Sunday, December 18, 2011

Weird Worlds: Kepler 22b

It's what all the cool kids are (still) talking about, so why not a post on it? In the glut of Kepler mission transiting planets, a new planet has risen to the fore as the possibly most Earthlike extrasolar planet. Huzzah! (And in a few months yet another new planet will take its place. Just watch).

Credit: NASA/Ames/JPL-Caltech

What we know

Kepler 22 is a star very similar to our sun. It is slightly smaller (0.98 times the radius of the sun) and slightly smaller (0.97 times the mass of the sun). It is 587.1 light years away, so it's not something we're going to be visiting soon.

So far, it only has one known planet, dubbed -- as these things go -- Kepler 22b. This planet is smack bang in the habitable zone ...on the inner edge, so OK, maybe not that smack bang... BUT. The part people are getting exciting about is that it's the smallest planet we've found in the habitable zone thus far.

How small? 2.38 Earth radii. For comparison, Neptune, the next biggest solar planet after Earth, is 3.88 times Earth's radius. That puts Kepler 22b just on the smaller side of halfway between Earth and Neptune. In terms of size.

What we don't know is how massive it is. The way the Kepler satellite detects exoplanets is by looking at stars and measuring how much dimmer they get when (if) a planet passes between the star and us. By knowing how much light the star gives out usually, and how far away it is, it's possible to work out how large the planet is. (And, actually, even if you don't know how far away the star is, you could still work out how big the planet has to be as a fraction of the size of the star.)

We know how long its year is, basically by measuring how often it passes in front of the star. Yeah. It's that simple (particularly since there seems to be just one planet in this system at the moment). So Kepler 22b's year is 290 days long, not drastically different to Earth's. That and its position in the habitable zone have lead people to suppose that maybe it's not so different to Earth.

Based on how far it is from its star etc, the average surface temperature would be about -11º Celsius if it had no atmosphere. However, if it had an atmosphere like Earth's average temperature would be about 22º C. Perhaps a slightly less insulating atmosphere would be in order, however, since Earth's mean surface temperature is actually 14º C. (Because we have to take global lows and highs into account, you see, and average over the whole planet, never mind that 22º is just about room temperature.)

Harping on what we don't know

It's that mass. And the fact that we don't have a planet of that size in our solar system. It's in the transitional zone, as I said, between rocky terrestrial planet and mini gas giant. If it's rocky, it's likely that the gravity will be stronger than Earth's, thanks to it's larger size. In fact, if it's the same density as Earth, the surface gravity will be about 2.4 times Earth. Which isn't long-term viable. At Neptune's density, we get a ball of gas with surface gravity 0.72 times Earth. A ball of ice would result in gravity 4.3 times Earth. The least dense terrestrial planet in our solar system is Mars and at Mars' density, Kepler 22b would have gravity 1.7 Earth's.

So there's quite a spectrum of possibilities there. We really don't know enough to make any definitive judgements at this stage. That doesn't make it less exciting, of course, and it's true that there might be oceans and continents there. Or it could be a small dense ball with a thick gaseous atmosphere inhabited by dragons (perhaps even fire-breathing ones, if there's methane in the atmosphere and breathing fire is a viable way to catch prey). Which would also be cool. Arguably, cooler.

Saturday, December 10, 2011

Australian Women Writers Challenge

Next year, I am going to take on the Australian Women Writers Challenge. To make it particularly challenging and to tie in better with the contents of my blog, I am going to try to read only science fictional books by female Australians.

The specifics of my challenge:

Genre challenge: Purist: one genre only

Challenge level: Miles (read 6 and review at least 3*)

* Should include at least one substantial length review

I'm excited! But also kind of glad that there are still a few weeks left in 2011 to finish the Vorkorsigan Saga which I'm in the grips of. (Only, um, 4-5 books to go...)

Book list

And here is my preliminary list of books/authors that I plan to read. The order I've listed them is more or less the order they occurred to me / were suggested to me on Twitter / I saw them on past Aurealis Awards short lists. Also, I think some of these will be difficult to acquire, so that will definitely affect my ability to get through them all.
  • Marianne de Pierres (definitely Angel Arias which is sitting on my bookshelf, quite possibly others)
  • Patty Jansen (Watchers Web / The Far Horison)
  • Kim Westwood (Courier's New Bicycle)
  • Maria Quinn (Gene Thieves)
Sara Creasy (Song of Scarabaeus)
  • Sonny Whitelaw (Rhesus Factor)
  • Claire Corbett (When We Have Wings)
  • Sue Isle (Nightsiders)
  • Maxine McArthur (Less Than Human / Time Future)
  • Michelle Marquardt (Blue Silence -- seems very hard to find though)
  • Tess Williams (Sea as Mirror)
  • Sally Rogers-Davidson (Spare Parts)
 I've put a link along the top bar thingy under the banner to a page where I'll be collating reviews and keeping track of the books I've read.

Wednesday, December 7, 2011

Measuring distances: the furthest away objects

[First up, apologies for the unscheduled hiatus. Being sick and moving house (mercifully not simultaneously) sort of quashed any blogging plans I may have had. OK, so I don't mean so much quashed as put out of my mind entirely, but whatever.

Also, thanks to changing life routines, I think I'll be changing my update schedule from Wednesday nights to weekends. For the time being it seems more manageable.]

This week I thought I'd talk about something a little bit outside the realms of foreseeable future SF: extragalactic distances. I say outside in the sense that there is currently no plausible way to travel to neighbouring galaxies, let alone galaxies at the edges of the observable universe.

How far is far?

The thing to understand here is that the universe is really big. Like, amazingly, mind-blowingly large. Douglas Adams said it well:
Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.
Light travels 300 000 km in one second (in a vacuum). It takes about eight minutes for light to travel from the sun to Earth. About five and a half hours from light to travel from the sun to Pluto. It takes a hundred thousand years for light to travel from one edge of our galaxy to the far edge (along the disc). By this stage, I'm sure you've heard the term light year. It's the distance that light can travel in one year and is about 9 460 000 000 000 kilometers (about 1013 km or ten trillion kilometres). The nearest galaxy is two and a half million light years away. See how all these distances stack up?

Most astronomers don't actually measure or think about distances in light years. They're somewhat useful for conceptualising things, but parsecs (abbreviated to pc) are more common. One parsec is 3.26 light years. That puts the nearest galaxy, Andromeda almost 800 kpc away (kpc is kiloparsec where the kilo indicates a factor of 1000). Mostly galaxy distances are measured in megaparsecs (Mpc) where one megaparsec is a million parsecs.

Even larger distances are measured using a scale called redshift. The universe is expanding. When light leaves a distant galaxy and travels towards us, it takes time. Possibly millions or billions of years, depending on just how distant that galaxy is. In all that time while it's travelling, the universe continues expanding. The expansion stretches out the light so by the time it gets to us, it has a longer wavelength. Longer wavelength means redder (on the visible spectrum, although in reality this light could have started at any wavelength, depending on what emitted it, and could finish up stretched out all the way into the radio region). Hence the term "redshift".

Doing the Measuring

I touched upon spectroscopy when I talked about the Doppler effect in this astronavigation post. Basically, you look for some known lines (often hydrogen lines) and see how far they've shifted towards the red end of the spectrum.

So we should just be able to use this to measure distances, since we know how fast the universe is expanding, right? Not quite. In the post I linked above, I talked about Doppler shift. This is different to redshift but it can look very similar. Far away galaxies can be moving relative to their neighbours (galaxies in a cluster orbiting a central galaxy, for example). These local motions are called peculiar velocites. This means that you could work out spectroscopic redshifts for galaxies in a cluster, which are all around the same distance from us, but get different results because of their peculiar velocities.

