Teslescopes see the past, but which?

  • Context: Undergrad 
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Discussion Overview

The discussion revolves around the concept of observing distant stars through telescopes and the implications of light travel time. Participants explore whether zooming in on a star affects the perceived time of its light reaching the observer, particularly in the context of cosmological distances.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether zooming in on a star that is 100,000 light years away allows us to see it as if we were 50,000 light years away, implying a potential 'fast forward' effect in observing its past.
  • Another participant asserts that zooming in does not change the distance from which the light was emitted, emphasizing that the light observed is from the time it was emitted, not altered by magnification.
  • A participant expresses confusion about how distant images can be resolved given the divergence of light and suggests that the photon emission densities from these stars must be significant to allow for resolution despite the distance.
  • Another participant confirms that the photon flux is indeed very high when close to a star, using the sun as an example of the dangers of observing bright sources from a distance.

Areas of Agreement / Disagreement

The discussion contains multiple viewpoints, with some participants clarifying misconceptions about the effects of zooming in on distant objects, while others express confusion about the implications of light divergence and resolution. No consensus is reached regarding the initial question posed.

Contextual Notes

Participants discuss the relationship between distance, light travel time, and photon flux without resolving the underlying assumptions about the nature of light and observation. The discussion reflects varying levels of understanding regarding these concepts.

trini
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hey guys, ok so here's what's on my mind. we know that everything we see is in the past due to the finite speed of light, my question is, and this applies to everything but let's consider cosmological scales for simplicity:

when we zoom in on a star that is say 100000 light years away with a telescope and see it from a perspective that it would be if we were say 50000 light years away, do we see that star 50000 or 100000 years in the past.

In other words, does zooming in on something optically 'fast forward' you through its past?
 
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oops misspelt the title ^_^'
 
No, it's just bigger.
 
trini said:
In other words, does zooming in on something optically 'fast forward' you through its past?

Nope.
 
trini said:
hey guys, ok so here's what's on my mind. we know that everything we see is in the past due to the finite speed of light, my question is, and this applies to everything but let's consider cosmological scales for simplicity:

when we zoom in on a star that is say 100000 light years away with a telescope and see it from a perspective that it would be if we were say 50000 light years away, do we see that star 50000 or 100000 years in the past.

In other words, does zooming in on something optically 'fast forward' you through its past?

You seem to be under the impression that zooming in on something actually somehow causes it to be closer to you. It doesn't. It just makes that object take up more of the field of view.

No matter what the magnification, you're seeing the object as it was at the time when the light from it was emitted. How long ago that was depends on how far away the object is.
 
indeed, so if this is the case the photon emission densities of these stars must be massive because if what we are doing is essentially 'stretching' the received image radially outwards so as to magnify it then we should also be stretching the space in between the photons.

In other words, for us to be able to still resolve the image even after the kind of divergence(decreasing flux as distance increases) this light would have undergone on its journey to us, the photon flux must be massive at the source, right?

this was really the source of my confusion, how are we able to resolve very distant images if the flux from these objects has diverged so much on the way here.
 
Yes, the photon flux when you are close to a star is incredibly large. That is why we are warned not to look at our sun, even though we are about 150 million km away.
 
cool my mind is at ease ;)
 

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