Evolution, Insects & Oxygen

One of the key elements of my novel the Tau Ceti Diversion was the unique setting I imagined for the story. Specifically, an alien planet where the top evolutionary niche was filled by an intelligent insect race.  So I needed to think about insect evolution, and how that evolution was affected by the amount of oxygen those insects could take in from the planet’s atmosphere to fuel their metabolism.

Now, it wasn’t going to be too much fun to have my human crew menaced by determined ladybugs or extremely intelligent grasshoppers two inches long, so I needed big insects! I needed a world where the entire biosphere – every single evolutionary niche, both large and small – was filled with insectoid life.

You think people shudder when they have to shoo an insect out of the living room window with a rolled up newspaper, how about having to face a three metre tall intelligent being, staring back at you with multi-faceted insect eyes? Creepy? Stay calm space-explorers!

dragonflycaterpllar lifecycle_thumb

On Earth, insects are small, and a variety of other life has evolved to claim the top evolutionary spots in the food chain.

The size of insects on Earth has been constrained by two main factors, the way they take oxygen into their bodies, and the amount of oxygen in the atmosphere. Change those two things, and everything changes. Insects were here first. If not for those two constraints, our little furry ancestors would probably never have made it out of their burrows, let alone up the primate tree.

Earth’s insects don’t actually breathe in the way that mammals do. Our insects take oxygen into their bodies through the process of diffusion, the precious oxygen passing across membranes directly into their cells, with waste gases passing out of the cell walls in the other direction. Our insects have a series of holes in their abdomen, called spiracles, that allow air to enter their bodies. From there, incoming air moves into a network of tiny tubes called tracheae. The biggest bugs have the longest tracheae, to allow them to get the most oxygen into their bodies.

Insects have a very limited ability to use their oxygen absorption equipment. They can open or close the spiracles by muscle contraction, and they can also pump muscles inside their body to try and increase the amount of air passing through the tracheal system, but to limited effect. The amount of oxygen they can extract from the air is always going to be limited by the tracheae shape and the rate of  oxygen diffusion through the cell walls.

In the Tau Ceti Diversion, human explorers come face-to-face with evolved life dominated by insects, thanks in part to the planet’s high oxygen atmosphere, and an evolutionary adaption of the alien insects that has given them true lungs.

That’s not to say Earth didn’t have some big insects. At the moment our atmosphere has around 21% oxygen (by volume). The concentration of oxygen in the air has gone up and down throughout Earth’s history, mostly in response to what was happening in the biosphere. Toward the end of the Carboniferous periods (300 million years ago), oxygen peaked at a maximum of 35%. At this time there were some pretty impressive insects – like dragonflies with wingspans of over a metre in length. That’ s one hell of an insect, and all with basic air diffusion to get the oxygen into its body.

On my fictional planet of Cru, orbiting Tau Ceti, the oxygen concentration in the atmosphere is more than 30 percent, which certainly makes things fun for the explorers. They not only have to deal with huge insect life, but also have to deliberately moderate their breathing to prevent hyperventilation, and they have to be careful how all that extra oxygen makes any sort of combustion in the atmosphere more aggressive.

My novel, The Tau Ceti Diversion, is a story about our search for new planets to colonise outside our solar system. Much of the action takes place on planet tidally locked to Tau Ceti that has some rather unique life forms. The novel is due to be launched on September 1st 2016 – not long now! – and pre-order is available on Amazon! Read more about what happens in the story here!

Stay tuned for a free chapter download, coming soon!

Tau-Ceti-Diversion-severed-ebook-cover (Medium)

 

Day Side & Night Side – Tidal Locking of Planets

So what is tidal locking? Our Moon is tidally locked to the Earth, always presenting the same face to us. That doesn’t mean that the Moon is stationary, far from it, it just means that it takes just as long to rotate around its own axis as it does to revolve around the Earth. The same thing can happen for planets, which can be tidally locked to their stars, always presenting the same side of the planet to their star, giving those planets a permanent ‘day’ side and ‘night’ side.