Instead we have to use a combination of different methods, two of which I'll talk about now. The same principle underlies both. Basicaly, in the 70s and 80s, it was discovered that there are a few "scaling relations" which galaxies obey. For example the Tully-Fisher relation relates a spiral galaxy's luminosity (how much light it gives out in total) and the rotational velocity of it's stars (how quickly they orbit the centre).

Spiral Galaxy M101
A spiral galaxy. Although, for a Tully-Fisher measurement, you'd
want it to be side-on, not face-on. But face-on looks prettier.
We can measure the rotational velocity of the stars in a spiral galaxy using the Doppler effect (even though the galaxy is moving away, the stars on one side will be moving towards us and on the other side away from us -- the difference between the two sides can be used to work out the rotational velocity). Once we know that, we get a prediction for the luminosity of the galaxy. However, the galaxy is far away and looks dim, much like a light in a high-ceilinged hall that isn't too bright too look at although it would hurt your eyes if you were up close. Exactly how dim a galaxy looks depends exactly on how far away it is. So if we know how bright it should be, we can compare with how bright it appears and work out how far away it is. Huzzah.

There is a similar, albeit slightly more complicated, relationship for elliptical galaxies called the Fundamental Plane.

Both the Tully-Fisher relation and the Fundamental Plane are constantly being improved upon as we build better telescopes that give more precise measurements and also as we understand the underlying physics governing them better. (At the moment, we're not super sure why they exist.) However, we're still able to use them to measure things like Hubble's constant. Who knows, maybe there are super advanced aliens out there who can set up extragalactic wormholes and need to know how far away to place them.

Probably not, though. I did say this post was outside the realm of plausibility.

Wednesday, November 16, 2011

Strong Characters (Audience participation post!)

Although not strictly science- or space-based, this post has been kicking around my mind for a while. I decided that today (when my sinuses are trying to kill me and I don't quite have the energy to talk about exploding meteorites in Terra Nova), would be a good time to write it. And fair warning, I am going to Use Examples from Harry Potter, because JK Rowling not only provided good examples, but most of the world already knows what happened in the end so I don't feel bad about possible spoilers. Sorry to those three people in the developed world who haven't read Harry Potter. Well done.

Actually, it's not so much the blog post that's been rattling in my head so much as the question: what makes a strong character "strong"?

Several people have written all over the internet that "strong", when we're talking about characterisation, does not automatically imply physical strength (particularly relevant when we're talking about strong female characters, but that's not quite the point I want to raise today). I want to talk about emotional strength and skip the argument as to whether that's equal to physical strength.

Strong characters in Harry Potter.
It is easy to identify characters that lie at extreme ends of the emotional strength spectrum. The hero/ine who sacrifices a lot to save her friends/village/the world is almost certainly going to be a strong character because (assuming it's a good story) they are going to have various obstacles to overcome, both physical and emotional, perhaps stemming from their flaws. Antagonists in some ways have less stringent requirements. Voldemort won't allow anyone to stand in his way (making him strong, if Evil), but Wormtail spends his time attaching himself to strong people around him (first James and Sirius, later Voldemort). And I'm sure he's described as "snivelling" at least once; a clear indication of a weak character.

There are other situations when the distinctions between weak and strong are less cut and dried. There's the character who does the right thing for the wrong reasons or the character who does the wrong thing for the right reasons. There's Snape who did very difficult things for love and, ultimately fought on the side of Good. He didn't do it for noble reasons (in my opinion) like the lead trio, but he still had to be very strong to prevent Voldemort from catching on.

What about the character who is so strongly affected by something (a death, a breakup) that they have difficulty functioning? Are they stronger or weaker than the character who represses their emotions or (for whatever reason) doesn't feel anything? It seems clear to me that the character who is terribly saddened but still carries on through their hurt is emotionally strong. (Although, if you want to argue in the comments, knock yourselves out.) I ask you, which is "stronger": character A, who can't come to terms with the terminal illness of character C and avoids them because they hurt too much to see them suffer, or character B who isn't as emotionally affected but stays by character C out of a sense of duty? It's a grey area, although I'm sure character C would appreciate B more, especially from a practical point of view. (And character D who is heart-broken but stays around anyway would be the clear winner, but they aren't always an option.)

On the other hand, the character who isn't scared can't be brave.

What are your thoughts on the matter? What makes a strong character for you? What are some good examples of weak and strong characters in fiction?

Thursday, November 10, 2011

Future Tech in Fiction

I thought this week I'd talk about some incorrect technology predictions in fiction. My aim is more to highlight ways in which authors can be wrong rather than mock them. I mean, you can't expect to be right all the time, but I think it's interesting to note exactly how they were wrong and why (from a somewhat philosophical point of view).

So I've chosen three books, all old (60ish years) and all containing some piece of technology which didn't quite work out as foreseen.

Second Foundation by Isaac Asimov

Second Foundation the final book in the original Foundation trilogy was first published in 1953 (although it was serialised in Astounding Magazine -- now known as Analog -- prior to that between 1948 and 1950). For those unfamiliar with the Foundation series, it is set in a post-galactic empire world as said galactic empire is crumbling. So a good thousand years or so in the future.

I remember quite clearly a passage where one of the characters, a teenage girl called Arkady, is writing an essay for school. These days, obviously, she would be typing it on a computer. In Second Foundation she was dictating to a typewriter that printed in nice calligraphy on pink (I think) scented paper. I don't think it was called a typewriter (but I don't have the book nearby to check) but it seems an apt label since I think when she mispronounced something she had to redo the page. Definitely no screen.

Asimov himself has said that he completely failed to predict a few major things, one of which was the miniaturisation of computers (up until the microchip was invented in the real world his future tech computers still had vacuum tubes). Does that make Asimov's work wrong or bad? No, it doesn't. A typewriter you can talk at is a possible evolution of writing hardware, just not the one we followed. It's not that we can't make a dictation-typewriter now, it's that we have better things, like editable text. (See, that story even pre-dated electric typewriters.)

Would Asimov's story been better if he had somehow foreseen laptops or smartphones and given his characters those instead of juiced up typewriters? I think not, for a couple of reasons:
  1. It was a fairly minor point in the story and stopping to explain a laptop to a 1950s audience would have taken several unnecessary pages and not added anything to the actual story (the point of the scene, from memory, is to build setting and to later show us how she grows throughout the story).
  2. Once you have something like a laptop, a lot of the other technology would need upgrading (no more vacuum tubes on spaceships either) which would lead to more needless explaining of concepts. It's not that there isn't a place for explaining future tech in stories -- it's what puts the "hard" in hard SF after all -- but I think you need to choose your battles in terms of what's most relevant to the story at hand.
This example reminds me of the quote by Henry Ford, who invented the car: "If I had asked customers what they wanted, they would have said a faster horse." But maybe sometimes we need a faster horse. I think that often what we really want the future to be like is more or less like now, but a bit better, faster and shinier. Unless you're dealing with dystopian SF, which Asimov assuredly was not.

Prelude to Space by Arthur C Clarke

This novel was written in 1947 but, according to Wiki, not published until 1951. It was set in the near future (relative to when it was written); the 1970s. It recounts the events leading up to the launch of the first manned mission to the moon in delightful detail. (If you're wondering, it's the British, launching from Woomera in Australia, who win this space race. Possibly unsurprising given Clarke's nationality.)

I am in no way faulting Clarke for getting the year wrong for the moon landing (and he wasn't that far off). I do think having the British achieve it was a bit optimistic on his part, but I don't have a problem with that either (and being set in Australia gets bonus points from me ;-p ). In fact I've included it here for pretty much just one flippant statement made by a character about the future of spaceflight.

At some point, one of the characters makes the remark that atomic rockets were necessary to get to the moon and that it would never have been possible with chemical rockets. The problem? Chemical rockets are exactly how we got to the moon, and just about everywhere else, at least in part. Some prototypes and a few probes have done more interesting things, but all manned missions used chemical rockets.

