Measuring the Earth: Latitude and Longitude

Measuring your latitude is relatively easy; the Greeks and others were doing this from a very early date. Longitude was not so easy, however. Because the Earth spins, the stars appear to move from east to west. You can’t just look up in the sky and determine your location. Instead, measuring longitude depends upon knowing exactly what time it is.

What time is it? A short story…
Have you ever traveled to a different time zone and tried to call home? When I lived on the West Coast, my Mom would always want to call up and say hello. The problem was that she lives here, on the East Coast. So she would get up in the morning, pace around anxiously, and force herself to wait until a decent hour to call me (she knew that I like to sleep late…). So, finally, it would be 9am Eastern Standard Time, and she wouldn’t be able to contain herself any longer… “Marty should be up by 9am, right?”

Well… maybe not. What time would it be on the West Coast? Naturally, I’d still be sleeping and wouldn’t want to talk.

So anyway, the day would pass by, and I’d be feeling rather guilty about not talking to my Mom… I was usually pretty busy, and would want to get home, eat dinner, and relax before calling home.

So, it would be a few minutes after 9pm, Pacific Standard Time, and I would start thinking about calling home… I’d think “sure my mother goes to bed early, but there’s no way she’d go to bed before 9pm… right?”

And of course, after I made the call, my Mom would be very gracious, and would always want to talk to me, no matter what time it was.

Eastern Standard Time is:
2 hours AHEAD of Pacific Standard Time (PST)
2 hours BEHIND PST
3 hours AHEAD of PST
3 hours BEHIND PST