Thursday, March 11, 2010

Rapid Transit

Intergalactic Tunnel Portal
Regular readers know, and newcomers may guess from the blog title and header image, that I have a weakness for traditional space technology. This is the technology of Clarke and Heinlein, and it has the virtue that it actually works. Even the much maligned Shuttle truly has been a workhorse for a generation, its two catastrophic losses more the result of mismanagement than its design flaws. (And at that they were just the disasters that writers of the rocketpunk era expected.)

Thus I have avoided discussion of FTL, or even such minor technomagics as antigravity and sublight warp drives. In part it is because these technologies are so speculative that it is hard to pin down their capabilities and limitations, in part because I just plain prefer roaring rockets (or, in a different context, flashing swords) to magical mumbo jumbo.

But physics rears its head in surprising ways, and it showed up in the wonderful, astonishing comment threat on Torchships to point out that FTL, with certain constraints, does not violate General Relativity. (GR itself is surely not the Final Word on the subject, but its findings are no more likely to be tossed out wholesale than Newton was.)

In particular, commenter Luke raised the subject of wormholes, and explored some of the relevant concepts. I recommend the discussion, though you may wish to inbibe the ethanol mix or herb of your choice before your head explodes.

The mainstream convention in science fiction is to treat FTL as a handy interstellar rapid transit system, allowing ships to travel at the speed of plot while otherwise leaving them as more or less familiar, recognizable spaceships. My own preference, back when I was playing with traditional FTL in demi operatic settings, was to treat starships as hardly different from interplanetary ships except that they had a gizmo somewhere containing a young lady singing in Welsh to hustle things along.

But there is no particular reason to think that wormholes, or other plausible ways of making an end run around Einstein, would work that way. If wormholes can be traversed at all, we may be able to anchor them to planets, so you could simply walk through, or at least drive through like the Holland Tunnel. Stargates of this sort are by no means rare in SF, to be sure; the first I encountered was in Heinlein's Tunnel in the Sky.

Such details are (within broad constraints) purely a matter of conjecture, and I prefer to suppose that the technology of passing through a wormhole requires a 'fixed guideway' of some sort, AKA a railway structure, making it truly a rapid transit system to the stars. While the underlying principles may involve head-exploding physics, much of the operation might be more recognizable - stations, switching systems and interlockings, scheduling trains, and of course a nifty system map inspired by the London Underground map.

So get out your fare card and head for the turnstiles.

Photo Note: San Francisco loves its transportation history, and here a historic (ex-Philadelphia) PCC streetcar arrives inbound, the N Judah line evidently having been rerouted from Sunset/Parkside to Messier 88, 50 million light years from Embarcadero Station. Streetcar image by David Pirmann from; galaxy from Astronomy Picture of the Day.


Thucydides said...

FTL moving at the speed of plot; I like that.

Jerry Pournelle had the best combination of FTL and space opera with the "Alderson Drive"; you needed a spaceship to get to the Alderson point (hence the need for spaceships, a Space Navy, Imperial Marines etc.) but could take the FTL tramline to get to wherever the plot demanded.

But since wormholes or other FTL tropes are not manifested in normal space (at least in any way we can detect today), we can wave enough hands and make anything happen (at the speed of plot).

Francesco said...

I see some small problems about having wormholes on planetary surfaces dealing with things like conservation of momentum and gravitational potential energy. If both of wormholes ends are on rapidly moving and spinning bodies, with different angles, and immersed at different altitudes in gravity wells, does this translate in some kind of stress on the wormhole, on the body crossing it, or both? Luke pointed out that you should send matter both ways to keep things balanced and avoiding stressing the wormhole till it does break, do we've an idea at least rough of the magnitud of the stress that are tolerable and of those that're not?
I mean, if wormholes turn out to be too delicate to allow a proper stargate, if they allow even only some photons, we could still have the ansible.
Other possible consequences, if wormholes are possible and they can be made on local scale and maybe miniaturized, is to having an electronics revolution on hand. FTL communication, even on short ranges, if cheap enough open the door to supercomputers much more efficient than anything we could do right now...

Sabersonic said...

Might as well put my two cents on the whole "Wormhole as Subway IN SPACE" idea.

Assuming that a wormhole bridge could not only be created within the foreseeable future, stable enough to allow transit in between the two "stargates" for lack of a better term reliably, and the phenomenon could be sustained for a reasonable amount of time if "indeterminately" is not possible for Macro-mass transit (i.e. anything larger then an atom at best), there's still the problem of putting that wormhole at the desired exoplanet in the first place.

Or to be more exact: A starcraft will still have to be sent to said star system and exoplanet in order to build the framework that would support the "Exit B" of the wormhole conduit/corridor/tunnel/whatever between Earth and this exoplanet. True, a planet-bound wormhole would all but eliminate the need to build and maintain a fleet of spacecrafts and starcrafts, but it still requires an infrastructure to exist in the first place. I could also imagine a kind of size or volume restriction (not really sure about the mass restriction, don't know enough about relativity and mathematics to wonder about that possibility) that would set a maximum scale of the payload that could perform the transit through the wormhole not unlike the Panamax designs of the twentieth century. If it could only allow transit of two average sized human beings marching abreast, then you can pretty much say goodbye to the idea of driving your car to this new world, much less any heavy construction equipment and vehicles.

I also feel that the technology to "project" wormholes in "free space", for lack of a better term, to other worlds without the need to create a stargate or any like minded infrastructure would be a future development well beyond the foreseeable future.

As for thoughts on the idea of FTL transit itself and not adding FTL communications? I think I'll hold my tongue on that one for the moment. Too many ideas in my head would cause me to babble and ramble carelessly and many of them are Space Opera worthy. Granted, a few are more "mature" and "evolved" thanks due to Atomic Rocket's Webpage on Faster Than Light.

- Sabersonic
Gmail Address

WillN said...

You've read, I hope, Peter Hamilton's Pandora's Star and Judas Unchained series? The train approach is exactly what he uses for traversing his wormholes.

Rick said...

Welcome to new commenters!

'Speed of plot' special credit to R. Mildred, who only left one comment on this blog, but included that brilliant line.

There could be problems with anchoring wormholes to planetary surfaces, but from Luke's discussion these might be solvable - given a tech that can deal with wormholes in the first place.

I would never have thought of the implications of nano-distance FTL for computers!

If wormhole stations have to be put in place by STL ships, this does constrain your future history - the railroad as a whole can only expand at sublight speeds, even if trains on it go faster.

It need not be that severe a complaint - even in FTL interstellar settings, the historic frontier often has implicitly expanded at roughly the speed of light - typically you have settings a few hundred years in the future, and a human region of space a few hundred light years across. Galactic-scale settings are usually thousands of years into the future, a la Foundation Trilogy.

But in any case there are workarounds. Wormholes may exist naturally in vast numbers, needing only to be 'inflated' (or whatever) to fit a rail line through them. Or the Old Ones may have built the tunnels eons ago, so that we only need to add tracks, trains, and station platforms. (Platform 9 3/4, anyone?)

Assuming any of this stuff turns out, ansibles should at least as doable as tunnels that you can push large objects through. But ansibles, like robotic probes, violate the First Law of SF Tourism. We don't just want to talk, or even look at cool pictures - we want to GO there.

