Idaho Skies Transcript for January 17th and 18th

PAUL
Welcome to Idaho Skies for January 17th and 18th. We’re your hosts, Paul...

RACHEL
...and Rachel.

PAUL
The moon is new on the 17th.

RACHEL
That means it’s too close to the sun to see and will set before its gets dark.

PAUL
Perhaps this would be a good time to distinguish between the moon’s far side and the moon’s dark side.

RACHEL
Sure. The lunar far side is the half of the moon we can never see from Earth.

PAUL
And there’s no such thing as the dark side of the moon.

RACHEL
The far side exists because the moon’s day, or the time it takes to rotate once on its axis is 27.3 days.

PAUL
And the length of time it takes the moon to orbit Earth is also 27.3 days.

RACHEL
This means the moon rotates at exactly the rate at which its orbits Earth.

PAUL
The result is that there’s one side of the moon we can never see from Earth.

RACHEL
This is the moon’s far side and it was a mystery until the early Space Age in 1959.

PAUL
Actually, we can manage to see 9% of the moon’s far side.

RACHEL
The reason for this is called libration.

PAUL
One form of libration occurs because the moon’s orbit is elliptical.

RACHEL
This means there are times when the moon is recessing from or approaching Earth.

PAUL
And this allows the moon’s rotation to get a little ahead or behind a line between the centers of the moon and Earth.

RACHEL
A second form occurs because the moon’s orbit is tilted.

PAUL
So at times, the moon is either low or high in its orbit and we can see just peak over the moon’s top or bottom.

RACHEL
Finally, we can just glimpse a bit over the moon’s edge as it rises and sets.

PAUL
That’s Idaho Skies for the 17th and 18th of January.

RACHEL
Be sure to follow us on Twitter @IdahoSkies for this week’s event reminders and sky maps.

For Idaho Skies this is Rachel...

PAUL
...and Paul.

RACHEL
Dark skies and bright stars.