The Most Important Thing Armstrong Left on the Moon



The most famous thing Neil Armstrong left on the moon 35 years ago is a footprint, a boot-shaped depression in the gray moondust. Millions of people have seen pictures of it, and one day, years from now, lunar tourists will flock to the Sea of Tranquility to see it in person. Peering over the rails … "hey, mom, is that the first one?" Will anyone notice, 100 feet away, something else Armstrong left behind? Ringed by footprints, sitting in the moondust, lies a 2-foot wide panel studded with 100 mirrors pointing at Earth: the "lunar laser ranging retroreflector array." Apollo 11 astronauts Buzz Aldrin and Neil Armstrong put it there on July 21, 1969, about an hour before the end of their final moonwalk. Thirty-five years later, it's the only Apollo science experiment still running.

University of Maryland physics professor Carroll Alley was the project's principal investigator during the Apollo years, and he follows its progress today. "Using these mirrors," explains Alley, "we can 'ping' the moon with laser pulses and measure the Earth-moon distance very precisely. This is a wonderful way to learn about the moon's orbit and to test theories of gravity." Here's how it works: A laser pulse shoots out of a telescope on Earth, crosses the Earth-moon divide, and hits the array. Because the mirrors are "corner-cube reflectors," they send the pulse straight back where it came from. "It's like hitting a ball into the corner of a squash court," explains Alley. Back on Earth, telescopes intercept the returning pulse--"usually just a single photon," he marvels. The round-trip travel time pinpoints the moon's distance with staggering precision: better than a few centimeters out of 385,000 km, typically.

Targeting the mirrors and catching their faint reflections is a challenge, but astronomers have been doing it for 35 years. A key observing site is the McDonald Observatory in Texas where a 0.7 meter telescope regularly pings reflectors in the Sea of Tranquility (Apollo 11), at Fra Mauro (Apollo 14) and Hadley Rille (Apollo 15), and, sometimes, in the Sea of Serenity. There's a set of mirrors there onboard the parked Soviet Lunokhud 2 moon rover--maybe the coolest-looking robot ever built.

In this way, for decades, researchers have carefully traced the moon's orbit, and they've learned some remarkable things, among them:

(1) The moon is spiraling away from Earth at a rate of 3.8 cm per year. Why? Earth's ocean tides are responsible.

(2) The moon probably has a liquid core.

(3) The universal force of gravity is very stable. Newton's gravitational constant G has changed less than 1 part in 100-billion since the laser experiments began.
Physicists have also used the laser results to check Einstein's theory of gravity, the general theory of relativity. So far, so good: Einstein's equations predict the shape of the moon's orbit as well as laser ranging can measure it. But Einstein, constantly tested, isn't out of the woods yet. Some physicists (Alley is one of them) believe his general theory of relativity is flawed. If there is a flaw, lunar laser ranging might yet find it.

NASA and the National Science Foundation are funding a new facility in New Mexico, the Apache Point Observatory Lunar Laser-ranging Operation or, appropriately, "APOLLO" for short. Using a 3.5-meter telescope with good atmospheric "seeing," researchers there will examine the moon's orbit with millimeter precision, 10 times better than before.







The Laser Ranging Retroreflector experiment


The Apollo 11 lunar laser ranging retroreflector array.

The Laser Ranging Retroreflector experiment was deployed on Apollo 11, 14, and 15. It consists of a series of corner-cube reflectors, which are a special type of mirror with the property of always reflecting an incoming light beam back in the direction it came from. A similar device was also included on the Soviet Union's Lunakhod 2 spacecraft. These reflectors can be illuminated by laser beams aimed through large telescopes on Earth. The reflected laser beam is also observed with the telescope, providing a measurement of the round-trip distance between Earth and the Moon. This is the only Apollo experiment that is still returning data from the Moon. Many of these measurements have been made by McDonald Observatory in Texas. From 1969 to 1985, they were made on a part-time basis using the McDonald Observatory 107-inch telescope. Since 1985, these observations have been made using a dedicated 30-inch telescope. Additional measurements have been made by observatories in Hawaii, California, France, Australia, and Germany.

Laser beams are used because they remain tightly focused for large distances. Nevertheless, there is enough dispersion of the beam that it is about 7 kilometers in diameter when it reaches the Moon and 20 kilometers in diameter when it returns to Earth. Because of this very weak signal, observations are made for several hours at a time. By averaging the signal for this period, the distance to the Moon can be measured to an accuracy of about 3 centimeters (the average distance from the Earth to the Moon is about 385,000 kilometers).

The Laser Ranging Retroreflector experiment has produced many important measurements. These include an improved knowledge of the Moon's orbit and the rate at which the Moon is receding from Earth (currently 3.8 centimeters per year) and of variations in the rotation of the Moon. These variations in rotation are related to the distribution of mass inside the Moon and imply the existence of a small core, with a radius of less than 350 kilometers, somewhat smaller than the limits imposed by the passive seismic and magnetometer experiments. These measurements have also improved our knowledge of changes of the Earth's rotation rate and the precession of its spin axis and have been used to test Einstein's theory of relativity.

every time these claims are posted on ats,i feel so downhearted,its so embarrassing for this site,its been done over and over,and it seems the governments plan to dumb down the education has worked,all the facts these people use are just from bad science or ignorance of facts,yes they have high res pictures of the Apollo landing site.this subject just isn't worth any more energy but i was so surprised by all of the posts from people thinking it didn't happen.

