Traveller 2300 Game Query

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Re: Traveller 2300 Game Query

Postby GJD » Wed Jan 01, 2014 1:07 am

enderra wrote: However, my earlier objection was based on the impossibility to suggest that there is any form of ftl detection. That breaks not only everything we know and hold dear, but it also breaks the setting. (If you can detect anything FTL, you can also build an FTL radio.)
It's not a sensor that provides results FTL, it's a sensor that detects an active stutterwarp by it's interaction with the ships sensors, whatever form you want that to be. As I said, the results still only propagate at the speed of light, so if a ship 2 light hours away turns on it's stutterwarp, you get those readings two hours later. Of course, by then they they have probably outpaced their own sensor wavefront and the first thing you know is when they arrive.
enderra wrote:As for detecting a starship, should be easy based on the radiation it's giving off. Lots of infrared, if nothing else. Plus, the intermittent nature of the signal (it skips space as it travels) should set it apart quite nicely from any conventional or natural source (a question of resolution of the sensor I guess). So you can track it quite nicely while it's in your system, but before it arrives and after it departs, you can't tell where it's going or coming from etc.


The grav sensor doesn't detect a starship in any really useful form. It quite clearly cannot be used for targeting or identification, or even ranging and course, just notification that somwehere, sometime there was a ship. As I also said, you'd get a lot more information from a basic optical scope.

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Re: Traveller 2300 Game Query

Postby GJD » Wed Jan 01, 2014 1:10 am

Wil Mireu wrote:
GJD wrote:It's a suggestion I made on the 2300ad facebook page which Colin Dunn (the 2300AD line writer) liked and ran with. If it gets into print it'll be canon, as the moment it's a suggestion.
I was under the impression that Colin had rejected the idea of grav scanners (as described in 2300AD) since they were so unrealistic.

Perrsonally I don't like the idea that stutterwarp is trackable at all, with any kind of technology.
And I'd be with him, but it's in the GDW 2300AD so we were tossing ideas around about what it could be, since any modern method we have of detecting gravitational waves won't work the way it's been described.

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Re: Traveller 2300 Game Query

Postby enderra » Wed Jan 01, 2014 1:37 am

GJD wrote:Nothing is instant. Everything takes time, even if it's only plank-time duration for each jump, you still lose some time when you consider the number of jumps involved.
Well if a jump were to take less than one Planck time, we couldn't detect so anyway.

Planck time 1: Ship is in location A
Planck time 2: Ship is now in location B, a couple hundred meters further down the road.

My point was that the ship is never "elsewhere" - there's no jumpspace or hyperspace or whatever.
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Re: Traveller 2300 Game Query

Postby enderra » Wed Jan 01, 2014 1:53 am

GJD wrote:It's not a sensor that provides results FTL, it's a sensor that detects an active stutterwarp by it's interaction with the ships sensors, whatever form you want that to be. As I said, the results still only propagate at the speed of light, so if a ship 2 light hours away turns on it's stutterwarp, you get those readings two hours later. Of course, by then they they have probably outpaced their own sensor wavefront and the first thing you know is when they arrive.


Yes, fixed in edit, I shouldn't answer to messages when tired. Mea Culpa. The FTL thing was another discussion elsewhere.

But your proposed sensor still doesn't make sense; you basically replace a grav sensor that won't work (at least not in a practical sense) with something that has no explanation, no logic, and no practical use. What's the point?

Why not just chalk it up to 1980s sensibilities and move on? It won't affect the setting much, if at all, if there's no grav sensor.
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Re: Traveller 2300 Game Query

Postby Hopeless » Wed Jan 01, 2014 1:43 pm

So back to say how it was treated in the Lost Fleet series where there was a definite time lag between ship's arriving and anyone on a planet in the system learning of their arrival via a series of space navigation satellites?

Hmm well at least if I went with my game idea it would explain how they managed to reach the planet's surface rather than being intercepted well before reaching the inner system...
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Re: Traveller 2300 Game Query

Postby GJD » Wed Jan 01, 2014 3:03 pm

enderra wrote:
Yes, fixed in edit, I shouldn't answer to messages when tired. Mea Culpa. The FTL thing was another discussion elsewhere.

But your proposed sensor still doesn't make sense; you basically replace a grav sensor that won't work (at least not in a practical sense) with something that has no explanation, no logic, and no practical use. What's the point?

