Relativity

tlb wrote:I am sorry if there are any authors that would try to use an engine that moves the rest of the universe instead of the ship. For one thing that is just a change in viewpoint rather than an actual mechanism; since the mass of the rest of universe is unbelievably huge compared to that of the ship. For another that is claiming various galaxies unbelievably distant are being moved while still maintaining the same relative position.

If I ever encountered a book claiming these things, I would get rid of it immediately and never read that author again; much as I have done in another context with Stuart Woods' Stone Barrington series.

I am not saying it moves the universe. I'm saying that the reference frame for figuring what the drive does is the intersection of the wedge with the universe, thus the universe. The drive still moves the ship as normal.

Consider a car vs an airplane. An airplane operates in the reference frame of the air, it is not exactly that uncommon for small planes to fly while tied to the ground in big storms and there have been observed incidents in the air where a plane was flying backwards by ground speed.

A car, however, always operates in the reference frame of the ground. The movement of the air might increase drag but that's all.

A normal space drive is somehow pushing the ship, it's operating in the context of the ship--the equivalent of the airplane. I'm saying that the wedge is shoving against the fabric of the universe and thus operating in the reference frame of the universe--the equivalent of the car. It is not immune to the mass increase, though--eventually the acceleration will drop off because you don't have the power to overcome the increased mass of your ship, especially as your output is likewise being reduced by the slowing of time.

tlb wrote:

cthia wrote:I think what Loren is proposing is similar to what happens in the Star Trek world. The nacelle's "warp" space-time, therefore has an "apparent" velocity 1000 times c.

Then I have another reason to be glad that I stopped watching after the first season of the original series.

There are showstopper engineering problems with warp drives but Einstein isn't going to object. The Enterprise never actually exceeds lightspeed, it shrinks the space in front of it so as to move at a velocity that appears to exceed lightspeed.

ThinksMarkedly wrote:I meant that several "drive technologies" in Sci-Fi are about space-time warp, where you don't accelerate the mass of the ship, but you make spacetime move. Starfire's drive fields are like that and were actually what I was mostly thinking of here, not Star Trek's Warp Drive, though they apply to. The fact that a Star Trek Warp Drive can go superluminal and Starfire's Drive Fields can't is a distinction without a difference.

I consider things like Starfire to be pseudo-velocity drives rather than warp drives. They don't feel the same to me--warp drives simply amplify your speed, they don't flip a switch and move you to some high speed until you turn them off again. I don't really know how to describe them but warp doesn't feel at all right.

Loren Pechtel wrote:I consider things like Starfire to be pseudo-velocity drives rather than warp drives. They don't feel the same to me--warp drives simply amplify your speed, they don't flip a switch and move you to some high speed until you turn them off again. I don't really know how to describe them but warp doesn't feel at all right.

We see quite a lot that if the warp drive cuts out, the ship drops out of warp in the middle of nowhere. So to stop, all one needs to do is stop feeding energy to the drive. Except when the plot requires otherwise (they had to reverse power to stop the warp drive after the Kosinski modifications in "Where No One Has Gone Before" [TNG]).

Loren Pechtel wrote:I am not saying it moves the universe. I'm saying that the reference frame for figuring what the drive does is the intersection of the wedge with the universe, thus the universe. The drive still moves the ship as normal.

Consider a car vs an airplane. An airplane operates in the reference frame of the air, it is not exactly that uncommon for small planes to fly while tied to the ground in big storms and there have been observed incidents in the air where a plane was flying backwards by ground speed.

A car, however, always operates in the reference frame of the ground. The movement of the air might increase drag but that's all.

A normal space drive is somehow pushing the ship, it's operating in the context of the ship--the equivalent of the airplane. I'm saying that the wedge is shoving against the fabric of the universe and thus operating in the reference frame of the universe--the equivalent of the car. It is not immune to the mass increase, though--eventually the acceleration will drop off because you don't have the power to overcome the increased mass of your ship, especially as your output is likewise being reduced by the slowing of time.

