3 ms·

This is admittedly a bit over my head, but does that mean it is technically possible that an image of earth could be captured from the distance needed to see Pa

by asxd 5y ago

This is admittedly a bit over my head, but does that mean it is technically possible that an image of earth could be captured from the distance needed to see Pangaea? Thinking about this has sparked a bunch of questions I hadn't thought of before. For instance, does information encoded with light degrade over long distances in a vacuum? If not, it does seem like a mega-lens could potentially capture such an image right?

hutzlibu 5y ago
"For instance, does information encoded with light degrade over long distances in a vacuum?" Since the vacuum is not totally empty, it does as far as I know. Just like humid air fogs the picture.
- asxd 5y ago
  Good point, I was being idealistic and imagining space as a perfect vacuum.
  - ceh123 5y ago
    Under this perfect assumption you end up having a problem with the red shift caused by the expansion of the universe (which I didn't account for above) that lengthens the wavelength of the light you want to see, requiring an even larger lens. On the lens side of things, as far as I'm aware (not a physicist, math PhD student who is just generally into this sort of thing) there isn't anything fundamental preventing you from collecting this light and building the lens, but from our current understanding of materials science I'm fairly confident it's currently impossible to construct a structure that will stay together that large. That being said there may be ways around this problem, like I said not a physicist or engineer, but you are right that from an information theoretical perspective if you ignore dust and other things in the way then yes all the information is still there.
    - martinpw 5y ago
      > Under this perfect assumption you end up having a problem with the red shift caused by the expansion of the universe (which I didn't account for above) that lengthens the wavelength of the light you want to see, requiring an even larger lens. Redshift does not come into play at the 'small' scale of our galaxy since the Milky Way is a gravitationally bound system that does not itself expand with the Universe. Even within our local group (eg from Andromeda) it is not an issue since the local group is also gravitationally bound. Redshift only becomes an issue at much larger scales, if you are in another galaxy outside our local group.
      - ceh123 5y ago
        Yup good point. Thanks for the clarification

by asxd 5y ago

hutzlibu 5y ago

"For instance, does information encoded with light degrade over long distances in a vacuum?" Since the vacuum is not totally empty, it does as far as I know. Just like humid air fogs the picture.

asxd 5y ago
Good point, I was being idealistic and imagining space as a perfect vacuum.
- ceh123 5y ago
  Under this perfect assumption you end up having a problem with the red shift caused by the expansion of the universe (which I didn't account for above) that lengthens the wavelength of the light you want to see, requiring an even larger lens. On the lens side of things, as far as I'm aware (not a physicist, math PhD student who is just generally into this sort of thing) there isn't anything fundamental preventing you from collecting this light and building the lens, but from our current understanding of materials science I'm fairly confident it's currently impossible to construct a structure that will stay together that large. That being said there may be ways around this problem, like I said not a physicist or engineer, but you are right that from an information theoretical perspective if you ignore dust and other things in the way then yes all the information is still there.
  - martinpw 5y ago
    > Under this perfect assumption you end up having a problem with the red shift caused by the expansion of the universe (which I didn't account for above) that lengthens the wavelength of the light you want to see, requiring an even larger lens. Redshift does not come into play at the 'small' scale of our galaxy since the Milky Way is a gravitationally bound system that does not itself expand with the Universe. Even within our local group (eg from Andromeda) it is not an issue since the local group is also gravitationally bound. Redshift only becomes an issue at much larger scales, if you are in another galaxy outside our local group.
    - ceh123 5y ago
      Yup good point. Thanks for the clarification