http://news.bbc.co.uk/aboutbbcnews/spl/hi/history/noflash/html/1920s.stm
1971 – The American space probe Mariner 9 began orbiting Mars becoming the first spacecraft to successfully orbit another planet.
http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1971-051A
2007 – The last Direct Current electrical distribution system in the US was shut down by Con Edison in New York.
http://cityroom.blogs.nytimes.com/2007/11/14/off-goes-the-power-current-started-by-thomas-edison/
Read Tom’s science fiction and other fiction books at Merritt’s Books site.