Why not just chalk it up to 1980s sensibilities and move on? It won't affect the setting much, if at all, if there's no grav sensor.
Sure, you can do. Remove them from the game, I agree it makes more sense, but we were discussing (in the original thread on FB, that is) how to make the canon version of a gravity sensor work. My suggestion was that we KNOW that gravity affects stutterwarp, and affects it in a quantifiable and measurable way, so if we need a sensor that is able to detect "gravity" - by which I took to be a sensor that is capable of detecting space-time curvature due to a mass remote from the sensors location - why not tie it into a system that we already know is affected by gravity. A stutterwarp isn't just going to be affected by the nearest source of gravity - everything with mass will generate a space-time curvature and thus affect the drive in some small way. It's really just flavour text for how the magic grav sensor works.

That aside, the biggest problem with the Grav sensors as written is that they give "size", which I took to be the objects mass, rather than physical dimensions, but not distance or direction. Since the mass of the object remains the same, but the experienced gravitational force will vary with distance from the observer it means that an object twice as far away will have a lower gravitational force on an observer than one closer (I don't remember what the rate of drop would be off the top of my head), so if we have object A with gravitational attraction X and object B with gravitational attraction 2X, is B closer or more massive? Without another reference point, you can't tell. What's even weirder is that if you just knew the gravitational attraction and direction, you could work out distance, and thus mass through taking multiple bearings to the target, but the grav sensor in 2300AD doesn't even give position or direction, just a list of masses of all the objects in range.

The solution I suggested - monitoring fluctuations in the Jerome Field - doesn't fix that problem, but it does suggest a way that the gravity of a remote object could be detected - by it's influence on the stutterwarp field. You still have the problem that the grav sensor itself works in a counter-intuitive way, giving a result (the mass of an object) - without the other necessary information, direction and distance. It's like like solving a complex equation without showing the working out.

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Re: Traveller 2300 Game Query

Postby Wil Mireu » Wed Jan 01, 2014 6:35 pm

enderra wrote:
GJD wrote:Nothing is instant. Everything takes time, even if it's only plank-time duration for each jump, you still lose some time when you consider the number of jumps involved.
Well if a jump were to take less than one Planck time, we couldn't detect so anyway.

Planck time 1: Ship is in location A
Planck time 2: Ship is now in location B, a couple hundred meters further down the road.

My point was that the ship is never "elsewhere" - there's no jumpspace or hyperspace or whatever.
That's how I considered it - however there might be more to it than that perhaps: http://www.sciencedaily.com/releases/20 ... 142218.htm

Of course, if we're being realistic, and wormholes are involved in quantum tunneling too, then it could be that the tunneling particles actually only travel at the speed of light through the wormholes - which would make stutterwarp no faster than light too. ;) (Personally I'd go with 'the ship covers the distance instantaneously', which means that the travel time is actually equal to the cumulative time that the ship is cycling between individual microjumps).
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Re: Traveller 2300 Game Query

Postby enderra » Thu Jan 02, 2014 11:36 am

GJD wrote: My suggestion was that we KNOW that gravity affects stutterwarp, and affects it in a quantifiable and measurable way, so if we need a sensor that is able to detect "gravity" - by which I took to be a sensor that is capable of detecting space-time curvature due to a mass remote from the sensors location - why not tie it into a system that we already know is affected by gravity. A stutterwarp isn't just going to be affected by the nearest source of gravity - everything with mass will generate a space-time curvature and thus affect the drive in some small way. It's really just flavour text for how the magic grav sensor works.
Gravity affects drive efficiency, yes; but if I recall correctly it's a threshold at which efficiency simply drops massively and not a gradient of any kind. So all you know is whether or not you're deep enough in a gravity well. As far as information goes that's still pretty useless.

