Thursday, December 04, 2008

Advent 2008: Week One Thursday

Yes, it's Thursday and we have audience participation. Fun stuff today!

First, here is the picture I ought to have shown yesterday, with the five water molecules:Remember this is really to be thought of as three-dimensional. Someday I will get it drawn with shadows and stuff to give you a better clue (yes I can spell perspective, but have a tough time drawing it with this little round mouse thing. Sorry.)

The next time you pour yourself a glass of water, take a good look at it. You won't see what I am going to tell you about today, but you'll need to remember it as we proceed. Let's make a tinylittle box, a cube one centimeter on each side - that's about the width of the fingernail of an adult's little finger, or about two and a half in one inch. Now, take that box and take your sharpest knife and cut it into ten million little slices, take one of those slices and cut it into ten million little strips, and take that strip and cut it into ten million little very little cubes. Each of those cubes (you would have 1,000,000,000,000,000,000,000 if you cut up your whole little original cube) has enough room to fit about 33 water molecules.

Now I know that is a rather tough exercise in imagination, and it is about to get even tougher.

You see, as hard as it is to imagine these bunches of really tiny little balls in the first place, you have also to remember that they are not just little balls. They attract and repel and stick and bounce around. The stick and bounce because they have that "partial dipole" - the fractional charges which make them act like magnets to each other. They move because they are warm. Yes, the startling fact for the outsider to understand when you go into the submicroscopic (molecular) world, or come back out to our "macroscopic" world, is that what we call "heat" up here is called "motion" down there.

And these things are hauling. Assuming I did both the physics and the math correctly, the average (actually the "RMS" velocity) for water at body temperature (98.6°F or 37°C or 310°K) is about 657 meters per second, or over 1460 miles per hour! Now, not all are going that fast, but some might go faster; also, not all of the energy is translational (more on that in a moment). Also they don't go very far, since there are lots of other water molecules around for them to bump into, and they will bounce like pool balls off the bumpers.

I said that not all the energy is "translational" - translation in this context means moving from place to place. There are two other forms: they rotate, and they vibrate. The bond from the oxygen to the hydrogen (the -OH bond) is kind of like a spring, and the balls can "wobble" a little. Not very far, of course, and yes, the H can come off, but in pure water only one of every ten million will be that way. (They usually don't come apart unless you do something nasty like send electricity through it - no, not even heating will do it.) Ah, you now know the secret of your microwave - like the singer who shatters the goblet, the device in a microwave oven "sings" the radio frequency which matches the -OH bond, and makes it wobble. Remember, motion in the tiny world is heat in ours? Yes. So that's how it works.

What does all this mean? I needed to tell you this so I could explain a little about that word "osmosis" I used last time. Things are moving around down there, and unless something is "tied down" somehow, it will get shifted all over the place. You can demonstrate this very easily. Time for an experiment!

Go away from home (or one room) for a while, and come back, and bring a lemon and a knife and a dish. Close all the windows and doors, and turn off any fans or heaters or things that make the air move mechanically. Go into one corner of that room and cut open the lemon, carefully, so you don't get any juice on yourself, and put the lemon and knife on the dish, and sit the dish in that corner. Don't let anyone meddle with it - if there are others around, they ought to sit quietly and help you. Then go into another corner, and wait. (You might pray or otherwise be useful in the meantime.) Soon you will smell the lemon. This is called "dispersion of a fragrance", but it works because the air is in motion, even without a fan. (Ah citrus things smell SO good!)

Here's another, maybe even more fun. You'll need the biggest bowl or jar you have - glass if possible - and a bottle of blue food colour. (Don't use ink, and DO NOT use the bathtub! I remember a Calvin and Hobbes comic... Ahem.) Fill your glass vessel with water, and sit it somewhere where it won't get shooken, while you relax and do something else (maybe pray, we need prayer!) for a while, until the water isn't visibly sloshing around. OK, now go over to it, very carefully, (DON'T BUMP THE TABLE) come VERY close to the water and GENTLY ONE SINGLE DROP of the blue into the water - then stand back.

If you have some time, you may sit and watch (why not pray as you watch, like Jesus told the apostles in the garden of Gethsemani?) Watch as slowly the blue seeps all over - and soon the whole vat is completely coloured. Amazing. No stirring!

That's also diffusion... and osmosis is (in a simple sense) the same thing. At normal temperatures, stuff seeps through fluid or gaseous mediums like air or water.

That's how many one-celled creatures get their nourishment. (There are a few who have other tricks to get their food.) It's fine, very easy for tiny things, but as soon as we have a somewhat bigger organism, we need to use those other tricks. Which means eating, if we are talking about food. But you have to remember, that each cell needs food, not "the organism". What good is a steak to a bacterium? Or to your toe? Or your left ventricle or your brain? (Hee hee. Ah,but do you hear St. Paul? The eye cannot say to the hand... [see 1:Cor 12] But hush, we'll do that someday.) Now when we were one-celled, and for a few days after, we got all our nourishment by osmosis. There's always "edible" matter floating around living beings - one of the lesser-known systems of the body, the "lymphatic" system, is in charge of managing the stuff that seeps out and would get out of control otherwise. And as hard as it may be to believe, for those who have a problem with that line in the gospel about the poor we will always have (Jn 12:8) there are "poor" cells in our bodies who literally make their living by osmosis from their neighbours: those in the cornea and lens of the eye, which have no blood vessels!

But as we heard last time, osmosis won't do the trick for organisms of any significant size. (Or rather, there has to be an arrangement to permit osmosis for every tiny bit of the organism!) So the first system that is built by every growing "large" organism is a "transport" system. In plants there are various "vascular" arrangements; in insects, birds, fish, animals and Man, there is one or another form of circulation. There is also (usually built a bit later on) some arrangement for handling food, known as the digestive system; how food is managed before it is ready is yet another part of the cunning plans. If you find this stunning, try finding out how a computer starts running. Unless you work for one of the big companies, you will probably not ever get to see the code, but at least it is somewhere, maybe locked up in a vault. (I've seen it for an old computer, and I also know the principles involved). God doesn't show His source code, but after a century of serious work we have some idea of how it is done.

Here, you may understand, is a hint to myself: someday I will have to talk about embryology and development as it is tied to computer science. All software is a matter of plan and design, and the more complex the system, the more details must be specified in the designs. It is as futile for a biologist to avoid computing nowadays as it would be to avoid chemistry! But let us get back to the water. Er. Next time.


Post a Comment

<< Home