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

Wednesday, September 14, 2011

Masers in Space, or Cool Stuff You Didn't Know Existed

I think the title of this post pretty well sums up what it's going to be about.

What is a maser?

I am going to go ahead and assume that you've all at least heard of lasers and probably experienced them in a pointing at things from a distance context. Did you know Einstein developed the theoretical underpinnings of lasers in 1917? He sure did a lot of fundamental physics for someone who didn't like the idea of quantum uncertainty.

Although it's now written all in lower-case, LASER was originally an acronym: Light Amplification by Stimulated Emission of Radiation. The acronym is actually a fairly good summary of how lasers work; they emit light (a form of radiation), which has been amplified thanks to stimulation. Yeah, OK, rephrasing it like that doesn't actually help. On the other hand, going into the quantum mechanics of it won't either. Briefly, a laser works thusly:
  1. You need an optical cavity, which is just a fancy way of saying a container (usually a metal tube) with mirrors at either end and filled with the right kind of material (which varies depending on the colour/wavelength you want to get out).
  2. You put some photons (particles of light) into it (or some other form of energy, like electrical, which will ultimately lead to photons) and they bounce back and forth thanks to the mirrors. The input light should be of a similar wavelength to what you want to emit.
  3. While the photons are bouncing around, the material inside your cavity — called the "gain medium" — absorbs some of them and then re-emits them at a very specific frequency/wavelength. The reason for the specific part is because quantum physics dictates that the intervals between different energy states (in the gain medium, in this case) have very specific and discrete values. The properties of your laser will dictate exactly which energy transition (and hence which
  4. So you end up with a whole lot of photons of the same frequency* bouncing around inside your cavity. At some point, you have more photons being emitted than are being absorbed and you can reap the rewards of your lasering. 
  5. When you let these photons out of the cavity, you are releasing a whole lot of light which is exactly the same wavelength/frequency/colour and, thanks to the properties of the cavity, which is perfectly in synch (you can think of it as focussed, which is also true but actually a different property). That's why lasers are singularly coloured and why more energetic lasers can burn.
That's nice, you may be thinking, but what in space does this have to do with masers? Well, dear readers, it is no coincidence that "maser" sounds very much like "laser". It's a bastardisation of the acronym, standing instead for Microwave Amplification by Stimulated Emission of Radiation. The principle is the same but with microwave radiation instead of optical** (and because of the longer wavelengths involved, the industrial construction is a bit different). Interestingly enough, the first laser built was actually a maser. (See the history section on the laser wiki article I also linked to above.)

* If you're wondering why I keep randomly switching between frequency and wavelength, it's because they're interchangeable via a simple formula and we scientists tend to just use whichever we feel like in the context. The formula, if you're wondering is speed of light = frequency x wavelength. And the speed of light is constant (more or less).

** All forms of electromagnetic radiation are in principle the same, just longer or shorter wavelengths. From the shortest — gamma rays, X-rays, UV light — to optical light that we can see with our eyes, to the longer wavelengths — infrared, microwave, radio waves — it all works the same way just with different amounts of energy involved.  

Um, so where's the space part?

Glad you asked! This is where it gets really cool. (Arguably lasers are already cool, but bear with me.)

 In space, anywhere where there are large collections of molecules — for example in molecular clouds (d'uh), around dying stars, and some planetary atmospheres — the following sequence of events isn't uncommon:
  1. Some external source excites a molecule. The source is probably starlight, but there are a few other things that could also do it. Beside the point at the moment. The term excitation refers to the molecule absorbing a single particle of light (photon) and thus increasing its internal energy level.
  2. At some point, the molecule will spontaneously de-excite, emitting a photon of exactly the energy difference between the excited and less excited energy states. (This could be the energy of the original photon it absorbed, but in the case of masers often the exciting photon jumps the molecule up several energy levels and it drops down them one by one.)
  3. The emitted photon goes on to be absorbed by another molecule of the same type (where there's one there's almost always going to be a bunch more) or it can stimulate another molecule to de-excite by exactly the same amount. (It's a bit of quantum magic, but it does happen.) And now you have two photons of the same energy.
  4. Loop steps 2–3.
  5. A whole lot of light of exactly the same frequency will escape the cloud (and some of it will shine at Earth, so that we can see it).
Sound familiar? Yep. There are natural masers in space.

If you are curious, some of the sorts of molecules which often exhibit masing* are water, carbon monoxide, methanol, hydroxide, molecular hydrogen, formaldehyde, ammonia, and a bunch more. We can easily tell the difference between these molecules because the exact energies of the light they emit is specific to the molecule. It's even possible to tell the difference between different isotopes of oxygen, nitrogen, carbon, etc. And yes, that means all those molecules are floating around in space or surrounding dying stars with other stuff ejected during their death throes.