That's kind of hard to believe, but at the same time it sounds true. Before I speculate, let me just say that RFC must have invented the particle shield limit to avoid having to answer this question in the first place, and that the accelerations matching Newton's Laws instead of Einstein are an oversight, just so he could calculate them.

It's hard to believe because we know that space is as relative as everything else. It does flow down a gravity well, which is why space has a curvature, which is why light can't escape a black hole despite nothing being able to outpace it. It's also why our current physics predict that once you cross the event horizon of a black hole, time and space swap roles, so "towards the singularity" isn't "ahead of you" but "in your future". Yeah, freaky.

Both Einstein and Newton say that any inertial frame of reference is indistinguishable from any other. Einstein simply adds an extra term to Newton's First Law to account for the geometry of space (see this Veritasium video, between 9:55 and 11:10). From that point of view, the fact that the ship is accelerating (somehow!) doesn't negate its need to obey Einstein. From the ship's point of view, the total power of its impellers hasn't changed, so there's no reason why it should accelerate any more or any less than it would if it were at rest relative to the system primary. And because the speed of light hasn't changed (TANSTALÆ - There Ain't No Such Thing As Luminiferous Aether), Einstein still rules.

However, in the Honorverse, there are deviations from Einsteinian physics, not in the least that you can travel faster than light. Take, for example, the fact that translating down from alpha to normal space bleeds off 92% of your velocity and dissipates as energy. Simlarly, you can't translate up to hyper from normal space if your speed is over 0.3c. Velocity measured on what frame of reference?

For those statements to be true, there needs to be a frame of reference that is more important than others. What it's at rest relative to isn't specified, but it must be very close to the star that projects the hyperlimit or the mean galactic speed. Though the closest thing we have to an Universe-wide frame of reference is that of the Cosmic Microwave Background. In any case, all of those are at worst a couple hundred km/s, which any cargo ship will exceed in under 5 minutes of acceleration anyway and doesn't represent more than 0.2% of light speed.

When we last discussed Relativity, in one of the first threads I created after joining, "MDMs should last a little longer than they do," I speculated the same thing you're doing now. That the acceleration of the wedge is constant when measured against this frame of reference, not any other, including that of an observer sitting on the missile. The problem with that is that it leads to inconsistencies, such as the fact that from the missile's point of view, its third stage impeller burns out much more quickly than the first and second.

Conclusion: the math breaks down, here. Don't go past this line ("this far, no farther!" - Picard, Star Trek: First Contact). Just ignore the numbers, apply a fudge factor, and accept that RFC has done such an admirable job up until that line.

Then we can discuss what the rest of the 3 billion people do in the Manticore Binary System.

ThinksMarkedly wrote:Both Einstein and Newton say that any inertial frame of reference is indistinguishable from any other. Einstein simply adds an extra term to Newton's First Law to account for the geometry of space. From that point of view, the fact that the ship is accelerating (somehow!) doesn't negate its need to obey Einstein. From the ship's point of view, the total power of its impellers hasn't changed, so there's no reason why it should accelerate any more or any less than it would if it were at rest relative to the system primary. And because the speed of light hasn't changed (TANSTALÆ - There Ain't No Such Thing As Luminiferous Aether), Einstein still rules.

However, in the Honorverse, there are deviations from Einsteinian physics, not in the least that you can travel faster than light. Take, for example, the fact that translating down from alpha to normal space bleeds off 92% of your velocity and dissipates as energy. Simlarly, you can't translate up to hyper from normal space if your speed is over 0.3c. Velocity measured on what frame of reference?

For those statements to be true, there needs to be a frame of reference that is more important than others. What it's at rest relative to isn't specified, but it must be very close to the star that projects the hyperlimit or the mean galactic speed. Though the closest thing we have to an Universe-wide frame of reference is that of the Cosmic Microwave Background. In any case, all of those are at worst a couple hundred km/s, which any cargo ship will exceed in under 5 minutes of acceleration anyway and doesn't represent more than 0.2% of light speed.

