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Catching Photons Coming from the Moon

Zonk posted more than 8 years ago | from the need-better-than-a-jar dept.

146

Roland Piquepaille writes "In 'Shooting the moon,' the San Diego Union-Tribune describes how and why physicists from UCSD are using lasers to send light pulses in direction of an array of reflectors installed on our moon in 1969 by Neil Armstrong and Buzz Aldrin. One of the goals of these experiments is to check the validity of Einstein's theory of general relativity. Another one is to measure the distance between the Earth and moon with a precision of one millimeter by catching photons after their round trip to the moon. But it is amazing to realize how difficult it is to capture photons after such a trip. I also have up a summary, which contains additional details and pictures, if you just want to learn how difficult it is to capture photons back from the moon."

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nice (1)

old and new again (985238) | more than 8 years ago | (#15723475)

we finaly have the tech to prove the theory(or at least try)

Re:nice (1)

cleverhandle (698917) | more than 8 years ago | (#15723577)

There have been experimental verifications of General Relativity for quite some time now. IIRC, Einstein himself noted how his theory accounted for a slight deviation in Mercury's orbit that Newtonian mechanics could not. And, if you don't consider astronomy quite "experimental" enough, there have been experiments with clocks and other such things. The first Google hit got me this page [utoronto.ca] , which looks like an understandable enough summary.

LOOKS LIKE ZONK SCORED SOME ANAL FROM ROLAND (1)

CmdrTaco (troll) (578383) | more than 8 years ago | (#15723644)

Or is it the other way around? Who knows...

Re:nice (3, Insightful)

Umbral Blot (737704) | more than 8 years ago | (#15723581)

Oh we had the technology to verify the theory long ago (the atom bomb was one such verification of E=mc^2, the slower decay of fast moving particles is a verification of time dilation, the bending of light arround the sun observable during an eclipse is a verification of the curvature of space time, and the explanation of Mercury's orbit is a verfication of E=mc^2 in the other direction), this is simply an additional check.

If you look close... (3, Funny)

DumbSwede (521261) | more than 8 years ago | (#15723478)

You can just make out the begin of what looks like the word "chair"

Re:If you look close... (1)

B3ryllium (571199) | more than 8 years ago | (#15723568)

SPOOON!! hahah :) Nice reference. [wikipedia.org]

Mirrors? On the moon! (-1, Troll)

glowworm (880177) | more than 8 years ago | (#15723495)

But we all know the Moon landings were a hoax [ufos-aliens.co.uk] . These researchers must be faking their results to fraudulently obtain grant money.

Re:Mirrors? On the moon! (1)

0racle (667029) | more than 8 years ago | (#15723583)

Don't tell Buzz, he's really committed to the lie.

Re:Mirrors? On the moon! (3, Interesting)

megaditto (982598) | more than 8 years ago | (#15723594)

I know you are trolling, but the real Moon-hoax tinfoilers never claimed that 'something' didn't land on the Moon, just that no humans from Apollo 11/12 landed on the Moon.

The Hatter idea is that no living thing can escape the atmosphere and survive (due to radiation [wikipedia.org] or whatever reason the Hatters claim). And no, the Space Station and the sattelites are technically inside the atmosphere, well below the Van Allen belt.

The reflector delivery and the soil sample return could be done by a robotic probe, which in fact is what the Russians did with their Luna 16 [wikipedia.org] mission about a year after the alleged Apollo 11.

Since the Russkies got the first sattelite (Sputnik), the first man in orbit, the first suit walk, the first docking, etc., the thinking was that we could sound-stage their glorious defeat, end the darn space-race, then go spend the money on something more profitable [wikipedia.org] .

The credible conspiracy theory: Send the humans into orbit, camp in orbit while the robot [nasa.gov] fetches the samples, reunite humans with the 'bot, then land as heroes.

Re:Mirrors? On the moon! (1)

Beryllium Sphere(tm) (193358) | more than 8 years ago | (#15723654)

The funny thing being that with 1960s technology it would have been harder and more expensive to create thousands of hours of difficult fx than to land on the moon. This was before CGI.

Re:Mirrors? On the moon! (2, Funny)

megaditto (982598) | more than 8 years ago | (#15723702)

http://science.slashdot.org/science/06/07/13/16542 00.shtml [slashdot.org] Apollo 11 TV Tapes Go Missing

Let me ask, have YOU seen any of these "thousands of hours" of high-res tapes that you refer to. Have you seen a single original frame? The fact is that Williams and Kranz (top brass in charge of the archives and missions at NASA) conceed that the original data is misplaced, believed wiped.

All we have now is re-filmed qvga-res shit: tv-grabs, literally.
But don't despair, for NASA, like the OJ, just might finally find the reel killer.

What's funny is that one would need post-doctoral training to even understand just the kind of info one could extract from high-quality TV scans; I do not expect you to understand.

