h a l f b a k e r yTrying to contain nuts.
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Probably the best place in the solar system to put a radiotelescope is the Lunar Farside -- not only is it relatively close (in space terms), but the mass of the moon would block out all of the junk EM radiation from the earth.
Now, we could land huge armies of tractors on the moon to build the
necessary dishes, but why not instead create a super-Arecibo and clear out some of the more dangerous earth-crossing asteroids at the same time? Simply redirect the asteroids to hit chosen areas on the Lunar Farside. Two or three of the right asteroids hitting the same spot could give us a crater where all we have to do is smooth things out a bit and add electronics. Or we could go all out and make Farside look like a golfball so we have a window on half the universe at once, and dome over the extra ones for any colonies we want to set up.
That would provide us with the "Big Ear" we'd need -- at least until we start building telescopes at the sun's gravitational focal point. (Next week, we'll design a circumlunar subway/supercollider :-)
(?) Lunar radio interference
http://www.astro.gl.../LunarFarsideRadio/
Short description of "Why Lunar Farside?" [mrouse, Apr 10 2002, last modified Oct 04 2004]
(?) Another Lunar Link
http://www.astro.gl...ers/yuki/radio.html
A description with pretty pictures ;-) [mrouse, Apr 10 2002, last modified Oct 04 2004]
(?) The Arecibo Observatory in Puerto Rico
http://www.planetar...rvatory_474x600.jpg
Made from a huge limestone sinkhole. Really just linking to answer [phoenix]'s question: //And the idea of a dish is to make the antenna directional, no?// [Worldgineer, Feb 28 2005]
(?) Bad Elephant Jokes
http://www.fortunec...oks/845/elepind.htm
[normzone, May 16 2008]
Lunar crater telescope
https://www.nasa.go...er_radio_telescope/
[xaviergisz, Apr 10 2020]
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Why do elephants have big ears?
Because Noddy wouldn't pay the ransom.
so sorry mrouse...croissant BTW |
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Why not just put the thing in orbit? |
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Earth produces way too much interference -- everything from cell phones to over-the-horizon radars. Look at all the junk caught by Arecibo for setiathome. Lunar farside would block the signals coming from earth and geosynchronous orbit. |
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Er, you're only going to 'hear' the stuff on the frequency you're listening on, no? And the idea of a dish is to make the antenna directional, no? |
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Correct me if I'm wrong, but I don't think it makes all that much difference (except that having the dish closer makes it cheaper to build and cheaper to maintain). |
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This would also endanger the secret military base there. Best to leave that place alone. |
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I think this idea has been around, esp. in science fiction. Definitely a good thing to have, a lot quieter than any earth orbit and hence a quantum jump from Hubble, but colossally expensive. |
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Some better spots further out would probably be one of the moons in the outer system, a comet, or a formation of asteroids at the oort cloud. |
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Even further would be larange points between stars, or 'gulf' regions where there are fewer stars. |
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Ultimately, if we can move to an extra-galactic location, that would be the best. |
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"Dear Noddy,
Please find enclosed the item that renames your closet friend. We are holding him on the dark side of the moon and will not give him back until you pay us lots of toytown gold.
