OK, Astronomy Magazine has available online (see link) a table of what time the transit of Venus event shall (did) begin for various cities around the world.
The table shows variations of times by minutes (minutes of time, that is) - local time. Why does this vary? When it happens, it happens. As I recall, lunar eclipses, for example follow my “rule”. No matter where you are, the Universal Tie of the lunar event time is simply converted to local time…an adjustment of hours to account for timezones.
…Not sure why the transit table shows these variations!
I’m pretty sure it’s because of time zones. Remember, you’ve got big stretches of distance (~1000 miles or thereabouts) all on the same “local time”, but the actual solar time or sidereal time will vary by about an hour from one side of a time zone to the other. So, the local time listings have to be adjusted to account for this.
Well, remember that one of the reasons why people got excited about transits of Venus in the past was that it gave us a chance to measure the distance to the sun (or maybe Venus) more accurately, using parallax. The Earth is broad enough so that observers in different places on the planet will see the transit start at different times. So that may be the reason for the difference.
It’s definitely not time zones, as all the times in that table are in Universal Time.
Finagle has the right answer. Note that places furthest to the west (in Europe and Africa) saw the first ingress about 13 minutes after those furthest to the east (eastern Australia). Venus goes around the sun faster than the Earth, so it will cross the sun from east to west. So easterners will see the transit first
Using your lunar eclipse model will lead you in the wrong direction. In that case, something is happening to a heavenly body (the moon) as a result, in part, of the motion of ourselves (the earth). When that event happens on the moon, we all see it at the same moment - i.e. when a shadow falls on, say, Copernicus crater, we all see it at the same moment. However, if you use the SOLAR eclipse model, in which something gets in between people on earth and an object in the sky - the sun - then people farther east or west will not see it at the exact same moment, and you have an analog for the Venus transit. The Venus transit is, in fact, an eclipse of the sun. It just doesn’t totally eclipse the sun because it’s so much farther away than the moon.
Yeah, I seem to have slipped a gear there. I thought the table the OP was referring to was using local time with conversions to UTC time. I would have known better if I’d actually looked at the table. :smack:
