The Physics of the Death Star (Synopsis)

“What’s that star?
It’s the Death Star.
What does it do?
It does Death. It does Death, buddy. Get out of my way!” -
Eddie Izzard

It's said -- at least by Darth Vader -- that the power to destroy a planet is nothing compared to the power of the force. But how much energy is that, really?

Image credit: Lucasfilm / Star Wars: Episode IV, a New Hope. (Motion Picture) Image credit: Lucasfilm / Star Wars: Episode IV, a New Hope. (Motion Picture).

While it is, objectively a lot of energy, that kind of destruction really isn't so unfathomable, not if you're willing to consider the ultimate tool of destruction for physically practical purposes: antimatter.

Image credit: Lucasfilm / Star Wars: Episode IV, a New Hope. (Motion Picture). Image credit: Lucasfilm / Star Wars: Episode IV, a New Hope. (Motion Picture).

If that green beam isn't a laser, but is rather a beam of antimatter, you'll be surprised at how easy destroying a whole planet would be!


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If we were unlucky to have the antimatter presence, then we would not be conscious of the world of matter, but then, maybe, in a galaxy far, far away .........

I vaguely recall Kip Thorne saying that wormholes would be unstable because photons traveling through them, then back to the origin and through again (rinse, repeat) would instantly produce a massive build up of energy that would blow the wormhole apart. It's essentially using time travel to make one photon come through the hole N times "instantaneously" (from the outsider's perspective), where N is really large.

Now since the Star War denizens have some sort of FTL warp technology, maybe they could use this effect as a weapon. IOW, the Death Star could first produce a small wormhole near Alderaan, then pump/prime it with a more reasonably energetic laser.

No discussion of planet-killing would be complete without a link to "How to Destroy the Earth" at of course.

But comparing your numbers with theirs (point #6 on their page is antimatter bomb) and double-checking the calculations myself, I think you may be off, Ethan. They estimate 1.24 trillion TONNES of antimatter, which is 1.24 quadrillion (10^15) kilograms. Asking WolframAlpha to convert kilos to joules for me, that appears correct. (They up that by a factor of 20 assuming much of the energy output would not be available as destructive force, but we can set that aside for now.)
For reference:*10%5E15kg+in+joules

That whole space station, green laser thing is just for show. Darth Vader really destroys planets with the force. Gotta keep the admirals happy.

BenHead @3: Ugh, that's what you get when you do an extra conversion -- grams to kilograms -- that's totally unnecessary. Thanks for the catch; I fixed the text in the original article.

Still massively inefficient, compared to simply making the planets surface instantly unsuitable for life.

So less than one solar mass energy can undue the binding energy of a galaxy? Are you sure?
Hypernovas and GRBs release this magnitude of energy, but little of it goes towards kinetic energy of the galaxies components.

By Omega Centauri (not verified) on 18 Sep 2014 #permalink

I never really got the point of such a massive, and massively overcomplicated weapon. If you want to destroy a planet you simple toss a rock, a really big rock, at it and let the kinetic energy take care of the rest. No need to actually destroy the entire planet, sure it is impressive, but why? You are going to unbalance the entire solar system. Next thing you know planets in the same solar system, planets you might rather keep around, start running into each other. You could get a runaway planet that threatens all before it. Who knows where it might end up in a few thousand years?

Come to think of it, you might need, and the one really good use for a Death Star might be to clean up rogue planets.

Which brings up the cult classic movie "Dark Star". A story about a mission to blow up rogue or unstable planets, if they had no life on them, if said rogue planets threatened a habitable planet. To do the job they are give twenty sentient and enthusiastic mega-bombs termed "planetary triggers". For obvious reasons, the ship is programed to keep them from going home until all the triggers are expended.

The movie is a classic. A dark comedy and counterpoint to science fiction that posits a future of clean, well-lit, spacecraft with staid and professional crews. This crew is as broken and exhausted as their spacecraft but the only way home is to find the right conditions that will allow the use of the bombs and get the job done.

It is a story of humanity broken by the vastness of space. I highly recommend it.

Do you think that the speed of destruction is feasible? That's a lot of acceleration. How fast can a shock wave propogate through the earth?

