Question 1

Which of the following statements about dark matter is FALSE:

Accepted Answer

Astronomers do not have a good idea of what dark matter is made of. Its nature and composition remain a mystery, although several candidates have been proposed, including weakly interacting massive particles (WIMPs) and axions.

Question 2

The first satellite (spacecraft with instruments) to measure and confirm the cosmic microwave background was the:

Accepted Answer

The COBE (COsmic Background Explorer) satellite was specifically designed to measure and confirm the cosmic microwave background radiation. It was launched in 1989 and provided important data on the nature of the early universe.

Question 3

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

Accepted Answer

The Planck satellite, launched by the European Space Agency (ESA), has provided the most precise measurements of the cosmic microwave background radiation, offering insights into the universe's age, content, and fabric.

Question 4

The two scientists who first discovered the cosmic microwave background radiation were:

Accepted Answer

Penzias and Wilson discovered the cosmic microwave background radiation in 1964 while working at Bell Laboratories.

Question 5

Where in space did the expansion of the universe begin?

Accepted Answer

The expansion of the universe began everywhere at once. This is because the universe itself is expanding, meaning that every point in space is moving away from every other point. This concept is fundamental to the Big Bang theory and cosmology, indicating that there is no central point from which the expansion started.

Question 6

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)?

Accepted Answer

According to the models of the universe discussed in this course, the galaxies move apart because of the expansion of space itself that started with the Big Bang. This expansion is accelerating, as confirmed by observations of distant supernovae, and is described by Hubble's law. The galaxies are not moving through space like objects on a conveyor belt, but are instead carried along with the expanding space. The expansion stretches the light from distant galaxies, making them appear redder than expected, and the rate of expansion can be measured from this redshift. The cause of this accelerating expansion is currently unknown and is one of the biggest mysteries in physics, leading to the need for concepts like dark matter and dark energy to explain it.

Question 7

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, electro-magnetism and

Accepted Answer

The four forces that govern all action in the universe are the strong nuclear force, the weak nuclear force, electro-magnetism and gravity.

Question 8

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

Accepted Answer

The standard model of the Big Bang Theory does explain the expansion of the universe, the presence of the cosmic microwave background, the abundance of helium, and the redshift observed in galaxies. However, it does not fully explain why the temperature of the cosmic microwave background is so uniform across the vast expanse of space, given the limited time for thermal equilibrium to have been established over such large distances. This uniformity is one of the key puzzles that led to the development of the inflationary model of the early universe.

Question 9

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?

Accepted Answer

Measurements of the 3-degree cosmic background radiation have confirmed that the universe is isotropic on the large scale. The cosmic background radiation is the leftover radiation from the Big Bang and is observed to be the same in all directions.

Question 10

According to our modern theories, the geometry of the entire universe (all of space-time) 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?

Accepted Answer

The properties of black holes, particularly their ability to warp space and time around them, have led to the belief that the geometry of the entire universe may be curved or warped. This is in line with Einstein's theory of general relativity, which predicts that gravity can curve the fabric of space-time.

Question 11

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

Accepted Answer

The idea that the properties of the universe are fine-tuned for the existence of intelligent life is known as the anthropic principle. It suggests that if the fundamental constants and laws of nature were even slightly different, then intelligent life would not have emerged in the universe. This explanation is based on the observation that the universe seems to be finely tuned for life, which is difficult to explain otherwise.

Question 12

Some scientists speculate that our universe is not the only universe that exists, but the only one we can gather evidence about. This idea is called

Accepted Answer

The idea that our universe is just one of many and there are multiple parallel universes is known as the multiverse theory.

Question 13

What is the strongest known force in the universe?

Accepted Answer

The strong nuclear force is the strongest known force in the universe. It holds together the nucleus of an atom and is responsible for the binding of protons and neutrons. The other options are also important forces, but they are not as strong as the strong nuclear force.

Question 14

According to the most recent data from satellites making precise measurements of the properties of the cosmic background radiation (CBR),

Accepted Answer

According to the most recent data from satellites, dark energy makes up just under 70% of the density of the universe, making it the most significant constituent of the universe's total mass-energy.

Question 15

The model of the universe that involves an enormous increase of scale during a very short time in the early universe is called:

Accepted Answer

The model of the universe that involves an enormous increase of scale during a very short time in the early universe is called the inflationary universe model. This idea proposes that the universe went through a period of exponential expansion, called cosmic inflation, shortly after the Big Bang. This expansion amplified quantum fluctuations, producing the large-scale structures that we observe in the universe today.

Question 16

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?

Accepted Answer

During inflation, the universe rapidly expanded, smoothing out any curvature that may have existed before. This expansion was so rapid and extreme that it essentially stretched the universe into a flat shape, which is why we observe a flat geometry today.

Question 17

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:

Accepted Answer

The best choice would be a satellite with infrared and microwave telescopes on board as these wavelengths of light are ideal for studying the cosmic microwave background radiation, which is the afterglow of the Big Bang that can provide information on the conditions in the early universe. Gamma-ray or high-energy x-ray telescopes would not be useful for this purpose, and a small visible light refractor or an ultra-violet telescope would not be sensitive enough to detect the faint signals from the cosmic microwave background radiation. A tank of chlorine deep inside the Earth would also not be relevant for studying the early universe.

Question 18

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?

Accepted Answer

According to our textbook, roughly 95% of the mass and energy contents of the universe is made up of dark matter plus dark energy.

Question 19

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?

Accepted Answer

It took a few hundred thousand years after the beginning for the universe to become cool enough for neutral atoms to form. This is known as recombination and is the point at which the cosmic microwave background radiation was released. Choice A is incorrect because it is an exaggerated time frame for recombination to occur. Choice B is also incorrect as it is too soon after the Big Bang. Choice D is incorrect because it is much later than the actual time for recombination. Choice E is a humorous option and does not provide a scientific answer.

Quiz 29: The Big Bang