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Catching Photons Coming from the Moon
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."
You can just make out the begin of what looks like the word "chair"
Letter To Iran
"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.
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.
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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!)
.. 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.
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
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.
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.
A Shadeless room is a brighter room.
Its being further out might have somthing to do with all those pesky scientists bouncing photons off it.
cat
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.
http://michaelsmith.id.au
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.
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.
Philosophy.
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 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 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.
The credible conspiracy theory: Send the humans into orbit, camp in orbit while the robot fetches the samples, reunite humans with the 'bot, then land as heroes.
Obama likes poor people so much, he wants to make more of them.
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.
Nope, photons are bosons and not fermions. If the Pauli Exclusion Principle applied to photons then we wouldn't have lasers.
http://science.slashdot.org/science/06/07/13/16542 00.shtml 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 we will not know until the original tapes can be examined.
Obama likes poor people so much, he wants to make more of them.
There had already been a few robot landers. Three Rangers, which crashlanded; five Surveyers (1966-68) which successfully softlanded. The Apollo 12 astronauts visited the Surveyer 3 site.
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.
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".
n ade/pages2/269.html shows a lunar shot... within an entirely french page, sorry)
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/Prome
Herve S.
Hey! Just cause you Yanks got there first doesn't make it yours, m'kay?
"Don't belong. Never join. Think for yourself. Peace." V.Stone, Microsoft Corporation
Fire the "L.A.S.E.R."!
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
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
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.
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, one of the better units on the market, does 25 ps resolution, and accuracy is closer to 100 ps.
"National Security is the chief cause of national insecurity." - Celine's First Law
In 1980 I visited the MOBLAS-5 Yarragadee station in the Western Australia outback, which was custom-built for this purpose. MOBLAS meant MOBile LASer, and as you can see from the picture it is built in a trailer. But the equipment does not move. The site has clear night skies and no geological or human interference. And results from one location over time are valuable. It was beautiful and eerie to see the green laser beam. Even though the air was clear you could see it when standing around the pad. It seemed to last longer than the tiny fraction of a second it pulsed. At the time the operators would get a visual feedback from their instruments on who big the return signal was. And they would tweak the telescope tracking as required to get good returns. Tapes of the results were then sent back to NASA. I assume this is all automated now. Those guys looked extremely bored.
BTW, notice how big the empty tarmac is around the trailer. I was told NASA wanted a 100 by 100 foot pad and they mistakenly got a 100 by 100 metre pad, making it about 10 times bigger than they needed!