The problem isn't that the book had nuclear powered space flight, it was the sweeping generalisation that quickly dated it. OK, so the whole "we don't need to speculate about how we're going to get to the moon once we've been there and know how we got there" also contributed to that. Perhaps I should have said that the sweeping generalisation made me laugh when I read it.

My suggestion is not to make sweeping generalisations about future tech if you can avoid it, especially if you're writing something reasonably near-future. I think it might become less important in other sub-genres such as dystopian science fiction for example.

Step to the Stars by Lester del Rey

This one was published in 1954. Also, I don't recommend actually reading it because it is horribly racist and sexist.

(I think it's good that my formative SF-reading years were spent reading mostly Asimov, who isn't racist nor sexist*. I'm not sure what I would have made of the highly inflammatory and offensive preface to this book if I had read it at a more impressionable age. The preface, if you're curious, basically said that if We -- ie Americans, because no one else reads books in English, right? -- don't build a space station first, then They -- that is, the evil commies -- will kill Us all with space lasers. I'll admit I don't remember if space lasers were actually mentioned, but that was the gist. It might have been nukes, now that I come to think of it. Anyway...)

The premise is that in order to expand into space, the best approach is to build a space station and then launch ships to the moon and Mars and wherever from there. So the US government decides to build one in secret. Egads! There is no way that would have stayed secret as long as it did in the book. Sure, you might be able to put a few high-orbit military satellites up without your enemies noticing, but all the bits required for a space station? I think not. Not to mention that the actual space station would be reasonably noticeable (assuming you were looking for your enemies to do something, which given the context of the book, they would have been). But I am ranting about the wrong thing. (Also, gah! They recruited random engineers and mechanics to build the thing in space. What?! AND these people all kept quiet about the secret space station? OK, OK, moving on.)

I thought the descriptions of living in space were reasonable, particularly given that they were written before anyone had ever actually been in space. What I wanted to draw attention to was how del Rey portrayed rocket flight. The Loyal Citizens building the space station used small rocket-powered taxi ships (I hesitate to call them shuttles because of other connotations) to get around between the construction site and whatnot. (See how large this enterprise was? How could they think it would stay secret?) The way it was described, each little ship had just one largish rocket attached to it, so to break or turn, they had to point the rocket in another direction and fire. I believe gyroscopes were used to change orientation.

It's not so much that he got the physics wrong here (although rockets as we usually think of them would be much too powerful for these purposes, that is easily overcome), but the impracticality of the set up. Surely it would save time and training money to just put smaller rockets in for manoeuvring? This is what we do in the real world, more or less (the less being that the actual rockets used are nothing like the sort used to get off the ground because there's no gravity to overcome and no air-resistance either).

It's not just accurate science which is necessary -- del Rey was as accurate as he could be, from memory -- but practicality. Yes, you can use a gyroscope to flip your ship around and change direction, but think of how disorienting that would be for the pilot with all the spinning stars.

* I mean, Asimov's books aren't overfilled with female characters or anything, and they are in many ways a product of their times, but he had some competent women who were more than secretaries or love interests to the male characters. For example Susan Calvin in some of the robot stories, Arkady who was mentioned above, and several secondary characters whose names escape me. And he wasn't racist.

Wednesday, November 2, 2011

Weird Worlds: Kepler 14b

This post follows the same theme as last week's: planets in binary star systems. Last week's planet, Kepler 16(AB)b, orbited two stars which closely spun around each other. This week's planet, Kepler 14b, orbits one star, which in turn orbits another star at a further distance. This paper, by Buchhave et al (2011), is the main source of my data on Kepler 14b.

Kepler 14b is unlikely to have any sort of solid surface.
However, the two stars could look something like this. Maybe.
Honestly, I think this might be a re-purposed Io illustration
but NASA did use it on a Kepler 14b page, so who am I to argue?
Image credit: Susan Stanley for NASA Kepler Mission Education
and Public Outreach.
It turns out that unlike originally thought from the Kepler satellite data, the star Kepler 14 is not a star, but is two stars. Buchhave et al (2011) discovered this when they went and looked at it with an Earth-based optical telescope. The two stars are so close together in the sky as seen from Earth that it took fancy adaptive optics to be able to resolve them. Resolving, by the way, means being able to distinguish that there are two separate sources of light, not a single blob. The stars were too close together to be able to separate out their spectra (because this uses a different instrument than the one that images them normally), so a few assumptions had to be made, but none that should strongly affect the planet.

Some facts

The two stars that make up Kepler 14 are designated A and B with A being the one the planet orbits, but the nomenclature is a little fuzzy because the binary nature of the system was discovered later. Going on the basis that the system is 980 parsecs away (3200 light years), then the two stars are separated by 280 AU (remember, 1 AU is the distance from Earth to sun and Pluto is about 40 AU from the sun). Both stars are bigger, hotter and brighter than the sun. The sun is a G type star and the Kepler 14 stars are F types, one spectroscopic class hotter/bluer. They are 1.51 and 1.39 times the mass of the sun and orbit each other once every 2800 years.

The planet, Kepler 14b -- I am tempted at this point to make up a name for it. I dub it Keforb -- is 8.4 times the mass of Jupiter. This makes it a fairly large gas giant and definitely not habitable by human standards. Could one of it's moons be habitable? Well, let's keep looking at the planetary parameters.

The orbital period, the length of one Keforbian year, is 6.79 Earth days. That's pretty quick. If you've been playing along at home, you might remember that planets orbit faster the closer in to their star they are. Keforb is only about 0.08 AU from it's primary sun. (Mercury is about 0.4 AU from the sun.) I don't need to do any calculations to know that this planet is going to be way too hot for life, even if it had a suitably-sized moon. It's the sort of planet that's known as a hot Jupiter.

I found this pretty awesome NASA page which shows everything you need to know about Keforb (except for my awesome name) including, if you click on the buttons down the bottom, where Kepler 14's habitable zone is and the orbits of solar system planets for comparison.

So the habitable zone for this system is out past Mars's orbit, in the range of 2.17–3.56 AU, roughly where the asteroid belt is in our solar system.

Similar configurations?

OK, so there's no hope for life on the one known planet in the Kepler 14 system, but what about other possible planetary systems of similar configuration. I mentioned Tatooine last week as being similar to the planet in the Kepler 16 system. The Kepler 14 system is different because the planet orbits only one star, not both of them.

A system of this sort that pops up in fiction every now and again is a planet orbiting a red dwarf star which is in turn orbiting a larger, brighter star. I'm pretty sure I've read about this sort of thing more than once but the series that springs to mind first is the Second Sons Trilogy by Jennifer Fallon. Partly this is because it's one of my favourite series, so I may be biased. In the first book, Lion of Senet, we are introduced to a world with two suns: a small red sun and a more distant yellow sun. The world orbits the red sun and the red sun orbits the second yellow sun. The residents experience two different types of sun sets and sun rises and their "nights" are when only the red sun are up in the sky. They also get to experience side-effects from the tidal forces of a) having two suns and b) being in a relatively close orbit with the red dwarf. This means lots of volcanoes and tidal waves (I think the first book even opens just after a volcano, but I may be wrong and I don't have it on hand to check).

It's billed as a fantasy series, and it's certainly written in a fantasy style with feudalism and political intrigue and war and things (the rest of Jennifer Fallon's books are indisputably fantasy). However, there isn't any more magic than in our world which makes me tempted to say that it's technically sort of science fiction. But without laser guns (or any sort of guns. There are swords, though). Maybe "sword and science" rather than "sword and sorcery".

Anyway, I highly recommend it, not just because of the interesting celestial mechanics, but also because it's a damn good read. The hero, Dirk, goes around applying his brain, not brawn. Also, if you go in solely for the celestial mechanics, you might be disappointed because, while good for the reasons I've mentioned above, it's not quite perfect, mostly for reasons of plot.

Sometimes, it's best not to let science stand in the way of a good story. (So long as you try and at least some of the science is sensible.)

