The practical limitation isn't just magnitude, but resolving power. Atmospheric disturbance makes it difficult to resolve anything smaller than a meter from orbit, and the diffraction limit means the further are away from the thing you want to observe, the wider your telescope needs to be. Since the distortion effects near a black hole are near-asymptotic, the features we want to see have <i>very small</i> subtended angles, and we need much higher resolving power to "see" recognizable features.<p>Stars? Definitely feasible. Planets? Much harder. People? Certainly not with available optics.
You don't want the light reflected by 180 degrees - it needs to be reflected where Earth is <i>going to be</i>; a much harder problem. For the easy case quoted in the article of 6 light years, any collimated light would need to be properly directed at the sub-nanoradian (milliarcsecond) level (which is possible -- see sig and [0]).<p>Interesting to think about, even if it is an incredible observational challenge.<p>Fun application for the Arecibo radar, if it's still running. Locking into a modulated signal might yield the necessary SNR?<p>[0] <a href="http://en.wikipedia.org/wiki/File:Diffraction_limit_diameter_vs_angular_resolution.svg" rel="nofollow">http://en.wikipedia.org/wiki/File:Diffraction_limit_diameter...</a>
You need to read 'The Light of Other Days', detailing the use of microscopic wormhole lenses to observe ancient earth: <a href="http://en.wikipedia.org/wiki/The_Light_of_Other_Days" rel="nofollow">http://en.wikipedia.org/wiki/The_Light_of_Other_Days</a>
This Lebbeus Woods has some great artwork. I'd never heard of him before but I found these two pieces by him:<p><a href="http://historyofourworld.files.wordpress.com/2009/11/lw-iii.jpg%3Fw%3D720%26h%3D418" rel="nofollow">http://historyofourworld.files.wordpress.com/2009/11/lw-iii....</a><p><a href="http://www.krobarch.com/images/winners/2012/entry3353.jpg" rel="nofollow">http://www.krobarch.com/images/winners/2012/entry3353.jpg</a>
Does anyone here know why the Einstein cross has 4 of the repeated image instead of being a continuous repetition around the lens object? It seems to me like you should see the magnified image as a sort of circle instead of having a finite number of repetitions.<p>Is this related to the lines forming a cross you see in pictures of stars?
I'm not so much into physics but based on what I understand - ok, we might get just enough photons reflected back by MACHOs if we build a massive new telescope.<p>But then how do we separate them from other photons - ie the ones not reflected back? Do photons reflected by MACHOs have a specific signature on their EM wave ??
I find it sort of ironic that everyone here thinks this would be awesome, but are completely opposed to hovering predator drones observing our every action 24/7. Obviously it's all a matter of who has access to the data, but essentially the data would be the same.
Was reading the article, excited by the prospect when I realised, we have a hard enough time identifying planets dozens of light years away, from direct light, that surely the reflected light from a massive object 3000 light years away would be orders of magnitudes more difficult. Perhaps impossible. Theoretically possible yes, but what sort of technology needs to be invented to actually do it?<p>edit: turns out I should have just finished reading the article.. bigger telescopes!
This reminds me of Greg Egan's short story "The Hundred Light-Year Diary". The text is at [1] but better still buy the book [2]<p>[1] <a href="http://pastebin.com/f341e113e" rel="nofollow">http://pastebin.com/f341e113e</a>
[2] <a href="http://www.amazon.co.uk/Axiomatic-Greg-Egan/dp/0575081740" rel="nofollow">http://www.amazon.co.uk/Axiomatic-Greg-Egan/dp/0575081740</a>
Posting obligitory link to:<p><a href="http://en.wikipedia.org/wiki/Time_viewer" rel="nofollow">http://en.wikipedia.org/wiki/Time_viewer</a><p>Of course someone should mention Father François Brune and his Chronovisor: <a href="http://en.wikipedia.org/wiki/Chronovisor" rel="nofollow">http://en.wikipedia.org/wiki/Chronovisor</a><p>But none of that is real.
If we ever invented FTL travel, even for just probes, this could be done too.<p>Except you'd need insane levels of resolution or a whole new way to think beyond optics to be able to see details.<p>I mean what if you could see that far back but the earth's resolution was only the size of a pin head?
Another possibility (perhaps more feasible?) would be for an intelligent alien civilization to observe light / radio transmissions from Earth, record them, and kindly play them back for us.
I've never seen that image of our galaxy's central region, it's fascinating! Is "Sgr A" the black hole, Sagittarius A*? If yes, why would it be bright? I thought it's inactive.
Ha, that was the plot line of Paycheck [1], but seeing the future, not the past.<p>[1]<a href="http://www.imdb.com/title/tt0338337/" rel="nofollow">http://www.imdb.com/title/tt0338337/</a>