Exam 18: Relativity and Black Holes

While traveling the galaxy in a spacecraft, you and a colleague set out to investigate the 10⁶M _$\odot$ black hole at the center of our galaxy. She hops aboard an escape pod and drops into a circular orbit around the black hole, maintaining a distance of 4 *10⁶ km, while you remain much farther away in the spacecraft. After doing some experiments to measure the strength of gravity, your colleague signals her results back to you using a green laser. What would you see? Hint: you will need to calculate the location of the event horizon.

Gamma-ray bursts are likely to be:

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.

What is the "rubber sheet" analogy for spacetime, and why is it useful for explaining gravity and gravitational waves?

A geodesic is the name for:

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?

What is the Lorentz factor for an object moving at 0.85c?

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

How would the Newtonian theory explain the orbit of the Earth around the Sun? What would the explanation be in general relativity?

Describe two early verifications of the prediction of relativity.

Explain what four-dimensional spacetime means.

The bending of light passing near a massive object is called:

How does relativity compare to Newtonian physics?

The gravitational redshift of light should be smallest for light emitted from the surface of:

You measure that an object has a mass of exactly 1 kg by weighing it in the Earth's gravitational field. The equivalence principle says that the mass you would measure by trying to accelerate it would be:

If the Earth were to shrink in size until it became a black hole, its Schwarzschild radius would be:

The twin paradox shows that special relativity:

Light is increasingly redshifted near a black hole because:

What is the difference between the singularity and the event horizon of a black hole?

Compared to a clock on the surface of the Earth, a clock on the International Space Station runs: