Sciency Words: Stochastic

June 23, 2017

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


At first glance, stochastic appears to have a pretty easy definition. Basically, it means random. A stochastic event can be defined, quite simply, as a random event. So why do scientists need this weird term? Why can’t they just say random if they mean random?

I’ve seen this word now in a surprisingly wide range of scientific fields, most recently in relation to the population dynamics of endangered species and then in relation to the magnetic field of Jupiter. The thing is that in actual usage, stochastic and random aren’t quite synonyms. A better definition for stochastic might be “seemingly random.”

The word originates from a Greek word meaning “to aim at” or “to shoot at.” So it’s an archery term, but the Greeks also used it to mean “to guess at.” I like this linguistic metaphor because a guess really is like aiming for the truth; whether or not you hit the mark is another matter.

Anyway, the word seems to have migrated from Greek to German to English, and in its modern scientific sense it refers to something that might be predictable in theory but appears to be random in practice. As an example, you may have heard that the flapping of a butterfly’s wings could set in motion a chain of events ultimately leading to a devastating hurricane.

In theory, these butterfly-initiated hurricanes could be predicted, if only we knew the exact locations and flapping behaviors of every single butterfly on Earth (along with a million and one other factors). But in practice, since we can’t gather all the necessary data, we can only make educated guesses about when and where the next hurricane will hit.

In other words, hurricanes are stochastic events. They seem random, even though they’re not.

What’s the Minimum Viable Population of a Space Colony?

June 21, 2017

Let’s say we’ve found a human-friendly planet orbiting another star, and we’ve decided to go colonize it. How many people should we send? In terms of maintaining a healthy human gene pool, what’s the minimum viable population for a distant, isolated space colony?

If you’re anything like me, you’ve spent many a sleepless night pondering that question.

I sincerely doubt anyone can provide us with a firm, specific number. However, there is a sort of generalized rule of thumb in the field of conservation biology called the 50/500 rule.

Originally proposed in 1980 by geneticist Ian Franklin and biologist Michael Soule, the 50/500 rule tells us:

  • Populations below 50 are under near-term threat of extinction due to inbreeding.
  • Populations below 500 are under long-term threat of extinction because the gene pool is too small to adapt to environmental changes.

Except the 50/500 rule is not a hard scientific law. It’s just a rule of thumb, and it has many, many detractors.

Even Michael Soule, one of the co-creators of the rule, seems to have gotten pretty frustrated by the way people took the rule literally. Here’s an interesting and, I think, revealing article about some endangered parrots. A team of conservationists contacted Soule, asking if they should even bother trying to save these parrots, because there were only 48 left.

There also an argument to be made that the numbers 50 and 500 are too low and that a 100/1000 rule would be more appropriate. And of course, can we really apply this rule to all species equally when some species reproduce more rapidly than others or face different kinds of environmental challenges, etc, etc….

Still, if we’re trying to imagine a colony of humans on some distant world, a colony struggling for short-terma and/or long-term survival, I think the 50/500 rule at least gives us a good place to start.

Sneezing in Space

March 15, 2017

So in case you were wondering: yes, astronauts do sometimes sneeze in their spacesuits. And no, there’s nothing they can do about it when it happens. The sneeze just splatters on the helmet’s faceplate.

I believe I first read about this in one of those Time Magazine specials I reviewed last year (click here or here).

The thing I really want to know is how the force of the sneeze affects the astronaut’s motion, especially when the astronaut is not wearing a helmet. For example, what happens when an astronaut is floating freely aboard the I.S.S. or some other spacecraft and suddenly sneezes?

I’d imagine the force of the sneeze could have some amusing propulsive effects in microgravity.

Sciency Words: Ecotype

December 30, 2016

Sciency Words BIO copy

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


Let’s say you discover two groups of antelope. Both groups are the same species, but one group lives on the east side of a mountain range and the other group lives on the west side.

Again, these antelope are all the same species of antelope. But because of a geographic barrier, the two groups rarely if ever intermix or interbreed. As a result, one group has developed thicker wool than the other, or they have slightly different antler shapes, or there’s some other distinctive characteristic that one group has and the other doesn’t.

When you find distinctly different groups within the same species, the groups are called ecotypes. Typically, this sort of differentiation occurs within a species because ecotypes are living in separate ecological habitats.

I first encountered this term in a recent article in Scientific American. As a science terminology enthusiast, I find this to be an interesting kink in the ongoing debate over how to define the word “species”—but the article I read was about something even more interesting than that.

Orca Ecotypes

If we ever learn to communicate with orcas (killer whales), we should tell them about Shakespeare.


Orca ecotypes don’t mix, even though there’s nothing stopping them. They’re genetically compatible. Their territories overlap. They encounter each other in the open ocean all the time, but apparently they don’t like to intermingle due to what Scientific America calls “cultural differences.”

We should be careful about anthropomorphizing animal behaviors. When Scientific American says orcas have “cultural differences,” they mean they have different hunting and feeding practices. And also different clicking/whistling patterns for communication.

Actually, that does sound a little bit like orcas have human-like languages, and maybe even a primitive version of human-like culture. And those linguistic and cultural barriers are enough to keep them apart. We really should tell them about Shakespeare. They’d probably understand a lot of Shakespeare’s themes.

P.S.: You may have missed it, but I was trying to make a West Side Story reference with that thing about antelope.


Sciency Words: Zoosemiotics

November 4, 2016

Sciency Words MATH

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


Sometimes with these Sciency Words posts, I feel like I’ve bitten off more than I can chew. This is one of those times.

