Indexing Blog Posts

500+ posts is too many for me to keep track of, and quite a few are “reference” posts, such as the ones on planet building or horse coat color genetics. So I’m putting in a new feature, an index page that links to posts linking to the posts on a given topic. (Sound confusing? Try doing it!)

These indexing posts start today (see below) and will appear occasionally until the reference posts are all indexed. After that I’ll just be updating the index posts, which will be accessible from the Index tab above.

Why an Index?

With 550 posts as of today, I’ve started to have problems remembering what I’ve already put on here. This is particularly a problem with posting existing content such as poems, short pieces from the Summer Arts Festival, or science explanations originally written for the Alaska Science Forum. I can’t remember which books or DVDs I’ve posted reviews on. It also is starting to be a problem when I want to link to a previous post and can’t remember when it was put up or what the title was. And there are posts on this blog that have permanent information, like the series on planet building and the one on horse color genetics, or the book and DVD reviews. I want to make it easier for my readers as well as myself to find things.

I made a start some time ago by adding an index page, which can be accessed from the menu at the top of any page. Right now, the only links are to index pages on my author site. This takes you out of the site and sometimes back in, which is rather clumsy. The index list is also incomplete.

I’m going to start posting an occasional entry which is strictly an index of past posts on a particular topic. These posts will be linked from the index page, and will link forward to the individual blog posts. As it takes a while to find all the posts that belong together, this will be a slow process—probably extending over the next few months. The first in this series, on DVD reviews, is already queued for January 3. Others will follow, most on Thursdays.

I probably won’t be indexing every post. Some, like those early posts which were simply glossary entries for my books, are on the author site and really belong there. Others, like the regular Monday updates on North Pole weather starting in November 2010, can be found easily enough just by using the calendar on the site. But I hope that by the time I have finished this, older posts of interest will be easier to find.

Snowflakes

In the air, vapor’s swirling,
On the pond, folks are curling,
The vapor makes drops, the drops freeze and pop,
And six-sided snowflakes fall down.

On the lake, skates are gliding,
Overhead, clouds are hiding,
Ice in the sky is growing, oh, my,
And six-sided snowflakes fall down

Snowflakes could be square or five pointed,
Or octagons, or spherical, you know,
But water with water is jointed
So that only six arms can grow.

On the slopes, skiers swish on,
Snowflakes hide stars to wish on,
They fall through the air, and catch in your hair,
The six-sided snowflakes fall down.

The rhyme above can be sung, to the tune of “Winter Wonderland.” But it’s also a fairly good outline of why snowflakes look the way they do.

A water molecule is made up of one oxygen atom and two hydrogen atoms. The hydrogen atoms are not in a straight line with the oxygen atom, but are angled, like a bent line with the oxygen at the bend.

Ice, being crystallized water, is made up of water molecules in three-dimensional order. The water molecules in an ice crystal are held together by what are called hydrogen bonds — each hydrogen atom links not only with the oxygen in the water molecule, but with the hydrogen atom of a neighboring molecule. Given the shape of the water molecule, the easiest way the molecules can form an ordered structure is a hexagonal lattice. I’m not going to try to draw it, but there is a good drawing in this reference.

Most snowflakes actually start out as water droplets in clouds. A few droplets encounter ice nuclei as the temperature drops below freezing, and freeze into ice droplets. Sometimes the droplets explode to make many ice particles as they freeze, and each bit of ice can nucleate another droplet.

If ice and water are side by side at subfreezing temperatures, the ice will suck up water vapor from the water. The growth on the ice will be strongest at the sites where the crystal lattice juts out farthest, so the frozen droplet rapidly grows into something like a very short bit of a hexagonal pencil. The edges and corners of this hexagonal prism grow fastest, and sometimes even sprout arms.

Why are snowflakes often symmetrical, but different from each other? The type of growth is determined by the temperature and moisture of the air at the moment of growth. As each snowflake follows a slightly different path through the cloud, it will encounter a different sequence of growth than any other snowflake. At the same time, all of its six arms see the same sequence. The result is a snowflake that is fairly symmetrical but different from any other snowflake.

Very simple snowflakes – usually simple hexagonal plates or needles – may look very similar to each other. But the more complex dendritic snowflakes are generally one of a kind, because each has had a unique path through the cloud that spawned them.

We have snow of the ground now, here in Fairbanks, and many other areas farther south will soon. If you live in snow country, invest in a small hand lens and enjoy the myriad shapes of the snowflakes.

(Photos are from Bentley’s collection of snowflake images.)

Keeping Windows Dry

Air is a fair insulator, and one of the ways of insulating windows in a cold climate is to fasten clear plastic inside the windows, generally a couple of inches inside the pane. The problem is that moisture is frequently trapped between the window and the plastic sheet, leading to condensation on the window. Especially when the temperature outside reaches 40 below.

