Dumping heat

[Winston Blake]

I'm not sure how low-temperature you could really get an ion engine. [snip] It also would tend to be more visible than a rocket exhaust of similar temperature (not saying there is such a cold rocket, but comparing apples to apples), since the charge on the ions would tend to cause them to repel and scatter more thoroughly than a rocket exhaust. Essentially, the exhaust from ion engines physically cannot be gathered into a collimated beam

I'm pretty sure that ion engines don't actually shoot charged particles out the back, but that they're more like neutral particle beams in that the ions are neutralised before they leave. Otherwise you'd end up setting up a huge current loop in the interplanetary plasma.

[The Dark]

I'm not sure how low-temperature you could really get an ion engine. [snip] It also would tend to be more visible than a rocket exhaust of similar temperature (not saying there is such a cold rocket, but comparing apples to apples), since the charge on the ions would tend to cause them to repel and scatter more thoroughly than a rocket exhaust. Essentially, the exhaust from ion engines physically cannot be gathered into a collimated beam

I'm pretty sure that ion engines don't actually shoot charged particles out the back, but that they're more like neutral particle beams in that the ions are neutralised before they leave. Otherwise you'd end up setting up a huge current loop in the interplanetary plasma.

Electrons are injected into the exhaust to neutralize the charge buildup on the vessel, but you'll end up with both the initial exhaust scatter due to charge and the (very very very low but existent) momentum shift from electron injection. You really don't have to neutralize the entire ion stream, just emit the electrons into space at the same time as the ions are emitted to prevent charge buildup.

Your engines have to be 99.9999997% efficient to accelerate an icecube to 0.99c without evaporating it.

To be fair, ion engines are wonderfully efficient (to the best of my knowledge, the second most efficient "throw shit out the back" space propulsion we've developed), but 99.9999997% is rather more efficient than we've been able to do. Even a Hall thruster (the most efficient "throw shit out the back" system) is only around 70% max, and that's the most efficient electrical propulsion system developed so far.

[Wyrm]

Note that if any of the neutrinos are the weaker muon or electron neutrinos, the number required jumps higher. This is the minimum number of neutrinos a 90% efficient reactor capable of generating an instantaneous hyper jump would generate.

Not neccessarily. The sun pumps out electron neutrinos each having energy on the order of ~2-10 MeV. The <2.5 eV energies stated for electron neutrinos is the rest mass of the neutrinos; this is the minimum amount of energy the neutrino can have, but in order to get anywhere, the neutrinos need kinetic energy.

Electron neutrinos, on the other hand, do have this nasty tendency to interact with matter in charged current interactions, but all neutrinos can interact with matter by neutral current interactions, which at the energies involved can be just as bad. Although the cross section of interaction is small, and only a small fraction of the total energy in neutrino radiation actually gets dumped into you, a large enough number of neutrinos can still roast your cookies.

[The Dark]

Note that if any of the neutrinos are the weaker muon or electron neutrinos, the number required jumps higher. This is the minimum number of neutrinos a 90% efficient reactor capable of generating an instantaneous hyper jump would generate.

Not neccessarily. The sun pumps out electron neutrinos each having energy on the order of ~2-10 MeV. The <2.5 eV energies stated for electron neutrinos is the rest mass of the neutrinos; this is the minimum amount of energy the neutrino can have, but in order to get anywhere, the neutrinos need kinetic energy.

But that kinetic energy will have to be imparted by the ship's creation of the neutrinos, and will thus be work being done by the ship, which will generate heat through inefficiencies in the mechanism. The rest mass will be the heat that is lost by the vessel through the generation of neutrinos.

[Ender]

You realize shields are one way, right?

Then they won't keep neutrinos and IR from reaching any detectors.

I'm curiosu as to this logic - they let things out, but stop things from coming in, therefor they will let things in. I just don't follow.

