That's No Moon
January 16, 2012 8:22 AM Subscribe

This article aims to investigate the first ‘Death Star’ from the ‘Star Wars’ film series and how much energy it would require to destroy a planet.
posted by veedubya (79 comments total) 5 users marked this as a favorite

Untrusted connection? No thanks.
posted by starvingartist at 8:27 AM on January 16

"However, it would probably struggle on very large planets and it would not be capable of destroying stars."

Really? You're just going to softball it in like that?
posted by griphus at 8:27 AM on January 16 [1 favorite]

Erm, two pages? That's it? Hardly a geekgasm. Not even geekforeplay, even.
posted by Capt. Renault at 8:28 AM on January 16 [1 favorite]

Something I've always wondered is if it would have actually been possible for the Death Star to blow up Alderaan the way it did -- causing the planet to explode like a bomb, rather than simply breaking it into chunks.
posted by El Sabor Asiatico at 8:29 AM on January 16

Something I've always wondered is if it would have actually been possible for the Death Star to blow up Alderaan the way it did -- causing the planet to explode like a bomb, rather than simply breaking it into chunks.

Paging Mythbusters. Mythbusters to the white courtesy telephone please.
posted by shothotbot at 8:31 AM on January 16 [6 favorites]

I always assumed that the beam somehow excited the planet's core, making the whole thing explode from the inside out like an egg in a microwave.
posted by Faint of Butt at 8:32 AM on January 16 [2 favorites]

They explain it in a few extended universe novels. Alderaan's entire economy revolved around supplying the rest of the galaxy with nitroglycerin, methane, gunpowder, aerosol cans, fireworks and pre-filled grain silos.
posted by griphus at 8:32 AM on January 16 [34 favorites]

Conclusion: The ability to destroy a planet is insignificant next to the power of the Force. But, I'm overseeing construction of these two Death Stars anyway. Under protest, mind you. And I won't prove my point by building both of them with a fatal flaw, no I wouldn't.
posted by RobotVoodooPower at 8:34 AM on January 16 [11 favorites]

I'm pretty sure it would take, and I quote, "Half the starfleet with more power than I've--"

...and then Han's expert witness testimony was cut off.

Stupid Lucas.
posted by scaryblackdeath at 8:45 AM on January 16 [1 favorite]

But the Death Star isn't real.
posted by swift at 8:51 AM on January 16 [3 favorites]

. . . causing the planet to explode like a bomb, rather than simply breaking it into chunks.

Clearly, the planet's core consisted of molten whatever it is that villainous henchmen in action movies keep in the trunks of their cars.

I think it's called plotignite.

posted by Herodios at 8:54 AM on January 16 [10 favorites]

The ability to destroy a planet is insignificant next to the power of the Force.

You know, this thing Vader does here is kind of a thing, really. Here's the original exchange, from IMDB:

Admiral Motti: Any attack made by the Rebels against this station would be a useless gesture, no matter what technical data they have obtained. This station is now the ultimate power in the universe! I suggest we use it!

Darth Vader: Don't be too proud of this technological terror you've constructed. The ability to destroy a planet is insignificant next to the potential of the Force.

Admiral Motti: Don't try to frighten us with your sorcerous ways, Lord Vader...

What Motti probably meant to say was "Oh, not this bullshit again." Because what do you do with that? Next to "the potential" of the Force? What potential? Why potential rather than fact? Because extraordinary claims demand extraordinary evidence.

Is Vader suggesting that an individual Jedi or Sith could try really really hard at using the Force and blow up a planet on his lonesome with the power of his flexed midichlorians? Because that'd be pretty impressive but the most we ever see is some localized object-hurling and stunts like Yoda brain-deadlifting an X-Wing. We don't see the Emperor—a reliably bad dude who appears to be pretty far up there on the whole mastery-of-the-Force list and who would clearly enjoy such things—making even too-short Imperial Stormtroopers explode, let alone planetary bodies. So it's clearly not a matter of won't as it is can't, and if the gulf between potential and practice is that vast then yammering about potential is pretty facile.

If Vader's suggesting something more like the potential result of every single Force-sensitive being in the universe getting together for a training montage and then millions or billions of them collectively using their Force powers together all at once to explode a planet, that's, well, a neat image but it's utopic revolutionary propaganda, not, again, some sort of practical statement of the Force's potential in a contemporary context. If everybody on Alderaan's northern hemisphere all jumped at exactly the same time, that'd be kind of neat too, but it's also not going to happen.

