Question/theory regarding the superlaser

[Diplomat]

After reading the various discussions/info regarding the Superlaser I had a question which I didn't see considered-- specifically, the lack of actual heating of the planetary mass.

The figure of 1E+38J for a planet of 1E+24kg, comes to an average of 1E+14J/kg-- enough to heat the mass by about 30 billion degrees Kelvin, which would obviously vaporize it (not even counting fusion/fission issues). However this is inconsistent with the "Alderaan graveyard" (i.e. the asteroids which the Falcon runs into), which indicates that the planet was not vaporized, but was simply dispersed into a local asteroid-field.

And when the planet explodes, we don't even see any of the pieces glowing-- as it would if even an earth-like planet was to be taken apart without adding any energy. If the planet was vaporized, there would simply be a bright flash.

Likewise, this seems most consisent with SW tech seems to indicate any such , the most advanced of which seems to pertain to hyperspace devices (drives, communicators etc)-- which are the least explicable by modern means.

Additionally, one thing I didnt' see mentioned in any of the energy-calculations here or elsewhere, was the planet's ambient heat-- i.e. what happened to its geothermal energy-- which averages ; if somehow converted into motion, which would provide more than enough than to propel its mass to escape-velocity of 11km/sec (i.e. 700J/degree Kelvin/kg, or up to about 1900km/s-- i.e. 3.1%C).
(I'm not counting specific-heat of vaporization, since the planet didn't appear to be vaporized.

Therefore, it would seem that the Superlaser could be some sort of entropy-shifting (i.e. hyperaccelerating) device, whereby the planet's ambient thermal energy was dispersed into the space around it, causing it to explode of its own heat-- similar to a hot rock thrown into cold water (which will explode). As a result, both the planet's material and energy would simply be dispersed over a larger area, but would be significantly cooled-- basically a reversal of the planet's formation from asteroid-material (thus explaining the absence of any red-hot material from near the planet's core).

[Wyrm]

After reading the various discussions/info regarding the Superlaser I had a question which I didn't see considered-- specifically, the lack of actual heating of the planetary mass.

The figure of 1E+38J for a planet of 1E+24kg, comes to an average of 1E+14J/kg-- enough to heat the mass by about 30 billion degrees Kelvin, which would obviously vaporize it (not even counting fusion/fission issues). However this is inconsistent with the "Alderaan graveyard" (i.e. the asteroids which the Falcon runs into), which indicates that the planet was not vaporized, but was simply dispersed into a local asteroid-field.

How do you know that a fair fraction of the planet didn't vaporize, and the pressure of that vapor is what scattered the planet? Something had to convert the energy of the superlaser into work.

And when the planet explodes, we don't even see any of the pieces glowing-- as it would if even an earth-like planet was to be taken apart without adding any energy. If the planet was vaporized, there would simply be a bright flash.

All the fast pieces were glowing. Work heating on the chunks. The only chunks that were not glowing were the ones not fast enough to leave the debris field by the time the Falcon arrived. That is, the ones that weren't accelerated very much, and the ones with only a bit of work (and therefore work-heating) applied to them.

Additionally, one thing I didnt' see mentioned in any of the energy-calculations here or elsewhere, was the planet's ambient heat-- i.e. what happened to its geothermal energy-- which averages ; if somehow converted into motion, which would provide more than enough than to propel its mass to escape-velocity of 11km/sec (i.e. 700J/degree Kelvin/kg, or up to about 1900km/s-- i.e. 3.1%C).
(I'm not counting specific-heat of vaporization, since the planet didn't appear to be vaporized.

Please present your calculations that show the geothermal energy of an earth-like planet meets or exceeds the required 1e38 J energy requirement.

Therefore, it would seem that the Superlaser could be some sort of entropy-shifting (i.e. hyperaccelerating) device, whereby the planet's ambient thermal energy was dispersed into the space around it, causing it to explode of its own heat-- similar to a hot rock thrown into cold water (which will explode). As a result, both the planet's material and energy would simply be dispersed over a larger area, but would be significantly cooled-- basically a reversal of the planet's formation from asteroid-material (thus explaining the absence of any red-hot material from near the planet's core).

