Physics and Star Wars

Physicists are anxious for a Star Wars film to explain some of the key physics elements that hold the story together. A few of the advances in physics could produce a few of the capabilities shown in the movie. Other effects or devices show some serious neglect of physics effects, or severe overkill.

The “Force”

First, we should deal with the “Force”. Does or can it exist? How would I know, and it doesn’t really matter. Almost all of the occurrences of the force are very local in effect and around just a few people. Sticking out your hand and regaining your light saber from a few feet away could be rendered moot by a single backup warrior, or by a simple wrist strap. I have a wrist strap on my ceramic ocarina, in case I were to drop it on concrete. The old Darth Vader choking someone a few feet away could by done by anybody by taking a few extra steps. Sensing the death of a planet by the force could be done with good communication. Guiding the X-wing fighter bomb by the force could be replaced by upgrading fighter guidance systems between movies, which would be available to all pilots. Extracting a brain readout is commonly done by truth-telling drugs. If only a handful of people use the force in very local ways, it would be relatively hard for any person to know about this. Physicists label their forces, of which we have four fundamental ones, and it about time that Star Wars labeled theirs, before someone like me labels it “the fairly useless Force”. It pales in comparison to Marvels’ characters powers.

Destroying a Planet by Ozone Depletion

Next, we come to the key suspense device of destroying a planet. I started thinking of what was the minimum energy way to destroy a planet. Actually, what they want to do is destroy life on a planet. That in itself is extreme overkill, since what they really want to do is wipe out a small rebel base. The easy solution comes from an earlier film where they use drones, something that we now are successful with. To destroy life on a planet, we already almost managed this ourselves without knowing about it. Simply by using spray cans with chlorofluorocarbons, we injected chlorine into the ozone layer, which acted like a catalyst to destroying ozone. That would have left us subject to ultraviolet solar radiation, that would give everyone skin cancer. F. Sherwood Rowland and Mario Molina at UC Irvine won the 1995 Nobel Prize in Chemistry for discovering this. Amazingly, the chemical companies producing these chemicals tried to discredit this research and continue the production and use of chloroflourocarbons.

The Starkiller

The new planet destroying weapon, the starkiller, uses all the heat and energy in a star. They captured this in a single planet. Since a planet has only a smidgen of the mass of the star, putting all of that energy into the starkiller planet would essentially melt and evaporate it, before it could be used as a weapon. Even with magnetic confinement of the plasma, the heat from the plasma cannot be confined, and would evaporate the starkiller. I understand that the starkiller fired through hyperspace, or else the explosion of a nearby target planet would wipe it out. If the starkiller absorbed all of the mass of the nearby sun, that gravity of that mass would pancake any structure and people on the star killer. Finally, when the absorbed energy of the star is all shot at the target planet, the recoil would send the starkiller recoiling off into space, and the sudden acceleration would cause a shock wave on the starkiller, which would blow it apart. Overkill destroys the destroyer. With today’s technology, that can all be replaced by a drone regiment in the first place. Only a set of Senate committees completely led by science deniers could have approved such an unscientific and immensely expensive weapon. We have already reached that stage today.

Pressure Problems Inside a Starkiller

Since the full structure of the starkiller is not clear, we can only mention some pressure problems that would have to be dealt with. Hollowing a cylinder inside a planet would have to support the self attraction of the remaining mass of the planet, or its weight. Absorbing a larger star inside a smaller planet would require compressing the star’s plasma, which would increase its pressure, density, and temperature. These increases would increase the rate of fusion to generate a yet higher temperature and increase the radiation that would melt the starkiller. Even though magnetic confinement would contain the plasma, the magnetic fields would be supplying the confining pressure, and transmit that to the magnets providing the magnetic fields. The magnets would then press outward, and need to be confined by strong structures. In superconducting magnets on earth, that is supplied by surrounding steel and concrete. Finally, I don’t see how a fired plasma beam would be guided into hyperspace, and would know where to emerge from it to destroy a planet.