Energy shields are one way for certain, and the evidence that particel shields have to be dropped contradictory (states in text they need to be dropped, but we see a torpedo stopped by shields agaisnt the engines at Endor). Thuis this is not a concern. Shields would stop your sensors from reading the incoming emisions (barring what you had sticking out beyond the shields) but not what you throw out.

I see, I misunderstood. I though the claim was that the ISD's shield would make it stealth. I wasn't thinking in terms of a shield around the detector blinding it. That seems possible in principle, but the countermeasure is obvious: sensors on pylons or drones outside the shields.

Which we know is done for some circumstances (the Athega incident). But its a bit hard to mount your fuel tank out on a plyon, and we don't know if they can mount IR detectors small enough but still accurate enough like that. And drone we know the the TIE/fc (fire control) and of other fighters serving that purpose.

Typically warships are extremely close. Note that the Executor and its escorting Imperators both pulled 3,000 Gs above Endor. Like I said, they are all in the same order of magnitude, in fact it appears that there is less then 1,000 Gs difference between the fastest and slowest ships.

Well, I was sketching general principles. If all ships' performance is effectively the same, then firepower ought to be all that counts.

But 1,000 gees difference in ships that pull 3,000 gees is a significant performance difference: 33%. You don't have to be orders of magnitude faster than you opponent to choose the terms of engagement.[/quote]That diference is from a troop transport to a frigate noted for its unusually low acceleration.

As for firepower, like I said, if you are running, you lose you heavy firepower.

True, but if you have more legs than the other guy you either get away, or else catch up right close and let him have it. He has to stop running if he wants to shoot back, and if he keeps running you can catch him again. (These simple tactical analyses are, of course, heavily modified when you can force engagement by threatening a stationary asset, or when the faster ship has a safe refuge in range, or somehow runs out of room to flee.

Yes, and the ability to go to FTL compounds it further. Hence the importance of tactics.

I must also mesh with the observed evidence, first and foremost.

Indeed. An explanation that doesn't mesh with the observations that it is trying to explain is no explanation at all. But on the other hand, an explanation that doesn't mesh with teh things we are trying to explain observations in terms of isn't an explanation either.

In this instance, invoking neutrinos to explain the (observed) low temperature of ISDs would fail as an explanation if it didn't mesh with what we know about ISDs. But on the other hand, it would also fail if it didn't mesh with what we know about nneutrinos. At very least it would require further explanation.

The same is true of explanations of the drives and weapons that chew up the non-waste part of the power output: the engines, shields, and weapons.

Hence this thread.

I realise that it is an official statement of some sort, and that it is offered as an explanation. But it only succeeds as an explanation if it is consistent with what we know of neutrions. If it isn't, for instance if it demands further explanation of why those neutrinos are not as detectable as neutrinos actually are, then it is at least insufficient.

Right, and if the sheilds block sensors (or where you would place the sensors) then the problem is neutralized. Then it just becomes a question of why they don't make them small enough to extend beyond the shields, and there you can wave it away by citing sensor tech limits.

I suppose its possible they collaminate it into a beam

No, I don't think it is possible. We'd better ask someone whose physics background is in thermodynamics rather than electromagnetism,

*raises hand* AFAIK Mike and I have had the most training on the subject; though mine was abbreviated and more focused on what was relevent to nuclear reactors rather then thermodynamics on the whole.

I raised this point a little over a year ago in discussion and the response was basically a big "I dunno". I'm thinking of writing a university that runs a neutrino generator and asking about their machine, but I'm not sure if those ae omni directional or focused.

but I have a strong suspicion that such a beam would represent a lot of energy at very low entropy. In other words this would violate the Second Law of Thermodynamics.

I think it might depend on how it is done. Consider, a flashlight is an omnidirectional release of light that is turned into a beam by cupping it in a mirror. The light that hits the mirror is reflected out so it only comes out through the opening.

Now we don't know if shields, assuming they are opaque to neutrinos, absorb them, or scatter them. If they scatter them, one would merely need an internal shield projected around the walls of the radiator room that bounced all the neutrinos back out through the opening.

