“Time” is a weird concept, and the world of quantum physics is even weirder. Numerous observed phenomena oppose our logical understanding. This fact is well illustrated by the classic double-slit experiment used to investigate the role of consciousness in affecting/shaping physical reality.
A modified version of this experiment called “the delayed-choice” or “quantum eraser” experiment is used here to give a cosmic scale explanation.
A scenario that happened billions of years ago in which a star emitting a photon which heads towards the earth is imagined. There is a galaxy in-between. The light needs to bend around the galaxy either to the left or to the right to reach the earth. If billions of years later one sets up an apparatus to trace the photon, the photon will take both the ways.
If a telescope is set on both sides of the galaxy to know which side the photon took. This act of watching itself influences the photon’s direction. The pattern will not be an interference pattern, but a “one way” direction. This means that the way we choose to measure “now” affects the direction that the photon took millions of years back.
Content Source: http://www.anonews.co/quantum-experiment/