Scientists Witness Meteor Strike on the Moon

Lonesome Squash writes "BBC reports that scientists have seen a smallish meteor strike on the moon. Impact only equivalent to 70kg of TNT, but still, you wouldn't want to have it land on your moonbase. At that size, it's kind of neat they saw it at all."

I don't understand

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How they get that [bbc.co.uk] from that [bbc.co.uk]. Is there some kind of science behind it, or is it just guesswork?