September 14

1914 – Royal Australian Navy submarine HMAS AE1 vanishes while on combat patrol near Papua New Guinea.

• This begins one of Australia's longest naval mysteries: the sunken vessel will not be discovered for another 103 years.
  

1958 – Two rockets designed by the German engineer Ernst Mohr, the first German post-war rockets, reach Earth's upper atmosphere.

1959 – The Soviet probe Luna 2 crashes onto the Moon, becoming the first human-made object to reach it.

2015 – The first Human observation of gravitational waves is made, a century after they were predicted.

• These gravity waves —ripples in the fabric of spacetime— are believed to result from a cataclysmic event calculated as 1.3 billion light years away from Earth.