Wednesday, October 26, 2011

Weird Worlds: Kepler 16

I have talked about the Kepler exoplanet-finding mission in the past (planet spotting, Kepler 11, KOI 730). Today I'm going to look at a planet Kepler has found in a binary star system: Kepler 16(AB)b and next week I'll talk about Kepler 14b which is also in a binary system but in a different configuration.

A binary star system is where two stars are close enough together to be in orbit around each other, instead of individually orbiting the centre of the galaxy. Instead they orbit the centre of the galaxy together, much the same way as the Earth and the moon orbit the sun together. Also sort of like on Tatooine from Star Wars.

Kepler 16b

Artist's impression of the Kepler 16 system.
Credit: NASA/JPL-Caltech/R. Hurt
Basic stats for the Kepler 16 system are somewhat unartistically presented here. I'll go over some of them below.

As far as we know, there are three bodies in the Kepler 16 system: the two stars which are designated Kepler 16A and B (and together Kepler 16(AB). As per usual convention, the more massive star will be A while the smaller will be B. The usual convention, for non-binary systems, is that the star is designated Whatever-a and planets in order of discovery then mass (so mass when several are discovered simultaneously) are designated Whatever-b, Whatever-c etc. The lower-case a for the stars is a bit redundant here, though. Masses and distances for the system are as follows:
  • Star A:
    • Mass: 0.69 solar masses
    • Size: 0.65 solar radii
    • Temperature: 4450 Kelvin (about 4180º C or 7600º F)
  • Star B:
    • Mass: 0.20 solar masses
    • Size: 0.23 solar radii
  • Stars AB together:
    • Orbital period: 41 days
    • Orbital separation: 0.224 AU (for comparison, Mercury's orbit is 0.387 AU from the sun)
  • Planet Kepler 16(AB)b:
    • Mass: 0.33 Jovian masses
    • Size: 0.75 Jovian radii
    • Orbital period: 229 days
    • Orbital radius: 0.70 AU (Venus is 0.72 AU from the sun)
It's not possible to separate out and measure the temperature of star B because it is completely overwhelmed by the light from star A. We can only make guesses based on it's spectral type which is determined from its chemical make up. Also note that the distance measurement for the planet is from the centre of mass of the two stars -- the barycentre.

For a bit of fun, let's work out how big and bright each star would be from the planet, relative to the sun. I should note that this is a gas giant planet and so any possible light would be more likely to exist on one of its moons, not the planet. The suns would appear the same size from a moon, though.

First, how big would the suns appear? (See this post for details on the calculation.) Remember for comparison that the sun (and moon) have an angular diameter of about 0.5º. So, sizes:
  • Star A as seen from planet on average: 0.49º, so about the same as the sun
    •  Range: 0.43º to 0.59º
  • Star B as seen from planet on average: 0.18º, which is about a third of the diameter of the sun
    • Range: 0.15º to 0.21º
Now, how much light would reach the planet from the two suns? Or how brightly would the stars illuminate the planet? This is a slightly more complicated calculation which you can read about here (and for comparative purposes, about 1400 Joules of energy hit each square metre of the Earth from the sun each second). Remember, also, that sometimes star B will pass behind star A, sometimes they will appear next to each other and sometimes B will be in front of A, blocking out some of A's light but contributing its own. I'm just going to calculate them separately.
  • Star A: 410 Joules per square metre per second, which is a bit less than a third of the light energy the Earth gets from the sun. It is also going to be redder light, thanks to the cooler temperature of the star.
  • Star B: assuming its temperature is about 2500 K which is within the plausible range for M type stars (star A is K type, if you're curious), I get about 5 Joules. That's 3-4% of the light from the sun hitting Earth. On the other hand, it's still a lot brighter than the full moon in Earth's sky (and significantly redder). About 1400 times brighter, in fact. And about as bright as 260 100 Watt light bulbs at a distance of 10 m. Except it would probably feel dimmer thanks to the redness.
Finally, let's suppose that there is an Earth-like moon of this gas giant planet Kepler 16b. How warm would the suns make it? The calculations are discussed in this post on the habitable zone. Since most of the warming comes from star A, I'm going to ignore star B for this calculation. The average temperature I get is about 190 K which is about -85º C or -121ºF. So a little bit too cold for life, but not too hot, which is a harder problem to solve. Maybe throw in a bit of greenhouse warming and a lot of snow gear and you have yourself a snowball planet with two suns. Not just cold, but pretty cool.

And if you want to read more, here is a nice New Scientist article about it. And, below, a video from APOD:

Friday, October 21, 2011

Bunch of links, mostly outdated

First up, square Earth anyone? Forget realism, let's just have a think about what an Earthlike planet would be like if it were a cube. Puts me in mind of the planet builders in Hitchhikers' Guide to the Galaxy. Brought to you by Discovery News.

Second, the Planetary Habitability Laboratory talks about brightnesses of the various planets in the solar system and also of exoplanets. An interesting read, particularly if you enjoyed my old How Bright is the Night? post.

Martian moons eclipse the sun in these NASA photos from the Opportunity rover:
Credit: NASA/JPL/Cornell

Enceladus pics from Cassini. Enceladus is one of Saturn's moons, most famous for it's ice geysers.

Proposed space robot to cannibalise old satellites which have previously been boosted up to "graveyard" orbits. Many mentions of zombie satellites and grave robbing associated with this one ;-p . From New Scientist.

And finally, laser driven fusion in California. From New Scientist again.

Happy weekend, gentle readers!

Wednesday, October 19, 2011

Propulsion: Not just rocket science

Spaceships: something's gotta make them go. Even if you have made up a nice way of going faster than light -- wormholes, warpdrives, hyperspace, improbability drives -- there are going to be bits when your characters have to travel more mundanely. You can't go into orbit when you're travelling faster than light. Unless you happen to be inside the event horizon of a black hole, but then you have other problems.

This post is about relatively non-relativistic (yeah, I did that on purpose, so shoot me) methods of propulsion. To be used in local space only (or if you want to throw your characters into suspended animation or trap them on a generation ship, or something).


OK, it's pretty much mandatory that I start with rockets since they are what got us into space in the first place. Specifically chemical rockets, since the term has come to be used more broadly in some circles.

Space shuttle Endeavour taking off.
Credit: NASA
The basic premise is: set things on fire explosively, direct the explosion away from where you want to go, and conservation of momentum does the rest. Why conservation of momentum? In the greater scheme of the universe, momentum must be conserved. It cannot be created spontaneously and it cannot be destroyed. It's one of those immutable laws. So, the only way to move is by exchanging momentum with something else. Say you sit on a particularly good wheeled chair. If you throw your heavy, laptop-filled bag away in front of you, the chair will move backwards a bit. Assuming you were stationary to begin with, when you threw the bag, you imparted it with momentum. (Momentum, by the way, is just the product of mass and speed, nothing too mysterious.) But momentum has to be conserved, so to compensate, you and your chair moved backwards with momentum exactly equal and in the opposite direction to that of the bag. Of course, this example isn't perfect since the wheels of the chair are also slowed down through friction, but ideally, your mass plus the chairs mass, multiplied by how quickly you moved backwards, would be equal to the mass of the bag multiplied by the speed at which you threw it.

In a frictionless environment, such as space, throwing something as small as an apple (also, congrats on smuggling an apple onto your space station) would propel you backwards noticeably. This is what most fuels do, in essence. They throw something backwards as hard as they can so that they can go forwards.

Commonly, rockets (that take off from Earth) have two tanks, one filled with liquid oxygen and one with liquid hydrogen. When combined they react very quickly and exothermically* which leads to a rapid release of energy and water. Because water is what you get when you put a lot of hydrogen near a lot of oxygen. (Really, putting a lot of hydrogen near a little bit of oxygen also ends explosively.) And water is what you get when you burn hydrogen (and if you're wondering "burning" something is just a colloquial way of saying "oxidise rapidly" or "react with oxygen"). The good news is that launching rockets doesn't have a large carbon footprint (because no carbon is involved in the actual launch process); building them is another matter.

