Where Yesterday is Tomorrow
Paradox and the international date line

Returning from her Around the World Cruise, Constitution sailed from Manila to Honolulu, crossing the international date line. Ask students to research the location of this line. (It zig zags around the line marking 180 degrees longitude.) What is the purpose of it? What if you lived on it and or it ran through your neighborhood? Explain to the class that a paradox is “an argument that apparently derives self-contradictory conclusions by valid deduction from acceptable premises.” Draw a line on the board as shown below. Explain that for people on side A, the other side is tomorrow; for people on side B, the other side is yesterday. Does this mean the middle of the line is yesterday and tomorrow? What happened to today? Is this a valid paradox? Ask students to look up the famous Zeno’s paradox and compare the two.

Students might be interested to know that the location of the line recently changed. The island nation of Kiribati voted to move the date line so that it no longer cut through the middle of their country, enabling all Kiribatians to be on the same calendar day. With this change, Kiribati claims it was the first place on Earth to see the dawning of the new millennium in the year 2000. (The beginning of 2001 was officially the moment the millennium changed.) Many nations, from Tonga to New Zealand to Fiji were also making this claim. The Royal Observatory in England, which originated the date line, has agreed with Kiribati’s right to redraw the line. What does your class think?

Have on Hand- a world map