Plan Nine From Inner Space: The Core

Steven Dutch, Natural and Applied Sciences, University of Wisconsin - Green Bay
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Hot Babe Scientist. Linus Pauling never looked like this. Hollywood is now capable of dealing with a woman scientist. Someday they will be capable of portraying a plain, middle-aged or overweight woman scientist.


Hunk Scientist. Linus Pauling never looked like this, either. Stephen Hawking may be a great heroic role model, but good looks sell tickets.


High Caloric-Intake Monster. Large animals eat a smaller fraction of their body weight each day than small ones, a manifestation of surface to volume ratio. Hollywood critters, on the other hand, eat like shrews.


Pompous Ass who Pays With His Life. The pig-headed boss or political figure who refuses for selfish reasons to listen to warnings and gets killed. Occasionally it really happens; the governor of Martinique refused to evacuate when Mont Pelee began erupting 1902, and died in the resulting catastrophe. So did 30,000 innocent people.


Superfluous Kids. Kids (generally repugnant) who serve no real dramatic purpose except to generate audience sympathy. I root for the monsters, especially when the kids do something stupid after they've been told not to.


Cookie Crumbs Have No Calories. And large objects (like asteroids) cease to exist once they're broken up.


No Other Scientists in the World. Apart from the two or three characters in the film, nobody else in the entire worldwide scientific community is aware anything unusual is going on. Nobody else seems to be aware of the huge tidal waves, plagues of locusts and frogs, rain of blood, global slaughter of first-born, etc.

The Core (HBS, Hunk, PAPWL, NOSW)

Rarely does a capsule summary of a film say as much as Roger Ebert's: He describes the film as "sillier than it sounds" but only "a step below Congo, Anaconda, Tomb Raider, and other guilty pleasures." Sillier than it sounds? A step below Anaconda?

Although I couldn't resist the cheap shot in the title of this page, I actually enjoyed this film more than I thought, in large part because the film doesn't take itself too seriously. For example, when a scientist says it would take ten years to make his earth-boring machine operational, a general asks what it would take to do the job in three months. "Fifty billion dollars." "Will you take a check?"

Boston: 32 civilians suddenly drop dead in their tracks, all wearing pacemakers. London: flocks of pigeons become disoriented and slam into buildings and people. A hot-shot geophysicist, Josh Keyes (Aaron Eckhart) suspects disturbances of the earth's magnetic field and puts his graduate students to work searching for other anomalies. Of course, nobody at Harvard or M.I.T. actually has instruments monitoring the earth's magnetic field when the pacemaker owners are zapped.

The Space Shuttle Endeavor, returning from space, suddenly turns up far off course and headed for impact in Los Angeles. When the crew first sees the ground, the Channel Islands are dead ahead, making me wonder why they didn't try for a water landing rather than endangering people on the ground. At the last moment, the hot shot female co-pilot, Major Beck Childs (Hilary Swank) comes up with a plan: land in the Los Angeles River, which is a concrete channel.

Our hot-shot geophysicist hands his theory that the earth's magnetic field is breaking down over to Dr. Conrad Zimsky (Stanley Tucci), the World's Leading Geophysicist  who, it turns out, is already aware of a problem. He invites Keyes to Washington, where they brief the military on the threat. The problem with making sci-fi movies for audiences with the scientific literacy of doorknobs is that all the expository material has to be at that level. Thus we get to see a briefing to the highest leadership of the military (all of whom certainly have graduate degrees) that sounds like a third grade lesson plan dumbed down. The bottom line is that the earth's core has stopped rotating, which in turn will lead to the loss of the earth's magnetic field and its radiation shielding ("the magnetic field is our friend," the brass is told). Within three months "we're back to the stone age" as all electronics are fried, within a year, the human race is dead from radiation. Meanwhile, there will be super electric storms and deadly bursts of microwave radiation.

Well, every million years or so the earth's magnetic field changes direction, which means that in the interim the field either disappears or at the very least becomes very chaotic, yet there are no correlations between magnetic field changes and extinctions. If all electronics were to be fried, that would indeed plunge the world into chaos, but we could reconstruct the technology of 1940, or 1900, easily enough, neither of which were exactly Stone Age. The magnetic field does indeed divert charged particles, but most of them are funneled into the earth's polar regions, creating auroras and electromagnetic disturbances, but not exactly bathing Iceland or Alaska in lethal radiation. And microwaves are not affected at all by the earth's magnetic field.

