# Gravitational lensing

1. Jan 6, 2013

Hi Everyone,

This is my very first post here.. :)

My question is regarding the gravitational lensing.. i understand that any object with mass in space causes the space to bend more like in the image here.. so imaginig a star behind the planet how would the light of it form gravitational lensing because the space around the planet is not bulging out but instead bulging inside....

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2. Jan 6, 2013

### Staff: Mentor

Light that would have passed by the planet, and the observer in the shadow of the planet, is pulled inward towards the planet. If the gravitational pull is strong enough the path of the light is changed enough for it to be seen by the observer behind the planet, and it then forms an image. (Usually heavily distorted however)

The lines on your image simply represent the strength of the gravitational pull. As the lines approach the planet they are bent further and further from their straight paths by gravity. As they recede gravity is reduced and the lines go back to their straight paths. The lines DO NOT represent something passing by such as light. Light will not bend inwards and then come back out. Imagine a beam of light traveling parallel to one of the top lines. The further the line is bent inward, the greater the strength of gravity is, so the more the path of the light is bent. The greatest bending will occur when the light is at its closest approach to the planet, where the pull is strongest, which is represented by the lines being bent towards the planet the most.

Does that make sense?

3. Jan 6, 2013

so what you are trying to say is that the bending of light is opposite to those gravity liness... iam i right?

4. Jan 6, 2013

### Staff: Mentor

No, the light is bent more strongly where the lines are bent more. When the lines recede from the planet and straighten back out the light is bent less while traveling through that area. If we were to exaggerate this, you would draw a light beam initially parallel to the top line, and as it approached the planet it would start to bend inwards towards it, similar to the line. But, as the line starts to straighten back out, the light beam DOES NOT. It is still bending towards the planet, but less and less at it moves away. The net effect is the light enters from the left side at a 90 degree angle from the edge, bends, and leaves the right side at an angle LESS than 90 degrees from the right edge. So it isn't a straight beam of light, it's a curve.