Equinoctial Sunrise

It is the morning after the equinox and not a bad one either. The sun rises due east on the equinox, but the daily difference is at its greatest at this time too so we have already moved north of east.

In this picture the horizon is well above sea level because of the hill, so we have to bear in mind that the angle the sun makes to the horizon will be 90 degrees minus our latitude, ie. our colatitude.

Horizon

There was a typically excellent Horizon documentary on BBC2 last night called, 'Do You Know What Time It Is?' It ranged and veered in a challenging and entertaining way from the Mayans to the sub-atomic. I hadn't planned to watch it all, more of a 'give it a chance' type of sit down, but it got its claws in early on. I failed to escape the sofa for the full hour, despite being subjected to some string theory along the way.

One of the things I learned (as opposed to being 'bamboozled by') was that the time it takes the earth to rotate varies slightly (a millisecond or so) each day and the reason for it is... the winds. The winds on earth actually affect the speed the whole thing rotates. And, as Columbo might say, one more thing... the speed of the earth's rotation is slowing down, a few hundred million years ago a day only lasted 22 hours.

Like so many other excellent Horizon programmes this one really got the mental juices flowing, without it has to be said actually changing the price of tea in China very much.