31 May 2010
Last time here we learned about the names of the first four planets from the sun, the terrestrials. Now we hit the Giants in the outer solar system, and a distant dwarf.
The "gas giants," Jupiter and Saturn, are the last of our planets observed by the ancients. (Neptune and Uranus have only "recently" been discovered.)
Jupiter is the Roman equivalent of the Greeks' Zeus, the leader of the club, the Big God on Campus. His name, derived from Latin and earlier languages, roughly translates to Father God, but probably more for his siring prowess than his paternal instincts. You can still see the "father" - Latin "pater" - in his name. Coincidentally, he was the father of Mars.
Many of us think that Jupiter (or Zeus) was the main guy and that most of the myths revolved around him. Not so. Did you know that in the pagan pantheon Jupiter had a dad? His name was Saturn. The stories involving Saturn and his brothers and sisters are rich and numerous, if not also contradictory and varied. You've probably heard of the Titans and Cyclops; they were a part of this rich mythological time.
One story involved Saturn and his own dad, with whom he did not have the best of relations, whom he ends up castrating! Saturn's father was God of the Sky, his mother was Mother Earth. Her name in the Greek myths was Gaia, his Ouranos; the Latin version of which is Uranus.
Uranus, the ice giant planet, was too dim to be seen by the ancients. It wasn't until 1781 that scientist William Herschel, with telescope, discovered it. Herschel wanted to honor King George III, his benefactor, and call the planet George. Others suggested Herschel. Thankfully, more reasonable minds prevailed and the planet was named Uranus. Now there was Mars, son of Jupiter, who was son of Saturn, who was son of Uranus. Son of a gun, that's works out nicely.
But what about Neptune? Discovered in 1846, it, too, went through a little naming controversy, with one proposed name being Le Verrier after one of its discoverers. But again, in keeping with tradition, the scientific community named the planet for a mythological figure, here a brother of Jupiter, god of sea and water, Neptune.
There is one more celestial body out there we should mention out of respect. Although no longer considered a planet, it is part of our planetary heritage. Discovered in 1930 by Clyde Tombaugh, the name Pluto was suggested by a little girl in England who knew her mythology and figured since the planet was probably cold as heck, that it should be named for the god of the underworld. And so it was named after Pluto, also a brother of Jupiter.
There are the Original Nine, complete. Until next time, clear skies!
17 May 2010
Part of a more complete understanding of the skies above involves knowing not just the names of objects up there, but how they got their names. Today we will look at the names of the first four planets, the earth-like planets. Next time we will hit the outer giants, and a dwarf planet called Pluto.
Of course, every culture has its names for the planets, but we will focus here on those handed down to us in the west from the Babylonians, Greeks, and Romans thousands of years ago.
The skies back then were sacred, the abodes of the gods, and a place reserved for the great stories of deity and heroes.
But the planets - the word itself comes from a Greek word meaning "wanderer" - weren't fixed in the skies as were the stars. They moved. They were something unique and set apart. Hence, for the most part, they are named for the Big Gods on Campus.
Let's start with Mercury. For millennia humans have noticed a little pin prick of light that hugs the sun, sometimes at sunrise, sometimes at sunset. This little guy would move noticeably through the skies not over months and years, but in days. It was quick, so what better god to represent it than the fleet-of-foot Roman messenger god, Mercury ("borrowed" from the Greeks' Hermes).
Venus, second from the sun, represents the only female deity of the lot. The Babylonians first named it after their goddess of love, Ishtar. The Greeks followed suit soon after, naming the planet after their goddess of love, Aphrodite. And of course the ever-borrowing Romans followed them both up by naming the planet after - you guessed it! - their goddess of love, Venus.
Mars' name may have been influenced by its color. Its light reddish hue may have typecast it into a violent role. The Greeks called it Ares, after their god of war. Later, the Romans, sometimes not the most creative people, gave us the name Mars after their god of war.
What about Earth? Well, until the Middle Ages our planet wasn't really a "planet" in the ancient sense of the word, i.e. a wanderer in the skies. Our word "Earth" is from the Old English word "eorthe," which meant the land or ground or soil, which it still means today when we say, "This is good earth for growing corn." Well, the term stuck around, going global around the 1400's to mean our whole planet.
Who is up next time? The big guys... and one tiny dwarf.
03 May 2010
In my class I have hanging from the ceiling on a string a pencil, parallel with the ground, with some magnets taped to it. The carefully ordered magnets force the pencil to point north. This homemade compass is a simple, but elegant, everyday display of our planet's magnetic field.
And what a field it is!
Our magnetic field reveals to us what is going on down below our feet, helps us find our way on the surface, and protects us from destruction above. How?
Through some complicated physics, it has been shown that a magnetic field can arise from a rotating, conducting fluid. Meaning, if a planet has a sphere of liquid iron down below the surface, the rotation of that planet can cause the liquid to throw a protective magnetic shield around the planet. The field is similar in shape to that taken by iron filings around a bar magnet, like we all saw in elementary school.
We believe that way down below, at the center of planet earth, we have an "inner core" made of very hot - but solid - iron and nickel. But surrounding that we have a molten, swirling "outer core" of liquid nickel and iron, perfect conditions for a magnetic field.
On our surface we can take advantage of this magnetic field with a compass, which has a magnetized pointer that lines up with our magnetic field and allows us to find magnetic north (which is not exactly true north, but close). This has allowed people for centuries to find their way around this planet, and has saved many a lost soul.
Way above us, our all-encompassing magnetic field interacts with pesky charged particles. So what? So this...
The sun bathes us in a wind of charged particles called - surprise - the solar winds. Composed of mainly protons and electrons, this wind travels at hundreds of miles per second.
But instead of those bothersome particles blasting into us and wreaking havoc on our atmosphere - especially on poor water vapor which it can strip from a planet - our magnetic field steps in and calmly says, "Wait a minute, here."
The laws of nature ensure that our magnetic field will deflect the charged wind around earth and by us, like a sailing ship forces the waters aside and around.
Some of the particles do manage to sneak in through the weaker areas, around the earth's poles. As they crash into the atmosphere they light up the skies in beautiful Northern and Southern Lights.
If you ever see the Lights, or just play with a child's compass, pause. You are witnessing the effects of a remarkable planetary phenomenon.