Gravity-based sensors

[Jedi Master Spock]

Given that terms such as "anti-photons" and "gigawatts of particle energy" are used, relying on dialog being technically accurate may not be wise. (The question Spock was answering may have been somewhat of a trick question, given that it was referring to "anti-gravitons" in the first place.)

There are technical dialogue bugaboos that we can't explain, but in general, the question on Spock's screen fits with what little else we know about their technology.

Including vibrations due to people walking around? If the internal sensors had this level of detail, nobody could ever hide while on a starship.

Vibrations of the ship due to people walking around (and banging on the wall, etc) tend to occur at particular known ranges of frequencies. Really, it's not that hard to filter out the vibrational motion of the sensors - you don't even need to know what exactly the vibrational noise "looks" like before you send it through the filter. For the vast majority of the vibrational noise you'll get? Fourier transform, zero the noisy bits, inverse Fourier transform, done.

There's a strong implication that gravimeters aren't used for [a primary method of] detecting masses in TNG's "The Survivors," however. A ship that appeared out of nowhere was assumed to have been hiding in a Lagrange point.

If the Enterprise were equipped with with gravimeters as sensitive and precise as you would require to get around the interference I have mentioned, then a ship could not hide in a Lagrange point, because its own gravity well would not be affected by the Lagrange point. The suggestion that a ship could hide in one would be outright silly with sensors that capable.


Direct graviton detection would have the same problem: the gravitons being emitted by the starship would not be affected by simply originating from an L-point, so again the suggestion would be very silly.

The problem with gravimetric sensors when you have gravimetric shielding is that a source can also be shielded from you. (I hadn't brought this up before. It creates all kinds of complications related to cloaking.)

There are some really quirky things associated with Trek sensors failing to see things (e.g., the magnetic pole issue) which make as little sense as tracking interstellar hydrogen in realtime in "The Battle."

However, the bit about the Langrange point is actually well taken.

Think about it carefully for a minute, going back to what I said about filtering out predictable bodies. L4 and L5 points are stable equilibria and tend to collect matter (most famously the Trojans). Accordingly, if you wandered in-system and picked up a million ton blip sitting more or less stationary in the Lagrange point, you would assume it was part of the random collection of debris normal to such points and discount it accordingly.

If anything, reliance on gravitic sensors would help explain why the Langrange points can be a hiding spot - of all the kinds of sensors, gravitic sensors are the most likely to ignore a ship sitting in a loose cloud of dust and asteroids. A ship is usually optically very distinct from loose clouds of dust with the occasional larger rock.

And the amount of work is completely unnecessary if gravimeters are being used, because the effects of gravitation can be detected FTL.

The only way you can detect gravitation "FTL" is if you're invoking some kind of subspace transmission component. Gravity propagates at c.

Then what is the range of the system?

Depends on how much resolution you have. In general, range at which you can fix an object is a particular variety of the basic parallax problem.

And how do you handle two starships near each other? Your sensors will, at best, only see a single blip because the gravity is pulling to the center of mass of the system.

Two ships near each other ("near" relative to the angular resolution of the system) moving similarly will often be resolved as a single source, yes.

The alternative to phantom blips appearing and disappearing to fit the data would be a margin of error listed for each detected object.

A MOE for distance, position, and mass, yes. That's how it would be for any sensor system.

[Keiran]

There are technical dialogue bugaboos that we can't explain, but in general, the question on Spock's screen fits with what little else we know about their technology.

So the Federation has the ability to create a perpetual motion machine?

Blocking gravitons as you describe would allow a violation of Conservation of Energy. If an object previously on the ground is given x KE going "up" (and converted to an equal amount of potential energy when it reaches the peak of its ascent) and it will then have x KE when it reaches the ground again.

However, with the ability to block gravity, an object given x KE can continue to move away from the gravity well without losing KE. Once the object is in the gravity well again, however, it will begin to lose KE. However, when it reaches the surface again, its KE will be greater than the original KE.

Where did this energy come from?

The problem with gravimetric sensors when you have gravimetric shielding is that a source can also be shielded from you. (I hadn't brought this up before. It creates all kinds of complications related to cloaking.)

And perpetual motion devices...

There are some really quirky things associated with Trek sensors failing to see things (e.g., the magnetic pole issue) which make as little sense as tracking interstellar hydrogen in realtime in "The Battle."

A reliance on subspace sensors could explain it, if subspace is affected by gravity and electromagnetic fields in ways that could cause interference.

However, the bit about the Langrange point is actually well taken.

Think about it carefully for a minute, going back to what I said about filtering out predictable bodies. L4 and L5 points are stable equilibria and tend to collect matter (most famously the Trojans). Accordingly, if you wandered in-system and picked up a million ton blip sitting more or less stationary in the Lagrange point, you would assume it was part of the random collection of debris normal to such points and discount it accordingly.

If anything, reliance on gravitic sensors would help explain why the Langrange points can be a hiding spot - of all the kinds of sensors, gravitic sensors are the most likely to ignore a ship sitting in a loose cloud of dust and asteroids. A ship is usually optically very distinct from loose clouds of dust with the occasional larger rock.

Relying on gravimeters to that extent would be silly. Gravimeters would be much more useful when used in conjunction with easier methods of detecting distance and mass.

