science

SF World Building with Polymers

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So you want to design an extrasolar planet for your hard-SF story, and cast about your house looking for ideas.  There, you find all manner of of man-made materials:  polystyrene coffee cups, polycarbonate eyeglass lenses, PVC pipes.  Nothing could be farther from the natural, organic compounds of life, right?

Wrong.Polystyrene_formation

Polystyrene, polycarbonate, and PVC are all examples of polymers, a class of chemical compounds made by bonding sequences of smaller chemicals (“mers”) together into long chains.  We didn’t think of this concept first, though.  Consider the following examples of polymers from life:

  • Cellulose, the building block of trees and the roughage in your whole wheat bread, is a polymer made up of sugar molecules strung together into long chains.  It is a polysaccharide.
  • Proteins, which provide structure to cells and control the chemistry of life, are built from sequences of amino acids linked together.  They are polypeptides.
  • DNA, the design template of life, is built from long chains of base-pair sequences.  It is a polynucleotide.

It would seem, therefore, that whenever a big molecule was needed in nature, a polymer was used.

What does this mean for the chemistry of world building?  Pretty much any polymer chemical invented by man might exist naturally in the life chemistry of a distant world.  Imagine a world where animals use lightweight PVC as a skeletal material instead of the protein collagen.  Suddenly the need for calcium in the diet is greatly reduced, but the need for dietary chloride is increased.

Of course, a world that makes use of PVC is going to be subject to all the chemical problems that PVC might have.  For example, PVC is degraded by exposure to ultraviolet light.  It might, therefore, not work well on earth, but might be effective on a world that orbits a red dwarf sun, or one with an extremely dense atmosphere.

If a compound exists naturally, however, it is more likely to be part of the food web.  We can’t digest cellulose, but cows can—and so can many bacteria.  If animals use PVC as a structural material, there will certainly be other animals and bacteria with the enzymes to digest it.

Modern man is surrounded by polymers:  Nylon, Lexan, Teflon, Kevlar, Dacron, and many others.  Any one of these could be a starting point for the design of an original life chemistry on your planet.

Note to regular readers: I plan to work through the exercises in #blogging101 when it starts next week. I have no idea what kind of assignments will be required, so please forgive me if my blog becomes suddenly inhabited by posts about sentient protozoa or the potential of Rick Moranis to star as the romantic lead in your next non-comedy action film.

The (Thermo)Dynamics of Life in SF

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So you want to write hard science fiction.   You want to write stories that are consistent with science as we know it today, and perhaps you also want to locate your stories away from the earth—perhaps far from the earth.  If you know what that story is, and you know the science you need to write it, close your browser window and do it now.  You owe it to your readers, and you owe it to yourself.

If, however, you’re stuck in a rut, you may need to try something different to get inspired.  If, like me, you haven’t finished a story in four months (with or without a health concern to justify that situation), you may need to do some research.  In that frame of mind, let’s talk about what your off-world setting requires to support life.

PressurePhase diagram of water, derived from diagram at University of Arizona

The chemistry of life requires a liquid medium to transport chemicals within the living body.  In our neck of the woods, that means water[1].  The need for liquid water, however, puts a hard limit on the locations where water-based life could develop[2].

At any pressure lower than 6.117 millibars (the triple point of water), liquid water can’t exist.  Instead, it sublimates directly from a solid state to a gaseous one.  For comparison, one earth atmosphere is 1013 millibars.  Mars, with its surface pressure of 6.36 millibars, has just barely enough atmosphere to sustain liquid water.  The tiny Jovian moon Europa can sustain liquid water because its icy crust holds things down. Most small planets, however, especially small rocky ones, cannot support liquid water, and you’ll have to work hard to justify the presence of living organisms there.

What this means for world building is that you probably need a world with either underground seas or a mass large enough to keep your atmospheric pressure up above the triple point of water.  Size isn’t the only factor—Venus, which is smaller than Earth, has a surface pressure 92 times ours—but it’s something to consider.

ThermometerTemperature

A related question is the temperature range required for life.  Assuming the need for liquid water, biological processes need a local (internal) temperature between 0°C and 100°C at a “typical” earth atmospheric pressure[3]. Traditionally, this is interpreted to mean that your planet needs to be in the “Goldilocks” Habitability Zone, neither too hot nor too cold.  Earth is in this zone, mostly because it’s the right distance from our sun, but there are other factors, including geological heating or atmospheric collection and reflection of heat, which can modify this range.

