28 Mar 2005
Water - it’s a blessing, it’s a curse. Well, for a self-centered astronomer it’s a curse anyway. Those darn clouds and that blasted rain and snow can ruin a night’s costly observing run at a premiere scope, indefinitely postponing important research.
And we amateur astronomers here in southern California have had to deal with plenty of the meddlesome wet stuff this year. Just a week ago our astronomy club had to cancel another star night for a local elementary school. A perfect cosmic setting - above all those clouds – passed over.
But how about for a moment we take off our astronomer’s cap, rimmed with a fringe of bad attitude, and just sit back and admire the tiny water molecule and see how utterly unique it is.
Composed of just one oxygen atom bonded to two hydrogens, water molecules are tiny to be sure. And molecules as small as water are almost always gases. Nitrogen, oxygen, and carbon dioxide - all bigger than water - are all gases in our atmosphere. There is no chance under present conditions that we will get an oxygen downpour or a nitrogen snow storm.
They don’t liquefy naturally on our planet because they just are not very “sticky” at all, and at these temperatures the little guys are moving just too fast to have any chance of holding on to each other. Then what gives smaller, faster water molecules the right to stick together so well that they not only form a liquid on our planet but a solid, as well?
It all has to do with the shape of those wee beasties. Because of the laws of physics, water is shaped like a little Mickey Mouse balloon. Imagine Mickey’s head as the oxygen atom and his two ears as the bonded hydrogens. So what? Well, this shape effectively gives water a slight charge.
The bonds that hold it all together are made of electrons and the oxygen has this greedy tendency to pull those bonding electrons more toward itself, away from hydrogen.
This means the oxygen has what’s called a “partial negative” charge on it. The hydrogens get stuck wearing a “partial positive” badge. So what we have here is a molecule with a negative side (Mickey’s head) and a positive side (his ears).
You can actually see this charge with a tiny experiment. Comb your hair to a fare-thee-well on a relatively dry day (remember those?). Bring the comb up to a thin, smooth stream of water from the faucet. The watery stream, attracted to the static-electrically charged comb, will bend towards it.
What’s this all got to do with the miracle of water? This charged character of water means that the little guys are attracted to each other – and rather strongly at that. This attraction allows them to stick to each other like socks to pants fresh out of a dryer.
This stickiness means they don’t mind congregating in the b-zillions to form tiny invisible droplets suspended in the air. If cool enough, these tiny droplets don’t mind at all clinging to each other, becoming big enough to be seen, as in fog or clouds. If conditions are right, these megadroplets don’t mind then gathering into conglomerates so big that they can fall as raindrops.
And the beauty of it all is that they aren’t too sticky. With a little energy thrown their way, the stickiness can be overcome and they are off by themselves again.
Just think of how important that is. Water molecules in oceans are sticking together. But at the surface where the water molecules are exposed to the pounding energy of the sun, they can leave en masse. They evaporate purely, leaving their salty ion friends behind.
Carried aloft they can travel literally thousands of miles. Cooling, they stick and fall as rain, injecting new life into an area, with the excess flowing back toward the ocean to start again.
Bottom line: That little molecule called water has been engineered so brilliantly – perfect size, shape, charge, etc. - that it can be transported deep into dry continents assuring life virtually everywhere on this great rock of ours.
Should I also get into the stunning ability of water to dissolve all kinds of stuff, allowing everything from erosion to the biochemistry in every cell of every living creature?
Should I elaborate on one unique property of water, unlike just about every other compound in existence, to actually become less dense when it is frozen, thus allowing ice to float rather than sink? Ice that sinks would turn our world into a giant iceball.
And on and on and on…
Yes, clouds and rain can wash out an otherwise perfect night of observation. But that little molecule, with its two H’s and single O, is a great work of art, worthy of observation in and of itself.
13 Mar 2005
But fear not! Before you begin suffering through those mind-altering flashbacks of pop quizzes you were forced to take in school, know this: This will not be graded, no letters will be sent home. You are only required to think, have fun, and simply classify the following statements as true or false.
1. The Sun burns stuff. It’s really nothing more than a big fat fire.
This is a common belief. And it makes common sense if you think about it. We see fires all over the place, from the fireplace to the forests. And we see the bright hot surface of the sun looking pretty similar. So the sun must be burning fuel just like these terrestrial conflagrations, correct?
Not really. The sun is hot because of a process called nuclear fusion. That’s when tiny atoms like hydrogen are smashed into other tiny atoms and fuse together to make bigger atoms like helium. When this happens some of the mass of the tiny critters is converted into enormous amounts of energy.
The “burning” the sun does down at its core is more like what goes on in a thermonuclear device, à la the fusion bomb. But instead of mere pounds of bomb material converted to energy, the sun converts over 4 million tons of matter into energy every second! And amazingly, even at this rate, the sun has enough fusion material left to “burn” for billions of years. Answer: False
2. Meteor showers rain down havoc on the earth! Everybody duck!
Meteor showers can be very dramatic fire-in-the-sky events but they are thoroughly harmless. They are just dusty debris from passed-by comets slamming into the atmosphere of the Earth. On average they are about the size of a grain of sand. But get them going at speeds of tens of miles per second and they can light up in a long fiery trail.
Most all the “shooting stars” we see are like this – whether part of a meteor shower or the strays we see occasionally flying solo through the night sky. They rarely make it to the ground, but their vaporized carcasses do give us tens of tons of extra new dust each day! Think of that next time you’re dusting behind the bookcase: you are probably wiping up some comet gut particles along with all the rest of the schmutz. Answer: False.
3. An asteroid or comet slamming into Earth will destroy the planet!!!
Imagine driving down the freeway at a good clip. Suddenly, without warning, a savage nectar-sucking butterfly flies right into the direction of your oncoming vehicle! Too late to react, the butterfly smashes into your front end splitting your car in two, both halves now careening off the road in different directions in a duel fireball of destruction.
This won’t happen, of course. The mass of the butterfly is way too small to cause any damage to your car other than an unsightly gooey mess. Asteroids and comets, even the bigger ones, are just miles, maybe a couple tens of miles across on average. When they hit Earth, which stretches thousands of miles through, other than leaving an unsightly crater they don’t do much damage to the planet at all. But they can really hurt the atmosphere.
Once they plough through Earth’s atmosphere and into its mantle they explode and hurl molten material literally all over the planet. This worldwide firefall ignites infernos everywhere, which pollutes the air on a global scale and shrouds us in darkness. Rainfall comes down as acid rain now, poisoning waters everywhere. Plant life suffers greatly. Being the bottom of the food chain, plants directly impact all the rest of life on earth. Lose those and mass starvation runs rampant.
Moreover, the sudden climate changes affect the complex, sensitive creatures the most, driving many to extinction. Earth is not a fun place to be for years. But the planet itself spins on, essentially unaffected. Answer: False.
Well, how did you do this time? Don’t worry if you got most wrong; these are all common misunderstandings. And, as my parents used to say, there’s more where that came from! In coming seasons we’ll try and debunk some more of these cosmic misconceptions.
Until next time, clear skies!