A hammer and a feather, dropped together

At the end of the last moonwalk of Apollo 15, David Scott held out a geology hammer and a falcon feather and let go of both at once.

They hit the dust together, on live television, which is Galileo's argument settled in a place with no air to spoil it. Scott's line was that it made Mr Galileo's findings correct. The camera was being operated from Houston, with a delay, and it caught it.