Various alternative formulations of general relativity were proposed, based for example on tetrads, spinors and twistors (and more recently on connection, loop and non-commutative geometry methods)—but none led to any great simplification.

Around 1621 Wilhelm Schickard probably built a machine based on gears for doing simplified multiplications involved in Johannes Kepler 's calculations of the orbit of the Moon.

Since the 1960s it has been noted in many simplified quantum field theories that there can be a kind of duality in which a soliton or other extended field configuration in one representation becomes what acts like an elementary particle in another representation.

In attempting extensions to 4D, spin foams have been introduced—and variously interpreted in terms of simplified Feynman diagrams, constructs in multidimensional category theory, and possible evolutions of spin networks.

And following a 1951 suggestion from Stanislaw Ulam (who may have already independently considered the problem) he simplified his model and ended up with a 2D cellular automaton (he apparently hoped later to convert the results back to differential equations).