When we last discussed Relativity, in one of the first threads I created after joining, "MDMs should last a little longer than they do," I speculated the same thing you're doing now. That the acceleration of the wedge is constant when measured against this frame of reference, not any other, including that of an observer sitting on the missile. The problem with that is that it leads to inconsistencies, such as the fact that from the missile's point of view, its third stage impeller burns out much more quickly than the first and second.

Conclusion: the math breaks down, here. Don't go past this line ("this far, no farther!" - Picard, Star Trek: First Contact). Just ignore the numbers, apply a fudge factor, and accept that RFC has done such an admirable job up until that line.

Then we can discuss what the rest of the 3 billion people do in the Manticore Binary System.

To begin with, any acceleration removes the requirement that all relative frames of reference are equivalent. Once the acceleration stops, then the relative frames are again equivalent; but knowledge of the history still leaves asymmetry. Although Mach's Principle is controversial in how it is applied, the philosophical basis seems sound: if the perceived velocities of the background stars add to an appreciable resultant velocity, then the observer is most likely moving at that velocity (rather than believing the observer is stationary and it is the stars that move). The observer can then check the frequency ship of the light from those stars and come to the same conclusion.

tlb wrote:To begin with, any acceleration removes the requirement that all relative frames of reference are equivalent. Once the acceleration stops, then the relative frames are again equivalent; but knowledge of the history still leaves asymmetry. Although Mach's Principle is controversial in how it is applied, the philosophical basis seems sound: if the perceived velocities of the background stars add to an appreciable resultant velocity, then the observer is most likely moving at that velocity (rather than believing the observer is stationary and it is the stars that move). The observer can then check the frequency ship of the light from those stars and come to the same conclusion.

Hubble's constant in our epoch is ~70 km/s/Mpc. So stars are receding at 0.2c @ at 850 megaparsecs away. Can I measure my velocity against them?

Stars are also moving in nearly random velocity vectors. On average they have a baseline that allows them to orbit the centre of the Galaxy (though they don't obey the regular a = ω²R relation), but each one's vector is different from all the others. In fact, the stars antipodal from us on the other side of the Galaxy have velocity some 300 km/s in the opposite direction (galactic orbital velocity is ~150 km/s). So which star do you measure against? That's 0.1% of the speed of light (0.001c) so it might have never been noticed in the books because of rounding.

How about runaway stars; if you translate from hyper on one, which star is your velocity measured against? We know of a hypervelocity star that is moving at 1200 km/s (wikipedia doesn't say what frame of reference is used).

I'm saying David oversimplified the physics at this point to the point that it's inconsistent with what we know and with itself, or at least we're lacking a lot of update to the theories to explain.

Stars aren't still, the universe isn't static, and yet that's what it looks like from the books. When Einstein proposed General Relativity, scientists still thought the Universe was static, which is why he introduced the Cosmological Constant in the first place. But Hubble and Lemaître upended all of that with data from Leavitt back in 1929.

tlb wrote:To begin with, any acceleration removes the requirement that all relative frames of reference are equivalent. Once the acceleration stops, then the relative frames are again equivalent; but knowledge of the history still leaves asymmetry. Although Mach's Principle is controversial in how it is applied, the philosophical basis seems sound: if the perceived velocities of the background stars add to an appreciable resultant velocity, then the observer is most likely moving at that velocity (rather than believing the observer is stationary and it is the stars that move). The observer can then check the frequency ship of the light from those stars and come to the same conclusion.

ThinksMarkedly wrote:Hubble's constant in our epoch is ~70 km/s/Mpc. So stars are receding at 0.2c @ at 850 megaparsecs away. Can I measure my velocity against them?

Stars are also moving in nearly random velocity vectors. On average they have a baseline that allows them to orbit the centre of the Galaxy (though they don't obey the regular a = ω²R relation), but each one's vector is different from all the others. In fact, the stars antipodal from us on the other side of the Galaxy have velocity some 300 km/s in the opposite direction (galactic orbital velocity is ~150 km/s). So which star do you measure against? That's 0.1% of the speed of light (0.001c) so it might have never been noticed in the books because of rounding.

