Seeing Earth's Formation - Can We?

  • Thread starter locutus7
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First time poster and non-cosmologist.

Why can't we use telescopy (across the EM spectrum) to view the formation and development of our planet? Let me explain by laying out some assumptions (correct them if they are inaccurate).

- When we use telescopes (again, I mean x-ray, radio, visual, etc) to capture photons from distant stellar objects, we are in a sense looking back in time. "seeing" a galaxy 10 billion LY away is seeing it as it was 10 billion years ago.

- The photons we collect with our telescopes vary in intensity based on distance and if they are emitted (from a star) or reflected (off a planet). Thus we cannot "see" planets that are too distant as the reflected EM radiation is weaker than that emitted by a stellar object.

- In this scenario we will assume all particles travel not to exceed lightspeed, but let us assume that we may discover other particles such as gravitons that will enhance our capabilities (so we might eventually see images of planets light years away).

- Universe is expanding.

Okay, is it possible, if we could calculate which direction to look, that we could point all of our telescopes (and hypothetical gravitic detectors) to look out 4 billion light years and see the actual formation of our solar system, which would be in a different location than now because of inflation?

And if so, could we look out 2 billion light years (time and distance) and see our nascent planet Earth, and then 1 billion LY and so on and watch our actual planet develop?

Again, assuming an improvement in technology, could this be accomplished, or is my logic flawed?

Thanx in advance.
 

Answers and Replies

  • #2
Nabeshin
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Hey and welcome to PF.

I'm not sure why you think you would find an image of our own Earth "out there" somewhere. The EM radiation the left the Earth since the beginning of its existence has been faithfully traveling outwards away from it in a spherical shell at precisely the speed of light. Therefore, if you wanted to see this radiation in our current epoch, you would need to turn it around somehow. Of course, we can't well believe there to be a giant mirror out there, but it is, at least theoretically, possible that the light could come back to use via gravitational lensing.

So yes it is possible that we could receive a photon from the early Earth if it was very fortuitously gravitationally lensed such that it came back to the Earth's present position. The expansion of the universe isn't really important here.

(Note: Gravitational waves, i.e gravitons, travel at the speed of light)
 
  • #3
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Thanx, Nabeshin, for replying. I wish I could draw an illustration of what I mean. Basically, if our earth was in position X two billion years ago, and is now in position Y because space expanded and everything is flying away from each other.

So the reflected photons, gravitons, whatever-trons from Earth X travel 2 billion light years (in a spherical front) and should be able to be captured by our various instruments on or near Earth Y (our current earth), assuming they were sufficiently sensitive.

Thus from earth we could see the EM emissions from our planet long ago and far away. And if you followed this reasoning to its conclusion, instruments from our current earth, Earth in position Y could view earth 1 million years ago - 1 million LY away- (we will call it position Z Earth because it would be further from Earth Y as it is more recent and thus more distant due to accelerating space expansion).

In other words, we are viewing an image of earth 1 million years ago and if our instruments were super-advanced, we might see dinosaurs, etc. Truly looking back in time at our earth.

How is this flawed? I really want to know, and will try to clarify if my point is unclear.
 
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  • #4
D H
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So the reflected photons, gravitons, whatever-trons from Earth X travel 2 billion light years (in a spherical front) and should be able to be captured by our various instruments on or near Earth Y (our current earth), assuming they were sufficiently sensitive.
No, they can't.

This makes for a nice sci-fi setting where the author can hand-wave the laws of physics goodbye. It is just that, sci-fi. Those photons are long gone, never to be seen again. The only possible exceptions are an fortuitous arrangement of gravitational lenses that curves the light back to us, and a closed, curved universe (some of those remote stars we see is our sun). The former is not just fortuitous, it is outrageously fortuitous. The latter was deemed a remote possibility decades ago, but not any longer. As far as we can tell the universe is flat and very, very big.
 
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D H
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This thread strongly violates the rules of this forum and is therefore locked.
 

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