Where are we?

Wherever you are on Earth, the same stars appear. Not in the same place, or at the same time, but there they are. If we were mariners sailing the seas of long are, we would use the stars to guide us. Thatıs all we would have.

Well, we could tell how far north or south we were (our latitude) by looking at the North Star. The Earth is a sphere (people always knew that) whose axis points to the North Star (Polaris.) At the North Pole Polaris is directly overhead; as we move south, this star drops lower in the sky. (In fact, this was just how people knew the Earth was round.)

If we wanted to sail to a certain spot, we would sail north or south, watching Polaris, until we reached the correct latitude. Then we would sail east or west until we bumped into something. Not a great solution, but that's all we would have. That's why Columbus, bumping into the Bahamas, thought he had landed in the Indies.

But now we know, when we call a friend in another country, that the time there is different from the time here. When the Sun is setting here, it may be high in the sky there - or have already set. Again, this is because the Earth is round. If we knew how high the Sun was in that country - or the time there, we would know how far east or west of that place we were. We would know our longitude.

Nowadays, it's easy to know the time in another country. We can just call a friend there and ask. Or, if we had no friend there, we could hop on a plane, fly there, and set our watch. Nothing we could do, say, in the time of Columbus. What then?

We could travel there (by horse or ship) set a clock, and come home. Only one thing. It had better be a good clock. No pendulums - the rocky sea would make them impossible to use.

There were no good clocks in Columbus' time. They were yet to be invented. So there were dozens, probably hundreds of ship wrecks. Until 1704. Then William Harrison invented the first accurate, seaworthy clock.

Only since then can we all know just where we are.

(03/11/09)