Once you use more reliable sensors (i.e., sensors that don't require the elaborate workarounds you've mentioned thus far) to determine the main sources of mass, then gravimeters can show any anomalies that the other sensors may have missed. (We know they can detect the mass of starships using FTL sensors, for example.)

Besides, at range, a planet, its moon, and its moon's L2 point would show as a single blip. (All the gravimeters on your ship will point to the center of mass of the system.) A starship could "hide" from a starship using only gravimeters by simply being in orbit. (At a light-minute away, the starship's gravitational pull would be orders of magnitude less than the diameter of an electron (per second squared).) In this situation, hiding in a Lagrange point is meaningless.

So over-reliance on gravitics isn't a good option. They'd have to acquire information through other means before they could even speculate on whether something was hiding in the Lagrange point or not. (And, as you said, a starship should look quite a bit different from the objects normally found there.)

The only way you can detect gravitation "FTL" is if you're invoking some kind of subspace transmission component. Gravity propagates at c.

Yes, I know. In addition, we're talking about detecting movement due to gravity of less than the diameter of an electron for anything at any decent range. If they can detect this gravitational pull via subspace sensors (where it'd be even substantially less than that), then why bother with the realspace version even at close range?

A MOE for distance, position, and mass, yes. That's how it would be for any sensor system.

I'm saying it'd be greater for gravimeters due to the greater levels of interference mentioned. (Things that wouldn't be a problem for optics, for example.)

[Jedi Master Spock]

So the Federation has the ability to create a perpetual motion machine?

Blocking gravitons as you describe would allow a violation of Conservation of Energy. If an object previously on the ground is given x KE going "up" (and converted to an equal amount of potential energy when it reaches the peak of its ascent) and it will then have x KE when it reaches the ground again.

However, with the ability to block gravity, an object given x KE can continue to move away from the gravity well without losing KE. Once the object is in the gravity well again, however, it will begin to lose KE. However, when it reaches the surface again, its KE will be greater than the original KE.

Where did this energy come from?

A similar COE problem crops up with the mass lightening of warp fields. It's all related, isn't it? It's actually a combination of the mass lightening COE problem and the problem of going to warp deep in gravity wells which forces Trek ships to have such high peak power generation figures.

IMO, Star Wars antigrav (cited to work only within proximity to planetary gravity wells IIRC) probably invokes a similar directional shielding principle somewhere along the line to "bounce" gravitons from the planetary well. Actually, since Lucas likes to use the term "magnetic" for levitation, we can pretty reasonably assume a shared principle at work for a VS scenario.

The short answer is that if we are to preserve COE, creating an envelope that blocks gravitons is not a "free" process, nor is moving it around or moving something into its "shadow."

A reliance on subspace sensors could explain it, if subspace is affected by gravity and electromagnetic fields in ways that could cause interference.

Relying on gravimeters to that extent would be silly. Gravimeters would be much more useful when used in conjunction with easier methods of detecting distance and mass.

Once you use more reliable sensors (i.e., sensors that don't require the elaborate workarounds you've mentioned thus far) to determine the main sources of mass, then gravimeters can show any anomalies that the other sensors may have missed. (We know they can detect the mass of starships using FTL sensors, for example.)

Besides, at range, a planet, its moon, and its moon's L2 point would show as a single blip. (All the gravimeters on your ship will point to the center of mass of the system.) A starship could "hide" from a starship using only gravimeters by simply being in orbit. (At a light-minute away, the starship's gravitational pull would be orders of magnitude less than the diameter of an electron (per second squared).) In this situation, hiding in a Lagrange point is meaningless.

Depends how close you are. The problem is mainly angular resolution, and the fact that the ship is behaving just like an inert rock.

As I may have mentioned, though, the direct graviton detection method has a much easier time and basically amounts to an open and shut case.

So over-reliance on gravitics isn't a good option. They'd have to acquire information through other means before they could even speculate on whether something was hiding in the Lagrange point or not. (And, as you said, a starship should look quite a bit different from the objects normally found there.)

Nobody is saying that gravitational sensors are the be-all and end-all of sensor systems. Federation ships in particular are notorious for being designed as "explorers" with all sorts of different methods of measuring things.

Yes, I know. In addition, we're talking about detecting movement due to gravity of less than the diameter of an electron for anything at any decent range. If they can detect this gravitational pull via subspace sensors (where it'd be even substantially less than that), then why bother with the realspace version even at close range?

Who says gravity is less in subspace? I'm not going to commit to that without brushing up on the warp metric, and IMO, neither - unless you're an expert geometer working in the field - should anyone else make that claim without doing some careful fact-checking first. And that's assuming that it's appropriate to apply, which is a pretty big assumption.

And yes, the sensitivity level involved for significant ranges with this sort of thing is pretty ridiculous.

I'm saying it'd be greater for gravimeters due to the greater levels of interference mentioned. (Things that wouldn't be a problem for optics, for example.)

Optical systems do have their uses, but they also have their own problems. Gravitics have some advantages (think about why you see CGTs used in Star Wars, and think about obscuring objects/phenomena in the way - which gravity penetrates straight through unimpeded - and then think of the problem of trying to measure mass without a detailed composition scan through the object) and some disadvantages (difficult to design and use, generally poorer resolution than similarly sized arrays of optical sensors).

In general, having working gravitic sensors is something I would call a big plus. It adds some very useful information.

[SailorSaturn13]

Given that terms such as "anti-photons" and "gigawatts of particle energy" are used, relying on dialog being technically accurate may not be wise.