If it were not a dropoff but any sort of gradient, you could use it for triangulation as you point out, below.
GJD wrote: That aside, the biggest problem with the Grav sensors as written is that they give "size", which I took to be the objects mass, rather than physical dimensions, but not distance or direction. Since
the mass of the object remains the same, but the experienced gravitational force will vary with distance from the observer it means that an object twice as far away will have a lower gravitational force on an observer than one closer (I don't remember what the rate of drop would be off the top of my head),
Inverse square, which is always a good assumption to fall back on.
GJD wrote:so if we have object A with gravitational attraction X and object B with gravitational attraction 2X, is B closer or more massive? Without another reference point, you can't tell. What's even weirder is that if you just knew the gravitational attraction and direction, you could work out distance, and thus mass through taking multiple bearings to the target, but the grav sensor in 2300AD doesn't even give position or direction, just a list of masses of all the objects in range.
Why do you think it won't give you that info? The "they meant mass when they wrote size" call is a good one, but beyond that I don't see how those limitations can apply, since, as you rightfully state, the sensor can't actually tell what the mass of an object is without also knowing the distance. From re-reading the paragraph, I think it's quite obvious the author meant "of all the attributes this planetary body has, only mass can be detected by a gravitational scan because everything else, such as atmosphere, presence of water etc, can't be derived by looking at its gravity".
GJD wrote: The solution I suggested - monitoring fluctuations in the Jerome Field - doesn't fix that problem, but it does suggest a way that the gravity of a remote object could be detected - by it's influence on the stutterwarp field. You still have the problem that the grav sensor itself works in a counter-intuitive way, giving a result (the mass of an object) - without the other necessary information, direction and distance. It's like like solving a complex equation without showing the working out.
Well - thanks, for the explanation - I do understand where you're coming from. But I still maintain that the way to fix a "hard" science fiction setting is to actually use science and technology, and not just make stuff up that makes no sense at all. Your magical sensor is still more troublesome than the problem it is trying to fix, without fixing the problem.
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Re: Traveller 2300 Game Query

Postby enderra » Thu Jan 02, 2014 11:52 am

Wil Mireu wrote: That's how I considered it - however there might be more to it than that perhaps: http://www.sciencedaily.com/releases/20 ... 142218.htm
Thanks for the link, that's quite interesting.

And yeah whatever mechanism stutterwarp drives use, it obviously can't be faster than light - that's a given. :)
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Re: Traveller 2300 Game Query

Postby GJD » Thu Jan 02, 2014 12:09 pm

enderra wrote:
GJD wrote:so if we have object A with gravitational attraction X and object B with gravitational attraction 2X, is B closer or more massive? Without another reference point, you can't tell. What's even weirder is that if you just knew the gravitational attraction and direction, you could work out distance, and thus mass through taking multiple bearings to the target, but the grav sensor in 2300AD doesn't even give position or direction, just a list of masses of all the objects in range.
Why do you think it won't give you that info? The "they meant mass when they wrote size" call is a good one, but beyond that I don't see how those limitations can apply, since, as you rightfully state, the sensor can't actually tell what the mass of an object is without also knowing the distance. From re-reading the paragraph, I think it's quite obvious the author meant "of all the attributes this planetary body has, only mass can be detected by a gravitational scan because everything else, such as atmosphere, presence of water etc, can't be derived by looking at its gravity".
Because in the Traveller:2300 Referees manual and 2300AD Directors guide say that the Grav sensor gives information on "size (only)". The MGT2300AD version of grav sensors can "(detect) ...planets and asteroids at system wide ranges".

If the sensors could detect size, distance and direction, why say "sizes only" - it's a very specific caveat that the MGT one does little to dispell.

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Re: Traveller 2300 Game Query

Postby Wil Mireu » Thu Jan 02, 2014 9:28 pm

GJD wrote:Because in the Traveller:2300 Referees manual and 2300AD Directors guide say that the Grav sensor gives information on "size (only)". The MGT2300AD version of grav sensors can "(detect) ...planets and asteroids at system wide ranges".

If the sensors could detect size, distance and direction, why say "sizes only" - it's a very specific caveat that the MGT one does little to dispell.
Gravitational sensors don't work like that at all though. Gravimeters are used in geophysics today and their results are pretty ambiguous - you basically end up with a model of what could be underground, and it could be a massive/dense ore body that's deep underground, or it could be a small ore body that's very close to the surface, or it could be anything in between. You have to use knowledge of the geology and terrain to figure out what the most likely scenario is.

A gravimeter in space wouldn't be any better - you wouldn't be able to differentiate between a large planet far away from a small planet closer to the detector. And you'd be far better off using visual and other EM sensors to actually identify the planets than a 'grav sensor' anyway since they would be pretty obvious in those other sensors.
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Re: Traveller 2300 Game Query

Postby enderra » Thu Jan 02, 2014 11:56 pm

GJD wrote: Because in the Traveller:2300 Referees manual and 2300AD Directors guide say that the Grav sensor gives information on "size (only)". The MGT2300AD version of grav sensors can "(detect) ...planets and asteroids at system wide ranges".
Why write "size" if you mean "mass"? *shrug*

Clearly whoever wrote that paragraph wasn't being very precise. Not that the Mongoose-2300AD author is doing better. What's "system wide", for starters?

