Category Archives: The Liminal Zone

Dunes

With The Liminal Zone foremost in my writing mind just now, I’m always eager to read space news about Pluto. And just recently another paper has been published analysing the surface features as revealed by the New Horizons flyby back in July 2015.

Audiobook cover
Audiobook cover

But before that, a quick reminder of the giveaway competition currently running for the audio version of Half Sick of Shadows. There were 5 copies each on Audible UK and US available free. Just follow this link, listen to the sample snippet, and get back to me with the answer. Some copies have already gone but others remain to be won! It’s absolutely free – if you don’t currently have Audible membership then you can sign up for a trial month at no cost, then cancel if you don’t like it.

Back to Pluto. The specific surface feature that the report found was dunes. Not, of course, sand dunes, but ones made of ice granules, moved about very slowly by the extremely light winds which stir the extremely thin atmosphere there. It’s a remarkable tribute to the way physical phenomena tend to mirror each other. The conditions on Earth and Pluto are radically different in ever so many ways, yet they share the ability for dunes to form on their surfaces. Like everything on Pluto, it all takes place on an immensely slow timescale – I doubt that these dunes move appreciably over a human lifetime. But nevertheless, there they are, adding to the richness and complexity of the surface features of a world which, not so long ago, was assumed to be utterly boring.

Cover - Dune (Goodreads)
Cover – Dune (Goodreads)

A science fiction reader’s first reflex, on hearing of dunes, is naturally to jump to Frank Herbert’s Dune. That world was bakingly hot, dry, and life was absolutely dominated by the survival need for water. The dunes there – sand dunes – covered the vast majority of the desert world’s surface, and concealed both exotic wildlife and a radical human culture. It seems unlikely that much life frequents Pluto, with a surface temperature around -230° Centigrade. But these days, it would be a brave person who would say it’s impossible. And The Liminal Zone is – among other things – about the human settlement on the margins of our solar system.

Finally – and since my main enthusiasm is not so much for Pluto as for its largest moon Charon, here is a video put together by NASA from the New Horizons flyby. It’s partly for fun, and partly because next week – June 22nd – is the 40th anniversary of the discovery of Charon! It’s only short, but quite cool.

After enjoying that, don’t forget the giveaway for Half Sick of Shadows!

Planet 9?

Another space blog post today, complete with some thoughts about life out there, and an extract from my work-in-progress The Liminal Zone.

First, though, the elusive Planet 9. For some time now, astronomers and space scientists have been speculating that an additional planet, of considerable size, lies out beyond Pluto. The evidence is indirect, in that such a planet has not been observed via telescope. Hence the matter is currently unresolved. But a recent paper argues that its presence would solve several unexplained issues, while its absence would create several more.

Orbital resonance in the moons of Jupiter (Wiki)
Orbital resonance in the moons of Jupiter (Wiki)

So what are the problems? Essentially, they come down to the logic of orbital dynamics, which says that you can’t just put a bunch of planets in random orbits around a star and expect them to be stable. Even though the gravitational attraction between two planets is small, it nevertheless exerts a steady regularising influence on the two paths around the sun. So the orbits of our sister planets show all kinds of patterns of ratios which at first sight seem remarkable (they’re still remarkable when you take gravity into account, but in a different way). And the more patterns that you see, the more you can infer about things you can’t see.

This, for example, is how the outer planets beyond Saturn were deduced before they were observed. The planets from Saturn inwards have been known since prehistory. But when careful observations with a telescope could be made, small but noticeable perturbations in their tracks were found. These pointed to the existence of unknown planets further out. The same principle explains why the orbits of Neptune and Pluto are synchronised – two of Pluto’s orbits match 3 of Neptunes. So, although Pluto dips inside Neptune’s orbit for a couple of decades every 248 years (one Pluto year), they are never at risk of colliding. These synchronisations happen all over the place – for example within the moon systems of Jupiter and Saturn, within the asteroid belt, or forming the delicate internal patterns of Saturn’s rings.

