What Neil & Buzz Left on the Moon (Other Than Footprints)

science.nasa.gov

21 points·diwank··4 comments

A very interesting example of relatively lesser-known scientific innovations. It is a surprisingly rare knowledge. In fact, it is one of the evidences scientists use to refute the claim of the moon-landing deniers.

It is also worth mentioning that this project has now been axed (in 2009 to be precise) as the mirrors have gotten dusty and no longer provide the same worth of scientific data they used to [1]. The above post was written in 2004, long before such problems surfaced.

[1]: www.guardian.co.uk/technology/2009/jun/21/mcdonald-observatory-space-laser-funding

This was mentioned in the article: "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."

Does anybody know what specific flaw(s) they're talking about?

A scientific theory is a set of principles that explain and predict phenomena. All theories are only provisional, in that they are upholded every time an observation supports the predictions they make. In principle, a good observation that is inconsistent with a theory's prediction can falsify it.

In this case, Einstein's theory predicts the lunar orbit to be slightly different than Newton's gravitation model. If someone could find a discrepancy in new observation he would have found a flaw in Einstein's theory of general relativity.

As of this writing, no flaws have been found in the theory of general relativity. Though such claims pop up every now and then.

What do they mean when they say the gravitational constant has changed less than 1 part in 100 billion? Surely that's within experimental error? I think they mean to say "there is no evidence that it has changed at all".

Reply on news.ycombinator.com