# Can something you see through a telescope be behind you?

For the 1st paragraph of your question:

You need light to see anything.

Firstly I will emphasize on my comment.

If you reach the event horizon of a black hole safely (where light can get into orbit around the black hole), then since the light is in orbit, the light from the back of your head would go around the black hole and come back to reach the front of your eyes enabling you to see the back of your head. But there are subtleties involved and I am just a beginner in general relativity.

Secondly for your question. It does happen. It's called Gravitational Lensing.

A gravitational lens is a distribution of matter (such as a cluster of galaxies) between a distant light source and an observer, that is capable of bending the light from the source as the light travels towards the observer. This effect is known as gravitational lensing, and the amount of bending is one of the predictions of Albert Einstein's general theory of relativity.

In general relativity, light follows the curvature of spacetime, hence when light passes around a massive object, it is bent. This means that the light from an object on the other side will be bent towards an observer's eye, just like an ordinary lens. Since light always moves at a constant speed, lensing changes the direction of the velocity of the light, but not the magnitude.

From Wikipedia:

Light rays are the boundary between the future, the spacelike, and the past regions. The gravitational attraction can be viewed as the motion of undisturbed objects in a background curved geometry or alternatively as the response of objects to a force in a flat geometry.

$\theta = \frac{4GM}{rc^2}$

toward the mass M at a distance r from the affected radiation, where G is the universal constant of gravitation and c is the speed of light in a vacuum.

Have a look at this:

https://en.m.wikipedia.org/wiki/File:Black_hole_lensing_web.gif

Incidentally, Gravitational Lensing is used widely to predict the existence of dark matter and gravitational lensing has shown that the dark matter problem isn't due to a fault in GTR (I have read so) or due to its incompleteness but rather the Standard Model is incomplete (once again, Einstein prevails).

Yes in principle that is possible, however usually you won't recognize the light as a star anymore, because it has to come very close to a large gravitational field of a black hole. What is indeed observed and you can find pictures of that is black holes acting as gravitational lenses so that you see galaxies or stars behind it multiple times. This is possible because the light can bend around the black hole on different sides. So if you are just looking for the effect of gravity bending light I suggest looking for that.