Transformation optics

ccording to Einstein’s general theory of relativity, the geometry of space-time is curved by the momentum and energy of macroscopic objects. This curvature is what we perceive as gravity, because it influences the motion of particles such as Newton’s apple falling from a tree in the space-time geometry curved by Earth or the planets circling around in the space-time geometry curved by the sun. Gravity also influences the propagation of waves, the most striking demonstration of which is gravitational lensing where light from distant stars or galaxies is deflected and focused in the space-time geometry created by other stars or galaxies. Gravity is universal, because the geometry of space and time sets the scene for everything, particle and wave alike.