Sun-Earth Connection Education Forum Podcasts
Transcript of Sun-Earth Day 2006 Podcast, Program 2
Welcome to the second in a series of NASA podcasts that will explore solar eclipses, and how humankind's fascination with the moon has been evident throughout history. These podcasts will connect you to the cultural history, math and science behind solar eclipses, and why we still find them so exciting to watch today.
My name is Troy Cline and in today's podcast you will hear an interview I recently conducted with Lou Mayo. Lou is a professional astronomer at NASAs Goddard Space Flight Center, and he will be talking to us today about eclipses - and then he'll share some interesting facts that you'll want to know before seeing the eclipse live, or through our webcast on March 29th. Transcripts of his interview along with a copy of the PowerPoint presentation called Solar Eclipses Through Space and Time, are available on our website at sunearthday.nasa.gov .
Before going into the actual interview I asked Lou to tell us a little bit about who he is, and his work.
Lou: "I work at the NASA Goddard Space Flight Center for the Raytheon Corporation. As a researcher, I'm interested in planetary atmospheres, so I have been studying the atmosphere of Titan for quite some time now, Saturn's largest moon, trying to understand for example, is it raining on Titan? And using spacecraft data to determine that. I'm also a program manager, managing a small contract here at the Goddard Space Science Data Operations Office for Raytheon.
But more and more often I've been called upon to do education and public outreach work, and so I'm joining the ranks of an increasing group of scientists called EPO scientists -- Educational and Public Outreach scientists -- and so my job there is to communicate science to the public, to teachers, to students, to the general public, and I really get a lot out of that type of work."
My first few questions to Lou were simple and to the point. What is an eclipse and why do they occur?
Lou: "Well, astronomers get really excited whenever they see any two objects coming together in the sky, and so this kind of thing happens with some regularity, eclipses, transits, conjunctions, all kinds of interesting associations of celestial objects. But when we think of an eclipse, we think of the moon blotting out the Sun, or perhaps the Earth's shadow falling on the moon, as would be the case in the lunar eclipse. Solar eclipses, like the one we'll have on March 29th of this year, happen because the moon periodically moves in front of the Sun as seen from Earth."
"Now, the Moon orbits the Earth about once every month, and so you'd think we'd have an eclipse every month, as the Moon moved back in front of the Sun, but because the Moon's orbit is tilted, just a little bit, with respect to the orbit of the earth, the Sun, Earth and Moon don't always come into straight alignment. Sometimes the Moon's shadow misses too high, sometimes it misses too low. But at least twice a year, the Moon's shadow will fall on the Earth, and we will have some kind of eclipse."
" Now, there are three basic kinds of eclipses. There's a total solar eclipse where the Moon blots out the entire disc of the Sun, which we call the photosphere. And when that happens, that's really exciting because you can see the Sun's atmosphere. You can see the beautiful Solar corona which is very dim, and so it's blotted out with the bright sunlight, with the bright photosphere. But when the Moon blocks the photosphere, you can see the Sun's corona. Or you can have a partial eclipse, a partial Solar eclipse, where the Moon just blocks out part of the photosphere of the Sun. In these eclipses you cannot see the corona because it's still too bright. Another kind of eclipse occurs when the Moon is too far from the Earth in its orbit around the Earth, and so it's a bit too small to cover the entire disc of the Sun. These eclipses are called Annular eclipses. And when you have an Annular eclipse, you'll actually see a ring of the Sun around the Moon. So those are kind of neat, but again, you can't see the solar corona because it's still too bright."
Eclipses have been important throughout history for a variety of reasons. Lou expanded on this topic by focusing on research and historical accounts.
Lou: "Historically, eclipses have been events of tremendous wonder, of awe and great fear and anxiety. You can imagine the Sun going away would have to evoke a tremendous sense of fear in cultures that didn't understand what was happening."