The bottom like is that whether the TV feeds came from the Moon or from a set [wikimedia.org] we will not know until the original tapes can be examined.

Re:Mirrors? On the moon! (1)

MichaelSmith (789609) | more than 8 years ago | (#15723771)

All we have now is re-filmed qvga-res shit: tv-grabs, literally.

We have the ALSJ [nasa.gov] and I don't believe there was a writer in the world (let alone in the US) in the 1960's and '70s who could have written it from scratch.

Re:Mirrors? On the moon! (1)

megaditto (982598) | more than 8 years ago | (#15723818)

We have the ALSJ and I don't believe there was a writer in the world (let alone in the US) in the 1960's and '70s who could have written it from scratch.


What are you trying to say here, exactly?
Are you claiming the aliens beamed ALSJ down on stardate 3134.0? Or the NASA con-men scripted it?

I just don't care either way. I was merely pointing out to GGP that the reasonable tin-foil hatters never claimed Apollo 11/12 was fake, just that the humans on the Moon part was fake.

Nothing to see... (0)

Anonymous Coward | more than 8 years ago | (#15723498)

At my university (Wesleyan) we have a duplicate of the reflector array (one of the physics professors was involved with the Apollo program) in the basement. Its says on the plaque that already know the distance to a few cm and it was enough to provide relativistic evidence. My guess is that this experiment is just a higher wavelength laser (think blue vs. red) and appropriate detector. I know that there are completing modifications to relativity to increase accuracy and that this experiment might help on that front, but such high precision measurements are commonplace. Why this is front page news is beyond me.

Re:Nothing to see... (0)

EGSonikku (519478) | more than 8 years ago | (#15723510)


You are aware that the moon's orbit is slowly going further out and eventually it will be flung out and lost? I'd wager the distance is minutly further out now than in the 60's.

Re:Nothing to see... (2, Funny)

H3g3m0n (642800) | more than 8 years ago | (#15723549)

Its being further out might have somthing to do with all those pesky scientists bouncing photons off it.

Re:Nothing to see... (1)

MichaelSmith (789609) | more than 8 years ago | (#15723584)

You are aware that the moon's orbit is slowly going further out and eventually it will be flung out and lost?

The Earth doesn't have enough angular momentum to do that. Eventually earth and moon will be tide locked to each other and recession will stop.

Re:Nothing to see... (1)

megaditto (982598) | more than 8 years ago | (#15724010)

Wrong.

it's people like you that make us depend on alien engineers.

Re:Nothing to see... (1)

Profane MuthaFucka (574406) | more than 8 years ago | (#15724865)

Actually it'll continue to move outwards at a slowing rate until it stabilizes at about 1.5 times the size of the current orbit. The rate at which the moon's orbit changes is not and never has been constant.

Re:Nothing to see... (1)

kfg (145172) | more than 8 years ago | (#15723556)

Why this is front page news is beyond me.

Because it's the first time the journalism majors at the San Diego Union-Tribune have heard about it, compounded by the fact that they had reason to bury some of the real news back in the C section where they hope noone will notice it.

And for what it's worth I've just come back from an hour or so of catching photons from the moon without any sort of instrumentation at all. Piece of cake.

KFG

Re:Nothing to see... (1)

helioquake (841463) | more than 8 years ago | (#15723642)

My guess is that this experiment is just a higher wavelength laser (think blue vs. red) and appropriate detector.

Bluish green, if I recall correctly. On a slightly misty night I drove by one facility in Greenbelt, Maryland, and saw a freakin' laser beam shooting off the dome. Scare the hell out of me.

Why this is front page news is beyond me.

It may have to do with the submitter.

Good. (1)

headkase (533448) | more than 8 years ago | (#15723501)

Well good, at the least now the conspiracy nuts will now have to admit that aliens from Area 51 put up that pesky reflection array on the moon. But damnit, men did not walk on the moon.

Re:Good. (1)

ArbitraryConstant (763964) | more than 8 years ago | (#15723646)

A robot probe could easily have carried a reflector. People wouldn't be required.

Re:Good. (1)

headkase (533448) | more than 8 years ago | (#15723765)

It would have had to have some pretty impressive computer controlled landing software for 1969!?!
A lot of people worked on the moon shots, so many that something did go to the moon in July of 1969. I believe that people went because they could handle all the problems easily (e.g. landing) that computers of the era could not easily do.
People also tend to think that finding one case where a general rule fails invalidates the entire rule. The entire moon shot could have been faked at great expense at the time - so much so that actually doing it cost less.

Re:Good. (4, Informative)

1u3hr (530656) | more than 8 years ago | (#15723850)

It would have had to have some pretty impressive computer controlled landing software for 1969!?!

There had already been a few robot landers. Three Rangers, which crashlanded; five Surveyers [nasa.gov] (1966-68) which successfully softlanded. The Apollo 12 astronauts visited the Surveyer 3 [nasa.gov] site.