They might possibly concentrate it into a cone, and point the cone away from know enemy sensors, I suppose. But I thinki thermodynmics requires that this would cost energy, and sets a fairly broad lower limit on the width of the cone.

Indeed. I have seen a few references to "neutrino lasers", I need to dig deeper.

Exhaust you should get scattered gamma flashes from collisions, particularily when it is turning. But you need not get thermal reading from the exhaust plumes. I can have an ice cube moving at .99 C afterall.

Only if the process you use to accelerate the icecube is godawful efficent.

Lets say I toss it out the airlock. This was meant solely as an example.

Besides which, kinetic energy tends to degrade to heat. I expect that an icecube whipping through the interplanetary medium at 0.99c is going to heat itself by friction, and explode into a puff of incandescent vapour. Lets say that the interplanetary medium consists of five million hydrogen attoms per cubic metre. The cross-sectional area of the icecube will sweep out 3E8 cubic metres per square metre per second, so from the point of view of the icecube the interstellar medium is a beam delivering 1.5E15 hydrogen atoms per square metre per second. At 0.99c those atoms have a kinetic energy of (gamma-1)mc^2. Gamma is 6.08 we calculated before. The mass of a hydrogen atom is about 1.7E-27 kg. c^2 is 9E16. That's 1.4E6 Wm^-2, which is about a thousand times as bright as sunshine. It will evaporate 700 metres of ice a second.

Dude, you are digging ay too deep. My only point was that there is a major difference between kinetic energy and thermal energy and that one can have a high kinetic energy with a low thermal energy. Thermal energy is basicall the result of molecular collisions in the substance, despite moving very fast relative to the ship they do not have to be moving fast relative to each other, and thus it can be very cool. It will heat up upon impacting something moving at a different velocity, certainly, but that is different from its temperature when it leaves the engine bells.

Temperature is relative, and a low temperature is going to have very little emissions.

No, temperature is an absolute.

No. Don't let the term "absolute zero" fool you. Temperature is the average random molecular kinetic energy of a substance. Kinetic energy is proportional to velocity, and velocity is relative. Even in experiments on earth where they try to stop all motion in a substance to get it to absolute zero, the slow down is only realitive to the instruments as the substance is still moving at great velocity as earth orbits the sun. If I had a magic device that let me measure the temperature of that substance from the moon I would get a different reading because the molecules would be moving at a different velocity relative to my instruments. This is the same as you outlined above.

Low temperature exhausts, and low temperature wreckage will have low emissions, but I don't think that either one is plausible without a lot of furtehr explanation.

Wreckage no, and I personally I don't buy the exhaust thing as I believe it serves as more evidnece that all ships must ahve shields and there is no real evidence for it, but it is possible.

The tracers on the weapons I'm not sure what you are talking about. They are only a few kilowatts in strength, its not a thermal glow there dude; we see they are green and the human eye can't see green hot because of how our eyes are rigged. Same with purple. Anywyas, the essential guides confirm its nonthermal in nature.

Actually, I was not thinking som much of the glow of the bolts. I was thinking in terms of incandescent wreckage from the targets.

Are you thinking of this from a neutral planetary observer position? Because I'm looking at it from the role of another ship, and the wreckage isn't going to matter because it will have been one of your ships and you already knew where it was.

[The Dark]

You realize shields are one way, right?

Then they won't keep neutrinos and IR from reaching any detectors.

I'm curiosu as to this logic - they let things out, but stop things from coming in, therefor they will let things in. I just don't follow.

That's not what Agemegos is saying. A passive sensor will see the neutrinos and IR passing through the shield on the way out. Such a shield would only block active sensors (which work by emitting something and sensing the return of an object) by absorbing the emission. However, since the ship itself must emit the neutrinos and infrared radiation through the shield to eliminate the heat, a passive IR or neutrino sensor would be able to see the radiation coming off the vessel.

