Idaho Skies Transcript for January 8th and 9th

PAUL
Welcome to Idaho Skies for January 8th and 9th. We’re your hosts, Paul...

RACHEL
...and Rachel.

PAUL
The moon reaches the last quarter phase on the 8th.

RACHEL
Last quarter phase is a good time to view the moon through binoculars, but stargazers will need to go outside after midnight.

PAUL
The moon reaches a third quarter seven days after full because it takes the moon 27.3 days to orbit Earth.

RACHEL
That is, relative to the stars.

PAUL
This 27.3 day orbit is called the synodic month and it was much shorter billions of years ago.

RACHEL
The reason a lunar month takes longer today is because the moon is slowly moving farther away from Earth.

PAUL
Measurements using the laser range finders left on the moon by the Apollo astronauts indicates that the moon moves 1.5 inches farther from Earth each year.

RACHEL
So why is the moon slowly spiraling away from Earth?

PAUL
The main reason is because that the moon’s gravity is raising tides on Earth.

RACHEL
Since Earth spins faster than the moon orbits, the gravity of those tides are pushing the moon ahead and therefore into a higher orbit.

PAUL
But as the moon moves further away from Earth, Earth has to slow down its rotation rate to compensate.

RACHEL
Astronomers predict that in several billion years, the length of Earth’s day and the length of Earth’s month will become equal.

PAUL
When that happens, one day in the future will be weeks long.

RACHEL
When that happens, the moon will remain stationary above one point on Earth.

PAUL
Only that hemisphere of Earth will ever see the moon and there will never be another moon rise.

RACHEL
The question is, will the sun have turned into a red giant and vaporize Earth and the moon before this happens.

PAUL
That’s Idaho Skies for the 8th and 9th 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.