Problem is, we don't know their physics. It' obviously slightly unlike ours, allowing for example ships to buzz in space.

"antiphotons", for example,. could be some strange objects that annihilate photons, OR just photons in counterphase to ones they expected.

However, with the ability to block gravity, an object given x KE can continue to move away from the gravity well without losing KE. Once the object is in the gravity well again, however, it will begin to lose KE. However, when it reaches the surface again, its KE will be greater than the original KE.

Where did this energy come from?

Obviousli, the shielding has to provide it, just like by beaming.

[Who is like God arbour]

I've learned a short time ago, that the M-theory [1], wich has unifies the five superstring theories [2], states, that there are 11 dimensions [3] in our universe and infinite other univeres parallel to our universe. One conclusion of this M-theory is, that gravitation don't has to be the smallest fundamental interaction. It is more pronounced in some of the other dimensions and could even be leaking in the other universes [4].

Could it be, that in subspace, gravitation is more pronounced than in real space or that the UFP is able to scan the gravitation in the dimensions, which we can't experience?

[Keiran]

A similar COE problem crops up with the mass lightening of warp fields. It's all related, isn't it? It's actually a combination of the mass lightening COE problem and the problem of going to warp deep in gravity wells which forces Trek ships to have such high peak power generation figures.

IMO, Star Wars antigrav (cited to work only within proximity to planetary gravity wells IIRC) probably invokes a similar directional shielding principle somewhere along the line to "bounce" gravitons from the planetary well. Actually, since Lucas likes to use the term "magnetic" for levitation, we can pretty reasonably assume a shared principle at work for a VS scenario.

The short answer is that if we are to preserve COE, creating an envelope that blocks gravitons is not a "free" process, nor is moving it around or moving something into its "shadow."

With mass-lightening, we can talk about energy moving in/out of subspace and costs associated with the transitioning.

We have no such comfort when talking about blocking gravitons. There is no mechanism for the graviton blocker to gain/lose energy as objects potentially lightyears away move towards and away from the gravity well while in the "shadow."

Because blocking gravitons as such would violate the first law of thermodynamics, we can conclude that outright blocking of gravitons is impossible.

Now, there are ways to make the ST4 quote work. One possibility is that the question is worded strangely on purpose (it does use the word "anti-gravitons" when gravitons may be their own antiparticle), and the real goal is to modify the envelope so that the current gravitational pull is countered.

Whatever the explanation, the same conclusion can be reached: whatever happens inside the field, gravity must be normal outside of the field. The consequence is that graviton shielding cannot be used to assist gravimeters. (If the gravimeter is outside graviton shield, then it receives gravity as if the shield didn't exist. If it is inside the graviton shield, then it can't measure gravity.)

Depends how close you are. The problem is mainly angular resolution, and the fact that the ship is behaving just like an inert rock.

Behaving like an inert rock with a gravitational influence on a gravimeter of less than diameter of an electron (and much less than the random movements of electrons in the atoms making up the sensor). I don't see any reason to believe that Federation sensors are capable of this level of sensitivity for gravimeters.

As I may have mentioned, though, the direct graviton detection method has a much easier time and basically amounts to an open and shut case.

It's not a proven capability for Trek sensors, though. We know that Federation sensors can detect graviton activity.

That's it.

We don't know how they do it. We don't know how much detail the sensors receive. We don't know if they can detect the vectors of individual gravitons.

The examples of graviton detection given in this thread are all explainable with radar and/or optics to determine distance, whatever subspace sensors can detect determine mass FTL, and gravimeters detecting unexpected gravity sources or changes in gravity after the already known sources have been compensated for.

Nobody is saying that gravitational sensors are the be-all and end-all of sensor systems. Federation ships in particular are notorious for being designed as "explorers" with all sorts of different methods of measuring things.

Perhaps we're starting to agree... I can't really tell. My position, as I've stated before, is that gravimeters have too many inherent problems and limitations to be used as a practical primary sensor, and are best used as auxiliary sensors to see if the primary sensors missed anything. (With less data to sift through, anomalies can appear much more easily.)

Who says gravity is less in subspace? I'm not going to commit to that without brushing up on the warp metric, and IMO, neither - unless you're an expert geometer working in the field - should anyone else make that claim without doing some careful fact-checking first. And that's assuming that it's appropriate to apply, which is a pretty big assumption.

That's not what I meant. I wasn't talking about gravity in subspace, I was talking about the gravity that would be detected using realspace sensors being much, much less at the distances that require the use of FTL sensors.

And yes, the sensitivity level involved for significant ranges with this sort of thing is pretty ridiculous.

Enough that it'd be impractical outside of theory under ultra-ideal conditions. (Except at short range, at least as far as starship detection is concerned.)

Optical systems do have their uses, but they also have their own problems. Gravitics have some advantages (think about why you see CGTs used in Star Wars, and think about obscuring objects/phenomena in the way - which gravity penetrates straight through unimpeded - and then think of the problem of trying to measure mass without a detailed composition scan through the object) and some disadvantages (difficult to design and use, generally poorer resolution than similarly sized arrays of optical sensors).

Optics were just an example, of course.

And CGTs are rare in Star Wars.

In general, having working gravitic sensors is something I would call a big plus. It adds some very useful information.

Oh, they definitely have their uses.