[Ender]

Then they won't keep neutrinos and IR from reaching any detectors.

I'm curiosu as to this logic - they let things out, but stop things from coming in, therefor they will let things in. I just don't follow.

That's not what Agemegos is saying. A passive sensor will see the neutrinos and IR passing through the shield on the way out. Such a shield would only block active sensors (which work by emitting something and sensing the return of an object) by absorbing the emission. However, since the ship itself must emit the neutrinos and infrared radiation through the shield to eliminate the heat, a passive IR or neutrino sensor would be able to see the radiation coming off the vessel.

No, because the incoming neutrinos and IR from the other ship would be stopped by the shield before it got to the sensor.

Ghetto diagram-

----- > | (

--- is neutrinos, > is the scatter from them hitting the shield, | is the shield, ( is the sensor.

[The Dark]

I'm curiosu as to this logic - they let things out, but stop things from coming in, therefor they will let things in. I just don't follow.

That's not what Agemegos is saying. A passive sensor will see the neutrinos and IR passing through the shield on the way out. Such a shield would only block active sensors (which work by emitting something and sensing the return of an object) by absorbing the emission. However, since the ship itself must emit the neutrinos and infrared radiation through the shield to eliminate the heat, a passive IR or neutrino sensor would be able to see the radiation coming off the vessel.

No, because the incoming neutrinos and IR from the other ship would be stopped by the shield before it got to the sensor.

Ghetto diagram-

----- > | (

--- is neutrinos, > is the scatter from them hitting the shield, | is the shield, ( is the sensor.

Assuming all sensors are below the shield, which is not necessarily the case (as with the Executor losing its sensor globes prior to the shields collapsing, or with Pellaeon's ISD losing sensors to a star's radiation).

In fact, you just gave a grand reason to not have shields block the sensor bands of radiation, since a passive sensor can always detect an active sensor from further away than the active can detect a target, not blocking those bands would benefit oneself more than blocking them would.

[Ender]

That's not what Agemegos is saying. A passive sensor will see the neutrinos and IR passing through the shield on the way out. Such a shield would only block active sensors (which work by emitting something and sensing the return of an object) by absorbing the emission. However, since the ship itself must emit the neutrinos and infrared radiation through the shield to eliminate the heat, a passive IR or neutrino sensor would be able to see the radiation coming off the vessel.

No, because the incoming neutrinos and IR from the other ship would be stopped by the shield before it got to the sensor.

Ghetto diagram-

----- > | (

--- is neutrinos, > is the scatter from them hitting the shield, | is the shield, ( is the sensor.

Assuming all sensors are below the shield, which is not necessarily the case (as with the Executor losing its sensor globes prior to the shields collapsing, or with Pellaeon's ISD losing sensors to a star's radiation).

The Athega incident yes, but not the Executor's sensor globes. They also have projector vanes on them, so clearly they are covered.

In fact, you just gave a grand reason to not have shields block the sensor bands of radiation, since a passive sensor can always detect an active sensor from further away than the active can detect a target, not blocking those bands would benefit oneself more than blocking them would.

This is of course assuming that is an option. Blocking of certain bands may just be a side effect that they can't do anything about.

[Wyrm]

Note that if any of the neutrinos are the weaker muon or electron neutrinos, the number required jumps higher. This is the minimum number of neutrinos a 90% efficient reactor capable of generating an instantaneous hyper jump would generate.

Not neccessarily. The sun pumps out electron neutrinos each having energy on the order of ~2-10 MeV. The <2.5 eV energies stated for electron neutrinos is the rest mass of the neutrinos; this is the minimum amount of energy the neutrino can have, but in order to get anywhere, the neutrinos need kinetic energy.

But that kinetic energy will have to be imparted by the ship's creation of the neutrinos, and will thus be work being done by the ship, which will generate heat through inefficiencies in the mechanism. The rest mass will be the heat that is lost by the vessel through the generation of neutrinos.

