Diagram of a solar eclipse
Diagram (not to scale) from the Royal Astronomical Society teacher resource 'The maths of a solar eclipse'

A solar eclipse occurs when the Moon passes between the Earth and the Sun. 

Satellite graphicThe application of Einstein’s theories of special and general relativity are central to the lives of all of us who rely on satellite navigation (GPS). Without application of these theories, positional accuracies would be measured in kilometres not centimetres. Very simply, Special Relativity tells us that the moving clocks on satellites seem to us to run slow and General Relativity tells us that the clocks situated ever farther from the surface of the Earth will appear to us to run fast. It is by measuring the difference in time given by different satellites that we can triangulate our position on Earth.

Einstein published his theory of Special Relativity in 1905 and his General Theory in 1915.

Contemporary graphic showing the deflection of starlight by the sun. Believed to  have been compiled from a composite of two photographs taken at Sobral, it is  similar to an illustration that appeared in The Illustrated London News on 22   November 1919. From Hutchinson’s Splendour of the Heavens (1923) where it is  credited to E.N.A
Contemporary graphic showing the deflection of starlight by the Sun. 


Galaxy cluster Abell 370 photographed by the Hubble Space Telescope. The arcs of light are the effect of gravitational lensing.
Abell 370 galaxy cluster. Image credit: NASA, ESA, and J. Lotz and the HFF Team (STScI)