Well, the machine won't work more recently than a hundred thousand years ago.
5 seconds sound clip from the X Minus 1 - A Gun for Dinosaur by L. Sprague de Camp classic radio drama series.
You can hear this line at 00:08:56 in the radio play.
Quote context
[...]
- Look, where do you shoot for? I mean, with dinosaur. What is the best shot?
- Well, you don't try for his brain, you know. They don't have any.
- Try for the heart. They have big hearts, over a hundred pounds.
- An exploding shell in the heart will slow them down, at least.
- Well, the machine won't work more recently than a hundred thousand years ago.
- Why? Well, I... Look, I'm no four-dimensional expert on the subject...
- And there's also some kind of taboo about sending people back to the same time again.
- Eh, it's paradoxes... mustn't have 'em.
- I'm not sure but the university isn't taking chances.
- They've got about a billion years to cover... they won't run out of eras.
[...]
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Actors: Fred Collins (Announcer), Wendell Holmes, Bill Zuckert, Peter Capell
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