In Greg Bear's book "The Forge of God" a similar anti-matter weapon is used but somehow they get a couple of capsules of super-dense matter/anti-matter (~100 million tons) to the centre of the earth where they combine and destruct. But the subsequent destruction of the earth takes 10s of minutes, not seconds. The forces of destruction take some time to propogate 6000 km through the earth.

By William T (not verified) on 18 Sep 2014 #permalink

William @8: Shock waves by definition travel at speeds faster than the speed of sound in the medium. It's when the shock wave has lost enough energy that it slows down and becomes an ordinary sound wave. I couldn't find an upper limit on the speed (except the speed of light, of course); if the antimatter explosion keeps pumping energy in, there's no reason it couldn't accelerate as fast as you wish.

As a practical upper bound, you could consider 10% lightspeed, which is the result speed of a supernova remnant according to Wikipedia.

You might need more than the minimal amount of antimatter to get it to move fast enough though. And that might be pretty dangerous for the Death Star in close orbit around the planet.

By Ross Presser (not verified) on 18 Sep 2014 #permalink

Yes, clarification on the 3 seconds would be much appreciated. I've seen these super nova simulations on youtube, the same must be possible here. And if it's a sphere of antimatter, annihilation would occur only on the surface, wouldn't that take time? If it is instead a ray of antimatter, should we think of it as a cylinder inside the target, with length about the diameter of the target - or would it form a cone or a ball when it hits the surface and travels into the core?

By Josef Nedstam (not verified) on 18 Sep 2014 #permalink

Second 13 into the video, it seems the length of the antimatter ray is about 10-20 times the diameter of the planet. Should also give us an estimate of the speed at which it travels, slightly less than 2 seconds, and with the death star at about moon distance the speed is around 50% of the speed of light. I'd say the death star would get a fair bit of recoil there too. If I haven't done any mistakes between meters and km, a rod 10 times the radius of earth with volume of AnneFrank would have an area about the size of a decent suburban plot, 860m2. Maybe the density of crystalline antimatter hydrogen is much different from that of an asteroid, and anyway it looks like it's a plasma when being fired. Oh, well, back to work...

By Josef Nedstam (not verified) on 18 Sep 2014 #permalink

If I recall correctly from the EU knowledge base (he said, sucking on his retainer), the Death Star is powered by "hypermatter", which...we don't really know what that means. But it's hyper. So, maybe the system output is some sort of ultradense plasma generated from the hypermatter reaction and confined/fired from some serious magnetic fields. Also, consider the size of the DS and just how *thick* that beam has to be. Kaboom.

I never really got the point of such a massive, and massively overcomplicated weapon.

Star Wars is a space opera. Over-the-top stereotypes of normal things is kind of a hallmark of the genre. You don't have an antagonist, you have a really evil villain. And you don't have a weapon, you have a super duper end-of-the-world weapon.

> So less than one solar mass energy can undue the binding energy of a galaxy? Are you sure?

I agree, this claim seems dubious. If an antimatter star crashed into a matter star it would produce 3.6x10^47 joules (2x10^30 * c^2 * 2) which is about 35 times as powerful as a big supernova. Add to this that most of the energy would radiate between the stars rather than hitting them, you wouldn't necessarily disrupt a galaxy by unleashing this amount of energy in it.

Geez people, I belive it was determined some time ago they were using a discombobulator ray. Catch up!

With today's technology everything you state seems infeasible but the stars wield are by no means the strongest forces in the universe. Consider the worries that were voiced over CERN creating a black hole. Could the Death Star not have also produced and stabilized such a force, then released it forcing the atoms to be smashed against each other and create a similar explosion? Little is our knowledge of science, we've only been using electricity for a few hundred years, imagine the known science of 10,000 years in the future. If we haven't already destroyed ourselves, the toys of today will be child's play.

All you really have to do is shield the planet from the incoming "mass effect" of the universe ( Mach's principle ) which holds it together. Everything inside the shield goes to the speed of light and weighs nothing. Then turn the beam off suddenly ( femtoseconds ), and the entire Universe smashes into the planet with very short impulse. I know why you are asking this question. You are testing to see if we understand that controlling that Higgs boson will create the last bomb. It will.