Maybe Vader was making more of an argument for indirect means—like, the potential power of the Force is in the long game, like the Emperor could use his Sith powers over a series of decades to rise to a position of power in civilian government and use that to marshall a military-industrial complex sufficiently wealthy and organized that it could accomplish something like building a mobile battlestation capable of blowing up planets. In that sense the potential of the Force is realized: the Force allowed Sidious to get his Death Star on, twice even, and he used it to blow up...one planet? Let's say he blew up a few more off screen between the Alderaan situation and him taking a dive down the Death Star 1.1b's energy shaft. Is that really what Vader wants to brag on? One crazy power-hungry asshole that he works for spending a lifetime acquiring the capacity to blow up a planet and do the equivalent of shouting HOW DO YOU LIKE THOSE APPLES at a grad student from an expensive Republic university?

Basically, there's no indication that the potential of the Force has shitall to do with the practical fact of a goddam planet-busting space station. I'm not saying Vader shouldn't have choked Motti a little—he is, by all appearances, a sarcastic dickbag and if you're gonna get your limbs chopped off and your lovelife ruined in a prequel you ought to at least be allowed to asphyxiate the occasional ankle-biter—but I get the feeling Motti et al have heard a lot of this shit from Vader over the years.
posted by cortex at 8:56 AM on January 16 [57 favorites]

"It would not be capable of destroying stars."

Makes a Star Destroyer seem a bit of a silly name for a mere spaceship.
posted by TheAlarminglySwollenFinger at 8:57 AM on January 16 [1 favorite]

I'm no physicist, but if I'm getting the gist of their argument correct, they're assuming that 1) Alderaan is completely solid, unlike the Earth, which is basically a big molten blob of iron and rock covered by a thin skin of solid rock, and 2) that you have to completely overcome the "gravitational binding energy" of the planet all at once in order to destroy it. Not plausible.

Also, cortex, see also The Power of Love [TVTropes[.
posted by Halloween Jack at 8:59 AM on January 16

Thanks for reminding me of my beloved Star Wars Technical Commentary! Relevant section here, my favourite here.
posted by hat_eater at 8:59 AM on January 16 [1 favorite]

...but I get the feeling Motti et al have heard a lot of this shit from Vader over the years.

I'm going to assume everyone who has ever served around Vader got an earful of that at least once, regardless of the relative accomplishments he's observing:

"Don't be too proud of this containment reactor you've repaired. The ability to keep us alive is insignificant next to the potential of the Force."

"Don't be too proud of this wampa steak you've grilled. The ability to evenly char is insignificant next to the potential of the Force."

"Don't be too proud of this ceramic latrine you've unclogged. The ability to snake a toilet is insignificant next to the potential of the Force."
posted by griphus at 9:03 AM on January 16 [28 favorites]

Is Vader suggesting that an individual Jedi or Sith could try really really hard at using the Force and blow up a planet on his lonesome with the power of his flexed midichlorians?

He's talking about the riddle of steel. Palpatine's use of the force enabled him to dominate the entire galaxy under the nose of the Jedi. Destroying a single planet is crude and simplistic in comparison.
posted by Brandon Blatcher at 9:06 AM on January 16 [9 favorites]

He's talking about the riddle of steel.

Yes, but if, cf. Kenobi, "the Force is what gives a Jedi his power. It's an energy field created by all living things. It surrounds us and penetrates us; it binds the galaxy together", if in fact the Force is an all-pervasive background-radiation substrate of the universe which some sensitive folks are able to manipulate locally but which exists everywhere all the time in any case, surrounding and penetrating and binding and all that, then arguing for the potential of the Force is like arguing for the potential of the strong nuclear force. And while I actually like the idea of shouting "that gun would be useless without PHYSICS!" at people, it's a pretty silly argument.

I would accept something like "don't be too proud of this technological terror you've constructed. The ability to destroy a planet is insignificant if the Emperor chops your fucking balls off for being a mouthy asshole" as being a more reasonable statement of riddle-of-steel type warning to Motti to not dismiss the Machiavellian agency of the dude they all work for than to pin it vaguely on the Force. The Force, in that formulation, isn't really what would potentially be nutcrackering an Admiral for insubordination.
posted by cortex at 9:17 AM on January 16 [4 favorites]

The Death Star uses sympathetic resonance to perform its foul deeds. You don't actually need all that much energy to destroy a planet, you just need a really big tuning fork and the exact resonant frequency. Then, all the physicists on the planet read this explanantion, and the cumulative force of all of their heads asploding destroys the planet.

