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Hi, I'm Leigh and this week on NASA Now -
winter, spring, summer, fall.
What's the reason for our Seasons?
Here's a clue, think tilt.
And we're celebrating Sun-Earth Day this month
with ancient mysteries and future discoveries.
That's ahead but first let's find
out what else is happening at NASA now.
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Sun-Earth Day is just a few days away and NASA is rolling
out the red carpet to celebrate.
Over the past 11 years, NASA's Sun-Earth day team has come
up with some exciting events
to highlight NASA's research and discoveries.
This year a live webcast brought to you
by NASA Edge will air March 19th.
Check it out.
Where have all the sunspots gone?
That's the question some physicists were asking in 2008
and 2009 when sunspots almost completely disappeared.
A team of scientists have discovered the answer.
This model shows the cycle of sunspot formation.
How they ride on plasma currents like ocean tides.
It shows how they are born, decay,
get pulled toward the interior of the star
where they become re-amplified and pop back
up to the surface like a cork.
In 2009, the plasma currents speeded up, giving less time
for re-amplification and very few sunspots.
It was a period that scientists now refer
to as a "solar minimum".
Read more about this recent discovery right here
on the NASA Explorer Schools Website.
Hey, now let's take a look at the past.
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The first Earth Day was celebrated on April 20, 1970.
Last year, NASA helped commemorate the 40th anniversary
of Earth Day on the National Mall in Washington.
A NASA village was built featuring a science tent
with hands on demonstrations
She's been studying the stars and has been fascinated
with our solar system ever since she was a child growing
up in Hollywood, California.
Now Kelly Fast makes her living as an astrophysicist
at NASA Goddard Space Flight Center in Greenbelt, Maryland.
She's here to answer the question,
why do we have seasons here on Earth?
My name is Kelly Fast.
I'm an astrophysicist here at Goddard Space Flight Center.
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I study the atmospheres of planets.
We have an instrument that was developed here
at Goddard Space Flight Center
with a funny acronym called HIPWAC and it is used
at observatories such as the NASA Infrared Telescope Facility
and the Japanese Subaru Telescope which are
on the big island of Hawaii, Mauna Kea.
One of the best sights in the world
for doing infrared astronomy.
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Well, the Earth has seasons not because it gets closer
to the sun in the summer and then further away
from the sun in the winter.
It does get a little closer and further from the sun
in its orbit, but what really causes the seasons is the fact
that the Earth is tilted.
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Well in the spring and fall you hear the word equinox.
During the equinox you have 12 hours of daylight
and 12 hours of darkness.
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Well, it takes time for things to heat up and cool down.
The summer solstice, that might be the time when we are getting,
in a particular spot on the Earth, the most sunlight.
In the case of the winter,
why is it that we get our cold weather
after the first of the year?
Instead of right at, in December,
when we have the winter solstice.
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We don't know, but it's possible to look at what's going
on in the solar system and to try to track it back and come
up with some ideas to why the Earth might be tilted.
That moon that we have helps us to maintain that tilt,
but how we got that tilt in the first place we can't know
for sure all we can do is theorize.
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You have a wide variety of tilts in the solar system.
Some of them are tilted similar to the Earth, like Mars.
You have planets like Jupiter
that have very little tilt they are almost like straight up
and down and you have a planet like Uranus
that is tilted beyond the horizontal.
It's tilted so far over that its gone beyond where it would be it
if it were just rolling around the sun.
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Other planets do have seasons just like the Earth does
in the sense there's a change as they go around the sun
and as the sunlight hits it differently
because of their tilts.
The planets that aren't tilted as much don't show
as much seasonal behavior.
A planet like Mars has a tilt similar to ours
and it has similar seasons.
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Well, as a scientist I'm motivated
to discover the unknown just because I'm amazed
with just what's out there.
It seems like every time you get a little taste
of maybe some solution to the unknown you want
to find out more and more.
It's ok to not know everything but It's important
to try understand what's out there
because by understanding what happened
in the past it might help us to understand our present,
understand our future.
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Did you know that most magnetic storms
on Earth happen during the equinoxes
in March and September?
Well, that's because the position of the Earth allows
for greater interaction with the interplanetary magnetic field.
Now you know!
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Italian composer and violinist, Antonio Vivaldi,
used the Earth's seasonal relationship to the sun
as inspiration for his masterpiece "The Four Seasons".
"The Four Seasons" consists of four violin concertos,
each inspired by a different season.
Check out this website where you can listen to an excerpt
from each of the concertos and decide
which season Vivaldi is trying to portray.
Well that's it for NASA Now, be sure to tune in next week
when we'll learn about lunar mathematics and mapping.
We'll see you then on NASA Now.
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NASA Now comes to you from the Virtual Campus
at NASA Explorer Schools.