"The noise is probably the sound of rocks scraping other rocks, although this has
never been proven (at least to my knowledge)."

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Excellent...always good to see someone speak precisely like that. It is exactly this type of eye to close detail that points the way to breakthroughs in science and should be commended whenever it is seen.

This type of disciminating observation is also regarded by some as an avenue for further pursuit and study (aka - a "hint" if you will...)

Just my 2 cents worth