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Unbelievably Large Telescopes On the Moon?
Matt_dk writes "A team of internationally renowned astronomers and opticians may have found a way to make "unbelievably large" telescopes on the Moon.
'It's so simple,' says Ermanno F. Borra, physics professor at the Optics Laboratory of Laval University in Quebec, Canada. 'Isaac Newton knew that any liquid, if put into a shallow container and set spinning, naturally assumes a parabolic shape, the same shape needed by a telescope mirror to bring starlight to a focus. This could be the key to making a giant lunar observatory.'"
Actually, it just seems large because the moon looks so small. My guess is you're holding the telescope the wrong way round.
Confucius say, "Find worm in apple - bad. Find half a worm - worse."
I can't believe it! Do you? *gasps*
http://www.object404.com
...n unbelievably large telescope on the moon.
Any technology distinguishable from magic is insufficiently advanced.
As with many ideas, this is so simple I can't believe we haven't thought of this before.
'Impossible' is a word that humans use far too often. -- Seven of Nine
When I saw the summary I actually HOPED it would be misleading, because it makes it sound like nobody had thought of liquid mirror telescopes before. Now it's possible that they were just copying a similarly misleading article, but no... even has a nice photo of the Large Zenith Telescope to spice things up. Space Fellowship 1 - Slashdot 0.
Yeah, building stuff on the moon is a doddle.
Hmmm...as the article notes, the idea of liquid mirror telescopes isn't new, so it seems a tad odd that this is being trumpeted as a breakthrough.
The ionic liquid coated with silver is cool, though.
Kythe
Since the "dark" side of the moon is protected from the radio emissions from Earth, I think it's inevitable that the dark side will one day be "the" spot for big radio telescope arrays. Why not put our biggest optical telescope there as well?
No folly is more costly than the folly of intolerant idealism. - Winston Churchill
to get liquids to the moon?
Too big to fit into our current spaceships is nowhere near unbelievable.
The range of unbelievable scale starts at 1000m. This idea could work for a rotating mirror that large, but not on the moon unless you're willing to lay rather a lot of maglev track to support the weight of the outer edges of the mirror, or to take a ludicrous amount of support structure to the moon.
*starts playing frenetic circus plate-spinner music*
That's great. When they want to look at a different patch of sky, they can just just swivel the moon.
steampunk web design
Maybe they should ask the science community for 1 million dollars to build this "Telescope".
"wahts woring iwth my tyoping?"
which as always, will require correction. In this case, for the Moon's own rotation (for instance, Coriolis force if not at a pole). And precessionary wobbles, if the Moon is still precessing.
"Cock Up Your Beaver" does not mean what you think. This sig is intended to clog filters and annoy do-gooders
a 3 million dollar overhead projector...oh wait...you mean there are other kinds of projectors?
Twinkling has been technologically defeated in serious astronomy. Parallax measurements would benefit but not on the levels that it's currently done on. Your accuracy of a parallax measurement when the observation points are only a quarter of a million miles apart is going to suffer compared to when they're 186 million miles apart.
Dedicated Cthulhu Cultist since 4523 BC.
The "liquids" to be used are less dense than water, and being placed on the lunar surface, which is covered in dust several times finer than baking powder.
I'd give it about 3-5 days (depending on the size) before the "revolving liquid mirrors" become revolving lunar mud pies.
VLC FOR MAC IS DYING! IF YOU DEVELOP, PLEASE SAVE IT!!
This is total lunacy!
Knowledge is power. Knowledge shared is power lost.
Really? I wonder what they did wrong. Maybe they should have just bought plane tickets to Canada instead:
http://www.astro.ubc.ca/LMT/lzt/index.html
it wasn't even part of a myth, it was part of a contest between two outside groups trying to start things on fire with mirrors. when they discovered that all teams were technically not fully within the rules they had to revise their mirrors, the one time tried to use plaster in a spinning platform to form parabola but it didn't come out with the correct shape so they had to abandon it. no myth was busted from this.
it was this episode
I know this isn't typical slashdottiness, but I actually read the article, and have some knowledge of telescopes in general. But since you won't believe me purely on my supposed knowledge, here's a quote from TFA:
And to add insult to injury (Uh Oh...): http://en.wikipedia.org/wiki/Large_Zenith_Telescope
Yeah... They'll never work. Mythbusters said so.