Let's not violate well-established physical principles like the second law of thermodynamics without some evidence, cupcake.

[Teleros]

However this is inconsistent with the "Alderaan graveyard" (i.e. the asteroids which the Falcon runs into), which indicates that the planet was not vaporized, but was simply dispersed into a local asteroid-field.

1. Any glowing debris is by its very nature radiating heat into space. By the time the Falcon arrived, they had shed enough heat that they didn't look particularly hot in the visible spectrum.
2. You don't need to vaporise every tiny piece of Alderaan: some chunks can survive as asteroids without being heated to vaporisation temperatures.

And when the planet explodes, we don't even see any of the pieces glowing-- as it would if even an earth-like planet was to be taken apart without adding any energy. If the planet was vaporized, there would simply be a bright flash.

Watch ANH. Note great big explosion as Alderaan is blown to smithereens. Note all the glowing bits hurled in every direction.

Additionally, one thing I didnt' see mentioned in any of the energy-calculations here or elsewhere, was the planet's ambient heat-- i.e. what happened to its geothermal energy-- which averages ; if somehow converted into motion, which would provide more than enough than to propel its mass to escape-velocity of 11km/sec (i.e. 700J/degree Kelvin/kg, or up to about 1900km/s-- i.e. 3.1%C).
(I'm not counting specific-heat of vaporization, since the planet didn't appear to be vaporized.

So... the Death Star magically converted all that geothermal heat into propelling the mass of the planet outwards... yeah, that makes sense . You're also forgetting the mini-superlasers seen in AotC on the LAAT-i gunships or whatever they were called, and that's assuming all your calcs are even correct.

Therefore, it would seem that the Superlaser could be some sort of entropy-shifting (i.e. hyperaccelerating) device, whereby the planet's ambient thermal energy was dispersed into the space around it, causing it to explode of its own heat-- similar to a hot rock thrown into cold water (which will explode). As a result, both the planet's material and energy would simply be dispersed over a larger area, but would be significantly cooled-- basically a reversal of the planet's formation from asteroid-material (thus explaining the absence of any red-hot material from near the planet's core).

Hang on a minute. I'll admit I'm no physicist or geologist, but it seems to me that prior to the Death Star firing, the planet was, apart from the crust, basically a ball of very hot, liquid rock... that's been losing heat one way or another since it was formed a few billion years back. At any rate, this planet has been sitting there happily, despite being so hot, all this time... which means to get it to explode would require putting even more energy into it... which sounds suspiciously like the classic explanation of the superlaser (ie, a really big laser).

And we also of course DO see lots of glowing pieces of Alderaan being hurled away from the explosion, never mind the actual explosion itself (guess what the visible parts of the explosion would be made of - yep, Alderaan). Lots of pretty pictures & movies of the superlaser being fired can be found on the main site here.

[Stark]

Turns out to blow it apart, you have to vapourise shitloads of it, and the rate of thermal transmission through the planet would not be even. This is pretty obvious from watches the explosion in progress.

[Junghalli]

A violent explosion is a pretty inefficient means of heating an object. A lot of the debris could easily have been thrown clear before they had time to absorb enough energy to completely vaporize them.

[Darth Wong]

Diplomat, you don't seem to realize that heat is insignificant in this equation. The energy calculation was based entirely on gravity and velocity of the expanding debris cloud, neither of which you can explain any other way. You could take 100% of the internal energy of the planet and it would be utterly insignificant compared to the task of overcoming GPE and accelerating even 1% of the planetary mass to 5% of c, which was the rate of expansion of the cloud.

[Mad]

Additionally, one thing I didnt' see mentioned in any of the energy-calculations here or elsewhere, was the planet's ambient heat-- i.e. what happened to its geothermal energy-- which averages ; if somehow converted into motion, which would provide more than enough than to propel its mass to escape-velocity of 11km/sec (i.e. 700J/degree Kelvin/kg, or up to about 1900km/s-- i.e. 3.1%C).

