Gravitational Lensing!

I'm not going to lie, I don't understand a lot of Einstein's model of General and Special Relativity. One thing, however, I do understand (well, I at least understand the concept of it, I still have a hard time with wrapping my head around spacetime as an actual thing). Anyway, Gravitational lensing is one of the few things this semester I got the concept of immediately.

Gravitational lensing was one of the first tests that helped to prove Einstein's theory of General Relativity. First, it's important to realize that the "fabric" of spacetime is curved by objects with mass, but objects with larger masses curve spacetime more. The Earth curves space time, but the Sun curves it more.



In class, we used the anatomy of a water bed. The surface of the water bed is spacetime, and if you put a small object on the surface, it creates a small dip around the object. Bigger object (more massive object), bigger dip.

Got that? Good. Moving on.

Light rays travel in straight lines, right? Well, not necessarily, all the time. If the spacetime through which a light ray is traveling is curved (like when light passes near the surface of the Sun) the path of the light ray is also curved. Basically, gravity bends light.


The maximum light will bend is only 1.75 arcseconds, but it is enough to make far-away stars appear to be in a different position then they actually are. Another effect of gravitational lensing is that very, very distant objects seem brighter, and are therefore easier to see and study.