The key to Star Wars and any other interplanetary or galactic science fiction is almost instantaneous transport to any other part of the Galaxy. Stars orbit around the Galaxy at speeds of a few hundred kilometers per second. Even if you could almost instantaneously move across the Galaxy, you would arrive at your destination with a relative speed hundreds of km/sec out of sync with the target planet’s velocity, crossing it in a few seconds. Deceleration or acceleration to a synchronous velocity would require enormous g forces that would crush passengers and starships. There would also probably be a large time dilation and lack of time simultaneity between the start and end points, so you would arrive far before the threat, or far after the threat. The only mechanism being considered for such galactic travel is going into a black hole and emerging out of another one, via a wormhole, if possible. Of course, tidal forces crush anything going into or out of a black hole. Also, you could only arrive where the wormhole happens to lead to.  Actually, the isolation from intergalactic invaders that the universe requires, is the best defense that our civilization has. If you want conflict stories with threats to our civilization, just look at nuclear weapons on our own planet.

Energy and Anti-gravity Ships

One of the major advanced technologies in Star Wars is the anti-gravity used from star ships to desert scooters. Of course, deserts can easily be crossed in SUVs without such technology. Also, in many cases, the star ships could often land in many places. Now for the physics. If an object is on a frictionless table top, it can be moved across it without expending energy. If it was supported by an effective anti-gravity device such as electromagnetic suspension, or magnetic levitation, movement along a track or surface of suspension would not require energy. Of course, the various places a starship would hover over wouldn’t usually have such a magnetic surface, so they must use a different technology. It would, however, require energy to escape from a planet, equal to the gravitational potential energy it lost when landing on the planet from very far outside the planet. It is conceivable that the starship with its anti-gravity would have an analog of regenerative breaking, where it can store the energy that would normally accelerate an object falling to the earth’s surface. It would then have the energy to escape from the planet again.

Suspension of Anti-gravity Ships

If you put an object on a surface under the force of gravity, it compresses the surface until the restoring force balances the weight or gravitational force on the object. If the object is an ordinary ship, and the surface is water, enough water is displaced so that the greater pressure provides enough force on the bottom of the ship to counteract the force of gravity. A suspended starship would have to compress any surface it is over, or if over water, displace enough water to absorb the pressure of the anti-gravity suspension field and counterbalance the force of gravity on the starship. When the ship moves across the surface, the displaced water must move across the surface, and would provide the same drag as a boat of the shape of the displaced water. This would chew up energy, just like an ordinary boat. Similarly, a depression of a surface moving along a surface from an object resting upon it dissipates energy which is the same as that due to sliding friction of a non-suspended object.

The Massive Structure and Spaces of Starships

The motors of the star ships appear to propel the ships by ejecting matter, so why do star ships appear to be so spacious and built of heavy, thick metal, without lightweight cross members for structure. The halls are always empty except for storm troopers chasing the heroes. Compare this to our space shuttle or command modules or space station where every space is cramped and serves many purposes. When accelerating to hyper speed, why aren’t structures and people crushed by very high g forces?

Mass of Fuel for Energy:  Chemical, Fission, and Fusion 

The most efficient energy source which we can realize now is ion acceleration. Batteries, or chemical fuel burning, only generate a few electron volts per atom. Nuclear processes yield a few Million electron volts (MeV) per atom. Fission requires the heaviest elements such as uranium, to get a few particles out. Fusion gives a few MeV per light nucleus such as Helium 4. If the tri-alpha process, developed by the late UCI Professor Norman Rostoker, works, the energy comes out in already charged He 4 nuclei (alpha particles). Energy can be captured from these to accelerate some of them further or to accelerate protons from hydrogen, and be ejected for thrust. This allows the star destroyers to go furthest with the minimum weight being carried for ejectable fuel.

