Date: September 8, 2009

Title: Who Wants To Be An Astronomaire

Podcaster: Wayne Harris-Wyrick

Organization: Kirkpatrick Planetarium of Science Museum Oklahoma.
Visit the Museum’s site at www.sciencemuseumok.org.

Description: With apologies to Meredith Vieira (and Regis Philbin), here is my version of “Who Wants To Be An Astronomaire”, a game-show-like quiz on some basic astronomy-related concepts. You may Phone a Friend, but no searching the Internet.

Bio: Wayne Harris-Wyrick is the Director of the Kirkpatrick Planetarium, a part of Science Museum Oklahoma, where he has taught astronomy to countless thousands of kids and families for more than 30 years. Wayne writes a monthly astronomy column covering all aspects of this amazing universe. Wayne can be contacted at wwyrick@sciencemuseumok.org.

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by the American Astronomical Society, the major organization for professional astronomers in North America, whose members remind everyone that One Sky Connects Us All. Find out more or join the AAS at aas.org.

Transcript:

Hi. This is Wayne Harris-Wyrick. I am the director of the Kirkpatrick Planetarium, part of Science Museum Oklahoma. Welcome to today’s edition of WHO WANTS TO BE AN ASTRONOMAIRE, the game show about astronomy. You know the rules and the lifelines, so let’s play. We are ready for the $32,00 question.

$32,000: Which of the following is the largest?
A.) Sun
B.) Milky Way
C.) Earth
D.) Solar System

The correct answer is B. Earth is 7,926 miles across at the equator. Our sun, a more or less typical star is 865,000 miles in diameter. A solar system consists of a star and any planets, asteroids, and comets that orbit it. We know of some 300 other stars that have at least one planet, and there are several that have two or more. Solar systems are typically a few billion miles across.

Technically, our solar system is the Solar System, since Sol is the name of our sun. Other stars that possess planets are generically referred to as stellar systems.

A good-sized galaxy consists of upwards of one hundred billion stars, with perhaps a quarter of those possessing planets, making them stellar systems. Galaxies also contain nebulae, huge clouds of gas and dust from which stars are born, and some bizarre objects like pulsars and black holes. Our Milky Way galaxy, bigger than the average galaxy, is some one hundred thousand million million miles across. That’s a 1 with 17 zeros after it.

$64,000: How long does it take Earth to go around the sun once?
A.) One day
B.) 30 days
C.) 365 days
D.) 365.2424 days

The correct answer is D. The period of time it takes a planet to orbit the sun is, by definition, that planet’s year. A look at the calendar shows that our year contains 365 days. But the length of Earth’s orbit has no direct correlation to its day. Every four years we add an extra day, making a leap year with 366 days. The rule is every year evenly divisible by 4 is a leap year, like 2008 and 2012. By adding these leap days, the average year becomes 365 1/4 days long. But the leap year rule contains a lesser known additional part. Only century years evenly divisible by 400 are leap years. Thus 2000 was a leap year, but 1900 wasn’t and 2100 won’t be. This addition makes the average year 365.2424 days long, accurate to within one day in 10,000 years.

$125,000: How does the size of the full Moon near the horizon compare to its size when high in the sky?
A.) Smaller
B.) Larger
C.) The same size
D.) It varies

The correct answer is C. The Moon is always the same size. You can prove this by comparing it to a dime when near the horizon and when high in the sky. But it can look larger than normal when near the horizon. This is known as the Moon Illusion. Our brain knows that the more distant an object is, the smaller it looks. This is the basic perspective that artists use to make paintings look realistic.

Studies show that we don’t perceive the sky as spherical, but rather as a sphere that is flattened overhead. That is, the horizon seems to us to be farther away then the “top” of the sky. So when we see the Moon on the horizon the same size as when high in the sky, but our perception is that the horizon is farther away, our brain makes the Moon appear larger to make the scene look right to us.

$250,000: When is Earth closest to the sun?
A.) January
B.) July
C.) We’re always the same distance
D.) It varies randomly from year to year

The correct answer is A. January. Earth is actually closest to the sun on January 4th and farthest from the sun around July 4th. Contrary to popular belief, distance from the sun does not create our seasons. If that were the case, it would be summer everywhere on the planet at the same time. But the seasons are reversed in the northern and southern hemispheres.

$500,000: What is the brightest star in the sky?
A.) Moon
B.) Venus
C.) Sirius
D.) The North Star

(Sound of a buzzer). Trick question. The sun is the brightest star in the sky. I didn’t say nighttime sky. We all know that, of course, but we sometimes forget the sun is a star. In fact, the only significant difference between our sun and the nighttime stars is distance. If you moved our sun as far away as the average distance of the stars you see at night, it wouldn’t even be visible without a telescope. Almost every other star you see with your eyes is brighter than our sun, but they’re just so much farther away they don’t look like it.