Rick said...

Forgot to add that a couple of commenters have now mentioned Peter Hamilton's train-based FTL. More for my to-read list!

ZeGermanz said...

I'd just like to throw out there that while wormholes may technically be feasible, they still have the same nasty issue That all FTL has, and the vast majority of people don't appear to understand.

Wormholes would permit time travel. Time travel would imply violation of causality. Violation of causality is... difficult to work with, to say the least.

Every solution I've come across to this problem that allows wormholes and protects causality requires some kind of arbitrary constraint. "The probability of an event violating causality is zero." "Wormhole mouths must be spatially separated in a spacelike separation." "You can have one wormhole between two points, you can't have more." "Wormholes can be formed, but cannot be traversed." etc. All of these are pretty messy solutions.

It doesn't help that the other proposed method of achieving FTL travel within the bounds of GR, the Alcubierre Drive, has recently been shot down. Apparently when that the vessel breaks light speed, it actually becomes causally disconnected from reality.

The simple fact is that the lightspeed barrier is a singularity. Beyond it, things are simply... undefined. We can speculate, we can guess, we may as well pray (in Welsh), but unless some sort of miracle happens, we won't be able to look past, let alone walk beyond, that veil any time in the foreseeable future.

Maybe we actually don't want to. "Liberate tu ta me ex infernis."


Luke said...

Francesco: As far as we know, the wormholes do not care what the other end is doing across flatspace (so long as they don't make a time machine that lets you go into your own past). The conservation of energy and momentum (and electric charge, and angular momentum) is all handled locally, because the wormhole mouth acquires the conserved properties of anything that goes into it, and loses the conserved quantities of anything that goes out of it.

Here's an example. We have a 1,000,000 ton wormhole mouth on Earth. It's corresponding mouth on Terra Nova also has a mass of 1,000,000 tons. So far, no problem. We send a 100 ton train through at a speed of 10 meters per second. The train has a momentum of 100,000 kg * 10 m/s = 1,000,000 kg m/s. Once the train has passed through, the Earth end of the wormhole will have a mass of 1,000,100 tons and the Terra Nova end a mass of 999,900 tons. The train will have given a kick of 1,000,000 kg m/s to the Earth end in its direction of motion as it passes through, and the Terra Nova end will be kicked back with an impulse of 1,000,000 kg m/s in the opposite direction of the train.

Of course, we want to brace the wormhole ends so our wormholes do not drift around. To analyze the forces, we need to know that the momentum transfer is the force exerted times the time over which the force is exerted. If the train is 100 meters long, it will pass through in 10 seconds. This means the force the train exerts on the wormholes is 100,000 newtons, either in or against its direction of motion. So, to handle trains of this mass and speed, we need braces that can stand up to 100,000 newtons of force.

This leads to an interesting consequence. Wormholes are rockets. If you have one end of a wormhole in space, you can accelerate it by squirting propellant in from the Earth side. As the propellant shoots out the space end of the wormhole, it exerts a force and boosts the wormhole along to where we want it to go. Just like a rocket, we can only squirt so much propellant out before we run out of mass. For very light wormhole ends, we can even use photon rockets efficiently - a 10 nanogram wormhole with a 100 watt laser shining through it will be accelerated at 33 m/s^2, or a bit over 3 gravities. This can end up being a way to get our wormholes to other planets.

Actually, my preferred method is to start out the trip by charging up both ends of a wormhole by shooting a particle beam through one end. Then you shoot one of the wormhole mouths at ultra-relativistic speeds out of a particle accelerator toward your destination. Once launched, you discharge the wormhole by shooting the particle beam through the end left on Earth (so the wormhole is not deflected by stray magnetic fields). At this point, you use the rocket effect for course corrections. Eventually, you need to start slowing down. If your wormhole is sturdy enough, you can just steer it into the planet for lithobraking. Otherwise, you can slow it down with the rocket effect, or by opening it up wide and trying to sweep up as much ISM and solar wind as you can.

Luke said...

Sabersonic: The wormhole itself could be the starcraft. See my note to Francesco. This leads to an odd sort of spacecraft - all your crew and sensors and rockets and propellant are on Earth, but go through the wormhole in order to be used.

Luke said...

Rick: Remember that even though the wormhole ends are traveling to other planets at sub-light speeds, due to time dilation effects those of us back on Earth do not need to wait that long. From the torchship thread, a 100 light year journey might only involve waiting 1 month after launching the wormhole, if the time dilation factor is 1200. It's like being on a relativistic starship, except that you get to stay home.

On another subject, you will probably need airlocks across your wormhole tunnel. Even minor differences in air pressure could lead to hurricane or even tornado force winds howling through the tunnel.

Luke said...

ZeGermanz: We've discussed the causality issue on the torchship thread. I generally go with the idea that wormholes, or wormhole networks, are prevented from turning into time machines by forming perfect resonators for quantum fluctuations as soon as you get closed light-like loops. This either destroys an offending wormhole in the network or exerts a force on them to move the ends around such that you do not get the formation of a time machine. Visser's work on this seems pretty convincing, although not yet proved for all possible wormhole configurations. If this holds, you will need to be careful that your wormholes do not form time machines, but it is doable.

As for the Alcubierre warp drive, it is not entirely clear that it doesn't work - even though a vessel inside a warp bubble cannot affect the outside universe, there is the possibility of arranging the warp bubble so that it "pops" after traveling a certain distance, precipitating the spacecraft out at its destination. This gives you FTL, but you need to chart your course beforehand. Unfortunately, the warp drive is more problematic to analyze than wormholes, because the surface of the warp bubble becomes singular when you get it going light speed - meaning we can no longer use classical general relativity to figure out what is going on.

There are also Krasnikov tubes, but not much work has been done on them.

Thucydides said...

Given the highly stressed metrics of any semi plausible wormhole I have read about, I suspect they are only possible at or near very undesirable real estate, such as the event horizon of black holes or maybe inside a neutron star.

This is probably a good thing, since there are all kinds of implications that wormholes (especially ones that can act as terminals on a planetary surface) would bring.

The easiest one to contemplate is quarantine: would you want the inhabited galaxy to go down with H1N1 (or the computer equivalent)?

If wormholes are energy intensive (as you would expect) then the important star systems would be linked via wormhole and branch lines from the terminal ends would still be via STL rockets. Since the transmission speed in the "suburbs" is far slower than the metro express lines, you would expect lots of cultural dislocation the farther you go from the terminals. This might have to be countered by imposing a static culture such as Egypt in the time of the Pharaohs, otherwise the forces of cultural evolution would make the far ends of the line become alien to the metropolitan center.

There are lots of reasons I could see keeping the end of the wormhole nicely isolated in space, regardless of the ability to host it on a planet.

Luke said...

Thucydides: There are certainly many wormholes described in the scientific literature which have very extreme metrics. The original Morris-Thorne wormhole, for example, was so deep in its own gravitational well that the microwave cosmic microwave background radiation was blue shifted to blow-torch intensity x-rays near the wormhole mouth! However, all of them I have seen are assumed to be built in flat space-time, without nearby neutron stars or black holes. Many of them have neutron star masses or more, however - a wormhole that required a galaxy's worth of mass would not be particularly useful!

