A gigantic dinosaur monster of 50m height and 20000t weight appears in the centre of Tokyo! The invasion of giant spiders! These are common scenarios in science fiction films. Mankind has always been fascinated by giant creatures. Whether it be a child or an adult, no one passes by the skeleton of a Tyrannosaurus rex without being awestruck. Thus, it is very easy to use such creatures in movies. But the key point of every monster movie is the “stats”. A height taller than a high-rise building and a weight nearing one of a battleship excites people before the movie even starts. The problem is that this is very unscientific (considering it is a “science fiction”).
Let us look at the dinosaur monster first. The moment the monster steps on to land, it will be crushed like tofu. Every structure in its body will collapse and the skeleton will give way, causing 20000t of meat to crash to the ground. Simply put, the monster is just too heavy. Let us hypothesise that the monster is the shape of a gigantic T-rex. Tyrannosaurus rex was 15m tall and weighed 7t. If a 15m dinosaur is stretched to the height of 50m, the height becomes 3.3 times the original. But as the width and depth need to be expanded by 3.3 times as well, the weight becomes 37 times the original. The question is whether the monster can support its own weight. Just as the volume increased by a factor of 37, the cross-sectional area of every part of the body increases by a factor of 3.3 x 3.3 = 11. As muscle strength is directly proportional to the cross-sectional area, the strength only increases by 11 times. Thus, the load on a creature’s body is the same as the factor of expansion (e.g. there is 3.3 times the load on the monster’s muscles). But this is only when the T-rex was simply stretched. According to the stats, the monster weighs 20000t - 2800 times the weight of a T-rex. To support 2800 times the weight with 11 times the muscle, the load on the bones and muscle is 250 times. This is equivalent to having 249 people the same weight as you on your back. Of course, the monster cannot support this and its bones will become crushed and its internal organs will all burst, causing instant death.
Similarly, a giant insect monster also receives the same load as its expansion. But unlike an animal, insects have an exoskeleton instead of a skeletal system. This structure cannot support the load caused by the expansion (also, if you stretch an ant that is not even 1cm to just 10m, the load becomes over a thousand times). Ergo, the monster will collapse instantly. A giant monster is an unscientific creature that can only exist in our imagination.