The aliens of the TV-series ‘Invasion’ (also: ‘Inversion Fish II’)

All episodes of the first season of the TV series ‘Invasion’, from Apple, are now available for viewing. If you are still planning to see the series later, stop reading now, because there are spoilers ahead.

--------------------------

The series shows an alien invasion of Earth from the viewpoint of a few individual people, here and there on the globe. The protagonists at first seem to be people randomly caught up in the events, but some later wind up playing more important parts. I wouldn’t be surprised if all of the remaining apparent bystanders will end up being close to the centre of things, but that will have to wait for future series (a second series has been ordered).   

In the early episodes no-one has a clue what is going on, an that includes the protagonists as well as the viewers. That uncertain state lasts quite a while, because the series is no hurry at all to speed up the story or to explain where it is going. This may be a reason why the ratings haven’t been very high. Personally, I do not mind that the story unfolds slowly. This ‘strategy of keeping the viewer in the dark also means that the makers do not explain much, and so did not have to insert the kind of technobabble that is often used in science fiction series to explain alien technology or biology. In fact, there was almost no explanation of how anything works, which was fine with me. 

There was one instance of an irritating wilful neglect of knowledge in the series: a child lies shaking in an apparent MRI machine with an EEG cap on, resulting in an apparent MRI image with overlaids spots of colour, prompting a passing neurologist to say that the EEG was flat. That's not how MRIs or EEGs work; I guess that a real EEG wasn’t considered impressive enough.  

Anyway, it takes quite a while before you see the actual aliens. When you finally do, they are just dark blobs from which spikes shoot out towards a nearby floor, wall or ceiling. You typically do not see them moving in great detail, but it is clear at one point that they more or less ‘invert’ themselves. That is not easy to explain in words, so it is good that the producers posted a short video on YouTube about how they designed the aliens. 

Here it is. The commentary at one point includes the following: ‘A biological entity that we cannot even begin to understand’. Well, I am not going to take that at face value... 

In science, it is always time begin doing just that. Of course, here we do not have have to deal with real alien biology, but just with a human design, and what one human can design, another can understand.
   
You may have to watch the video a few times to see exactly what happens. I still found that difficult, so I made a slow-motion version of part of the video.

And here is that version. Aha. Let’s analyse what we have seen. 

The aliens are roughly cylindrical, about 60-80 cm in length, with a diameter about half that. If they would be solid cylinders they would have a volume of 42 to 100 L, but they must be hollow, so I estimate their volume to be 30 to 60 L. If their density is the same of that of Earth animals, their mass would be 30 to 60 kg. If they would be denser, say with a density of 1.4 kg/L, their mass would be 40-80 kg. That makes them quite hefty.  

‘Inversion fish’
The animation shows rings coming in from the centre, moving forwards and outwards, after which the rings move backwards again, where they no doubt move back inwards and forwards again. The spikes on the rings can be seen to point forwards at first. Then they move backwards over the surface of the rings. I do not think that the rings are separate objects. It seems to me that they form a contiguous surface instead, one that moves over the substance of the animal. You could say that they invert themselves.

Believe it or not, but inverting animals, consisting of a torus with exactly such a gliding surface, has already been discussed on this blog, back in 2013. That discussion was inspired by Thomastapir’s ‘Moebius fish’. I called the resulting type of animal ‘Inversion Fish’, assuming such animals would be small and simple sea creatures, like jellyfish. With all the inversion going on, it would be difficult for them to form brains or guts, so such animals might have non-invertible parts. I meant to follow that first post later with a second one on the same subject, but I never did, for a variety of reasons. The good news is that I can label this post ‘Inversion Fish II’, bringing closure to that long-open end.

I now resurrected some old Matlab routines to animate the inversion fish and pimped them a bit. Here is the result of that; the Inversion Fish is still a simple ring, but it is now rotated to make it swim horizontally. The lines sticking out represent hairs that will help propel it through the sea. The animal was supposed to be at most a few mm in size. 

 

Here is a second animation: I stretched the animal to give it a cylindrical appearance, so it begins to resemble the aliens. 

