cGh physics

Because of the tremendously large value of the speed of light—c (i.e. 299,792,458 metres per second in vacuum)—compared to the range of human perceptual response and visual processing, the propagation of light is normally perceived as instantaneous.

Hence, the ratio 1/c is sufficiently close to zero that all subsequent differences of calculations in relativistic mechanics are similarly 'invisible' relative to human perception.

However, at speeds comparable to the speed of light (c), Lorentz transformation (as per special relativity) produces substantially different results which agree more accurately with (sufficiently precise) experimental measurement.

ignoring terms (in the Taylor expansion) with a factor of 1/c—producing a first-order approximation of the formulae.

Similarly, in the theories where the effects of quantum mechanics are irrelevant, the value of Planck constant (h) can be neglected.

Diagram showing where quantum gravity sits in the a near-cube hierarchy of physics theories. Note that electromagnetism and quantum field theory in curved spacetime are added in as an extra and distinct items.