How about runaway stars; if you translate from hyper on one, which star is your velocity measured against? We know of a hypervelocity star that is moving at 1200 km/s (wikipedia doesn't say what frame of reference is used).

I'm saying David oversimplified the physics at this point to the point that it's inconsistent with what we know and with itself, or at least we're lacking a lot of update to the theories to explain.

Stars aren't still, the universe isn't static, and yet that's what it looks like from the books. When Einstein proposed General Relativity, scientists still thought the Universe was static, which is why he introduced the Cosmological Constant in the first place. But Hubble and Lemaître upended all of that with data from Leavitt back in 1929.

I did not say "star", I said "stars" (plural); so the irregularities are averaged out. If you are in an inertial frame that is spinning, it will be obvious from the apparent movement that you observe of the surrounding stars. Linear movement is harder to detect, but not impossible; despite the occasional hyper-velocity outlier.

PS.

ThinksMarkedly wrote:However, in the Honorverse, there are deviations from Einsteinian physics, not in the least that you can travel faster than light. Take, for example, the fact that translating down from alpha to normal space bleeds off 92% of your velocity and dissipates as energy. Simlarly, you can't translate up to hyper from normal space if your speed is over 0.3c. Velocity measured on what frame of reference?

Is it possible that the Alpha Wall provides the frame of reference in the Honorverse? Would that help explain the way the spider drive works?

tlb wrote:

ThinksMarkedly wrote:On average they have a baseline that allows them to orbit the centre of the Galaxy (though they don't obey the regular a = ω²R relation), --cut--

I did not say "star", I said "stars" (plural); so the irregularities are averaged out. If you are in an inertial frame that is spinning, it will be obvious from the apparent movement that you observe of the surrounding stars. Linear movement is harder to detect, but not impossible; despite the occasional hyper-velocity outlier.

The problem with galactic orbit is that it does not obey regular circular motion, at least not according to Newton. When we noticed that stars had roughly the same tangential velocity independent of how far they were of the centre of the Galaxy that we realised that there had to be a lot more matter out there than we could see. Then Astronomers and Cosmologers, in their tradition of uninspired names, called that "dark matter" (not to be confused with the missing baryonic matter, which I think we've already found).

Since we don't know what dark matter really is, any speculation past this point is, well, speculation. The nature of dark matter could have something to do with what frame of reference is preferred over all others.

In the Alexis Carew sci-fi book series, author J.A. Sutherland speculates that dark matter was to be found in a layer of space separate of our own, through which ships could indeed travel faster than light. His "dark space" and Honorverse's hyperspace are similar in some ways, having currents that allow a ship to go faster than outside of it. They also have sails, like the Warshawski sails, to "catch" those currents. Like the HV hyperspace, long distance visibility is very compromised (even more so). And Alexis is an officer in Her Majesty's Navy, of the (Star) Kingdom of New London, though she fights Hanoverians who speak German, instead of Havenites who have French-sounding names. But comparisons end quickly: things are even more "Age of Sail" in the Alexis Carew universe because the ships can't really move outside of a current and thus can become becalmed; tacking the wind is also an important manoeuvre, something we've never been told of in an Honorverse grav wave though it might be happening. And for some reason the Kingdom of New London not only uses pounds instead of dollars, they also decided to resurrect the shilling...

Anyway, sorry for the digression.

The point was that stars don't obey Newtonian physics and could have something to do with dark matter too. Moreover, orbital speed is also a local phenomenon because the arms of a spiral galaxy don't get tangled, despite the fact that the stars closer to the centre are moving at the same tangential velocity as the ones further out (they have higher angular speed). So how local would the frame of reference be in HV case? Too local and it's just the local star; too wide and it includes zones of low density between the arms.

If you make it Galaxy-wide or up to a billion billion cubic light-years, it's the frame of reference of the galactic centre, and the 150 km/s tangential velocity stars have is swept under the rug by approximations we didn't need to be told. We could go bigger an include the Andromeda Galaxy and the rest of the Local Group, since we're still gravitationally bound to each other.

