What discovery gave scientists the first evidence for the theory of plate ttectonics

Before that, the similar theory of continental drift was suggested by mountain formation and earthquakes. When mid-ocean ridges were discovered, it was realised how continents moved, they were "floating" on top of the magma underneath the crust, and their movement was influenced by the currents in the magma. Some plates move under other plates, and they move apart.

Answer the radiant sun;