### Don Rosa's scientific wisdom

I finally met again Piero Patteri at Comunicare Fisica, a workshop about the comunication of physics, and Piero gave to me a book that the italian Disney's fun site Papersera.net realized for Don Rosa in 2011. Because I will be to Lucca Comics in order to speak about comics and science, I decided to publish here the english version of the article that I written with Piero for the book "Don Rosa: A little something special".
The physical law of the real world are enforced in a very loose way in the comic book world. Bouncing, smashing, hitting in harmless crashes are common events in the strips, at least since the brick thrown by Ignatz against Crazy Cat, actually continuing the paroxysm of comic actions in the mute movie era. Therefore is really surprising, and amazing from a physicist point of view, to find a comics artist showing a constant effort of supporting the humoristic side embedding his plots in a rather coherent physical frame.
Here we account for our feelings when exploring the features of the Rosa's physics both in the voyager in the micro world, in The Incredible Shrinking Tightwad, both in the outer space in Solar System in Attack Of The Hideous Space Monsters, each of them a must subject in the work of sci-fi writer. After reviewing the most amusing gag offered by teletransport in On a Silver Platter we eventually land in the realm of the Extraordinary Physics acting in On stolen time, and A Matter Of Some Gravity
In the micro world
The reducing machine appearing in The Incredible Shrinking Tightwad is an explicit citation of the Carl Barks' machine in Billions in the Hole, but the device found by ducks in the garret of Uncle Scrooge is defective, and once the squeezing has been started, the process proceeds indefinetely. So, beside the discovery of new dangerous features in an increasingly small world, the out-of-control evolution in the Rosa's tale enhance the thrilling plate after plate. In Barks' tale the size reduction causes a sudden flipping of hunter/prey role between ducks and ants, and just the timely rescue by Gyro Gearloose save their lives. Here Uncle Scrooge and Donald Duck fight at every stage, jumping on the coins in the bin like on pebbles in a stream, until these become the slippery walls of huge crack, or chasing away a ugly louse in the hair which soon becomes a monster; in the end in the dirty pocket of a Beagle Boy, the germs resembling mithological monsters Medusa or One-hundred-eyed Argo are on the point of overcoming them and only a deus-ex-machina intervention seems to be able to rescue them.
On the other hand, by the exploration of the new environment looking for an escape they discover realistic details, such as the grease on a hair, or the wood yarn embedded on the surface of a sticky plum; one could say they had nothing to the plot, but just their 'useless' presence conveys the feeling that ducks are really falling in an extraordinary, but extremely realistic world. So the way out jumping on the spikes of shaven beard is not a sudden trickery but the logical opportunity built all along the tale.
The hastening of events sometime reminds Hitchcock's hunting/escaping sequences, such as in North by Northwest or Vertigo, and like in the movies by the Master of suspence, the choching solution bursts into the stage, with Uncle Scrooge becoming again full size in the hand of a Beagle Boy

In the outer space
Again the foolish switch-on of a misterious device affects the physical property of the Uncle Scrooge bin. This time it looses its wheight, and the ducks must pursue it in the space, hoping to success in reversing the operation of the device.
The comment in the italian edition on Zio Paperone #132 emphasizes the tribute to classic sci-fi movies. Although this is true as far as the dive in a space-time tunnel is concerning, quoting the Star Trek and Star War sagas, we think that most of details in the tale are an humorous tribute to Paperino e il razzo interplanetario. The space-ship travel among the asteroid belt and the encounter with a family of precious mineral digger match the corresponding sequences by Luciano Bottaro.
The parodistic side of the tribute is not only in the personality and aspect of the aliens, but also in minor characters, as the chichen, mistaken for the chief of ducks, owing to a red crest which recall the Rebo crest. The interrogation of the chicken in the last cartoon is quoting the same probing of Donal Duck by Juppiter officers.
While these points are in the realm of the 'classical sci-fi physics', Rosa adds an additional concept to his Extraordinary Physics, to be discussed later in deeper insight, to explain the operation of the antigravity device: it cancels the inertia, so that the sudden hit on the Moon does not destroy the asteroid and the bin on it. Besides recalling these amazing points, we cannot forget that in Don Rosa's drawings there is a astonishing anticipation of the dynamics of the dramatic events of 9/11.

Teletransport
Again this tale starts with a citation of Carl Barks'Stranger Than Fiction, using a magic platten by Magica de Spell instead of a device realized by Gyro Gearloose, shown in top of the figures below.