Back to the point, oxygen/hydrogen are used as propellants because they give off the most energy of any practical combination of chemicals. Somewhere, probably on the internet, I once came across a table of effectiveness of different fuels. I would love to link to it now, but that was several years ago and I could not find it again. The closest I got was this table in Wiki, which is more a table of different propulsion methods.

* Exothermic reactions are reactions that release energy. Conversely, endothermic reactions consume energy.

Ion drives

Ion drives are a term that gets bandied around in both science fiction and "future of science" type discussions every now and then. There are actually a few different ways to build an ion drive (see aforementioned table in Wiki for details). The basic premise is that instead of using a chemical reaction to push something out the back of the spacecraft, you use electric fields to push ions (atoms with either a positive or negative charge; positive one are being pushed out, usually) away from the spacecraft. (Which you might have ionised with a laser or similar.)

The main downside is that the accelerations generated are fairly low, so it would take a long time to get anywhere. Unlike chemical rockets, however, ion drives would generally take a lot longer to run out of fuel. It might also be possible to scoop up stray atoms from space, ionise those and use them as propellant (this part, completely untested right now; ion drives in principle have been constructed though). So, although you start off slowly, if you keep accelerating constantly over a long period of time, the ion drive could leave you with considerable speed by the time you arrive. On the other hand, now that I think about it, they probably wouldn't work for decelerating suddenly, nor for manoeuvring.

Really, ion drives are just another way of throwing things backwards to make you go faster.

To read more, go look at the NASA Deep Space 1 page, a mission powered by an ion drive.

Solar sails

Solar sails, on the other hand, work on a slightly different principle. Instead of bringing fuel along on the trip and throwing it out, a solar sail works, well, similarly to a sail on a boat. You throw your fuel at it to make it go forwards.

Just as wind pushes boats along by the sails, so does light push solar sails along.

Light can't push things! I hear you exclaim. (Or is that the sleep deprivation talking?) Actually, yes it can. Photons, particles of light, have a momentum associated with them. It is calculated a little differently to momentum for objects/particles which do have mass; instead of mass times velocity it's Planck's constant divided by wavelength (exactly why is a bit complicated. Quantum is involved).

So a solar sail works by "collecting" the momentum of the light that hits it. The source of that light could be the sun or it could be a giant laser. The advantage of the sun is that it's free, but the disadvantage is that sunlight is a little dilute from an Earth's distance away so the acceleration would be fairly slow. A laser would start off more concentrated and impart a lot more initial acceleration, but once the sail was out of range you'd be left with a giant laser and nothing to point it at. (I suppose some people wouldn't see this as a disadvantage.) Perhaps some combination of the two would be best, but in the real world, we're not up to that sort of testing.

Below is a picture (CGI sadly. I so wanted this to be a photo taken from the ISS or something) of NASA's NanoSail-D which they recently deployed. From memory, there was a bit of trouble getting the thing to unfurl properly (definitely can't launch with those sails fully extended) and then after a few days it magically worked. Here is more info from NASA.

NanoSail-D. Pic from NASA via APoD.

So there you have it, a few ways for your characters to travel mundanely, mainly within a system.

Wednesday, October 12, 2011


Rimmer from Red Dwarf. He went mad in his
astronavigation exam and wrote "I am a fish"
four hundred times. It's not actually that hard.
If you want to include space travel in your story, then at some point, some of your characters will need to know about navigating through space. Even if a computer/AI does the actual controlling of the ship, someone probably needs to know the basics. Unless, of course, you want all your characters to fail astronavigation (repeatedly) like Rimmer from Red Dwarf. Not to mention, computerfail is a common plot device.

To the stars and beyond*!

*Not actually very far beyond.

The Stars

The first, conceptually basic method is by looking at the positions of the stars. This is a bit different to sailors navigating by the stars.

The Earth rotates about its axis once ever 24 hours. That means over the course of a night, stars appear to move across the sky; the stars aren't actually moving, it's the planet. But if you know the time and where the stars should be at that time, you can use that information to navigate fairly accurately. Even if you don't have precise instruments, the Southern Cross or the North Star can point you in the general direction of south and north. (These two point to or are located close to the southern and northern celestial poles, respectively. The celestial poles are located along the line where the Earth's rotational axis extends into space. As stars move across the sky at night, they will appear to circle one of these points. Unless you're at the equator, in which case they will move straight from east to west.)

If you're in interstellar space, the rotation of the Earth is supremely irrelevant. However, if you know the exact locations (in the galaxy) of at least three stars and can measure their directions relative to you with precision, then you can use that information to triangulate your position.

The tri in "triangulate" gives you the hint that you only need three stars to be able to pinpoint your position but, because there's only so much accuracy with which directions can be measured, the more stars you use, the more accurately you can determine your location. Another good reason to have more than three reference stars is so that you (or, y'know, the computer) can still navigate when you're on the other side of the galaxy and can't see them any more.

As far as re-identifying stars goes, the spectra of normal regular stars are a bit unique. That is, the temperature of the star combined with the exact concentrations of various elements that make up the outer layers of a star are like a fingerprint and (usually) don't change very rapidly. So if you find yourself coming out of a mysterious wormhole, and you have a spectrograph on board, you could take some spectra, find enough reference stars and get the computer to work out your location for you. Yay.

(One final note: you would want a computer to take all the spectra and do the comparisons. Really, you would. I mean, the calculations of stellar positions are at least possible by hand but if you don't already know what stars you're looking at, there is no way you want to be comparing those squiggly lines by hand. Trust me on this.)

Astronavigation 101, unit 1: pass.

Speeding stars

OK, so what if you know more or less where you are, but you're not sure how fast you're going? First, I need to point out that speed is entirely relative. It is impossible to determine an absolute speed for anything. On Earth, we tend to measure speed relative to the ground or, sometimes, relative to the wind. However, the Earth is spinning and hurtling around the sun at about 30 km/s. The sun is, in turn, careening around the centre of the galaxy at about 220 km/s. The galaxy is streaking through space at about 550 km/s relative to the CMB (cosmic microwave background radiation).

And yet, here we sit in front of our computers/smartphones/iPads and (with the possible exception of those of you reading this on your phone on public transport) it feels like we're sitting still.

The moral of the story is that we can't feel speed. What we can feel when we're on a moving train, or taking off in an aeroplane, or in a car going around a corner is actually acceleration. And it's not just us, Einstein's equivalence principle tells us that (assuming there isn't some window for us to look out of) there is no possible way to tell the difference between sitting still and hurtling through space at eight hundred kilometres per second. We can make devices that detect acceleration (those of you who have ever had a smartphone or a camera change the LCD image when you turned it sideways have experienced this). What we can't do is build a device to determine absolute speed. Because speed is relative.

The good news is, there are lots of ways to determine speed if we can see where we're going. On a train, for example, you might look out the window and get an idea. In space, at reasonably non-relativistic speeds, the stars don't stream past you like they do in that old Windows screen-saver. The distances between them are so vast that they would not appear to be moving at all.

This is where your trusty spectrograph comes in handy again. All stars have some recognisable elements in them. Notably hydrogen, helium, maybe oxygen and carbon but depending on the star, these may not be present in sufficient quantities for our purposes. Every element has a unique set of emission/absorption lines. The wavelengths at which these lines are found are based on quantum mechanics and immutable. However, when you're moving towards or away from the source of the lines (ie, a star), the Doppler effect will come into play. The Doppler effect makes the wavelength of light that you (or your spectrograph) see appear to be slightly longer or slightly shorter, depending on whether you're moving away from or towards the source. So you can take a spectrum, compare the wavelength of the hydrogen (for example) lines with what they should be, then you can work out how fast you're moving relative to that star.

