We Have Seen the Moon Move

Another learning you can point out of the Lunar Eclipse of 15th June 2011 to students is about the time it took the shadow to cover up the whole Moon from when it started at one edge until it covered the whole face of the Moon.  This took place from 9:23 until fully covered at 10:22, which is almost exactly one hour. Now one may ask can we explain this time in terms of the movement of the Moon in its orbit around the Earth?

Now let us do the calculation: 

It takes one month,that is average 30 days for the Moon to move once around the earth, which is 360 degrees in 30 days.

This means that in one day it shifts by 12 degrees per day.

If you now find out how much it shifts in one hour, you have to divide 12 degrees by 24 hours. This gives half a degree per hour, just as you saw during the lunar eclipse.

This means that while you were watching the gradual covering up of the face of the Moon, you were actually watching the Moon move in the sky as it slipped slowly into the Earth’s shadow.

Did you notice that the edge that started darkening first was the edge that was towards the East. This is because the Moon shifts in the sky from West to East.

You can confirm this when you see that from the time of the New Moon when the Moon is in the West at sunset.  In the following days, the Moon will appear higher and higher in the sky at sunset until after 7 days it is over head and half phase and after 14 days, at sunset it is rising in the East as a Full Moon.

This means that in the 14 days from New Moon to Full Moon the Moon has shifted from East to West.  ALL object in the sky including the planets shift slowly day by day westwards.  That is natural movement in our solar system.

So during the lunar eclipse when we saw the Moon being covered up we actually saw the Moon move from East to West as it entered the Earth’s shadow.  We have seen the Moon move!!

Is that not amazing?

NB: This article is acquired from Dr. Jiwaji’s e mail on response to question asked by Students from Agape Secondary School in Moshi Tanzania.


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