Deck 14: Down the Rabbit Hole: Relativity and Black Holes

Question 1

How did physicists try to detect the luminiferous aether in the late 19th century?

A) by measuring the rate at which it produced light
B) by measuring its refractive properties
C) by measuring its density
D) by measuring its relative velocity to Earth

Answer 1

by measuring its relative velocity to Earth

Question 2

Two observers in different frames of reference will measure different:

A) laws of physics.
B) values for the speed of light.
C) values for the speed of material objects.
D) values for Newton's gravitational constant.

Answer 2

values for the speed of material objects.

Question 3

An airline pilot spends a considerable fraction of his life traveling at a speed of several hundred kilometers per hour relative to his identical twin brother.How does the pilot's lifetime compare to that of his brother,all other things being equal?

A) The pilot's is slightly longer.
B) The pilot's is slightly shorter.
C) The pilot's is much longer.
D) The pilot's is much shorter.

Answer 3

The pilot's is slightly longer.

Question 4

The general theory of relativity includes an explanation of:

A) the four fundamental forces.
B) gravity and space-time.
C) quantum mechanics and gravity.
D) light waves and photons.

Question 5

Light waves emitted from a laser at rest will travel at a speed c relative to:

A) the Sun.
B) a laboratory in Paris.
C) the cosmic microwave background.
D) all of the above.

Question 6

A spaceship moves at 3/5 the speed of light relative to an observer.How long will each tick of a clock on the spaceship take,relative to an identical clock held by the observer?

A) 3/5 as long
B) just as long
C) 5/4 as long
D) 5/3 as long

Question 7

If the speed of light were infinite,how would black holes change?

A) They would have to be more massive.
B) They would have to be denser.
C) They would be easier to observe.
D) They would not exist.

Question 8

Two observers travel perpendicular to each other,as shown in the figure below.If observer B shone a light toward observer A,what velocity would observer A measure the beam to have?

A) c
B) 0.84 c
C) 0.66 c
D) 0.5 c

Question 9

How do the laws of physics change for moving observers?

A) Kinetic energies are always larger for moving observers.
B) The Doppler effect is stronger for moving observers.
C) Gravity is weaker for moving observers.
D) None of the laws change.

Question 10

Einstein showed that Newton's physics is:

A) wrong.
B) accurate only at low masses.
C) accurate only at large distances.
D) accurate only at low velocities.

Question 11

Gravitational waves are:

A) observed during planetary conjunctions.
B) responsible for periodic orbits.
C) ripples in the fabric of space-time.
D) only produced by supermassive black holes.

Question 12

Imagine that a spaceship is traveling at half the speed of light relative to an observer.The spaceship shoots a laser in the direction of its motion.How fast is the laser traveling relative to the observer?

A) half the speed of light
B) the speed of light
C) 1.5 times the speed of light
D) 2 times the speed of light

Question 13

Imagine that a child is inside a car traveling at 8 m/s.The child throws a ball with a velocity of 1 m/s in the direction of the car's motion.How fast is the ball traveling relative to an observer at rest on the side of the road?

A) 1 m/s
B) 8 m/s
C) 9 m/s
D) 10 m/s

Question 14

Experiments to measure the properties of the luminiferous aether were problematic for scientists in the early 20th century because there was no evidence for:

A) the motion of observers relative to the aether.
B) absorption as light traveled through the aether.
C) emission of light from the aether.
D) gravitational effects of the aether.

Question 15

What is invariant between different frames of reference?

A) the kinetic energy of an object
B) the law of gravity
C) the speed of an object
D) all of the above

Question 16

What remnant will a star with an initial total mass of 100 M_sun leave at the end of its life?

A) black hole
B) neutron star
C) white dwarf
D) brown dwarf

Question 17

The first experimental verification of the general theory of relativity was:

A) gravitational waves.
B) gravitational lensing.
C) time dilation.
D) the detection of black holes.

Question 18

Which of the following did Einstein determine to be a constant of nature?

A) the speed of a photon
B) the gravitational force of a proton
C) the mass of a proton
D) Newton's gravitational constant

Question 19

A muon is a type of subatomic particle.If a muon is at rest in the laboratory,it will decay into an electron after about 2 microseconds.Suppose an observer watches a muon travel through the atmosphere at 90 percent of the speed of light.How does the lifetime of the moving muon compare to the laboratory muon,for an observer at rest with respect to the lab?

A) It is shorter.
B) It is longer.
C) It is the same.
D) It cannot be determined with the given information.

Question 20

What are black holes?

A) the densest regions in the Universe
B) regions from whose gravity nothing can escape
C) the most massive objects in the Universe
D) all of the above

Question 21

According to the general theory of relativity,what is the internal structure of a black hole?