Coz eternity my friend, is a long *ing time.
The biggest issue I see with this tech on the moon is that not many substances exist as a liquid in a vacuum, and while I appreciate that the lunar surface isn't a true vacuum, it's good enough that your telescope would either evaporate or freeze almost immediately.
That said, if you could get a liquid mirror up there and spin it into shape, you could then expose it to the outside temperature to freeze it, and you'd remove the need to keep spinning it forever.
It would mean having to choose the right material (solid at moon temperature, liquid at not too much more, small/no surface crystals on freezing, ionic so that it can be coated with silver, ...). Making something like this on the moon would be much cheaper than taking it up there.
OK: I understand that they might not want to steer if far off vertical to keep things cheap but I would have thought that a little directionality would be a boon.
If this would have been a "steampunk" telescope on the moon, then this article would have made boingboing.
One hopes they have better things to do. Do you Slashdotters even read articles?
Some people who actually know what they are doing tried it and it did work.
BTW the first working laboratory LMT was built in 1872.
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
we don't have to transport massive amounts of equipment to the dark side of the moon.
It's FAR SIDE people! Far Side, Far Side, Far Side. Like the cartoon. The Moon is tidally locked to Earth, so there's a Near side and a Far Side. If it were tidally locked to the Sun, then you'd have a light side and a dark side. But it's not, so we don't. There is no dark side of the moon, except for the ever changing half that's facing away from the sun at the moment.
When our name is on the back of your car, we're behind you all the way!
This could be the key to making a giant lunar observatory
Or a fully functional battle-station.
It just looks big because you're seeing it through a powerful telescope.
A lot.
The mass of the moon is ~7*10^22 kg (70 billion trillion kg). The mass of the Saturn V rocket is about 3 million kg. If we sent up a Saturn V rocket for every man, woman, and child on the planet, we wouldn't even be close to an appreciable fraction of a percent of the moon's mass. And even if we were, it is a stable system so there wouldn't be any significant effect.
One standard, starched, American flag... Oh. Shit.
Look, I don't care who you work for sonny, you are not flying with more than 100ml of liquid in your luggage, so hand it over. Bloody astronauts think they are so superior.
Home fucking is killing prostitution.
I don't believe it.
talked about making silvered-ice mirrors on the Moon in his 1981 story The Patchwork Girl. Not quite liquid, but it would certainly start out that way, and probably at least grossly shaped in the same method. (Figuring and finish would probably be done the traditional way, though.)
And being solid, an ice mirror would be STEERABLE.
Welcome to the Panopticon. Used to be a prison, now it's your home.
Such a telescope would prove very useful to the Whalers on the Moon when seeking out new hunting-grounds.
Cress, cress, lovely lovely cress
...at the sun's gravitational focus. You'd be able to resolve a planet halfway across the galaxy.
First link I pulled from Google (but there are several others): http://www.centauri-dreams.org/?p=176
Surely that would be a "Probe"!
Oh, "Parsons", sorry, forget I said anything. ;-)
simon
As I understand it, the moon's gravitational pull works against the earth's and the two are in a sort of balance that determines the distance of the moon's orbit, or something.
Yes, but the mass of the object is irrelevant. Very approximately, an orbit is where the outward force due to centrifugal force[*] is equal to the inward force due to gravity; both these terms scale linearly with mass, so if you increase the mass of one, the other increases proportionately and the balance remains.
(This is why the space shuttle and the space station can be in the same orbit a few metres apart, despite being different sizes.)
Also, in general the human race is nowhere near able to do any kind of cosmic engineering, deliberate or otherwise. Even if we bent all our resources to it, we wouldn't even be able to significantly resculpt the surface of our own planet, let alone another one.
[*] To pedants: yes, I know.
(BTW, the moon already is lopsided. The same tides that pull water around on Earth pulls the rock around on the moon. The near side of the moon is significantly larger than the far side. Interesting factoid: the moon is so irregular that setting up a stable orbit around it is really hard.)
