Question 1

The distance to a particular galaxy is 60 million light years. If you assume Hubble's constant to be 23 km/s/10⁶ ly, then what redshift recession velocity would you expect to measure? A) zero B) 1.4 × 10³ km/s C) 2.6 × 10³ km/s D) 0.38 × 10³ km/s E) None of these is correct.

Accepted Answer

The answer of The distance to a particular galaxy is...

Question 2

A classical calculation shows that the critical mass density of the universe is given by where H is the Hubble constant and G is the gravitation constant. If the density is below this value, the universe will expand forever, whereas if it is above this value the universe will eventually stop expanding and collapse. Approximately how many hydrogen atoms per m³ is the critical density equivalent to? A) 4 B) 40 C) 400 D) 4000 E) 40,000

Accepted Answer

The answer of A classical calculation shows that the critical...

Question 3

Redshift measurements of a galaxy yield a recession speed of 1700 km/s. Hubble's constant H is 23-km/s/10⁶ ly. The distance to the galaxy is approximately A) 36 × 10⁶ ly. B) 47 × 10⁶ ly. C) 53 × 10⁶ ly. D) 66 × 10⁶ ly. E) 74 × 10⁶ ly.

Accepted Answer

The answer of Redshift measurements of a galaxy yield a...

Question 4

In the standard model, weak charge is
A) the charge associated with the gravitational force.
B) carried by leptons and quarks.
C) carried by quarks and gluons but not leptons.
D) carried by photons.
E) a property of the W± and the Z particles.

Accepted Answer

The answer of In the standard model, weak charge is
A)...

Question 5

We think that the universe is expanding because
A) the light from distant galaxies is very faint.
B) the light from distant galaxies is very bright.
C) distant galaxies are very small.
D) the light from distant galaxies is blueshifted.
E) the light from distant galaxies is redshifted.

Accepted Answer

The most accepted evidence for the universe expanding is the observation of redshift in the light from distant galaxies. This means that the wavelength of the light is stretched out, indicating that the galaxies are moving away from us. This effect is known as the Doppler shift and is caused by the stretching of space itself as the universe expands.

Question 6

There is evidence that the universe is expanding like a loaf of raisin bread baking in an oven. This means that
A) some clusters of galaxies are not getting farther away from other clusters of galaxies.
B) the expansion looks different from each cluster of galaxies.
C) the expansion looks the same from each cluster of galaxies.
D) we should be able to determine the location of the center of the expansion.
E) the universe will eventually collapse.

Accepted Answer

The evidence suggests that the expansion of the universe looks the same from each cluster of galaxies, which is known as the cosmological principle. Therefore, choice C is the best answer. Option A is incorrect because all clusters of galaxies are getting farther away from one another, not just some of them. Option B is incorrect because the expansion looks the same from each cluster, as mentioned above. Option D is incorrect because there is no center of expansion - rather, the universe is expanding from every point in space. Option E is also incorrect because the expansion may continue indefinitely, rather than collapse.

Question 7

Redshift measurements of a galaxy yield a recession speed of 1000 km/s. Hubble's constant H is 23-km/s/10⁶ ly. The distance to the galaxy is approximately A) 23 × 10⁶ ly. B) 37 × 10⁶ ly. C) 44 × 10⁶ ly. D) 52 × 10⁶ ly. E) 61 × 10⁶ly.

Accepted Answer

The formula for Hubble's law is:
v = Hd
where v is the recession speed, H is Hubble's constant, and d is the distance to the galaxy.
Rearranging the formula gives:
d = v/H 
Substituting the given values, we get:
d = 1000 km/s / (23 km/s/10^6 ly)
Simplifying gives:
d = 43.48 × 10^6 ly ≈ 44 × 10^6 ly
Therefore, the answer is choice C.

Question 8

In the standard model,
A) the fundamental particles are the leptons and quarks.
B) the force carriers are the photon, the W±, the Z particles, and the gluons.
C) every force in nature is due to the strong, electromagnetic, weak, or gravitational force.
D) a particle experiences one of the basic interactions if it carries a charge associated with that interaction.
E) All of these are correct.

Accepted Answer

All of the statements are correct in the standard model. A) Leptons and quarks are the fundamental particles, B) Photon, W±, Z particles, and gluons are force carriers, C) The four fundamental forces in nature are strong, electromagnetic, weak, and gravitational forces, and D) A particle carrying a charge associated with an interaction experiences the interaction.