A) a constant density inside the event horizon
B) nearly empty inside the event horizon, with a singularity at the center
C) increasing density inside the event horizon, with a singularity at the center
D) a ring of high density material at the event horizon

Question 22

A galaxy is positioned precisely behind another,very massive,galaxy on the sky.We would observe the more distant galaxy as a:

A) ring, displaced from the galaxy's true location.
B) pair of identical images, displaced from its true location.
C) single magnified image, at its true location.
D) single magnified image, displaced from its true location.

Question 23

Why is the Schwarzschild radius significant?

A) It is the distance within which space-time breaks down.
B) It is the distance within which nothing can escape a black hole.
C) It is the distance within which gravitational lensing is strong.
D) It is the distance within which the black hole's tidal forces are strong.

Question 24

What kind of stars are most likely to form black holes?

A) stars that can only initiate hydrogen and helium fusion
B) stars with low-mass cores
C) stars with masses greater than 30 MSun
D) stars with an overabundance of heavy elements

Question 25

According to the general theory of relativity,a satellite orbits Earth because:

A) Earth has deformed space around it, so the satellite is trapped in a circular well.
B) Earth has deformed space-time in such a way that the satellite falls freely through it.
C) the spinning Earth's frame of reference drags the satellite with it.
D) Earth has deformed space around it, so the satellite's frame of reference rotates.

Question 26

Which of the following effects must be accounted for to make accurate measurements with global positioning system satellites?

A) light travel times
B) special relativity
C) gravity
D) all of the above

Question 27

Which of the following objects has the strongest tidal forces,assuming that each has the same mass?

A) black hole
B) white dwarf
C) neutron star
D) the Sun

Question 28

What does the "no-hair" theorem state?

A) Black hole formation cannot be observed.
B) Nothing can escape a black hole.
C) Black holes can be described by just three numbers.
D) Black holes can only be observed through gravitational lensing.

Question 29

A black hole,originally with a mass of 10³ MSᵤn,accretes gas and grows so that its event horizon increases in radius by a factor of 10.What is the final mass of the black hole?

A) 10⁶ M_Sun
B) 10⁵ M_Sun
C) 10⁴ M_Sun
D) 10³ M_Sun

Question 30

Which of the following sets of numbers completely characterizes a black hole?

A) mass, electric charge, radius
B) mass, temperature, radius
C) mass, angular momentum, temperature
D) mass, spin, electric charge

Question 31

A laser falls into a black hole,but it continues to emit light directly away from the black hole as it does so.How does the light appear to a distant observer as the laser gets closer to the black hole?

A) The light appears to slow down.
B) The light becomes redder.
C) The light begins to orbit the black hole.
D) The light becomes brighter.

Question 32

According to the general theory of relativity,gravity:

A) affects all forms of energy.
B) is a warping of space-time.
C) is equivalent to a different frame of reference.
D) all of the above.

Question 33

Cosmic censorship is the idea that:

A) naked singularities are impossible.
B) black holes evaporate.
C) black holes cannot form.
D) black holes do not radiate.

Question 34

A set of stars all initially have the same mass of 20 MSᵤn,but their other properties differ.Which is LEAST likely to form a black hole at the end of its life?

A) the most luminous star
B) the star that transfers most of its mass to a binary companion
C) the star with the most heavy elements
D) the star with the weakest stellar winds

Question 35

What stops the collapse of the most massive stars at the end of their lives?

A) nothing
B) electron degeneracy pressure
C) neutron degeneracy pressure
D) gamma-ray bursts

Question 36

Muons created by cosmic rays in Earth's atmosphere survive much longer than those created in the laboratory.This is because of:

A) the uncertainty principle.
B) the randomness of half-lives.
C) relativistic time dilation.
D) the properties of cosmic rays.

Question 37

Suppose a supermassive black hole moves across the line of sight to a distant star,as shown in the figure below.How will the star appear to change to an observer on Earth?

A) The star's light will be trapped by the black hole, and we will not see it.
B) The star's light will become bluer.
C) The star's light will become redder.
D) We will see multiple images of the star.

Question 38

Why is quantum mechanics necessary for resolving the puzzle of a black hole's singularity?

A) It implies that space is granular on the smallest scales.
B) It is necessary for very massive systems.
C) It is necessary to explain the gravitational redshift.
D) It is a necessary component of stellar collapse.

Question 39

A star sits directly behind a black hole relative to the observer,as shown in the figure below.An observer will perceive it as a ________ the black hole.

A) single point, just behind
B) single point, offset from
C) pair of points, on either side of
D) circle surrounding

Question 40

Black hole A has a mass of 10³ MSᵤn,while black hole B has a mass equal to the Sun's.How large is the Schwarzschild radius of black hole A,relative to that of black hole B?

