Our ground-based telescopes have given us great views of the Cosmos and the Hubble Space Telescope (HST) has revolutionized our understanding of astronomy. But even the HST, orbiting high above our turbulent atmosphere, has its limitations. It seems Mother Nature, like so many other things, is way ahead of us by building great beasts of telescopes in deep space - we just need to find them! I am referring to gravitational lenses.
As their name suggests, a gravitational lens is a lens created as a consequence of the force of gravity and their existence was predicted by Einstein in his famous theory of general relativity.
To understand how gravitational lenses work, it's necessary to delve into the very fabric of space (which is fiercely intertwined with time but for the purpose of this article, lets forget about the "time" in "spacetime").
ANALYSIS: Mapping Dark Matter with a Cosmic Lens
Firstly, imagine space as an unending sheet of rubber with balls rolling around on the sheet. The balls (of various sizes) represent the galaxies and the rubber sheet represents the "fabric of space." Placing the balls on the sheet will cause deformation and dents will form as the balls' mass exert a downward pressure. The greater the mass, the deeper the dent.