If you’re designing a brand new world for your SF story, you probably want to give it goldilocks habitability.  If the star is red or orange, your planet will be close to its sun, and may even be tidally locked.  If you have a blue-white supergiant, the planet will be farther away, and the sun may perhaps appear smaller.  If other factors affect your world’s temperature, like insulation from thick clouds or tidal heating from the gas giant it happens to be orbiting, these factors will affect the descriptions in your story, and you’d best think them through in advance.  There is a lot of room for creativity here, but it’s a lot of work, too.

Energy

NASA-false-color-sun-image

Pressure and temperature, however, are really just expressions of a bigger need for all living things, and that is energy. Life requires energy to overcome the limits imposed by the second law of thermodynamics, which states that entropy (disorder) in a system will always increase.  Living things are massively more ordered than the universe at large, so we can only survive by creating disorder somewhere else.  Generally this implies a transfer of energy from a state in which it is concentrated to one where it is dispersed.

Nearly all of the energy available to living things on earth comes from stars, and I don’t simply mean solar energy.  Coal, gas, and oil come from the bodies of plants and animals, which themselves can trace their source of energy back to the sun.  Wind energy comes from the sun, and even geothermal energy comes from the decay of radioactive isotopes forged in the core of a long-past supernova.  The only energy source I can think of that isn’t indirectly solar is tidal energy, and tides get their energy from the same force of gravity that drives fusion in our sun.

When writing SF about life on other planets, it may be useful to ask where the energy comes from, and how it travels through your world to enable the processes of life.  It isn’t enough to have a static, warm world for life to exist; we need a dynamic one with an external source of energy that life can tap to survive.  This may sound hard, but we’re talking about hard SF here, and I think the most interesting story ideas can be born when a creative mind tries to wrap itself around a difficult issue.

[1] There may be life based on liquids other than water, but its chemistry would be far different from ours.  As a polar molecule, water readily dissolves ions that non-polar solvents like liquid methane or nitrogen could not.
[2] Yes, there are bacteria at the South Pole, where the temperature peaks around -17°C. Even if these bacteria are biologically active (and the American Society for Microbiology asserts that they can’t be), these bacteria were imports from warmer climes.
[3] At higher pressures, water stays liquid longer, so a hot super-earth might conceivably have liquid oceans. Unfortunately, the energy that makes it hotter might also cause water vapor to escape, leading to a water-deprived atmosphere like the one on Venus.
Photo credits:  Triple point diagram derived from a lecture at the University of Arizona chemistry department.  Thermometer by User:Gringer [Public domain], via Wikimedia Commons. False-color image of the sun from NASA via Wikimedia Commons.

KSP: It really IS rocket science

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True confession: I am easily distracted by strategy games on my computer. I have owned every version of Civilization since the original, and every Sim-* game since the original SimCity, other than the most recent one–and even that may change, now that Maxis has eliminated the “always online” requirement. I spend all day worrying about how my actions will affect other people; I don’t need a social game to compound that requirement.

This year, however, I started playing Kerbal Space Program (KSP), and was surprised to discover (like Randall Munroe) that I’m gaining an intuitive understanding of orbital mechanics, which I used to find counterintuitive. The other thing I find myself realizing is just how big the universe really is. That is to say, the magnitude of space is beginning to sink in for me. But to really understand this, we need to start closer to home, with a simple airline flight.

airline-viewYour commercial flight is perhaps 10 thousand feet in the air, perhaps less, and since you finished your novel during the layover in Detroit, you look out your window at the view. “Wow, you think, those houses are so small. I’m a long way up in the air.” But you aren’t even two miles above the ground.

I don’t mean to belittle that altitude. I’m sufficiently acrophobic that the thought of falling a few dozen feet is angst-producing for me. Compared to space travel, though, this is really nothing. Astronauts in the International Space Station, for example, habitually orbit at an altitude of 230 miles above the surface of the earth.

low kerbin orbitFor Kerbals in KSP, the numbers are a bit different, but the effect is similar. This picture shows an orbital altitude of 80,000 meters, which is roughly equivalent to low earth orbit (LEO) for kerbonauts, whose atmosphere is only a third as deep as ours. (From this point on, I’ll be using screenshots from KSP to illustrate this article, but I’ll try to use numbers from our solar system. I think the relative scales are still valid.)

