The gravitational force is the oldest force known to man and the least understood.


P. Van Nieuwenhuizen (1981). Supergravity, Volume 68, Issue 4 of Physics reports. North-Holland Pub. Co.. p. 4.


The gravitational force is the oldest force known to man and the least understood.

The gravitational force is the oldest force known to man and the least understood.

The gravitational force is the oldest force known to man and the least understood.

The gravitational force is the oldest force known to man and the least understood.