Your programed buddy

I would like to counter some points raised so far, i do not dispute the reason why there are no stars in the pictures, that makes sense to anyone who has a basic understanding of photography. In regards to the van allen belt, i believe it was in1996 when the space shuttle ascended to a distance of approximately 600miles from the 1st belt at which point the astronauts reported beams of bright light passing through the craft, their suits, their skulls finally hitting the retinas of their closed eyes. From this mission NASA stated that the van allen belt was a greater danger to the astronauts than originally thought. The depth of the belt would require more than just a couple of hours travel to pass through meaning dangerous levels of exposure would have had some form of impact on any astronaut passing through. None such effects were reported. To whoever stated that it is an embarresment to discuss this subject is clearly missing the point, if there was even one anomaly in the official record of the greatest event in human history then it should be discussed thouroughly, as there is NO conclusive proof of the sucess of the apollo missions one must keep an open mind to the possibility we have been lied to. Scientists will verify that moon rock is virtually identical to earth based rocks, with minor differences that could be easily explained by treatment in a vacuum chamber. The mirror that has been placed could have easily been placed by an unmanned probed or a surrogate manned mission which did not involved the known apollo astronauts. No one has managed to provide a satisfactory reason for the deception in producing the earth shot from the capsule window, surely if this had an innocent purpose the astronauts would have laughed off such an accusation and provide a suitable explanation? The reactions displayed do not demostrate innocent practice. Again, please explain this.....surely THIS is more of an embarresment to the american people than a group like us discussing anomalies and conflicting evidence of the official version of events? To ignore this evidence without adequate scrutiny is naive and against common sense. The pictorial record of the apollo mission is replete with seemingly glaring continuity errors of potentially whistleblowing proportions, to ignore or explain away this reality is whitewashing the fact these questions must be asked and begs the question why such anomalies exist?

To become angered by discussion of this issue is something i do not understand, this is a valid debate and one i strongly encourage to continue as long as these anomalies remain unexplained.

In my opinion the reason these anomalies or errors exist is because of documented evidence of UFO's in space, so they practice whatever fishy business they do to cover it up. Also while many will take offense to this, i honestly believe that the entire "faked moon landing" conspiracy was introduced as a way to discredit conspiracy theorists because it's so ridiculous. The science just isn't on your side and in my opinion using astronauts cherry picked reactions when asked a ridiculous question is hardly evidence of a hoax on such a worldwide scale.

I'm a very open minded person and i trust the government about as little as most people on this site, but this just doesn't seem to have any credible evidence at all that the landing was faked. Motive isn't really there other than to pull one over on us, and as said earlier, the Russians (or any other country around the world) would not have stood for this had they gotten even a shred of evidence that the landing never took place.

Maybe i'm mistaken but your argument basically rests on the perceived safety of this van allen belt? If that's all you've got i'm going to have to side with scientists.

it is interesting how you describe the hoax theory as ridiculous yet seem to endorse the seemingly more ridiculous theory that these blatant attempts at fakery is to cover up ufo encounters, could it not be possible that these fanciful tales of alien encounters could exist to detract from the far more believable theory that the mission was hoaxed? It is clear from the footage i have referenced that the astronauts are in fact in low earth orbit when they claim to be half way to the moon, the time and date from the atomic clock are shown in the video. It is impossible for them to be where they say they are, that is the smoking gun. The van allen belt explanation is merely common sense.

The landing on the moon is just as fake as how stupid we humans are to destroy our own world by pollution.

So we've been there for sure.

Pictures will come up eventually, im sure.

Welcome eyeofrah

I am not sure i agree with you though, as consumers we have little choice in the practices that exist that are the causes of pollution. as people we live under pre existing systems which perpetrate the production of waste and pollution, we can only do our part as individuals until suitable systems are in place to facilitate a more ethical system of waste production and managment.

Back to the point, man may well have been to the moon but i believe the apollo program was for show only. I have mentioned the possibility of a surrogate program that may have existed outside of public scrutiny. There are simply too many anomalies in the apollo program to discount and i have yet to read any worthy attempt to do so on this thread or elsewhere.

Welcome again and i hope you enjoy your time here

that really isn't an argument, that's just going in circles. the evidence of UFOs in our solar system is pretty substantial IMO but id rather not get into it now.


this i cannot explain, but im not a scientist or physicist, nor have i really invested much time in investigating this incident. ill concede this as fishy business, but i don't understand how you can come to such a conclusion. not to sound like an MK-ultra pawn, but there could be a number of explanations which could allude to other questionable actions, most of which i probably couldn't conceive.


common sense? really? All i can find are reports of either the radiation being manageable or life destroying. Again, i'm not a scientist or astro-physicist, but anytime i come across someone saying the van allen belt is impossible to penetrate its always followed by "and thats why the moon landing was faked" so i'm a bit weary of that information. But thats not to say that i can't be swayed by sound science. The problem with knowing the truth about things we cant measure ourselves is we're left to filter out information from sources we don't trust then come to our own conclusions. this leads to a very subjective reality IMO and is the problem with truth today.

in summary: I'm really not convinced. personally i see the evidence as greatly stacked against you, and while i can't explain the astronauts miss-representing their location (or if they even did in the first place) i can safely say that everything else seems pretty wrapped up. Don't forget, if you saw a video on the internet, take it with a grain of salt.

i do hate arguing for the mainstream....

OK, so how about the absolutely BLATANT inconsistency of the Apollo 11 astronauts calling the moon "GREY and looking like PLASTER OF PARIS - NO COLOR" from 60 miles above it. We now know that that is NOT TRUE! To me that fact alone proves a conspiracy.