A visualisation of how extreme gravity can distort the light paths close to binary black holes. The blue and red halos are the accretion disks surrounding the black holes (material super heated close to the event horizon). The blue disk represents a black hole some 200 million times the mass of our Sun. The red one is a smaller black hole half this mass.

Gravitational lensing like this is a real and measurable consequence of general relativity and astrophysicists are now using sophisticated modelling techniques to make incredible predictions. One amazing application of gravitational lensing is predicting when duplicated but delayed images from the same supernovae will appear, allowing astronomers to study exploding stars in real time.

This happens when a single event – like a supernova – is projected into multiple copies of itself by a large intervening galactic mass, with each copy delayed due to different light paths through spacetime.⁣

Video Credit: @NASAGoddard