Now, Pluto is the first major body in the Kuiper Belt, a disc of space outside Neptune which we now know contains a decent number of small asteroids and similar objects. So it starts around 30AU from the Sun (AU = Astronomical Units, the distance between Earth and Sun). But it then Belt stops, quite abruptly, around 50AU. Why should this be? Why not feather off gradually?

Trans-Neptunian Object orbits (LIve Science / ESO)
Trans-Neptunian Object orbits (LIve Science / ESO)

Additionally, as we have built up a catalogue of these asteroids, a picture is emerging in which a surprising number have orbits around the sun which are aligned with each other. The simplest way to explain this is to suppose that some sizeable, but as yet unknown, object is synchronising them.

So, why has it not yet been found? Well, first of all, as Douglas Adams said, space is “vastly, hugely, mind-bogglingly big” (Hitchhiker’s Guide to the Galaxy, chapter 8). So although the potential planet is several times larger than the Earth, it is on average 20 times further from the sun than Neptune is – 600AU – with an orbit that is quite noticeably elliptical rather than circular. That means that there is a lot of space to search in, and also that it is dark and cold out there. There is not a lot for optical or infrared telescopes to detect. But each new discovery helps narrow the search window down, and some lucky group of astronomers may well announce a discovery soon.

Or, of course, not. It may be that the apparent alignment we see will be eroded by more observations. Which would be a bit of a shame, in that it is always nice to have unknown things to discover. It would also leave several other problems unresolved. Other things being equal, I’d like Planet 9 to be found!

Artist's impression, Planet 9 (Live Science / JPL-CalTech)
Artist’s impression, Planet 9 (Live Science / JPL-CalTech)

So, what might it be like to live there? For one thing, cold and dark. Our sun is still the nearest and brightest star by a huge margin. But at 20 times further away than Pluto, it gets just 1/400 of the solar radiation of any kind. Or if you like, 0.0003% of what we enjoy on Earth. You’d want to know you had reliable sources of heat and light, if you went there. And it will take a long time to get there. It is not a place for a quick jaunt. For reference, Voyager 1 is a little over 100AU from Earth and has spent about 40 years getting there.

Could there be indigenous life out there? Well, life as we know it depends on liquid water, and the surface of Planet 9 is way too cold for that. But possibly, there could be subsurface heat turning ice into water at some depth? Or perhaps, there might be a moon which would be subject to gravitational flexing, just as happens to the inner moons of Jupiter and Saturn. This could – maybe – provide enough heat to give us water. We’ll have to wait and see.

I haven’t yet written anything going that far out from the sun. In the universe of Far from the Spaceports, an Earth-Mars trip takes a couple of weeks. An Earth-Pluto trip takes a few months. An Earth-Planet 9 trip would take anywhere from seven or eight months up to just over a year, depending on whereabouts in its orbit it happens to be. Not a journey you’d make lightly.

The Liminal Zone (temporary cover)
The Liminal Zone (temporary cover)

The Liminal Zone takes place on Charon, the main moon of Pluto. The New Horizons probe returned some fascinatingly detailed pictures to us of these two, transforming them from hazy blobs to detailed worlds. New Horizons is currently en route to an object further out in the Kuiper Belt, 2014 MU69, popularly known as Ultima Thule, and is due to arrive early next year. Finding a second destination more-or-less on the flight path after Pluto was a remarkable thing in itself, as objects are so exceedingly thinly spread out there. Anyway, The Liminal Zone is not a financial fraud book like Far from the Spaceports or Timing – it’s more of a voyage of discovery, both personally for the main character, Nina, and more generally for the society she is part of. So here is a short extract – Nina is talking to Percy, one of the Charon residents, about events surrounding an emergency several years ago…


