Two astronauts land on Mars. Their mission: to check whether there is oxygen on the planet.
“Give me the box of matches,” says one. “Either it burns and there is oxygen, or nothing happens.”
He takes the box and is ready to strike a match when, out of the blue, a little green Martian appears, waving all six of his arms and yelling…”No, no, don’t!”
The two guys look at each other, worried. Could there be an unknown explosive gas on Mars?
Still, he takes another match…and…
A crowd of hysterical green Martians is coming to them, all waving their arms: “No, no, don’t do that!”
One of the astronauts says, “This looks serious. What are they afraid of? Nonetheless we’re here for science, to learn if Man can breathe on Mars.”
So he strikes a match–which flames up, burns down, and NOTHING HAPPENS!
So he turns to the Martians and asks, “Why did you want to prevent us from striking a match?”
The leader of the Martians answers, “It’s Shabbos!”