Or it's the frame of reference of the CMB. As I said, that's the closest thing we have to a Universal frame of reference everyone could agree with.

ThinksMarkedly wrote:
In the Alexis Carew sci-fi book series, author J.A. Sutherland speculates that dark matter was to be found in a layer of space separate of our own, through which ships could indeed travel faster than light. His "dark space" and Honorverse's hyperspace are similar in some ways, having currents that allow a ship to go faster than outside of it. They also have sails, like the Warshawski sails, to "catch" those currents. Like the HV hyperspace, long distance visibility is very compromised (even more so). And Alexis is an officer in Her Majesty's Navy, of the (Star) Kingdom of New London, though she fights Hanoverians who speak German, instead of Havenites who have French-sounding names. But comparisons end quickly: things are even more "Age of Sail" in the Alexis Carew universe because the ships can't really move outside of a current and thus can become becalmed; tacking the wind is also an important manoeuvre, something we've never been told of in an Honorverse grav wave though it might be happening. And for some reason the Kingdom of New London not only uses pounds instead of dollars, they also decided to resurrect the shilling...

Actually there's one mention of ship's tacking to beat "upwind" in grav waves - but only to say they don't need to anymore.

It's in 'The Universe of Honor Harrington' at the end of the first anthology 'More Than Honor' (which, along with the appendix to SVW and the much later armor essay in IFF, provide the bulk of the collected reference materials on Honorverse propulsion, ships, etc.). It says

More than Honor: The Universe of Honor Harrington wrote:Of course, there wasn't always a grav wave going the direction a starship needed, but with the grav detector to keep a ship clear of naturally occurring grav waves impeller drive could, at last, be used in hyper-space. In addition, it was possible for a Warshawski Sail ship to "reach" across a wave (which might be thought of as sailing with a "quartering breeze") at angles of up to about 60° before the sails began losing drive and up to approximately 85° before all drive was lost. By the same token, a hypership could sail "close-hauled," or into a grav wave, at approach angles of 45°. At angles above 45°, it was necessary to "tack into the wave," which naturally meant that return passages would be slower than outgoing passages through the same region of prevailing grav waves. Thus the old "windjammer" technology of Earth's seas had reemerged in the interstellar age, transmuted into the intricacies of hyper-space and FTL travel. By 1750 pd, however, sail tuners had been upgraded to a point which permitted the "grab factor" of a sail to be manipulated with far more sophistication than Dr. Warshawski's original technology had permitted. Indeed, it became possible to create a negative grab factor which, in effect, permitted a starship to sail directly "into the wind," although with a marginally greater danger of sail failure.

ThinksMarkedly wrote:

Loren Pechtel wrote:I consider things like Starfire to be pseudo-velocity drives rather than warp drives. They don't feel the same to me--warp drives simply amplify your speed, they don't flip a switch and move you to some high speed until you turn them off again. I don't really know how to describe them but warp doesn't feel at all right.

We see quite a lot that if the warp drive cuts out, the ship drops out of warp in the middle of nowhere. So to stop, all one needs to do is stop feeding energy to the drive. Except when the plot requires otherwise (they had to reverse power to stop the warp drive after the Kosinski modifications in "Where No One Has Gone Before" [TNG]).

I don't see them as being the same, although in both cases you're stranded.

With a pseudo-velocity drive you instantly obtain whatever performance it's capable of, when it's switched off you return to whatever your velocity was before you started. The only ones I can recall being FTL are from long ago (ie, Lensman) before Einstein was a household name. Ships with pseudo-velocity drives usually don't have all that high delta-v capability as their drives will basically only be used to match velocities with wherever you are going. Tens or hundreds of km/sec is plenty.

Warp drives don't move you anywhere, they make the distance shorter and you use some other drive to actually move your ship. When they cut out you retain whatever velocity your realspace drive produced. Such ships have very high delta-v capability because the warp drive simply amplifies it. They can usually push the ships to relativistic velocity.

Loren Pechtel wrote:I am not saying it moves the universe. I'm saying that the reference frame for figuring what the drive does is the intersection of the wedge with the universe, thus the universe. The drive still moves the ship as normal.

