Question 1

Gravitational lensing occurs when ________ distorts the fabric of spacetime.

Accepted Answer

A)  a star 
B)  dark matter 
C)  a black hole 
D)  any massive object 
E)  a white dwarf 
A)  a star 
B)  dark matter 
C)  a black hole 
D)  any massive object 
E)  a white dwarf D

Question 2

If the Sun suddenly turned into a black hole, what would be the radius of its event horizon?

Accepted Answer

A)  3 m 
B)  30 m 
C)  300 m 
D)  3 km 
E)  30 km 
A)  3 m 
B)  30 m 
C)  300 m 
D)  3 km 
E)  30 km D

Question 3

What is the meaning of the phrase inertial frame of reference?

Accepted Answer

A)  a reference frame that is not accelerating 
B)  a reference frame that is stationary with respect to Earth 
C)  a reference frame that is rotating at constant speed 
D)  a reference frame that is accelerating at a constant rate 
E)  a reference frame in which there are strong gravitational forces 
A)  a reference frame that is not accelerating 
B)  a reference frame that is stationary with respect to Earth 
C)  a reference frame that is rotating at constant speed 
D)  a reference frame that is accelerating at a constant rate 
E)  a reference frame in which there are strong gravitational forces A

Question 4

The Sun's mass would affect the spacetime in its nearby space and photons from distant stars would follow curved geodesics rather than straight paths when passing close to our star, as in the figure shown below.According to general relativity, an observer on Earth would also expect the "apparent stars" to appear

Accepted Answer

A)  farther apart. 
B)  hotter. 
C)  closer together. 
D)  brighter. 
E)  more massive. 
A)  farther apart. 
B)  hotter. 
C)  closer together. 
D)  brighter. 
E)  more massive.

Question 5

In an accelerator, a massive particle may gain a relativistic speed for which its total energy is 1,000 times greater than its rest energy.This implies a Lorentz factor of

Accepted Answer

A) 0.999. 
B) 10. 
C) 1. 
D) 1,000. 
A) 0.999. 
B) 10. 
C) 1. 
D) 1,000.

Question 6

Suppose you were to travel to the brightest star in Earth's sky, Sirius, 8.6 light-years away, in a spaceship that traveled very close to the speed of light, so that the trip there took only a week for you.During the trip, though, your friends back on Earth would say that around ________ had passed.

Accepted Answer

A)  1 week 
B)  8.6 weeks 
C)  17.2 weeks 
D)  4.3 years 
E)  8.6 years 
A)  1 week 
B)  8.6 weeks 
C)  17.2 weeks 
D)  4.3 years 
E)  8.6 years

Question 7

According to the theory of general relativity, a clock on top of Mount Everest would run ________ compared with a clock at sea level because ________.

Accepted Answer

A)  faster; of the high altitude, which means a slightly weaker gravity 
B)  faster; the air is a lot thinner and there is less friction within the clock 
C)  faster; it is closer to the Moon and thus experiences stronger tidal forces 
D)  slower; of the low pressure at that altitude 
E)  identically; time is the same for all clocks in the universe 
A)  faster; of the high altitude, which means a slightly weaker gravity 
B)  faster; the air is a lot thinner and there is less friction within the clock 
C)  faster; it is closer to the Moon and thus experiences stronger tidal forces 
D)  slower; of the low pressure at that altitude 
E)  identically; time is the same for all clocks in the universe

Question 8

Use the figure shown below to estimate the relative velocity at which relativistic effects become important.Be sure to explain and justify your reasoning.

Accepted Answer

The figure shows the Lorentz factor as a

Question 9

Explain why no object that has mass can ever move at a speed equal to the speed of light.At what velocity do massless particles (e.g., photons) travel in vacuum?

Accepted Answer

According to relativity,increasing the s

Question 10

To travel at a tenth the speed of light (0.1c), a spacecraft carrying humans would require

Accepted Answer

A)  little effort. 
B)  technology that does not yet exist. 
C)  human physiology to evolve further, first. 
D)  an enormous amount of energy. 
E)  a way to protect the humans from being crushed by length contraction. 
A)  little effort. 
B)  technology that does not yet exist. 
C)  human physiology to evolve further, first. 
D)  an enormous amount of energy. 
E)  a way to protect the humans from being crushed by length contraction.

Question 11

For a fast (hypothetical) interstellar ship moving at v = 0.95c relative to stars, a distance of 10 ly between neighboring stars would measure

Accepted Answer

A)  32 ly. 
B)  10.5 ly. 
C)  3.1 ly. 
D)  9.5 ly. 
E)  10 ly. 
A)  32 ly. 
B)  10.5 ly. 
C)  3.1 ly. 
D)  9.5 ly. 
E)  10 ly.

Question 12

If you were to fall to within the event horizon of a black hole, you would

Accepted Answer

A)  never be able to escape. 
B)  get stuck at that location forever. 
C)  get burned up by Hawking radiation. 
D)  not be able to see light. 
E)  be destroyed instantly. 
A)  never be able to escape. 
B)  get stuck at that location forever. 
C)  get burned up by Hawking radiation. 
D)  not be able to see light. 
E)  be destroyed instantly.

Question 13

Explain why measuring Hawking radiation may not be a practical way to observe black holes.

Accepted Answer

The Hawking radiation produced by a blac

Question 14

At what (relativistic) speed does the length of a spacecraft become half of its rest length?

