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I can only remember part of this short story, which I believe is from the '60s. A lunar base has been set up to study an installation abandoned by technologically advanced aliens eons before. I can't remember how, but the main character - who was some kind of screw-up - activates two pieces of alien technology which he cannot control. The first is a time machine that keeps shifting him from the far future to the far past - the other is a small rod, a disruptor weapon. He drops the disruptor, which burns all the way down to the lunar core, and when he is shifted into the distant future he finds himself drifting in space because the disruptor has been working all that time and the moon is about the size of a football. Then he is shifted back to the time of the aliens - one of them sees him and picks him up. The end.