I've got your six
I recall a conversation when I was younger with someone explaining that there was (of course) a time before traffic lights when busy junctions had a policeman directing traffic. It is interesting seeing old films that show that, and some horse drawn vehicles.
What I find especially interesting is technologies that are vanishing from the face of the earth so completely that anyone younger than a certain age has no clue what the hell you are talking about.
Things like the "Phone box" are vanishing quickly. The rotary dial telephone is so unusual there is a whole generation that would have a had time recognising it as a phone, let alone using it. And an audio cassette tape would baffle them. I have heard people very confused by the concept of paper maps even!
It is especially interesting when you have technology that was new when I was younger and has now almost completely vanished in just a few short decades - like the "CD".
Watch Back to The Future II - it amusing how they assume CD and video disks will be with us so much in 2015 and still have phone boxes! The barcode number plate is especially amusing - realising that a machine readable ID is needed in the future but not realising that computers will be able to read letters or more likely that cars will all have real time wireless location reporting as a normal feature some day.
I was today trying to clarify some artwork for an engraving job, and got the very sensible answer: "The notch goes at 9 o'clock". But it struck me, I am not sure my kids would know what was meant by that phrase. A "traditional" analogue clock face is getting rarer and rarer these days. It won't be long before phrases like "I've got your six" lose all original meaning and become one of those strange quirks of English (or possibly American) language.
As I say, an interesting time in which to live.