Does a Gravitational Lens Really Magnify Objects?

-- Andy | April 21, 2021

Question:

Gravitational lensing: I sometimes read that gravitational lensing “magnifies” a hidden celestial body (star, galaxy…etc,). The body acting as a lens then bends the light rays coming from the hidden body. Now, we can readily see that the Einstein cross shows four images of the same quasar around the body that is acting as a lens. And in other times we see light that circles around galaxies which are acting like a huge lens.
I do not believe that gravitational lensing magnifies. It only sends the photons coming from a hidden body, bend them (Einstein’s space-time warping), to reach our eyes. No magnifying.
Thank you.
Andy

-- Andy

Answer:

In fact, the magnification due to a gravitational lens is directly analogous to the magnification of objects that one sees when looking at them through a magnifying lens. NASA has produced a very nice video which does a great job of explaining how gravitational lenses magnify objects.

-- Jeff Mangum

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