Such is the power of the force of illogic. This psuedo-science, you see: it vibrates.
posted by It's Raining Florence Henderson at 9:18 AM on January 16 [7 favorites]

Palpatine's use of the force enabled him to dominate the entire galaxy under the nose of the Jedi. Destroying a single planet is crude and simplistic in comparison.

Yeah, the thing is that Vader's right. It's probably super-annoying to deal with a mouthy cyborg warrior-scholar when you just want to build The Biggest Fucking Laser, but the most the Empire accomplishes with the Death Star is the destruction of one planet. The most they accomplish with the Dark Side, working in the shadows in ways that we aren't even shown, is full Galactic Empire. Like, we the audience never see the Emperor doing too much; for all we know, he spends 90 percent of his time in a locked room engaging with the underpinnings of the universe, subtlely changing the course of fate like a puppetmaster pulling on the cytoskeleton of an amoeba.

"Over the last few years, the Chinese have changed their strategy in Tibet, increasingly relying more on ethnic and economic colonization than on military coercion, rapidly transforming Lhasa into a Chinese version of the capitalist Wild West with karaoke bars and Disney-like 'Buddhist theme parks' for Western tourists. In short, what the media image of brutal Chinese soldiers terrorizing Buddhist monks conceals is the much more effective American-style socio-economic transformation: within a decade or two, Tibetans will be reduced to the same status as that of Native Americans in the United States. It seems that the Chinese Communists have finally learnt the lesson: what is the oppressive power of secret police, prison camps, and Red Guards destroying ancient monuments, compared to the power of unbridled capitalism to undermine all traditional social relations?"
-Slavoj Zizek, Living In The End Times
posted by Greg Nog at 9:23 AM on January 16 [11 favorites]

Yes, but if, cf. Kenobi, "the Force is what gives a Jedi his power. It's an energy field created by all living things. It surrounds us and penetrates us; it binds the galaxy together"

Yes, but Kenobi was a known manipulator of the truth, so why believe him?

I see the exchange as Vader's way of dealing with unbelieving fools he's not supposed to kill, so he feels the need to interject statements. It's sort of like a nerd fight with him, he had to prove the other guys wrong, because he knows they're wrong.

I wonder if he ever voiced these concerns to the Emperor.
posted by Brandon Blatcher at 9:28 AM on January 16 [2 favorites]

but the most the Empire accomplishes with the Death Star is the destruction of one planet.

Under the iron-fisted direction of the Emperor, who is the grand facilitator of the Force and who yet manages to get in a petty squabble with his co-worker's son and ends up getting his ass killed as a result, shortly before and largely independent of the scrappy and apparently mostly Force-free Rebels blowing up the Death Star again anyway.

If the Force gets credit for Sidious building up the Empire from scratch, it also gets credit for him totally blowing that all over a crappy family get-together. At which point the potential of the Force is for things to happen that are either impressive or totally unimpressive, which is some pretty serious mission creep for a mystical force; this mostly sounds like an argument for the potential, and potential for catastrophic collapse, of human power and hubris. Which, and again this is my main point, just doesn't feel like what Vader was going for rhetorically when Motti went and eyerolled himself breathless.
posted by cortex at 9:42 AM on January 16 [1 favorite]

(joke about union labor)
posted by 1adam12 at 9:42 AM on January 16 [1 favorite]

Just the other day I was thinking about the fact that the earth gets warmer as you go down, because of all the heat radiating out from the core. And of course that made me think of the Alderaan scene. Actually, more specifically the asteroid field immediately afterwards. And, what I was thinking is that all those asteroids should have been glowing red hot. Because the vacuum of space is actually a relatively poor absorber of heat, and if a planet takes billions of years to cool down, even a relatively small asteroid of a few hundred meters across should take longer than a couple hours.
posted by meinvt at 9:43 AM on January 16 [2 favorites]

The Death Star was a flagrant misuse of resources. You don't need to actually blow up the planet when you have the capability to reduce its entire surface to molten radioactive slag. Instead of spending all of those resources to build one big battlestation, just build a bunch more Executor-class Super Star Destroyers. When a couple of those show up in orbit around your planet with attendant support vessels and such, you'll be saying "Yes sir, Mr. Emperor sir!" in no time.
posted by vibrotronica at 9:46 AM on January 16 [1 favorite]

It's sort of like a nerd fight with him, he had to prove the other guys wrong, because he knows they're wrong.

