It's Sol here back again with another blog, this is less, a theory blog and more a deconstruction. This is an attempt to come up with realistic (as this topic allows) explanations for tropes in the Ultra Series. Previously I did Alien Invasion, now wer're doing Giant Monsters. If possible, I'm also going to be coming up with some 'realistic' versions to a kaiju. If successful, maybe the guys over on UltraFan can use it for worldbuilding.
Why Theropods Don't Work
So first things first...making a kaiju shaped like a T-Rex or other dinosaur...is nowhere as realistic as some people may think. Firstly, dinosaurs only grew to their size because oxygen levels were much higher. It's why elephants don't grow any bigger than they do. Even so, the largest known dinosaur to have ever existed, has a similar mass to a blue whale, the largest animal alive today. This means, that if you had a T-Rex alive to day, they would collapse from a lack of the needed amounts of oxygen, let alone one the size of a kaiju, or not even grow that big. There is also the Cube Square Law, the main reason we don't have giant monsters in real life. This states, in short, that the larger a creature is, the more pressure it is placing on its body, specifically the system that keeps it upright, it's bones. This means that anything over twenty to twenty three feet tall...the larger it gets past that point, the more likely it will collapse on itself in a blood mush. Heck at that size, tripping and falling could be fatal. That is not even a joke. And yes...that means the classical Godzilla with his thick leg muscles, is more realistic than Zilla, with his sinuous frame, from that perspective... On to the next part!
How they may function
So the question has to be asked, why can't a giant dinosaur just stroll through a city, without crushing itself? Well the answer is mainly because a normal endoskeletal system (an internal skeleton) doesn't allow for that... The bones would break, and exoskeletons aren't much better. You could have a mix of the two...and that still would not be as large as we would like to call it. The most realistic 'conventional' kaiju would be one of the quadrupedal ones, the four legged beasts like Baragon, or Anguiras.
However I expect people want the upright lizards and other similar creatures. Well for that, we really need to look for 'alternate' biology. The more conventional we demand these things be...the less realistic they are.. Perhaps the most realistic explanation I have found (and let's be honest none of these are really realistic, they just 'sound' that way) comes from Monster Planet, where Godzilla's bio-matter contains metallic elements, making him rather strong, and also able to conduct electromagnetic energy to create a personal shield ala Superman. In the Ultraman Tiga Manga/Manwha/Comic (I really don't care what you call it, but I will call it 'manga'), there are diagrams of Golza and Melba showing their internal anatomy. Golza's bones are described as being as strong as steel, and Melba, while hollow like a bird's are also described as being incredibly strong, to withstand the incredible weight put on them. Again, the idea that their bodies, their cells, contain metallic elements, something akin to Carbon Fibers helps to explain how they exist and how they are so durable.
There is one issue though, besides the Cube Square Law, this is body heat. Any living body produces heat, even if the creature was cold blooded, at that size, they would still be producing internal body heat. In fact a cold blood kaiju would be screwed as it wouuld not have the ability to deal with that heat like warm blooded creatures. It would cook itself to death. For this, maybe a monster's heat ray is less an attack and more a focused system of quickly getting rid of excess heat. Maybe those dorsal fins or structures not for show.
There are other options for biology, like 90's Gamera's surpsingly light build at just a 100 tons (I am not even joking at that...) or Legion's anatomy, or you could go the Shin Godzilla route and say that most of its internal anatomy is a complete mystery that baffles science. Yet there is one more mystery that is rarely solved.
In short, the most 'realistic' monsters, are the most alien, exotic, even absurd to us. This is because they are clearly not running on the rules, they are clearly breaking. Take for example Legion from the Gamera Trilogy. It is an insect like creature made almost entirely of silicon, and with a muscular system, that works on air pressure, not unlike hydraulics. This means, that for the most part, Legion is one of the most theoretically realistic Kaiju ever imagined. It doesn't have a skeleton to break, and that frees up its mass to grow much larger, heck it even raises oxygen levels so that probably adds to its height.