"Traditionally there have been a number of stories that people have made up to explain why the Sun appeared to be going away. Some cultures for example would believe that monsters, or dragons perhaps, were eating the Sun, and so they would run outside and bang pans and make tremendous amounts of noise to drive the monster away. Of course they always succeeded. Some cultures believe that the Sun and the Moon coming together like that meant that they were fighting and they were in disharmony. And so that was a scary time that there was disharmony in the heavens. Some cultures believe that the Sun and the Moon were lovers coming together. But generally, these kinds of events evoked a real sense of fear."
"Today of course we know exactly why we have eclipses. We know how to predict them, and there more events that are fun and just kind of awesome events that remind us of our place in the universe. Research has been done during solar eclipses. Some of this research keys in on the fact that the photosphere is blocked out. The photosphere of the Sun is blocked out by the Moon, and so you're isolating the Solar corona. In fact, that's how helium was discovered -- not first here on Earth, but by observations of the Sun's corona."
"Other studies, for example, in 1919, Einstein's general theory of relativity was tested during a total Solar eclipse where they were able to watch the stars that come out as the Sun's photosphere gets blocked. And they were able to measure the displacement of those stars which happens because the light from those stars is actually bent around the massive Sun, and able to verify that Einstein's general relativity equations were in fact correct. But for the most part, these events are just fun events, wonderful times to get together to look up into the sky and recognize that we have a wonderful universe."
People who are just learning about eclipses often ask questions about the Path of Totality caused by the moons shadow. Lou offers a brief but very understandable explanation.
Lou: "Well, there are actually two kinds of shadows that the Moon casts on the Earth during a total solar eclipse. One kind is the dark Umbral shadow, which is cast on a very small part of the Earth. If you're standing within the Mmbral shadow, you'll actually see the total eclipse of the Sun, you'll see the Sun's photosphere completely blocked out. Another kind is the Penumbral shadow, and that covers a much larger area on the Earth. If you're standing within the Penumbral shadow, you will see a portion of the Sun blocked out, but not a total eclipse."
"The Path of Totality is the path that the Umbral shadow makes across the Earth as the eclipse progresses. And this happens primarily because the Earth is spinning under the Moon. The Path of Totality for the March 29th Solar eclipse begins on the east coast of Brazil where you're unlikely to see an eclipse because its often very cloudy there. It then proceeds across the Atlantic Ocean and through Africa, proceeding north through the Middle East into Turkey, and on into Asia"
There are a number of ways people can learn about eclipses and astronomy in general. I asked Lou to share a few programs that might help those interested get more involved.
Lou: "Well, of course the night sky and the day sky for that matter are accessible to everyone. And there are thousands and thousands of people all over the globe that have joined amateur astronomy clubs in order to share their passion, their interest in astronomy and in viewing the night sky. And these are groups that get together on a regular basis with telescopes and look at the night sky. Many of them have education programs that work through school systems or community groups, and work with children as well to help communicate the wonder of astronomy to pretty much anyone who wants to listen."
"For the March 29th Solar eclipse, amateur astronomers and astronomy enthusiasts from all over the globe will be traveling to The Path of Totality, to Turkey, Libya, and other countries to view the eclipse in totality. And if you go to our website at sunearthday.nasa.gov, you'll find a section for amateur astronomers focused specifically on their interests."
"Troy, as you know, one thing I feel passionately about is bringing the excitement of astronomy to children. And in support of that, NASA has developed a network of after school astronomy clubs from all over the planet. These clubs are often taught in an after school setting, are kid focused, which makes them unique, and just provide kids with a whole variety of learning experiences in astronomy, usually during the day time. If you want to find out more about these kinds of clubs, you can even go the website which is afterschoolastronomy.org."
For details about this year's Sun-Earth Day program, you can visit our website at sunearthday.nasa.gov and explore our classroom resources for teachers and students. You will also find information on public programs being conducted at many museums and science centers around the world.
So get prepared, because on March 29, we will bring the eclipse to you live from Side, Turkey, through an online webcast!
We'll see you next time!
Sun Earth Day is a program sponsored by the NASA Sun-Earth Connection Education Forum at the Goddard Space Flight Center, and at the UC Berkeley Space Sciences Laboratory.
To find out more about the Sun Earth Day program, and eclipses, visit our website at sunearthday.nasa.gov.
This is Troy Cline signing off.