Incidentally, this wouldn't be a particularly tedious calculation to do by hand, assuming you had reference tables at hand and maybe some sort of (basic scientific) calculator. Also, if you remembered the equation.

So there you have it. Your characters can now work out where they are, and how fast they're going. Don't worry, though; they won't violate Heisenberg's uncertainty principle. They're not quantum particles. (And the uncertainty on the position will be too big.)

Astronavigation 101, unit 2: pass.

Friday, October 7, 2011

Winds of Change finally available for (online) purchase

As the title suggests, it is now possible to purchase Winds of Change, the latest Canberra Speculative Fiction Guild anthology, featuring my short story "Time Capsule". There is a PayPal/credit card button on the CSFG website here.

Table of contents and book trailer are also at that link, and I've blogged about them before here and here, respectively.

Wednesday, October 5, 2011

Let's talk seasons

Depending on where you live, you probably experience two or four seasons a year. Does this have to be the case on planets other than Earth? What causes Earth's seasons and what else might cause seasons on other planets? Read on!


Earth spins about an axis that runs approximately from the North Pole to the South Pole. It completes one rotation per day (and, indeed, a day is defined by the period of rotation). the degree of tilt of the axis never changes. This is because one of the fundamental laws of physics is that angular momentum must always be conserved. If the angle of tilt changed then the direction of the angular momentum would also change and this isn't possible without some sort of external influence (like an asteroid, which isn't quite something we want to happen).

What is this angle of tilt relative to? Well, it's the amount by which the axis of rotation differs from making a 90º angle with the plane of Earth's orbit around the sun. Hopefully the image below helps.

Nabbed from Wiki. Credit: Dennis Nilsson, NASA.
As I said, the tilt doesn't change, so for part of the year the northern hemisphere is more exposed to the sun and for another part of the year, six months later, the southern hemisphere is more exposed to the sun. In temperate climates, these periods of greater exposure are called summer while the periods of least exposure are called winter. The in-betweens, as I'm sure you're aware, are spring and autumn. Here is another diagram to illustrate this:
Light and heat from the sun is hitting more of the southern hemisphere than the northern hemisphere.
Hot and/or tropical regions, which tend to lie close to the equator, experience two seasons: the wet season and the dry season. Similarly, the other extremes of the planet, the poles, also experience two seasons: polar day and polar night. This is because during winter the sun never rises the poles and never sets during summer. Within the polar circle but away from the actual rotational poles, there will be a period of transition between the two seasons (of varying length, depending on distance from the poles).

The greater the axial tilt, the more pronounced the differences between summer and winter will be (see the bit about Uranus at the very end for a very extreme case).

OK, so axial tilt causes Earth's seasons. What else can cause seasons?

Near and Far

Another possible cause of seasons is an elliptical orbit. This occurs when for part of the year a planet is noticeably closer to its sun than for the rest of the year. So when the planet is physically closer to the sun, the whole planet experiences summer (not just one hemisphere). During the more distant part of its orbit, the whole planet would experience winter.

On Earth, key seasonal dates, such as the solstices and equinoxes, are defined by the length of daylight (shortest day/night of the year and equal day and night respectively). On a planet with an elliptic orbit the key dates would be defined by significant points in the orbit. The equivalent of the summer solstice would be the periastron, the point of the planet's closest approach to the star. The winter solstice would be replaced with the apoastron, the time when the planet is furthest from the sun.

An interesting thing to note is that, thanks to Kepler's second law, a planet will move more quickly in its orbit when it's closer to its star than when it's further away. (If you follow that wiki link, there's a nice little animation which sort of explains it.) The result is that summer on such a plane will be briefer than winter. The more eccentric (non-circular) the orbit, the greater the difference between the lengths of summer and winter (and the closer the planet will be to its sun during summer). Could make for an interesting cultural interpretation of the seasons.

Pulsing star?

Some stars vary their brightness. Cepheid variables, for example, pulse with a regular period (which can be anywhere from one day to a few months). Theoretically, this could induce a seasonal variation for any surrounding planets. However, there is a problem when it comes to life evolving on such a planet. These stars are unstable and won't last very long (on an astronomical scale) in their pulsing state. This makes it a bit more difficult to justify having an inhabited planet around them. Maybe a planet with a colony that's studying the star. Anything more natural probably wouldn't last or might not have enough time to have evolved (depending on the size of the star). Of course, there's no rule saying impending doom couldn't be central to a plot.

Wacky planets

Uranus is sideways. (Also, the rings aren't
really red, just coloured that way for emphasis
here.) Credit: Lawrence Sromovsky, (Univ.
Wisconsin-Madison), Keck Observatory.
via APOD
Uranus is an interesting case. It's axis of rotation lies almost in the plane of it's orbit. So for part of the year the south pole points directly towards the sun and part of the year the south pole points directly away from the sun. In between is a transition similar to the type of seasons Earth experiences, but with more extreme beginning and end.

Of course, Uranus is too large and with too dense an atmosphere to support life as we know it. However, it's possible that a rocky planet more suitable for human habitation could also have this kind of extreme tilt. Everywhere except on the equator there would be periods of multiple days of darkness. Even on the equator, polar summer and winter would be spent in perpetual twilight.

I suspect this sort of configuration could also cause interesting weather/climate issues, but I think that would depend a lot on the atmosphere as well. Could be problematic.

Tuesday, October 4, 2011

More on Terra Nova

I had a few comments on my last post (and a surprisingly large number of hits--who knew writing about something so topical would be so popular?). Although I addressed the questions in the comments section there, I'm not convinced anyone will see them, so I thought I'd repost and expand my responses here.

Stars, not moon

The first comment pointed out that geeky girl in Terra Nova blamed the expansion of the universe for the stars in the sky being in different places, not the moon. My mistake. She's still wrong, though. The stars we see in the sky are all part of the Milky Way and hence too close to be expanding away from us (or more accurately, because they are gravitationally bound to the galaxy). They would still look different 85 million years ago, however. This is because all these stars, including our sun, are orbiting the centre of the galaxy. It takes the sun about 250 million years to orbit the centre of the galaxy. Even in 85 million years it, and all the other stars, would have all orbited part way around and be in different positions. The sun would actually have moved about a third of the way around it's orbit, but different stars closer or further in have different circumferences and would appear to have gone further or less far around.

The second commenter also raised a good point about the characters remembering the constellations, though. If the parents were young when they last were able to see the moon, it seems unlikely that they would ever have seen the constellations. Perhaps geeky girl studied them in class? (The parents don't actually mention the stars, just that the moon looks different and that they were young last time they saw it.)

Runaway moon?

The commenter two asked how, if the moon is moving away from us by 2 cm a year, has it not moved too far away by now?

Laser Ranging Retro Reflector, used to measure the exact distance
between Earth and moon, and how much this distance is changing.
Deployed by Apollo 14 astronauts.
Credit: NASA Johnson Space Center (NASA-JSC)
First, let me say that from bouncing lasers off reflectors left on the moon by Apollo astronauts, we know that right now the moon is moving 3.8 cm away per year. However, various theories suggest that the moon was moving away at different rates in the past. This makes sense since the Earth's gravitational influence becomes weaker as the moon moves further away, and because things like ice-ages would influence how much water was available for tidally sloshing around and influencing the moon.

In Terra Nova, the girl actually says the moon is moving away half a centimetre a year. I chose 2 cm when explaining it by accident, but it turns out this is roughly what palaeontological estimates predict the average may have been over that time (link and citations within).

A recession of 2 cm a year over 85 million years gives us a moon less than 2000 km closer 85 million years ago. Given that the moon varies more than that as it moves through closer (perigee) and further away (apogee) parts of its orbit now (at perigee it appears about 15% larger than at apogee), the real question is would the moon really be that noticeably bigger? If you're keen, you can use what I wrote in this blog post to work it out.