Everyone, sing with me:
We're whalers on the moon
We carry a harpoon
But there ain't no whales
So we tell tall tales
And sing a whaling tune
Oh yeah? What about the the Pioneer and Voyager probes that we've sent (almost) out of the solar system!?
Relax. The amount of mass is too small to make a real difference. The December 2004 earthquake that caused the Indonesian tsunami released more energy than we've ever produced/harnessed as a race, and consequently moved many orders of magnitude more mass than we will in the foreseeable future. Its effect on Earth's rotation was the barest fraction of a percent.
I think it's marvelous! HaHaHa!
One swallow does not a fellatrix make
Communication won't be a problem when using a polar orbit. But apparently this is more difficult than it sounds:
http://science.nasa.gov/headlines/y2006/30nov_highorbit.htm
This is not the sig you're looking for.
Quick answer: When the telescope has enough mass to make tidal forces.
My UID is prime. Hah!
How in the world will they protect the device from micro & macro impacts?
would seem to be a problem. I mean, if you get a few strikes of dust particles whacking your liquid mirror every couple of hours, won't it always have a bad picture?
This is my sig.
Don't make big plans, 'cause you're broke...
You can't have a trillion dollar bailout of the rich bankers, buy up every dishwasher's quarter-million dollar underwater mortgage, hold a permanent-endless war on the other side of the world, ... and have a giant telescope on the moon. It's not possible, it's science fiction.
All the space exploration projects being talked about and planned for the 2020's may actually happen...in the 2120's or 2220's. Not in ten years from now.
I know that you're all young and starry-eyed, but in the bankrupt USA, reality rules. And reality says that there isn't going to any giant new space program in the 2010's-2020's.
Don't just mod me to -1 for simply telling you the truth. And don't tell me how small the giant new space program is compared to other absurd federal government programs. Those programs are toast also.
My American friends...you are simply broke... you have dreams... but you have no money.
> The story would be more believable if they did not get certain basic facts wrong.
> Mercury has a very low vapor pressure, it's not going to evaporate very quickly.
Quickly enough. The astronomers are capable of doing the math.
> That's why you don't see mercury fog inside a mercury switch or thermometer.
Fog consists of fine droplets of liquid suspended in gas. Their absence tells you nothing about vapor pressure.
The head space in the thermometer is filled with mercury vapor. The head space in the switch also contains mercury vapor though it may be filled with air or inert gas as well.
> The cost and weight of the mercury are inconsequential compared to the cost of the
> rocket to lift the telescope up there.
The plan is to build the telescope on site using local materials where possible. Your mercury would significantly increase the mass that would need to be lifted up there. It would have to be replenished frequently due to evaporation, adding to support costs.
It would also have to be heated to keep it liquid. This would also add to support costs and prevent the mirror from getting as cold as the ionic liquid ones can.
IIRC the spinning mercury telescopes here on Earth use a plastic film to prevent air currents from disturbing the surface of the mercury. Perhaps such a film could be used on the moon to reduce evaporation.
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
Exactly how would this work when Hubble's main mirror was 2.3 microns off, which in turn caused the Hubble to become useless until the mirror was replaced? Can you actually spin a liquid so precisely that you get a product that is worth the expense?
its the moon after all, cheaply and bountifully available
intellectual property law is philosophically incoherent. it is your moral duty to ignore it or sabotage it
Lasers on the moon?
I was speaking more of the article summary here than the article itself.
Kythe
But given millions of years... would we want to increase the weight or decrease the speed to counteract the outward momentum? any appreciable increase in mass we can accomplish may amount to only a benefit.
The massive spinning pool could have a boat in it, with sailors -- the Futurama prophesy may come to pass!
vatch me split my letters.
Won't the whales displace enough water to disrupt the optical properties?
For great justice.
Isaac Newton knew that any liquid, if put into a shallow container and set spinning, naturally assumes a parabolic shape, the same shape needed by a telescope mirror to bring starlight to a focus.
The only reason I can think that evolution then has not developed this as a vision enhancement is that evolution still hasn't developed the wheel. Otherwise it would be a selected-for survival trait as an aid for detecting predators and prey at greater distances.
Oh, say does that Star-Spangled Banner entwine / The myrtle of Venus with Bacchus's vine?
