A.I. sets out to explore the big issues like the nature of love, the meaning of being human, and the foibles of trying to satisfy human needs with technology. Unfortunately, it stumbles on pesky little details like the laws of physics and effective storytelling style.

There's a thin boundary between science fiction and science farce. Science fiction relies on science that may be highly speculative but is, at least, conceivable. It becomes science farce when its plot rests on imaginary science which is clearly contrary to longstanding scientific principles in areas where they're known to be true. A.I. seems to be science fiction yet staggers dangerously over the boundary during its opening narration.

Greenhouse gasses have warmed Earth, causing ice caps to melt and flood major cities in coastal areas. As a result, populations have been displaced and "hundreds of millions" in poor nations have starved. So far it's science fiction. Greenhouse gasses could cause ice-cap melting, although it would take a much longer time than implied by the movie.

If only the North Pole melted there would be no flooding. The northern ice cap floats like a giant ice cube. The volume of water it displaces as floating ice exactly equals the volume it would occupy when melted. Antarctica is another story. Here the ice is several miles deep on top of a continent. Melt it and it would flow off the land into the ocean, causing the ocean to rise.

The narrator stumbles into the realm of science farce when he says that prosperous nations sustain their prosperity to a large extent by creating the perfect low-cost labor force: robots. According to the narrator, these robots require no resources beyond those used to create them. In other words, we're asked to believe that the robots never need to be recharged, refueled, or rebuilt. They are essentially perpetual motion machines which break the first and second laws of thermodynamics. If this actually happened it would shake the very foundations of physics.

Okay, a movie can still be a masterwork and break an occasional law of physics. Although we hate to admit it, sometimes there are good artistic reasons to defy a law of physics. Great artists have often been defiant. Edouard Manet and René Magritte are both famous for creating paintings which look realistic but use impossible physics. Manet did it to provoke the French Academy. His painting Le Bar aux Folies-Bergère [The Bar at the Folies-Bergère] deliberately shows an impossible reflection of a young woman in a mirror. Magritte did it as a type of visual joke or riddle. His painting L'Empire des Lumieres [The Domain of Lights] shows a night scene occurring during the day. However, there's a big difference between insightful or clever rule-breaking and the clumsiness of an amateur who can't get perspective, proportions, and the overall physics of vision right.

Movies must seem believable to be taken seriously. A movie which represents itself as serious science fiction puts its believability at risk when it trips over a major principle of physics. It can recover, however A.I. does not. It gets worse. Toward its end the movie seems to abandon even the pretense of serious science fiction and takes on a new storytelling style: pure fantasy.

There's an old axiom in fiction writing which says it's okay to ask a reader to believe the impossible but not the improbable. For example, it's okay to say that a maniac has activated an antimatter bomb in the wall safe, but it's not okay to say that someone miraculously guessed the right combination on the first try. A.I. asks us to do both.

Following a particularly depressing scene, the main character, a robot boy, casts himself into the sea in the middle of what was once Manhattan. Fortunately, a robot friend is watching and pilots a helicopter which miraculously turns into a submarine and dives under the water to rescue the robot boy.

Needless to say, design parameters for helicopters are almost complete opposites of design parameters for submarines. Helicopters require light-weight construction to be able to fly. Subs need heavy-weight construction to sink and resist pressure. Helicopters rise using complex aerodynamic principles, while subs rise primarily using Archimedes' principle. Helicopters use air-breathing engines. Subs use electric motors. Subs must resist extreme external pressure differentials—at least 10 atmospheres greater than the pressure inside (generally more)—while helicopters must withstand only modest internal pressure differentials—less than 1 atmosphere greater than the external pressure—if any pressure differential at all.

The difference between internal and external pressure differentials is a major design issue in itself. Soda pop bottles can resist around 5 atmospheres of internal pressure differential. Yet, an empty soda bottle can be crushed with light external finger pressure thanks to a nasty little detail called elastic instability. It takes far more wall thickness and/or material strength to protect against an external pressure differential than the same internal pressure differential.

In theory, a mechanism could be designed to equalize pressure on both sides of a sub's walls by altering the internal air pressure as the sub changed depths. Since a sub can go up and down rapidly, this would require a large air supply with high flow rates. When the sub ascended, it would have to expel large quantities of air. People in the sub would also have to remember to exhale or risk having their lungs pop from overpressure. Such a system would add complexity and safety problems without any real weight advantage.

We could go on at length, but suffice it to say that designing a dual-purpose helicopter/submarine would be an engineering nightmare and is not likely to happen anytime in the foreseeable future.

After making the rescue, the robot friend is captured by the police, leaving the saltwater-soaked robot boy in the helicopter/submarine. A mouth full of spinach has previously caused the robot boy to have a serious malfunction, yet he is unaffected by saltwater. Apparently he has been programmed to keep his mouth shut during suicide attempts.

It seems like the loss of a friend would plunge the robot boy into an even deeper depression. But no, when he was drifting beneath the waves the robot boy just happened to see what he had desperately been seeking: the Blue Fairy from the Pinocchio tale. He hopes she can make him into a real boy so the human he considers his mother will love him.

With his trusty robotic teddy bear, the robot boy excitedly pilots the helicopter/submarine back to the ocean-floor home of the Blue Fairy. Unfortunately, after reaching its destination, the sub becomes hopelessly trapped.

In reality the Blue Fairy is a long-abandoned statue, but this does not stop the robot from begging it to make him a real boy. Not only is the statue free of slime, barnacles, and major deterioration but stays that way until discovered frozen in a thick layer of ice 2000 years later by skinny beings. These look a lot like animated versions of Alberto Giacometti sculptures.

Evidently we're supposed to believe that the Earth's axis has shifted and New York is now a polar ice cap. A simple ice age would have lowered ocean levels, but this evidently didn't happen before New York froze.

All of humanity is extinct and has been replaced by the skinny beings. Considering that the freezing of New York took only 2000 years it's not surprising that humanity was doomed.

During 2000 years of entrapment in the presence of the Blue Fairy the robot boy never figures out that the Blue Fairy is just a chunk of plaster. This is an awfully long time to be stuck in a loop. The robot boy is able to pilot a helicopter/submarine without training and is supposedly capable of the highest human characteristic: love, yet is totally lacking in common characteristics like panic, doubt, or even boredom.

When the skinny beings find the submarine, it's in perfect shape without so much as a leak. They pop open its canopy and the robot boy, along with his teddy bear, come to life just like before. After 2000 years at the bottom of the ocean, wearing saltwater-soaked clothing, the robot boy doesn't even need a change of clothes, let alone a change of batteries. The moviemakers clearly weren't kidding when they asked us to believe that robots were perpetual motion machines.

The movie continues in this bittersweet fairy-tale mode until the end. The bitterness comes from a periodic injection of reality. The syrup is created by inventing scientific principles out of thin air and totally ignoring probability.

From the standpoint of moviemaking technology and special effects, A.I. is a marvel. Undoubtedly some viewers will also find deep meaning and heartfelt emotion in it. One senses that the moviemakers were indeed sincere. It could have degenerated into a pure action piece designed to boost box-office returns, as is the case with many science-influenced movies. A.I. deserves far more respect. Sadly, however, like the robot boy it depicts, A.I. seems unable to rise above the condition of being merely an amazing work of technology.