The MythBusters conduct a test at NASA to determine whether a flag on the moon would wave as it does in the video footage of the first moon landing. They find that momentum alone can keep a flag moving in a vacuum; wind is not needed.
Leonard and Sheldon explain to Zach their experiment in which they shoot lasers at the moon to definitively prove that astronauts have landed on it. As they're preparing the experiment, they answer Zach's questions, as unintelligent as they may be.
This scene simulates the moment Neil Armstrong exits the lunar lander on the Apollo 11 mission and steps foot on the moon, a first for human beings. This moment represented the culmination of centuries of mankind's ambitions and scientific understanding.