* Science likes making up words.

One more thing...

Image credit: NASA/ESA
A cool link: Giant reservoir of water found surrounding a quasar (discovered thanks to water masers, although it doesn't explicitly say so in that article). Above is the image to go with it, because NASA/ESA are good at finding artists to draw cool things in space.

Sunday, September 11, 2011

Science fiction done right: Inherit the Stars by James P Hogan

So far most of the content of this blog has been more about the science and less about the writing. Today, however, I want to highlight a book that gets the science spot on.

Inherit the Stars by James P Hogan was first published in 1978 and is now available from Baen (it's even part of their free library). It's got a bit of a "Golden Age" feel to it but it's also recent enough that the science it covers isn't very outdated.

Now, I'm not saying that every mention of science in Inherit the Stars is 100% spot on and accurate today — it can't be, there's been too much progress in the past thirty or so years — but what really makes it stand out is the way in which it presents the day-to-day science and the scientific method.

The story starts when some lunar colonists come across a space-suited body on the moon. A very old space-suited body. Human and yet very much pre-dating human space travel. And so the mystery begins.

The the book can be best described as a scientific mystery as the characters — mostly scientists — try and work out where the body came from, not to mention who it is and why they were even on the moon. The best part is, they do it in a very logical and scientific way. I found it to be a very realistic depiction of how real scientists would go around trying to work something like this out, clunky 70s technology notwithstanding.

The way it was paced, with new hints and bits of information being gradually uncovered (or in a few cases, coming to them completely out of the blue) made it continuously interesting. The main character also goes off and does other things and time passes before new information is uncovered. Unlike in Hollywood, significant scientific discoveries take time to fully understand (y'know more time than just the speed of the plot). Also, because of how the facts were meted out it was difficult to guess the ending ahead of the characters. Which isn't to say that knowing science didn't help me guess a few things before they were revealed, but it was nice not having to read about dull characters that can't put the pieces together and see what's obvious to the reader.

So there you have it, if you want to see a shining example of science done right, go read Inherit the Stars. It's free, so what's stopping you?

(I should also mention that it's the first of a series, but I haven't got around to reading the others yet, so I can't recommend them either way.)

Winds of Change - Now with its very own book trailer

The wonderfully talented Nicole Murphy has made a book trailer for the upcoming Canberra Science Fiction Guild anthology Winds of Change. (I posted the table of contents here.)

And so, without further ado, the trailer:

Very cool.

Wednesday, September 7, 2011

Habitable Galaxies - Part 3: Galaxy Environments

This is part three in a series of posts about habitable galaxies. Post 1, covering types of galaxies and galaxy mergers, is here, last week's post 2 talking about active galaxies is here and this earlier post on the (most) habitable areas of our own galaxy is also relevant.

[Unrelated to the topic, but I wanted to say that I've been playing around with Blogger settings and made a favicon (the little icon that helps distinguish this tab from others) and an iOS home screen bookmark button. So now, if you're using Chrome or the latest version of Firefox (I suppose it should work for other versions of Firefox, but the second to most recent version failed for me) check out the little purple telescope on the white background. And if you're reading this on an iDevice, you can even see said telescope with a glossy Apple finish. What fun!]

So this week I'm talking about different galaxy environments. That is, the environment where a galaxy might be found, not environments within a galaxy (although I briefly covered that earlier). Let's start by looking at what sort of environments galaxies can be found in.

The universe has environments now?

What we mean when we talk about galaxy environments is more or less talking about how many other galaxies are nearby. It's possible to get isolated galaxies or galaxies clustered together in groups of varying sizes. Our galaxy, the Milky Way, is part of a group creatively labelled the Local Group, which has about forty-five members. Of these, the Milky Way is the second largest (probably), with Andromeda the largest. Other members include the Triangulum Galaxy, the Large and Small Magellanic Clouds and a non-literal pile of dwarf galaxies.

As far as classifications go, smaller collections of galaxies are termed groups, while larger collections—containing upwards of fifty more densely-packed members—are called clusters. This may seem like a bit of an arbitrary distinctions (what makes the Local Group a group and not a cluster if it has almost fifty galaxies in it?) but it's important to remember that while we know the Local Group is full of dwarf galaxies, other groups and clusters are too far away for us to be able to see their smaller members. So when we say a cluster has fifty members, we mean that many medium to large galaxies.

