What is Gravitational Lensing?

Reference News:-

This article forms a part of The Hindu’s Science for All newsletter, which explains all things Science, without the jargon.

What is gravitational lensing? How does it work?

Gravitational lensing is an effect of Einstein’s theory of general relativity – simply put, mass bends light.
The gravitational field of a massive object will extend far into space, and cause light rays passing close to that object (and thus through its gravitational field) to be bent and refocused somewhere else.
The more massive the object, the stronger its gravitational field and hence the greater the bending of light rays – just like using denser materials to make optical lenses results in a greater amount of refraction.

Benefits:

Gravitational lensing is useful to cosmologists because it is directly sensitive to the amount and distribution of dark matter.
Lensing can help astronomers work out exactly how much dark matter there is in the Universe as a whole and also how it is distributed.
Lensing has also been used to help verify the existence of dark matter itself.