Teaching astronomy this year and wanted to have some simple/quick "facts"
(using approximate numbers) to share with students and parents. For
example, light takes 8 min to get from the Sun to the Earth. In that time
the Sun moves four of its own diameters. (Sun moves 15° per hour in the
sky, or 1° every four minutes, or 2° every 8 minutes -- four solar
diameters). This seems about right. Sunsets appear to take longer, but I
have not timed them. Maybe there are some optical effects/refraction from
our atmosphere? Earth's rotation? Minimal effect?
What about the Moon? It has a diameter of 2000 miles and moves 2000 mph --
it moves its own diameter across the sky each hour. I think solar/lunar
eclipses take about an hour to progress from start to totality. But the
Moon appears to move much faster across the sky. I think we need to take
the Earth's rotation into account. Moon moves 360° in 29.5 days, or
12.2°/day. Earth spins 360° in 24 h, or 4 min per degree. So the Moon rises
4 min/° x 12.2°/day = 48 min (or 0.8 h) later each night. The Moon takes
24.8 h to appear at the same point in the sky. So it moves 360°/24.8 h =
14.5°/h. To move its own diameter takes 0.5°/(14.5°/h) = 0.034 h = 2 min.
Seems reasonable as I often watch the Moon But what about Earth's movement
around the Sun in one day? Minimal effect?
Can anyone check these ideas/numbers? I didn't intend this to be a "math"
email, but the Moon thing intrigued me.
*CONFIDENTIALITY NOTE:*
The information transmitted, including attachments, is intended only for
the person(s) or entity to which it is addressed and may contain
confidential and/or privileged material. Any review, retransmission,
dissemination or other use of, or taking of any action in reliance upon
this information by persons or entities other than the intended recipient
is prohibited. If you received this in error, please contact the sender and
destroy any copies of this information.
Please consider the environment
before printing this email.