Question 9

How far is a galaxy from Earth if it is receding from Earth at a speed of 0.1c? A) 3.1 × 10²⁰ m B) 1.3 × 10²² m C) 1.3 × 10²⁵ m D) 3.4 × 10²⁸ m E) 1.3 × 10³⁰ m

Accepted Answer

The speed of recession (0.1c) can be used with Hubble's Law (v = H₀d) to find the distance. Assuming H₀ ≈ 70 km/s/Mpc, the calculation gives a distance of approximately 1.3 × 10²⁵ m.

Question 10

The scientific community now thinks that
A) the universe was formed in an explosion that took place between 10 and 15 billion years ago.
B) new matter is continuously being created in the space between the galaxies.
C) the universe is collapsing.
D) quasars originated in the nucleus of the Milky Way.
E) our Sun is at the center of the universe.

Accepted Answer

The Big Bang theory, widely accepted by the scientific community, suggests that the universe was formed in an explosion that took place between 10 and 15 billion years ago. This theory is supported by various pieces of observational evidence, including the cosmic microwave background radiation and the observed redshifts of distant galaxies. The other choices are not supported by current scientific understanding.

Question 11

Mesons are particles that mediate the strong nuclear force. They are thought to travel at near the speed of light and exist over a distance of $\backsim$1.5 fm between two nucleons in the nucleus. The mass of the mesons is of the order A) 10 MeV/c². B) 150 MeV/c². C) 550 MeV/c². D) 1000 MeV/c². E) 3000 MeV/c².

Accepted Answer

The mass of mesons is approximately between 100 to 200 MeV/c^2, which is closest to option B. The other options are either too low or too high compared to the range of masses of known mesons.

Question 12

Assuming a radial speed of a galaxy to be 100 km/s from us and Hubble's constant to be 23 km/s/10⁶ c · y, how far is the galaxy from us? A) 2300 ly B) 2300 Mly C) 4.3 Mly D) 0.23 Mly E) None of these is correct.

Accepted Answer

We can use Hubble's Law to calculate the distance to the galaxy:

v = H0d

where v is the radial speed, H0 is Hubble's constant, and d is the distance.

Rearranging the equation:

d = v / H0

Substituting the values given:

d = 100 km/s / (23 km/s/10^6 pc)

d = 4.35 Mpc

Converting Mpc to Mly:

d = 14.2 Mly / Mpc

d = 4.35 Mpc x 14.2 Mly/Mpc

d = 61.8 Mly

Therefore, the answer is C) 4.3 Mly.

Question 13

Hubble's law can be interpreted to tell us the approximate
A) angular speed of the Milky Way.
B) temperature of our Sun.
C) force of gravity at any point in space.
D) age of the universe.
E) mass of Earth.

Accepted Answer

Hubble's law tells us that the greater the distance of a galaxy from us, the greater its redshift and therefore the faster it is moving away from us. This allows us to estimate the current rate of expansion of the universe and work backwards to estimate its age. Therefore, (D) age of the universe is the approximate value that can be interpreted from Hubble's law.

Question 14

Hubble's Law relates the speed of a galaxy from its distance to us. If you assume Hubble's constant to be 23 km/s/10⁶ ly, then what is the distance of a galaxy that is traveling at 10% the speed of light away from us? A) It is not possible for a galaxy to travel so fast! B) 1.3 × 10¹⁰ ly C) 1.3 × 10⁹ ly D) 1.3 × 10¹¹ ly E) 1.3 × 10⁸ ly

Accepted Answer

Hubble's Law states that the velocity of a galaxy relative to us is proportional to its distance from us. Mathematically, this can be expressed as v = H0 d, where v is the velocity of the galaxy, d is its distance from us, and H0 is Hubble's constant. We are given H0 as 23 km/s/10^6 ly. To find the distance of a galaxy traveling at 10% the speed of light (which is 0.1c), we first convert H0 to units of km/s/Mpc (megaparsec) by dividing by 3.086 × 10^19 km/Mpc:

H0 = 23 km/s/10^6 ly ÷ 3.086 × 10^19 km/Mpc 
= 0.00745 km/s/Mpc

Now we can use the formula v = H0 d, but we need to convert the velocity to km/s first:

v = 0.1c ÷ 1.609 × 10^6 km/s/c 
= 0.622 × 10^8 km/s

d = v ÷ H0 
= (0.622 × 10^8 km/s) ÷ (0.00745 km/s/Mpc) 
= 8.35 × 10^9 Mpc

Finally, we convert Mpc to ly:

8.35 × 10^9 Mpc × 3.26156 × 10^6 ly/Mpc ≈ 1.3 × 10^19 ly

Therefore, the best choice is C, 1.3 × 10^19 ly.

Question 15

The cosmic background radiation is an important aspect of the Big Bang theory because it
A) shows that evolutionary models of the universe are incorrect.
B) does not show any redshift.
C) could not be produced in the universe as it is now, which suggests that conditions must have been different in the past.
D) discredits Hubble's law.
E) is useful in identifying the locations of important objects in the universe.

Accepted Answer

The cosmic background radiation is thought to be the leftover radiation from the Big Bang itself. The fact that this radiation exists and is relatively uniform throughout the universe supports the theory of the Big Bang. The radiation is also very uniform, which suggests that the universe was very homogeneous at the time it was produced. The fact that the radiation exists suggests that conditions in the universe must have been different in the past, supporting the idea of an explosive beginning.

Question 16

According to Hubble's law, the age of the universe is
A) approximately 6000 years.
B) less than 6000 years.
C) roughly 1 billion years.
D) too great to estimate.
E) between 10 and 15 billion years.

Accepted Answer

Hubble's law states that the universe is expanding, and by measuring the rate of expansion and extrapolating backwards, astronomers have estimated the age of the universe to be between 10 and 15 billion years.

Question 17

In the standard model, as with the leptons, there are 3 generations of quarks u&d, c&s, and t&b). The reason for this is
A) because a baryon contains 3 quarks.
B) because the electric charge of the quarks is +1/3 or -2/3 of e.
C) because each quark has a baryon number of 1/3.
D) all of the above.
E) something we do not yet understand.

Accepted Answer

The answer of In the standard model, as with the...

Question 18

The property of the universe that primarily determines whether the universe will expand forever or eventually stop its expansion and contract is
A) its average abundance of heavy elements.
B) how much of its gas has been converted into stars.
C) its average temperature.
D) its total mass.
E) dependent on the amount of helium in the universe.

Accepted Answer

The total mass of the universe is the primary factor that determines whether the universe will expand forever or eventually stop and contract under the influence of gravity. This is because gravity is a force that is proportional to mass, so the more mass the universe has, the stronger the force of gravity will be, and the more likely it is that the universe will eventually stop its expansion and begin to contract.

Question 19

The cosmic background radiation strongly suggests that
A) the energy radiated from the quasars is redshifted.
B) the universe has always been as it is today.
C) the universe evolved from a cold, rarified state.
D) the universe evolved from a hot, uniform state.
E) matter is continuously being created.

Accepted Answer

The cosmic background radiation, which is a remnant of the hot, dense state of the early universe, strongly suggests that the universe evolved from a hot, uniform state. This is known as the Big Bang theory, which is currently the most widely accepted cosmological model.

Quiz 28: Particle Physics

The distance to a particular galaxy is 60 million light years. If you assume Hubble's constant to be 23 km/s/10⁶ ly, then what redshift recession velocity would you expect to measure?

Redshift measurements of a galaxy yield a recession speed of 1700 km/s. Hubble's constant H is 23-km/s/10⁶ ly. The distance to the galaxy is approximately

In the standard model, weak charge is

We think that the universe is expanding because

There is evidence that the universe is expanding like a loaf of raisin bread baking in an oven. This means that

Redshift measurements of a galaxy yield a recession speed of 1000 km/s. Hubble's constant H is 23-km/s/10⁶ ly. The distance to the galaxy is approximately

In the standard model,

How far is a galaxy from Earth if it is receding from Earth at a speed of 0.1c?

The scientific community now thinks that

Mesons are particles that mediate the strong nuclear force. They are thought to travel at near the speed of light and exist over a distance of $\backsim$ 1.5 fm between two nucleons in the nucleus. The mass of the mesons is of the order

Assuming a radial speed of a galaxy to be 100 km/s from us and Hubble's constant to be 23 km/s/10⁶ c · y, how far is the galaxy from us?

Hubble's law can be interpreted to tell us the approximate

Hubble's Law relates the speed of a galaxy from its distance to us. If you assume Hubble's constant to be 23 km/s/10⁶ ly, then what is the distance of a galaxy that is traveling at 10% the speed of light away from us?

The cosmic background radiation is an important aspect of the Big Bang theory because it

According to Hubble's law, the age of the universe is

In the standard model, as with the leptons, there are 3 generations of quarks u&d, c&s, and t&b) . The reason for this is

The property of the universe that primarily determines whether the universe will expand forever or eventually stop its expansion and contract is

The cosmic background radiation strongly suggests that