Re:Good. (1)

njh (24312) | more than 8 years ago | (#15724121)

Not to mention the various russian landers that predated Nasa's efforts.

Re:Good. (1)

ArbitraryConstant (763964) | more than 8 years ago | (#15724900)

I don't personally doubt that the Apollo missions happened more or less as NASA claims. But the presence of a reflector is not the reason I believe it. I believe it for other, more compelling reasons. I pointed out that there are other ways for a reflector to be there because I don't want to see my position supported by such a weak argument.

"It would have had to have some pretty impressive computer controlled landing software for 1969!?!"

Indeed. And it's even more impressive that a Soviet computer did it first, in 1966. What's your point?

Re:Good. (1)

PresidentEnder (849024) | more than 8 years ago | (#15724939)

No, no, see, this whole thing is a conspiracy, too. There is no reflector array on the moon, the scientists are lying to us. All the footage of "laser pulses" is faked in a Fox News studio.

Snippet describing how difficult it is ... (4, Informative)

Hulkster (722642) | more than 8 years ago | (#15723502)

"Only about one part in 30 million of the light we send to the moon is lucky enough to actually strike the targeted reflector. But the reflector is composed of small corner cubes, and for reasons related to the uncertainty principle in quantum mechanics, the light returning from each of these small apertures is forced to have a divergence (called diffraction).

In the case of the Apollo reflectors, this divergence is in the neighborhood of 8 arcseconds. This means that the beam returning to the earth has a roughly 15 kilometer (10 mile) footprint when it returns to the earth. We scrape up as much of this as our telescope will allow, but a 3.5 meter aperture will only get about one in 30 million of the returning photons -- coincidentally the same odds of hitting the reflector in the first place."

I.e. 1 out of 30,000,000^2 photon's come back to be captured.

Re:Snippet describing how difficult it is ... (1)

mrjb (547783) | more than 8 years ago | (#15724128)

"Many photons before you went on this quest, but none returned. But you will."
"Why?"
"Because you are The One".

Re:Snippet describing how difficult it is ... (1, Offtopic)

MustardMan (52102) | more than 8 years ago | (#15724455)

Thanks for the cut and paste... keeps people from clicking on TFA. It's bad enough that fucking advertisement troll roland gets his shit posted here on slasdot... they actually gave him a blog on zdnet now!?!?!??? Dear God, next thing you know TrollAxor will be working for Fox News (well, that might be an improvement from O'Reilley).

But wait.... (0)

Anonymous Coward | more than 8 years ago | (#15723503)

I guess the array must have left behind by the hollywood crew who faked the moonlandings.... :D

Pretty cool... (0)

Anonymous Coward | more than 8 years ago | (#15723506)

If I RTFA correctly, Snell's Law is limited by quantum uncertainty as the normal approaches 90 degrees. Never realized that before, but it makes sense, because the Exclusion Principle would be violated momentarily at exactly 90 degrees. (But: is the Exclusion Principle even supposed to apply to photons?)

Re:Pretty cool... (2, Informative)

Beryllium Sphere(tm) (193358) | more than 8 years ago | (#15723635)

Nope, photons are bosons and not fermions. If the Pauli Exclusion Principle applied to photons then we wouldn't have lasers.

Seems a bit frivolous... (1)

freemywrld (821105) | more than 8 years ago | (#15723508)

Is it just me or does it seem that goal #2 is a bit excessive. Knowing the distance between the Earth and the moon to the point of a millimeter.. Exactly what does that gain us in, say, accuracy of experiements, etc.?

Re:Seems a bit frivolous... (3, Insightful)

calidoscope (312571) | more than 8 years ago | (#15723539)

Well if you read TFA from the Union-Trib, the whole point was getting enough accuracy to see if the orbit of the moon followed the predictions of General Relativity exactly. A deviation from those predictions would mean that General Relativity needs amending. The beauty of this experiment is that it is relatively inexpensive - the reflector is already on the moon.

Re:Seems a bit frivolous... (0)

Anonymous Coward | more than 8 years ago | (#15723945)

Well if you read TFA from the Union-Trib

Trib? What has a lesbian sex technique to do with the Moon? Are there lesbians on the Moon? If there are, then I say by all means, let's go back to the Moon, with some good cameras.

Re:Seems a bit frivolous... (1)

thePig (964303) | more than 8 years ago | (#15724283)

Many of the experiments which measured up in cms, ad many other data proved that for those ranges the theory is correct.
But as was the case of Newton, wherein his theories of gravity was proved right for a huge range of velocities/distances.

Only more experiments, in smaller ranges, would even put a question mark on the Einsteins theory of gravity.
If it holds up, well and good.
If not, time for change (either the experiment or the theory)

So, this experiment and millions of others are very useful indeed.