By john snakenburg (not verified) on 19 Sep 2014 #permalink

Try putting a peeled hard-boiled egg in a microwave.

Try Prince Rupert's drop.

Who knows for sure what the forces are that bind this planet together, and what its weak spots are?

By David Bennett (not verified) on 19 Sep 2014 #permalink

Back in the nineties, a physics graduate I knew -- in the context of discussing ideas for hypothetical computer games -- suggested that a spacecraft powered by antimatter would, when it needs to refuel, approach an antimatter planet, fire a quantity of matter at it, and collect chunks of antimatter ejected by the resultant annihilation.

Later, faceless people on Usenet told me -- with no doubt whatsoever and something of an incredulous tone -- that this was nonsense because in a matter-antimatter annihilation, NONE of the energy that results is converted into kinetic energy that might eject material adjacent to that which is annihilated.

I've never been entirely sure who was right.

By Adrian Morgan (not verified) on 19 Sep 2014 #permalink


Could that be the power source (size, weight)?

By Steven Belsky (not verified) on 20 Sep 2014 #permalink

Rather than go into a technical discussion about the Death Star, antimatter does seem like it would work, particularly as a weapon. Using it for power would be tricky and dangerous, but just slinging masses of it around to blow stuff up would be comparatively easy.

If antimatter were used, that would make the attacks seen in the movies, particularly "Return" suicide missions. If there was enough antimatter on them to blow up Alderaan with more to spare (according to source material the Death Star could fire several shots per day), The Death Star itself would be annihilated. At the very least the system would be filled with extremely high velocity Death Star bits, some of which might have hit the base in the original movie. Endor, and both fleets, certainly would have been toast from fragments, blast and radiation.

Do we use a lot of energy with internet and cell phones ? If yes how long do we have before we destroy ourselves in the process of inventions?

Obi Wan Kenobi: That’s no moon…it’s a giant plot device! OMG!
Han: It’s too big to be a plot device, like totally.
Luke: Fer sure, I have a very bad feeling about this.

The Death Star is powered by neither physics or the force, it runs entirely on Industrial Light and Magic, even says so in the credits.

Read the Cosmic War by Joseph P Farrell. There are other models that are much easier than anti-matter. There's also that strange asteroid belt exactly at the right spot between Mars and Jupiter. Then there's the crazy design of the Saturn moon Iapetus with its linear six mile high hill that goes all the way around the planet...and it death star look and feel. Gulp. What did George know and when did he know it...?

Assembling the amount of antimatter required to blow up a planet roughly the size of Earth ("What's an Earth?" Luke Skywalker asks) would be staggeringly challenging. If one actually wanted t blow up a planet, it would be more economical to trigger some sort of internal chain reaction.

Alternatively, if one merely wanted to wipe out all life on an Earth-sized planet, crashing an asteroid 10 or 20 miles wide into it would probably do the trick.

The gravitational binding energy is just what's required to get the fragments of the planet out of each others gravitational pull. Before you can even look at doing that, you have to break the planet into fragments. The chemical binding energy between the atoms of earth where you plan to open up massive fissures is not insignificant. But before you can do that you need to generate the energy by reacting the anti-matter with matter. That will result in the generation of huge amounts of gamma rays and neutrinos. The neutrinos and some of the EMR will fly off into space taking about 50-60% of the energy with them. Then the remaining gamma rays and other EMR will convert largely to heat (and the heat capacity of earth will absorb huge amounts of that). Not saying that the earth won't be totally uninhabitable, but it wouldn't totally explode like in the movie either.

Nice, but why always with the "deathrays", hyperkinetics anyone?

Applied to the deathstar: Could a stream of particles at near c do something like that?

The problem with an antimatter approach is that the antimatter would never get inside the planet. When the antimatter contacts matter, it generates very high energy gammas, which radiate in all directions, including toward the antimatter. Those gammas are absorbed and heat up the antimatter, ablating it and turning it into plasma and also generating a radiation pressure that greatly exceeds the physical strength of all known materials.