If you can get a tight enough seal that room air cannot get between the plastic and the window, there is a solution.

Ever heard of silica gel? You’ve probably run into it, in the form of the little packets used to keep things like pills dry. It’s also available in craft stores, for drying flowers. The kind I’ve gotten has tiny crystals in it that turn blue when dry and pink when moist. It soaks up moisture from the air when dry. When moist, it can be dried in the oven.

Have a small dish handy, of a size to fit comfortably on the windowsill between the plastic and the glass. Make sure the gel is thoroughly dry, and pour a few inches into the container. (I use small plastic glasses.)

The plastic I use has double-sided tape that is applied to the window frame, and I do the final drying while the tape is being applied. I then place the container of dried gel on the windowsill and apply the plastic, making sure I have an air-tight seal. The result? Windows that stay dry, even in the plant room.

Of course if the air is humid enough, condensation will still form on the plastic or the walls. But the window will stay a good deal drier with the gel than without it.

How Dry I Am

Suppose you live in a cold climate, and it’s winter. Paint is flaking off the walls. Your sinuses feel as if they were lined with a thin layer of concrete. House plants long for a vacation in the relatively moist Sahara. You stop slathering goop on cracking skin long enough to listen to the weather report, only to hear, “current temperature minus twenty degrees, relative humidity seventy-five percent.” Obviously, the weather service’s humidity has very little to do with the humidity where you live! But why?

Actually, if you measured the relative humidity outdoors, as the weather service does, you’d probably come up with about the same value they get. Contrary to general belief, Alaska north of the Coast Range complex does not have a particularly “dry” cold in winter. The only reason the humidity is not closer to 100 percent is because of the way relative humidity is defined. It’s the amount of water actually in the air divided by the maximum amount the air could hold if it were saturated, that is, if it had an endless reservoir of liquid water to supply moisture. This is a perfectly good definition at temperatures above freezing. Ice, however, turns out to be less effective as a moisture source than supercooled water (water which stays liquid below freezing temperatures), and in Alaska we tend to have an endless reservoir of ice in the form of snow, rather than water, in the winter. Our normal winter humidities near the ground are generally close to the maximum possible in the presence of ice.

Why, then, are we and our houses so dehydrated through most of the winter as to threaten spontaneous combustion?

The amount of water that a given amount of air can hold depends on the temperature of the air as well as on whether the air is in contact with ice or water. The air in a moderate size house — about 1325 square feet with eight-foot ceilings — would hold almost a gallon and a half of water at 68 degrees F. At 32 degrees F, the same amount of air could hold only about a quart and a half of water. As temperatures drop, the amount of water gets less — one and a quarter cups at zero, less than half a cup at twenty below, and a couple of tablespoonsful at forty below.

Now suppose we are maintaining the house temperature at 68° F. The air in the house is capable of holding almost a gallon and a half of water. But the same amount of air at outdoor temperatures is able to hold much less, especially if the effect of snow is considered. At forty below, for instance, an amount of outdoor air sufficient to fill the house, with an official relative humidity of 68 percent, will contain less than half a shot glass of water. When this outdoor air is brought into the house and warmed up to 68 degrees, it will still contain only half a shot glass of water, but will now be able to hold a gallon and a half, so the relative humidity of the outdoor air brought in and heated with no change in its water content will be about half of one percent. No wonder it is dry indoors in the winter!

Of course normal human activities — cooking, bathing, even breathing — are constantly adding water to the air indoors, and generally considerably more than is brought in with fresh air from outdoors. But beyond a certain point this extra water is removed by contact with cold windows and insulation. That, however, is a subject for a future column.

This article and its follow-up were originally published in the Alaska Science Forum. Next week I’ll talk about a way of insulating windows so they don’t fog up too badly.

The Geophysical Institute

“From the center of the Earth to the center of the sun.” The Geophysical Institute at the University of Alaska Fairbanks covers a lot of territory, and a lot of subjects. It started out with space physics and aeronomy, but has expanded its interests to include atmospheric sciences, seismology, remote sensing, snow, ice and permafrost, tectonics and sedimentation, and volcanology.

The building to the right is actually the International Arctic Research Center, but this is the building that now houses the GI's climate and atmospheric science program.

A large part of its work is cutting-edge research, but it also provides aurora forecasts, earthquake information, the Alaska Science Forum (a popular science feature distributed to media outlets throughout Alaska, which I once wrote) and volcano alerts. It maintains the world’s only scientific rocket launching facility owned by a university.

If you’ve read the bio on my website, you know that I spent more that 30 years  at the Geophysical Institute as a student, researcher and teacher. But what’s the Geophysical institute all about? What problems does it address? And what on earth does it have to do with writing science fiction?