We could expect these planets to have some pretty unique characteristics, with a hot, dry side, and a frigid frozen night side. Some scientists have even dubbed them ‘eyeball’ Earth’s due to the likely combination of features that might develop.

one-side-planet eyeball earth

Source: space.com

In my SF novel, the Tau Ceti Diversion, the action is set on a planet that is tidally locked to Tau Ceti, always divided into a hot day side and a cooler night side. This set up was crucial to the novel, and to the civilisation that the stranded crew of the starship Starburst find when they land on the planet’s night side. Actually they were aiming for the terminator – the dividing line between the day and night sides – expecting this to be a temperate zone. But I can’t say much more without spoilers:-)

Tau Ceti is a G-class sun, around 12 lightyears from Earth. One of our close stellar neighbours. Could we expect that one of its planets would be tidally locked to its star?

Well, it did not take me too much research to realise that this is one very complex question. It would indeed be surprising to find a tidally locked planet around Tau Ceti. Finding a tidally locked planet might be more likely around a smaller M class star. But there are many, many variables that might allow a planet to become tidally locked to its star within a reasonable fraction of that star’s lifetime. The variables that might increase the likelihood of a planet becoming tidally locked early in the star’s lifetime include the lack of a companion satellite (i.e. more likely if there is no moon), a low initial rate of planetary spin, a low dissipation function (the rate at which mechanical energy is converted into heat), a low rotational inertia . . . even the rigidity of the planet can be variable.

So, all these variables gave me enough wiggle room to allow my planet to be tidally locked. Plus I had a secret weapon – a key bit of backstory that affected the planet’s spin at a key point of its history. But I can’t say anything about that either, not without giving away the story!

Stars are classified based on their spectral characteristics. The M-class spectrum contains lines from oxide molecules, particularly TiO, with absorption lines of hydrogen typically absent. M-class are the most common of stars, representing over 76% of our stellar neighbours.  So we might expect more than a few tidally locked planets out there. Of course these will be the smaller bodies, Earth-sized and smaller, so will not be well represented in our current exoplanet catalogue, which features a lot of big, Jupiter-sized and heavier planets due to the methods used to identify exoplanets (so far). M-class stars are light orange red in colour, from 0.08-045 solar masses and low luminosity (less than 0.08 of our Sun’s). This class features rare and exotic creatures that can rarely be seen by the naked eye, mostly red dwarfs, although some are red giants, or even red supergiants. The class also includes the intruiging brown dwarfs, which are ‘late’ class M stars.

My novel, The Tau Ceti Diversion, a story about our search for new planets to colonise outside our solar system, is due to be launched on September 1st 2016, and pre-order is now available on Amazon! Read more about what happens in the story here!

Stay tuned for a free chapter download, coming soon!

Tau-Ceti-Diversion-severed-ebook-cover (Medium)

Atmosphere on a Fictional Planet

So you’ve got your plot sorted out, and maybe some idea of the mass, radius and gravity of your fictional planet. The orbit puts it in the ‘sweet spot’ goldilocks zone where liquid water can be present on the surface. What sort of factors go into whether that planet, presumably an Earth-like rocky world, will have an atmosphere that can support terrestrial life?

Planets above a blue planet

The gravity of the planet is one key variable, along with surface temperature, and the strength of the planet’s magnetosphere, which can protect against atmospheric stripping due to solar wind.

The surface temperature of a planet will determine how much kinetic energy, and so velocity, the gas particles will have. If that temperature, and velocity, is high enough it will exceed the planet’s escape velocity and the molecules will fly off into space like tiny spaceship explorers. Earth has lost most of its very light gases like hydrogen and helium in this way, whereas the gas giants have enough gravity to retain them. We kept our water, and we’ve got a lot of it! If Earth was sitting where Venus is things would be different, the additional temperature would give those lighter gases like water vapour enough energy to escape, and also prevent any being trapped on the planet’s surface itself (whereas some is ‘sequestered’ on Earth as water and ice at our lower surface temperature). But beyond the early, settling down period where the lighter gases are lost, any world larger than Earth, orbiting in that goldilocks zone, will not continue to lose a significant proportion of its atmosphere through thermal processes.

