Final homework

According to our textbook, roughly what percent of the mass and energy contents of the universe is made up of dark matter plus dark energy?

95 percent

Why did Einstein introduce the cosmological constant into the equations of his General Theory of Relativity when describing the universe?

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

Scientists looking at an overview of physics today understand that there are four forces that govern all action in the universe. These four forces are the strong nuclear force, the weak nuclear force, electromagnetism and

Gravity

The satellite that has given us the most precise measurements of the characteristics of the cosmic background radiation is:

Planck

The standard bulbs (standard candles) that made it possible for astronomers to discover the acceleration in the expansion of the universe were

Type Ia supernovae

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

age of the universe

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

Scientists speculate that the properties (laws) of the universe must be the way they are because if they were significantly different, we would not be here to think about them. This idea is called

anthropic principle

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 (or, more precisely, spacetime) that is stretching; individual galaxies don't speed away from each other as if they were rockets. In this view, why do galaxies show a redshift?

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 FALSE?

at the very beginning, the energies were so great that the universe was actually contracting for a while

Where in space did the expansion of the universe begin?

everywhere at once

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?

measurements of the 3-degree cosmic background radiation

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

several billion years after the Big Bang

Which of the following did NOT happen during the first few minutes after the Big Bang?

some very massive early stars formed

What is the strongest known force in the universe?

strong nuclear force

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

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

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

Astronomers have measured that there is more helium in the universe than can be explained by the fusion in stars over the last 13 billion years. How do they think the extra helium got into the universe?

the extra helium was made during the first few minutes of the Big Bang, when the entire universe was hot enough for fusion to occur briefly

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

According to our modern theories, the geometry of the entire universe (all of spacetime) may be curved or warped. This is a pretty bizarre notion; what other discovery in astronomy has helped us believe that space may be able to curve or warp?

the properties of black holes

One of the things that our current "standard model" of the Big Bang Theory doesn't explain is

why the temperature of the cosmic microwave background is so uniform throughout all of space