Measuring the distance from the Earth to the moon (Luna)

[MetricRocketeer]

Hi TRF colleagues,

I believe that this is the correct forum in which to post this question.

Someone please correct me if I am wrong in any of what I am about to say.

I have heard that, during an Apollo mission, the astronauts planted a receiver of some kind on Luna. A signal of some sort sent from Earth could reach this receiver and bounce back a return signal to Earth. With this method -- which continues in use to this day -- the distance from the transmitting station on Earth to the Luna receiver can be determined with millimetre accuracy.

Does anyone know, please, if this Is correct, and do you have more details?

Thank you for your consideration.

Stanley

 

[Mushtang]

Mirrors

https://en.wikipedia.org/wiki/Lunar_Laser_Ranging_experiment

A cool episode of Myth Busters had the guys visit a huge laser which pointed to one of these and measured the return. It was a crazy small number of photons that returned from a hugely powerful laser pulse. But it was still detectable and enough to make a measurement.

 

[Funkworks]

Yup. According to:
https://spie.org/news/12-09-laser-ranging?SSO=1

We have “a precision equivalent to determining the distance between Los Angeles and New York to 1/100 of an inch” (that’s 0.254 mm)

A similar more recent experiment:
https://www.nasa.gov/feature/goddard/2020/laser-beams-reflected-between-earth-and-moon-boost-science

 

[MetricRocketeer]

Hi @Mushtang and @Funkworks ,

Thank you for the quick response, and the great references.

Stanley

 

[Marc_G]

Also made for a fun scene in Big Bang Theory...

 

[Hobie1dog]

according to the charlatan David Icke, the moon is made plywood and 2x4's, or it's definitely hollow as the instruments said it rang like bell, according to David, and people pay lots of money to go see his "shows", and believe everything he says.

 

[Funkworks]

Also made for a fun scene in Big Bang Theory...