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Comment by Overtonwindow | Hacker News Reader

Just curious, maybe there is someone out there that can explain this: If there was an earth-like planet way out there, and if someone was on those planets looking back at us, what would they see? What do we look like from a billion light years away etc. ?

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This question was asked on Reddits AMA:

https://www.reddit.com/r/IAmA/comments/5vkoyd/were_nasa_scie...

'The next generation of space telescopes, after WFIRST and JWST, to be launched in the 2030's. would be capable of actually getting a spectrum of the Earth, separate from the sun, using an instrument called a coronagraph or a star shade. The current telescopes could measure the size of the Earth as it transits in front of the sun. However, that only happens only once per year, so you have to know when to look, or look for a long time. The latter strategy was adopted by the original Kepler Mission. Michael Werner'

I can't quite answer this, though I can share an image that has always made me feel absolute awe. Google 'pale blue dot' - that image was taken in 1990 by the Voyager 1 from a distance of approximately 6 billion kilometres.

> from a distance of approximately 6 billion kilometres.

or 5 light-hours. Still absolute awe :)

Right now, an observer 39 light years away would be receiving our light and thus seeing the earth of 39 years ago.

So these planets, should they have observers and amazing telescopes would be able to see the Earth of 1977.

For a billion light year distant planet, they would be seeing earth of a billion years ago.

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