No. By that argument, blackbody radiation (made of photons which are nothing but kinetic energy) can't cool because the kinetic energy of the emitted photons would have to be supplied from work liberated in the hot object. Since the work would have to be generated with inefficiencies, blackbody radiation therefore generates more heat in the hot object, making it hotter. Obviously, this doesn't happen, because otherwise stars would be getting continuously hotter and hotter as they shine.

The kinetic energy of the neutrinos as they zip out into open space is the heat that we are dissipating. Remember, you only need to do work if the process your considering doesn't disperse energy. In cooling by blackbody radiation, we are divying up the incoherent kinetic motion of a large number of electrons into a much larger number of photons. The surroundings take in the photons and thereby increases the dispersal of the energy, and therefore the surroundings absorb heat from the blackbody. In cooling by neutrino radiation, the neutrinos are taken in by the surroundings and thereby increases the dispersal of the energy, and therefore the surroudings absorb heat from the neutrino radiator.

Keeping the neutrino energies low actually makes the radiation cold. The temperature of a neutrino gas (and consequently, of neutrino radiation) is related to the average kinetic energy of the neutrinos. If the energy in the neutrinos is low, then the temperature is also low. Quickly now, if you have two neutrino gasses, which one carries away the most heat? Right! The hotter one, or the one with higher average kinetic energy.

[NRS Guardian]

Granted. Armour did the same with big-gun battleships, too. WWI battlecruisers were essentially battleships without armour, and the theory was that they would be able to 'out-gun what they can't out-run'. What happened in practice was that their battleship guns were overkill against anything except a battleship: the difference between an eight-inch gun and a fourteen-inch gun doesn't make a lot of difference to either a cruiser or a battlecruiser. And when the battlecruisers went in against the heavies (eg. Jutland) it really mattered that each 14"-15" shell hit did a lot more damage to an essentially-unarmoured battlecruiser than it did to a battleship with over a foot of armour plate and the scantlings to back it up.

Anyway, though that is interesting stuff I'm afraid I've led us onto a bit of a tangent. If submarine-like 'lurk and devastate' tactics do work in space it doesn't particularly matter what tactics would be like if they didn't. Let's get back on track.

I'm sick and tired of people always saying battlecruisers went up against battleships at Jutland. The fact is not one battlecruiser, British or German, ever went up against battleships at Jutland, except for the Germans being shot at from long range by a division of British fast battleships attached to the Battlecruiser Force. All battlecruisers sunk at Jutland were sunk by other battlecruisers. The reason the British had a hard time of it at Jutland was due more to flaws in training and their shells, as well as bad positioning. Rather than any design flaws. Battlecruisers were primarily designed as cruiser-killers, and the Battle of the Falklands proved that the design philosophy was sound. The British battlecruisers just ran into more bad luck than their German counterparts.

[Agemegos]

You realize shields are one way, right?

Then they won't keep neutrinos and IR from reaching any detectors.

I'm curiosu as to this logic - they let things out, but stop things from coming in, therefor they will let things in. I just don't follow.

The ISD's shield lets its neutrinos out. Therefore the neutrinos are there to be detected.

Supposing that shields stop neutrinos from going in, my detectors will not be able to detect the ISD if they are inside my shield and if my shields are up. It is (by this hypothesis) my shields, not the ISDs shields, that make the ISD's neutrinos indetectable. But I, not the ISD, have control over my shields.

I could very easily put my detector on a pylon outside my shield, or on a drone outside my shield. Or I might be in a fleet with a sensor picket ship. I might even drop my shields for a sensor fix for a split second every now and again. In any of which cases I would be informed of the ISD's position.

The same is true of explanations of the drives and weapons that chew up the non-waste part of the power output: the engines, shields, and weapons.

Hence this thread.

Exactly so.

I realise that it is an official statement of some sort, and that it is offered as an explanation. But it only succeeds as an explanation if it is consistent with what we know of neutrions. If it isn't, for instance if it demands further explanation of why those neutrinos are not as detectable as neutrinos actually are, then it is at least insufficient.