Ha! that's what they think... (0)

Anonymous Coward | more than 8 years ago | (#15724391)

Heh, every once in awhile the ferengi come around to raise and lower the reflectors on us for a big mind fuck.

I'd question whether 1 mm is even possible... (2, Informative)

msauve (701917) | more than 8 years ago | (#15724457)

Considering all the variables plus measurement accuracy.

1 mm at lightspeed is about 3.3 picoseconds. First, what photon detector has a rise time in that range? Second, atmospheric conditions will dynamically affect the measurement, I suspect with significantly more than a few picoseconds of noise. Tidal effects on both the Earth and the Moon will change the distance. Finally, what Time Interval Analyzer are you going to use? The SR620 [thinksrs.com] , one of the better units on the market, does 25 ps resolution, and accuracy is closer to 100 ps.

Re:I'd question whether 1 mm is even possible... (1)

Vellmont (569020) | more than 8 years ago | (#15724712)

With one measurement, you're totally correct. But using statistical techniques from multiple measurements you can cancel out all the random errors that occur. You can do the same thing using a GPS receiver and get centimeter accuracy from the at best 3 meter accuracy of GPS.

Boring.... (0)

Anonymous Coward | more than 8 years ago | (#15723511)

Just shooting the moon with a laser is boring.

Nuke The Moon [slashdot.org]

title? (2, Funny)

binarybum (468664) | more than 8 years ago | (#15723512)

must say that title is a bit vague. I was just outside last night getting bombarded with photons from the moon. I'm betting technology circa 1888 is capable of capturing photons coming from the mooon.

Re:title? (1)

evilviper (135110) | more than 8 years ago | (#15723815)

must say that title is a bit vague.

Yeah, surely you couldn't be bothered to read the short summary to figure out more specific info than the title can convey.

Really, give me a break. To make matters worse, you didn't even bother to suggest an alternative title. You're just making pedantic complaints.

Re:title? (1)

mgblst (80109) | more than 8 years ago | (#15724119)

Yeah, well at least he read the whole line. I just read the word catching, and can't seem to find any references to baseball. What madness it this?

Re:title? (1)

binarybum (468664) | more than 8 years ago | (#15724968)

Yeah, surely you couldn't be bothered to read the short summary to figure out more specific info than the title can convey.

    from the summary: "I also have up a summary, which contains additional details and pictures, if you just want to learn how difficult it is to capture photons back from the moon" sorry, I'm still at a loss - if their finding it difficult, perhaps they're just not sending enough photons - I can assure you it is no difficult task to capture photons back from the moon.

you didn't even bother to suggest an alternative title.
          oh man, what a great place this would be if I thought anyone cared about post-hoc title suggestions..
    here are just a few, " Local man hit in the eye with laser bounced off moon "
            "CHA "
    " Bouncing lasers off moon to test relativity"
    " Scientists bounce lasers off of Buzz Aldrin's lost vanity mirror"

The "Moon": A Ridiculous Liberal Myth (3, Funny)

Anonymous Coward | more than 8 years ago | (#15723523)

It amazes me that so many allegedly "educated" people have fallen so quickly and so hard for a fraudulent fabrication of such laughable proportions. The very idea that a gigantic ball of rock happens to orbit our planet, showing itself in neat, four-week cycles -- with the same side facing us all the time -- is ludicrous. Furthermore, it is an insult to common sense and a damnable affront to intellectual honesty and integrity. That people actually believe it is evidence that the liberals have wrested the last vestiges of control of our public school system from decent, God-fearing Americans (as if any further evidence was needed! Daddy's Roommate? God Almighty!)

Documentaries such as Enemy of the State have accurately portrayed the elaborate, byzantine network of surveillance satellites that the liberals have sent into space to spy on law-abiding Americans. Equipped with technology developed by Handgun Control, Inc., these satellites have the ability to detect firearms from hundreds of kilometers up. That's right, neighbors .. the next time you're out in the backyard exercising your Second Amendment rights, the liberals will see it! These satellites are sensitive enough to tell the difference between a Colt .45 and a .38 Special! And when they detect you with a firearm, their computers cross-reference the address to figure out your name, and then an enormous database housed at Berkeley is updated with information about you.

Of course, this all works fine during the day, but what about at night? Even the liberals can't control the rotation of the Earth to prevent nightfall from setting in (only Joshua was able to ask for that particular favor!) That's where the "moon" comes in. Powered by nuclear reactors, the "moon" is nothing more than an enormous balloon, emitting trillions of candlepower of gun-revealing light. Piloted by key members of the liberal community, the "moon" is strategically moved across the country, pointing out those who dare to make use of their God-given rights at night!

Yes, I know this probably sounds paranoid and preposterous, but consider this. Despite what the revisionist historians tell you, there is no mention of the "moon" anywhere in literature or historical documents -- anywhere -- before 1950. That is when it was initially launched. When President Josef Kennedy, at the State of the Union address, proclaimed "We choose to go to the moon", he may as well have said "We choose to go to the weather balloon." The subsequent faking of a "moon" landing on national TV was the first step in a long history of the erosion of our constitutional rights by leftists in this country. No longer can we hide from our government when the sun goes down.