Something about his expression made Nina stop.
“But you didn’t actually see anything?”
He drew back a little.
“Seeing’s not everything. Haven’t you ever just known something for sure?”
His eyes held hers, suddenly very intense, and she felt a little internal quaver run through her body. She had hoped it wouldn’t show, but then she saw the trace of a smile cross his eyes.
“I’ve got Welsh blood, you know. It helps me comprehend things which maybe can’t be seen with the naked eye. And what about you, Nina? Where do you come from?”
She went blank.
“I grew up in Lacus Gaudii. On the Moon.”
He shook his head.
“Not that recent. Go back a few generations. Where did your family live? Before they came up to settle in that lunar lake of yours.”
The noise of the kettle was maddening. She withdrew inside herself, trying to escape the pressure.
“I… I don’t know. I suppose I could find out. It’s never mattered.”
He looked away, letting the moment pass.
“Ah, but it just might make a difference here.”
She took a long breath and tried again.
“But did you actually see anything?”


I’ll be posting more on progress into The Liminal Zone as it comes along…

How close are personable AI assistants?

A couple of days ago, a friend sent me an article talking about the present state of the art of chatbots – artificially intelligent assistants, if you like. The article focused on those few bots which are particularly convincing in terms of relationship.

Amazon Dot - Active
Amazon Dot – Active

Now, as regular readers will know, I quite often talk about the Alexa skills I develop. In fact I have also experimented with chatbots, using both Microsoft’s and Amazon’s frameworks. Both the coding style, and the flow of information and logic, are very similar between these two types of coding, so there’s a natural crossover. Alexa, of course, is predominantly a voice platform, whereas chatbots are more diverse. You can speak to, and listen to, bots, but they are more often encountered as part of a web page or mobile app.

Now, beyond the day job and my coding hobby, I also write fiction about artificially intelligent entities – the personas of Far from the Spaceports and related stories (Timing and the in-progress The Liminal Zone). Although I present these as occurring in the “near-future”, by which I mean vaguely some time in the next century or two, they are substantially more capable than what we have now. There’s a lot of marketing hype about AI, but also a lot of genuine excitement and undoubted advancement.

Far from the Spaceports cover
Far from the Spaceports cover

So, what are the main areas where tomorrow’s personas vastly exceed today’s chatbots?

First and foremost, a wide-ranging awareness of the context of a conversation and a relationship. Alexa skills and chatbots retain a modest amount of information during use, called session attributes, or context, depending on the platform you are using. So if the skill or bot doesn’t track through a series of questions, and remember your previous answers, that’s disappointing. The developer’s decision is not whether it is possible to remember, but rather how much to remember, and how to make appropriate use of it later on.

Equally, some things can be remembered from one session to the next. Previous interactions and choices can be carried over into the next time. Again, the questions are not how, but what should be preserved like this.

But… the volume of data you can carry over is limited – it’s fine for everyday purposes, but not when you get to wanting an intelligent and sympathetic individual to converse with. If this other entity is going to persuade, it needs to retain knowledge of a lot more than just some past decisions.

A suitable cartoon (from xkcd.com)
A suitable cartoon (from xkcd.com)

Secondly, a real conversational partner does other things with their time outside of the chat specifically between the two of you. They might tell you about places, people, or things they had seen, or ideas that had occurred to them in the meantime. But currently, almost all skills and chatbots stay entirely dormant until you invoke them. In between times they do essentially nothing. I’m not counting cases where the same skill is activated by different people – “your” instance, meaning the one that holds any record of your personal interactions, simply waits for you to get involved again. The lack of any sense of independent life is a real drawback. Sure, Alexa can give you a “fact of the day” when you say hello, but we all know that this is just fished out of an internet list somewhere, and does not represent actual independent existence and experience.

Finally (for today – there are lots of other things that might be said) today’s skills and bots have a narrow focus. They can typically assist with just one task, or a cluster of closely related tasks. Indeed, at the current state of the art this is almost essential. The algorithms that seek to understand speech can only cope with a limited and quite structured set of options. If you write some code that tries to offer too wide a spectrum of choice, the chances are that the number of misunderstandings gets unacceptably high. To give the impression of talking with a real individual, the success rate needs to be pretty high, and the entity needs to have some way of clarifying and homing in on what it was that you really wanted.

