Why? Well, I... Look, I'm no four-dimensional expert on the subject...
6 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 00:08:59 in the radio play.
Quote context
[...]
- 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.
- Hallo! Here we go! Now, cheers, eh?
[...]