MODERATORS! (0)

Anonymous Coward | more than 8 years ago | (#15723557)

Moderators please...mod this guy Funny!

I almost wet myself laughing while I was reading this.

Re:The "Moon": A Ridiculous Liberal Myth (1)

Mikya (901578) | more than 8 years ago | (#15723560)

I want the three minutes of my life it took to read that back.

Re:The "Moon": A Ridiculous Liberal Myth (0)

Anonymous Coward | more than 8 years ago | (#15723609)

You weren't going to use them anyway.

Re:The "Moon": A Ridiculous Liberal Myth (1)

Mikya (901578) | more than 8 years ago | (#15723777)

True enough :)

Re:The "Moon": A Ridiculous Liberal Myth (1)

FormOfActionBanana (966779) | more than 8 years ago | (#15723937)

Granted. Start any time.

Re: The "Moon": A Ridiculous Liberal Myth (1)

bhiestand (157373) | more than 8 years ago | (#15723977)

You, sir, are trying to spin the facts to spread blasphemy and heresy. It is well documented throughout numerous sections of the bible that God Himself created the Moon, and that all things Moon-Related are God-Related. How can you state that light "just randomly emits" from the Moon? That the nuclear reactors which power this "just randomly work"? Clearly there is an intelligence far beyond us at work here. Only God could create something so massive with such powerful light-reflecting abilities, perfectly designed and positioned for the pleasure and needs of humanity! Imagine where we would be had God not made things so perfectly for us. All of the evidence points to one simple, logical, and divine solution: Intelligent Reflection.

Re:The "Moon": A Ridiculous Liberal Myth (1)

IHC Navistar (967161) | more than 8 years ago | (#15723997)

Oh dear God, someone needs to pull the emergency brake on that poor man's imagination. Like, right now...

Few things things, such as old people driving large cars, California, or Chinese food, scare me. But when I read stuff like this, I think that some people (such as the poor soul who wrote this) DESERVE to be dragged into the street and shot.....several times..... for the good of humanity.

I think this idiot embodies the term LUNATIC.

-----

Sig Sauer

Re:The "Moon": A Ridiculous Liberal Myth (1)

4D6963 (933028) | more than 8 years ago | (#15724189)

I think that some people (such as the poor soul who wrote this) DESERVE to be dragged into the street and shot.....several times..... for the good of humanity

One who would DESERVE that would be someone who would be gullible enough to think that the guy in question was being serious, in other words, the subtle person that you are ;-)

question (1)

macadamia_harold (947445) | more than 8 years ago | (#15723536)

how and why physicists from UCSD are using lasers to send light pulses in direction of an array of reflectors installed on our moon in 1969 by Neil Armstrong and Buzz Aldrin.

How did Neil Armstrong and Buzz Aldrin install reflectors on the moon from a soundstage in Burbank?

Re:question (5, Funny)

Anonymous Coward | more than 8 years ago | (#15723572)

How did Neil Armstrong and Buzz Aldrin install reflectors on the moon from a soundstage in Burbank?

They didn't. The Burbank soundstage looked fake, so they had to build one on the Moon.

The Burbank Landing is a hoax. We never went to Burbank. Going to Burbank requires resources and capabilities far exceeding those we possess or will be able to possess in the foreseeable future.

Re:question (0)

Anonymous Coward | more than 8 years ago | (#15723623)

Also, more flying machines have been destroyed while attempting to land in Burbank [ntsb.gov] than while attempting to land on the Moon.

Re:question (1)

Amazing Quantum Man (458715) | more than 8 years ago | (#15723774)

Do not be fooled by the phrase "Beautiful Downtown Burbank". Burbank is a strange and hostile environment, unfriendly to human survival.

At least... (1)

tubapro12 (896596) | more than 8 years ago | (#15723547)

...this should theoritcally put to rest the conspiracy theories having to do with the Apollo mission and a Western US military base of which the government doesn't acknowledge.

Re:At least... (0)

Anonymous Coward | more than 8 years ago | (#15723871)

Western US military base

Is that a military base with cowboys and indians and sheriffs and bandits and stuff?

Re:At least... (0)

Anonymous Coward | more than 8 years ago | (#15724815)

why should it? because a couple egg heads in some basement lab somewhere said they measured something that only their intruments are senstive enough to measure?

this is only proof to people that already believe, it's no kind of proof that matters to the common man

it's just more of the same, "trust us and believe what we tell you"

Keep experiments running (3, Interesting)

MichaelSmith (789609) | more than 8 years ago | (#15723559)

The LR^3 retroreflector featured here was part of the ALSEP station on several of the apollo missions. In the years since these missions the ALSEP stations have been shut down. The reflectors are passive devices and don't have an off switch, which is why they are still working.