[Keiran]

Why would they say again and again gravitons, if they would only mean gravitation?
If they wouldn't be able to detect gravitons directly, it wouldn't be necessary to refer to gravitons instead of gravitation. Quite the contrary, it would be misleading.
To know theoretical, that gravitation is caused by gravitons, is useless knowledge, as long as the gravitons are not detectable.
We don't call a lamp a photon emitter or light a photon beam. We speak of photons only if we really mean photons.
They wouldn't have a reason to call something a gravtion-(field)-generator or graviton-emitter, if all they know is, that this generator or emitter creates gravitation, which is theoretical caused by gravitons.
That's why in my opinion, we can assume beyond a reasonable doubt [1 / 2], that they mean gravitions and not only gravitation, which is caused by gravitons, when they refer to gravitons and not only to gravitation.

I disagree. First, Star Trek is known for using overly-complicated dialog for relatively simple things.

Second, particles are detected by the interaction they make with their environment. If gravitons are accepted to exist by the Federation, then detecting gravitation means the same thing as detecting gravitons, because gravity cannot exist without gravitons in Star Trek.

That's what I don't understand. If there would be a ship, you would, as you have partially admitted, at least get a vector only with the gravimeters, on which along the ship have to be.

You would know, that there would have to be something, what your other sensor-systems can't detect (maybe a cloacked ship?).

If you would change your own position in relation to this vector, you would get a new vector to the ship (assuming, that it hasn't changed its course).

Both vectors would cross with each other. The ship would have to be at this point. Now, you have its position at this moment.

In German, we call this method "Triangulieren". I couldn't find a matching Englisch term. But I assume, that you know this method. It could be done with two or more ships at the same time or if two gravimeters on one ship are far enough away from each other, with one ship at the same time.

I don't understand, why this should be impossible.

Triangulating is easy when you only have one source, but when you have multiple unaccounted for sources of gravity, triangulation isn't so simple.

You have an unknown number of gravity wells, and each one is moving and accelerating on its own (from gravity, if nothing else). Each gravimeter on your ship will be pointing in a particular direction (generally they will all have roughly the same vector).

Now, even after observing for a period of time, you will still have any number of possible solutions to the problem (remember: you don't know how many unaccounted for gravity sources you have).

If anyone can find an algorithm (a specific one, not vague) that can give a solution for an assumed number of masses, then we can more easily confirm or deny this.

As it is to read, the Enterprise and the Crystalline Entity were at warp speed and up to five lightyears away from each other. Nevertheless the Silicon Entity was able to detect the graviton beam from the Enterprise.

It was a graviton beam and not only a gravitation-wave or a wave in subspace, caused by a gravitation wave in real space. I think - and have argued at SDN - that we have to assume, that the gravitons, fired in subspace, propagate with high warp-speed because they don't leave subspace unless they collide with an object - in this case, the Crystalline Entity or maybe after some time, in which they could have become slower. Otherwise the gravitons would have never reached the Crystalline Entity.

Ok, so maybe these gravitons did stay in subspace.

To corroborate my these, I have refered to the TNG episodes "Chain of Command", in which was seriously dicussed the possibility to launch dormant metagenic material on a subspace carrier wave and the TNG episode "New Ground", in which a whole ship was transported through subspace by a carrier subspace wave, the soliton wave.

Metagenic material would consist of complex biological molecules and a whole ship a fortiori too (OK, no biological molecules for the ship unless it is a biological ship.). But gravitons are only elementar particles. Therefore I think, it would be far easier to send such elementar particles, which have no mass and can't be ruptured through subspace, than heavy complex biological molecules, which are held together only by molecular bonding forces.

I have argued, that the first could be therefore already in common use while the latter, which would be far more difficult, was only in a test phase.

Firing gravitons in subspace would be useless as a sensor, though: there's no data to receive.

[Keiran]

slightly off top, but the best way for warp would be sending gravitons via subspace to create a pulling channel - which pulls the ship forward supraluminal.

Gravity can't pull something FTL. And sending gravitons ahead of you won't pull you to anything, you have to have something sending gravitons to you.

If gravitons exist, then they have wave properties, too. They not only pull, they also bend space and create forward-backward movement.

The important formulas are: the closer to object, the more energy each graviton has (slower vibrations).
And the direction of gravitons gives us a vector to target.
Detecting vector is easy: jst build long , small tube which blocks gravitons in walls and the only gravitons coming through (to detector) are in correct direcition

Blocking gravitons causes a violation of Conservation of Energy. That's not something we call "easy." Or even "hard." "Impossible" is the word of choice here.

And given they can emit gravitons by random (shields) it is likely they do know more intractions.

Even if that's true, that doesn't mean those interactions can give the information necessary for individual graviton detection.

Problem is, we don't know their physics. It' obviously slightly unlike ours, allowing for example ships to buzz in space.

"antiphotons", for example,. could be some strange objects that annihilate photons, OR just photons in counterphase to ones they expected.

A photon is its own antiparticle. Photons do not interact with each other, so photons do not annihilate each other. And Voyager was transmitting them.

Obviousli, the shielding has to provide it, just like by beaming.

That doesn't work, there's no way for the hypothetical graviton blocker to transmit/receive energy to/from objects of arbitrary an distance.

[Jedi Master Spock]

With mass-lightening, we can talk about energy moving in/out of subspace and costs associated with the transitioning.

We have no such comfort when talking about blocking gravitons. There is no mechanism for the graviton blocker to gain/lose energy as objects potentially lightyears away move towards and away from the gravity well while in the "shadow."

