The Krell furnaces... chain reaction... they cannot be reversed.
10 seconds sound clip from the Forbidden Planet (1956) movie soundboard.
You can hear this line at 01:35:49 in the Blu-ray version of the movie.
Quote context
[...]
- Stop. No further. I deny you, I give you up.
- In 24 hours you must be 100 million miles out in space.
- The Krell furnaces... chain reaction... they cannot be reversed.
- Oh, no.
- Ninety-eight million point six.
[...]