An alternative and (I think) more plausible method for destroying a planet and which is perhaps more doable, only requiring technology that can manipulate gravity is via generation of small black holes which evaporate.

Using your value of 2.5x10^15 kg, that could be done with black holes that evaporate shortly after generation.

A black hole with a mass of 2.5x10^15 kg has an inconveniently long evaporation time.

3 second evaporation time is 3.3x10^5 kg. You would need ~10^10 of these mini-black holes. You could use somewhat fewer and larger black holes if they were generated in specific configurations and in-spiraling so as to coalesces at the proper time and place. The in-spiraling black holes would release significant energy as gravitational radiation, which is perhaps somewhat more benign and doesn't convert all of the planet to plasma the way that antimatter generated high energy gammas would.

The 3 second destruction time is rather faster than essentially any type of shock can propagate through the planet. Even if 1.25x10^15 kg of antimatter could be deposited at the center of the planet.

Depositing a week's worth of a star's energy a few tens of thousands of miles from a Death Star would put a “strain” on any radiation shields. Using many mini-black holes, allows the high temperature plasma to be captured by black holes that remain dark. You could (in theory) deliver the right number, quantity and configuration of black holes to vaporize enough of the planet to expel the relatively cool crust while capturing the core and high energy plasma in additional black holes that remain dark. In principle, if you can manipulate black holes, then you could have the infalling mass/energy radiate away as gravitational radiation, or generate additional mini-black holes that are accelerated away via multi-body interactions.

Mini-black holes make a pretty awesome weapon. Adjust the mass so it evaporates just as it reaches its target and no material substance could withstand it. You really would need gravitational shields at Schwarzschild level fields to cope with it.

By daedalus2u (not verified) on 22 Sep 2014 #permalink

This is a tangential question but it is very important. How does gravity on the Death Star work? Does everyone stand in the same universal direction (up is up) on and in the Death Star or is it based on the core so one pole up is up and from that person's point of view, someone standing on the other pole is upside down?

Later, faceless people on Usenet told me — with no doubt whatsoever and something of an incredulous tone — that this was nonsense because in a matter-antimatter annihilation, NONE of the energy that results is converted into kinetic energy that might eject material adjacent to that which is annihilated.

I find that dubious. First, because conservation of momentum says that if you shoot mass A into mass B, the system must end up with the same net momentum it started with - so some of the energy produced by the primary reaction must be kinetic. The balls can't just stick together, unmoving, releasing gammas; m1v1 must equal m2v2. But that may be an insignifirant contribution in the grand scheme of things; more importantly, it is hard to imagine that none of the resulting gammas would undergo secondary reactions with the planet's matter in a such a way as to impart kinetic energy to them.
In fact that is so unfeasible that I wonder hwether your usenet friends were arguing over primary reactions only, and tacitly accepting that such secondary reactions would occur.

The initial matter-antimatter reaction would produce very high energy gammas, 510 keV from electron-positron and ~900 MeV for proton-antiproton.

These have short interaction lengths in matter, where they are scattered causing ionization and energy deposition. The energy flux is so large, that matter near the source is heated very hot, so hot that it radiates black-body radiation that is very hard x-rays. This radiation also has a short interaction length in matter, so it is absorbed to, and heats up the next increment of matter.

The expansion of the fireball occurs via radiation (the same way a nuclear warhead fireball expands). There isn't time for anything to move, the photons heat stuff up so rapidly that it doesn't have time to move.

Heating matter from ambient to billions of degrees makes the pressure go up. That pressure is what causes stuff to move.

By daedalus2u (not verified) on 23 Sep 2014 #permalink

I recently learned that there was much much more to the Death Star, such as 64 separate laser generates on the inside, with miles of focusing lenses, and gravity magnifiers, which consisted of was 3 large circles spinning around each other. There were two of these in between each set of lenses. Taking into account that they had such advanced technology such as laser based weapons, the ability to almost revive the dead, and create beings such as general grevious, and a clone army in a matter of weeks, the death star had the power to do all this. And what is this about recoil? I do not understand how an energy beam would cause recoil since there is no explosive force behind creating it, that I learned in high school.

