HW 10: Black Holes and Curved Spacetime

According to Einstein’s Special Theory of Relativity (1905), which of the following is a key consequence of observing an object moving near the speed of light?

The object’s length contracts in the direction of motion. 

What are the two main postulates of Einstein's Special Theory of Relativity?

The laws of nature are the same for everyone, and the speed of light is the same for everyone.

What phenomenon describes light waves taking extra time to climb out of a deep hole in spacetime, leading to their wavelength increasing?

Gravitational Redshift 

What happens to tidal forces as an object approaches a black hole?

Tidal forces are lethal near a 3-solar-mass black hole but gentler near a supermassive black hole. 

Gamma-ray bursts, first detected in the 1960s are now known to originate from…

Very distant galaxies, and they are extremely powerful explosions

What was the significance of the LIGO detection on September 14, 2015?

It was the first direct detection of gravitational waves from emerging black holes.

Which of the following is not a test of verification of relativity

Observing the changing phases of the Moon.

Carol is stationary midway between two light bulbs and observes that they turn on at the exact time. You are moving near the speed of light towards the light bulb to Carol’s left. What do you observe?

You observe the light bulb to the left turns on first.

A person watching a train going by says the train is moving 50 km/hr. A person in the train claims the train is not moving. Who is correct?

Both are correct in some sense but should be more specific when describing the motion.

A spaceship is moving past us at a speed close to the speed of light. What would we conclude about time (clocks) on the spaceship as it goes by?

We would conclude that their clocks are going slower than ours.

What did the Michelson-Morley experiment demonstrate?

The speed of light that we observe is not affected by Earth’s motion around the Sun.

The primary difference between the special theory of relativity and the general theory of relativity is that the general theory also describes ____.

The nature of gravity

In relativity, two people share the same reference frame only if they ____.

Are not moving relative to one another.

Precise determination of location via GPS satellite is a practical application of which famous theory?

General theory of relativity

Two twin sisters, Gwen and Jackie, are both 20 years old in the year 2050. Suppose that Jackie makes the round-trip to Vega, which is 25 light-years away, at an average speed of 0.9999 c. Which of the following correctly describes the situation when Jackie returns to Earth? (Ages in this problem refer to biological ages, that is, how much time has passed for each sister since she was born.)

It's the year 2100. Gwen (who stayed home) is 70 years old, but Jackie is only a little older than her age of 20 when she left.

What is the primary reason why scientists accept the idea that the speed of light is the same for everyone?

Because it has been verified by many observations and experiments

Suppose your normal resting heart rate is 60 beats per minute. Now, suppose you board a spaceship that travels away from Earth at 90% of the speed of light. While on the ship, you measure your heart rate. What will it be?

It will still be 60 beats per minute

Suppose you measure the density (mass per volume) of an object moving by you at high speed. How will its density compare to the density it would have at rest in your reference frame?

Its density would be higher

In what way do observations of binary star systems support the special theory of relativity?

The fact that the stars appear distinct supports the idea that the speed of light is unaffected by the motion of the stars.