I certainly can’t cover everything the Geophysical Institute does in a single article, but why not use this as my new article series for Sundays? As to what it has to do with writing science fiction, not much with the plots, but a tremendous amount with the planet building.

Next week I’ll try to give a little of the early history of the GI (as it is mostly called by those who work there.)

More on Ice Melting

I meant to post on the leopard gene in horses today, but I just didn’t get the post finished. I took a few more pictures of melting ice yesterday, so I thought I’d put them up for today.

Note the difference between the left side of this block, which has been exposed to strong sunlight, and the side facing the camera. This particular block is either in the same orientation it had in the pond or upside down, as shown by the vertical fabric of the sunburned ice.

This coumn was a little better sheltered, but there is still some solar melting on the right side. Notice the clarity of the shaded ice.

The middle part, between the clear ice on the left and the wood on the right, shows the intergrain boundaries as seen from the end. This block must have been turned on its side relative to its original orientation.

The blocks for the single-block competition are 8′ by 5′ by 3′ and weigh a staggering 7,800 lb each. Needless to say, they are positioned by power equipment! The multi-block competition can have up to 4 carvers and use up to 10 blocks of ice, but the blocks are smaller–a mere 3′ x 4′ by 6′. Repositioning and stacking these blocks is done by cranes, and the crane operators really have a job hoisting these delicate carvings into precise position. Aside from Harvest Moment, the photos in yesterday’s post were all single block.

Why 12-Hour Days Already?

We broke 12 hours of daylight Friday, 2 days before the equinox. Why? And is this just due to my being close to 65 degrees North, or is it a more general anomaly?

There are two parts to this peculiarity. One is latitude combined with the finite diameter of the sun, which can be calculated. The other is the refraction of the atmosphere, which varies from day to day and can only be estimated.

Let’s take latitude first. Sunrise and sunset are defined as the time that the upper edge of the sun is just visible above a flat horizon. “Equal days and nights” (which is what equinox means) assumes the dividing line between day and night is the time when the center of the sun is on the horizon, assuming light moves in straight lines. If the sun rose vertically, as it does at the equator, it would rise at a rate of about 1 solar diameter a minute, and the calculated sunrise time based on the center of the sun would be only half a minute after the time the upper edge first showed.

At higher latitudes, however, the sun appears to rise at an angle and sunrise and sunset appear slower. At 65 degrees latitude the sun’s path at the equinox is 65 degrees from the vertical, and a little trigonometry stretches that half minute to about 1 minute 10 seconds, or twice that in day length. Latitude alone is still not enough to allow our days to be 12 hours 15 minutes long at the equinox. For that, the refraction of the atmosphere becomes important.

The apparent break in the spoon handle is due to refraction.

Everyone is familiar with refraction, though you may not know it by that name. The optical illusion of a broken spoon in water is caused by the fact that the speed of light in water is less than that in air. Yes, the speed of light in vacuum is constant, but in any other transparent medium it moves a little slower. When it crosses a boundary between two transparent media with different speeds of light, any light rays not moving at a right angle to the boundary are bent. Air is one of those transparent media, and while the speed of light in air is not a great deal slower than that in vacuum, there is enough of a difference that the bending affects what we can see.

The actual difference in speed depends on the density and moisture content of the air, which in turn depend on pressure, temperature and relative humidity. Air near the ground is almost always denser than that above it, and this is particularly true at sunrise. The change with height is gradual, and thus the light rays are not bent sharply, as in the water-air interface, but curved along the earth’s surface. Objects far away appear higher than they are, and this certainly applies to the sun at sunrise. The amount by which the sun appears higher in the sky than it really is will depend the atmospheric density and how it changes with height.

For practical purposes the time of sunrise is calculated assuming that the upper edge of the sun is visible when the center of the sun is 50 minutes of angle—almost a degree—below the horizon. This also means that the sun at the equinox will rise not quite due east, as it “rises” while it is still physically below the horizon and slightly north (in the northern hemisphere) of east. The difference, however, is slight.

Refraction is also responsible for the fact that the sun appears to flatten as it approaches the horizon when setting or just after rising. The part of the sun closest to the horizon is more strongly affected by atmospheric refraction than is the upper part of the sun, so the two appear pushed together and the sun appears flattened, rather than round. I’ve probably overused this in Tourist Trap.

Momentum and Teleportation

Teleportation in Homecoming requires that energy, momentum, angular momentum and mass be conserved—all basic laws of physics. We’ll skip mass and angular momentum for right now, and just look at the situation where something is moving in a straight line.

Anything that is moving has both kinetic energy (energy of motion) and momentum, but the two are not the same. The difference is usually expressed mathematically: energy is half the mass times the square of the velocity and momentum is the mass times the vector velocity, but for many that just makes if more confusing. Let’s try this, instead. (If you don’t understand mass, think weight.)