Here’s a cool pictorial on thermal escape (source: Wikipedia).

Solar_system_escape_velocity_vs_surface_temperature.svg

Beyond that thermal stripping process, is where the magnetosphere comes into its own, deflecting the solar wind – one of the main non-thermal processes leading to atmospheric loss. The very thickness of a planet’s atmosphere (retained due to its gravity, and as a function of surface temperature), will also protect a planet from the solar wind, even in the absence of a magnetosphere. It’s thought that Venus’ thick atmosphere, ionized by solar radiation and the solar wind, produces magnetic moments that act out to 1.2-1.5 planetary radii away from the planet to deflect the solar wind, much like a magnetosphere (but an order of magnitude closer to the planet). In fact, it’s thought the dominant non-thermal atmospheric loss process on Venus is actually from a type of naturally induced electrical acceleration. On Venus, the stripping of the lighter electrons from the atmosphere causes an excess of positive charges, accelerating ions like H+ out of its atmosphere.

Our explorers need a breathable atmosphere, but they also need an atmospheric pressure like our own Earth’s.

My fictional planet of Cru, in the Tau Ceti Diversion, has comparable surface temperatures to Earth, but a higher surface gravity. The higher surface gravity, and its lower density, allowed me to assume a lighter atmospheric composition, and allow an atmospheric pressure, or weight of atmosphere, close to surface much like Earth’s. That atmospheric composition is crucial to having a reasonable atmospheric pressure – its not just the gravity of the planet. Venus, even though it has slighter lower gravity than Earth, has a crushing atmospheric pressure of 90 times Earth’s due to its heavier  atmosphere of CO2.

The Tau Ceti Diversion is due to be launched on September 1st 2016! Read more about what happens in the story here!

Tau-Ceti-Diversion-severed-ebook-cover (Medium)

Estimating Surface Gravity on a Fictional Planet

WARNING: MATHS CONTENT!!!

One of the things I had to do as part of the rework of my novel The Tau Ceti Diversion, is to try and work out the surface gravity of my fictional planets. From the Kepler data, there are two exoplanets located in the Tau Ceti system that are likely to be in the system’s habitable zone, or where there is the possibility of liquid water on the surface, and perhaps life as we know it.

To play around with my estimates of gravity, I used ratioed rearrangements of Newton’s law of gravity (law of universal gravitation) and a simple formula relating the density of a spherical planet to its mass and radius (these are at the bottom of the post in the ADDENDUM).

Here’s Newtons famous law:)

law of gravity

The two planets thought to be in Tau Ceti’s habitable zone are denoted Tau Ceti e and Tau Ceti f. What is known about these two planets is their likely orbit, eccentricity, and their mass. All of these properties have been derived by calculation, based on observed data, so are all known to within appropriate error bounds, but I’m leaving the error off my scribblings so things don’t get too messy.

Tau Ceti e is thought to be around 4.3 Earth Masses, or Me (i.e. 4.3 times as heavy as Earth), while Tau Ceti f, the planet that orbits a bit further out, is thought to be around 6.67 Me. For the astronomically minded, these two planets orbit at around 0.55 and 1.35 AU from Tau Ceti respectively.

So, here’s where I cheated a bit, like any good engineer. I started with the answer I wanted and calculated backwards to see if the answer I wanted led to reasonable base assumptions. This is not as cheeky as it sounds, because when you have an insoluble problem (i.e. not enough data is known for an explicit result), an iterative approach is often used.

For my story to work, I needed a surface gravity on my planet of no more than 1.2g – that’s twenty percent higher than Earth’s. But how could I get a gravity that low on a planet that was over 4 times the mass of Earth? The answer is that surface gravity is a function of mass and radius, or going a step further along the calculation path, mass and density.