No, it's exactly the same thing.

Did I mention that if you lighten mass, the entire universe is in the "shadow"? Objects light years away will be moving towards and away from whatever you lightened in every direction, gaining and losing energy all the while with respect to whatever you lightened. Conservation laws are OK with gravitons being blocked, filtered, or whatever else... so long as the blocking agency accounts for the change in energy.

It's a messy problem, sure - and you may wish to invoke "subspace" effects to try and provide an elegant explanation - but it doesn't get any different from a lightening field to a blocking field.

Because blocking gravitons as such would violate the first law of thermodynamics, we can conclude that outright blocking of gravitons is impossible.

Try again. You still haven't found a good explanation as to why it would necessarily violate conservation. It's really quite a simple problem, and quite symmetric in its applications both directionally and non-directionally. Remember, gravity is always mutual and symmetric.

Perhaps I should talk some about the motivation for invoking quanta of gravitation in the first place and the general properties of particles in systems of particles? That may help, gravity is still a very messy field of study.

Now, there are ways to make the ST4 quote work. One possibility is that the question is worded strangely on purpose (it does use the word "anti-gravitons" when gravitons may be their own antiparticle), and the real goal is to modify the envelope so that the current gravitational pull is countered.

That interpretation has no grounding. The question of graviton vs anti-graviton relevant to the use of the term "block" rather than "generate a cancelling field."

Behaving like an inert rock with a gravitational influence on a gravimeter of less than diameter of an electron (and much less than the random movements of electrons in the atoms making up the sensor). I don't see any reason to believe that Federation sensors are capable of this level of sensitivity for gravimeters.

For the record, the diameter of the electron is not a unit of force or energy - nor is the level of energy at which it starts to be appropriate to start talking about gravitons as particles very high. Nor, for that matter, is it usually appropriate to talk about the "diameter" of an electron, as it is generally a non-localized object due to uncertainty. (In practical terms, the "diameter" of an electron is its orbital, i.e., ~10^-10m.) Of course, we can otherwise talk about an electron as having a diameter of 10^-14m - much like a proton or neutron, which don't have the problem of never being still enough to measure carefully.

It is very easy for us in the modern age to detect individual photons of the order of energy of single electron-volts, i.e., the order of 10^-19 joules.

It's not a proven capability for Trek sensors, though. We know that Federation sensors can detect graviton activity.

That's it.

We don't know how they do it. We don't know how much detail the sensors receive. We don't know if they can detect the vectors of individual gravitons.

The examples of graviton detection given in this thread are all explainable with radar and/or optics to determine distance, whatever subspace sensors can detect determine mass FTL, and gravimeters detecting unexpected gravity sources or changes in gravity after the already known sources have been compensated for.

We don't know beyond any doubt - but it is strongly suggested. (E.g., identifying a series of graviton pulses "from X" strongly suggests either directionality of detection or the sort of extraordinarily sensitive gravimeters described.

Nor is it suggested in any way that some form of "subspace" sensors detect mass magically. Observation of gravity and its effects is the only method IRL to directly detect the mass of an object external to your control, and is the most extensively used one. (We rarely measure inertial mass directly.)

Perhaps we're starting to agree... I can't really tell. My position, as I've stated before, is that gravimeters have too many inherent problems and limitations to be used as a practical primary sensor, and are best used as auxiliary sensors to see if the primary sensors missed anything. (With less data to sift through, anomalies can appear much more easily.)

We are in some ways. At the same time, mass patterns are important enough to detailed scans that I would count that as one of the more important sensor systems.

Most of the time in Trek, we have no idea what combination of sensor systems - optical, gravitic, or various flavors of unknown systems - was involved in resolving data.

Essentially speaking, we have only a handful of fundamental forces to appeal to in constructing sensors. We can detect magnetic fields, electrical fields, or combinations thereof; we can detect gravitational fields; we can also make guesses about particles with mass from their interactions with other matter.

In Trek, we presumably have some mysterious "subspace force" to contend with, but I prefer not to invoke it when it isn't suggested or required.

Enough that it'd be impractical outside of theory under ultra-ideal conditions. (Except at short range, at least as far as starship detection is concerned.)

But then, so is tracking interstellar hydrogen displaced by a warp speed vessel. "Impractical" is a problematic term when faced with the evidence.

As far as "short range" goes, I don't see any evidence of very detailed scans being carried out past a few light seconds at most, and in general the most detailed information may easily be restricted to about 40,000 km (transporter range). You can call this short range (you've been using the idea of detecting an individual ship at a light minute), but it's really not very short range. Tactical range for Trek ships is on the order of a light second against other moving ships, after all.

Our ideas of what makes a useful base measurement case are separated by 3 orders of magnitude here.

[Keiran]

No, it's exactly the same thing.

Did I mention that if you lighten mass, the entire universe is in the "shadow"? Objects light years away will be moving towards and away from whatever you lightened in every direction, gaining and losing energy all the while with respect to whatever you lightened. Conservation laws are OK with gravitons being blocked, filtered, or whatever else... so long as the blocking agency accounts for the change in energy.

It's a messy problem, sure - and you may wish to invoke "subspace" effects to try and provide an elegant explanation - but it doesn't get any different from a lightening field to a blocking field.