Yours menacingly,
The Lunar Goblins" |
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baboo... mrouse is talking about a radio telescope here. Hubble is not a radio telescope. Different animal. Not a quantum jump, since they serve different functions. |
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Earth EM isn't as big a problem as it would seem, certainly not so big to warrant building a dish on the dark side of the moon. Also, there are lots and lots of non-Earth based known EM sources that you'd still have to filter through. These, along with the Earth based ones, are documented and accounted/allowed for during observation sessions. |
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Some of these are very useful signals, for calibration and sensitivity testing. Arecibo (at least until recently) often uses Pioneer 10's signal as a system test. (Pioneer 10 is about seven billion miles out there now.) |
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Since this seems to be the only problem your idea is meant to overcome, it ain't worth the effort. |
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NASA has plans (and may have already done this, not sure) to create an array of ground-based systems combined with orbiting satellites, resulting in one humongous radio telescope with an effective diameter exceeding the size of Earth. |
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I put up a couple of links to help answer the question "Why put a radiotelescope on the other side of the moon?" I just combined this idea with a way to get rid of pesky earth-crossing asteroids at the same time. By choosing the impact points, we can put huge radio dishes wherever we want. |
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Or if you prefer, we could put one monster crater exactly opposite of earth, shape it so the focus is at L-2, then put the LNA and associated electronics in a satellite at the focus. The resolution would continue to improve as we smoothed out the crater. :-) |
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Surely your added idea of sending large amounts of earth bound asteroids into the moon is not quite as good an idea as it sounds. Forgive me if I'm wrong but isn't one of Newton's laws "every action has an equal and/or opposite reaction"? Large earth-bound movement transferred to the moon probably ain't very bright.... |
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Sending large amounts of earth bound asteroids into the moon is every bit as good an idea as it sounds (heh heh). |
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Asteroids pack quite a punch, granted, but look at how many huge things have hit the moon in the past without doing something drastic like pushing it out of orbit -- the moon is pretty big after all. Better target it than the earth, anyway. With the size of the earth-crossing asteroids I've heard about, a meteor shower on earth would probably be the most dramatic thing that could happen -- and even that is iffy (debris thrown up from the far side would need to fly fast enough to hit escape velocity, but not too fast or it wouldn't loop around the moon and hit the atmosphere). |
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Forcewise, asteroid striking moon = gnat striking human during stroll through park. (pre-emptive "no strolling gnat jokes" admonition) |
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Mind you, to be totally accurate, the gnat would need to be flying at about 24,000 miles per hour. |
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...and the park would have to be in zero gravity... |
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ok, now that I know that the moon won't be sent hurtling towards the earth I shall vote for this idea. I also propose that we set up video cameras near the estimated point of impact and send loads of crap up there that we don't like anymore, and watch in slow-mo playback as it gets crushed by the very edge of the asteroid as it hurls itself into the moon (I'm thinking maybe adding some high explosives in there as well :) !) |
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Actually, having the moon hurtle toward the earth was part of my plan to generate more coastline and higher waves for surfers :) |
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Big ear on the Moon's far side--then another ear would likely follow. From there, it's a slippery slope until before too long you've got the beagle-puss glasses, nose and mustache and googly eyes. We have no right to decorate the Moon to look like Mr. Potatohead. |
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This idea is most definitely not original with the poster.
If I recall right, Heinlein's "The Moon is a Harsh Mistress"
(written about 1968) mentions observatories on the
back side of the Moon. And I don't think Heinlein was first,
either. |
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Next, as soon as we start littering the Solar System with the numbers of spacecraft envisioned in science fiction stories, all communicating with each other, the Lunar radio telescope will start to become less useful The best place to put a bunch of Big Ears is in the Oort Cloud (or farther). The convex sides of their own dishes can block radio coming from the heart of the Solar System, while their outward-facing concave sides can be HUGE (no significant gravity out there), and equivalently sensitive. Not to mention the Very Long BaseLine Interferometry possibilities, with a bunch of Big Ears in various places in the Oort Cloud (or farther). |
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You would have to redirect the moon to have the asteroid hit it. That would take an incredible amount of energy that would be better used to just create the crater ourselves. |
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Big ear on the Moon? Why not Mercury instead? The rotation rate there is so much slower that objects in the night sky are viewable for 88 (Earth) days at a time, as opposed to a mere 14 days for the Moon. This is useful for listening as well as photographing. |
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Oh yea, why would we need to build a crater on the farside when there are so many already there? |
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Why not start with a radio telescope satellite on in lunarsyncronus orbit around the far side of the moon with a relay satellite to send its signals to and from Earth, it would be a good, cheap, demonstration of the idea and technologicly feasable today. |
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I like the idea of putting the telescopes on the asteroids themselves, and sending them on their way across the Solar System |
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I'm not so sure about targetting the far side of the moon...by definition, The Earth is in the background to safely catch any misses. |
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