In particular the seismonitors which were a part of each system could still be operating today, and delivering new scientific results.

I think this article is an example of why experiments should not be shut down before they really stop working.

Re:Keep experiments running (0)

Anonymous Coward | more than 8 years ago | (#15724033)

So, ALSEP is now ASLEEP? Wake it up!

Narrow output pulse (2, Informative)

Animats (122034) | more than 8 years ago | (#15723617)

What's new here is how short a pulse they're sending. The light pulse is only about 0.1ns long (the article says "an inch"), which is actually quite good for a big pulsed laser. That's why they get so few photons back.

On the other hand, detecting single photons is no big deal; that's what photomultipliers are for.

It's not like detecting a single photon, alone! (4, Informative)

Herve5 (879674) | more than 8 years ago | (#15723884)

Actually the said 'single photon' that comes back from the retroreflector arrives with millions of others coming from everywhere around (from our atmosphere to the neighboring moon land), and is totally unvisible within this "noise".
The issue here consists in estimating the presence of photons *below noise level*, which you only can do by statistically studying series of shots. (or, in a simplified form: by averaging hundreds of shot results, you lower the noise and end in seeing a small peak around the time where you expected the photons to come back)

Incidentally these experiments have been and are done today routinely in many observatories worldwide; the originality here may be an increase of precision but the mehod is very classical. Here in France I have a neighbor observatory which organizes visits to this setup, for instance (the last photo of http://www.bdl.fr/fr/ephemerides/astronomie/Promen ade/pages2/269.html [www.bdl.fr] shows a lunar shot... within an entirely french page, sorry)

I must register a strong objection (0)

Anonymous Coward | more than 8 years ago | (#15723634)

to the use of the phrase "our moon" in the article. While I realize that most of the Slashdot "readership" (given the relevance of posts to the articles, I hesitate to use the word) is USian, and that you fellows believe you own the moon by right of discovery, those of us in Canada beg to differ.

The moon does not belong to the States by discovery. It was discovered by the first hairy ape that looked up at night. We always knew where it was, you guys just got there first.

As intellectual leaders of a sort, or at least as the nearest thing down there, I would think that the slashdot editors would feel some bit of "white man's burden" to set a good example and make sure such phrases don't creep into the stories.

Re:I must register a strong objection (1)

gomoX (618462) | more than 8 years ago | (#15723708)

Those of us in the rest of the world understand that when someone says "our moon" they are actually including you and me.

Re:I must register a strong objection (0)

Anonymous Coward | more than 8 years ago | (#15723709)

[I must register a strong objection] to the use of the phrase "our moon" in the article. While I realize that most of the Slashdot "readership" (given the relevance of posts to the articles, I hesitate to use the word) is USian, and that you fellows believe you own the moon by right of discovery, those of us in Canada beg to differ.

I'm also a Canadian. I understand what you're saying: in proximity to the mention of the 1969 Apollo 11 landing, the phrase "our moon" in the summary does seem to sound US-possessive. However, I'd give the Slashdot editors the benefit of the doubt. The phrase "our moon" is broadly understood to mean "the Earth's moon" in most contexts.

Re:I must register a strong objection (0, Flamebait)

hunterx11 (778171) | more than 8 years ago | (#15723710)

First the U.S. doesn't respect the rights of brown people, and now we don't respect the dignity of little green men!

Seeing the surface (1, Insightful)

FractusMan (711004) | more than 8 years ago | (#15723723)

This is slightly off topic, but related to sending light and receiving it. From the Earth's surface, just how good of a resolution can we get of the lunar surface? I mean, can we put the 'We never landed on the Moon' theories to rest simply by pointing a good telescope up there and looking for footprints/lunar rover tracks?

Re:Seeing the surface (4, Informative)

GoulDuck (626950) | more than 8 years ago | (#15723861)

how good of a resolution can we get of the lunar surface? I mean, can we put the 'We never landed on the Moon' theories to rest simply by pointing a good telescope up there and looking for footprints/lunar rover tracks?
I have the admit, that this is just something I read somewhere, but we can't see that small details on the moon. The Earths atmosphere will make the pictures to blurry (even with these auto-compensating-corrective lenses they use) and you can't zoom that much. Pointing Hubble at the moon is also a no-go, because it was made to look at objects far far away.

Resolution of Hubble (4, Informative)

Circlotron (764156) | more than 8 years ago | (#15724067)

Hubble can see items of 50 metres size in UV wavelength on the moon's surface. Seems it's resolving power is related to the wavelength of the "light" it is using, same as in photolithography used in producing nanometre scale details on semiconductors. http://www.newscientistspace.com/article.ns?id=dn7 880 [newscientistspace.com]

Re:Resolution of Hubble (1)

GoulDuck (626950) | more than 8 years ago | (#15724150)

Thank you for the link!

