From left: Edgar Mitchell, Alan Shepard and Stuart Roosa

The space shuttle Challenger exploded 73 seconds after liftoff from Cape Canaveral, killing all seven crew members.

The Surveyor 7 landing site on the Moon 

On Tuesday, January 9, 1968, the Surveyor 7 space probe, the fifth and
final spacecraft of the Surveyor series, made a soft landing on the Moon,
marking the end of the American series of unmanned explorations of the
lunar surface. The primary objectives of the Surveyor program, a series
of seven robotic lunar soft landing flights, were to support the coming
manned Apollo landings. The Surveyor program had a total price tag
of $469 million.   

Pierre and Marie Curie in their laboratory, where radium was discovered

Radium, in the form of radium chloride, was discovered by Marie and Pierre Curie
on December 26,1898. The couple extracted the radioactive compound from
uraninite. The handling of radium was blamed for Marie Curie’s death due to
aplastic anemia.   

A view of Pierre Curie extracting radium

Sir Isaac Newton (25 December 1642 – 20 March 1727)   

Newton was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian. He is considered by many to be the greatest and most influential scientist whoever lived.

Sir Isaac Newton’s First Law of Motion