Consider a car. Let it be a big, heavy car, say an SUV. Suppose it is coasting at a steady speed, say, 30 miles an hour to the west. Can a mosquito stop it by hitting the windshield? Not likely! The car’s resistance to having its steady motion changed is due to its momentum. This momentum has a direction—the direction the car is moving. Friction will slow it down, eventually, by transferring its momentum to the earth, but for the moment we’ll ignore that.

It also has kinetic energy. If the speed is doubled, the momentum will also double—but the kinetic energy will increase by a factor of four.

Remember momentum has a direction. Suppose we have another SUV moving 30 miles an hour to the east. Speed to the east and speed to the west cancel, so the momentum of the two-car system is zero. Their kinetic energy does not cancel, as can be seen if the two cars meet head-on—when the dust settles, they will be stationary at the point where they met. But the energy will have gone into crumpling metal (and whatever else makes up the cars) and ultimately into heat.

It is possible for two objects to bounce off of each other in such a way that energy, as well as momentum, is conserved. But if the momentum adds up to zero before the impact, it must also add up to zero after the impact. This is a common problem in billiards, though in this case the balls are most often moving at angles to each other so the vector sum of the momentum is not zero—but it will still be the same after the collision as it was before.

The conservation of momentum, in fact, nicely encapsulates Newton’s laws of motion.

Now consider Roi’s problem in teleporting to a very different location. He is moving with the planet under his feet. For illustration, let’s assume he is on the equator, at sea level, at sunrise, and wants to go to the opposite hemisphere, also on the equator at sea level, but at sunset.

Assuming he is on a planet like the Earth, he is moving toward the sun at around a thousand miles an hour, and the area he wants to teleport to is moving away from the sun at the same speed. No change in kinetic energy, but if he doesn’t do something about momentum, he’ll arrive moving about two thousand miles an hour relative to his surroundings—not a very survivable teleport!

My solution is strictly science fiction—I assume it is possible for a person (or a machine) to transfer or “swap” momentum from one mass to another. But they’d better remember to do it!

Mass into Energy

“If you can Heal, you may eventually be able to exchange mass and energy if you conserve hadrons,” Derik told Roi. (from Homecoming.)

Exchange mass and energy? And what are hadrons?

Einstein’s famous equation—E=mc²—says that a very small amount of mass can be turned into a very large amount of energy or vice versa. If you could turn a gram of mass (that’s about the mass of a small gourmet jellybean) into energy, you’d get roughly 25 million kilowatt-hours. In practice, you have to conserve hadrons—essentially the total number of neutrons and protons in the cores of atoms, which make up most of their weight.

Thus it is possible, with enough heat and pressure, to force four hydrogen atoms (each with one proton and one electron) together to form one helium atom (with two protons, two neutrons and two electrons.) The four hydrogen atoms turn out to have about 1% more mass than the helium atom, and this extra mass, the binding energy, reappears as gamma rays and particles. This is the energy of the hydrogen bomb, and also the energy that powers the sun and most of the stars. The process is called fusion (coming together), but as of yet we cannot control it. (I don’t think you can call a hydrogen bomb controlled.)

A second way in which mass can be transformed into energy involves very heavy elements, such as uranium. It turns out that all of the protons and neutrons packed together in these elements aren’t really happy. They may split apart on their own, or because they are hit by some other particle, but the net effect is that the mass of the parts they split into is less than that of the original atom, so the split produces energy. This is nuclear fission (splitting.) This is the energy of the original atomic bomb, but it is also the energy that drives plate tectonics and volcanoes, and is occasionally tapped for geothermal energy. This one we can control to some extent, and it is the energy source for nuclear power plants—but those large, unstable atoms are rare in nature.

The middle-weight elements—such as iron—are stable. There is no way to extract binding energy from iron—it is sometimes called the nuclear ash of stars. (Note that many of the elements of all masses have isotopes in which an imbalance between neutrons and protons leads to instability, but these are very rare in nature. They are very important in man-made nuclear waste, however.)

Most of the energy we use today comes from sunlight past or present—fusion energy. Solar energy intercepted by the earth today fuels not only what is called solar energy but also wind power, hydropower, and biofuels. These are all “renewable” sources—we can use them at the rate present-day sunlight generates them. But they are limited by the amount of sunlight available.

Fossil fuels are storage for the sunlight of the past—and we are using them up far faster than they can be replenished. Only a tiny fraction of the sunlight falling on the surface of the earth is actually captured as biomass, and only a tiny fraction of that biomass is buried and eventually becomes coal, oil or natural gas. But ultimately, it is all nuclear energy.

So yes, mass can be turned into energy, and in fact almost all of the energy we use actually comes from such conversion. But there are limits.