I used a ratioed form of Newton’s law that allowed me to relate the ratio of two planets gravitational forces to the ratios of their masses and radii. I already knew the ratio of the gravities ( assumed at gTCe/gE= 1.2) and the ratio of the masses (MTCe/ME =  4.3), so could calculate the ratio of radii (rE/rTCe) at 1.89.  Using another formula that related the ratio of the two planet’s densities to their ratioed mass and radii, I could then calculate their ratioed densities (dens TCe/ densE) at 0.63. So at the end of all that, to have a surface gravity of 1.2 g, Tau Ceti e would have to have a density of 63% of Earth’s. Is that reasonable?

The density of Earth is 5.514 g/cm3, not too much different from the density of a rocky planet like Mercury (5.427 g/cm3), but a lot higher than other solar system planets like Jupiter and Uranus (1.326 g/cm3 and 1.27 g/cm3 respectively), comprised of lighter materials. A surface gravity of 1.2g on Tau Ceti e would put its density at around 3.5 g/cm3, less dense than our own rocky planets, but certainly in a feasible range.

So what sort of densities would you expect for the Tau Ceti system? One clue is the metallicity of the system, which is a measure of the ratio of iron to hydrogen in the star’s makeup. In the case of Tau Ceti, this is estimated to be around one third of our own sun. This indicates the star is likely to be older than the Sun, made up of stellar remnants left over from less evolved stars that have not had time to form as much of the heavier elements in their internal fusion factories.

So Tau Ceti is made up of lighter elements. Based on this, it was reasonable to assume that the planets in the Tau Ceti system would also be made up of proportionally lighter elements, and quite possibly in the range I had estimated. Tau Ceti e and Tau Ceti f are also large planets – much larger than our own Earth – so having a density in between Earth and our own gas giants also made sense to me.

Using the same planetary density I had calculated for Tau Ceti e, for the larger Tau Ceti f, gave me a surface density of around 1.4g for the bigger planet – just a little too high for feasible human colonisation – and that fit nicely with my story as well.

It was a lot of fun playing with these calculations, and thankfully the known science fit with my story, at least with some comfortable wiggle room!

The Tau Ceti Diversion is due to be launched on September 1st 2016! Read more about what happens in the story here!

Tau-Ceti-Diversion-severed-ebook-cover (Medium)

 

ADDENDUM

For those interested in the maths. . .

Density formula:  densp= Mp / (4/3*pi()*rp^3)

Where:

densp= Density of Planet (kg/m3)

Mp = mass of planet (kg)

rp = radius of planet (m)

In ratio form: densp1/densp2= Mp1/Mp2 *(rp2/rp1)^3

 

Ratio of Newtons law relating gravity, mass and radius of two planets:

gp1/gp2= Mp1/Mp2 *(rp2/rp1)^2

 

Tattoos in Fantasy

Cropped A3 Poster with Red Button
I’ve always been intrigued by tattoos. The awesome finality of having your skin inked has made me even more fascinated by traditions where tattoos carry a special meaning, such as the Polynesian cultures.

In my fantasy world of Yos, tattoos carry very particular meanings. Men and women are tattooed with a totem on coming of age, which has a religious meaning and marks inclusion in a particular sect and tradition – men inked on the chest and women on the cheek.

Then, both men and women gain tattoos that show their chosen path in life, their achievements and honours. This is so central to the cultures of Yos that to cover your chest (it’s a warm world) is a sign of deceit. Warriors will only wear armour in full-scale conflict.

In a world where many cannot read or write, the tattoos give a person’s history at a glance, where honour – and dishonour – is written in ink.

Here’s the cover from The Calvanni, that shows some of the tattoos of the Way of the Calvanni – or knife-fighter.

Calvanni front cover (Small)

Do you have any special tattoos that carry a particular meaning for you?

What’s Your Favourite Fantasy Weapon?

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One of the great things about writing fantasy is the fun you can have with weapons:)

In my fantasy world Yos, where my three-book Jakirian Cycle is set, all metal is present as a magical crystal called a glowmetal. These glowmetals are a naturally occurring blend of light and metal that cannot be created or destroyed. So in the development of weapons, swords and metal armour were out. Instead I developed various classes of composite ceramic.

