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Signal Beacon approaching Black Hole

  • #1
In the interest of science you give your roommate a flashing light signal beacon and toss him/her into a supermassive galactic black hole. Describe what you see as you observe the fall from far away, stationary relative to the black hole. Explain your reasoning in each of the following questions.

a. What happens to the apparent timing and color of the signal beacon as your roommate approaches the event horizon?

A: The signal beacon flashes less frequently as he approaches the event horizon and is blue shifted?

b. How fast does your roommate seem to be traveling as he/she approaches the horizon?

A: ???

c. How does the brightness of the image vary with time?

A: The brightness decreases over time?
 

Answers and Replies

  • #2
In the interest of science you give your roommate a flashing light signal beacon and toss him/her into a supermassive galactic black hole. Describe what you see as you observe the fall from far away, stationary relative to the black hole. Explain your reasoning in each of the following questions.

a. What happens to the apparent timing and color of the signal beacon as your roommate approaches the event horizon?

A: The signal beacon would appear to arrive slower than before and the light from the beacon would be red shifted because he is moving away from me faster and faster.

b. How fast does your roommate seem to be traveling as he/she approaches the horizon?

A: He would be moving faster and faster the closer he got to the event horizon because he would be affected by the gravitational pull of the black hole.

c. How does the brightness of the image vary with time?

A: The brightness decreases over time until he passed the event horizon and then no light would reach you ever again.

Do these answers seem correct?
 
  • #3
tiny-tim
Science Advisor
Homework Helper
25,789
249
Welcome to PF!

Hi waterboy613 Welcome to PF! :smile:

a. You haven't said anything about how gravity affects the beacon.

b. You haven't asnwered the question … it asks how fast does he seem to be travelling.

c. Half-right … from what point in time (your time) would "no light would reach you ever again?

Re-read your notes about black holes, and then try again … and remember, the question asks you "what you see". :smile:
 

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