QUOTE : This 'Planck length' is the only quantity with the dimensions of a length that can be built from the three mist fundamental constants of Nature: the velocity of light c, Planck's constant h, and Newton's gravitational conatant G. It is given by Lp = (Gh/c^3)^1/2 = 4 X 10 ^ -33 cm. This tiny dimension encapsulates the attributes of a world that is at once relativistic (c), quantum mechanical (h), and gravitational (G). It is a standard of length that makes no reference to any artefact of man or even of the chemical and nuclear forces of Nature. Relative to this unit of length, the size of the entire visible universe today extends roughly 10^60 Planck lengths, but the cosmological constant must be less than 10^-118 when referred to these Planck units of length rather than centimetres. To have to consider such a degree of smallness is unprecedented in the entire history of science. Any quantity that is required to be so close to zero by observation must surely in reality be precisely zero. This is what many cosmologists believe. But why?