What Powers Them
Now this is a question that I find is surprisingly rarely asked, and less often answered. What do these things eat? Really has anyone even thought of that? An elephant eats a massive amount of food that most people would find astonishing and it is nowhere near the limit of the cub square law. Now imagine a creature big enough to rival a skyscraper. So unless these things are eating continents barren they need an alternate source of energy. Just as monsters would not have a normal biology, if they were to exist. The most common form of sustenanace for Kaiju, ever since Big G rolled onto cinenmas in 1954, has been Nuclear Radiation, Gamma Radiation, Ionizing radiation (though that last part is more of an umbrella term). As strange as that is...it makes more sense then normal food consumption. A concept I've called Gammasynethesis. If it sounds similar to Photosynthesis well, you paid attention in biology class. To explain this, take Photosynthesis, the process by which plants absorb sunlight to produce food and food energy. It's actually a bit more than that. Most plants use it to combine the minerals they absorb, with the water they take in to form more bio-matter and grow. Yes that would also explain why Kaiju grow so grossly large. However, ionizing radiation, is a much more sensible source of food energy than typical...well food. However Kaiju would probably still have to eat sometime, just not as often as normal creatures, as 'food energy' alone does not make a creature healthy. There is also another, but possibly connected source of energy for a potential Kaiju, a Plasma Organ. Something I've heard about from the Godzilla franchise, it's either a heart, a stomach, or mix of the two, all mixed together with an organic power plant. What it does, in short would, be to take whatever it eats and use it as fuel, igniting the material, either through internal body temperature, electricity generated by the metallic elements in its body, a mix of the two, or mabye some magnet like organs around it. Plasma is produced when you heat something to state of gas, and also ionize it. Ionization, is when part of the electron cloud is loss, or a positiron in the atom's core is removed, to create an electrical imbalance, turning the atom positively or negatively charged. In short ionization radiation, is radiation, powerful enough to damage the atomic structure. It's why they cause cancer. Kaiju simply have in their bodies and/or cells the means to catch the energy and utilize it. A plasma organ would also be able to strip substance down to their elementary components. A potent sort of digestion. These elements can then be absorbed by the body for obvious reasons. Plasma, particularly this form, and especially raw, also produces ionizing radiation, interestingly enough. It's why when 90's Gamera spat out a plasma ball, it was surrounded by fire (also a form of plasma). Interestingly, it would mean that they Kaiju habit of shoot beams of energy, most likely plasma, is actually them vomitting up their last lunch, and spraying vommit is not as strange a defense in the animal kingdom as you would think. As Plasma produces ionizing radiation, it would also mean that it is feeding their gammasynthesis in a sort of cycle. If all of this seems like a stretch...well congrats you've just pointed out another reason Kaiju don't exist.
Where would they live
Frankly, sea monsters make way more sense than monsters lurking underground, if only because the water counters their massive weight. Even if we go with kaiju that live underground, four legged kaiju are still more realistic. That less weight on load bearing limbs than a bipedal creature. If there is a reason to have a creature like this live underground, it would be to collect minerals. The metallic elements, the metal components of its biology would be much easier to find underground. Presumably such a creature would have some system of detecting and finding these mineral, and tunneling, wherein the quadrapedal shape makes more sense. The minerals would be digested via the plasma organ and absorbed into its body, and with gammasynthesis fused with other elements to produce its almost bio-mechanical bio-matter and grow to its large size.
An amphibious nature, would make sense in that moving from the hot underground environment to the ocean blue, would help in cooling it down. Which would be a problem any creature of any size faces, maintain a body temperature, especially when they are massive. Also since they are running on gammasynthesis, they don't really need that much air, or oxygen filtered from the water to keep themselves alive, since the ionizing radiation is being used to keep their cells going.
With that in mind, such creatures would probably have nests, cooler pockets underground, and closer to the surface, or underwater caves. It does raise the question however, of why they would attack cities, why they would go on land, where they most feel their weight, where there is often no ocean to help cool them.
Or maybe they are cold blooded, aside the from the fusion reactor in their bodies, and its further pushes them to such temperature extremes, and is also why their bodies are so durable as to withstand tank fire. Maybe the do come to the surface, but through sheer luck or providence always away from human civilization, which is most next to some large body of water, at least 70% of our settlements.
Why they are attracted to Cities
The most sensible answer I can come up with...is food, and no not people...mostly not people. After taking into considering all the nonsens- I mean, theories I cam up with, the most likely reason a Kaiju would have for attacking cities, besides Nuclear Power Plants...would be the buildings.
We already established they would probably have metallic elements to their bio-chemistry, that they would search the Earth's crust for these minerals and obviously have some mechanism of finding them, they have a plasma furnace in their bodies for digesting them. Cities have something in abundance, processed metal, metal without any of the other stuff that has to be filtered out, metals in abundance in the skeletons of skyscrapers.
It may also eat people given the chance...because well, it can't just survive on metal alone, but there are giant squid in the sea and large marine animals in the deep oceans. There would be large quantities of fish, and other deep sea live.
So when Kaiju attack cities, they aren't simply destroying buildings that in their way, they are going after the metal contruction components inside, that their bodies want to grow and maintain themselves.
Kaiju may also be like Legion, and communicate long distances via radiowaves, and human civilization is off setting that and causing them to become territorial.