Right, and if the sheilds block sensors (or where you would place the sensors) then the problem is neutralized. Then it just becomes a question of why they don't make them small enough to extend beyond the shields, and there you can wave it away by citing sensor tech limits.

Okay, but the sensor tech limits have to be plausible. And consistent with any canon statements about neutrino detection.

I suppose its possible they collaminate it into a beam

No, I don't think it is possible. We'd better ask someone whose physics background is in thermodynamics rather than electromagnetism,

*raises hand* AFAIK Mike and I have had the most training on the subject; though mine was abbreviated and more focused on what was relevent to nuclear reactors rather then thermodynamics on the whole.

Well, my physics training was aimed at making me an electrical engineer (except for second-year Modern Physics, which I did for fun). So you're ahead of me.

I raised this point a little over a year ago in discussion and the response was basically a big "I dunno". I'm thinking of writing a university that runs a neutrino generator and asking about their machine, but I'm not sure if those ae omni directional or focused.

Please do. I will be very interested in learning about it if a highly anisotropic beam of neutrinos is not very low-entropy.

but I have a strong suspicion that such a beam would represent a lot of energy at very low entropy. In other words this would violate the Second Law of Thermodynamics.

I think it might depend on how it is done. Consider, a flashlight is an omnidirectional release of light that is turned into a beam by cupping it in a mirror. The light that hits the mirror is reflected out so it only comes out through the opening.

Yes, and näively one might think (I used to) that this represented a way to turn waste heat into useful energy (a beam weapon, or at least a serachlight). But in discussions on the usenet group rec.arts.sf.science I was told by people who sounded as though they knew what they were talking about that it in not possible to run even an IR searchlight on waste heat. Apparently an anisotropic flood of radiation has low entropy, so that it costs energy to concentrate it into even a spreading conical beam. I never saw a detailed argument, but several of the more rational-seeming posters quoated a result that confining the radiation of waste heat to pi steradians of sky was in principle possible only as a limit with an emitter of infinite size and with zero efficiency.

I figure that you are in a better position than I am to discover whether that is true and whether the principle applies to neutrinos as well as to photons. But if you would prefer to stick to the formalities of debating I guess I could eventually ferret out the facts.

Now we don't know if shields, assuming they are opaque to neutrinos, absorb them, or scatter them.

They must scatter of reflect them, I think. If shield absorbed neutrinos there ought to be a way to use shields themselves as neutrino-detectors. Especially considering the flux intensities we are talking about here.

They might possibly concentrate it into a cone, and point the cone away from know enemy sensors, I suppose. But I thinki thermodynmics requires that this would cost energy, and sets a fairly broad lower limit on the width of the cone.

Indeed. I have seen a few references to "neutrino lasers", I need to dig deeper.

You can't run a laser on waste heat. I would be very, very surprised if you could do so with a neutrino laser, because if you could you could use the neutrino laser to heat a target to a temperature higher than your engine, which is a definite no-no.

Exhaust you should get scattered gamma flashes from collisions, particularily when it is turning. But you need not get thermal reading from the exhaust plumes. I can have an ice cube moving at .99 C afterall.

Only if the process you use to accelerate the icecube is godawful efficent.

Lets say I toss it out the airlock. This was meant solely as an example.

Well, if you toss it out the airlock it won't be a very efficient rocket exhaust. To be an efficient rocket exhaust it needs to have a very high velocity compared to the ship.

Besides which, kinetic energy tends to degrade to heat. I expect that an icecube whipping through the interplanetary medium at 0.99c is going to heat itself by friction, and explode into a puff of incandescent vapour. Lets say that the interplanetary medium consists of five million hydrogen attoms per cubic metre. The cross-sectional area of the icecube will sweep out 3E8 cubic metres per square metre per second, so from the point of view of the icecube the interstellar medium is a beam delivering 1.5E15 hydrogen atoms per square metre per second. At 0.99c those atoms have a kinetic energy of (gamma-1)mc^2. Gamma is 6.08 we calculated before. The mass of a hydrogen atom is about 1.7E-27 kg. c^2 is 9E16. That's 1.4E6 Wm^-2, which is about a thousand times as bright as sunshine. It will evaporate 700 metres of ice a second.

