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2Spoons

Thu Jun 14 2012, 04:10AM

Registered Member #2939 Joined: Fri Jun 25 2010, 04:25AM
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Posts: 615

I would love to see the telescope capable of resolving 100m objects 20+ light years away...
We can't even see moons around distant planets, so you can forget spotting space junk.

HV Enthusiast

Sat Jun 16 2012, 03:29PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

2Spoons wrote ...

I would love to see the telescope capable of resolving 100m objects 20+ light years away...
We can't even see moons around distant planets, so you can forget spotting space junk.

Yeah right. Even the hubble which has a resolving limit of 0.05 arc seconds at 20 light years the minimum resolution it could detect is approx. 45,800,000 km!!! (assuming my math is correct) You'd probably need a telescope bigger than the earth to resolve 100m objects at 20 light years!

I don't know about the math, but i'm guessing its probably equivalent to seeing a molecule on the moon with an earth telescope.

Steve Conner

Sat Jun 16 2012, 06:00PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I agree with Les. It could just be the way of things, that planets of the right size to be habitable are too small to provide resources for nursing a civilisation to the point of technological awakening, and then building a fleet of interstellar spacecraft.

I think most important of all are the cheap fossil fuels that would have powered the infrastructure, even if the rockets themselves would have used some more advanced energy source. I bet it'll be a lot harder to build spacecraft in a post-carbon society, and I wouldn't be surprised if in putting a man on the moon (using a fossil-fuelled rocket!) we've already got as far as we'll ever get.

On the bright side, there is a lot of leeway between dropping out of the space race and going extinct as a species. We will see that space of options start to be explored in our lifetimes.

Chris Russell

Sun Jun 17 2012, 06:55AM

... not Russel!
Registered Member #1 Joined: Thu Jan 26 2006, 12:18AM
Location: Tempe, Arizona
Posts: 1052

Tesla555 wrote ...

2Spoons wrote ...

I would love to see the telescope capable of resolving 100m objects 20+ light years away...
We can't even see moons around distant planets, so you can forget spotting space junk.

I don't know about the math, but i'm guessing its probably equivalent to seeing a molecule on the moon with an earth telescope.

Let's do the math!

Hubble's angular resolution is 0.05 arcseconds.

The angular diameter of a very large, 100m piece of space "junk" (about the size of the ISS) at 20 light years is about 1.1e-10 arcseconds. (206265 d / D)

So yes, Hubble is nowhere close. A single hemoglobin molecule is about 6nm(.000000006m). Something with a resolution of 1.1e-10 arcseconds would be the equivalent of being able to see a hemoglobin molecule at a distance of 1.13e7 meters, or about 11,000 kilometers. Not quite earth-moon distance, but good ballparking!

So, how big would a telescope have to be in order to see a 100m piece of space junk at 20 light years? The approximate formula for a telescope's resolution is Radians=wavelength/objective diameter. 1.1e-10 arcseconds is 5.3e-16 radians, so 510nm (green light wavelength) / 5.3e-16 radians = 9.6e17nm, or 960,000 kilometers. This is much larger than the Earth -- a telescope this powerful would have to be a little less than three times wider than the distance from the earth to the moon.

Sulaiman

Sun Jun 17 2012, 07:10AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

So ...
Phase 1, a phased array of telescopes in orbit around the earth at 1 LD
Phase 2, a phased array of telescopes in orbit around the sun at 1 AU

might cost a lot though!

OR

If coilers of the world unite
a global array of GPS synchronised Tesla coils may attract some attention.....

ALSO

I propose every February 29th should be a global day of electromagnetic silence
shut down all infrastructure, electrical, communications, lighting etc. networks,
only emergency services and battery powered receivers allowed.
How nice to have a day of no noise, radio, tv, work, transport...
The only problem may be a baby boom 9 months later.

Chris Russell

Sun Jun 17 2012, 11:40AM

... not Russel!
Registered Member #1 Joined: Thu Jan 26 2006, 12:18AM
Location: Tempe, Arizona
Posts: 1052

Yes, that's the idea behind very long baseline interferometry. Current resolutions are measured in microarcseconds. We need 10,000 times more resolution (and a lot more sensitivity) to meet the 1.1e-10 arcsecond requirement, though, and it works at the wrong wavelengths to be able to "see" space junk.

Costing "a lot" is relative. It would cost a lot compared to our current space programs to put an array of radio/optical telescopes in solar orbit, yes. The annual cost, though, spread out over many cooperating nations, would probably be a tiny fraction of what each participating nation spends using and maintaining their militaries. The UK alone spends enough on military expenditures each year to launch three (yes, three) manned missions to Mars -- to say nothing of what the US, China, and Russia are currently spending. Humanity could do great things if we could find a way to get along just a little better.

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