The participants of the briefing emerge to see the night sky shimmering with strange lights. "High-level static discharges," mutters Keyes, apparently never having been introduced to the aurora borealis during his geophysics training. Nor, apparently, are there any other scientists struck by the sudden onslaught of auroral activity at low latitudes. What are they all doing, studying to be on Weakest Link?

Hang Up Your Disbelief

If you're going to watch Star Trek, you have to accept that there are ways of traveling faster than light. If you're going to watch The Core, you have to accept that there is a way to travel to the earth's core. During the briefing, Zimsky muses that there might be a way to get there after all. Seems he has an ex-colleague, Ed Brazzelton (Delroy Lindo: he's ex because Zimsky stole his research) living as a hermit in the Utah desert and working on tunneling machines. I always wonder about hermit scientists. First of all, you have to buy groceries. Then you have to buy an abandoned military base, and even if you get it cheap, you have to pay property taxes on it. Then they always have huge amounts of exotic equipment. Where do they get the money for this stuff? Does the National Science Foundation have some kind of Hermit Scientist program?

Brazzleton has two key ingredients for a core-borer. First he has a serious kick-butt laser array that bores holes in rock like soft butter. Second he has a miracle alloy whose full name is "37 syllables long" but which he nicknames "unobtanium." This stuff actually gets stronger with increasing temperature and pressure and, amazingly, also turns heat into energy. At this point there is no point in even attempting to complain about violating the Second Law of Thermodynamics.

Project Deep Earth

So Project Deep Earth gets under way. The crew consists of Keyes, Zimsky, Brazzleton and a French colleague of Keyes, Serge Leveque (Tchky Karyo). The pilots are the pilot and co-pilot of the crashed space shuttle, who were expecting to be cashiered but who were instead commended for their resourcefulness and given command of this expedition. Rounding out the ensemble is Rat (D.J. Qualls), a world-class computer hacker who is given the task of keeping the impending disaster secret by suppressing all chatter about it from the Internet. Either that or go to prison for hacking. This plan will work because nobody will talk about these events on the phone, see them on the news, or spread rumors word of mouth. And of course the Internet is totally free of conspiracy believers who might become suspicious if certain types of pages keep disappearing.

At critical moments, the hush-hush nature of what's going on is underlined by closeups of folders marked "Secret." Sorry to disillusion anyone (not really), but Secret is not all that impressive in the military. Routine military exercises are typically classified Secret. Top Secret is where it's at, and really important stuff is classified at levels above Top Secret. By the way, the cover sheets themselves are unclassified. Makes sense. If the cover sheets were classified, you couldn't know you were in danger of violating security without actually doing it.

Major Childs is itching to be a commander, but the pilot Commander Iverson (Bruce Greenwood) tells her she's not ready. She's too used to winning, he says, and you can't really lead until you know what it's like to lose. So we know this guy is toast. I wonder why he even packed for the trip. He's so temporary the film doesn't even attempt to give him a personality.


The ship is the ultimate subway train, built in six modules connected together. It can flex, but more importantly, damaged modules can be jettisoned. I wondered how they knew that only the rearmost module might take damage, and what might happen if, oh, the second module had a hull breach. The ship is launched (dropped) into the Marianas Trench, a site picked by Zimsky for having thin crust. In a nice scene, whales, attracted by the ship's sonic emissions, follow it down. But alas, the Marianas Trench is seismically active, and an undersea earthquake creates tension before the ship's lasers fire in the nick of time and the ship starts melting its way through the mantle.

If you want to get into the earth this way, seems to me you'd want to go in where rocks were already hot and soft. Say, a rising mantle plume like Hawaii. Or maybe a mid-ocean ridge. But not a trench, where you have cool rigid crust and upper mantle to penetrate. Oh well, guess that's why I'm not the World's Leading Geophysicist.

The trip down is at a nice leisurely 60 miles an hour. I wondered how they would show any outside views, but we learn enough about the ship's imaging systems to make it at least semi-believable. But there are other things not so believable. For one thing, they have communications. The movie never even attempts to explain this. Extremely low frequency (ELF) radiation can penetrate the deep earth, but it's slow as molasses. Submarines that use it to communicate can transmit and receive about a character a minute. Typically they use short coded messages as signals to surface so they can transmit conventionally. So how the ship gets voice and even video to and from the surface is a deep mystery.