Something like that, yeah. You can (a) know why Linux is a really solid operating system and a good solution for lots of situations and (b) be understandably annoyed at people who think their Xbox 360 is the greatest piece of computing hardware ever built and still (c) say some really stupid shit at LUG meetings. Vader might as well have been talking about the potential of Beowulf clusters.
posted by cortex at 9:46 AM on January 16

Pffft. It doesn't take that much energy to asplode a papier-mâché model. DUH.
posted by clvrmnky at 9:47 AM on January 16

Makes a Star Destroyer seem a bit of a silly name for a mere spaceship.

I think they're supposed to be destroyers-in-the-stars, not destroyers-of-stars.
posted by kirkaracha at 9:48 AM on January 16 [3 favorites]

You don't even have to slag the whole planet to execute the Tarkin Doctrine. Just a continent or two would do.
posted by vibrotronica at 9:52 AM on January 16 [1 favorite]

Don't be too proud of this technological terror you've constructed. The ability to distribute a Beowulf cluster is insignificant next to the potential of the Grendel.
posted by It's Raining Florence Henderson at 9:52 AM on January 16 [1 favorite]

If the Force gets credit for Sidious building up the Empire from scratch, it also gets credit for him totally blowing that all over a crappy family get-together.

Nah, that was the Emperor being too greedy, i.e. getting emotional. Which is understandable. If I has spent decades building an Empire, I be looking for quicker ways of instilling the requisite fear to cement said Empire. Why spend years manipulate when you can just crack a whip?

The Emperor needed that empire to be able to get the resources to build the Death Star and even then, he only managed to put out two. Sucker's were expensive and took a while. Plus, he was little crazy, desiring power for its own sake, instead of doing specific with it, except get more power.

Vader might as well have been talking about the potential of Beowulf clusters.

It was clear the boy had issues. I doubt he socialized much after a certain incident, you know? All he had left was proving the Force was all powerful.

Plus, wasn't Vader an indentured servant, as opposed to co-worker?
posted by Brandon Blatcher at 9:53 AM on January 16

Why spend years manipulate when you can just crack a whip?

Are you saying the Emporer couldn't give the past a slip?
posted by kirkaracha at 9:56 AM on January 16 [2 favorites]

I don't think that anything we're shown in ANH shows that the fragments of Alderaan were no longer gravitationally bound. If you take an earth-sized planet and carve it into 1km³ chunks (of which there would be something like 10^12) and impart something like 1/100 or 1/1000 of the gravitational binding energy of the whole planet, what are the pieces going to do on a timescale of hours?

Anyway, we also know from ANH that the Death Star couldn't destroy a gas giant and then a rocky planet in quick succession, so if that's what running the numbers says too then I guess George did better than I expected this one time.
posted by jepler at 9:58 AM on January 16

The Diary of Grand Moff Tarkin.
posted by Brandon Blatcher at 10:00 AM on January 16 [1 favorite]

So how much energy does it take to accelerate spaceships to superluminal velocity? Because the last time I checked I'm pretty sure the answer was that it would take an infinite amount of energy to reach the speed of light.

So whatever the Star Wars tech is doing clearly has end-runs around normal physics. I always assumed that the Death Star beam summoned the energy out of some other dimension, and that the extravagant show of excess was made precisely to be extravagant. I'd assume it works something like gridfire in Iain Banks' Culture novels, where there is a nearly infinite pool of energy waiting to be tapped and the real danger isn't running out but releasing it by accident.
posted by localroger at 10:00 AM on January 16 [1 favorite]

Darth Vader: Don't be too proud of this technological terror you've constructed. The ability to destroy a planet is insignificant next to the potential of the Force.

While I enjoy a good beanplating as much as the next guy, the line -- in both the original and the Special Edition -- is "insignificant next to the power of the Force."

I knew lining up at the Centre Mall Twin Cinema all those times in 1977 would someday pay off.
posted by ricochet biscuit at 10:09 AM on January 16 [3 favorites]

I think they're supposed to be destroyers-in-the-stars, not destroyers-of-stars.