Semiotics is a field of study related to linguistics, but more focused on the creation of signs and symbols and how these signs and symbols can be used to communicate meaning. Zoosemiotics is the study of how animals do that.

Think of birdsong or whale-song, or the dance of bees, or ants laying down scent trails, or dogs marking their territory, or squid rapidly changing colors, or all the crazy displays animals put on to attract mates. Or think of the way pets very pointedly stare at you while you’re eating.

There are three basic types of communication that zoosemioticians study:

  • Intraspecies zoosemiotics: communication between animals of the same species.
  • Interspecies zoosemiotics: communication between animals of different species.
  • Anthropological zoosemiotics: communication between animals and humans.

In each case, we have an animal engaging in some sort of behavior that symbolically expresses meaning. On the other side of the equation, we have another animal (or animals) trying to interpret that behavior. If the behavior is interpreted correctly, we have communication!

And when animals communicate frequently, relationships can develop. A sort of culture might start to emerge. Animals may even form a kind of social order. Studying the culture and social orders of animal groups is also part of zoosemiotics’ domain, and this is where I think things get tricky.

It’s a little too easy to anthropomorphize animals, to assign human emotions and human motivations to their natural animal behavior. So just how human-like are animal communications? How human-like are animal “cultures” and “social orders,” according to zoosemiotics? Or should we rather ask how animal-like are humans?

This starts getting into a lot of heavy philosophical territory that I’m probably not qualified to talk about. I mean, I’m not a zoosemiotician. I only learned about this term a week ago, and I have a lot more research to do. For now, I’m just happy to have a new word to add to my scientific vocabulary.

P.S.: Xenosemiotics doesn’t seem to be a word yet, but it totally should be.

Sciency Words: Conan the Bacterium

October 7, 2016

Sciency Words BIO copy

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us all expand our scientific vocabularies together. Today’s term is:


Meet Deinococus radiodurans, a species of bacteria found in truly unexpected locations all over the globe. It’s said to be the toughest bacterium in the world. It’s so tough that it’s earned the nickname Conan the Bacterium.


Don’t panic. Conan the Bacterium is nonpathogenic and does not represent a threat to humans.

Some microorganisms are referred to as extremophiles, because they’ve adapted to survive in some specific extreme environment. Conan is a polyextremophile, because it has adapted to survive in a wide variety of extreme environments. Among other things, Conan can endure:

  • Highly acidic environments
  • Airless environments
  • Waterless environments
  • Extremely cold environments
  • Extremely radioactive environments

Frankly, it sounds like this little bugger is perfectly adapted for life on Mars, but according to my reading, its genome suggests that it did in fact evolve here on Earth.

Conan’s resistance to radiation is of particular interest to science. It seems that whenever radiation damages Conan’s DNA, even if the DNA is shredded into tiny bits, Conan can stitch its DNA back together again in as little as twelve hours.

Lots of organisms, including humans, have some ability to repair their own damaged DNA. Conan is just a whole lot better at it than the rest of us, and no one’s sure why.

I first learned about Conan the Bacterium in a book called All These Worlds Are Yours: The Scientific Search for Alien Life. I’ll be doing a book review early next week.

Molecular Monday: Liquid Water vs. Liquid Methane

September 5, 2016

Molecular Mondays Header

Welcome to Molecular Monday! On the first Monday of the month, we take a closer look at the atoms and molecules that make up our physical universe. Today, we’re comparing some of the properties of:


So you’re a moon or other planetary body, and you want to get some biochemical action going on. First, you need some organic substances. Titan has set a great example with the tholin haze that forms spontaneously in its atmosphere.

Next, you need a liquid to dissolve that organic material in, in the hopes that the organic material will recombine as amino acids, peptide chains, and ultimately DNA. But which liquid should you choose? Liquid water (as seen on Earth) or liquid methane (as seen on Titan)?

Pick Water!

Water (H2O) makes an excellent solvent for our purposes because it’s a polar molecule. There are two big reasons for water’s polarity.

  • First, oxygen has an extremely high electronegativity, meaning oxygen atoms like to yank electrons away from other atoms. Within a water molecule, oxygen’s electron-hogging tendencies cause it to become negatively charged, while the two hydrogen atoms become positive.
  • Second, you know how water molecules have that Mickey Mouse shape? Because of that shape, with the two hydrogen atoms bent toward each other, the positive charges accumulate on one side of the molecule and the negative charge accumulates on the other.

Thus, water is a polar molecule, and it’ll go around interacting with other polar molecules, like tholins or amino acids.

Don’t Pick Methane

Unlike water, methane (CH4) is a nonpolar molecule. Why?

  • Carbon is slightly more electronegative than hydrogen, but not by much, so the atoms in a methane molecule share electrons almost equally. This minimizes the electric charges that might build up inside the molecule.
  • Methane molecules are symmetrical, with the carbon atom in the center and the four hydrogens evenly spaced around in, like the four corners of an equilateral pyramid.

Sp05 Methane vs Water

Any electrical charges in a methane molecule balance out, due to the molecule’s symmetry. And those charges are fairly weak anyway, due to the similar electronegativities of carbon and hydrogen.

I won’t be so bold as to say life can’t develop in a liquid methane environment, but the idea does seem a bit farfetched in light of the chemistry. Polar molecules like tholins just aren’t likely to dissolve in a methane lake, like the lakes found on Titan.

On the other hand, the universe keeps surprising us, and the giant lake monster I recently met on Titan might dispute my assessment of Titan’s biochemical potential.

P.S.: Titan’s lakes also contain liquid ethane, but that doesn’t really change anything. Ethane is also nonpolar.