Dude, you are digging ay too deep. My only point was that there is a major difference between kinetic energy and thermal energy and that one can have a high kinetic energy with a low thermal energy.

You can. But not, I contend in the exhaust plume of a rocket unless either the exhaust velocity is low or the engine is implausibly efficient.

Temperature is relative, and a low temperature is going to have very little emissions.

No, temperature is an absolute.

No. Don't let the term "absolute zero" fool you. Temperature is the average random molecular kinetic energy of a substance. Kinetic energy is proportional to velocity, and velocity is relative.

I think we are drifting off on a tangent here. But I don't think this is right. The heat of a parcel of molecules is the energy of their random motion with respect to their collective centre of mass, not the whole of their kinetic energy. The velocity of each molecule is decomposible into the velocity of the centre of mass with respect to the observer and the velocity of the molecule with respect to the centre of mass. The square of the first (times half the mass of the molecule) is that individual molecule's share of the kinetic energy of the parcel, the square of the second (times half its mass) its that molecule's share of the heat. I recoil from teh relativistic case, but I think it is pretty easy to see that under the Galileian transformations the total heat of the parcel is independent of frame of reference.

Even in experiments on earth where they try to stop all motion in a substance to get it to absolute zero, the slow down is only realitive to the instruments as the substance is still moving at great velocity as earth orbits the sun.

Yes, of course. But that is not random thermal motion. The collection of supercooled atoms has high kinetic energy in the Sun's frame of reference, but not high heat.

In short, thermal energy depends not on a single velocity (that of the molecule) but on the difference between velocities (that of the molecule and that of the centre of mass of the object it is part of). Vector algebra assures that this difference is the same vector if the same vector is added to both.

And by the way, in every case except that of monatomic gases, some of the thermal energy is stored in rotational and vibrational modes, which are not relative.

If I had a magic device that let me measure the temperature of that substance from the moon I would get a different reading because the molecules would be moving at a different velocity relative to my instruments.

Well, rather than using a magical instrument, let's imagine that we calculate the heat of the object by observing the spectrum of its thermal radiation. The emitivity to an depends on its composition, and ought to be the same in all frames of reference, right? And the thermal emissions depend on the emitivity and the temperature. So we ought to be able to determine the temperature of an object by finding the peak of its thermal emission spectrum. Now, the object emits real photons, and different observers must surely agree on what photons are emitted. They can only disagree about their wavelength because of the Doppler effect. The thermal spectum of an approaching object will be 'warmed', but that of a retreating object 'cooled', even though both have more kinetic energy.

There is a real difference between the kinetic energy of an object and its thermal energy. The second causes violent collisions between its molecules and leads to thermal radiation. The first does not. It is absolutely true that an object radiates particular photons as a result of its temperature. These photons are characteristic of the object's temperature. And therefore temperature is absolute.

We can look at this another way, by considering two objects with relative motion, as a wheel A rotating inside an evacuated shell B. An observer on object A performs experiments with the vapour pressures of various liquids, and determines that A is at the temperature of the triple point of water. B does the same, and determines that B is at the triple point of water. Now we go an determine whether heat actually flows from A to B or from B to A (by radiation). They can't both get hotter and they can't both get cooler. Either they both rmaintain a constant temperature (in which case they were both the same temperature to begin with) or one heats and teh other cools. But if one heated and theother cooled we would be able to determine which one was really moving and which really stationary, which would violate the postulate of relativity.

(Okay, perhaps a rotation wasn't a very good example, because you can detect that. Let's make A and B infinitely long, infinitely wide, thin plates ver close to each other, and each determined in its own frame of reference to be at uniform temperature are teh triple-point of water.