I think it is a naval reference.

you know, for destroying oranges
posted by b1tr0t at 10:13 AM on January 16 [1 favorite]

It's a homeopathic death beam. Very little actual energy used.
posted by Babblesort at 10:23 AM on January 16 [1 favorite]

Sounds vegan actually.
posted by Brandon Blatcher at 10:27 AM on January 16

The power of the Force is so strong, Darth Vader could kill you with a tray.
posted by Pendragon at 10:28 AM on January 16

without a tray, even.
posted by Pendragon at 10:28 AM on January 16

The ability to destroy a planet is insignificant next to the power of the Force.

Basically, there's no indication that the potential of the Force has shitall to do with the practical fact of a goddam planet-busting space station.

I always took Vader's quote to mean: "While this Death Star is lovely, someone with power in the Force could take it out."

Which is exactly what happens.
posted by flarbuse at 10:35 AM on January 16 [8 favorites]

I always took Vader's quote to mean: "While this Death Star is lovely, someone with power in the Force could take it out."

More awkward family moments

Vader: Son you destroyed my place of work and several hundred thousand co-workers. I'm not sure I should let you in the house.

Luke: Whatever, you're just a glowing dead guy.
posted by Brandon Blatcher at 10:41 AM on January 16 [1 favorite]

The power of the Force is so strong, Darth Vader could kill you with a tray.

Sorry, aboard the death star, all trays must be stowed and locked in the full upright position during take-offs, landings, transitions to warpspeed, and planet bustings.

Sounds vegan actually.

No, that's Contact.

posted by Herodios at 10:44 AM on January 16 [1 favorite]

swift: "But the Death Star isn't real."

Yeah, now. They blew it up. Twice.
posted by Splunge at 11:26 AM on January 16 [3 favorites]

Imagine another world, another timeline. A universe in which Darth Vader and Palpatine never died in the films. Instead, we would have been treated to an endless series of Star Wars movies. We could be looking at around 12 Star Wars films. In each film, the story would alternate between a Death Star being destroyed, and a death start beginning construction. Imagine this world. Imagine this wonderful world.
posted by TwelveTwo at 11:36 AM on January 16

In each film, the story would alternate between a Death Star being destroyed, and a death start beginning construction.

No, eventually we'd have a Super Awesome Death Star, a super planet sized station that houses moon sized Death Stars. Imagine something like Jupiter, cruising around the galaxy with its 60+ moons, dealing death and destruction to all who talk while movies are on.

It would be a beautiful.
posted by Brandon Blatcher at 11:40 AM on January 16

No no no. What you'd end up with is a galaxy-wide strike. Neither the Sith nor Jedi can stand up to the combined might of the Electricians', Welders' and General Contractors' Local 273 after they get fed up with attrition rates from constant and eerily predictable workplace "accidents."
posted by griphus at 11:42 AM on January 16

What, are you kidding me? With the triple OT pay and the hazard insurance, this is a sweet, sweet gig! Vote Palpatine! The true power of the Force is... jobs creation!!!
posted by It's Raining Florence Henderson at 11:46 AM on January 16

The true power of the Force is... jobs creation!!!

The hell you say.
posted by ricochet biscuit at 11:54 AM on January 16 [1 favorite]

The power of the Force is so strong, Darth Vader could kill you with a tray.

Oh! The plate is hot!
posted by ROU_Xenophobe at 11:59 AM on January 16

Do I need new glasses? It looks to me like it says you need 10^32 J to destroy it, while the deathstar pumps out about 10^26 J/s. That's about 11 days. So yes, it can do it, but it won't be "pew-pew-kaboom".

Nope. 3 x 10^26 Js is the output of our sun, a single main-sequence star, whereas the Death Star's hypermatter reactor provides the power equivalent of several main-sequence stars. So it has power to spare.
posted by veedubya at 8:58 AM on January 16 [+] [!]

But even with the benefit of the doubt ('several' = '10') that's still only 3x10^27 J/s, innit? So we're looking at a toe-tappingly long ... 8 hours?

Poor Princess Leia would be famished. They'd need to serve refreshments and have toilet breaks.
posted by Sebmojo at 12:34 PM on January 16 [1 favorite]

If Tarkin were alive today, I'm sure he could tell you how he actually only intended to use the laser to have the Alderaan'ians lose control of their domesticated cats—hopefully then throwing the lucrative Alderaan'ian cat-toy-based economy on the skids.

