Let me explain conditional statement via set arguments.
If you know A is true for sure, and you can immediately infer that B is true.
A is true is sufficient condition that B is true.
We can also say that the event A is true is contained in the event B is true.
Like you are in London implies that you are in UK. But the other way around is not necessarily true.
and we can say B is necessary condition for A, for notB is in notA - you are not in UK so you are not in London.
Hope this theory make your logic class a lot easier!
In 1943, US Navy launched an experiment near Philadelphia, in which a battle ship with the crew, became invisible due to a special electro-magnetic field. The ship not only disappeared, but reappeared in a different place and a different day, and the crew has gone mad as well.
This is a REAL time travel case, not a fiction!