Galaxy cluster Abel 2218, from APOD.  The cluster is also a lens, but that's another story.
Image credit: Andrew Fruchter (STScI) et al., WFPC2, HST, NASA

Spot the difference

So what does it matter where a galaxy is, anyway? Well, when it comes to life, most of what determines habitability is internal rather than external to the galaxy. The only external influence I can think of which could inhibit life (and jump in in the comments if you disagree!) would be a nearby AGN blasting at the galaxy. And even then, I don't think it would prohibit life everywhere in the targeted galaxy, just in the parts being most irradiated.

However, there are some properties of galaxies which are dependent on their environment. In a denser environment, where there are more galaxies, there had to have been initially more matter for those galaxies to form from. Because there was (by chance) more matter in that area, it was more strongly gravitationally attracted to itself and hence formed earlier compared with a lone galaxy in a sparser environment. Our current leading theory of galaxy formation and evolution is called hierarchical assembly and one of its tenets is that larger (more massive) objects form first. In a sparse environment, matter is by definition more spread out and hence, as well as being more weakly gravitationally attracted to itself, has further to travel before it can clump and collapse into a galaxy.

The corollary to this is that big galaxies in clusters are older and more evolved (because have gone through more mergers, partly thanks to there being more proximate galaxies), while isolated galaxies are younger and have undergone fewer interactions with other galaxies.

Living around

As far as life developing in other galaxies is concerned, it seems pretty trivial now to make the conclusion that life would have had the opportunity to arise earlier in cluster galaxies and later in isolated galaxies. Group galaxies such as our own would fall somewhere in the middle.

On the other hand, cluster galaxies would have undergone more mergers, have a greater chance of having been in the path of an AGN and are more likely to be elliptical. Those first two points are merely hazards to the development of life, but the latter also gives rise to different experience for that life compared with our Milky Way existence. What off Earth am I talking about? The night sky.

Our night sky is covered in stars with the disc of the Milky Way running through them. An elliptical galaxy, not having a disc component, would not have such a band of dust, gas and denser stars. In fact, they wouldn't have much dust or gas at all, which means no nebulae and significantly fewer hints as to where stars even come from. Depending on the exact placement of the planet, they would likely have a more or less uniform distribution of stars in the sky, maybe with a brighter patch in the direction of the galactic core. Life that evolved in an elliptical galaxy might not ever get to observe young stars in their vicinity, let alone star formation. How might their understanding of astronomy and, in particular, stellar astrophysics be shaped by this? I think it's an interesting question to explore.

On the other end of the scale, we have isolated galaxies which could also harbour life (if they're big enough to develop sufficient metallicity in sufficient time). But if it's truly isolated, it might be that it's not possible to observe external galaxies with the naked eye. (We can, but they sort of look like stars until you put a telescope to them.)  Maybe such a civilisation would skip past the part of astronomy that labelled Andromeda and the Magellanic Clouds as nebulae but who knows how they might interpret distant blobs and spirals in the sky once they had the telescopes to see them? Also remember that isolated galaxies are going to be smaller and form later. By the time life even evolved there, would there be many other spiral galaxies left? How much more powerful would dark energy be at that point? How quickly would all the other galaxies be retreating from them?

How empty would the sky be?

Friday, September 2, 2011

Some Links!

Some interesting sciencey links, presented in the order in which I came across them (which I think is the order they were published anyway).

First up! This New Scientist article is about how the wakes of ships (the white "trail" they leave behind as they plough through the ocean) temporarily increases the albedo of the Earth—how much light from the sun it reflects. This would be good news for climate change (that is, enacting a more positive change and less the "oh gods we're all going to die in a tropical hell" sort) if not for all the greenhouse gases those ships also produce...

Next! This arXiv paper, "Kepler Exoplanet Candidate Host Stars are Preferentially Metal Rich", seems to back up some of the assumptions made in the paper I discussed a short while ago about the galactic habitable zone. In that paper they assumed that sufficient metallicity would be required to form planets and it looks like Kepler has confirmed that.

Penultimately! Forget about Martian meteorites containing fossilised life, simulations have shown that life from Earth may have made it off world and could be set to land on another planet. Could it be that when we finally get around to drilling through the Europan ice, we find Earthly extremophiles instead of aliens? Cosmos magazine have the full story.

Finally! National Geographic have an article about a newly discovered planet which has the potential to be Earth-like. Seems that it gets less energy from its sun than Venus does from Sol, but more than Earth receives. It's habitability thus depends on the appropriate weather conditions but with surface gravity 1.4 times Earth's it should be more or less possible to walk on the surface.


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