A Killer Electric Bill

Worst of all is the energy problem. It takes about 400,000 joules to melt a kilogram of rock. The ship is about five meters in diameter, so let's say it has a cross-section of 20 square meters. It has to get through the mantle, a trip of about 3,000 kilometers, meaning a total of 60,000,000 cubic meters of rock to melt. Mantle rocks weigh about 3300 kilograms per cubic meter, meaning the ship has to melt 200 billion kilograms of rock. So it will take 8x1016 joules to melt to the core. You may not be familiar with a joule (lifting a pound one foot requires a bit more than one joule) but you know what a watt is. A watt is one joule per second. It will take a bit over 24 hours to reach the core, or close to 100,000 seconds, so our total emission of 8x1016 joules in 100,000 seconds works out to 8x1011 or 800 billion watts. That's one heck of a laser system. Now heavy duty house wiring for a stove or heater running 1000 watts has to be pretty thick. Let's assume you can carry 1000 watts for every square millimeter of wire. That means 800 billion watts needs 800 million square millimeters of wire or about 800 square meters, or about 40 times the cross-section of the ship. I wonder who inspected the wiring.

Could the reactor handle the power demands? Well, if we could convert matter totally into energy, we could get that 8x1016 joules out of less than a kilogram of matter. This is Einstein's famous E = mc2, and once you get over being freaked out by the name Einstein, it's middle school math. The quantity m is mass in kilograms, c is speed of light in meters per second (3x108 meters per second) and E is in joules. On the other hand, nuclear reactions only convert a tiny amount of matter into energy. The fact that a typical commercial nuclear power plant is in the few hundred megawatt range doesn't inspire confidence. A kilogram of nuclear fuel can yield about 8x1012 joules of energy, so we only need about 100,000 kilograms of nuclear fuel, or about 100 tons. Then there's the shielding, the coolant, the power generators, etc, as well as wires with 800 square meters of cross section to carry the power.

One other point to put the energy demands in perspective. 800 billion joules (one second's worth of energy output) is about 1/6 of a kiloton. The reactor is cranking out the equivalent of a Hiroshima explosion every two minutes. Wonder what they're using for control rods.

Wouldn't it get easier to melt rock as we go down and it gets hotter? Rocks deep in the mantle are far hotter than their surface melting temperature, but they are still solid. Liquids take up more space than solids, and pressure tends to inhibit melting. Ice is an exception precisely because it takes up more space in the solid form than the liquid form, and pressure favors the melting of ice. But to melt deep mantle rocks, you'd need to supply enough energy to get the atoms to break apart and overcome millions of atmospheres of pressure. So bottom line, probably not enough to make the energy demands even remotely plausible.

Oh, one more thing. These calculations have been just for getting to the core. Double everything to get back.

Staying Cool

Speaking of heat, this ship has one humungous cooling issue, which is solved, we hear repeatedly, by "liquid nitrogen." I don't even want to think how much liquid nitrogen it would take to stave off temperatures of 5000 Centigrade. Also, consider this. If the ship's power system is 99 per cent efficient, those 800 billion watts that it's cranking out will radiate 8 billion watts of waste heat inside the ship. If you think I overestimated the wire needs, consider that the thinner the wire, the more resistance and the more heat.

Energy is proportional to temperature raised to the fourth power, where temperature is measured in degrees above absolute zero (the Kelvin scale). The core, at 5000 degrees, is about 20 times as hot as the earth's surface (not counting atmospheric effects) so the energy striking the ship is about 160,000 times (20 to the fourth power) what sunlight supplies to the earth. The sun supplies 1400 joules per square meter per second (or 1400 watts per square meter) to the earth, so the core is supplying 160,000 times that to the ship, or about 2.25 billion watts per square meter. If the ship is five meters in diameter and 50 meters long, it has about 800 square meters of surface area and has to fend off 1.8 trillion watts of heat. This is in addition to the 800 billion watts the ship is using to melt rock. We need a pretty honkin' big air conditioner.

Things in the Mantle

700 miles down, the movie encounters the biggest plot hole: a hole. A cavity. "Impossible," cry the geophysicists, and I agree wholeheartedly. Maybe it has a "cobalt shell," they theorize. Cobalt, neutronium, pixie dust, ain't gonna happen. Not nohow, not no way. Pressures at depths beyond a few kilometers deep would crush cavities out of existence. Nevertheless, the ship plummets into the cavity, which turns out to be lined with stupendous crystals. Perfect hexagonal prisms with pyramids, the only kind of crystal special effects people have ever seen. "Amethyst," says one of the geophysicists. Amethyst is a form of quartz, and we're at depths where quartz is compressed into denser forms, plus you're not likely to find quartz in the silica-poor mantle. Then again, you're not likely to find huge cavities kilometers across in the deep mantle either, so why get upset about the mineralogy?

