Science Museum Principle Animation:Black Hole and Gravitational Lensing Lab

The grid is an embedding diagram of space around the hole: deeper toward the centre, with the horizon at the bottom. Colours and clocks show how fast time passes—slower near the horizon. Light has no mass but must follow curved spacetime, so it bends.

Far away the deflection is α = 4GM/(c²b); closer in, the exact angle grows far beyond the formula. Rays with b below 2.6 Schwarzschild radii are swallowed; those right at the edge circle the photon sphere at 1.5 radii several times before escaping.

Light from the galaxy passes on both sides of the hole, so one galaxy shows two images: the outer one stretched and brightened, the inner one squeezed and dimmed. When all three line up, the images join into a circle—the Einstein ring. This is the view magnified to milliarcseconds; the hole itself is far too small to see.

At the innermost stable orbit the gas moves at about half light speed; the side coming toward us is compressed, brighter and bluer, the receding side dimmer and redder—over ten times apart. Bent light lifts the far side of the disk above the shadow. Jets leave at 0.9c; seen nearly head-on, the counter-jet all but vanishes.