Transcript: 18-22 September

PAUL
Welcome to Idaho Skies on Radio Boise. This is the third week of September. We're your hosts, Paul..

RACHEL
..Rachel..

KRIS
..And Kris

PAUL
Starting on the 21st, the Zodiacal Light is visible for the next two weeks.

RACHEL
The Zodiacal Light is caused by sunlight reflecting off dust in orbit around the sun.

KRIS
The dust is created by the collision of asteroids and from comet tails.

RACHEL
In dark skies, the Zodiacal Light appears as a tall triangle of faint light.

KRIS
You'll find it rising out of the east and it will have a noticeable tilt to the south. In dark skies it can reach half way to the zenith.

RACHEL
The Zodiacal Light is as bright as the beginning of twilight. But unlike twilight, the Zodiacal Light doesn't lie along the horizon.

KRIS
To see sunlight reflecting off dust in our solar system, look to the east more than an hour before sunrise.

PAUL
Since the sun rises at 7:30 AM, you'll need to be out before 6:30 AM.

RACHEL
Dark adapted eyes are best for viewing the Zodiacal Light, so plan to spend at least 15 minutes outside.

KRIS
One of the best places to see the Zodiacal Light is from the dark skies at Craters of the Moon. And they're having a star party this weekend.

PAUL
The moon is at apogee on the 21st at ten PM. Its distance, which is the greatest for this month, is 252 thousand, 500 miles.

KRIS
That's a lot compared to distances on earth. Even the Apollo astronauts took about three days or 72 hours to cover that distance.

RACHEL
But compared to the rest of the solar system, it's just peanuts. Why the sun is 368 times farther away than that.

KRIS
But if you had to walk to the moon, it would take you until the end of May in 2016 to get there.

RACHEL
Just imagine how many tennis shoes you would go through in that time.

PAUL
It's autumn on the 22nd at ten PM.

RACHEL
The moment autumn begins; the earth is at the autumnal equinox, or that point in its orbit that puts the sun directly over the equator.

KRIS
The word equinox means equal night and it refers to the fact that the day and night are equally long.

RACHEL
This is true for every location on earth. Although technically, refraction by the atmosphere will make the sun rise a few minutes earlier and set a few minutes later.

KRIS
If you could watch our earth from deep space, you'd see that during most of the year the terminator, or boundary between day and night, never passes over the earth's poles.

RACHEL
Instead the terminator would usually be tilted, giving one hemisphere more than 12 hours of sunlight and the opposite hemisphere less than 12 hours.

PAUL
Only at the equator would there always be 12 hours of sunlight.

KRIS
But at the equinox the terminator runs from pole to pole, giving every location on earth 12 hours of day light.

RACHEL
This can only occur at the moment when the earth's rotation axis is tipped neither towards nor away from the sun.

KRIS
And that happens twice each year, at the beginning of spring and the beginning of autumn.

RACHEL
So enjoy today's equal day and night. For the next six months, the nights will be longer than the day.

KRIS
That's far better than it is at the North Pole. There the sun is setting for the next six months.

RACHEL
And that's Idaho Skies for the third week of September. Next week our topic is the first planet X.

For Idaho Skies this is Rachel...

KRIS
..Kris..

PAUL
.. and Paul.