Certainly, there are some proposed wormhole geometries that are rather friendly - the Visser wormholes have no space-time curvature anywhere except at singular "struts" or "cords" used to prop them open. The more general "thin-shell" wormholes (of which the Visser wormhole is a special case) relax the singular requirement of the supports while still allowing paths through the wormhole without any space-time curvature. Kuhfittig (Physical Review D vol. 68 article 067502, 2003) discusses a spherical wormhole metric that can be supported by arbitrarily small amounts of exotic matter and can be made arbitrarily low mass. True Visser and thin-shell wormholes are probably unphysical because they have strictly zero mass - they may, however, be approximations of physically possible wormholes with low mass.

Rick said...

My demi meta speculation is that wormholes as such, or any mechanisms we can discuss, are just vague early gropings of a future physics, the later 19th century.

For example, in a story I'd avoid the terms, and stick with something neutral like 'stargate.' What really matters, as I just noted over on the torchships thread, is keeping the calendar straight in your head.

Your characters won't have that problem. Someone will prepare the calendars, and people will grow up knowing the travel consequences without having to understand why it works that way.

Just from literary perspective, the 'perfect resonator' thing works perfectly as a compact explanation, without sounding like an arbitrary handwave. It feels right. Actual validity is a further bennie.

Rick said...

Forgot to add, absolutely nothing precludes putting the rabbit holes off in deep space somewhere, so that you need traditional spaceships to reach them.

For that matter, does there necessarily have to be a physical stargate structure to hold the tunnel open? Or can it just be a locus in space that a properly equipped ship can traverse.

In that case you get the classic ship based FTL look & feel. The GR element is really all in the subway map, and when it gets you where. The physical attributes are pretty much user defined at this point of our knowledge. (???)

Luke said...

Rick: Exactly. No one is going to go through flat space-time when there is a wormhole around, so people will synchronize their clocks through the wormhole instead of across the light years. All the jumping around of time coordinates based on flat space-time can be swept under the rug.

No one really knows if you need a physical structure at a wormhole. Since highly curved spacetime with boundaries can produce regions of negative energy density (the event horizon of a black hole does this), it might be possible for the spacetime warping of a wormhole to generate a negative energy region such that the wormhole can sustain itself. You will be able to see through the wormhole to the other side (although the image is likely to be distorted), and anything that gets there and goes through the tunnel ends up on the other side, so it is not only properly equipped spacecraft that can traverse it. Unless, of course, the wormhole is normally only microscopic in dimensions, and the spacecraft needs to carry along the equipment to open the wormhole wide enough to go through.

Neon Sequitur said...

Another possible use for wormholes involves a different type, a 'non-orientable' wormhole, which reverses the chirality of anything passing through it. If this were possible, it could be used to produce dirt-cheap anti-matter.

Now your wormhole-driven spacecraft can be built with two wormholes: one non-orientable, and one of the old-fashioned kind, both connected to the combustion chamber of your total conversion drive.

And that's probably just the beginning....

Jim Baerg said...


Avoiding having your planet's atmosphere leaking away through the wormhole & quarantine of both biological & computer viruses are good reasons to not put a wormhole on the surface of a habitable planet.

The forces exerted on a wormhole when an object moves through it would tend to change its orbit around the local sun so putting the wormhole in an L4 or L5 point to stabilize its location would seem to be a good idea.

Sabersonic said...

"Wormholes may exist naturally in vast numbers, needing only to be 'inflated' (or whatever) to fit a rail line through them." - Rick

"Unless, of course, the wormhole is normally only microscopic in dimensions, and the spacecraft needs to carry along the equipment to open the wormhole wide enough to go through". - Luke

Oh great, now my mind is running with weird ideas of "Wormhole Stabilization Fields" on board STL spacecraft to traverse the wormhole being generated/stabilized by an orbiting stargate at L4 and L5 Lagrange points. And it's even suggesting the use of the wormhole collapsing back down to its normal radius as a form of propulsion for the spacecraft to exit the wormhole at high velocities not unlike the squeezing of a toothpaste tube or even akin to warp drives. Unfortunately, my mind works like that.

Though the though of wormholes as spacecraft in and of themselves with how Luke described the process. I don't really know, it seems more like the your every day probe mission by NASA. The only difference is that someone could actually GO to the malfunctioning wormhole gate and work on the problem or even bring back samples without figuring the deltaV requirements to do so. That and potentially less swearing like sailors in case of loosing said wormhole due to unforeseen circumstances. Well, unless the total collapse of the wormhole produces energy on the scale of a thermal nuclear warhead, or ten....

As for this one: "Wormholes would permit time travel. Time travel would imply violation of causality. Violation of causality is... difficult to work with, to say the least." Well, I'm not completely sure exactly WHO wrote the article or where I read it from, but there were some research and/or theories which suggests that physics has a way of preventing the kind of Time Travel that would cause such paradoxes to occur. Granted, it did not include the "many worlds" theory of alternate time lines as seen in some movies such as Back to the Future and the recent Star Trek film.

- Sabersonic
Gmail Address

Anonymous said...

Have you read the old Doctor Who novel "Transit"? It describes a network of railways running through "stunnels". There's a lovely quote about "For most people, the map of the System is the map of the universe".
Grif Ingram

VonMalcolm said...

I second (third) the excellence of ‘The Speed of Plot’ line.

If wormholes are feasible doesn’t that add more power to the Fermi Paradox? Shouldn’t there be (detectable?) wormholes scattered through out the local group? -Which would lead to an argument against wormholes in the first place. (How detectable would wormholes be?) Alien interstellar civilizations maybe present but sheer distance may keep them apart from us even if they had .3-.6 c capability, but if wormhole technology is feasible than is there any excuse for an Interstellar Alien Civilization not to be at our doorstep other than that we are ultimately alone in the Universe? (I hope this doesn’t lead to a Reptoids thread.)

This stuff is way over my head so forgive my newbie questions. . .

How does one control width, length and direction of said wormhole? -and would the negative energy density open a mouth of a wormhole which is then ‘projected’ towards the desired destination or would the negative energy density open a throat of a wormhole in between the two desired destinations at which two mouths ultimately open? Or perhaps would two mouths at the two desired destinations be opened and connected via a throat somewhere in the middle? (That would really mess things up.) How much more negative energy density would be needed for a Terra Andromeda Wormhole as opposed to a Terra Nova Wormhole?

Luke, this can of wormholes you opened is pouring out of my eyes, ears, nose and mouth!

Francesco said...

Everything that can be said about the speed of plot haveen said here (Warning: tvtropes timesink ahead!).
I love a lot "a can of wormholes"... I think it could be made a really nice title for an humorous short-story, maybe on the discovery of wormholes technology... :p

Luke said...

VonMalcolm: At this point, we have no idea how to control the length, width, or direction of a wormhole. The shape of a wormhole is, in principle, determined by the distribution of matter, energy, momentum, and stress (forces). In principle, if we can control the negative energy stuff being used to prop open the wormhole, we could control its shape. But there is still a lot we do not know about space-time engineering.

