Understanding the Time Delay in Viewing Events on the Moon with Telescopes

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    Light Time Travel
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Discussion Overview

The discussion revolves around the concept of time delay in observing events on the Moon through telescopes, particularly focusing on how to explain this phenomenon to a young audience. It includes considerations of light travel time, practical demonstrations, and the implications of viewing distant events.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants assert that light takes time to travel, meaning that events observed through a telescope are not seen in real time but rather after a delay, specifically 1.32 seconds for events on the Moon.
  • One participant suggests using a walkie-talkie demonstration to illustrate the concept of wave travel time, comparing the speed of sound to the speed of light.
  • Another participant argues that the path of light does not significantly change, implying that the delay should not be substantial, challenging the common understanding of light travel time.
  • A participant introduces a hypothetical scenario involving an advanced civilization observing events on Earth from 41 light years away, highlighting the difference in perception of time between observers.
  • There is a mention of a "superman" analogy, which did not resonate with one participant's grandson, while the concept of light waves was more effective in explaining the phenomenon.

Areas of Agreement / Disagreement

Participants express differing views on the implications of light travel time and how best to convey these concepts to a young audience. There is no consensus on the most effective explanation or the interpretation of the original question posed by the OP.

Contextual Notes

Some participants highlight the need for practical experience to understand wave travel time, while others question the clarity of the OP's understanding of the concept. The discussion reflects varying levels of familiarity with the physics involved.

Who May Find This Useful

This discussion may be useful for educators, parents, or anyone interested in explaining complex physics concepts to younger audiences, particularly regarding light travel time and observational delays in astronomy.

brentefs@comc
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Imagine an event occurring on the moon that is not visible to the human eye, but with a high powered telescope it is easily viewed. Did the telescope see it happening in real time or did it see the event 1.32 seconds after it occurred. Based on common sense you can imagine it as realtime, but I know better. How can this be explained to a very bright 11 year old.
 
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If you want to take it that way, we see nothing in "real time." Light takes time to travel.

Though you should probably wait for the pros of this forum to answer it since I am a twat.
 
brentefs@comc said:
How can this be explained to a very bright 11 year old.

Take the other person outside to a large field with a pair of walkie-talkies. Get about 100 meters apart. Yell "hello" loudly into the walkie-talkie. The other person will your voice through speaker, and then, after a short delay, hear your voice through the air. Explain that the speed of sound causes a greater delay than the speed of light does. But when people are a quarter of a million miles apart (earth to moon), the delay due to the speed of light is noticable.
 
brentefs@comc said:
Imagine an event occurring on the moon that is not visible to the human eye, but with a high powered telescope it is easily viewed. Did the telescope see it happening in real time or did it see the event 1.32 seconds after it occurred. Based on common sense you can imagine it as realtime, but I know better. How can this be explained to a very bright 11 year old.

What common sense? The only difference in the path the light had to take to get to your retina happened in the last few feet. For the other 239,000 miles, the path was the same. Common sense tells me if there is no substantial difference in the path, there is no substantial difference in the time.
 
mikelepore said:
Take the other person outside to a large field with a pair of walkie-talkies. Get about 100 meters apart. Yell "hello" loudly into the walkie-talkie. The other person will your voice through speaker, and then, after a short delay, hear your voice through the air. Explain that the speed of sound causes a greater delay than the speed of light does. But when people are a quarter of a million miles apart (earth to moon), the delay due to the speed of light is noticable.
That's not what the OP was asking.
 
The telescope has no effect on the time travel , it has just magnified the event for a human eye to view/witness. A superman with an ideal vision can view the event with no need to a telescope


the situation can be rephrased as two stars collide and, we view the event with our naked eyes at the moment when the traveled light hits our eyes , after traveling so many light years

:)
 
If an advanced civilization that's 41 light years away from Earth were to train their hi-power telescope at our moon, they'd see Neil Armstrong taking his first step off his capsule right now; not 41 years ago.

They'd murmur to each other, "The Earthlings just landed on their moon! The Earthlings just landed on their moon!" To us, however, the event took place 41 years ago.
 
russ_watters said:
That's not what the OP was asking.

What does the word "that's" in your post refer to? The OP shows a lack of practical experience with the fact that waves have finite speeds, and the resulting delays. I described an activity that can produce a personal experience with wave travel time. That's how I recommend teaching the concept to an 11-year-old.
 
mikelepore said:
What does the word "that's" in your post refer to? I described an activity that can produce a personal experience with wave travel time.
"That's" means "that is". Ie, "That is not what the OP was asking".
The OP shows a lack of practical experience with the fact that waves have finite speeds, and the resulting delays.
I'm not seeing that. What the logic is in the second case, I'm not sure, but in the first case it is clear that the OP understands that light takes 1.32 seconds to travel the distance from the Earth to the moon.
 
  • #10
Thanks guys or ladies; I must confess that the "superman " idea didn't impress my grandson after I let him read all the answers you were kind enough to suggest. The "light waves" was the one he focused on the most. I was able to get him to understand it for awhile, but he called me this morning, since he thinks grandpa knows everything, and now wants me to explain how a laser works. This, I believe, will be much easier. Thanks again, B.L.
 

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