Wouldn't silence the idiots (1)

CurtMonash (986884) | more than 8 years ago | (#15723928)

They'd claim the telescope was controlled, or the results misreported.

How would they work out the distance? (1)

drsquare (530038) | more than 8 years ago | (#15723736)

Considering neither the Earth or the Moon have a perfectly flat surface, millimetre-precision reading will only be useful if they know to the millimetre how far away the mirrors are from the centre of the Moon.

Re:How would they work out the distance? (1)

GoulDuck (626950) | more than 8 years ago | (#15723844)

If they know the height of the refelctor on the moon and the height of their laser, then you will be able to calculate the distance between two other points - I guess. But I think the most importain part is that we know the distance over time and then it dosen't matter where you messure from.

Other earth-moon projects might rely on knowing the distance, but then they just have to calculate it.

Re:How would they work out the distance? (1)

torpor (458) | more than 8 years ago | (#15724015)

You misunderstand. The 'millimeter' rating is only that: a rating. It states that they can measure, 'to the millimeter', the distance between the reflector and the laser. Of course, there will be other measurements relative to this figure which will be important - the shift between subsequent measurements, for example.

Problems with this article (1, Funny)

Antony-Kyre (807195) | more than 8 years ago | (#15723808)

Gravity accelerates all objects at the same rate? What does this mean? My understanding is that two objects of difference masses will fall at different rates. More massive objects will reach their destination quicker than the less massive objects. This has been mathematically proven. I even had a physics teacher help me write out the hypothetical trials.

(As to whether hotter objects fall faster than colder objects, I don't know yet. That's something else I've been wondering.)

Re:Problems with this article (4, Informative)

monoqlith (610041) | more than 8 years ago | (#15723854)

Are you serious? All objects will fall to the earth at the same rate at the same distance.
This is pretty basic. It's one of the first observations of classical physics.

F = G * m(1) * m(2) / (r^2) = m(1) * a

(equate Newton's second law with Newton's theory of gravitation where a is acceleration, m1 is the body being accelerated, and m2 is the massive body m1 is being accelerated towards.)

If you cancel m1 on both sides you get G * m2 / (r^2) = a

This means that the gravity of a massive body is always going to accelerate an orbiting body at the same rate if that body remains at the same distance. So, two masses let go at the same height above the earth will fall to the earth at the same rate (9.81 m/s^2). They each have different *forces* responsible for that acceleration, but since m*a = F, that extra force for the more massive object is needed to accelerate it at the same rate.

Re:Problems with this article (1)

hankwang (413283) | more than 8 years ago | (#15723971)

Don't bite the trolls.

Re:Problems with this article (1)

eyewhin (944625) | more than 8 years ago | (#15724014)

Care to enlighten us with your great discovery? I would have to say your physics teacher was actually a lit major who was masquerading. You've been duped.

Re:Problems with this article (2, Funny)

Antony-Kyre (807195) | more than 8 years ago | (#15724043)

Below are some of the formulas. I haven't been taught how to derive the bottom one. If you do a couple trials, objects A and C in trial one, and objects B and C in trial two, with A being more massive than B, with center of gravities being dropped from the same distance, the more massive one will reach it's destination "sooner" than the less massive one. This is math. It's provable. I need to go to sleep now, so maybe later I'll be posting the complete example with trials.

Force of Gravity = 6.67 * 10- mass1 * mass2 / distance

distance = ½ * acceleration * time
time = (2 * distance / acceleration) ^ ½

Re:Problems with this article (1)

lexarius (560925) | more than 8 years ago | (#15724433)

To get acceleration from a force, use Force = mass * acceleration. Equating the two cancels out the mass of the falling object. The acceleration of the object depends only on the mass of the other object. In other words, massive objects fall with greater force because a greater force is required to accelerate them. If it somehow seems strange that only the mass of one of the objects affects acceleration, realize that it works both ways. The earth's acceleration towards a falling object does not depend on the mass of the earth, only on the mass of the object. It accelerates towards it as much as the other light falling object does, which is to say approximately zero.

Re:Problems with this article (1)

Antony-Kyre (807195) | more than 8 years ago | (#15724945)

(Hopefully I didn't make any typos while copying this from a piece of paper.)

Object A is 2kg
Object B is 1kg
Object C is 1kg

Trial 1: The center of gravity of Object A is 10m from the center of gravity of Object C.
Trial 2: The center of gravity of Object B is 10m from the center of gravity of Object C.

