Gravitational lensing is a phenomenon predicted by Einstein's general theory of relativity, where the presence of a massive object, such as a galaxy or a black hole, distorts the fabric of spacetime and causes the path of light passing near it to bend.

This effect can be used to magnify and distort the images of distant galaxies, allowing astronomers to study the properties of these objects in detail. The Crash Course Pods: The Universe episode on black holes discusses how black holes can act as gravitational lenses, while the Nature Podcast episode highlights the use of gravitational lensing by the James Webb Space Telescope to amplify light from distant galaxies.

Gravitational lensing is a powerful tool in the field of astrophysics, providing insights into the distribution of matter in the universe and the nature of dark matter, as well as enabling the study of distant, faint, and otherwise undetectable astronomical objects.