The Universe

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 satellite with infrared and microwave telescopes on board

Where in space did the expansion of the universe begin?

everywhere at once

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 few hundred thousand years

Factoring in everything we currently know about the history of the universe, our best estimate for the age of the universe is

about 13.8 billion years

In the very distant future, given our best model of the accelerating universe, what will the universe look like?

all the stars will die and the galaxies will be dark

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)?

as a result of the Big Bang, space itself is stretching, and this stretching carries the galaxies away from each other

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?

as space stretches, the waves of radiation in space also stretch and their wavelength increases

Which of the following statements about the early universe (as envisioned by the standard model of cosmology) is TRUE?

as the universe expands, its temperature decreases at the beginning, the temperature was hot enough to turn energy into matter at the beginning, the universe was not transparent to electromagnetic radiation at the very beginning, anti-matter (as well as matter) was present in significant quantities

Which of the following did happen during the first few minutes after the Big Bang?

energy was converted to matter matter and antimatter collided and turned into energy two or three of the simplest elements fused together temperatures throughout the universe were hotter than the cores of stars are today

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)

essentially equal to zero (density is super low)

Today, we believe that only a small number of elements were actually formed during the Big Bang. Which of the following was one of these:

hydrogen helium lithium

Which of the following statements about dark matter is TRUE

it may make up even more of the universe that the matter we can see it is observed to be present in other groups of galaxies we can detect its gravity, even though we can't see it it is observed to be a major part of the Milky Way

If the universe were decelerating, our calculated age of the universe would be

less than 1/H

When do astronomers now think that the "dark energy" began to accelerate the expansion of the universe?

several billion years after the Big Bang

When we determine the age of the universe using the Hubble Time, what important simplifying assumption goes into our calculations?

that the expansion of the universe has been happening at the same rate - neither speeding up or slowing down

Which of the following is pretty good evidence that the universe began with a Big Bang?

the 3-degree cosmic microwave background radiation

The reciprocal of the Hubble constant (1/H) is a rough measure of the:

the age of the universe

According to the most recent data from satellites making precise measurements of the properties of the cosmic microwave background,

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

After the Big Bang, in order for the universe to become transparent to light and other electro-magnetic radiation, what had to happen?

the density of the universe had to decrease (to 1000 nuclei per cubic centimeter or less)

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?

the measurement of galaxy distances using Type Ia supernovae

Which of the following is the Earth located in?

the universe the Milky Way galaxy the solar system (NOT globular cluster M-13)

The objects that made it possible for astronomers to discover the acceleration in the expansion of the universe were

type la supernovae