Physics is local, so if we were to create a wormhole, I'm pretty certain we would create both mouths at the same place with the wormhole between them. Then we would have to move the mouths to where we want the ends ofthe wormhole to be. For example - we turn on a huge mondo particle accelerator and crash particles into each other and watch until the detectors pick up the tracks from a pair of wormhole mouths going through them. Then you send a work crew down to disassemble the particle trackers to where the mouths stopped, perhaps digging them out of the bedrock if they are highly penetrating and/or energetic. Then, if you want one end of your wormhole in Syndey and one end in San Francisco, you package each end up and send one of them to Sydney via UPS and one to San Francisco via UPS. Now you have a microscopic wormhole connecting Australia to California, probably less than a proton's diameter in width and less than a proton's diameter in length if you could go through it. Now you somehow wave your magic wand, and get your female Welsh enchantresses, in order to inflate the wormhole up to useable dimensions to tourists and buisnesspeople could go through.

As for the negative energy needed for a Terra Andromeda wormhole versus Terra Nova - it should make no difference. The wormhole doesn't care how far apart its mouths are in flat space.

As for the Fermi paradox - the aliens still are not here. Wormholes or not, either they don't exist, or they don't want to visit. (By "do not exist" I mean we are outside of the light cone of the event of the aliens creating their first wormhole.) As I mentioned in the torchship thread, if intelligent life is rare in the universe but we are not unique, the dynamics of how wormholes move naturally leads to us encountering other civilizations of our own level of advancement as soon as we figure out how to create wormholes.

At this point, we simply do not know how detectable wormholes are. At least one attempt was made to see if negative mass wormholes exist by looking for their unique gravitational lensing signature - none were found. Positive mass wormholes would probably be indistinguishable from other objects of the same mass that we cannot directly image. The universe could be crawling with them for all we know.

Luke said...

Sabersonic: A wormhole collapse cannon - I like it!

As for wormholes as spacecraft - if you can get low mass wormholes, these make sense. Why spend a zillion dollars per kilo for a one ton spacecraft when you can send a nanogram wormhole for pocket change. Then, when it gets to mars, it can eat some of the local soil to gain enough mass that you can send people through. Suddenly, every university will have a hands-on planetary exploration program. Also, using wormholes as spacecraft can be very important in getting them to where you want them to go - if you send one to Terra Nova, it is a spacecraft as it is going there.

Not to mention that if we want space battles, wormholes do not need huge heat sinks. They can dump all their heat on the planet where the other end is. In fact, all their weapons and generators can be on the planet, they will just be shooting beams out through the wormhole at each other. If wormholes are hard to damage, you may even see the return of boarding actions, where one wormhole overtakes the other, engulfs it, and sends a squad of marines through to wreck the equipment on the other side.

Citizen Joe said...

What if natural wormholes are formed in black holes where space is highly curved. However, since it is so curved, the tail ends tend to get disrupted unless they wind up in flat space. The now 'stable' wormhole dumps mass out of the black hole into flat space. Without the counterbalance, the wormhole causes a spatial distortion which essentially means creating new space. The apparent result is that it makes galaxies and stars seem like they are moving farther apart. Since there is more and more flat space being created, the chance of the tail end of a wormhole ending there and thus being stable enough to send matter through is growing. Thus more stable wormholes and more space being created. This is what is causing the universe to expand and accelerate.

Anonymous said...

A particle physicist named Jason Hinson worked out a plausible explanation for subspace and warp. He made it plausible mainly by ignoring some of the dumber technobabble, which just goes to show how valuable the editing process really is.

If your wormholes involve stresses that would destroy any macroscopic object that passes through them, you can still use them as rockets. Hold one end at the back of a payload module, and fire a rocket into the other end. This gives you a high-thrust craft that's almost nothing but payload, and lets you travel between stars on a humanly useful timescale. Of course, you're entirely dependent on the people back home to keep the rocket going...

Actually, thinking about it there's no reason you can't have more than one type of wormhole in your story, just like we can build more than one type of electromagnetic radiation-based communication network. Big, stable highly-engineered spacetime volumes connecting the major star systems, smaller and less-engineered wormholes as rockets to the star systems of the backbeyond, and nanoscale wormholes for fast communications between rich institutions. Galactic civilization is connected by a network of stargates, and the governments and major institutions can all talk to one another through quantagraph, but there are worlds that only see interstellar traffic maybe once a decade. Like mid-19th Century Europe, you can communicate with or get to any civilized region quickly and in comfort, but if you want to go somewhere off the rails you might as well be travelling back in time to the 18th or even 17th Century.


Anonymous said...
This comment has been removed by a blog administrator.
Winchell said...

Francesco, yes, I also had thought about the application of FTL to computer speed. Ever since I read about Admiral Grace Hopper handing out lengths of copper wire as "nanoseconds" (being the distance an electron travels in one nanosecond).

Thucydides said...

I found an email where I discussed the issue of how assumptions in world building would change the parameters of the story. Here is the relevant portion:

Other space drive or transportation systems have different effects on Society/politics, depending on the parameters you choose:

a. Relativistic STL drive means no practical Empire at all. The central office will dispatch expeditions that will arrive hundreds or thousands of years later in their frame of reference, and reports and returns will take similar amounts of time. Imagine if the Afghanistan task force was just receiving reports from Alexander the Great about conditions in Afghanistan, and would arrive there in 3000 AD to conduct the mission, and you will see what I am getting at.

b. Wormholes with fixed ends. Everything will revolve around the wormhole and its location. The terminus will be the most valuable and heavily defended piece of real estate on a planet or solar system (Stargate SG-1), or if it is some sort of natural phenomena, then entire armadas will be needed to secure the ends for your side (The Forever War, by Joe Haldeman).

c. Wormholes with unpredictable ends. If the area in which wormholes can exist is known with some certainty, then this becomes analogous to choke points in naval warfare, like the Straights of Gibraltar. Jerry Pournell'e "Alderson Drive" used this. Space navies and space opera conventions can apply here.

d. Unpredictable phenomena would create a sort of priesthood or shamanistic class of people who would claim to be able to call up the warp/wormhole etc. This is not something I have seen done before, might be a fun thing to look into?

Eric said...

Luke, after reading your proposal on how we could use relativistic wormholes to rapidly (from our perspective) explore other solar systems I tried setting up some light cone diagrams to see whether it would be possible to have a "triangle" of three locations connected via wormhole by your method.
I ran into problems with the first connection. shows the progress I made when I got stuck. I put a connection between the position lines of earth and A. C. that was within earth's light-cone, a la relativistic probe. The slope of the red lines denotes the wormhole connection, thus points 1 and 1' are spacetime points connected through the wormhole (you could stand on earth at 1 and look through the wormhole and see 1'. The same goes for 2 and 2', and 3 and 3'.
Where I ran into problems is where you can see the thin yellow line coming off of point 3. A light message sent from 3 would arrive at A. C. sometime between 2' and 3'. Thus, someone at A. C. could see that message, walk through the wormhole, and arrive on earth before point 3 to stop the message from being sent. Instant paradox.

I hope that my logic is flawed here. Is this kind of diagram even appropriate for something like a wormhole connection? Or am I missing something painfully obvious in my setup?

Citizen Joe said...

