On Monday, September 22, the M. D. Anderson Planetarium presents….

Water on Mars, Life on Mars

On July 31, 2008, the Phoenix Mars Mission team announced the first direct evidence for water on the desert planet Mars. In this special presentation, we will take a look at Mars, what we know about it, and what we hope to learn in the future. We will see

• how Mars is similar to Earth, and how it is very different;
• why water is so important to Earth, and what it might mean for Mars;
• what finding water on Mars means about the possibility of life on Mars;
• and other exciting topics!

I hope you can join us on September 22 at 7:30 PM.  As always, admission is $5 per adult, $3 per child under 18, and $10 for a family of 3 or more. Lambuth students, faculty, and staff are admitted free with their ID.

Posted by Matthew R. Francis under Public Events & Science Ideas & Science News | No Comments »

This Wednesday (September 10), the world’s most powerful high-energy physics experiment will begin operation.  The Large Hadron Collider (or LHC), part of the European international experimental facility CERN, is one of the most anticipated projects in all of physics for many years.

So what does the LHC have to do with astronomy?  Why is your intrepid planetarium director excited about this, when it doesn’t seem to have any relation to the usual stuff we talk about in the planetarium?  The answer lies in the mysterious substance known as dark matter, which comprises more than 20% of the contents of our universe.  In contrast, ordinary matter—atoms and molecules, which is the stuff of our bodies and our planet—only makes up about 4% of the contents of the universe.  (The rest is an even more mysterious substance known as dark energy, a subject best left for another essay!) Continue Reading »

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In August 2006, the International Astronomical Union (IAU) voted on a definition of “planet”. To be considered a planet,

1. The object must be large enough to be spherical under its own gravitational force.  This is a general principle:  if a chunk of rock or a ball of gas has enough mass, it tends to become spherical just because that’s the way  gravity works.  Smaller objects, like pebbles or baseballs, can be spherical for other reasons, namely erosion or forces other than gravity, so some Solar System bodies lie on the boundary of this criterion.  Two examples of this are the asteroids Vesta and Pallas, which appear to be roughly spherical, but might not quite be massive enough to count.
2. The object must orbit the Sun directly.  Certain moons, like Ganymede (which orbits Jupiter) and Titan (which orbits Saturn), are actually more massive than Mercury, and Titan has a thicker atmosphere than Earth.  However, since they orbit planets rather than following a direct orbit around the Sun, they don’t count as planets in their own right.
3. The object must dominate its orbit.  In other words, the body must be the most massive object in its neighborhood.  It also, by virtue of its gravity, cleared most of the smaller objects out of its path, so that impacts won’t substantially change its orbit.
4. The object must be small enough that it doesn’t emit its own light via nuclear fusion.  Planets don’t emit their own light:  we see Venus, Jupiter, and the like by the light they reflect from the Sun.  Stars like the Sun, on the other hand, compress the hydrogen atoms in their cores so much that they fuse into helium, releasing a huge amount of energy in the form of light.  This criterion isn’t terribly important for our Solar System, since Jupiter (by far the largest planet) comes nowhere near the threshold for becoming a star.

Continue Reading »

Posted by Matthew R. Francis under Science Ideas & Science News | 2 Comments »

I am still feeling my way about what kind of website to offer for the planetarium.  Being a scientist who engages in active research in addition to my educational roles (I’m a full-time professor at Lambuth as well as planetarium director), I think it’s important to share discoveries that might be interesting to you, the reader.

So I would like to take an informal poll:  do you read the science postings I have started writing recently?  If you do, what kinds of things would you like me to talk about?  Please send any questions, comments, or suggestions to planetarium@lambuth.edu, and I will use them to help provide the kind of site people will want to read.

Cheers,
Matthew Francis
Director, M.D. Anderson Planetarium

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Is there water on Mars?  We know the answer is “yes”, since Mars has ice caps at both poles that grow and shrink with the seasons.  The real, harder questions are:  how much water is on Mars, and where is it located? Continue Reading »

Posted by Matthew R. Francis under Science Ideas & Science News | 1 Comment »

Over the last 100 years or so, our view of the universe has changed dramatically.  It was possible in the early 20th century to think that our galaxy (literally meaning Milky Way, same root as “lactose” and “lactate”) might be the entire universe.  The famous “Great Debate” between astronomers Harlow Shapley and Heber Curtis was over whether the observed “spiral nebulae” were part of our galaxy, or separate galaxies in their own right. The issue wasn’t settled during the debate, but several years later by Edwin Hubble, who used techniques developed by Henrietta Swan Leavitt to measure the distance to the Andromeda galaxy.  Needless to say, he found the distance to be much larger than the size of the Milky Way, thus showing the universe to be a very large place.

Edwin Hubble (1889-1953) and Henrietta Swan Leavitt (1868-1921)

Continue Reading »

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On this date (May 29) in 1919, Arthur Stanley Eddington and his crew traveled to the island of Príncipe off the coast of Africa to observe a total solar eclipse. Solar eclipses, which occur when the Moon’s shadow falls on Earth, aren’t all that rare, but this one was important: it was the first total eclipse after the First World War, and the first after Albert Einstein predicted the bending of light by gravity. In other words, the gravity of the Sun (and indeed any massive object) will affect the path that light takes from distant stars. As one of the most significant predictions of Einstein’s general theory of relativity (first published in 1916), the bending of light due to gravity needed precise measurements to prove it was happening.

Usually, though, the Sun’s light overwhelms the light from stars, so the effect of gravity is not detectable under ordinary circumstances—which is why Eddington needed to make his observations during a solar eclipse, when the Moon blocks much of the Sun’s light from reaching Earth. The effect of gravity showed up by comparing the position of stars during the eclipse to their position when the Sun is in a different part of the sky—the bending of light by the Sun makes the stars appear in different places.  (Sizes and positions are exaggerated for clarity!)

Continue Reading »

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