Light bends too

Starlight passing the Sun

When spacetime bends, light follows the bend too. Light from a star just behind the Sun bends slightly as it passes the Sun, then reaches our eyes. So the star looks a little farther out than where it really is. During a total solar eclipse in 1919, astronomers photographed stars next to the Sun and confirmed this prediction.

Why?Normally the Sun is far too bright for us to see the stars right next to it. Only during a total eclipse, when the Moon covers the Sun completely, could those stars be photographed.

Learn moreLight grazing the edge of the Sun bends by about 1.75 arcseconds. One arcsecond is a tiny angle, one degree divided by 3,600, so the screen exaggerates it hugely. Very heavy things like galaxies can bend the light of galaxies behind them so much that they look like rings. This is called gravitational lensing.

Clock we are watching

A clock on the Sun’s surface

How much slower

About 0.2 s slower per day

Clock rate

0.9999979

seconds this clock ticks while a clock far away in empty space ticks one second · calculated with the formulas of relativity