Clinamen

Lucretius wrote :

The atoms, as their own weight bears them down
Plumb through the void, at scarce determined times,
In scarce determined places, from their course
Decline a little - call it, so to speak,
Mere changed trend. For were it not their wont
Thuswise to swerve, down would they fall, each one,
Like drops of rain, through the unbottomed void;
And then collisions ne'er could be nor blows
Among the primal elements; and thus
Nature would never have created aught.

This text regards the concept of the "Clinamen", which represents a certain idea of indetermination or determination (depending on how you view it) in the existence of things.
Plenty of people have their take on it, and it generally appears to be rather a pseudoscientific and philosophical source of speculation on the origin of life than a hard edge scientific concept.
The fact that it represents a notion of movement in the course of gravity seems particularly interesting. We do fall constantly, but in our fall we will bump into something which will prevent there being absolutely nothing.