What are the effects of mass lightening? As far as I'm aware, the gravity well of a mass-reduced object isn't confirmed to have changed. If that's the case, then there's no "shadow." Then we just modify the potential energy of the mass-reduced object by transferring what we need to/from subspace (since the AMRE is linked to subspace anyway).

Meanwhile, we still have no way of giving an object the required potential energy while it floats away from the gravity well that would otherwise be pulling it in.

Try again. You still haven't found a good explanation as to why it would necessarily violate conservation. It's really quite a simple problem, and quite symmetric in its applications both directionally and non-directionally. Remember, gravity is always mutual and symmetric.

Perhaps I should talk some about the motivation for invoking quanta of gravitation in the first place and the general properties of particles in systems of particles? That may help, gravity is still a very messy field of study.

Um, because energy can appear out of nowhere.

Let's say you have a bowling ball and throw it up at a slight angle. You've given the ball x KE. When it reaches the peak of its ascent, it will have x potential energy. Just before it reaches the ground again, it will have x KE (neglecting air resistance).

Now let's say you have a graviton-blocking plate on the ground, and you're standing next to it. Now throw that bowling ball up into the "shadow." You will have given it x KE. When it hits the ground, it should have, at most, x KE. But now it's going up and not receiving any potential energy (it's not moving against a gravity field and there's nothing between the plate and the ball to transfer energy). When the ball leaves the "shadow," it starts gaining potential energy and losing kinetic energy until it reaches the peak, then gains KE again as it falls, eventually gaining more KE than it started out with.

Again, we've just created a perpetual motion machine. Just keep throwing bowling balls up and have them move a generator when they land. There's nothing in the system that is losing an equivalent amount of energy for the gained KE, so CoE is violated.

It's fairly simple.

That interpretation has no grounding. The question of graviton vs anti-graviton relevant to the use of the term "block" rather than "generate a cancelling field."

So a violation of thermodynamics is somehow preferable to a trick question on a quiz for an explanation?

For the record, the diameter of the electron is not a unit of force or energy - nor is the level of energy at which it starts to be appropriate to start talking about gravitons as particles very high. Nor, for that matter, is it usually appropriate to talk about the "diameter" of an electron, as it is generally a non-localized object due to uncertainty. (In practical terms, the "diameter" of an electron is its orbital, i.e., ~10^-10m.) Of course, we can otherwise talk about an electron as having a diameter of 10^-14m - much like a proton or neutron, which don't have the problem of never being still enough to measure carefully.

Let's not nitpick the trees too closely, there's a forest here: you're trying to measure something that's less than the random fluctuations found in atoms. A neat trick, yes?

We don't know beyond any doubt - but it is strongly suggested. (E.g., identifying a series of graviton pulses "from X" strongly suggests either directionality of detection or the sort of extraordinarily sensitive gravimeters described.

Where has "from X" ever been at a strength and distance that required the gravimeters to be that sensitive?

Nor is it suggested in any way that some form of "subspace" sensors detect mass magically. Observation of gravity and its effects is the only method IRL to directly detect the mass of an object external to your control, and is the most extensively used one. (We rarely measure inertial mass directly.)

The Enterprise could measure the mass of a Borg Cube while the Cube was at warp.

We are in some ways. At the same time, mass patterns are important enough to detailed scans that I would count that as one of the more important sensor systems.

Of course, the Enterprise is always looking for anomalies, and gravimeters can deliver. But they'd realistically be a "second pass" sensor, used after the primary sensors have given enough information for the gravimeter data to have any substantial value.

But then, so is tracking interstellar hydrogen displaced by a warp speed vessel. "Impractical" is a problematic term when faced with the evidence.

If there's an impractical and a more practical (or less impractical) explanation that fits the evidence, then I'd prefer to go with the latter option.

As far as "short range" goes, I don't see any evidence of very detailed scans being carried out past a few light seconds at most, and in general the most detailed information may easily be restricted to about 40,000 km (transporter range). You can call this short range (you've been using the idea of detecting an individual ship at a light minute), but it's really not very short range. Tactical range for Trek ships is on the order of a light second against other moving ships, after all.

Our ideas of what makes a useful base measurement case are separated by 3 orders of magnitude here.

40,000 km is pretty short range as far as space is concerned, and as distances get shorter, gravimeters can become more useful. But many other Federation sensors can detect things at much longer ranges. If we're talking about short-range detailed scans, then a number of objects go away. (I should note that the topic earlier was not about short-range scans.)

[Jedi Master Spock]

What are the effects of mass lightening? As far as I'm aware, the gravity well of a mass-reduced object isn't confirmed to have changed. If that's the case, then there's no "shadow." Then we just modify the potential energy of the mass-reduced object by transferring what we need to/from subspace (since the AMRE is linked to subspace anyway).

Actually, mass lightening is quite explicitly explained in "Deja Q." In order to move the moon, they reduce its inertial mass by reducing its local gravitational constant.

Meanwhile, we still have no way of giving an object the required potential energy while it floats away from the gravity well that would otherwise be pulling it in.

You don't give the object the energy. It's the generator that needs to supply (or absorb, or reflect) excess energy.

Perhaps I should talk some about the motivation for invoking quanta of gravitation in the first place and the general properties of particles in systems of particles? That may help, gravity is still a very messy field of study.

Um, because energy can appear out of nowhere.

Energy never appears out of nowhere.