 

And a third one Inversion Fish, cut in half. The cut surfaces help to visualise the movement of the surface. Note that the surface moves forwards on the inside of the animal, while it is moving backwards on the outside, with not much distance between the two. There is no way to attach the surface to the inner substance of the body, in the way our skin stays close to the underlying tissues. In essence,  something like this can only work if the surface is essentially loose from the subsurface. The easiest way to achieve that is with a fluid between the surfaces. That is why I compared the Inversion Fish to jellyfish: jellyfish are essentially also membranes with jelly in between. But in their case, the membranes do not move in opposite directions.     
     
The spikes
The spikes appear at various points on the bodies, shoot out quickly and in doing so vary in length. They are always straight, never curved, and their width tapers to a pointy end. These ends apparently attach themselves to walls, ceilings or the ground. I did not see anything in the way of suckers, feet, hooks, nails or anything else that could help to attach a fairly large mass to a ceiling or wall. The spikes do not leave any marks either, as far as I could see. What also struck me is that I did not see the spikes sagging in any way. If you use a rope to suspend a weight from a wall or ceiling, the rope will sag a bit. These spikes are also used as rigid legs, and so must be very rigid. All in all, they must be able to withstand compression as well as tension easily, even while they are being formed.  

Now making such a material presents quite a design challenge. Which material can be extruded and absorbed at will and can remain very rigid and strong while it also behaves as a fluid? The commentary says ‘It’s made of ferrofluids, so it can be hard, but when you touch it, it moves like mercury.’ I cannot say I know much about ferrofluids, but my short foray into the subject suggest that the term 'fluid' should be taken quite literally. I did not see examples of hard ferrofluids.

Could you evolve animals using ferrofluids biologically? Obviously, evolution has no preset aim and cannot set out to evolve a ferrofluid. Evolution could start with a readily available source of ferrofluids, or there should be a reasonable reason for an animal to produce them, and after that it can evolve in a different direction. In other words, how do you wind up with tiny magnetic particles permanently suspended in a fluid? And how would you wind up with a handy biological way to acquire and control magnetism? Those are extremely tough challenges, and I doubt they can be met.    

Conclusion
Are these aliens original? Yes, very much so, unless you feel that ‘original’ may only be used for something that that has never been proposed anywhere. That would not be the case here, as witnessed by Thomastapir’s Moebius Fish and the later Inversion Fish. But that is asking too much: I really like the inventiveness shown here.   

Are they realistic as products of biological evolution? I very much doubt it. It will not be easy for biological evolution to come up with an animal whose living matter is essentially the fluid surface of a torus, and in which that living matter can become strong and rigid at will. We should probably add some additional problems here: the animals have no recognisable sense organs, and their brain and other relevant organs would have to be malleable and able to continue working while being inverted (but perhaps you could actually do something like that to an octopus brain, while it would continue working; don't try it!). At the end of the series, the aliens all collapse when the mother ship is destroyed, which is in Earth orbit. The aliens must therefore have a means of constant communication that functions immediately over large distances; should we add radio to their list of improbable biological feats? 

Perhaps it makes more sense to treat them not as the product of biological evolution, but as the result of engineering? Are they in fact bio-inspired robots? I guess we'll see in future series.

Inversion fish I

In November 2012 I wrote about thomastapir's 'Xenohox Gazelle', an extremely original concept for alien animal locomotion. In that post I also mentioned that I might write about another of his inventions, the equally creative and original  'Moebius fish'.

Click to enlarge; copyright Thomastapir

The Moebius fish consists of a body sitting like a node in a complexly folded ribbon. The ribbon folds in upon itself, resulting in a complex movement. Please read Thomastapir's own descrition on his DeviantArt page, using the link above. I wish there was an animation though, as I would dearly like to see which part goes where. Luckily, the German firm Festo has produced a flying inversion device, wit a perhaps similar movement. Festo is a technology firm that often plays with biologically inspired designs, such as helium-filled balloons moving like jellyfish or manta rays. Their most recent devices include a robot flying like a dragonfly.

