Space Mirror.

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projectorion

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If you could build a parabolic reflector in space to any size, how big would it need to be to see an Earth-like world orbiting another star under 20 light years away?
 
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nikshliker

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It all depends drastically on the quality of material you use for the mirror, in how much detail you would like to see the planet, and the size of the solar system yo are trying to view... <br /><br />A question that most likely cant be answerd
 
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projectorion

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Exceptional quality and precision material. I was thinking of a base alloy being melted to a liquid state in space by electric current then spun and accelerated at one G to produce a parabolic surface. Then allowed to cool. Shaded from solar radiation, perhaps in the Earths shadow. Without gravity to distort it we might get an exceptionally good mirror. With no size limitations I can think of. Could we use existing mirrors and just scale up the range of vision and diameter of surface to extrapolate values?
 
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tom_hobbes

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I thought one of the limiting factors was the glare from the host sun given the likely close proximity of any Earth like planet to it's parent. <div class="Discussion_UserSignature"> <p><font size="2" color="#339966"> I wish I could remember<br /> But my selective memory<br /> Won't let me</font><font size="2" color="#99cc00"> </font><font size="3" color="#339966"><font size="2">- </font></font><font size="1" color="#339966">Mark Oliver Everett</font></p><p> </p> </div>
 
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Saiph

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that "glare" is the diffraction of the light, which spreads over the area, obscuring the planet's reflected, weak light.<br /><br />A bigger scope reduces this diffraction, narrowing the "noise" and should uncover the planet as a seperate resolvable object.<br /><br />Now, you run into another problem, that of saturation. If you have a scope big enough to do that, the target star will easily saturate any CCD detector, causing the area to "bleed" and spread as the released electrons overflow their region of the chip, once again obscuring the planet.<br /><br />So you'd need a large, low surface area scope, I.e. interferometry, to pull it off.<br /><br />How big, I'm not sure, I put it in the 100m range. <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>
 
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bobw

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There are a few ideas circulating around for building a Terrestrial Planet Finder using interferomers. One is to put several small (10 foot) mirrors spaced along a 40 meter structure; another involves flying the mirrors in formation over a hundred or so meters. Since the synthesized aperture is roughly equal to the distance across the array I guess you would need a mirror in the 40-100 meter diameter range to get good science results. An interferometer can cancel the glare from the star and a single mirror can't, so a bunch of small mirrors will probably work better than one big mirror.<br /><br />This article from Space.com is a pretty good place to start looking for the information you want <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> </div>
 
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tom_hobbes

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Fascinating article Bob. And an ingenious solution to budget restrictions at the end. <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p><font size="2" color="#339966"> I wish I could remember<br /> But my selective memory<br /> Won't let me</font><font size="2" color="#99cc00"> </font><font size="3" color="#339966"><font size="2">- </font></font><font size="1" color="#339966">Mark Oliver Everett</font></p><p> </p> </div>
 
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project0rion

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Thanks guys. Fascinating material. We may never walk on another earth but maybe some day we will be able to look closely enough at one to feel as if we were. Imagine if someone is already watching us.
 
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pr0ject0rion

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It seems to me that Hubble was built to see the very edges of the known universe and identify previously unknown galactic bodies yet doesn't posess the focus to even pick out a super gas giant circling a neighbouring star. Sounds like we do need a massive space array if we ever want to find other worlds like our own. Seems strange there is so little effort being made in this direction. The rest of the worlds in our system are probably lifeless but there are so many other stars we could investigate. One of them within 50 light years must have such a world. Mars and Venus come so close to having the right conditions. Mars is a little too small and Venus has too thick an atmosphere but its mass is almost identical to Earth. So our own system very nearly had three livable Worlds. I imagine the universe is likely littered with Earthlike planets.
 
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kmarinas86

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Why are there 3<br />ProjectOrion<br />Project0rion<br />PR0JECT0RION's<br />?
 
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pr0ject0rion

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Good question. I created a second profile to prevent Doppelgangers from using it to mimic me. Then both profiles had their passwords changed without my authority and by persons unknown. So I created a third. The chances against both these original usernames being cracked at the same time has to be something astronomical. Therefore it is most likely a glitch, an admin or a mod who has decided to play silly buggers. If its a glitch then it should have mucked up other profiles and not just two of mine. Ofcourse I find it hard to believe an admin would waste valuable time playing god with board members. So one of the caretakers (mods) must be on a power trip. Probably someone with too much time on their hands.
 
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