WPBT2's Star Gazers

Episode #12-26 "The Reason for the Seasons"
Air Dates June 25 - July 1, 2012



FIVE MINUTE EPISODE SCRIPT
JAMES: Welcome to Star Gazers. I'm James Albury, director of the Kika Silva Pla Planetarium in Gainesville, Florida.†

DEAN: And I'm Dean Regas, outreach astronomer from the Cincinnati Observatory. We're both here to help you be sure you know what you're seeing in the night sky when you...

BOTH: Look up.†

JAMES: If someone asked you, "Why is it hotter in July than in January?" could you give the correct answer? Well, many people might tell you that the reason it's hotter in July than in January is because our earth is closer to the sun in July than in January.

DEAN: But that is about as far from the truth as you can get, because our earth was at its closest point to the sun for the year on January 4th and will be at its farthest point next week on the 4th of July. So why isn't it colder now if we're farther away from the sun? Letís explain.

STOP DROP

JAMES: OK, we're out in make-believe space with a make-believe sun and earth, and if our path around the sun, its orbit, were a perfect circle and if our earth were not at all tilted the weather and the seasons would be approximately the same everywhere on earth all year long, year after year after year.

DEAN: But about 400 years ago an astronomer named Kepler discovered that our earth
Does not travel in a perfect circle, but rather in a stretched out circle called an ellipse, and that our earth is not at the center of that ellipse. So as it makes its annual trip around the sun, earth's distance from the sun changes. It's always closest in January and always farthest in July. But this doesn't account for the seasons, does it?

JAMES: The major cause of the different seasons is due to the tilt of our earth's axis. Now next week on the 4th of July we'll be in the heat of summer but only for us in the northern hemisphere, everything above the equator. Everywhere south of the equator will be experiencing winter. You see our sun always puts out relatively the same amount of light and heat. But in northern-hemisphere-summer, our earth is in the place in its orbit where the northern hemisphere is tilted more directly toward the sun and thus the sun's rays strike more directly on the northern hemisphere than the southern hemisphere.

DEAN: So right now, in the northern hemisphere, the sun's rays are more direct and thus it's hotter in the northern hemisphere than in the southern hemisphere where it's colder because the sun's rays are less direct. When our earth is on the other side of the sun in January, even though the earth is closest to the sun for the year, our northern hemisphere is tilted so that the sun's rays are less direct upon it. So we have the cold of winter while the southern hemisphere is tilted more directly toward the sun's rays, so it's summer time for them. It's really as simple as that.

JAMES: So the reason for the seasons is the tilt of our earth's axis. Our distance from the sun has very little to do with it. In fact when our earth was closest to the sun on January 4th it was only 91 1/2 million miles away. But since that time it has moved over 3 million miles farther away and on this upcoming July 4th will be 94 1/2 million miles away. But that 3 million miles difference doesn't make a heck of a lot of difference temperature-wise.

DEAN: While you're out watching fireworks on the 4th of July, look west for three beautiful planets in the western sky just after sunset. Mercury will be quite low but if you look low in the northwest just as soon as it starts getting dark you might be able to catch it soon after the sun goes down. Up to Mercury's left is reddish gold Mars and up to Mars left is the ringed planet Saturn.

JAMES: Between Mercury and Mars you'll see the stars of Leo the lion as he gets ready to leave the evening sky. Remember the bright star in Leo's heart? It's Regulus. And the bright star up by Saturn is Spica in Virgo.

DEAN: And if you turn and look east you'll have a brilliant, nearly full moon brightening up the night and perhaps making a super backdrop for the fireworks. So this 4th of July ask your friends, why is it hotter in July than in January? And see what kind of answers you get.

BOTH: Keep looking up!

 

Episode #12-26 "The Reason for the Seasons"
Air Dates June 25 - July 1, 2012



ONE MINUTE EPISODE SCRIPT
DEAN: This 4th of July our earth will be at Aphelion, at its farthest point from the sun for the entire year, over three million miles farther away than it was in January. So wait, why is it hotter in July than in January?

JAMES: It all has to do with our earth's tilt. In July our northern hemisphere is tilted toward the sun and thus the sun's direct rays make the weather warmer in the northern hemisphere while the less direct rays make it colder in the southern hemisphere. So it's summer now above the equator but winter below it.

DEAN: in January our northern hemisphere is tilted away from the direct rays of the sun making it colder, even though our earth is closer to the sun in January.

JAMES: After sunset we'll have three planets for you to enjoy in the western sky; Mercury just above the horizon in the early evening with Mars up to its left and Saturn up the left of Mars. So happy earth-at-aphelion on the 4th of July day!

BOTH: Keep looking up!

 

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