Had he but paid attention in his geology class back at Emperial Uni, he might've learned that Alderaan had a crust made of Mentos™, a mantle of Coca-Cola, an outer core of Pepsi Cola, and a inner core of pure, unadulterated Pop-Rock.
Honestly, that place was a ticking time bomb from the get go.

(Also, it should be noted that the power of the laser was higher than normal due to a mis-read of the blueprints; I mean, for every mention of Metric, they referred to "Imperial" like 12 different times)
posted by blueberry at 12:41 PM on January 16 [1 favorite]

Back to TFA:
This is because most main sequence stars output far more energy by nuclear fusion than required by the weapon. For example the Sun outputs 3 ⨉ 1026 J s-1[7].

This isn't even a reasonable semblance of a research paper. The authors conflate energy (J) and power (J s-1); nothing they argue in the paper means diddly.

If you're going to play Pretend The Fiction Is Real, at least get the Real World science down.
posted by IAmBroom at 1:05 PM on January 16 [3 favorites]

Alderaan had a crust made of Mentos™, a mantle of Coca-Cola, an outer core of Pepsi Cola, and a inner core of pure, unadulterated Pop-Rock.

In an alternate universe, rather than being exploded, Alderaan disappears only to be replaced by a floating miasma of Galactus-vomit.
posted by griphus at 1:16 PM on January 16

this article says the journal is by and for undergraduates, meaning the authors are only students, so maybe we can go easy on them?

I was thinking that the Death Star may have been operational for days or weeks. Perhaps it has a big-ass capacitor and can store the energy over the days or hours it takes to accumulate, and then "pew-pew-kaboom"
posted by secretseasons at 1:17 PM on January 16 [1 favorite]

(I guess I could check the Death Star's plans for such a capacitor, but my R2 unit says he can only show the plans to his previous owner, a resident of these parts)
posted by secretseasons at 1:20 PM on January 16 [3 favorites]

I look forward to the author's monograph on the the viability of mining explosive crystals from planetoids by shooting them, vis-à-vis Sinistar.

Also, a detailed scatter-plot comparing the efficacies of various taunts on one's attacker in a variety of situations. Specifically, I refer to The People of New York vs. "I Hunger!... Run Coward! Run, Run Run!"

Also, if it's not too much trouble, I would like to see a simple org chart of the Geldra organization, and perhaps a glimpse at their Outlook calendar since a lot of their workday seems to be wasted on going in and out of meetings unremittingly.

So yeah, basically I want to hire myself out as an efficiency expert for fictional criminal organizations. I mean, just running the thumbnail numbers, any fool can see that the Mr. X and the 5 Sons of the Devil waste a tremendous amount of their bottom line on clay pots and snakes alone!
posted by blueberry at 1:26 PM on January 16 [1 favorite]

Previously on metafilter: The Economics of Death Star Planet Destruction, from the always erudite Overthinking it.
posted by autopilot at 1:56 PM on January 16 [1 favorite]

"Nope. 3 x 10^26 Js is the output of our sun, a single main-sequence star, whereas the Death Star's hypermatter reactor provides the power equivalent of several main-sequence stars. So it has power to spare."

Erm. Nope Nope. 2*(3x10^26) !> (1x10^32).
As mentioned, it would have to "store up" the output power for a dozen or so days.

Sure ok fine lets gets some batteries. But wait, exactly how much energy *is* 10^32 Joules. Well, if we were storing it in *PURE ENERGY* form (which is to say anti-matter pairs), 10^32 Joules would weigh 10^16 kilograms. That's 100% efficient storage (using present day physics, anyway).

Hmmm.. that sounds like a lot. But how much of a lot? Well, a Nimitz class aircraft carrier has a displacement of roughly 100,000 long-tons (about 1^9 kilograms). So, over the course of 11 days, they would need to accumulate roughly 10 Million Aircraft carriers worth of energy, in anti-matter form.

I mean: my guess is that they're just parking them in rows out back - on the side of the Death Star you can't see from the camera.
posted by TomStampy at 2:23 PM on January 16 [3 favorites]

That's not so implausible. Some estimates of the death star's size are in the range of 165km diameter. The volume of the outermost .5km shell is therefore about 42506km³. If the energy storage medium has the density of osmium (the densest non-exotic material in a list on wikipedia, 22570kg/m³) then this .5km shell would mass nearly 10¹⁸kg, or 100x the requirement you calculate (so the shell could either be 5m thick instead of .5km thick, or the energy density could be only 1% as great as the theoretical limit, or the storage could be interior instead of exterior, or a combination of these factors).