By galacticall co… (not verified) on 23 Sep 2014 #permalink

Eric @ 32,

It was a long time ago, but they definitely insisted that material would not be ejected (and hence that the refueling strategy would not work, which was the point). You always did get a lot of know-it-all types on Usenet who assume more knowledge than they actually possess, and I suspect they simply conflated "all primarily affected material is annihilated" with "no material is secondarily affected". They didn't explicitely mention kinetic energy, but I stand by my paraphrase because it's clearly equivalent to the "no ejecta" claim.

I wrote my previous comment on the spur of the moment, since the article reminded me of the discussion which I have not thought about for a number of years now. But I did think about it afterwards, and came to the conclusion that they were wrong (gamma rays heat surrounding material, heated material expands, propulsion results).

I also concluded, however, that it's an unnecessarily complicated way to collect fragments of antimatter. If antimatter planets exist, then so must antimatter asteroids (including arbitrarily small ones), and much simpler just to collect those.

By Adrian Morgan (not verified) on 23 Sep 2014 #permalink


In general life, we are not normally required to deal with this fact, but the fact is that photons have momentum. By conservation of momentum, if you shoot a photon out of a laser, the laser will experience a recoil. For lasers that we currently use, this recoil is vanishingly small because the momentum of photons is generally smaller than anything we are accustomed to dealing with. However, if you had an energy beam with sufficient energy to destroy a planet, I would think that there might be a non-negligible recoil.

I wonder at how a body of anti-matter could be generated/contained/ controlled in a world/universe of matter.

I wonder at how a body of anti-matter could be generated/contained/ controlled in a world/universe of matter.

Physicists do this in the lab, today. You use high vacuum magnetic bottles and traps.

(In more depth: antiprotons and antielectrons will have a charge, just like their matter counterparts do. So you put magnets around them with the same charged pole facing 'in,' and that will suspend the particle between the magnets. As long as the chamber is evacuated of all normal matter (i.e., it's a vacuum), the antiparticle can remain suspended, not touching any matter, indefinitely.

Thanks, Eric. I can understand the lab process for the containment part of the exercise. I just wondered on a planetary scale how this could be achieved.
What could be used to generate the anti-matter in the first place in a matter oriented world ?
Then the anti-matter would need to be controlled, aimed, and directed at its target. Hmmm, anti-matter rail gun?

We seem to be able to think rather easily in terms of destructive weapons; wouldn't it be a nice change to develop peaceful engagements instead .....

You may be able to contain in a lattice, where you have the anti-matter held at a vertex that energetically wants it kept there, as long as you don't disturb the lattice enough (e.g. heating or sound waves), it won't reach the nearest matter. Momentum works the same way for matter as for anti-matter (no matter what E E Smith says), so you could use phonons to eject antimatter in small amounts in well defined trajectories too.

You obvious missed to calculate the power of the dark side!!

The whole premise of this article is applying current Earth based science and technology to the problem of what is required "blow up an Earth sized planet". Far more energy is required to travel the immense distances between star systems then is needed to cause one planet to blow up.

What is the Death Star's propulsion? A form of gravity control powerful enough to move a Moon sized object not only through normal space but through "hyperspace" achieving faster then light travel?

That hyperspace is probably a parallel universe with completely different physical laws and accessed by an advanced technology able to scoop energy from there to fuel starship engines and weapons. Energy limited only by the ship size and available volume to carry the necessary equipment. The bigger the craft, the bigger equipment that can utilize this hyperspatial energy, i.e. small 1 man X-wing fighters, through Corillian Star Destroyers up to craft the size of the Death Star.

With this in mind the Death Star's reactor core would only be necessary to power ship systems and the exciters needed to harvest power from hyperspace that provide the energy to move through space and blow up planets. My speculation is the Death Stars engines double as a gravity control propulsion system and easily switched to a main weapon system that utilizes a ranged gravitational collapse to destroy ships and worlds.

We understand the physics explaining how massive stars fuse elements up to iron and the collapse and rebound of those iron cores at near light speed cause the stars to go supernova and explode. An advanced civilization (a long time ago and far, far away) could then use a Death Star's weapon to use the same physics to introduce a mini version of the collapse/rebound/explosive potential of supernovas into the target planet or ship.