Rodan - also known as the fire demon - can be seen clearly destroying buildings underneath him when he flies. Today we're going to find out the scientific cause of this. The effect can be seen in this video:
Rodan has the capabilities to fly over mach 2, or two times the speed of sound. He easily overtakes fighter jets, which fly at a staggering 2500 km/h or 1.95 mach.
The film has a not-so-satisfying explanation - apparently Rodan can create hurricane like winds that can destroy miles of buildings. We think that it can also be caused due to a sonic boom. But can Rodan really fly that fast, or is it impossible for a monster of his size?
Rodan's mass is given as 39,043,000 kg. Assuming Rodan flaps at an angle of 30° to the normal, and that he flies at a speed of 2 mach or 686m/s. In the following diagram,
Line A represents the flap of the wings of Rodan. He does not flap vertically downwards; that would make him travel only upwards with no horizontal displacement. Instead, all birds flap at an angle of approximately 30 degrees to the y-axis.
By flapping, he generates a force to the bottom right, which in turn causes a reaction force which propels him forwards and upwards. Finding out the accelration generated by Rodan's flapping:
$$Slope={y\over x}=tan \theta$$
$$\therefore tan\:\theta={Force\:spent\:against\:gravity\over force\: spent\: to\: move\: horizontally\: forward}={mg\over ma}$$
$$\therefore tan\:30°={1\over \sqrt 3}={g\over a}$$
$$\therefore a={g\sqrt 3}={9.8 * 1.732}=16.97ms^{-2} ≈ 17ms^{-2}$$
An acceleration of \(17ms^{-2}\) is very, very high. Coming to the energy required to produce such an enormous acceleration. Assuming displacement is 10,000 m,
$$W=F·S,\;\;F=ma$$
$$\therefore W=ma*S$$
$${W = {39,043,000 × 17 × 10,000} = {663,731,000 × 10,000}}$$
$$\therefore W≈6.63*10^{12}J$$
This is an INSANE amount of energy. To sustain just 10 km (10,000 m) of flight, Rodan would require 6.6x10¹²J, or about 1.6x10⁷ kcals!
To put that into perspective, a whale contains about 90,000 kilocalories. The energy Rodan needs to fly 10 km is equivalent to eating about 180 adult Blue whales. Yes, one hundred and eighty. And that's just the energy required to travel! What about energy to sustain bodily functions, such as breathing and heartbeat? Double that figure. Then triple it.
There is no way a creature like Rodan could ever exist in our world. It would likely die of starvation in the first ten seconds of birth. That, sadly, is the reality. Unless the laws of physics do conform to movies, which they don't, Rodan can't exist. Oh well, at least we figured out why Rodan causes buildings to tear apart.