Alas, one of the crystals has jammed the laser array and has to be cut. The crew ventures outside, relieved to discover the suits can withstand the pressure. At least the writers realized there would be pressure - I half expected them to take their helmets off and start breathing oxygen. The ship, however, has punched a hole in the shell around the cavity, and chunks of rock and a river of lava start falling in. A chunk of rock obligingly slams into Commander Iverson's head, fatally injuring him before he even more fatally falls into the lava. So Major Childs gets her shot at command.

Just before the core, the ship encounters something it can't penetrate: diamonds hundreds of meters across. Oddly enough, this might just be possible, though I rather doubt any accumulations of carbon in the mantle ever get that big. Childs tries to avoid one but hits it a glancing blow, Titanic-style. The rear section takes a hull breach. Keyes and Leveque are back there calibrating the timers for the nukes, and Leveque is trapped while retrieving one of the timers. Childs proves she can Make The Tough Call by sealing off and jettisoning the section despite Keyes' impassioned screams to open the door.

Into the Core

The ship drives on and plunges into the core. Then it rapidly accelerates. Good news? The trip will go faster? No, bad news. They have overestimated the density of the core. It's less dense than they expected so the ship sinks faster. This unfortunately means the nuclear blast won't be able to get the core spinning. Zimsky, who has been a pompous ass from the git-go, begins demanding that they abort the mission and go home.

Now do they mean density, how much the core weighs per unit volume, or do they mean viscosity, how much resistance the core puts up against flow? There are a lot of things we don't know about the core, but density is not one of them. First of all, we know the mass of the earth and we know its moment of inertia, a quantity related to the earth's rotation. These two quantities require the mass within the earth to be distributed in a certain way. As a cross check, the velocities of seismic waves also depend on density. So how density varies in the earth is known to pretty good precision. Other things, like temperature or viscosity, are not known nearly so precisely. In the 1980's studies of high-pressure materials indicated the core was a couple of thousand degrees hotter than previously believed. Besides, we're to believe this mission was launched at a cost of $50 billion and nobody ever ran different scenarios to see what might happen if our estimates were off?

Gravity does interesting things deep in the earth. The gravitational pull of a surrounding external shell is zero, so in a uniform earth the pull of gravity would decrease linearly as you approached the center. In the real earth, as you dive deeper you approach the dense core. Gravity holds remarkably steady throughout the mantle, actually increasing a few per cent near the core-mantle boundary, then starts to drop fairly linearly. So at the inner core boundary the ship would be at less than half a g of gravity, something not considered in the movie.

The crew comes up with an alternate plan. Detonate the nukes sequentially so the shock waves reinforce each other. Unfortunately the nukes were made to be detonated as a single unit and don't have individual protective shells. Okay, so we put each nuke in a module of the ship and disconnect the modules. Unfortunately, the ship wasn't designed to disconnect intact modules, and the hydraulic control is in a part of the ship that will be seriously lethal once the control is disabled. Brazzleton volunteers, and Zimsky makes his peace with him just before the end.

Fun With Atoms

At the last moment, Keyes and Zimsky realize they have forgotten a key core parameter in their computer models and the last bomb in the series is too small. Zimsky gets pinned behind a nuke in a section about to be jettisoned, but Keyes pulls the fuel rods from the ship's reactor and places them next to the final bomb (ignoring the probably lethal radiation exposure from the reactor fuel) to give it a bit more oomph.

Frankly, I like this. The more messed up people's conception of nuclear weapons is, the less likely it is that someone will actually be able to build one at home and the safer we all will be. The Core, by that standard, comes close to deserving a Nobel Peace Prize. Without in any way providing any useful information, there are two sizable bloopers in the film's nuclear scenario. (Everything in the next two paragraphs is available in open U.S. Government literature and has been for decades.)

First, in order to set off a nuclear weapon, you have to get uranium or plutonium into a critical mass, a mass big enough to allow a chain reaction to fission a large part of the uranium or plutonium atoms. The problem is that by the time the reaction is well along, you have a nuclear explosion trying to blow the rest of the fissionable material apart. You have to get the fissionable material together and keep it together for a few microseconds. Just putting a bit more plutonium next to the bomb won't do anything except make the fallout a bit more radioactive.