How did you come up with that number? You must have made some mistake. I plugged in some ridiculously generous numbers for the sake of simplicity to see if I could confirm your number and only got about 2.6 km/s.

I assumed a "planet" with earth's mass that was simply a big ball of iron at the temperature of Earth's core.

• Specific Heat of Iron: 448 J / (kg * K)
• Heat of Fusion of Iron: 2.66e5 J / kg
• Mass of Earth: 5.9736e24 kg
• Temperature at Earth's core: 7000 K

Code: Select all

specific heat  * temperature + heat of fusion = 3.402e6 J/kg

3.402e6 J = 1/2 * 1 kg * v^2
sqrt(2 * 3.402e6) = v = 2608 m/s

Last time I checked, Earth-like planets weren't entirely molten and made of iron, so if the energy released by cooling an entirely molten planet down to absolute zero isn't enough to throw the planet to escape velocity, a much cooler normal planet isn't going to do it, either.

[Darth Wong]

That number was so obviously bogus that I assumed he just pulled it out of his ass and I ignored it. He somehow went from 700 J/kgK to "1900 km/s", which he believes to be 3.1% of c. Every single part of that is wrong. He even fucked up the simple conversion from his ridiculous figure of 1900 km/s to a fraction of c.

Somehow, he figures that every kg of matter in the Earth contains roughly 1.8 TJ of internal energy, hence his 1.9E6 m/s velocity figure. That's not just impossible, it's laughably stupid. It's even funnier if you use his "3.1% of c" figure, which requires that every single kg of the Earth's mass has roughly 43 TJ of internal energy.

[Duckie]

Assuming the entire planet was made of iron, and that each piece was heated equally by the superlaser, would it be possible to calculate how long it would take the glowing chunks to cool down when in an environment of 3K (about the background temperature of the universe IIRC) to not be visibly glowing like the falcon saw them?

I think there might be too few variables without making some assumptions beyond even what I made, but it would be interesting to know as a minimum time for how long from alderaan's destruction it took for the falcon to arrive (and how long the death star waited around).

I'll admit I wouldn't have the slightest idea how to approach the idea though, so I'm just putting it here in case anyone else thinks it's interesting.

[Ender]

Assuming the entire planet was made of iron, and that each piece was heated equally by the superlaser, would it be possible to calculate how long it would take the glowing chunks to cool down when in an environment of 3K (about the background temperature of the universe IIRC) to not be visibly glowing like the falcon saw them?

I think there might be too few variables without making some assumptions beyond even what I made, but it would be interesting to know as a minimum time for how long from alderaan's destruction it took for the falcon to arrive (and how long the death star waited around).

I'll admit I wouldn't have the slightest idea how to approach the idea though, so I'm just putting it here in case anyone else thinks it's interesting.

Estimate an average size, find the mass for that. Use the energy applied and mass to find temperature. Use that surface area for that piece and temperature in the formula for a perfect blackbody. Divide the energy the piece has by the power from that formula to get time.

[Darth Wong]

There is no way that every piece of the planet was heated equally by the superlaser. The whole planet should have been vapourized. It's actually mystifying how any of the planet's mass would survive such enormous acceleration without being vapourized, so one can only start from the assumption that the heat distribution was extremely uneven. Same goes for the velocity distribution. We assume uniform velocity only for the purpose of generating order-of-magnitude energy estimates, not because we actually think the distribution of energy was uniform.

[Connor MacLeod]

Don't forget the planetary shield around Alderaan. Even though it didn't stop the Superlaser, we saw the energy dissipated over the surface of the shield, which is probably by itself going to affect the distribution of the energy input. Plus, whatever energy the shield actually absorbed may have been released when the planet went up, especailly given some of the concepts for shielding dissipating excess energy (didnt one of the ITW books mention Hoth's shield dumped excess energy into the core of the planet or something?)

Edit: I also vaguely recall that Organa spent a huge bundle on some sorts of super-indestructible underground bunker complexes or vaults below the planet (They couldn't withstand a direct hit from a superlaser, ,but they helped protect against it indirectly.) which may have accounted for some of hte visible chunks we saw onscreen as well.