Lanedd – which can be used for blades. This holds a razor-sharp edge, yet avoids the brittleness of pure ceramics.

Mought – incredibly tough material that can be cast into shape as armour or used for the haft of various weapons.

The longest practical lanedd blade that can be cast using the techniques available to Glassmiths in Yos is the ‘calv’ or long-knife. This is where the world ‘calvanni’ or knife-fighter derives.

On Yos the dualist’s weapon of choice is the greatscythe. This is a staff-like weapon with twin concealed blades, one at either end. The blades shoot out and lock into place. It is operated by a mechanism central to the haft . It is also the weapon of the Suul nobility.

I had a lot of fun trying to figure out how the greatscythe worked. After all – with no forged metal – I could not very well have conventional coiled springs.

Here’s what I came up with:

The greatscythe has a central fighting grip and a release grip slightly wider than this which is operated by twisting two rings. These have a thread on the inside that operates a rod moving parallel with the axis of the greatscythe. This movement switches what is known in knife-talk as an Out-The-Front or OTF mechanism.

To make this work I needed two separate types of springs in the internal mechanism, both which had to be some sort of natural material. The first I solved with small bone ‘leaf’ springs for the catches that lock the blade into position. For the main spring that drives the blade back and forward I used a rubber strap-spring.

The greatscythe itself tapers to the ends. Two cover plates attach to a hollow cast core and cover the dual mechanisms – sealed in place with a special mought (ceramic) that melts at a much lower temperature than the mought of the haft. So if the mechanism needs to be fixed the sealing mought can be melted away to free the plate.

What your favourite Fantasy weapon?

 

 

Worldbuilding – Unique Weapons

 

Cropped A3 Poster with Red Button

In my fantasy world Yos, all metal is present as a magical crystal called a glowmetal. These glowmetals are a naturally occurring blend of light and metal that cannot be created or destroyed. So in the development of weapons, swords and metal armour were out. Instead I developed various classes of composite ceramic.

Lanedd – which can be used for blades. This holds a razor-sharp edge, yet avoids the brittleness of pure ceramics.

Mought – incredibly tough material that can be cast into shape as armour or used for the haft of various weapons.

The longest practical lanedd blade that can be cast using the techniques available to Glassmiths in Yos is the ‘calv’ or long-knife. This is where the world ‘calvanni’ or knife-fighter derives.

On Yos the dualist’s weapon of choice is the greatscythe. This is a staff-like weapon with twin concealed blades, one at either end. The blades shoot out and lock into place. It is operated by a mechanism central to the haft . It is also the weapon of the Suul nobility.

I had a lot of fun trying to figure out how the greatscythe worked. After all – with no forged metal – I could not very well have conventional coiled springs.

Here’s what I came up with:

The greatscythe has a central fighting grip and a release grip slightly wider than this which is operated by twisting two rings. These have a thread on the inside that operates a rod moving parallel with the axis of the greatscythe. This movement switches what is known in knife-talk as an Out-The-Front or OTF mechanism.

To make this work I needed two separate types of springs in the internal mechanism, both which had to be some sort of natural material. The first I solved with small bone ‘leaf’ springs for the catches that lock the blade into position. For the main spring that drives the blade back and forward I used a rubber strap-spring.

The greatscythe itself tapers to the ends. Two cover plates attach to a hollow cast core and cover the dual mechanisms – sealed in place with a special mought (ceramic) that melts at a much lower temperature than the mought of the haft. So if the mechanism needs to be fixed the sealing mought can be melted away to free the plate.

Anyone else out there had fun with unique weapons?

The official launch of the Jakirian Cycle is being held next Thursday 13th March at Avid Reader in West End in Brisbane. You can register by calling Avid on (07) 3846 3422 or book on the events section of their site. Here is the link.

PS: Don’t forget to enter the Scytheman Book Giveway! I am giving away 5 copies of Scytheman, second in the Jakirian Heroic Fantasy series. The Giveaway ends on 10th March.