Of course, it might be. We only have theories and models for how the moon's rate of recession changes. But even using the present-day value of 3.8 cm/year, it would still only be 3200 km close 85 million years ago, which is less than a percent closer on average.

Saturday, October 1, 2011

Eureka & Terra Nova pilots: Sciencefail rant

You know what I really hate? Big budget productions with characters who are supposed to be geeky/nerdy/knowledgeable that say things that are wrong. When you have spent piles of money on special effects, isn't it in your best interests to make sure the dialogue isn't made of fail? As I'm sure you've probably guessed, this really annoys me. And, unfortunately, I've come across two pilot TV episodes in as many days that had a "smart" character explain something erroneously (where the fact it was an error wasn't part of the plot).


First up was Terra Nova, a show where colonists from a over-polluted future travel back in time 85 million years to where the air is fresh and dinosaurs roam the Earth. One of the important characters is a geeky girl whose main function so far has been to explain backstory in a sciencey and geeky way. Fine.

The moon looked bigger 85 million years ago because it was closer to the Earth. True story.
(Screen capture from pilot of Terra Nova.)
So back in 85 million years ago, they look up at the night sky and are amazed to see the moon because in their time the sky is too smoggy. The one of the parents says something like, "Was it always this big?" And geeky girl answers, "No, it moves two centimetres further from the Earth each year." So far so good. But then she says that it's because of the expansion of the universe.

That was when I died a little bit inside. The expansion of the universe is a large scale effect. Over cosmologically small distances gravity dominates. Like a lot. I touched on this in one of my galaxy posts when I said that the Milky Way and Andromeda will eventually merge. Basically, yes the universe is expanding, but it's only really far away things that are moving away from us. Even the nearby galaxies are being pulled gravitationally closer to us. Galaxies are made up of stars. Stars have planets around them and planets have moons. Our moon is much to close to the Earth for the expansion of the universe to pull it away.

So what is really causing the moon to drift away? Tidal forces, something else I've mentioned in the past. The moon causes tides on Earth by pulling water in the oceans towards it slightly, making it bulge out (and a bulge also forms on the opposite side to balance it). However, the Earth is rotating faster than the moon is orbiting it, so the bulge gets dragged along with the ground as it spins and in turn exerts a slightly different gravitational pull on the moon, pulling it forwards along its orbit. This causes an angular momentum exchange between Earth and moon--the Earth's rotation is slowing down and the moon's orbit is becoming wider (it's actually moving more slowly though...). Fun fact, that means tides would have been a bit higher back in the day, too.

There you have it. 85 million years ago, the moon was closer to the Earth because it hadn't had as much time to steal angular momentum from the Earth and hence widen its orbit. It has nothing to do with with the expansion of the universe.

Speaking of the expanding universe...

In the beginning there was the big bang. We don't know what caused it and for the purposes of my next rant, it doesn't really matter. At one point, everything was in the same place. Then it exploded.

I am going to digress slightly and talk about everyday explosions. (Well, hopefully things don't explode in your everyday life, but you know what I mean.) When something explodes, for simplicity let's say a bomb, then a sudden burst of energy--be it chemical or nuclear--pushes the material of the bomb (the outer casing or what have you) away from the centre. Depending on location and conditions, this material will fly through the air or water or whatever. In this sense, the big bang wasn't an explosion.

Matter, the stuff the universe is made of, did not explode out from a single location. It did not explode into anything because the universe is everything. There is nothing physically accessible outside it (M-brane theory notwithstanding). A common metaphor is this: imagine an un-inflated balloon with a bunch of galaxy clusters stuck onto its surface. The balloon part of the balloon is the universe. When you inflate it, the universe-balloon stretches and the galaxy clusters all move further away from each other. It's the space between the clusters that's expanding. You could make the balloon very small in its un-inflated form to get everything coming from one point. Then, at that point, everything was in the same place; all the space was together at the origin. Then it expanded. There is no single point that was once the origin, all the points were at the origin.

Imagine my frustration, then, when a genius scientist in the pilot episode of Eureka is looking for the origin point of the universe. It made me very angry. The fact that the MacGuffin of the plot hinged on his research was also a bit annoying. That he was trying to use an optical telescope to look for the beginning of the universe is just hilariously ridiculous (he would need to use very long wavelength radio waves, not visible light to do that--but I'll write a proper blog post about telescopes some time soon). It also really, really didn't help that the genius in question was a massively arrogant prick, but would it have killed the writers to make him a scientifically accurate prick? That would have mitigated my annoyance somewhat (not that much because the show is more sexist than it should be, but that's not a rant for this blog).

The moral of the story

If you don't take the time to get someone to check your facts (or if you do--and I know many Hollywood studios do--and then ignore the expert), you will piss geeks off. If you are making science fiction and geeks are a chuck of your target audience, why would you want to annoy them?

(And if you're wondering, I did actually like Terra Nova, it was just one line that irritated me. Eureka on the other hand, continued to annoy me with episode 2, even if irritating scientist prick wasn't in it.)

End rant.

PS You can read a bit more about the Terra Nova part of this (with more science and slightly less rant) in this post.

Friday, September 30, 2011


Well, today saw the launch of the CSFG anthology Winds of Change, with my story "Time Capsule" in it. Unfortunately, being on the other side of the world, I wasn't able to be there, but Twitter tells me it all went well. Cover art on the left and I'll post some links on how you can get your hands on it when I have them. (I believe the most reliable way to get a copy right now is from the Conflux 7 convention which is happening in Canberra this weekend. ;-) )

On a completely unrelated note, New Scientist have this neat article about detecting life on other planets. Unfortunately, it requires a free registration to read (and is only going to be freely available for 5 more days). Which is unfortunate for those of us who lack subscriptions. On the other hand, here is a link (pdf) to a poster that accompanies their article (jpeg here). I don't think you need to sign in or anything to see it.

And in the inane memes department, I made a word chart thingy with Wordle. I think it just used the first page-worth of blog posts, so it's a bit skewed. Still, word chart thingies are cool.

Click to enbiggen.

Wednesday, September 28, 2011

Day/Night (super) Stars

A supernova is the explosion of a large star that has fused all its hydrogen into helium (and other, heavier, elements). Well, actually, there are two types of supernovae. The first sentence describes a core-collapse supernova, which is all supernova types other than Type Ia. Ia supernovae occur when a white dwarf sucks so much matter from a red giant companion that it collapses under the weight and explodes. This blog is not about the differences between types of supernovae.

This blog post is about how supernovae affect civilisations. I've mentioned them before in the context of sterilising planets and hence halting the development of life. Today, I talk about supernovae that are distant enough to not kill everything while still being clearly visible to the unaided eye.


In the past millennium, there have been several (obviously non-sterilising) supernovae visible from Earth. We know about them thanks to various historical records, which tend to get more scientific as they become more recent. Don't think that being distant enough not to kill us means that they aren't bright. Most of them have been brighter than all the other objects in the night sky (other than the moon) and some were even still visible during the day.