Accepted Answer

A)  0.40c 
B)  0.27c 
C)  0.99c 
D)  0.87c 
E)  0.10c 
A)  0.40c 
B)  0.27c 
C)  0.99c 
D)  0.87c 
E)  0.10c

Question 15

A geodesic is the name for

Accepted Answer

A)  the aberration of starlight. 
B)  one of Earth's magnetic field lines. 
C)  the solid crust of a terrestrial planet. 
D)  the path followed by a freely falling object in spacetime. 
E)  the shape of a body that has mass. 
A)  the aberration of starlight. 
B)  one of Earth's magnetic field lines. 
C)  the solid crust of a terrestrial planet. 
D)  the path followed by a freely falling object in spacetime. 
E)  the shape of a body that has mass.

Question 16

Even if a black hole emitted no light, we can still detect it

Accepted Answer

A)  from sound waves produced by material falling onto the black hole. 
B)  by tides produced on Earth's oceans. 
C)  through its Hawking radiation. 
D)  through its gravitational effect on surrounding gas or stars. 
E)  by looking for dark patches on the sky where the black hole swallows background light. 
A)  from sound waves produced by material falling onto the black hole. 
B)  by tides produced on Earth's oceans. 
C)  through its Hawking radiation. 
D)  through its gravitational effect on surrounding gas or stars. 
E)  by looking for dark patches on the sky where the black hole swallows background light.

Question 17

Which of the following applications could not have been achieved without implementing necessary relativistic effects and corrections?

Accepted Answer

A)  fast-moving automobiles 
B)  GPS technology 
C)  interstellar travel 
D)  radio technology 
E)  neutrino detectors 
A)  fast-moving automobiles 
B)  GPS technology 
C)  interstellar travel 
D)  radio technology 
E)  neutrino detectors

Question 18

Black holes that are stellar remnants can be found by searching for

Accepted Answer

A)  dark regions at the centers of galaxies. 
B)  variable X-ray sources. 
C)  extremely luminous infrared objects. 
D)  objects with very faint radio emission. 
E)  regular, repeated pulsations at radio wavelengths. 
A)  dark regions at the centers of galaxies. 
B)  variable X-ray sources. 
C)  extremely luminous infrared objects. 
D)  objects with very faint radio emission. 
E)  regular, repeated pulsations at radio wavelengths.

Question 19

A person falling into a 1 MSUN black hole (BH) would be "spaghettified." What does this mean and why does it happen?

Accepted Answer

The human body cannot withstand the extr

Question 20

In an accelerator, a massive particle may gain a relativistic speed for which its total energy is 1,000 times greater than its rest energy.This implies a Lorentz factor of

Accepted Answer

A) 0.999. 
B) 10. 
C) 1. 
D) 1,000. 
A) 0.999. 
B) 10. 
C) 1. 
D) 1,000.

Exam 18: Relativity and Black Holes

Gravitational lensing occurs when ________ distorts the fabric of spacetime.

If the Sun suddenly turned into a black hole, what would be the radius of its event horizon?

What is the meaning of the phrase inertial frame of reference?

In an accelerator, a massive particle may gain a relativistic speed for which its total energy is 1,000 times greater than its rest energy.This implies a Lorentz factor of

According to the theory of general relativity, a clock on top of Mount Everest would run ________ compared with a clock at sea level because ________.

Use the figure shown below to estimate the relative velocity at which relativistic effects become important.Be sure to explain and justify your reasoning.

Explain why no object that has mass can ever move at a speed equal to the speed of light.At what velocity do massless particles (e.g., photons) travel in vacuum?

To travel at a tenth the speed of light (0.1c), a spacecraft carrying humans would require

For a fast (hypothetical) interstellar ship moving at v = 0.95c relative to stars, a distance of 10 ly between neighboring stars would measure

If you were to fall to within the event horizon of a black hole, you would

Explain why measuring Hawking radiation may not be a practical way to observe black holes.

At what (relativistic) speed does the length of a spacecraft become half of its rest length?

A geodesic is the name for

Even if a black hole emitted no light, we can still detect it

Which of the following applications could not have been achieved without implementing necessary relativistic effects and corrections?

Black holes that are stellar remnants can be found by searching for

A person falling into a 1 MSUN black hole (BH) would be "spaghettified." What does this mean and why does it happen?

In an accelerator, a massive particle may gain a relativistic speed for which its total energy is 1,000 times greater than its rest energy.This implies a Lorentz factor of

Thinking Like an Astronomer

Patterns in the Skymotions of Earth and the Moon

Motion of Astronomical Bodies

Gravity and Orbits

Light

The Tools of the Astronomer

The Formation of Planetary Systems

The Terrestrial Planets and Earths Moon

Atmospheres of the Terrestrial Planets

Worlds of Gas and Liquidthe Giant Planets

Planetary Moons and Rings

Dwarf Planets and Small Solar System Bodies

Taking the Measure of Stars

Our Starthe Sun

The Interstellar Medium and Star Formation

Evolution of Low-Mass Stars

Evolution of High-Mass Stars

Galaxies

The Milky Waya Normal Spiral Galaxy

The Expanding Universe

Cosmology

Large-Scale Structure in the Universe

Life

Filters

According to the theory of general relativity, a clock on top of Mount Everest would run compared with a clock at sea level because .

A person falling into a 1 M_SUN black hole (BH) would be "spaghettified." What does this mean and why does it happen?