Second, there's a reason why the world's nuclear arsenals top out at around 20, rather than 200, megatons. Anything over roughly a hundred kilotons requires fusion. The bomb gets its energy from fusing light hydrogen atoms. Guess that's why they call them "hydrogen bombs," right? Problem: in order to get the fusion started, you need temperatures and pressures normally found in the interior of the sun. Or in the middle of a nuclear explosion. So hydrogen bombs work by setting off a nuclear explosion which in turn triggers the fusion of hydrogen. So increasing the power of the initial nuclear explosion by adding more plutonium won't really have much effect. You might think that just adding more hydrogen would allow you to get as large an explosion as you like, but the problem is there's an atomic bomb going off right next door. Only a certain amount of hydrogen can undergo fusion before the bomb gets blown to smithereens, and the practical upper limit seems to be 20 megatons or so. The Soviet Union claimed to have tested a 50-megaton bomb in the 1960's, but there is good reason to doubt if a functional 200-megaton bomb is possible, even in theory.


As if to underscore the seriousness of the situation, a hole develops in the magnetic field over California, allowing those nasty microwaves to get through. A beam of microwaves hits the ocean full force, boiling water and killing the poor fishies, then the beam sweeps in over the Golden Gate Bridge. A hapless motorist with his arm out the window finds it instantly severely burned, but worse is to come. The microwaves heat the pavement, melting asphalt and tires. Electric currents induced in the bridge create huge electric arcs, then the cables, heated to incandescence, fail, and the span drops into the water. The beam sweeps on over San Francisco, leaving much of the city in flames. It's a dramatic illustration of what might happen if any of this were actually physically possible.

Now there are proposals to put huge solar electric generators in orbit and beam the power to earth as microwaves, and if the movie were about a solar generator whose microwave beam drifted off target, this would be a great scene. But the sun generates only a small amount of microwaves (at radio wavelengths, the earth far outshines the sun) and they pass through the earth's magnetic field and atmosphere unimpeded all the time.

Nevertheless, the commanding general (Richard Jenkins) decides the time has come to try another plan. Unconvinced that the crew can get the core spinning with their nuclear explosives, he orders Project Destiny activated. Turns out Zimsky was in on Destiny, a program for remote triggering of earthquakes, and there are dark hints that Destiny may have caused the core problem in the first place. Destiny stands for Deep Earth Seismic Triggering INItiation. The General orders the ship to return, but the crew refuses, whereupon he orders Destiny activated anyway, even though it will destroy the ship.

Say what? This ship is taking millions of atmospheres of pressure and temperatures approaching those on the surface of the sun, and is about to take shock waves from the largest explosions ever generated, and Destiny will destroy it? How? The hull gets stronger under pressure. Nevertheless, the crew is concerned that Destiny will set off chaotic instabilities in the core. Rat the hacker, whose function up till now has mostly been to watch global disaster reports on his monitor, sends a coded message to the crew, who advise him to stall Destiny. Apparently it has never occurred to the General that Rat might try anything unauthorized, but Rat begins hacking into Project Destiny, and for some reason his searches hit despite the fact that the acronym is actually DESTINI. Destiny (or DESTINI) uses a lot of power, and with the West Coast power grid out it takes most of the power east of the Rockies to make it work. This is a top secret program to generate devastating earthquakes untraceable by our enemies, who will never figure out there's a connection between their earthquake and much of North America having a brownout immediately beforehand. In the nick of time, Rat shuts down Destiny.

Happy Ending

The nukes go off, the plan works, the core starts spinning again. Jubilation in Mission Control. Unfortunately the ship, with its reactor fuel gone, is dead in the water, or molten iron. Aha, exults Keyes, unobtanium converts heat into energy! They hook the wiring to the hull and power up. But they don't have enough for lasers. Instead, they follow rising magma streams upward, eventually coming out of a submarine volcano off Hawaii. Now they really are dead in the water with no way to communicate. The Navy has a rough idea where they are but all they can pick up on the sonar are whales. Rat realizes the whales are responding to signals from the ship and the two survivors (Keyes and Childs, in case you've been keeping count) are rescued.

The movie ends with Rat blowing the lid off the Government's attempt to keep the project secret.


The August 2003 issue of Scientific American (p. 24) describes a semi-serious attempt to design a probe capable of reaching the earth's core. Serious, in that the scientists seriously attempt to come up with a physically possible way to do it, semi in the sense that the physical demands are enormous and some of the technology is still out of reach. The plan involves melting several million tons of iron, which would sink down through the mantle because of its high density. That part we can do. 

It's designing a probe to survive the temperatures and pressures that's the hard part. Diamond could probably stand it, but what would you use for electronics? Solid state electronics depend on keeping electrons and impurity atoms in semiconductors in precise configurations, and heat is deadly. Anyone who's ever fried a motherboard because they blocked the heat vents on a computer can testify to that. Solid state electronics can barely tolerate the boiling point of water, let alone the melting point of iron. 

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Created 21 January, 2003,  Last Update 05 April, 2011

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