Low earth orbit is a long way up, but compared to the earth, it isn’t a terribly big distance.  In fact, you would travel roughly 230 miles if you drove from Buffalo, NY to the state capital in Albany.  Compared to the size of the earth itself, LEO is practically touching the surface. Despite this, no human has gone higher than Low Earth Orbit since the Apollo program of the 1970s put men on the moon.

Since I grew up with the lunar landings as historical fact, I was never really impressed by them.  Having played with KSP, though, I now realize just how stupendously far away the earth’s moon really is.  At an altitude of more than 200,000 miles, the moon is three orders of magnitude higher than LEO.

moon visibleBy comparison, the distance around the world is only about 25,000 miles at the equator. To make his small step for man, Neil Armstrong travelled a distance equal to a trip around the world–more than nine times over.

This distance is so large, I didn’t really comprehend it until I took a look at the KSP-scale distance to the Mun, shown at left. In order to see it on my screen, I had to scroll back so far that the orbit of my spaceship (shown in blue) basically merged with the edge of the planet it was orbiting. And the ratio of those two distances is actually less than the real difference between the Moon’s orbit and LEO.

This immensity of scale is just the beginning, though. The planet Venus, our nearest neighbor, is never closer than about 23 million miles from us. That is roughly 100 times the distance from the earth to the moon. Once again, the scale is so tremendous that to visualize a trip from the earth to another planet, we have to zoom back so far that lunar distances disappear in the roundoff error of my first-order-approximate envelope calculations here.eve visible

Beyond our sun, the orders of magnitude just keep growing. The nearest neighbor to the Sun, Alpha Centauri, is 25 trillion miles away. This number, roughly 100,000 times the closest distance between Earth and Venus, is so large that we don’t normally talk about it in miles. Instead, the preferred unit is light years, with each light year representing the distance that light can travel in a year, or 5.8 trillion miles. At that scale, Alpha Centauri is a little over 4 light years away.

If you aren’t mind-boggled yet, consider this: the Milky Way galaxy is 100,000 light years across, and the next nearest galaxy, Andromeda, is 2.5 million light years away. There are other, more distant galaxies in our local cluster, and other galaxy clusters still further away. The local Virgo supercluster, containing our galactic cluster and its nearest neighbors, is bigger in light years than the earth’s orbit is in miles, or roughly the distance to the moon in feet.

Clearly, we have a long way to go if we want to explore the universe.

Entanglement

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“…the fact of quantum entanglement is this: If one logically inexplicable thing is known to exist, then this permits the existence of all logically inexplicable things.”

– Brian McGreevy, Hemlock Grove

Imagine a subatomic collision that produces two electrons. Due to conservation of spin, we know that one of the electrons has “up” spin, and the other has “down” spin — but we don’t know which is which. Now isolate the two electrons from interaction with other particles and separate them by an arbitrary distance. At this point you have two electrons, each in a superposition of states. Because we don’t know the spin of either electron, they both behave as if they could be have either one.

But here’s the fun part:  when you measure the spin of one particle, the waveform collapses, and it no longer behaves as if it could have the other spin.  Furthermore, at the same instant, the other particle’s waveform collapses as well. This is an example of the quantum phenomenon known as entanglement.

Since the knowledge transfer implied by this waveform change seems to occur faster than the speed of light, we can theoretically use it to implement all kinds of useful SF devices, especially the ansible. Time being what it is, however, anything that happens faster than the speed of light could lead to all manner of confusion in time-ordering of events, and smart people say it can’t be done.

Made you look!This has led me to a more interesting series of thoughts about the nature of time. Specifically, what if the future is not as a known (or unknown) series of events, but is instead a quantum superposition of all possible states? When we experience something, it collapses the waveform associated with that event, and it becomes fixed — but so does the waveform of everything connected to that event, which affects other quantum states, and so forth. We as sentient beings experience these transitions as a forward progression in time, and our interaction with these transitions as free will.

In my latest short story, “Entanglement,” I combine these two ideas into a hard-SF justification for prophecy. If the Prophet is himself somehow entangled with events in the future, then his awareness of those events “measures” the local waveform, thereby forcing the waveform associated with the future event to collapse. In a way, it is his very knowledge of the future that causes the future to occur.

This same theory, extended backward in time, may lead to a situation where the past becomes equally nonexistent whenever it loses its causal connection to the present. Those who fail to remember history shall doom it to no longer exist. But that’s a story for another day.