The game Fading Suns (by Redbrick publishing) has the ritualistic priesthood that deals with gates between systems. The gates themselves are way out there. The timing of the gates and navigation through them is controlled by a small group of people.

Luke said...

Eric: As you noted, wormholes where the ends have a time-like separation can act as time machines. You want to keep the separation space-like (that is, one end of the wormhole connects to outside of its own light cone).

If you want to diagram it out as a space-time diagram, the important events are (1) the event where one end is launched - at this point, both ends are at Earth; (2) the event where the projected end arrives at A.C.; (3) the event where earth observes the projected end arriving at A.C through the wormhole. The red line illustrating events connected by the wormhole goes from event (2) to event (3).

I presume A.C. refers to Alpha Centauri, which is 4.37 light years from earth. For illustrative purposes, say that the projected end of the wormhole is launched at 0.95 light speed. This gives it a time dilation factor of sqrt(1/(1-0.95^2)) = 3.2. Event (1) is on Earth's world line at time 0. Event (2) is on A.C.'s world line at time 4.37/0.95 = 4.6 years. Because of time dilation, the proper time that passes for the projected wormhole end is 4.6/3.2 = 1.4 years. So event (3) is on the Earth world line at time 1.4 years. The slope between (2) and (3) is (4.6 - 1.4)/4.37 = 0.73. This puts the event (2) outside of the light cone of event (3). When you have a single wormhole with spacelike separation, you should find that it cannot send a signal back to before the signal was sent.

Luke said...

Citizen Joe: The problem with having wormholes inside black holes is that they are inside of an event horizon. You can go in, but you can't get back out again. If one end is inside a black hole and the other isn't the wormhole is one way - you can dive through the event horizon and go through the wormhole, but you can't go back since you would have to come out through the event horizon. If both ends are in black holes, you can't use the wormhole to go anywhere in this universe.

This leads me to a slight digression. It concerns a property called topology. If you can distort one shape into another shape without ever tearing and/or sewing up the surface, the two surfaces have the same topology. For example, a teddy bear has the same topology as a sphere (neither has any loops), and a bagel has the same topology as a coffee mug (both have one loop). However, a bagel has a different topology than a sphere.

It may or may not be obvious, but the universe with a wormhole connecting two of its points has a different topology than one without. Herein lies what I am getting at - we do not know if it is possible to change the topology of space-time. It might be fundamentally impossible to "poke a hole" in space-time in order to make a wormhole. If this were true, it would seem to ruin all of our wormhole fun.

However, this would immediately lead to a new possibility. There is strong evidence that our universe underwent an "inflationary" period early in its history, in which space-time expanded at a super-luminal rate and essentially created the entire observable universe in a flash. If we could initiate inflation in a small patch of space, it would inflate "away" from our universe - it would be as if our universe were a rubber sheet, and you glued a straw onto it and blew real hard, making it balloon out. This would be the creation of a whole new universe, connected to our with ... a wormhole. However, because the topology of space-time cannot change, this wormhole can never completely collapse. You will always have a doorway into a whole new universe. It might be a doorway that is hard to keep open, but it can never be sealed away forever.

You can use all the tricks we talked about elsewhere for maneuvering your wormhole end in the other universe and taking advantage of time dilation to wait for the baby universe to age, mature, and mellow out until it is able to support life-bearing planets. Then find a likely planet, open up the wormhole, and start colonizing. In this scenario, we will never colonize other worlds in our own universe. Alpha Centauri and Epsilon Eridani will be separated from us by the same gulf of light years we have today. But humanity will expand to other worlds, new worlds, in brand new sparkling universes we made ourselves.

In conclusion, there are two possibilities in physics - space-time topology can be changed and the universe is ours, or space-time topology cannot be changed and we can spin off new universes to play in when ours becomes old and thread-worn.

Citizen Joe said...

The universe is bigger than it is old. Which means that it is expanding faster than light. The theory is that space is being created. There is talk about vacuum energy bubbling up to the surface and whatnot. If space is being created naturally, that means space is malleable. Likewise, gravity is thought to bend space. That being said, we've seen no evidence of space changing its fundamental properties (changing from a sphere to a doughnut). But there's no way to be sure since we are withi the experiment, not looking in from outside.

Jean Remy said...

I swore to myself I would try and stay away from this because my previous effort (see On Torchships) left me trying to hold my brains inside my head by plugging my ears.

I'll toss a few ones in there anyway.

One good reason to not have a wormhole on any sort of real-estate you're not interested in vaporizing: what if it collapses? Furthermore, what if it collapses while a mass is in transit. I think Saber brought up the point of their collapse, but it was something I thought about when I was world-building, and I made the decision to place my wormholes at L4/5 points, not for any mystical gravitational mumbo-jumbo, but because I had the idea that should the wormhole collapse accidentally, to conserve information in the Universe at large, at the moment of collapse any mass inside the wormhole would be converted to the equivalent energy (Oh E=mc^2 is there anything you cannot do?) and spewed out both ends (half and half). Since I was dealing with 100,000 tonnes spaceships, the effects were... spectacular.

On Topology: what if there are wormholes already then, would attempting to create a wormhole destroy another one?

Let's take your coffee cup. The cup part is the asymptotically flat universe and the handle is the wormhole. According to that theory you can't make another handle because it would break the cup. So in a one-handle universe, is it possible somehow to create a handle elsewhere, or move said handle? Does the act of attempting to create a new handle spontaneously destroy the first handle? Is it simply impossible to do anything to that handle?

I can see an interesting scenario developing from Case #2. If there's only a set number of possible wormholes in the Universe, a "Wormhole Rights" accord would have to be signed between alien races, deciding how many wormholes each is allowed (think Washington Naval Treaty, but with wormholes) This of course could easily lead to Wormhole Wars where races try to seize wormholes from each other in order to expand... But I am getting away from myself again, which is why I was just going to sit and read, but it got the better of me and by brain hurts again.

Luke said...

Jean Remy: You bring up an interesting possibility, whith the case of a fixed topology but already existing wormholes. In this case, any existing wormhole can be altered, its shape changed, its ends moved, but it can never be destroyed, nor can any new wormholes be created. Events such as the creation of time machines or shrinkage down to zero mass would simply render the wormhole unusable for transport or sending information, but would still leave a microscopic relic that could be re-inflated and re-used. If you find a wormhole already in existence, you can take it, move the ends to useful locations, and alter the shape of the wormhole to allow for easy transport of people and goods. If you don't have a wormhole but an enemy of yours does, you can steal his wormhole and make it your own (if he wasn't an enemy before, now he is). Of course, it is not guarenteed that it is easy to do much to wormholes - they might mass as much as a hundred suns, for example.

As far as wormhole destruction, it is anybody's guess what happens. Your idea of the wormhole turning most of its mass into radiation could well be what happens, and is a perfectly valid fictional choice at our current level of understanding. On the other hand, you could also choose to have the failure modes be more benign, simply expelling the mass of the stuff holding up the wormhole. It is pretty certain that anything inside the wormhole at the time of collapse will be pretty mangled (at least), and probably chopped in half if only part of it was in the wormhole (for the case of a wormhole much smaller in length than the length of the thing going through it.

Thucydides said...

