To see there is easier than to be there

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Discussion Overview

The discussion revolves around the concept of observing the past through reflections in mirrors or other reflective bodies in space. Participants explore the feasibility of using astronomical bodies or artificial mirrors to capture and analyze light from distant objects, considering implications for understanding historical events in the universe.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant suggests that images seen in mirrors represent messages from the past, proposing that reflections from celestial bodies could allow observation of historical events.
  • Another participant questions the practicality of finding a suitable reflective astronomical body, noting that Venus, while bright, does not provide detailed images.
  • There is a proposal to consider artificial mirrors in space, with the idea that a sufficiently large mirror could potentially reflect images of Earth from the past, although this would require advanced technology.
  • A participant inquires about the most distant object from which a radar signal can be received, indicating interest in the limits of current observational capabilities.
  • Further contributions mention that Saturn and its moon Titan are among the most distant objects from which radar signals can be reflected back, allowing for some analysis of past events on Earth based on the time it takes for signals to travel.
  • Discussion includes the potential for observing extremely weak signals from distant sources, with advancements in technology making this increasingly feasible.
  • One participant emphasizes that the question is more about seeing past images rather than time travel, framing it as a fun inquiry.

Areas of Agreement / Disagreement

Participants express a range of ideas about the feasibility of observing the past through reflections, with no consensus on the practicality of using natural versus artificial reflective bodies. The discussion remains open-ended regarding the capabilities of current technology and the potential for future advancements.

Contextual Notes

Participants acknowledge limitations in the current understanding of reflective capabilities in space and the challenges associated with detecting weak signals from distant objects. There is also a recognition of the technological advancements required to make such observations possible.

bothnicum
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Speculum Temporis - a partial solution?

All the pictures you can see in a mirror are messages from the past.

Photons must first travel from the object under survey to the mirror and back to the observer. Your do not think of that in the bathroom. But imagine that the mirror is located at the distance of one light year, the image you could see would be two years old.

If all celestial bodies besides black holes are reflective, at least some of the photons we are detecting by watching the sky, must be reflections from our very own history. By tuning at the distance of N ly's, you could watch direct broadcast of what happened 2N years ago.

This would help us to evaluate where to travel.

I think this could possibly work for some signals in the timeframe of minutes inside our solar system. But could it be possible in the timeframe of years or hundred years for any kind of reflections? What do You think?
 
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Well it's hard to think of an astronomical body that is as good a reflector as a mirror - one that you could see shapes for example. Probably the best reflector in the inner solar system is Venus, and that has the kind of reflectivity of white clouds. Very bright but no detail.


Since natural bodies are not likely to work, let's consider artificial bodies. Could we put a mirror out in space and arrange to see our past in that? Possibly, but it would have to be a very big mirror. Astronomers just recently managed to get an image of a planet of another star. All the other planets have been discovered from their gravitational effects on their stars. The image is just a blob, below the level of real resolution. But suppose future telescopes can do a few orders of magnitude better. Then maybe a planet sized mirror would work. But of course the image would be of Earth as seen from space. We could maybe see how the clouds moved forty years ago but not the people.

Sigh, more technology. Suppose the solve that problem...
 
Yes, it is hard to find an ideal mirror in space.

But let me ask the other way round:

- What is the most distant object in space we can get a radar signal back?
 
I don't know the answer to that. That would be an excellent question to ask on the Astronomy forum.
 
Good work. I'll be talking to you.
 
Nereid answered at General Astronomy & Cosmology -forum:

" AFAIK, Saturn, its rings and moon Titan hold the record:
http://www.aas.org/publications/baa...dps2002/109.htm
http://www.news.cornell.edu/Chronic...ydrocarbon.html

The distance? >1 billion km
"

So it takes 2.25 hours to get a reflected signal back from Titan. By analysing the reflected signal we can conclude (among other things) that someone was experimenting with a high energy radar down on the Earth more than two hours ago. Also if there were, say 5 seconds, black out in the power production system of the sun. We could observe its propagation through the planets so that we could see the black out in Pluto about 10 hours later.

Thus far we can say that yes 'Speculum Temporis' is observable in solar dimensions.

But does it exist in light year range? Why not - but the signal must be extremely weak. We probably must be able to catch single photons. This would have been totally impossible 20 years ago. But today we rapidly approaching that extreme. See for example "A broadband superconducting detector suitable for use in large arrays" by Peter K. Day et al in NATURE |VOL 425 | 23 OCTOBER 2003.
 
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To see is a progress

AS the progress , the time is a period, sorry it isn't a time travel question,but to see the past image is truth. it is a fun question.
 

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