-5
$\begingroup$

Until today, I had never once heard anyone ever mention these "reflectors" which apparently were placed on the Moon at the landing site in order to verify from Earth that humans were there.

On https://en.wikipedia.org/wiki/Moon_landing#Historical_empirical_evidence , it says:

Many conspiracists hold that the Apollo Moon landings were a hoax;[76] however, empirical evidence is readily available to show that human Moon landings did occur. Anyone on Earth with an appropriate laser and telescope system can bounce laser beams off three retroreflector arrays left on the Moon by Apollo 11,[77] 14 and 15, verifying deployment of the Lunar Laser Ranging Experiment at historically documented Apollo Moon landing sites and so proving equipment constructed on Earth was successfully transported to the surface of the Moon.

It further links to: https://en.wikipedia.org/wiki/Lunar_Laser_Ranging_experiment

However, the second link doesn't mention anything about the purpose of this being to verify that humans landed on the Moon. It goes on to mention the year "1962", which is before any humans had allegedly set foot on the Moon, and apparently they could still do the "experiment" without any reflectors in place, so what does this really prove?

This could become a conspiracy theory in itself; that they added this story about the reflectors long after the fact. However, I'm not saying anything -- I'm just wondering what the point of them was and why this has never been brought up as a way to verify the moon landings, if almost anyone can do it with some equipment.

$\endgroup$
  • 6
    $\begingroup$ There is no way anyone can know why you haven't heard of this, and it is 100% incorrect that "it has never been brought up". For example, they are mentioned in our canonical "How do we know the Moon landings are real" answer: space.stackexchange.com/q/28172/6944 $\endgroup$ – Organic Marble Apr 25 at 17:51
  • 3
    $\begingroup$ "Why haven't I heard of this before" is an unanswerable question, since it has to do with your specific education. The information about the LLRE experiments is extensively available, has been talked about extensively in communications and media at the time. There are transcripts discussing their placement on the moon in the Apollo record. Many papers have been written about the results from using them to measure distance to the moon. Also, this sounds like part of a moon-landing conspiracy theory. Thus the downvote. I suggest removing the conspiracy stuff and asking a specific question $\endgroup$ – Dan Hanson Apr 25 at 17:51
  • 7
    $\begingroup$ I’m voting to close this question because no one can know why you haven't heard of this. $\endgroup$ – Organic Marble Apr 25 at 17:58
  • 1
    $\begingroup$ I've known about the retro reflectors since I was a kid, from some kid's educational book about the solar system. I'm willing to bet there are plenty other things neither of us have ever heard of that are just as interesting as the reflectors. $\endgroup$ – BMF Apr 25 at 18:42
  • 2
    $\begingroup$ relevant XKCD -- from October 31st 2014. They weren't "placed on the Moon at the landing site in order to verify from Earth that humans were there" They were to improve the accuracy of the experiment. The equipment needed to perform the experiment is still pretty sophisticated. $\endgroup$ – JCRM Apr 25 at 19:17
8
$\begingroup$

However, the second link doesn't mention anything about the purpose of this being to verify that humans landed on the Moon. It goes on to mention the year "1962", which is before any humans had allegedly set foot on the Moon, and apparently they could still do the "experiment" without any reflectors in place, so what does this really prove?

As JCRM notes, the purpose of the retroreflectors was not to verify that humans have landed on the moon. At the time, almost no one doubted that humans had landed on the moon; moon landing denial is a relatively recent trend promoted by grifters and attention-seekers with no respect for truth. The purpose of the reflectors was to accurately measure the distance to the moon.

Re-read the paragraph mentioning a 1962 experiment more carefully:

The first successful tests were carried out in 1962 when a team from the Massachusetts Institute of Technology succeeded in observing laser pulses reflected from the Moon's surface using a laser with a millisecond pulse length. Similar measurements were obtained later the same year by a Soviet team at the Crimean Astrophysical Observatory using a Q-switched ruby laser. Greater accuracy was achieved following the installation of a retroreflector array on July 21, 1969, by the crew of Apollo 11, and two more retroreflector arrays left by the Apollo 14 and Apollo 15 missions have also contributed to the experiment.

In other words, a ranging laser was bounced off the bare surface of the moon in 1962, and the arrays placed by the Apollo missions allowed similar experiments to be conducted more accurately.

It's not remarkable that you, or anyone else, hadn't heard of the laser retroreflectors; they were one of many independent scientific experiments placed during the Apollo missions. They certainly weren't a story added after the fact; they were called out in the press kit publicly released a couple of weeks before the Apollo 11 launch:

During their two hours and 40 minutes on the surface, Armstrong and Aldrin will gather geologic samples for return to Earth in sealed sample return containers and set up two scientific experiments for returning Moon data to Earth long after the mission is complete. One experiment measures moonquakes and meteoroid impacts on the lunar surface, while the other experiment is a sophisticated reflector that will mirror laser beams back to points on Earth to aid in expanding scientific knowledge both of this planet and of the Moon.

And also in the the Apollo 11 Mission Report delivered in November of 1969:

Both crewmen evalu­ated their mobility on the lunar surface, deployed the passive seismic and laser retro-reflector experiments, collected about 47 pounds of lunar material, and obtained photographic documentation of their activities and the conditions around them.

These are just two of many Apollo-era documents that mention the retroreflector experiments.

| improve this answer | |
$\endgroup$

Not the answer you're looking for? Browse other questions tagged or ask your own question.