On this Day in History

On this Day in History in 295: 8th recorded perihelion passage of Halley’s Comet.
 
On this Day in History in 1702: Comet C/1702 H1 approaches within 0.0437 AUs of Earth.
 
On this Day in History in 1902: Marie & Pierre Curie isolate the radioactive element radium chloride.
 
On this Day in History in 1940: The First electron microscope was demonstrated by RCA.