Now, I’m quite optimistic about all this. The capabilities of AI systems have grown dramatically over the last few years, especially in the areas of voice comprehension and production. My own feeling is that some of the above problems are simply software ones, which will get solved with a bit more experience and effort. But others will probably need a creative rethink. I don’t imagine that I will be talking to a persona at Slate’s level in my lifetime, but I do think that I will be having much more interesting conversations with one before too long!

A research snippet

I thought today I’d share some research I have been doing for my WIP science fiction book, The Liminal Zone.

Full moon (NASA/JPL)
Full moon (NASA/JPL)

For various plot reasons I needed to know the answer to the following problem. Suppose you were standing on the surface of Pluto’s moon Charon, looking up at Pluto, fully lit by the sun… how bright would that be compared to looking up at the full moon from Earth?

This depends on a few factors:

  1. How bright is Pluto compared to our Moon?
  2. How big are Pluto and Charon compared to Earth and the Moon?
  3. What is the separation between Pluto and Charon compared to that between Earth and Moon?
  4. How much light from the sun falls on Pluto or Charon compared to Earth and Moon?

The relationship between these various factors boil down to a fairly simple equation – comparing everything to the full moon brightness, which is fairly familiar to us, you have to:

  1. Scale up by the ratio of intrinsic reflectivity of the two bodies (called the albedo)
  2. Scale up by the ratio of the apparent area of sky covered by the two bodies
  3. Scale down by the square of the relative distance from the sun.

The apparent area can be calculated relatively easily knowing the radius of the body in question and the distance apart.

At this point you start looking up the raw figures from any of several science sites (a handy list follows below).

Earthrise from lunar orbit (NASA/JPL)
Earthrise from lunar orbit (NASA/JPL)

Let’s first think about the simpler problem of how bright a “Full Earth” is as seen from the Moon. The Earth is, on average, 2.5 times as reflective as the Moon (that’s averaging over cloudy and clear skies, land and water, etc), and the area of sky it covers is about 14 times that of the Moon. So a Full Earth as seen from the Moon is about 35 times as bright as the Full Moon as seen from Earth. Quite a sight.

Charon from New Horizons spacecraft (NASA/JPL)
Charon from New Horizons spacecraft (NASA/JPL)

Let’s move out to Pluto, and imagine we are standing looking up at a “Full Charon”. Charon is brighter than the Earth, is much smaller, much closer to Pluto than our Moon is to us, and much much further away from the sun (forty times further on average).

When you put all those figures together you find that the apparent diameter of Charon in Pluto’s sky is nearly eight times that of our Moon, so nearly sixty times the apparent area. Scale up for the extra brightness and down for the distance from the sun, and you find that Charon has about 1/6 of the brightness of our full moon. Probably still just enough to cast shadows.

Pluto from New Horizons spacecraft (NASA/JPL)
Pluto from New Horizons spacecraft (NASA/JPL)

And finally, looking up at a “Full Pluto” from Charon. Pluto is about twice the size of Charon so about four times the area. By way of comparison, that means Pluto would nicely fit inside either the top or bottom half of the constellation Orion – between belt and shoulders, or belt and feet. Pluto is also brighter than Charon. Put that all together and you find that Pluto’s full light is about two thirds that of a full moon here.

I found this quite a remarkable fact when I crunched the numbers. Go all the way out from our Earth to the furthest of the standard nine planets, and the experience of standing on Charon looking up at Pluto is almost the same – in terms of brightness – as standing here looking up at the Moon. A useful comparison for my character, who is doing just that.

Facts and figures for the curious…
Albedo values (average)
  • Moon 0.12
  • Earth 0.3
  • Charon 0.45
  • Pluto 0.6
Radius values
  • Moon 1737 km
  • Earth 6371 km
  • Charon 606 km
  • Pluto 1187 km
Distances from planet to moon
  • Earth-Moon distance 384,400 km
  • Pluto-Charon distance 18,384 km
Apparent angular size
  • Moon from Earth 0.5 degrees
  • Earth from Moon 1.9 deg
  • Charon from Pluto 3.8 deg
  • Pluto from Charon 7.4 deg