Wednesday 22 December 2021

What does it take to make a reindeer fly?

This blog is about 'Furahan Biology and Allied Matters', and today we will stretch the 'allied matters' a bit, to produce this special Christmas post. Somewhere in Speculative Biology there must be a place to think about re-engineering mythological life forms, which is what this post is about.

The starting condition is simple. Thanks to globalisation, a most unusual subspecies of reindeer (Rangifer tarandus) has spread widely from its original area, so it can now be observed in skies over many parts of the world. In the skies? Yes, because these reindeer fly.       

It is not clear whether these reindeer can fly in their natural state, as they are only observed to do so when tethered to sleighs. This is slightly worrying, but even so, the force that keeps them in the air must be magic, as the reindeer lack any observable physical means to provide lift. While magic is a potent force in the imagination, in the real world it is noticeably difficult to acquire, so we need a more pragmatic approach. 

What would it take to make a reindeer fly in the real world? And I mean 'fly', not hurtling it through the air by strapping a jetpack to its back or using a large catapult. No, it must fly though biological means. The first problem is that reindeer have no wings, so we will have to use advanced creative bioengineering and splice in some wings. Done! That was quick...

Reindeer weigh around 100 kg, if we average estimates of male and female weight. But even these brand-new wings won’t make a 100-kg reindeer fly. And don't you start objecting that some pterosaurs weighed more than 100 kg and could still fly. We could in fact probably re-engineer the flying reindeer to achieve pterosaur-like mass, but the result would definitely look a lot like a pterosaur, and it should look like a reindeer, right?
Where was I? Oh yes, the 100 kg mass is a problem. Why? Well, take a 0.6 kg pigeon with a 70 cm wingspan. If you double its length, width and height, you get a wingspan of 140 cm and it will weigh 8 times the original weight. That factor 8 represents doubling of all three of length, width and height, so it is doubling to the third power (2 to the power of 3). By the way, for more on basic scaling of animals, see these posts here and here.

The problem is that lift is proportional to wing area, and area is proportional to the square of length. Doubling the pigeon's size makes the wing area four times larger, but that four times larger wing must carry eight times the weight. That won’t fly. (Sorry for that one.) We can make the wings extra large to compensate for the larger weight, but that will also increase weight. As explained in another post, at some point of increasing body size the wings can no longer carry the body.  

The obvious solution is to shrink the reindeer until it weighs as much as something that can fly. Say a rather massive goose at about 5 kg. Some calculations reveal that the reindeer's length should then be 25-30% of the original length of 180 cm.

To allow room for massive wing muscles, everything else must be reduced in weight: to decrease gut size it needs a new diet, mostly sugar; we can then also abolish the teeth, because it doesn't need them and won't get caries. We'll give it slender legs, tiny light hooves and fluffy hair. You will probably insist on antlers, so antlers can stay, but they will be much reduced. We can splice some red bioluminescence into its nose, to put the cherry on the cake.    

Done! A realistic flying reindeer! 

Click to enlarge; copyright Gert van Dijk & Roelien Bastiaanse


Happy holidays!

Thursday 16 December 2021

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.    

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.