Space, Reflection: See Earth's Past in Mirror?

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Discussion Overview

The discussion explores the theoretical possibility of using a mirror in space to capture images of Earth, specifically whether such an arrangement could allow one to see reflections of the past. The scope includes conceptual reasoning and speculative applications of light travel time.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant proposes the idea of placing a mirror in space to photograph Earth's reflection and see it in the past.
  • Another participant argues that even without a mirror, there is a natural delay in perception due to the time it takes for light to travel, exemplified by the time delay when observing a fly landing on a table.
  • A different participant suggests that while a mirror could theoretically introduce additional lag, the practical limits would only allow for a tiny fraction of a second of delay.
  • One participant humorously notes that if a mirror were already in place, it could potentially reflect images from three seconds in the past.
  • Another reiterates the original question about using a mirror in space and mentions that a bathroom mirror provides a delay of about ten nanoseconds.

Areas of Agreement / Disagreement

Participants express varying views on the feasibility of using mirrors to see the past, with no consensus reached. Some focus on the theoretical aspects, while others highlight practical limitations.

Contextual Notes

The discussion includes assumptions about the setup time for mirrors in space and the inherent delays in light travel, which may not be fully resolved or quantified.

Who May Find This Useful

Individuals interested in theoretical physics, the nature of light, and concepts of time perception may find this discussion relevant.

atarah
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TL;DR
can you theoretically put a mirror in space, take a photo of earth/dirts reflection and see it in the past?
can you theoretically put a mirror in space, take a photo of earth/dirts reflection and see it in the past?
 
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We don’t even need a mirror to produce that effect. When I see a fly land on a table 3 meters away…. The fly actually landed about 10 nanoseconds before I saw it land, because that’s how long it took the light to travel the 3 meters between the table and my eye. The same thing would happen if we were using a camera instead of a human eye to form the image.

And yes, sending the light on a circuitous path with one or more mirrors allows us to introduce yet more lag between event and eye. In practice however, we’re not going to be able to get more than a tiny fraction of a second of additional delay that way.
 
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atarah said:
Summary: can you theoretically put a mirror in space, take a photo of earth/dirts reflection and see it in the past?
Unless the mirror is already there, getting it set up will require so much time that you'll not see any farther into the past than when you launched it.

So if you are planning on getting some long distance images of the grassy knoll at a particular historically relevant moment, you are out of luck.
 
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How about this view? It looked back 3 seconds in history.

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atarah said:
Summary: can you theoretically put a mirror in space, take a photo of earth/dirts reflection and see it in the past?

can you theoretically put a mirror in space, take a photo of earth/dirts reflection and see it in the past?
Your bathroom mirror will give you a delay of ten nanoseconds or so. that would be a start!
 
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