ABSTRACT
According 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.
