
The lunar laser ranging experiment is still going 50 years later - sohkamyung
https://spectrum.ieee.org/the-institute/ieee-history/one-apollo-11-experiment-is-still-going-50-years-later
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NeedMoreTea
I always liked the story of the Lunokhod 1 - the first of the two Soviet Lunar
Rovers. Both had reflectors for laser ranging, but Lunokhod 1 was carelessly
misplaced in the early 1970s. So no more ranging until 2010 when the NASA
reconnaissance orbiter found it again. They didn't lose the other one. :)

I think one of the Lunokhods still holds the record for the furthest ever
travelled by an extra terrestrial vehicle.

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gonmad
Lunakhod 1 was still responding in 2013 (40 years later) thanks to the NASA
LRO (Lunar Reconnaissance Orbiter). French website, as it was a (secret)
collaboration between Russians and the CNES who provided the retroreflector:
[https://sciences-techniques.cnes.fr/fr/web/CNES-
fr/10757-st-...](https://sciences-techniques.cnes.fr/fr/web/CNES-
fr/10757-st-2013-lunakhod-repond-40-ans-apres.php)

~~~
NeedMoreTea
Thanks for that, I'd never heard of the French collaboration before.

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vermontdevil
You would think the reflectors being on the moon would shut up the “moon
landings were faked” crowd.

~~~
feintruled
Alas, that's not how it works. Any video you could show of the laser
experiment would also be faked. Even if you were to set them in front of the
equipment, that'd be faked too. I often wonder as a thought-experiment what
would happen if you bundled them onto a Musk style space tourism rocket and
flew them to the moon to see the flag (for a bonus they can look back to see
the spherical Earth) and then back, would they even then believe the
conspiracy or their lyin' eyes?

(Then I catch myself on and realise it wouldn't even theoretically be worth
wasting all that effort and money on someone so determined to be willfully
ignorant. We live in a world where schoolkids can send a camera high enough to
see the curvature of the Earth, yet we are to believe people who have made the
denial of this a core of their identity do not see fit to replicate the
experiment?)

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Spare_account
<Devil's advocate> _No point sending a camera up, the camera manufacturers
have tweaked the firmware to create the illusion of curvature._

 _I _know_ the earth is flat, so I already know that GoPro are in on the
conspiracy as well._ </Devil's advocate>

Your "throw them on a rocket" idea is the only realistic way to convince them
I would imagine. Which gives me an idea, maybe that could be my ticket to the
moon

~~~
chha
Won't work. The "rocket" is simply an advanced simulator with the ability to
simulate zero G with high-def displays. No matter what kind of evidence you
provide, they will always provide a (far fetched) counter argument.

~~~
logfromblammo
You can't even convince me that there is a Moon until after you release me
from this simulation.~

~~~
rhinoceraptor
I'm considering starting a solipsist meetup group. I can't be sure that there
are any like-minded solipsists out there.

~~~
logfromblammo
Which one of us is me?

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tyho
I have long wondered how easy it would be to perform this experiment as an
amateur. Powerful lasers are quite cheap now. You could get a telescope
(doubling as a beam expander and receiver), and some filters to only allow the
laser wavelength to your detector.

~~~
simonh
Actually very difficult. They use a 30in telescope for these observations and
the beam becomes extremely attenuated. The laser 'spot' projected on the moon
is roughly 7km across. Only a tiny fraction of the light is reflected back as
the reflector is only a few feet across, and is similarly attenuated on the
return journey. The return beam is 20km across by the time it hits the Earth.

Due to the extreme attenuation of the final signal the observation takes
several hours using highly sensitive equipment, averaging it out to extract
meaningful data.

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raldi
I've heard it said that this is the most significant figures ever accurately
recorded in any measurement, ever.

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sveit
Also see the Apache Point Observatory Lunar Laser-ranging Operation
(APOLLO)[0]: "APOLLO measures the round-trip travel time of laser pulses
bounced off the lunar retroreflectors[1] to a precision of a few picoseconds,
corresponding to about one millimeter of precision in range to the moon."

[0]:
[https://tmurphy.physics.ucsd.edu/apollo/apollo.html](https://tmurphy.physics.ucsd.edu/apollo/apollo.html)

[1]:
[https://tmurphy.physics.ucsd.edu/apollo/lrrr.html](https://tmurphy.physics.ucsd.edu/apollo/lrrr.html)

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Zenst
It also highlights how few impacts the moon gets these days as any impact near
this
[https://en.wikipedia.org/wiki/Retroreflector](https://en.wikipedia.org/wiki/Retroreflector)
would kick up moon dust and have a detrimental effect upon such a reflector.

Which is encouraging for any solar installations upon the moon for the one
day, eventual moon base.

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this_was_posted
isn't the lack of impacts near the retroreflector due to the fact that the
moon surface around the reflector is always facing earth?

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foota
The earth covers a pretty small part of the sky for the moon, so I'm not sure
it would have that much effect?

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dzmien
According to NASA [0], you are correct. Furthermore:

"It is likely that each side of the Moon has received equal numbers of
impacts, but the resurfacing by lava results in fewer craters visible on the
near side than the far side, even though the both sides have received the same
number of impacts."

[0]
[https://lunarscience.nasa.gov/?question=3318](https://lunarscience.nasa.gov/?question=3318)

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throw0101a
If he were still alive today, Stanley Kubrick would be very happy that people
are still finding his movie set useful.

:)

~~~
throw0101a
Down votes? Really? People, lighten up. Did you not see the smiley?