Next Big Future has an interesting speculation which sews up the Fermi paradox:

If wormhole technology can be used to create customized "pocket" universes for whatever race builds them, then there is little incentive to explore normal space.

As for wormhole weaponry, simply dunk one end into the interior of a star (the core if you can) and release the product in target space on or near the planet you are working to conquer. If the free end flaps around like a fire hose so much the better. If you can plant the firing end on a neutron star, either you get a gravitational vacuum cleaner or a spray of decomposing degenerate matter moving out the free end at relativistic speeds, either of which will spoil someone's day.

Jean Remy said...

"As for wormhole weaponry..."

I can kill you by shooting a gun at a counterweight, making it fall off a shelf onto on a weighted scale causing it to flip a switch that turns on the high voltage electrical plate you are standing on... Or I can just shoot you.

A degenerate-matter-spewing wormhole strikes me as a wholly unnecessary trick when nuking them with cheap and simple (relatively speaking) Tzar Bomba yield thermonuclear weapons gives you the same result.

I was talking in terms of accidents, or a cheap terrorist attack on an existing wormhole station, not a practical weapon of war.

Geoffrey S H said...

"House of suns" by Alastair Raynolds raises the point of a wormhole "flame-thrower". As a lareg scale strategic WMD I can see some uses for it...

Rick said...

Since I went through the turnstile, I guess I may as well sit back and enjoy the ride. (Lys: 35 minutes)

Let me test my understanding of the temporal implication for travel, and so ultimately for future history: polities, trade, wars, etc.

In my naive understanding, the natural tendency is for a long distance wormhole network to spread outward from Earth (or whatever source), but not to form loops.

So long as you are building a new branch, in human terms you can build it as quickly as your engineering tech permits - you can open a line to M31 in a year, if you dump enough money into the wormhole, and the fact that in some philosophical sense the far terminal is in the Year 2 Million makes no matter.

And you can travel through the network, from Scorpio-Centaurus to Orion, as fast as train operation (or whatever) allows. Whether or not you need a sleeping car or even a diner is the author's choice.

You can make round trips, again the full length of the network. Half the time you will be 'traveling into the past' (and the other half 'traveling into the future), but no matter how fast the trains go they never get you to any station before you left it last time.

BUT. If you want to build a bypass, or new connecting branch between two existing stations not now directly connected, you have to pay the temporal piper.

You can pay on a couple of different plans, but this is the one practical situation where 'real' travel times to all those places matters, because that determines how long it will take to establish a bypass line.

Which will strongly bias development toward a radial network with only one route between most stations, or at any rate neighborhoods.

Spawning parallel lines shouldn't raise issues, and local multiple connections are no problem, since normal space travel times for setup are short.

Luke said...

Rick: That sounds like an excellent summary.

Thucydides: Wormholes certainly have the potential to wreak awesome destruction. The energies and stresses needed to warp space-time to such an extreme can shred everyday matter as we know it as we would brush aside a cobweb. If an author wants to avoid this, she might invoke a very careful balance between the handwavium and unobtanium that keeps the wormhole stable, to allow some almost-cancellation whereby mere mortals (albeit technologically advanced mortals) can construct these doorways of the gods. This calls for some consideration, for space-time engineering of this caliber is both the unstoppable force and the immovable object. Your gateways to the centers of suns, or to the crushing depths of neutron stars, are withstanding forces that crush the very core of the atoms our day-to-day world is made of - giving you a shield and armor that can protect against nearly any threat that can be thrown at them, and the sword that can cut through any material save perhaps its counterpart in spacetime mangled beyond all recognition. Is the story to revolve around technologies that laugh at the most extreme phenomena science has yet uncovered? Or will we draw back to a more human scale, mere atom bombs and maraging steel, and say that the mighty engines that prop open these gateways are mere matter themselves, and thus subject to all of matter's weaknesses.

Either could be used for a fascinating story.

Francesco said...

Mmmmh, I tought about another consequence...

Let's take into consideration always our little Earth (A) and Terra Nova (B).
I create a route from A to B, and after reaching B I *collapse* the route. I then create a route from B to A, and when crossing back to A I'm 200 years in A future respect when I crossed. I go back to B, and let the route BA collapse.
In the meantime (!), in A past, they waited a pre-determined amount of time, and then sent from A to B a different wormhole, allowing me to go back to A after having visited its future, always without having 2 simultaneous wormholes open creating a timelike curve.

From this, I think we can deduct that, if causality protection does exist, the simple collapse of a wormhole is not a sufficient guarantee, so even for new wormholes, each extremity should have a "causality cone" that persist even after the collapse and that forbids the creation of new wormholes: in the case stated at the beginning, likely after the creation of the BA route I would not be able to send a new route from A past to B untill 200 years passed... or have I missed something?

Citizen Joe said...

Wormhole travel may actually require the collapse. Let's say gravity is able to bend space such that two distant points get connected. That particular topology always exists although the exact correspondence to our perception shifts about as the gravity wells which do the bending shift about. That doesn't mean you can pass through the connection, instead you need to 'open the door'. So you somehow make that door, enter it, then that door closes while the corresponding door on the other side opens and spits you out. This does nothing to sync up your velocity relative to your destination. It also makes short hops impossible since you A) don't have two large enough gravity wells within the same system and B) it is easier to bend a long distance around than a short one (take an 8 foot stick vs. an 8 inch stick).

Jean Remy said...

Another mind-bender, related to the topology issue.

If we take the view that the topology cannot change, and the there is a fixed number of existing wormholes that you can manipulate and bend to your will, so every trick we've discussed we can play with the two ends, then what happens when we *try* to violate causality with the new toy?

If the topology is unalterable, the wormhole cannot collapse to preserve causality, since no wormhole can be made or unmade. I guess there's still his energy discharge theorized to maintain the two ends apart in a configuration that prevents the wormhole from becoming a time machine, but it seems more dangerous for causality for the topology to be unalterable that alterable.

Jean Remy said...


I'm not sure that wormholes have a "length" in the way you seem to be thinking about. Luke pointed out (speaking on another matter: "and probably chopped in half if only part of it was in the wormhole (for the case of a wormhole much smaller in length than the length of the thing going through it." implying that even a light-year spanning wormhole may be shorter in length than a space ship, so shorter than 1 kilometer. I don't see a wormhole spanning a solar system be significantly smaller than that 100 ly/1 km long wormhole. The "length" of a wormhole might be entirely unrelated to the actual flatspace distance between the two end points.

Citizen Joe said...

No, I'm saying that the wormhole has an undefined length. The length of space that is being bent is where the 8'/8" bending thing comes into play.

Imagine two fairly flimsy sticks (8' and 8") laying on a table. These represent space between two points in flat space. If you push on both ends, both sticks resist change. Now suspend the ends of both sticks from the ceiling, representing the space between two gravity wells. The longer stick deflects much more and when you push on the ends you can relatively easily push them together. The shorter stick still resists bending. Where the stick bends back and touches itself is a wormhole. They may be naturally occurring all over the place but we don't know how to spot them or open them. The technological aspect would be some sort of sensor or predictor and then some sort of device to pierce through time space to get access to the wormhole.

Thucydides said...

