Presentation on theme: "T.A.Rector, I.P.Dell'Antonio /NOAO /AURA/NSF."— Presentation transcript:
T.A.Rector, I.P.Dell'Antonio /NOAO /AURA/NSF
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Imagine that there was zero inclination to ecliptic for the Moon's orbit. How often would we have eclipses? 1.There would be one total lunar eclipse and one total/annular solar eclipse every lunar month. 2.There would be two total lunar eclipses and two total/annular solar eclipses every lunar month. 3. There would never be any eclipses.
Moon Visibility... The table gives a summary of approximately when the Moon is visible and where to look (the crescent and gibbous phases are in between the table values). There are times during the moon's monthly cycle that the Moon is sometimes visible in broad daylight! Phase Ahead or Behind the Sun Rise Time in East Mid-Point In Sky Set Time In West New Within few minutes SunriseNoonSunset 1st Qtr.6 hrs behindNoonSunsetMidnight Full12 hrs behindSunsetMidnightSunrise 3rd Qtr.6 hrs aheadMidnightSunriseNoon
The most common incorrect reason given for the cause of the Moon's phases is that we are seeing the shadow of the Earth on the Moon! But this cannot be correct: when the Moon passes through the shadow of the Earth, we get a lunar eclipse. Anyone who has seen a lunar eclipse, though, might remember that the Moon actually passes through the Earth's shadow only rarely, so that can't be why the Moon has phases. The real reason for the Moon's phases depends on two things: the Moon is round, and the angle it makes with the Earth and Sun changes over its orbit.
Phobos Phobos: Mars moon Captured asteroid
Phobos Photo by HiRISE, MRO, LPL (U. Arizona), NASA Phobos: Mars moon Captured asteroid
Deimos Deimos: Mars moon: captured asteroid
Question: Every one on the night side of the Earth can see a total lunar eclipse. They see each part of the event at: 1.the same clock time. 2.the same time as read from the position of the Sun: i.e., true solar time. 3.the same time. Really, really, the same time (i.e., simultaneously) not counting light travel-time effects, or special or general relativity effects
Caption: "Lunar base concept drawing from NASA". The large field with ``furrows'' is probably an array of solar panels. But on the other hand, someone seems to be turning sod. The long linear structure is a mass driver is an electromagnetic launch device. A few experimental mass drivers have existed since 1976.