Question 1

A cube falls into a black hole with one flat side aimed directly for the hole. What happens to the dimensions of the cube?

Accepted Answer

As the cube approaches the black hole, the nearer points experience a much stronger gravitational force than the further points, causing a distortion in all three dimensions. This effect is known as spaghettification, where objects are stretched into long thin shapes resembling noodles. So, all the dimensions of the cube will be distorted.

Question 2

If you were watching a friend (or better still, an enemy!) who has fallen as far as the event horizon of a black hole, what would you measure as his heartbeat (apart from effects caused by his adrenaline level)?

Accepted Answer

An observer at a safe distance watching someone who has fallen into a black hole would see their motion slow down and eventually stop at the event horizon due to time dilation. From the perspective of the outside observer, time runs slower closer to the black hole due to the intense gravitational field. Therefore, the person's heartbeat would appear to slow down and eventually stop completely at the event horizon, causing it to appear as if their heart had stopped.

Question 3

Black holes with which of the following masses are most likely to have evaporated within the lifetime of our universe?

Accepted Answer

Black holes with very low mass, such as those with a mass about that of Mount Everest, are most likely to have evaporated within the lifetime of our universe due to Hawking radiation, a quantum mechanical process that causes black holes to lose mass over time.

Question 4

The age of the universe is roughly 14 billion years, which is also the approximate evaporation time for a black hole with a mass of 10¹⁰ kg. What is the Schwarzschild radius of such a black hole?

Accepted Answer

The evaporation time for a black hole is proportional to the cube of its mass, and inversely proportional to the square of its Schwarzschild radius. Using this formula, we can find the Schwarzschild radius for a black hole with an evaporation time of 14 billion years and a mass of 10^110 solar masses:

t = (5120πG^2M^3)/(ℏc^4)

where t is the evaporation time, G is the gravitational constant, M is the mass of the black hole, ℏ is the reduced Planck constant, and c is the speed of light.

Solving for the Schwarzschild radius yields:

r = (2GM/c^2) = (2ℏc/GM)^(1/2)

Plugging in the values for t and M, we get:

r = 1.5 × 10^-17 m

Therefore, the answer is B.

Question 5

How are antiparticles and virtual particles related?

Accepted Answer

Virtual particle pairs include both a particle and its corresponding antiparticle, but not all antiparticles are virtual particles and not all virtual particles occur in pairs with their corresponding antiparticle.

Question 6

The black hole at the center of the Milky Way Galaxy is estimated to have a mass of roughly 4 million M_ε. What is the TEMPERATURE of this black hole (that is, the temperature of a blackbody with an equivalent energy emission)?

Accepted Answer

Black holes, according to the theory of general relativity, do not emit light or any form of electromagnetic radiation under normal circumstances, making them effectively at a temperature that is essentially absolute zero in terms of observable radiation. The concept of temperature here refers to the black body radiation that a black hole could theoretically emit, known as Hawking radiation, which is so minimal for a black hole of such mass that it would be indistinguishable from absolute zero in practical observations.

Question 7

If you look for electrons emitted from the vicinity of black holes, you will:

Accepted Answer

The correct answer is based on Hawking radiation, a theoretical prediction that black holes can emit radiation due to quantum effects near the event horizon. Smaller black holes have a higher temperature and emit more radiation, including electrons, than larger ones.

Quiz 21: Stellar Remnants: Neutron Stars and Black Holes

A cube falls into a black hole with one flat side aimed directly for the hole. What happens to the dimensions of the cube?

If you were watching a friend (or better still, an enemy!) who has fallen as far as the event horizon of a black hole, what would you measure as his heartbeat (apart from effects caused by his adrenaline level) ?

Black holes with which of the following masses are most likely to have evaporated within the lifetime of our universe?

The age of the universe is roughly 14 billion years, which is also the approximate evaporation time for a black hole with a mass of 10¹⁰ kg. What is the Schwarzschild radius of such a black hole?

How are antiparticles and virtual particles related?

The black hole at the center of the Milky Way Galaxy is estimated to have a mass of roughly 4 million M_ε. What is the TEMPERATURE of this black hole (that is, the temperature of a blackbody with an equivalent energy emission) ?

If you look for electrons emitted from the vicinity of black holes, you will:

Quiz 21: Stellar Remnants: Neutron Stars and Black Holes

A cube falls into a black hole with one flat side aimed directly for the hole. What happens to the dimensions of the cube?

If you were watching a friend (or better still, an enemy!) who has fallen as far as the event horizon of a black hole, what would you measure as his heartbeat (apart from effects caused by his adrenaline level) ?

Black holes with which of the following masses are most likely to have evaporated within the lifetime of our universe?

The age of the universe is roughly 14 billion years, which is also the approximate evaporation time for a black hole with a mass of 1010 kg. What is the Schwarzschild radius of such a black hole?

How are antiparticles and virtual particles related?

The black hole at the center of the Milky Way Galaxy is estimated to have a mass of roughly 4 million Mε. What is the TEMPERATURE of this black hole (that is, the temperature of a blackbody with an equivalent energy emission) ?

If you look for electrons emitted from the vicinity of black holes, you will:

The age of the universe is roughly 14 billion years, which is also the approximate evaporation time for a black hole with a mass of 10¹⁰ kg. What is the Schwarzschild radius of such a black hole?

The black hole at the center of the Milky Way Galaxy is estimated to have a mass of roughly 4 million M_ε. What is the TEMPERATURE of this black hole (that is, the temperature of a blackbody with an equivalent energy emission) ?