String theory, on the other hand, takes a very different point of departure in tackling the problem of quantum gravity. The requirement of mathematical consistency and the non-renormalizability of perturbatively quantized gravity, and the need to incorporate the non-gravitational interactions are likely to force us to modify Einstein's theory at the smallest distances (Planck scale). This may not only lead to a geometrization of the other fundamental forces (as exemplified by Kaluza-Klein theories and supergravity) and the unification of matter and gravity, but to an entirely new type of theory, which could explain how space-time is dissolved at very small distances, and in which Einstein's theory emerges only as an effective low energy theory, valid above distances above the Planck scale. Superstring and supermembrane theory, and supersymmetric matrix theory are the most promising ansaetze so far in this direction. Major progress in this area has been recently achieved by members of the division, in particular the framework of the so-called AdS/CFT correspondence, and the study of certain infinite dimensional symmetries, which might underlie a unified and non-perturbative description of string theory (M theory).

The apparent force of gravity on Earth is the resultant (vector sum) of two forces: [31] (a) The gravitational attraction in accordance with Newton's universal law of gravitation, and (b) the centrifugal force, which results from the choice of an earthbound, rotating frame of reference. The force of gravity is the weakest at the equator because of the centrifugal force caused by the Earth's rotation and because points on the equator are furthest from the center of the Earth. The force of gravity varies with latitude and increases from about m/s 2 at the Equator to about m/s 2 at the poles.

* For cars without wheels, or clean hydrogen electric cars, where the car or truck will be able to overcome the gravity of the Earth and levitate, using a system the size of a domestic microwave oven.
Plasma reactors can generate electricity for the cars of the future, fully electrified.*
plasma reactors with double magnetic fields will hover cars, trucks, ships, airplanes
Aircraft industry