Some comments on the Milky Way's historical supernovae:
  • Lupus is now the remnant of a supernova which exploded in 1006. It is 2.2 kpc away (kpc = kiloparsecs; that distance is 7200 light years). It was visible during the day and apparently illuminated the landscape at night. (Interesting fact: if you take out the moon, it was brighter than the rest of the night sky put together.) It was recorded by Chinese, Arabic and European astronomers of the day.
  • Crab, as in the Crab Nebula and the Crab pulsar, is the remnant of the supernova that exploded in 1054. It is about 2 kpc (= 6500 light years) away and was well documented throughout Asia and the Middle East. It was visible in the sky for two years, though it was less bright than Lupus (due to there being more dust obscuring its light in that direction), it was very much visible during the day.
    Crab Nebula Mosaic from HST
    Image Credit: NASA, ESA, J. Hester, A. Loll (ASU)
    Acknowledgement: Davide De Martin (Skyfactory)
  • 3C 58 is one of the less inspiring names for a supernova remnant (pre-dominantly pulsar in this case). It was seen in 1181 by Chinese and Japanese astronomers and was only visible a night albeit as the brightest star in the sky. It's possible that the pulsar in that direction is older than the supernova event, but its hard to know for certain. It is 3.1 kpc (= 10 000 light years) away.
  • Tycho is the next supernova on the list. It exploded in 1572 and is named after Tycho Brahe not because he discovered it (how can you "discover" something that everyone can see, even during the day) but because he studied it extensively (some have said obsessively). It inspired him (and others) to revolutionise the astronomy of the day.
  • Kepler came next, with his supernova which was first observed in 1604. (4.8 kpc = 15 600 light years away.) It was bright enough to be visible during the day, but not when the sun was high. As with Tycho, Kepler didn't discover it but he wrote a book about it, which led to it being named after him. Wiki says this was the most recent observed supernova in the Milky Way, but there are two more about which less fuss was made because they were less glaringly obvious.
  • Cassiopeia A probably exploded in 1680 but that date uncertain. It was noted down in a routine sky catalogue by the first Astronomer Royal, John Flamsteed, then later erased as an erroneous entry because there was no long a star at that location. The modern remnant wasn't discovered until 1947, after which it was linked to the erroneous catalogue entry. Although the remnant is 3.4 kpc (= 11 000 light years) away, it wasn't easily visible because of the large amount of dust in that direction.
  • Speaking of dust, this last supernova is an interesting case. It doesn't have a nice name, merely one based on its galactic co-ordinates: G1.9+0.3, or G1.9 for short. No one saw it explode. there is a lot of dust in that direction. Most of the dust in the Milky Way lies in the plane of the disc and, looking towards G1.9, we are looking right through that disc of dust. From the speed of the remnant expansion, we predict that it exploded around 1868. Anyway, this one is less relevant to the thrust of this post, I just thought it was cool.
You may have also heard of supernova 1987a (which exploded in 1987, hence the moniker), but that was actually in the Large Magellanic Cloud, not the Milky Way.

Because I can, here is a little graphic showing the various directions of these supernovae:
Image credit: NASA/CXC/M.Weiss

Auspicious portent?

So supernovae are pretty cool (or incredibly hot, if you want to be literal about it) and now it's time to tie it back into stories.

Before we, as civilisations, knew what supernovae really were (and to be fair, that occurred relatively recently, compared with all those historical supernovae), they were seen as new stars, visiting stars. In fact that's what the "nova" part indicates: newness.

Lacking a physical explanation, imagine what those people must have thought when a new light appeared in the sky and then, incredibly, was visible during the day. It's the sort of thing that, these days, might make someone less abreast of astronomy think of aliens. What would it have been back then? Portents?

We know that comets were often hailed as portentous, so why not an auspicious supernova? Supernovae are even rarer which, one would think, would make them even more significant, mythologically speaking. In a world of myth and legend, what might the appearance of a bright new star lead people to do? I hesitate to suggest that people would panic (unless goats with two heads were born at the same time, maybe) but it would surely affect their lives. Especially if it lit up the night enough to see by (like Lupus probably did).

In a world of myth and legend, what might someone do if a new star lit up the day sky? Would they, perhaps, set out on a quest to follow it? What would their reaction be to whatever they found beneath it on their journey?

Sunday, September 25, 2011

Two links. Because I can

First, cells made out of metal, or at least, research heading in that direction. New Scientist has the story.

And here's a picture to capture your imagination: a supermassive black hole at the centre of a galaxy... stars flit around it in tight orbits. Some of those stars have planets. Some had planets but they were ripped from their orbits by the black hole's gravity. Starless planets, hurtling around erratically, if not being pulled apart, then smashing into each other. Their deaths leaving behind a dusty shroud. New Scientist. ArXiv.

It's posts like these that make me think that Tumblr might be a good idea. (Of course, my usual weekly posts are much less Tumblresque.)

Wednesday, September 21, 2011

Responsible world-building

Something a little different this time. Despite my usual spiel about getting the science right and then attempting to elucidate said science, sometimes you just gotta make stuff up. Sometimes you really just need some FTL* spaceships or your whole plot falls over. There are only so many times you can write a story about slow space travel — or even relativistic space travel. All that I ask is a little consistency. So I'm not going to talk about building worlds in the sense of planets (there will be many other posts about that), I'm going to talk about making up convenient science in a sensible and coherent manner.

World building: not just about worlds.
Snagged from APOD.
Illustration Credit: David A. Aguilar (CfA), TrES, Kepler, NASA
Some things are physically impossible. Some impossibilities are standard science fiction tropes, and that's OK. I've mentioned FTL, there's also telepathy (which, as Asimov masterfully showed, doesn't actually require space opera or science fantasy to operate) and worm holes. I am a bit more suspicious of inertial dampeners and hyperspace, but it does sort of depend on the story. I'd lump teleportation into the former list too, but that's a good example of something that we thought was impossible that we can sort of kind of almost start to do. Scientists have teleported photons across a lab and, more recently, I remember reading about a Bose-Einstein condensate (a small collection of atoms) being teleported, but I can't find a link right now so I'm hoping I didn't imagine it.

What they're actually doing with the teleportation at the moment is teleporting the quantum state of the photons/atoms. (I say this because I'm going to talk a little bit more about it shortly.) But that doesn't really matter. If you want to have people using teleports instead of lifts, then go right ahead. But you'd better have a good reason for them to have spaceships. Or a reason, at the very least, or pedants like me will whinge about your inconsistencies on their blogs and no one wants that.

The other thing with teleportation is that at some point you are somehow going to transfer a human-sized pile of data from point A to point B. I don't really care how you do it, but it's going to be a large pile (the upper limit, if you're curious, is about 1045 bits) of data that does somehow have to be encoded and then travel. I guess the teleportation part is implying that the travelling is instantaneous (you can invoke quantum entanglement, for example). But what about the encoding? How long is it going to take to encode that sheer quantity of information? (Actually, I did a bit of rough approximating and I got about 1029 bytes** for an average-sized person because the upper bound is, well, the upper bound.)

I assume you are going to let your encoding travel at the speed of plot. That's fine, if you're going to have some arbitrary reason, plot is better than most. However, if you're encoding people so that they can teleport, say, within a building in the space of a few seconds, then you had better not have them waiting a long time for their email to download. The speed of plot is the speed of plot, but really, you can't have different speeds of plot to suit your whim. It's sloppy and it annoys people like me. If you really must have them wait for their email, you had better have a damned good pseudo-scientific explanation.

To emphasise my point:
  • So let's say a person is worth around 1029 bytes (if you want to pick a higher number, knock yourself out; it will only make your data speeds more magically fast).
  • If it takes them 5 seconds to teleport from A to B (and assuming it shouldn't matter how far apart A and B are) then that's 2.5 seconds to encode the data and 2.5 seconds to decode it at the other end. Or maybe decoding is faster. Whatever. Order of magnitude is close enough.
  • So if it takes 2 seconds to decode 1029 bytes...
  • ...that's really fast. 
  • I mean, have you ever tried to copy a gigabyte-sized movie from your computer to your memory stick? (and assuming you weren't using Vista...) A gigabyte is 109 bytes so a person is 1019 gigabytes.
  • And don't get me started on storing that much data.
But this is science fiction, so those aren't insurmountable obstacles. But they are obstacles that, once surmounted,  have vast-reaching ramifications. Like email. Or hacking into an enemy's database. So if you need slow transfer rates somewhere else, ask yourself why similar technology to what enables teleportation can't be used.

Obviously, these ideas apply more broadly than just teleportation, but that's the example I've run with. And with that I'll close this slightly sleep-deprived post.

Remember: build worlds responsibly.

* Faster Than Light, which is currently physically impossible.
**1 byte = 8 bits


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