Sigh.

Wil Mireu wrote: A gravimeter in space wouldn't be any better - you wouldn't be able to differentiate between a large planet far away from a small planet closer to the detector. And you'd be far better off using visual and other EM sensors to actually identify the planets than a 'grav sensor' anyway since they would be pretty obvious in those other sensors.
Yeah but they'd also only measure the strength of local gravity, right? i.e. the sum of all gravity wells at the location of the device; that's why I didn't mention them. I am assuming gravity waves would work (in theory) because they are ripples - that is, changes in gravity as they propagate, but of course the effect is so small that the practicality of such a sensor is clearly in doubt..
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Re: Traveller 2300 Game Query

Postby Wil Mireu » Fri Jan 03, 2014 12:12 am

enderra wrote:
Wil Mireu wrote: A gravimeter in space wouldn't be any better - you wouldn't be able to differentiate between a large planet far away from a small planet closer to the detector. And you'd be far better off using visual and other EM sensors to actually identify the planets than a 'grav sensor' anyway since they would be pretty obvious in those other sensors.
Yeah but they'd also only measure the strength of local gravity, right? i.e. the sum of all gravity wells at the location of the device; that's why I didn't mention them. I am assuming gravity waves would work (in theory) because they are ripples - that is, changes in gravity as they propagate, but of course the effect is so small that the practicality of such a sensor is clearly in doubt..
Yes, there are other reasons why "grav sensors" are silly and that's one :)
A gravity wave detector would be impractical on a starship since it involve ridiculously sensitive lasers that must unaffected by any external vibrations or forces.
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Re: Traveller 2300 Game Query

Postby GJD » Fri Jan 03, 2014 2:50 am

Wil Mireu wrote: Gravitational sensors don't work like that at all though. Gravimeters are used in geophysics today and their results are pretty ambiguous - you basically end up with a model of what could be underground, and it could be a massive/dense ore body that's deep underground, or it could be a small ore body that's very close to the surface, or it could be anything in between. You have to use knowledge of the geology and terrain to figure out what the most likely scenario is.

A gravimeter in space wouldn't be any better - you wouldn't be able to differentiate between a large planet far away from a small planet closer to the detector. And you'd be far better off using visual and other EM sensors to actually identify the planets than a 'grav sensor' anyway since they would be pretty obvious in those other sensors.
I know. That's what I have previously said in the thread - the Grav Sensors as written won't work, so we tried to find a way to make them work.
Wil Mireu wrote: Yes, there are other reasons why "grav sensors" are silly and that's one :)
A gravity wave detector would be impractical on a starship since it involve ridiculously sensitive lasers that must unaffected by any external vibrations or forces.
Not to mention that it tells you the gravitational effect of said gravity wave only at the point where the sensor is, so you know a gravity wave has passed you by, but it won't tell you the mass of a distant object.

The principle problem is that there is nothing that we know of that can map gravity - the curvature of space-time (or maybe the Higgs Field density) - at a location remote from the sensor. Unlike shooting a laser or radar pulse onto an object to get a return and build up an image, or say an explosion to do seismic reflection imaging, you can't "see" what the gravity is 100 meters away from your sensor by active measures.

Likewise passive detection - looking for some form of radiative effect - won't work as gravity is it's own force, i.e. it's not an electromagnetic or nuclear force, and it's not radiative (on the whole - it's theorised that some funky high-energy stellar effects like colliding neutron stars might emit gravitational radiation). We can map thermal radiation by its output of electromagnetic energy. We can map nuclear decay by mapping the output of energetic particles. A theorised graviton would be a massless elementary particle that would be effectively impossible to detect - a theoretical detector with the mass of Jupiter in orbit around a neutron star would have a detection rate lower than the rate of background neutrino detection, and a neutrino detections is widely regarded as a staggeringly rare event because of their low rate of interactions. Gravitons are suggested to be even more bashful.