A) 10 times as large
B) 100 times as large
C) 10³ times as large
D) 10⁶ times as large

Question 41

Which of the following is essential for galactic jets?

A) a starburst
B) strong magnetic fields
C) a molecular cloud
D) an elliptical galaxy

Question 42

Two galaxies are shown in the image below.The central,nearly round object is nearby,while the ring-like object is actually positioned immediately behind the central galaxy.Why do we perceive the latter as a ring?

Question 43

In the late 19th century,how did scientists explain the wavelike properties of light?

Question 44

The first evidence for supermassive black holes at the centers of galaxies came from:

A) gravitational lensing.
B) their effects on nearby stars.
C) their light output.
D) galactic winds.

Question 45

According to the special theory of relativity,the duration between events depends upon the frame of reference in which those events are measured.In order to maintain a constant speed of light,what else must change between frames of reference?

Question 46

The figure below shows an observer and two light sources.How much faster does light from A appear to be moving for the observer than light from B?

Question 47

Does gravitational lensing occur in Newton's formulation of gravity? Why or why not?

Question 48

From the perspective of an observer near a black hole,which of the following appears to happen as he or she observes large distances from the black hole?

A) Distant objects appear to move toward the black hole.
B) Distant objects appear redder than they should.
C) Distant clocks tick more rapidly than the observer's clock.
D) Distant objects appear to "freeze" in time.

Question 49

Astronomers discover a bright X-ray source in the Milky Way.They see no counterpart in the optical bands,but it has another star orbiting it,and they determine that the X-ray source has a mass of 10 MSᵤn.What is the most likely origin of the X-rays?

A) a black hole
B) a neutron star
C) a white dwarf
D) a gamma-ray burst

Question 50

An accretion disk around a black hole is threaded by magnetic fields.What is a likely result of this configuration?

A) a jet of material moving near the speed of light
B) the breakup of the accretion disk
C) a reversal in the orbits of material in the accretion disk
D) bright optical emission from the accretion disk

Question 51

A stellar-mass black hole is accreting gas from a nearby O star in an X-ray binary.How does the peak wavelength of the system's X-ray emission change over time as this mass is transferred?

A) It decreases, because the star loses mass.
B) It decreases, because the black hole gains mass.
C) It increases, because the star loses mass.
D) It increases, because the black hole gains mass.

Question 52

A disk of gas orbits a supermassive black hole.What can astronomers use to determine the mass of the black hole from the properties of this disk?

A) Wien's law
B) the Doppler shift
C) Polarization
D) the Stefan-Boltzmann law

Question 53

In which wavelength range is material falling into stellar-mass black holes most likely to be detected?

A) optical
B) X-ray
C) infrared
D) none; they do not emit light

Question 54

What do astronomers believe exists in the center of nearly every galaxy?

A) a gamma-ray burst
B) a massive dust cloud
C) a star-forming region
D) a black hole

Question 55

Why do the most massive stars leave black hole remnants after they die?

Question 56

Three identical clocks are held by observers moving as shown in the figure below.Compare the rates at which the three clocks tick,as measured by observer B.

Question 57

What is the observational evidence that black hole jets are launched very close to the event horizon?

A) the narrowness of the jet
B) gravitational lensing by the black hole
C) the relativistic speeds of the jet
D) imaging of the accretion disk

Question 58

How do matter-energy and space-time affect each other,according to general relativity?

Question 59

What are the two fundamental postulates of special relativity?

Question 60

Two twins are separated at birth.One lives on a massive gas giant,while the other lives on a spaceship far from any stars.All other things being equal,which twin lives longer? Why?

Question 61

What kind of objects exhibit the strongest frame-dragging effects?

Question 62

An astronaut falls into a black hole that has 100 times the mass of the Sun.The astronaut sends signals to her partner,who sits at rest a large distance from the black hole.How far from the black hole's center is the astronaut when her signals can no longer reach her partner?

Question 63

The figure below shows a relativistic jet of material escaping an astronomical object.The jet is represented by the twisted gray columns.What is represented by the twisted lines and orange disk? What is at the center of such a system?

Question 64

What produces the X-rays in an X-ray binary?

Question 65

What are the three observable properties of black holes?

Question 66

How would Earth's orbit change if the Sun suddenly collapsed into a black hole (with the same mass as it currently has)?

Question 67

Most astronomers believe that stars that end their lives as black holes do not usually produce strong supernova explosions,unlike those that produce neutron stars.Why?

Question 68

Where do supermassive black holes typically live?

Question 69

Why does the existence of a singularity at the center of a black hole challenge the general theory of relativity?

Question 70

What is the event horizon of a black hole?