All who answered C. Sirius get to claim the prize. It is the brightest nighttime star visible from Earth.

Venus is not a star, although it is the third brightest object in the sky (behind the sun and Moon.) Nor is the Moon. Planets and moons are relatively small, cool bodies that don’t emit any light of their own. They only reflect the light from their parent star. Cloud-covered Venus reflects most of the sunlight that strikes it, making it very bright. The Moon is not very good at reflecting sunlight: only about 11% of the light hitting the Moon bounces off. This makes its reflectivity about the same as fresh asphalt! But being close, it appears quite bright.

When I ask this question during planetarium shows, North Star is the answer I receive about 95 percent of the time. It may be the best-known star, but it’s only the 33rd brightest star visible from mid-northern latitudes.

You may have never heard of Sirius. For the Northern Hemisphere it is up in the evening sky in December, January, February, March, April, and May. There just aren’t many people out stargazing during cold winter nights and spring months bring lots of cloud cover and rain, so most people rarely see it.

$1,000,000: What is the greatest threat stone-age humans faced?
A.) Saber-toothed tigers
B.) Rats
C.) Tyrannosaurus Rex
D.) Environment

OK, this isn’t exactly an astronomy question. On the face of it, anyway. But bear with me. Saber-toothed tigers were certainly fearsome. One of those overgrown incisors could make short work of a human. But we humans tend to defend ourselves in a coordinated way. We could outthink the big cats. Four-legged prey were easier to deal with and they don’t throw rocks or spears at you. By and large, humans aren’t prey animals, except when we prey upon ourselves.

Rats have played a negative role in human history. Most of the major plagues of the past several millennia were spread by rats and other rodents. But in stone-age times humans were rather few and far between, living in relatively small bands. There were no sprawling metropolises, and with this low population density, plagues, whether carried by rats or bad drinking water, just couldn’t spread very far.

It’s a misconception that humans and dinosaurs once co-habited this planet. Countless grade B movies probably had a lot to do with the belief in this myth. In actuality, dinosaurs disappeared from Earth 63 million years before the first humans appeared. No human, Stone-age or otherwise, has ever seen a living dinosaur.

And that brings us to the correct answer: D. Environment. Dinosaurs disappeared 65 million years ago when a six-mile wide asteroid slammed into Earth. The impact created the equivalent of a 100-Megaton nuclear blast. What creatures didn’t die from the initial blast were destroyed by fires and poisonous sulfuric compounds that spread worldwide. Smoke and ash from the fires created a thick, chocking cloud cover, blanketing the planet for a period of two years, blocking sunlight and killing off many of Earth’s plants. When the debris cleared, the dinosaurs were all dead, but among the survivors were some furry little mouse-like creatures that could burrow underground and live off of dead carcasses. They eventually evolved into all manner of mammals, including some intelligent chimp-like creatures that walked upright and eventually learned to make tools and create calendars based on natural phenomena like the daily rotation of Earth and its annual orbit of the sun.

A number of such mass extinctions have occurred over the history of Earth, all caused by acts of nature. Today, the biggest threat to the continued existence of humans may still come from space. An impact with a massive asteroid or comet could well do to us what it did to the dinosaurs. A powerful supernova explosion could potentially destroy Earth’s ozone layer, increasing your chances of sunburn or skin cancer, but that probably wouldn’t destroy the human race. If, however, that supernova explosion occurred at just the right time, it could be a real species-threatening event.

Our planet’s magnetic field protects us from harmful cosmic rays that come from, among other sources, supernovae explosions. However, Earth’s magnetic field isn’t constant over geological timescales. The north and south poles reverse in a rather chaotic fashion. It is not a sudden change; the magnetic strength ebbs and flows over a few hundred years, reverses and in fits and starts, rebuilds in the opposite polarity.

During the middle of such a reversal, terrestrial life may be vulnerable to cosmic ray bombardment. There is no evidence of a mass extinction being caused by such a reversal, but if Earth’s magnetic field were low or non-existent just as a powerful, nearby supernova blew, it could be pretty bad. Eta Carina is a massive star, some 150 times more massive than our sun and could explode as a hypernova in the near future, a much more powerful version of a supernova. That could potentially spray Earth with deadly levels of gamma rays and cosmic rays equal to two kilotons of energy over every square mile of the side of Earth facing the star when it blew. If THAT occurred without the protection of a magnetic field, life on Earth could hang by a thread.

End of podcast:

365 Days of Astronomy
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