic Matter d. Dark Matter

b

Where in space did the expansion of the universe begin? a. at a point so far away that only our largest telescopes can show us glimpses of it b. everywhere at once c. at the center of the Milky Way Galaxy; that's why all the other galaxies are moving away from us d. nowhere at all; new observations show that the universe is not expanding after all e. near the center of the Virgo Supercluster of Galaxies

b

Which of the following did NOT happen during the first few minutes after the Big Bang? a. temperatures throughout the universe were hotter than the cores of stars are today b. some very massive early stars formed c. matter and antimatter collided and turned into energy d. two or three of the simplest elements fused together e. energy was converted to matter

b

At first, right after the Big Bang, the universe was too hot for nuclei and electrons to combine into the kinds of neutral atoms that are familiar to us today. How soon after the beginning did it become cool enough for neutral atoms to form? (i.e. nucleons with electrons, not just the nucleons) a. 10^-43 seconds b. 3 minutes c. a few hundred thousand years d. a billion years

c

Hubble's law indicates that... a. The universe is expanding. b. The universe must have had a beginning. c. All of these. d. Nearly all other galaxies are moving away from us. e. None of these.

c

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 red-shift? a. astronomers cannot think of any good explanation for the red-shift if it's space that expands/stretches b. as time goes on, waves in space encounter more and more dust, and get redder c. as space stretches, the waves of radiation in space also stretch and their wavelength increases d. as space stretches, the presence of dark matter slows down the light between galaxies e. as galaxies age, they get redder and redder

c

In the very distant future, given our best model of the accelerating universe, what will the universe look like? a. the entire universe will become one huge black hole b. galaxies will shine even more brightly than today from all the dark energy c. all the stars will die and the galaxies will be dark d. all the galaxies will start showing blue-shifts e. the universe will look pretty much the same as it does today

c

The objects that made it possible for astronomers to discover the acceleration in the expansion of the universe were a. Cepheid variable stars b. the brightest irregular galaxy in a rich cluster c. Type Ia supernovae d. globular clusters

c

What created the Cosmic Microwave Background, or CMB? a. Pieces of space dust from the moon b. Radio waves sent from other universes c. Heat left over from the Big Bang d. Ultraviolet light from our Sun

c

What does a larger red-shift indicate? a. The galaxy has more stars b. The star is about to explode in a supernova c. The galaxy is moving away faster d. The star is older

c

What is the present best estimate of Hubble's constant? a. ~72 km/s/Mpc b. ~50 km/s/Mpc c. ~70 km/s/Mpc d. ~100 km/s/Mpc

c

When we determine the age of the universe using the Hubble Time, what important simplifying assumption goes into our calculations? a. that the universe is actually contracting instead of expanding b. the universe is not isotropic and homogeneous c. that the expansion of the universe has been happening at the same rate - neither speeding up or slowing down d. that we have accounted correctly for the effects of dark energy

c

Why is the CMB so cool now? a. The cosmological constant has "squashed" its wavelengths and cooled it. b. Hydrogen atoms have condensed on it and chilled it. c. The expansion of the Universe has cooled the radiation and stretched its wavelengths d. Dense clouds of dust have blocked most of it.

c

According to the models of the universe we discussed in this course, why do the galaxies move apart (why do we have Hubble's law)? a. gravity is a repulsive force, once you get outside the Milky Way Galaxy b. each galaxy has net charge on it, and they repel by the laws of electricity c. supernova explosions happen more frequently on one side of each galaxy, giving the entire galaxy a push that moves it away from its neighbors d. as a result of the Big Bang, space itself is stretching, and this stretching carries the galaxies away from each other

d

According to the most recent data from satellites making precise measurements of the properties of the cosmic microwave background, a. normal matter (like the atoms in our bodies) makes up 99% of the total mass-energy of the universe b. normal matter, dark matter, and dark energy each contribute about 1/3 of the total density of the universe - their contributions are almost exactly equal c. dark matter makes up less than 5% of the total mass-energy of the universe; it's only a minor contributor to what makes up the cosmos d. the dark energy makes up just a little less than 70% of the density of the universe, making it the most significant constituent of the mass-energy

d

After the Big Bang, in order for the universe to become transparent to light and other electro-magnetic radiation, what had to happen? a. stars and galaxies had to form b. the whole universe had to be hotter than the interior of a star c. the dark energy had to dominate over regular matter and energy d. the density of the universe had to decrease (to 1000 nuclei per cubic centimeter or less)

d

How do we think our Universe will end? a. A lonely freeze... b. A big freeze! c. A big crunch! d. A big rip!

d

The cosmic microwave background is sometimes referred to as "relic radiation" -- light left over from a truly ancient time. But it isn't a relic of the universe's first moments, of the hot plasma posited by theorists; instead, it's thought to come from about 380,000 years after the very beginning, just after an epoch called "recombination." What happened during this time period? a. The first stars ignited. b. Matter began coalescing into stars. c. Light atomic nuclei, like helium and lithium, formed. d. Neutral hydrogen and helium atoms formed.

d

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

d

Which of the following is pretty good evidence that the universe began with a Big Bang? a. the fact that stars explode b. the fact that all the galaxies are moving toward us c. the existence of a double star system like Cygnus X-1 d. the 3-degree cosmic microwave background radiation e. the fact that galaxies collide

d

Which of the following is the Earth not located in? a. the universe b. the solar system c. the Milky Way Galaxy d. globular cluster M-13

d

Which of the following statements about dark matter is FALSE: a. we can detect its gravity, even though we can't see it b. it is observed to be present in other groups of galaxies c. it is observed to be a major part of the Milky Way d. astronomers have a pretty good idea what the dark matter is made of e. it may make up even more of the universe that the matter we can see

d

Which of the following statements about the early universe (as envisioned by the standard model of cosmology) is FALSE? a. at the beginning, the universe was not transparent to electro-magnetic radiation b. as the universe expands, its temperature decreases c. at the beginning, the temperature was hot enough to turn energy into matter d. at the very beginning, the energies were so great that the universe was actually contracting for a while e. at the very beginning, anti-matter (as well as matter) was present in significant quantities

d

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

e

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 small refractor (which gathers visible light) on a college campus, but pointed in just the right direction b. a tank of chlorine deep inside the Earth c. a gamma-ray or high-energy x-ray telescope in orbit d. an ultra-violet telescope in orbit around Jupiter e. a satellite with infrared and microwave telescopes on board

e