The tracers on the weapons

Actually, I was not thinking so much of the glow of the bolts. I was thinking in terms of incandescent wreckage from the targets.

Are you thinking of this from a neutral planetary observer position?

I hadn't thought specifically about who the observer was. Somebody (Darth Wong, I think) specified the scenario of an ISD accelerating at full bore and firing all possible weapons, and I immeditely thought that the weapons fire must be hitting something, even if it were only the interplanetary medium.

[Agemegos]

That's not what Agemegos is saying. A passive sensor will see the neutrinos and IR passing through the shield on the way out. Such a shield would only block active sensors (which work by emitting something and sensing the return of an object) by absorbing the emission. However, since the ship itself must emit the neutrinos and infrared radiation through the shield to eliminate the heat, a passive IR or neutrino sensor would be able to see the radiation coming off the vessel.

No, because the incoming neutrinos and IR from the other ship would be stopped by the shield before it got to the sensor.

Ghetto diagram-

----- > | (

--- is neutrinos, > is the scatter from them hitting the shield, | is the shield, ( is the sensor.

There doesn't have to be a shield around the sensor. The only shield that you can guarantee exists is that of the ISD, and that has to let the neutrinos out.

[Agemegos]

I'm sick and tired of people always saying battlecruisers went up against battleships at Jutland.

Well, evidently I have been taken in by the flood of misinformation.

[Winston Blake]

No, because the incoming neutrinos and IR from the other ship would be stopped by the shield before it got to the sensor.

Ghetto diagram-

----- > | (

--- is neutrinos, > is the scatter from them hitting the shield, | is the shield, ( is the sensor.

There doesn't have to be a shield around the sensor. The only shield that you can guarantee exists is that of the ISD, and that has to let the neutrinos out.

This misunderstanding has wandered on too long. The situation as i understand it:


"The shields block the neutrinos."

1. Ender's proposal.

• Ship A is floating in space, emitting neutrinos which pass out through its shields.
  
  Ship B with its shields down and a neutrino detector onboard can detect the neutrino emissions of Ship A.
  
  Ship C with its shields up cannot detect the neutrino emissions of Ship A because its own shields are blocking their entry, just like they block the entry of enemy turbolaser bolts.
  
  This blocking of neutrinos is part of the fundamental nature of shields. Further, ships keep their shields up when expecting to be attacked.

2. Agemegos's misunderstanding:

• Ship A is floating in space, emitting neutrinos which are blocked by its own shields, resulting in the shield-ship system heating up and frying everybody inside, apparently invalidating Ender's proposal.
  
  Hence:
  
  Ship A is floating in space, emitting neutrinos which pass out through its shields, apparently in contradiction to Ender's proposal.
  
  Ship B detects the neutrino emissions of Ship A, thus making passive locating of Ship A easy.

All of which means nothing if ISDs don't even care about being located.


Other points:

• Sensors could poke outside the shield, or small holes in the shield could be opened at will for the sensors to see out.
  
  ISDs would only use full power (and hence produce max neutrinos) in a combat situation, when subtle locating isn't useful anyway.

[NRS Guardian]

Well, evidently I have been taken in by the flood of misinformation.

That's ok I was more frustrated by the misinformation and its repetition. Especially since I don't understand how it could have started, unless people just think battleships at Jutland equals dead battlecruisers.
Also, the battlecruiser design philosophy is better summed up as out-range what you can't out-run, because the primary advantage of battleship guns on battlecruisers is they out-range cruisers and the smaller-gunned German battlecruisers.
Ideally a British battlecruiser will try to hit without being hit back. Poor gunnery training, bad lighting, wind blowing smoke from their own guns at them, and running into range of their German counterparts before they realized it meant the avoidable deaths of two battlecruisers. Hood and the Invincible died later, but on nearly equal terms with the Germans, also managed to take out the battlecruiser Lutzow.