Best re-formulation of the facts I've heard all day.
DRM: Terminator crops for your mind!
I believe it was some form of hovercraft.
Prior Art
The idea goes back at least as far as 1803, and was recognized as being old then (some attribute the idea to Newton). Robert W. Wood, a University of Baltimore physicist, built the first one recorded (using mercury as the reflector) in 1909, but could not keep the spinning base spinning at a constant rate.
Borra has a tendency to announce these things again every so many years as if they are newly invented; here's an article from 1986: ahref=http://findarticles.com/p/articles/mi_m1200/is_v130/ai_4371602/pg_1?tag=artBody;col1rel=url2html-6340http://findarticles.com/p/articles/mi_m1200/is_v130/ai_4371602/pg_1?tag=artBody;col1> ...note that it predates the 1990 date where the article linked in the posted story claims he's only started studying them 4 years after that.
-- Terry
Instead of a single large mirror (liquid or not), one may instead use an array of smaller mirrors. It is trivially easy to make a lot of small optically flat mirror of perhaps 30 cm in diameter, as opposed to a curved mirror of a much larger size. I'll let the optical/astronomy/math geeks run with this one to figure out an appropriate size array of "flat" mirrors would be within tolerances for truly enormous curved mirror.
OK, what was the science fiction story some years back about this? By Lee Correy? All I can google about it is someone else asking the same question... someone with a pile of Analogs in their attic want to take a look?
while not being able to ignite the boat might seem like failure but in reality heating the wood to 400 degrees F means anyone on board would feel pretty uncomfortable if they were exposed to the light which would likely enough to cause permanent and instant blindness and some rather painful skin burns; I was on fire a couple years ago and it's pretty intense and intimidating.
Apocalypse Cancelled, Sorry, No Ticket Refunds
Then it could be Buster Gonad and his unfeasibly large telescope!
Task Mangler
The following is excerpted from:
Amateur Telescope Making.
Scientific American Publishing Company, 1928.
pp 244-245:
Rotating, Mercury Mirror: Dr. R.W. Wood, Professor of Experimental Physics at Johns Hopkins University attempted in 1908 to make an automatically paraboloidal mirror of variable focal length by the theoretically practicable method of rotating on a central, vertical axis a round, shallow pan of mercury. Under centrifugal action the mercury takes on the figure of a true paraboloid. Using a 20 inch pan, a rubber thread transmission and a magnetic clutch, Dr. Wood obtained interesting results, the focal length being varied with ease by changing the speed. Minute irregular disturbances injured the perfection of the mirror's surface, despite the velvety transmission or drive. The mirror was rotated at the bottom of a well, and since it is horizontal, it reflected only the zenith stars; a flat would therefore be required to complete the equipment so that it would take in a large field. The original experiments were described by Dr. Wood in the Scientific American, March 27, 1909, page 240 (out of print -- consult at large public libraries), and in Astrophysical Journal, March, 1909. This interesting experiment was originally proposed in the Scientific American, Dec. 13, 1873, page 365 by someone who signed "D." It is known, however that "D" was David Todd, later to become Professor of Astronomy at Amherst College. Dr. Wood's experiment was not completed. The elimination of the ripples required a constant speed of drive.
The above note was submitted to Dr. Wood with a request for comment. He replied as follows: "The experiments were continued after the publication of the papers, but I never published anything more on it. I got it to work much better the second summer. I put a 20-inch flat over it and had excellent views of the Moon. The final conclusion was that constant speed of drive would eliminate the slight tidal wave, which was all that remained. I did not even have a synchronous motor. One of these, operated on a modern A.C. circuit with the cycle frequency controlled by clock, would be a great improvement. I do not advise anyone to try the mercury mirror, however."
The entry on Mercury Telescopes contains an additional long paragraph on synchronous motors and clock drives that I have not transcribed.
An interesting note. After typing all this in, I went to the front of the book to type in the bibliographical information and was astonished to find that the first page is inscribed, in pencil, presumably with the name of the original owner:
R.W. Wood
John Hopkins Un.
and the used bookstore price, as purchased by my Wife's Grandfather: $2.00.
How about that!