I take it I do need to explain the motivation for gravitational quanta. The idea behind quantizing a field into particles is to break it up into discrete packets with individual bits of momentum and energy; much as a photon represents an individual packet of electromagnetic waves, a graviton represents an individual packet of gravitational attraction. Each graviton - which is difficult to present in three spatial dimensions and one temporal dimension, see here or here for some obvious google hits; the "problem" of gravity started to vex theoretical physicists in the 1920s for this precise reason - has a particular amount of energy associated with it.

We can suggest 1e-40 joules as a good general order of magnitude for the energy tied to some individual graviton, which is why we don't hear very much talk about detecting individual gravitons in a realistic setting.

The obvious point from all that is that if you have gravitons, it's quite possible to explain any energy and momentum redistribution involved in terms of interaction between the blocking envelope and the gravitons in question - as I said, energy that the generator has to deal with in one fashion or another.

So a violation of thermodynamics is somehow preferable to a trick question on a quiz for an explanation?

It wasn't a trick question - the one trick question of that quiz came at the end, you may recall. That was just part of his general review.

Where has "from X" ever been at a strength and distance that required the gravimeters to be that sensitive?

When has it been of a known strength that caused noticable effects?

The graviton pulses from the crystalline entity were how strong? Can you say? No, but we can say pretty clearly that there were taken to be definitely from the CE. Directionality is established from that passage, although not sensitivity.

The Enterprise could measure the mass of a Borg Cube while the Cube was at warp.

Which can be taken as a use of gravity sensors in warp space. We see things at warp, which implies that light at warp speed is travelling faster than light relative to things outside warp.

If there's an impractical and a more practical (or less impractical) explanation that fits the evidence, then I'd prefer to go with the latter option.

There's not a more practical explanation; that's the problem.

40,000 km is pretty short range as far as space is concerned, and as distances get shorter, gravimeters can become more useful. But many other Federation sensors can detect things at much longer ranges. If we're talking about short-range detailed scans, then a number of objects go away. (I should note that the topic earlier was not about short-range scans.)

Astronomically, it's pretty short. In space, however, it's pretty large.

[SailorSaturn13]

Now let's say you have a graviton-blocking plate on the ground, and you're standing next to it. Now throw that bowling ball up into the "shadow." You will have given it x KE. When it hits the ground, it should have, at most, x KE. But now it's going up and not receiving any potential energy (it's not moving against a gravity field and there's nothing between the plate and the ball to transfer energy). When the ball leaves the "shadow," it starts gaining potential energy and losing kinetic energy until it reaches the peak, then gains KE again as it falls, eventually gaining more KE than it started out with.

Again, we've just created a perpetual motion machine. Just keep throwing bowling balls up and have them move a generator when they land. There's nothing in the system that is losing an equivalent amount of energy for the gained KE, so CoE is violated.

Now let's create a perpetuum mobile with mass lightening. Throw the ball up, then mass-lighten Earth. When the ball reaches peak - which is MUCH higher than it would be with Earth non mass-lightened - cancel the mass-lightening. The ball falls back and gains much more KE than it had.

The BLOCK ENGINE has to supply the energy needed - we postulate that to keep a block field we have to supply the energy ball would otherwise loose.

Blocking gravitons causes a violation of Conservation of Energy. That's not something we call "easy." Or even "hard." "Impossible" is the word of choice here.

canon overrides physics. If they say they Can block gravitons, they can. And if it says they can get energy out of nowhere, they can. The answer may lie in subspace - remember the soliton wave which got stronger ON ITS OWN?

Second, particles are detected by the interaction they make with their environment. If gravitons are accepted to exist by the Federation, then detecting gravitation means the same thing as detecting gravitons, because gravity cannot exist without gravitons in Star Trek.

WE accept photons, but "detecting light" and "detecting photons" are 2 distinct things.

We have no such comfort when talking about blocking gravitons. There is no mechanism for the graviton blocker to gain/lose energy as objects potentially lightyears away move towards and away from the gravity well while in the "shadow."

The obvious would be that if you block gravtons you get a pull YOURSELF.

Because blocking gravitons as such would violate the first law of thermodynamics, we can conclude that outright blocking of gravitons is impossible.

Says who? In fact., if you take into account that the body in shadow ALSO sends gravitons, we can easily constitute laws that make the blocker loose exactly the amount of energy we need.

Now, there are ways to make the ST4 quote work. One possibility is that the question is worded strangely on purpose (it does use the word "anti-gravitons" when gravitons may be their own antiparticle), and the real goal is to modify the envelope so that the current gravitational pull is countered.

Context is about PARTICLES, not forces per se.

[Keiran]

What are the effects of mass lightening? As far as I'm aware, the gravity well of a mass-reduced object isn't confirmed to have changed. If that's the case, then there's no "shadow." Then we just modify the potential energy of the mass-reduced object by transferring what we need to/from subspace (since the AMRE is linked to subspace anyway).

Actually, mass lightening is quite explicitly explained in "Deja Q." In order to move the moon, they reduce its inertial mass by reducing its local gravitational constant.

Okay, so the energy still has to come from somewhere, like being transferred to/from subspace via the warp field.

And reducing G locally won't reduce mass (thus making the object easier to push), just the gravity well.

And the gravitational pull outside the warp field could still be the same, the extra gravity well being generated by the warp field.

You don't give the object the energy. It's the generator that needs to supply (or absorb, or reflect) excess energy.