Force of Gravity = 6.67 * 10- mass1 * mass2 / distance

Trial 1: Fg = 6.67 * 10- * 2kg * 1kg / (10m) = 1.334*10^-12 Newtons
Trial 2: Fg = 6.67 * 10- * 1kg * 1kg / (10m) = 6.67*10^-13 Newtons

distance = ½ * acceleration * time
time = (2 * distance / acceleration) ^ ½

Trial 1: t = (2 * 6.67m / 1.334*10^-12m/s) ^ ½ = 10^6 seconds
Trial 2: t = (2 * 5m / 6.67*10^-13m/s) ^ ½ = 1.22*10^6 seconds

Re:Problems with this article (1)

Geoff St. Germaine (819751) | more than 8 years ago | (#15724582)

If you aren't making a joke, then your physics teacher should be fired.

As has already been posted, due to the equivalence of inertial mass and gravitational mass, the object mass in the equation you have posted cancels. Also, if you really did do an experiment then I would question your methods. How did you account for air resistance. A 1992 article in Physical Review Letters details an experiment performed in an ultra-high vacuum where the universality of the free fall acceleration of objects in a gravitational field was verified to a few parts in 10^10. I'm assuming that this experiment was considerable more accurate than yours.

Of course, I hope that you are making a joke of some sort.

Wouldn't... (1, Interesting)

Anonymous Coward | more than 8 years ago | (#15723859)

... the reflector be covered in dust now? And what has 30+ years of solar wind done to the reflector?

Re:Wouldn't... (1)

mattavian (988882) | more than 8 years ago | (#15724375)

Actually the moon is a pretty static place. No air means no wind which means all the 'dust' stays where it is. Armstrongs original footprints should still be there (unless the lander wiped them out on take off.

captain (0)

Anonymous Coward | more than 8 years ago | (#15723935)

I need more power!

-m10

Not yours! (2, Funny)

badzilla (50355) | more than 8 years ago | (#15723943)

...installed on our moon in 1969...

Hey! Just cause you Yanks got there first doesn't make it yours, m'kay?

but some own parts of it already (0)

Anonymous Coward | more than 8 years ago | (#15723967)

http://www.lunarregistry.com/ [lunarregistry.com]

(now if something, this type of shit needs to be stopped)

-m10

Re:Not yours! (1)

GrumblyStuff (870046) | more than 8 years ago | (#15724966)

Hey, snooze you lose. Sucker. ;D

Obligatory movie qoute (2, Funny)

agw (6387) | more than 8 years ago | (#15723970)

Fire the "L.A.S.E.R."!

Quite far from difficult, can be done by almanyone (3, Interesting)

Ancient_Hacker (751168) | more than 8 years ago | (#15724198)

It's not all that hard to bounce photons off the Moon. The US Army Signal Corps did it in 1947, using very mediocre WWII radar sets. Radio amateurs have been doing it since around 1960, with limited equipment, skills, and very limited transmitter power.

What's difficult is doing it with nanosecond resolution. That requires very wide bandwith antennas and receivers, which also let in a lot of wide band background noise.

Re:Quite far from difficult, can be done by almany (1)

LouisZepher (643097) | more than 8 years ago | (#15724914)

It's not all that hard to bounce photons off the Moon.

Hell, the sun's been doing it for a few billion years using a working fusion reactor. Seems to me that beats out US physicists and engineers by a long shot.

obviously a FAKE... (0)

Anonymous Coward | more than 8 years ago | (#15724265)

as they never landed on the moon, they can't have build up any reflectors, so, there can not be a reflected photon to catch.

cogito ergo sum.

sorry, HAD to write this. Resistance is futile. ::o)

A step in the right direction (1)

mattavian (988882) | more than 8 years ago | (#15724388)

I think we should keep a few hundred lasers trained on the moon at all times... just in case. (cue background music)

This is not news... (0)

Anonymous Coward | more than 8 years ago | (#15724618)

I inspected the Auroral tracking station in Canberra Australia, in 1993. They even fired the laser up for us and explained that they bounced the laser off reflectors left on the moon.

The laser pulsed 10 times a second and I vaguely recall them saying it measured the distance to within a few centimetres.

They had been running this for quite some years before I saw it I am quite sure.

Just out of curiosity, (1)

nowhere.elysium (924845) | more than 8 years ago | (#15724920)

how does this affect our understanding of spatial dynamics? I only understand physics insofar as it affects 3D graphics (specifically, light and particle dynamics), so you'll have to forgive my relative ignorance. I just find myself wondering if it's going to be a minor amendment to the current theories, or a complete re-write. If it's the second option, I'll just sit and wait for the maths patches for my various 3D software tools, shall I? Also, on a totally puerile note: you can tell that they're physicists, and not web designers, can't you? Their page http://physics.ucsd.edu/~tmurphy/apollo/apollo.htm l [ucsd.edu] looks like it was designed around the same era the rocket they're named from was launched...

Yeah! That's my wife's telescope! (1)

wwphx (225607) | more than 8 years ago | (#15724965)

Well, she's the main operator. She also works for the Apollo program now, and I occasionally sit on the catwalk watching for airplanes that wander into the airspace while the laser is "shining."
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