Consider a car vs an airplane. An airplane operates in the reference frame of the air, it is not exactly that uncommon for small planes to fly while tied to the ground in big storms and there have been observed incidents in the air where a plane was flying backwards by ground speed.

A car, however, always operates in the reference frame of the ground. The movement of the air might increase drag but that's all.

A normal space drive is somehow pushing the ship, it's operating in the context of the ship--the equivalent of the airplane. I'm saying that the wedge is shoving against the fabric of the universe and thus operating in the reference frame of the universe--the equivalent of the car. It is not immune to the mass increase, though--eventually the acceleration will drop off because you don't have the power to overcome the increased mass of your ship, especially as your output is likewise being reduced by the slowing of time.

That's kind of hard to believe, but at the same time it sounds true. Before I speculate, let me just say that RFC must have invented the particle shield limit to avoid having to answer this question in the first place, and that the accelerations matching Newton's Laws instead of Einstein are an oversight, just so he could calculate them.

I think he just goofed. I'm taking the observed characteristics and trying to build an internally consistent model. It still doesn't explain all the acceleration a ship is capable of but it comes a lot closer than figuring drives work in a relativistic reference frame.

Both Einstein and Newton say that any inertial frame of reference is indistinguishable from any other. Einstein simply adds an extra term to Newton's First Law to account for the geometry of space (see this Veritasium video, between 9:55 and 11:10). From that point of view, the fact that the ship is accelerating (somehow!) doesn't negate its need to obey Einstein. From the ship's point of view, the total power of its impellers hasn't changed, so there's no reason why it should accelerate any more or any less than it would if it were at rest relative to the system primary. And because the speed of light hasn't changed (TANSTALÆ - There Ain't No Such Thing As Luminiferous Aether), Einstein still rules.

However, in the Honorverse, there are deviations from Einsteinian physics, not in the least that you can travel faster than light. Take, for example, the fact that translating down from alpha to normal space bleeds off 92% of your velocity and dissipates as energy. Simlarly, you can't translate up to hyper from normal space if your speed is over 0.3c. Velocity measured on what frame of reference?

For those statements to be true, there needs to be a frame of reference that is more important than others. What it's at rest relative to isn't specified, but it must be very close to the star that projects the hyperlimit or the mean galactic speed. Though the closest thing we have to an Universe-wide frame of reference is that of the Cosmic Microwave Background. In any case, all of those are at worst a couple hundred km/s, which any cargo ship will exceed in under 5 minutes of acceleration anyway and doesn't represent more than 0.2% of light speed.

Actually, I see no inherent contradiction. Newton and Einstein say any frame is as good as any other--but neither addresses hyperspace. The speed limit of hyperspace transit is not in our universe, but in the hyperspace. Note, also, that you need some sort of absolute reference frame with hyperspace or you introduce time travel issues. (This is commonly expressed as FTL inherently causing time travel issues but it isn't--so long as you have an absolute reference frame involved you can't get into your own past. Without an absolute reference frame jump drives are still ok but hyper drives are not.)

When we last discussed Relativity, in one of the first threads I created after joining, "MDMs should last a little longer than they do," I speculated the same thing you're doing now. That the acceleration of the wedge is constant when measured against this frame of reference, not any other, including that of an observer sitting on the missile. The problem with that is that it leads to inconsistencies, such as the fact that from the missile's point of view, its third stage impeller burns out much more quickly than the first and second.

Conclusion: the math breaks down, here. Don't go past this line ("this far, no farther!" - Picard, Star Trek: First Contact). Just ignore the numbers, apply a fudge factor, and accept that RFC has done such an admirable job up until that line.

Then we can discuss what the rest of the 3 billion people do in the Manticore Binary System.

My approach pretty much avoids this--yes, the burn time is shorter than specified in the missile's reference frame but nobody cares. The power of the drive has been increasing during the burn to adjust for relativistic mass increase and clock slowing. (Why they didn't simply build it stronger: the limit is in the interaction of the wedge with the universe and Einstein isn't messing with that.)