Though the logistics of converting a 5m-thick, 82.5km radius shell of osmium into a directed energy beam at 100% efficiency remains to be explored.
posted by jepler at 3:15 PM on January 16

Actually, I think the math for the Death Star's planet destroying laser doesn't add up because Star Wars is dumb.
posted by Uther Bentrazor at 3:28 PM on January 16 [1 favorite]

I'm happier doing mathematical calculations in this thread about sci-fantasy space stations than in that other thread about how many ounces of gold to the penny ron paul wants us to google.
posted by jepler at 3:31 PM on January 16 [1 favorite]

The nerdgasm is strong in this thread.
posted by deborah at 4:36 PM on January 16

cortex, I find your lack of faith disturbing. Apropos, have you noticed that you can have a Force-lightning wielding mage in Skyrim, clad in a dark robe? That's the potential of the Force.
posted by ersatz at 5:28 PM on January 16

>Erm, two pages? That's it? Hardly a geekgasm. Not even geekforeplay, even.

...as if three voices mumble mumble mumble and were suddenly silenced &c.
posted by cromagnon at 7:04 PM on January 16 [1 favorite]

Others have made excellent points about both the energy resources and timescales involved.

But, the question remains, is a magical super-collimated laser which puts out a few solar-luminosities a reasonable way to destroy earth-like planets?

The back-of-the-envelope answer looks pretty good. (I'm afraid I haven't the interest in Star Wars nor the time to try to do this properly - though, if someone else does it, I'd be keen to see the results.)

Taking a few times Lsun from the post, let's distribute 10^27 W evenly across the surface of the earth. That works out to roughly 1000 Hiroshima bombs per Manhattan-city-block per second. That suggests that it's a fine way to make planets into pretty nasty vacation spots, but doesn't tell us whether it's really a planet-killer.

If you imagine for the moment that the earth remains a solid sphere and just heats up, and ask what the equilibrium temperature would be with that sort of power input, it's around 10^5K. That's 15 times the temperature of the photosphere of the sun, with a density that's only different by a factor of a couple. Without having to do any calculations, then, we can say with some confidence that there will be a lot of ionized atoms in the material near the surface. (In reality, I imagine all sorts of more exciting things are likely to happen when you dump that much energy onto the surface of a planet all at once, but that's hard to figure out without knowing anything.)

There are a couple of different things we could do from there. One quick check is to compare the force due to radiation pressure to that due to gravity on the plasma. Equating those terms, the Eddington Luminosity due to Thompson scattering for an earth-mass object composed of singly ionized Si turns out to be close to 10^27 W. (This is almost certainly a significant over-estimate for an earth-composition cloud.) So, there's definitely enough power input to start tearing the planet apart and ejecting material, especially if the beam is not evenly distributed over the planet surface.

What happens after that is a bit complicated. Over the time (2*10^32 J / 10^27W = 2 days) that it would take to transfer the full gravitational binding energy of the planet, there's going to be a huge cloud of ejecta coming off the planet and surrounding it. How does the magic laser interact with those debris? How long are the death star operators willing to sit around pumping energy into what remains of the planet? Would they bother doing so, given that it seems likely their military targets are all pretty close to the surface of the planet?
posted by eotvos at 8:15 PM on January 16 [1 favorite]

If you take an earth-sized planet and carve it into 1km³ chunks (of which there would be something like 10^12) and impart something like 1/100 or 1/1000 of the gravitational binding energy of the whole planet, what are the pieces going to do on a timescale of hours?

Hm, assuming Alderaan is Earthlike and the back of my envelope is not faulty, the escape energy of something at its surface is about 63 MJ/kg. 1/100 of that energy would mean a velocity of about 1km/s. Fragments would reach an altitude of some hundreds of miles before falling back.

Another way to calculate this: the gravitational binding energy of a uniform sphere is [various constants]*mass/radius. Inject some fraction of its original binding energy, and you get a uniform spherical cloud of fragments of greater radius than the original planet, with correspondingly reduced binding energy. If Alderaan's radius was an Earthlike 6400 km, the cloud will be 7100 km.

