Physics Van 3-site Navigational Menu

Physics Van Navigational Menu

Q & A: Gravitational lensing in 3D

Learn more physics!

Most recent answer: 10/22/2007
Q:
WHEN I WAS 13, ME TEACHER WAS TALKING ABOUT LIGHT BEING BENT (General Relativity) BY A "Black Hole" AND SHOULD US A DIAGRAM OF THIS (star, black hole, and earth in a straght line with the star seen above the black hole)... I WAS THINKING ABOUT THIS THAT NIGHT AND IT HIT ME, ALL OF THE PICTURES AND DIAGRAMS WERE "2D" AND WE LIVE IN A "3D" UNIVERSE. SO INSTEAD OF THERE BEING 1 OR 2 STARS SEEN, SHOULDN’T WE SEE A RING OF STARS AROUND THE MASSIVE OBJECT BENDING THE LIGHT?
- Ryan (age 17)
Saunders Secondary School, London, Ontario, Canada
A:
Hi Ryan,

Good job working out the consequences of bending light in a gravitational field! This is a great example of exercising the scientific method: 1) formulate a hypothesis; 2) test its predictions by performing an experiment or observing something in Nature.

Your idea is correct. Here is an example of a ring of images of a quasar behind a lensing galaxy, obtained with the Hubble Space telescope.


This figure came from at NASA.

If the lensing galaxy were symmetrical around the line between us and the quasar, and if it is centered right on that line, we'd get a complete ring. As it is, the distributions are off-axis and nonuniform and so we observe multiple "arcs".

Tom J.

(published on 10/22/2007)

Follow-up on this answer.