Of course, that's not to say that in 300 years we haven't developed an entirely new method of detection that allows us to observe gravitons more easily (if they exist).
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Re: Traveller 2300 Game Query

Postby pachristian » Fri Jan 17, 2014 9:23 pm

enderra wrote:
GJD wrote:A grav scanner will tell you someone else is using a stutterwarp within 150 AU, but not range, direction or any other details, just if it's on or off..
Err, not to derail this, but gravity travels at the speed of light, and if you can detect gravity waves I am assuming you should also be able to tell at least direction. Or am I gravely mistaken?
You are mistaken. Gravitational effects are instant. A shift in gravity 10 light-years away is felt at the same time it happens - everywhere.

However, Gravity is the weakest of the four fundamental forces (the other three are electromagnitism, and strong and weak nuclear forces), and the effect drops off very rapidly over distance. So, in theory, you feel the pull of Jupiter's gravity. But in practice, it is so weak compared to all of the other forces on your body that you not only don't notice it, but only a very specialized instrument could even detect it.
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Re: Traveller 2300 Game Query

Postby GJD » Sun Jan 19, 2014 7:40 am

pachristian wrote:You are mistaken. Gravitational effects are instant. A shift in gravity 10 light-years away is felt at the same time it happens - everywhere.

However, Gravity is the weakest of the four fundamental forces (the other three are electromagnitism, and strong and weak nuclear forces), and the effect drops off very rapidly over distance. So, in theory, you feel the pull of Jupiter's gravity. But in practice, it is so weak compared to all of the other forces on your body that you not only don't notice it, but only a very specialized instrument could even detect it.
That's broadly correct, but slightly misleading. Gravity affects things as both the gravitational field and as gravitational waves or radiation. The gravitational field - the space time curvature - is a static field, and so changes to it effect the whole field at the same time. Newtonian gravity suggests those changes happen at an infinite speed, but more recent work suggests that they happen at speeds something in the order of one sextillion (1x10^21) times faster than the speed of light, or 1,000,000,000,000,000,000,000c, but there is no theoretical upper limit. Gravitational waves, the radiative part of gravitational radiation, do propagate at a discrete speed, though.

Newtonian Gravity says that effects on the static gravitational field SEEM to occur at a speed faster than this, but that is an illusion brought about by the nature of the observers interaction with the static fields. Crudely, the pull of the sun on your body is always towards where the sun is right now, even if the image of the Sun is where it was 8 or so minutes ago, because of the lag in the photons getting from the sun to you eyes, during which time the sun has moved. However, the gravitation pull from the sun is always towards where it is NOW, so the gravitational pull is in front of the optical image. This is because that is the effect of the static field. If the sun were to somehow instantaneously disappear, the static field would also disappear, but at the same time, everywhere. This is because a static field does not behave like a radiating body. It's not shooting out gravitons at a discrete speed, it's the curvature of space-time due to mass. If the mass disappears, the curvature changes, and it changes everywhere at the same time. However, this is not a case of anything "travelling" faster than light, because there is no mobile component of the static field - it's there or not. Now, that disappearance may also cause gravitational waves, localised ripples and disturbances of space time, and those disturbances may propagate at light speed.

Regardless, the canon sources say that the stutterwarp drives are detected via a method that propagates at the speed of light.

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Re: Traveller 2300 Game Query

Postby Wil Mireu » Sun Jan 19, 2014 5:51 pm

pachristian wrote:You are mistaken. Gravitational effects are instant. A shift in gravity 10 light-years away is felt at the same time it happens - everywhere.
Wrong. Absolutely 100% wrong.

Gravity propagates at the speed of light. This has been proven. It is not "instant". I was reading a good article about this just the other day, which I've unfortunately forgotten the link for - but I found this instead which explains it. I'm pretty sure the result has been refined more recently too: http://www.nbcnews.com/id/3077353/#.UtwQXBDTm9I
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Re: Traveller 2300 Game Query

Postby enderra » Mon Jan 20, 2014 6:33 pm

Will, I seem to recall that that particular experiment was called into doubt - but not because gravity propagates faster, but rather because this experiment doesn't prove it. Can't recall the details, not wanting to get too involved again either.

I think the issue GJD and pachristian refer to is the apparent lack of aberration (sp?) when it comes to gravity, but (again IIRC) this is solved by using the 'correct' frame-of-reference in General Relativity. I can't say I understand the math involved anyway, hence the 'quotation marks'.
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Re: Traveller 2300 Game Query

Postby Wil Mireu » Mon Jan 20, 2014 8:42 pm

It has certainly been proven that gravity does not propagate instantaneously. No mainstream scientist believes that it does.

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