Luke, postulating using wormhole technology to deliver nuclear weapons is somewhat akin to offering thermal imagers and laser rangefinders to neolithic tribesmen armed with atlatls. You could do it, and it would undeniably improve the tribe's effectiveness, but it would also represent a disproportionate ratio of effort to effect. Only a very rigorous process of world building (such as Larry Niven and Jerry Pournelle's "Mote in God's Eye") would allow for such a seemingly logical contradiction to work seamlessly in the story.

Judging from what I can understand of discussions of wormholes, I suspect that being able to manipulate time and space at that level will lead to physical principles far beyond anything we know or contemplate today, rendering things like fission, fusion or even anti-matter rather moot.

Even with the these limits of understanding, a wormhole would be the ultimate physical weapon, having a mass of millions or billions of tonnes, moving at relativistic velocities with respect to the outside universe while being set, acting as a conduit to almost anything and inducing massive distortions of space/time when brought near another wormhole. Unless you have the ability to create a pocket universe and "submerge", or have your own wormhole to fight back or escape with, being on the receiving end of a wormhole will be...eventful.

Even a "peaceful" wormhole parked at the Earth-Sun L1 point would have to be looked at with trepidation, since the owner might have a change of mind or an outside agency might decide to move their wormhole into the zone of influence of "your" wormhole for their own purposes.

Rick said...

I agree with Thucydides that if you have usable wormholes you probably have a whole new physics, and a host of technologies many of which nothing directly to do with wormholes as such.

How many of these will be weapons is purely worldbuilder's choice. It strikes me that - with the obvious, huge exception of nukes - relativity has scarcely been directly weaponized at all.

Nonexplosive nuclear energy revolutionized underwater warfare, but because of logistics, not weapons. I assume that relativity is implicated in radar and other systems, but not in weapons as such.

Lasers, I assume, are more about quantum mechanics, and in any case have not yet been used in anger as weapons in their own right, at least that I know of.

Oddly enough, Newton did not really revolutionize weapons as such either. After all, we already had guns.

Galleons, too, and Newtonian physics basically was developed after the fact to explain how cannonballs fly, and how galleons can get back home.

How coincidental!

Eric said...

Luke, I think I've figured out what the Minkowski diagram of a relativistic wormhole probe would look like:
Wormhole Probe
The red line from the origin to * is the path of one wormhole mouth from the earth to Terra Nova, at a high relativistic. The lines 1-1', 2-2', 3-3' represent the connection between the traveling WH mouth and the one staying at home. A-A' represents the final connection, which is spacelike. Earth experiences the final connection earlier than Terra Nova does because of the skewed connection line (The wormhole connection lines are lines of simultaneity from the perspective of the traveling WH mouth, as its space axis is skewed from the horizontal by its high velocity relative to earth and Terra Nova.)

Looking into combinations of three wormholes connecting three locations, there doesn't seem to be a way to avoid running into problems.
Three Systems Connection shows spacelike WH connections between three systems. On their own, none of them violates causality. However, when you get the path right, you've got a very timelike path to before you left your starting spot. This will happen for any cyclic path via wormholes where there's a possibility for net temporal displacement.
Given that unhappy state of affairs (Einstein comes to ruin the party once again), a system of wormhole connections would end up looking like a tree or bush, with lots of branches, but no loops.

Then again, there could be other arrangements that would allow for looping paths without upsetting causality. I hope there are, because a branching system wouldn't be able to do much about traffic congestion problems.

Jean Remy said...

"Judging from what I can understand of discussions of wormholes [...] rendering things like fission, fusion or even anti-matter rather moot."

I don't see WHY it would render current or near future science moot. The central principle of science is that discoveries and principles are additive, not substitutive. Breaking the atom has not lead to a wholesale conversion of weaponry to the new discoveries, it merely added weapons to our inventory. So while yes a wormhole weapon is conceivable, it also seems to be one of those uber-weapons you actually have in your arsenal so that someone else doesn't use it, but you would never ever *want* to use. In fact at this point dropping an H-Bomb seems preferable to unleashing that kind of power, it would be the difference between slagging a city and slagging an entire PLANET.

I suspect that even when we can manipulate wormholes 99% or our armament will be "traditional" weaponry (if you count hypersonic railguns and lasers as traditional)

Luke: It won't help congestion but the planet at the root of the system is going to get filthy rich. Or nuked. It's fun to be at the top.

Jean Remy said...

Rick: good point about nuclear power in a logistics sense. Can singularities and wormholes be tapped *for* power rather than costing vast amounts of energy to create and maintain? That might make things really messy in terms of causality if we now have ships or planets poking holes in the fabric of reality to get at that sweet sweet power mmmmmh.

Eric said...

This would be a very literal case of "All roads lead to Rome."
... and Rome got very rich, and then eventually got slagged.

Also, in wartime such a network would lead to a very bad case of gatecamping. There would only ever be one good path between two systems (unless you want to slog for an eternity through flat space), and whoever controls that path controls all access from the one system to the other.

emdx said...

Not much time to read the whole thread (that’ll come later), about wormholes, well, in Star Bridge, Jack Williamson had all the “wormhole/tubes” that connected to Eron* sitting on a huge building at the north pole, floating on an inches-deep sea of mercury and which rotated with the planet…

* All similarities of a last-century energy company are, hopefuly, totally fortruitious…

Luke said...

Jean Remy: If you have "tough" wormholes, the kinds you can drop into the core of a sun or onto a neutron star, well, you can drop one into the core of a sun. Now you have fusion hot plasma at your beck and call. Shoot the jet from the stellar core into a magnetohydrodynamic generator and you can get power out of it.

I suspect that if you have wormholes of this magnitude, however, you can also violate baryon conservation. Perhaps you can make micro black holes that instantly evaporate, turning their mass into radiation. Or perhaps you can make an exotic vacuum state which has different stable particles than ours, so that anything going into the exotic vacuum state and back out becomes a spray of radiation. Or perhaps you can make "non-orientable" wormholes which, in addition to mirror reflecting everything that goes through them, also turns things that go through them into antimatter. All of these methods give you more efficient and probably more convenient energy sources than dropping a wormhole end into a star.

For the case where space-time topology cannot be altered, but there are already wormholes in existence, then causality can be preserved if either wormholes collapse down so small that noting can get through them, or if the incipient formation of a time machine creates forces that prevent the wormhole from reaching a time machine configuration (maybe the wormhole end bounces away. Maybe the length of the wormhole stretches so that the extra distance it takes light to go through the wormhole is adds enough time to the trip that you don't get a time machine).

Luke said...

Re: Wormholes as weapons - it might well be that wormholes can also be used as defenses, as well. If your wormhole can survive nuclear fire, then perhaps you can just interpose a wormhole mouth between you and any incoming attack. Perhaps you can move your cities inside wormholes, or inside pocket universes connected to ours via wormholes, for protection, and just close down the mouth to microscopic dimensions in times of peril.

Of course, it is not necessary that wormholes will be uber weapons. For all we know they are delicate things that collapse at the slightest provocation. Very delicately balanced and ephemeral - go through one too fast or look at it cross-wise and it may pop like a soap bubble. I could suspend my disbelief for either option.

Luke said...

