Question 1

You have a 1 kg mass at rest sitting on a lab bench in front of you. You see somebody fly by in a spaceship traveling at 0.2c. That astronaut flying by also has a 1 kg mass sitting on a bench in front of her. She would measure that mass to be 1kg.

Accepted Answer

According to the theory of relativity, an observer in a spaceship moving at a constant velocity relative to an observer on the lab bench would measure the same mass as the observer on the bench. Therefore, the astronaut would measure the 1 kg mass to be 1 kg as well.

Question 2

The singularity of a black hole has an infinitely small radius, but its event horizon is finite.

Accepted Answer

The singularity of a black hole is a point of infinite density and zero volume, which means it has an infinitely small radius. However, the event horizon, which is the boundary beyond which nothing can escape from the gravitational pull of the black hole, has a finite radius. This means that anything that gets closer to the event horizon will eventually be pulled into the black hole and trapped forever.

Question 3

We can't detect the gravitational redshift coming from the Sun because the Sun has a very small amount of gravity.

Accepted Answer

This statement is incorrect. The Sun has a significant amount of gravity and gravitational redshift can be observed in the light coming from the Sun. In fact, this effect was first observed by Arthur Eddington during a solar eclipse in 1919.

Question 4

What would happen if mass were continually added to a 2M _$\odot$ neutron star?

Accepted Answer

Neutron stars have a maximum mass limit, known as the Tolman-Oppenheimer-Volkoff (TOV) limit. If mass is continually added to the neutron star, it may eventually exceed this limit and collapse to become a black hole.

Question 5

What will observers in different inertial frames of reference always agree on?

Accepted Answer

The results of physics experiments performed in each frame will always be the same, regardless of the frame of reference. This is a fundamental principle of the theory of relativity, and is known as the principle of relativity. It means that the laws of physics are the same in all inertial frames of reference, and that all observers will agree on the results of physics experiments, as long as those experiments are conducted in a truly inertial frame.

Question 6

Einstein's special theory of relativity implies that if a person standing at the front of a train traveling at 0.1 km/s shines a flashlight out in front of the train, the emitted photons will travel at a speed of 300,000.1 km/s.

Accepted Answer

According to Einstein's special theory of relativity, the speed of light is constant for all observers, regardless of their relative motion. Therefore, the emitted photons will still travel at a speed of 300,000 km/s, regardless of the speed of the train.

Question 7

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

Accepted Answer

An inertial frame of reference is a reference frame in which a body that is at rest or moving with constant velocity experiences no acceleration. In other words, it is a non-accelerating reference frame.

Question 8

Gravitational lensing allows us to see distant objects brightened and distorted because of massive objects in the path that the light from the object travels.

Accepted Answer

Gravitational lensing is a well-known phenomenon in astronomy that occurs due to the bending of light by massive objects like galaxies and clusters of galaxies. The light from distant objects like quasars, supernovas, and galaxies gets deflected and distorted as it passes through the gravitational field around these massive objects. This allows astronomers to observe distant and faint objects that would otherwise be invisible or too faint to detect. Therefore, the statement is true.

Question 9

One result of relativity is that an astronaut in a windowless spacecraft could tell the difference between falling freely and the presence of a nearby gravitational source.

Accepted Answer

According to the equivalence principle in general relativity, an astronaut in a windowless spacecraft cannot distinguish between free-fall in a gravitational field and being in deep space without gravity.

Question 10

You observe a distant galaxy apparently moving away at 1/3 the speed of light (v =c/3). If you could measure the speed that this galaxy's light is passing the Earth, you would get:

Accepted Answer

The speed of light is constant in all inertial frames, so the speed that the galaxy's light is passing the Earth is still c, regardless of the galaxy's apparent velocity.

Question 11

The aberration of starlight is:

Accepted Answer

The aberration of starlight is the apparent shift in the direction of starlight as observed from Earth due to the Earth's orbital motion around the sun. This effect was first explained by James Bradley in 1725.

Question 12

Special relativity says that moving clocks run slower.

Accepted Answer

Special relativity predicts that clocks moving relative to an observer will appear to run slower than stationary clocks in that observer's reference frame. This phenomenon is known as time dilation.

Question 13

The Earth orbits the Sun because the Sun changes space around it but not time.

Accepted Answer

The Earth orbits the Sun because the Sun's mass curves both space and time around it, according to Einstein's theory of general relativity. This curvature affects the path of the Earth, causing it to orbit the Sun.

Question 14

A black hole can be produced if the stellar core left over after a supernova is larger than 3 M _$\odot$ .

Accepted Answer

This is true. A black hole can be produced if the stellar core left over after a supernova is larger than 3 solar masses (3MF). The exact threshold for black hole formation is believed to be around 3.2-3.5 solar masses.

Question 15

Gamma-ray bursts are probably associated with extremely energetic supernova explosions.

Accepted Answer

This is currently the leading theory for the origin of gamma-ray bursts. It is believed that the collapse of a massive star and the subsequent explosion as a supernova can release enough energy to produce a gamma-ray burst. However, the exact mechanisms behind this process are still being studied and researched.