There's still no way to transfer this energy. The whole lack of a gravitational field to transfer energy and all... (Remember: any arbitrary amount of mass could be moving in any direction, but there's no mechanism there for the Graviton Eater 3000 to supply/absorb/reflect the varying possibilities.)

Um, because energy can appear out of nowhere.

Energy never appears out of nowhere.

Exactly. But for the graviton shielding to work, that's exactly what would have to happen.

I take it I do need to explain the motivation for gravitational quanta. The idea behind quantizing a field into particles is to break it up into discrete packets with individual bits of momentum and energy; much as a photon represents an individual packet of electromagnetic waves, a graviton represents an individual packet of gravitational attraction. Each graviton - which is difficult to present in three spatial dimensions and one temporal dimension, see here or here for some obvious google hits; the "problem" of gravity started to vex theoretical physicists in the 1920s for this precise reason - has a particular amount of energy associated with it.

We can suggest 1e-40 joules as a good general order of magnitude for the energy tied to some individual graviton, which is why we don't hear very much talk about detecting individual gravitons in a realistic setting.

The obvious point from all that is that if you have gravitons, it's quite possible to explain any energy and momentum redistribution involved in terms of interaction between the blocking envelope and the gravitons in question - as I said, energy that the generator has to deal with in one fashion or another.

If it's "quite possible" to explain it, then, by all means, do explain where the energy goes. From what I'm seeing, the system can either gain or lose energy depending on the direction objects are moving in the "shadow." How is it possible for the Graviton Eater 3000 to gain 100 MJ in one run (massive object moving closer to the planet through the "shadow") and to lose 100 MJ in another run (same object moving away from the planet)?

You're talking about interactions under the device, but it's the actions of objects above the device that determine the changes in energy. And there's no mechanism for the objects above the device to transfer the energy to the device. (After all, you took away the field that would normally do it.)

So, again, I have to ask: what mechanism is there that can allow the device to gain energy one time, and lose energy another time?

It wasn't a trick question - the one trick question of that quiz came at the end, you may recall. That was just part of his general review.

Why can there only be one trick question? (It could be testing his ability to logically think through imprecise terminology.)

When has it been of a known strength that caused noticable effects?

Just because it's not noticeable to humans doesn't mean it isn't pulling 1e-8 g's on the gravimeter (which is enough for today's gravimeters to detect). Again, I don't see any evidence that require any absurd level of precision.

The graviton pulses from the crystalline entity were how strong? Can you say? No, but we can say pretty clearly that there were taken to be definitely from the CE. Directionality is established from that passage, although not sensitivity.

So? When they detect their gravimeters suddenly going from pointing whatever towards the CE, they know it's from the CE. Again, this doesn't require us to assume the Enterprise was equipped with absurdly sensitive gravimeters.

Which can be taken as a use of gravity sensors in warp space. We see things at warp, which implies that light at warp speed is travelling faster than light relative to things outside warp.

The Enterprise was not at warp.

There's not a more practical explanation; that's the problem.

Sure there is. So far, there hasn't been any evidence presented that would require the use of absurdly sensitive gravimeters.

Astronomically, it's pretty short. In space, however, it's pretty large.

Yeah, but it's not enough to tell you there's a starship hiding behind a moon when you're in orbit around a planet.

[Keiran]

Now let's create a perpetuum mobile with mass lightening. Throw the ball up, then mass-lighten Earth. When the ball reaches peak - which is MUCH higher than it would be with Earth non mass-lightened - cancel the mass-lightening. The ball falls back and gains much more KE than it had.

The BLOCK ENGINE has to supply the energy needed - we postulate that to keep a block field we have to supply the energy ball would otherwise loose.

That's assuming the warp field doesn't emit extra gravitons outside the field to keep everything in sync.

canon overrides physics. If they say they Can block gravitons, they can. And if it says they can get energy out of nowhere, they can. The answer may lie in subspace - remember the soliton wave which got stronger ON ITS OWN?

How would the energy transfer to/from any arbitrary number of objects any arbitrary distance away? Can the device be overloaded by moving too much mass towards it too fast? How does CoE continue to be followed after the destruction of the device when the "shadow" is moving at lightspeed a million years later, still disrupting potential energy of objects?

WE accept photons, but "detecting light" and "detecting photons" are 2 distinct things.

A "photon detector" encompasses more wavelengths than the visual range we call "light."

The obvious would be that if you block gravtons you get a pull YOURSELF.

If you're stationary (resting against the ground, for example), then no work is being done, then no energy is gained or lost.

Says who? In fact., if you take into account that the body in shadow ALSO sends gravitons, we can easily constitute laws that make the blocker loose exactly the amount of energy we need.

What happens when the Graviton Eater 3000 is turned off and moved and some massive objects a light-hour away enter the field and start moving around?

Context is about PARTICLES, not forces per se.

The particles that carry the force; you can't have one without the other.

[Praeothmin]

A "photon detector" encompasses more wavelengths than the visual range we call "light."

Actually, what we call "light" doesn't stop at the visual range...
In optics, no matter the wavelength the source emits at, it is still called a "lightsource", and it is said to emit light.

So, detecting individual photons is very much different then simply detecting "light", IMO.
An optical power meter, for example, will detect all the individual photons that make up the "light beam", but will not be able to differenciate them.
It will only be able to "see" the total output of the "light source".
So in this case, it could not be called "photon detection", but "light detection".