Festo's inversion device is shown above. This too is a helium filled balloon, shown to turn inside out in the air. It is remarkable difficult to understand what you are actually looking at. I will come back to such complex inversion shapes in a later post; the basic design consists of a series of tetrahedra (a tetrahedron is a four-sided object, with a triangle for each side). In the Festo 'inversion cube', the tetrahedra are connected to one another to form a ring. When I first saw the Festo film I immediately wondered whether that intriguing movement could be used for animal locomotion; thomastapir had already designed his Moebius fish by then though!

The whole concept of inversion shapes is interesting enough to consider how it works in a bit more detail. I will not tackle the complex shapes in this post, but will starts with the easiest version I could think of. I will call them 'fish', using that word in the time-honoured but zoologically incorrect fashion meaning 'animals regardless of descent, nature or shape, with as the only shared characteristic that they live in water'. The Festo animal is in fact a ballont, and there is no strong argument against such creatures floating in air rather then water on other planets; having them swirl around in water is so much simpler however that that is where I will put them.

The basic shape is a ring that inverts itself, so after a bit of programming here is a very simple version: a ring that continually inverts itself. I do not think that this flat shape lends itself well as a Bauplan for an animal, but give it a bit of thickness and there is room for muscles, say for starters circular muscles running lengthwise along the two rims. If one of the  two ring-shaped muscles contracts, that rim will contract and will tend to move inwards. Alternate the movement and you might get something like the 'ring fish' above.

It doubt that the animal has much to gain from the movement though: when the outer part of the ring moves downwards, that part will provide an downwards thrust, but at the same time the inner part moves upwards, providing an upwards thrust. The outer part has a larger area than the inner part, so perhaps there is a net downwards thrust, but the movement cannot be particularly effective. I wonder whether this also holds for the Festo thingy: the video is not too clear about it actually moving through the air, although it obviously moves in the air.

Let's give the 'ring fish' a bit more body. Its shape is now a torus with a triangular cross section. It is intriguing to see the movement. Again, the animal can be equipped with muscles running lengthwise around its body in the corners of the triangle. By contracting and relaxing them in the right order the fish could turn itself in and out continually as shown here. Perhaps shorter muscles running at right angles between the three ridges might help in contracting the successive ridges, to result in the inversion movement. But will it move through the water?

A natural development is to add more details, turning the torus into a smooth-skinned shape. The one above has a pentagonal cross section. The muscle arrangement would still work to make it turn inside out, but as the sides become smoother it becomes ever more clear that the inside-out movement, the 'inversion', is by itself not a sound propulsion device.

To achieve that we need a trick. Equipping the surface with something that provides traction, such as fins, would do the trick. Here, I added simple lines to the inversion fish. If the animal is microscopic the lines may stand for hairs, and at that scale hairs do provide propulsion. Lots of microscopic animals on Earth use hairs ('cilia') for that purpose. Note that the cilia do not always simply stick out from the surface, but move depending on the phase of the movement. The cilia are swung back during the upstroke so they do not provide much of a downwards force then, but they stick out during the downstroke, providing an upwards force. I assume that the animal could reverse its thrust to sim down, and if it turns on ist sde it can move horizontally. I animated just one ring of cilia, but there could easily be lots more, providing continuous force. For larger animals, change the lines into shapes with a bit of surface area, and there you are: the 'hedgehog inversion fish'.              

This design is not without its problems, unfortunately. The biggest problem is probably that it is none too obvious why they move in the way; this is rather a big problem, but I will largely ignore it -for now- . Their bodies are distorted greatly during movement: just have a look at the rectangular outlines on the body, and compare a rectangle on the inner aspect of the torus with one on the outside: to turn one into the other much stretching and squashing is needed. Some animals can do that, of course, such as octopuses, but all this distortion must limit the design severely. One way to avoid that would be to add a node to the torus that does not change shape, to house things such as a brain etc. Thomastapir's Moebius fish has such a body, and if I understand the design correctly, the body does not rotate. But if I were to equip the torus designs above with a body by just gluing it to the torus,  that body would still rotate along with the torus, so any eyes there would have to cope with a continuously rotating world view. The squashing and stretching can be solved completely by doing away with the torus and substituting a series of tetrahedra, as in the Festo device, but that is something for another post.