A huge breakthrough in theoretical astrophysics was announced last week, proving Einstein's theory of general relativity true! In a nutshell, Einstein said that the 3-D space we live in plus a fourth dimension of time is linked together as one entity called spacetime. Heavy objects such as stars, planets and galaxies distort spacetime; basically space bends around these objects. Think about putting a bowling ball on a trampoline. The Sun is the bowling ball and the trampoline is spacetime. The bowling ball is so heavy that sapcetime bends around it. Now roll a marble, which signifies the Earth, around the outside of the trampoline. The Earth revolves around the sun because it's essentially trapped in the funnel of spacetime caused by the Sun. That's why all the planets revolve around the Sun.
Artist conception of frame dragging due to a black hole
The big discovery that was made was the proof of what Einstein called frame dragging. The theory of frame dragging can be understood using the following example. The sun rotates on it's axis and as it does so, it drags spacetime with it. This slight dragging of spacetime causes the precession of planets. So instead of the Earth following the exact same oval every time it orbits the sun, the oval moves slightly. (Kind of like how you make a flowery pattern using the old spirograph toys.) Until very recently, scientists did not know the origin of this precession, and frame dragging was one of many theories behind it. With the help of a telescope called Gravity Probe B, they were able to prove that large objects like the sun do drag spacetime with them as they rotate, and this causes the precession of other small objects that orbit it. The details about this experiment are a bit over my head, but the fact that we observationally proved general relativity true is a big step forward in astronomy!