But what Our Heroes saw when they came out of hyperspace was a well-distributed asteroid field, not a few-times-planetary-radius hellish plasma ball. Alderaan was well and truly disrupted.
posted by hattifattener at 12:04 AM on January 17

Forgive my ignorance, but do Death Stars move around? It seems like they're built where they're going to be needed and that's it - once they've done their thing and blown up whatever is next to them, that's sort of the end of their usefulness. They're spherical and have no thrusters or engines that I ever noticed.
posted by stinkycheese at 5:40 AM on January 17

@meinvt "Just the other day I was thinking about the fact that the earth gets warmer as you go down, because of all the heat radiating out from the core"

Just want to make sure that you know the reason the equator is warmer has nothing to do with the earth core. It consistently recieves the most sunshine, thats why its the warmest.
posted by amazingstill at 6:26 AM on January 17

stinkycheese: in ANH the Death Star travels both in hyperspace and regular space (Yavin IV is not in the Alderaan system). It's true that some spacecraft have what we recognize as engines that look like they might even work on a reaction-mass principle, but clearly there are other methods of propulsion that work in starwars physics.

hattifattener, I see your argument, but the momentum imparted to the individual pieces will vary. Maybe 1% would go out to 10x the original radius while 99% will stay within 110% of the original radius. (just picking numbers out of a hat here; probably some 1/f distribution at work?). That would mean that out at 10 plantary radii you'd have rocky fragments filling .001% of space by volume and maybe a similar excess of gas. Juggle the numbers as necessary, but it seems like this could fit with the observations made from the Millennium Falcon on its arrival in the Alderaan system.

One last note: I don't think we know how much time has passed between when Ben Kenobi senses the destruction of Alderaan and when they exit hyperspace near the expected location of Alderaan. So it could be minutes or days if it helps explain what we're shown. But not weeks and certainly not months.
posted by jepler at 7:57 AM on January 17

this article says the journal is by and for undergraduates, meaning the authors are only students, so maybe we can go easy on them?

secretseasons, only if they're undergraduate liberal arts majors. Otherwise, they should have been flunked out of their high-school science classes.
posted by IAmBroom at 8:23 AM on January 17

> I always assumed that the beam somehow excited the planet's core, making the whole thing
> explode from the inside out like an egg in a microwave.

You people just have no concept how many planets there are out there that are actually giant cherry bombs.
posted by jfuller at 10:11 AM on January 17 [1 favorite]

IAmBroom: "only if they're undergraduate liberal arts majors. Otherwise, they should have been flunked out of their high-school science classes."

Yeah, 'cause doing a sloppy job of a completely whimsical extracurricular analysis of the physics of star wars is a sure sign that they're idiots. Sheesh.

I teach physics at a small college where if anyone even showed any interest in applying physics to some other context, it would count as a big bonus in my mind
posted by secretseasons at 11:59 AM on January 17

hattifattener, I see your argument, but the momentum imparted to the individual pieces will vary.

Yeah, in practice you'd end up blowing off a shell and leaving a remnant behind. You can calculate the minimum size of the remnant using the same formula. You still end up with a basically planet-sized blob where Alderaan used to be. Solo's reaction wouldn't have been, "Hey, where's Alderaan?", it would have been, "Hey, why is Alderaan white-hot?".
posted by hattifattener at 10:47 PM on January 17

The Falcon wasn't making detailed astronomical observations, though. Simply by luck they're pointing the wrong way to see the white-hot wreck of Alderaan, distracted by the "asteroid collision" and then by the Tie Fighter that just happened to be within naked-eye viewing range. (no shortage of coincidences occur in Star Wars, after all)

Juggle my numbers so that they're at 100x the original radius of alderran, and the angular diameter will be about 35 arcseconds, on the order of the size of the moon or sun seen from the earth. Even if you do see it, maybe you just confuse it for a star.

Whatever system on the Falcon reported that they were in the right place was probably looking at the field of stars, not nearby bodies. Failure to detect an error of 100 earth radii / .004AU / 2 light-seconds from such a system might be totally expected from such a system running on automatic for just a few minutes at most.

And there are other indications in the series that hyperspace travel doesn't always bring you back into normal space exactly where you wanted (the death star emerges on the wrong side of yavin from the moon where the rebel base is, for instance) and the Falcon started its jump under difficult conditions which might further affect the accuracy.

So while the ruined Alderaan would make an excellent effects shot that we should have congratulated Lucas for adding to one of the updates of the series, it's also plausible that it could have been "out there" and just wasn't seen by the characters or the cameras, or it was not recognized for what it was if the characters did see it.
posted by jepler at 7:26 AM on January 18

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