Question 16

Gravity is nothing more than a curvature in the fabric of spacetime.

Accepted Answer

This is the theory of general relativity proposed by Albert Einstein in 1915, which explains gravity as a result of the curvature of spacetime caused by the presence of massive objects.

Question 17

Special relativity says that all observers moving at constant speed will measure the same value of the speed of light.

Accepted Answer

This is one of the fundamental principles of special relativity, known as the constancy of the speed of light. No matter how fast an observer is moving, they will always measure the speed of light to be the same value, approximately 299,792,458 meters per second.

Question 18

Black holes emit no light whatsoever.

Accepted Answer

Black holes themselves do not emit light, but the material around them, such as the accretion disk, can emit light and other forms of radiation.

Question 19

The mass of an atomic nucleus is a measure of how much energy is contained therein.

Accepted Answer

The mass of an atomic nucleus is related to its binding energy and therefore, the amount of energy contained in the nucleus. This is known as mass-energy equivalence, as described by Einstein's famous equation E=mc². Therefore, option A is correct.

Question 20

The Sun could turn into a black hole at the end of its life.

Accepted Answer

The Sun is not massive enough to turn into a black hole at the end of its life. Instead, it will become a red giant and then eventually shed its outer layers and become a white dwarf.

Quiz 18: Relativity and Black Holes

You have a 1 kg mass at rest sitting on a lab bench in front of you. You see somebody fly by in a spaceship traveling at 0.2c. That astronaut flying by also has a 1 kg mass sitting on a bench in front of her. She would measure that mass to be 1kg.

The singularity of a black hole has an infinitely small radius, but its event horizon is finite.

We can't detect the gravitational redshift coming from the Sun because the Sun has a very small amount of gravity.

What would happen if mass were continually added to a 2M _$\odot$ neutron star?

What will observers in different inertial frames of reference always agree on?

Einstein's special theory of relativity implies that if a person standing at the front of a train traveling at 0.1 km/s shines a flashlight out in front of the train, the emitted photons will travel at a speed of 300,000.1 km/s.

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

Gravitational lensing allows us to see distant objects brightened and distorted because of massive objects in the path that the light from the object travels.

One result of relativity is that an astronaut in a windowless spacecraft could tell the difference between falling freely and the presence of a nearby gravitational source.

You observe a distant galaxy apparently moving away at 1/3 the speed of light (v =c/3) . If you could measure the speed that this galaxy's light is passing the Earth, you would get:

The aberration of starlight is:

Special relativity says that moving clocks run slower.

The Earth orbits the Sun because the Sun changes space around it but not time.

A black hole can be produced if the stellar core left over after a supernova is larger than 3 M _$\odot$ .

Gamma-ray bursts are probably associated with extremely energetic supernova explosions.

Gravity is nothing more than a curvature in the fabric of spacetime.

Special relativity says that all observers moving at constant speed will measure the same value of the speed of light.

Black holes emit no light whatsoever.

The mass of an atomic nucleus is a measure of how much energy is contained therein.

The Sun could turn into a black hole at the end of its life.

Quiz 18: Relativity and Black Holes

You have a 1 kg mass at rest sitting on a lab bench in front of you. You see somebody fly by in a spaceship traveling at 0.2c. That astronaut flying by also has a 1 kg mass sitting on a bench in front of her. She would measure that mass to be 1kg.

The singularity of a black hole has an infinitely small radius, but its event horizon is finite.

We can't detect the gravitational redshift coming from the Sun because the Sun has a very small amount of gravity.

What would happen if mass were continually added to a 2M ⊙\odot⊙ neutron star?

What will observers in different inertial frames of reference always agree on?

Einstein's special theory of relativity implies that if a person standing at the front of a train traveling at 0.1 km/s shines a flashlight out in front of the train, the emitted photons will travel at a speed of 300,000.1 km/s.

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

Gravitational lensing allows us to see distant objects brightened and distorted because of massive objects in the path that the light from the object travels.

One result of relativity is that an astronaut in a windowless spacecraft could tell the difference between falling freely and the presence of a nearby gravitational source.

You observe a distant galaxy apparently moving away at 1/3 the speed of light (v =c/3) . If you could measure the speed that this galaxy's light is passing the Earth, you would get:

The aberration of starlight is:

Special relativity says that moving clocks run slower.

The Earth orbits the Sun because the Sun changes space around it but not time.

A black hole can be produced if the stellar core left over after a supernova is larger than 3 M ⊙\odot⊙ .

Gamma-ray bursts are probably associated with extremely energetic supernova explosions.

Gravity is nothing more than a curvature in the fabric of spacetime.

Special relativity says that all observers moving at constant speed will measure the same value of the speed of light.

Black holes emit no light whatsoever.

The mass of an atomic nucleus is a measure of how much energy is contained therein.

The Sun could turn into a black hole at the end of its life.

What would happen if mass were continually added to a 2M _$\odot$ neutron star?

A black hole can be produced if the stellar core left over after a supernova is larger than 3 M _$\odot$ .