The accident which blocked Donald Duck in the middle of teletransport, with potentially dramatic epilogue in Barks' tale, here becomes just the limited clearance of the platten allowing some of the most esilarating spatially-splitted gag, when Donald Duck or Uncle Scrooge counteract Magica de Spell, or when the platten takes off pushed by Gennarino's wings.
Gravity distortion
Cancellation of the gravitational force is a long favorite experiment of sci-fi writers, but as far as in our knowledge, nobody considered the case of gravity force acting in the horizontal direction.
"Gravitus Horizontus" is the magic spell used by Magica de Spell in A Matter Of Some Gravity. She learned it in a magicians' meeting in Lucca (probably referring to Lucca Comics): the spell cause a temporary modification in gravity's arrow against people affected by the spell. In this case Donald and Scrooge experiment a horizontal gravity, toward the walls of the money bin.
Don Rosa doesn't specify, from time to time, if there is a new center of gravity, so that walls, palaces, mountains attracted Donald and Scrooge with a horizontal force.
More likely it is the terrestial gravity which acts again, after a local rotation of the versus of the force, as suggested by Donald Duck's quotation while the two ducks are in Scrooge's office:
This furniture only looks like it's nailed down! I'm too heavy for it!
Later Donald's nephews exploit the effect to give chase to the witch:
We can steer our wagon at high speeds if you pull it with your weight!
The explanation is simple: the motion of the cart is horizontal, as the force acting on the ducks. So the nephews attack the uncles to the cart, and the two ducks "jump" across the building corner in the right direction. The cart is pushed in that direction by a horizontal force equals to the weight of the two ducks, with a resulting acceleration $a = g/2$, if nephews and cart total mass is equal to uncles total mass, or even larger if the two ducks are more heavy than the load they drag.
Another interesting point is crossing lake by our heroes. Scrooge jump in the water, suck that to stop their horizontal fall using the friction of the water, just as a spaceship speed is slowed down entering the atmosphere from an orbital flight.
At last Magica is reached at the airport, so the witch strikes again: "Gravitus opponere!" After that spell the gravity arrow points upward so the ducks are driven away from Earth, but the nephews climb up the uncles' feet together with a fire estinguisher. In such way the total mass of nephews and estinguisher equals uncles' mass, balancing the upward and downward forces. When nephews open the estingusher, the jet stream pushes them into the sky, so a "jet-propelled duck group" approach the aircraft stolen at airport by Magica and get the possibility of overcomind the witch in the final fight.
The most intriguing point for a physicist is that the spell is a parity violating interaction, i.e. the effect does not show specular symmetry: the ducks can go down the steps because they are pushed rightward the step vertical side, moving from upper right to lower left. This would not happen if they had to climb down moving from upper left to lower right. Luckly the airport is in the right direction.
It is worthwhile noting that Don Rosa was aware of this point, and later he exploited it in a gag: the ducks are supported by the windshield in one way, and flight away toward the back window when the bus u-turns at the airport bus stop.
Time freezing
Another important physical concept exploited in uncommon way by Don Rosa in On stolen time is time dilation, in the extreme case of time freezing; the time dilation in reference system moving each other with very high velocity, non negligible with respect to light speed, is a surprising, but well established effect predicted by Einstein Special Relativity.
In the Don Rosa's tale the Beagle Boys, using a new invention of Gyro Gearlouse, start to empty, little by little, the money bin. The invention is a time-stopping device, that can freeze time elapsing. When the clock is active, all thing and people are stopped, except people with clock or those who are within 10 meters radius. In this way everything who is in the range of the clock can move, else it's immovable.
The effect resemble very closely what would be the feeling of the twins in the well known Twin paradox: the time for that who travelled at nearly light speed was slowed, and when he meets again the twin which was at rest, find him much older then himself, or he could even find him disappeared, if tile lenghtening was extreme. So the time relationship between the inner and outer volume of influence of the time stopping clock is the same between two reference systems in extreme relative motion. A consequence one would expect is that the objects which time is slowed down appear to have become extremely massive (i.e. very heavy, in common term). Don Rosa created a few gags applying this relativistic effect.
We can try to explain it using the following definition of the force $F$: $F = \frac{\text{d} p}{\text{d} t} = \frac{\text{d} mv}{\text{d} t}$ where $p$ is the impulse, $m$ the mass, $v$ the velocity.
If time is stopped, $\text{d}t \rightarrow 0$, but people (or objects) can be in motion in their reference frame farther than 10 meters, any velocity change when hitted, causes $\text{d}v \neq 0$, so the force diverges or is very big, resembling an impulsive force like that affecting a ball bouncing on the ground.
Consequently, for example, Donald bumps against a butterfly stopped by the clock like against a wall:
You ran smack into a low-flying butterfly! Watch out for stuff like that in frozen-time
And we must pay attention the next time when Gyro invented a new stopping-time device!