Matter-Antimatter Annihilation for Energy and Propulsion

To get the most bang out of fuel, use matter-anti-matter annihilation. Chemical fuels give about one billionth of the available mc^2 of fuel to energy, fission about one part in ten thousand, and fusion about one part in a hundred. Matter-anti-matter annihilation can give at least half the full E=mc^2 to acceleration. The first applications of this were considered to be creating positrons in a low energy electron accelerator at a fuel base, storing them aboard, and then annihilating them with electrons. However, with an accelerator of several GeV, you can make anti-protons and store them. For the same single electronic charge of one unit they have 2,000 times the mc^2 of a positron, and 2,000 times the mass so they can be confined much easier. Electron-positron annihilation into two photons can be visualized in the case that one photon flies out the rear of the ship, and the other is absorbed by the ship giving the full momentum p = E/c to the ship, where E = (mass of electron) x c^2. This is the maximum possible conversion of energy into momentum for thrust. The absorbed photon converts to heat, which can run the ship or power an ion accelerator (combined cycle annihilation process).
Proton-antiproton annihilation makes pions. Neutral pions decay into two photons with the same maximum thrust. Charged pions decay to muon and neutrino. The neutrinos are unstopped but statistically balanced to give no net thrust. Statistically, half the muons are absorbed to give thrust, and also heat to again be used for ship power or running an ion accelerator. The muons decay to electrons and neutrinos, where again the neutrino energy and momentum is lost.

Laser Disruption Shields

The shield system may actually be possible. The most energy effective way to use light as a weapon to cut or evaporate an object is to use coherent laser light to vastly increase the in phase electromagnetic field to break electron bonds and eject electrons, weakening a solid. If a defensive light or magnetic or electromagnetic field is set at the laser frequency but with random fields, that could ruin the coherence of the laser light, and make it relatively useless.  Of course a well polished metal surface of a starship would be a good backup choice.

Plasma Sabers

The light saber has difficulties, as a light beam doesn’t cut off after a few feet. However, a plasma field might be shaped and confined by a magnetic field, conserving energy. This is similar to a plasma discharge, or electromagnetic discharge from power line connectors. That also makes a humming noise. If the discharge just goes out, as a current, it creates a solenoid shaped cylindrical magnet field about it that will confine it into a beam shape. The ringed magnetic field will bend back any plasma particles trying to escape the beam. By the way, plasma cutters are already available from Home Depot for around $500 dollars.

If the good guys use one charge for the ion beams and the bad guys the opposite charge ions, then when striking each other near alignment, the magnetic fields ringing around the beams would join between the beams and make a magnetic field of twice the magnitude and four times the energy density.  The fighters would have to expend a lot of energy and force to bring this about.  The plasma sabers would then repel each other as is seen in the battles.  Oppositely charged beams would also glow with different colors.

The plasma discharges generate ozone and maybe nitrous oxides, since all of the planets that they are breathing on contain oxygen. Used outside, the ozone disperses safely. What I have been leading up to is that people have been buying air cleansing ozone generators for their confined rooms. Air UCI has studied these and concluded that they are harmful, along with the judgement of consumer groups and the Air Resources Board.

The Lack of Cyber Security in Starships

One might also fault the cyber security of the starships. Even an ordinary droid that can only beep can hack into the starship at lightning speed. We have already reached this stage, where any business or government network doesn’t even encrypt their data. The other security fault was the control panel for the crucial shields is off in a poorly guarded hallway, and can be turned off by flipping a switch.

Star Wars Speculations

This of course leads to speculation of the origin of galactic conflict. My guess, is that it is the prolongation of the cyber and device split between Android Google systems and Apple iOS systems, which do their utmost to be as incompatible as possible. Add this to the Amazon distribution system. The first planets to be Flickred away were probably those ruled by Yahoo.

The fans have probably already figured out a meaning of the villain’s name of Kylo Ren. To me, it basically includes the word Kill, and to Rend apart. However, to a scientist, it pronounces close to “kilogram”, a hidden chide to our continued use of the complex British system of units (also called the Imperial units of the British Empire), as opposed to the very simple and universal metric system. On the other hands, if the far away galaxy has beings with six fingers on each hand, they are probably using the British system.

One impressive development is that any starship can be controlled without instruction, with presumably the same simple console as you learn just driving a desert scooter.

Another impressive development, is that nothing has to be recharged at night.  Perhaps they all run on Mr. Fusion modules.

Even without further technology enhancements in Star Wars, there is still much Physics to ponder over.

About Dennis SILVERMAN

I am a retired Professor of Physics and Astronomy at U C Irvine. For a decade I have been active in learning about energy and the environment, and in lecturing and attending classes at the Osher Lifelong Learning Institute (OLLI) at UC Irvine.
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