Eric: Your diagram looks correct to me. You are right that for round trip wormhole connections, it is easy to get configurations that result in time machines. In the torch-ship thread, Jim Baerg suggested that you could form a closed loop with four wormholes - Earth could send a wormhole to Terra Nova and to Johnsworld, and then Johnsworld and Terra Nova could each send a wormhole to Confluence. So long as the time lag from the Earth-Terra Nova line plus the time lag from the Terra Nova-Confluence line was equal to the time lag from the Earth-Johnsworld line plus the time lag from the Johnsworld-Confluence line, it looks like the configuration doesn't give you a time machine. You are going to need to be careful setting up the wormholes to make sure that everything is coordinated correctly, and keep a careful watch to make sure that an extra bit of time dilation somewhere doesn't force one of the connections to collapse. I may be missing something, though. If you check it out, you might see something I overlooked.

Eric said...

The logic makes sense to me, Luke.
As long as you could keep time dilation effects from relative motion compensated for, I think it would work, though the builders would have to be annoyingly precise about the whole arrangement (any wormhole loop would be sitting on a knife-edge of allowed causality, not a very comfortable place to be).

One thing that would give you a little more of a buffer would be to make sure that the wormhole mouths in a given system are all spaced several light-hours away from each other. This is puny compared to the several-decade Δt for an Interstellar Wormhole Express&reg, but just enough to give the custodians a bit of breathing room before the loop tries to tear itself apart.

M. D. Van Norman said...

If wormholes are propped open with negative energy, then wouldn’t that energy also have to be overcome by anything trying to traverse a wormhole?

Eric said...

Reminds me a comment in Carl Sagan's Contact: "If we don't engineer a consistent causality, it'll work itself out, and then it's almost always worse." (Excellent book, still one of my favorites)

Luke said...

Francesco: I am not sure I follow exactly when the wormholes are being created and collapsed. For example, I see a timeline of something like this:

2100 GMT: Earth sends out a wormhole to Terra Nova.
2101 GMT: Earth sees the Terra Nova wormhole arrive. You step into the wormhole. earth sees the wormhole collapse.
2201 GMT: The wormhole arrives at Terra Nova. You arrive at Terra Nova and collapse the wormhole.
2202 GMT: Bored of Terra Nova, you send a wormhole back to Earth.
2203 GMT: You see the wormhole arrive at earth. You step through to go to Earth.
2303 GMT: The wormhole arrives at Earth. You arrive at Earth.

Now when does Earth send a second wormhole to Terra Nova? I'm guessing from your description that we have events something like
2150 GMT: Earth sends a second wormhole to Terra Nova.
2151 GMT: Earth sees the second Terra Nova wormhole arrive.
2251 GMT: Second Terra Nova wormhole arrives.

If this is the case, then at sometime before your wormhole arrives at Earth, you would have the situation where a light signal from Earth could go through your wormhole back in time to Terra Nova, then go from Terra Nova to the wormhole en route from Earth, then back in time to Earth to arrive at or before it left. If we accept Hawking's chronological protection postulate, at this point the fluctuations in the electromagnetic field would build up around this loop until one or both wormholes was destroyed.

Or were you thinking of something else?

Luke said...

M. D. Van Norman: Not necessarily. There are wormhole geometries, such as the Visser wormhole and many of the thin shell wormholes, where travelers can go through the wormhole without ever directly encountering the negative energy regions. In these wormholes, the wormhole is supported by a "frame" of negative energy stuff, and the regions between the frame acts like perfectly normal space-time for all purposes.

Most research, however, has been done on spherically symmetric wormholes. When this constraint is applied, everything going through must cross a boundary where the negative energy stuff is. This need not be a deal breaker. For example, negative energy stuff may not interact with normal matter, so we would just go right through it. Alternately, you can build your wormholes so they are mostly spherical, but with windows. In the windows, there is no negative energy stuff, and you can go through there.

Luke said...

Eric: This could give you a distinction between the "rail lines" and the "shipping lines". Rail lines are part of the original branching network. You can just buy a ticket, hop on a passenger rail car and go anywhere the wormhole network goes to. However, if you have to do a lot of backtracking, this might be quite a long journey.

Meanwhile, the shipping lines are systems linked together by the secondary loops. The extra padding they need in the form of light hours of separation between the ends means you need to cross these gaps on spacecraft. Sometimes it is more convenient to take a spacecraft across a direct shipping junction rather than backtrack through many star systems.

Anonymous said...

Ok, I'm back and I have a few questions:
1. How much power/energy does it take to create a stable (one that you can traverse) wormhole? Can Uncle Ernie build one in his backyard or does it take a warehouse full of equipment and a good chunk of the national power budget to create?
2. If wormhole mouths are connected by a 'tunnel' through extra-cosmic space, then why can't we create a wormhole with one end on Earth and the other ANYWHERE in the universe? Without physically sending the 'distant' end anywhere?
3. How 'durable' are wormholes? Do they collapse after one transit, or can you go back-and-forth all day long?
4. Do wormholes, in fact, 'weigh' anything at all? Are wormholes made of 'stuff' or are they artifacts of space-time?

I'd like to know what you all think about my questions.


Anthony said...

One probable reason for wormholes to be in orbit (rather than ground-based gateways) is that it's not clear how you anchor a wormhole to a solid frame (whatever a wormhole is made of, it's unlikely to be conventional matter), and thus it will have a tendency to fall if placed on a planetary surface, with results that are likely to be somewhere between unfortunate and catastrophic.

Luke said...


No one knows. There are wormhole geometries that have no net energy at all. Presumably, a wormhole of this nature could be created without any energy or power. Since the total energy of a wormhole (divided by the square of the speed of light) is the wormhole's mass, the more massive wormholes have more energy. However, it may be that much of this energy can be supplied by the mass-energy of random junk - just stuff the wormhole full of rubble.


The wormhole tunnel is not through extra cosmic space. The tunnel of the wormhole is like normal space-time. It is just space-time with an odd geometry. This can be difficult to visualize. Anyway, the reason you create the wormhole ends close together is that physics is local. If you want to cause an effect a million light years away, you will need to propagate some physical effect over those million light years, which will take at least a million years. And who wants to wait a million years? Also, we have no idea how this could be done even in our wildest theories.

A more physically plausible mechanism is to somehow "tear" spacetime to give it a small loop. The loop is a wormhole, and you can now grab the ends and work with them and send them wherever you want.


The first wormholes ever envisioned collapsed before one transit, making them not very useful. The wormholes described in more modern scientific work seem to be able to last indefinitely, no matter how many trips you make across them. It is very likely, although by no means certain, that wormholes will collapse before they become a time machine, or before one end gets a negative mass.


Wormholes do "weigh" something. They have mass. They act like any other physical object in this respect. In addition to mass, wormholes also have electric charge, momentum, and angular momentum.

So far we do not know what wormholes are made out of. What they are is a "loop" or "bridge" of spacetime. However, we do know that they need something with a negative energy density to keep them open, and they probably need something with positive energy density to give them mass. The positive energy density stuff might end up being normal matter. In fact, you might need machinery made out of normal matter to make the negative energy density stuff that holds the wormhole open. If this is the case, part of the wormhole is "stuff".

Thucydides said...

Why would nuclear fission, fusion or anti-matter be moot in a universe where intelligent life can manipulate the fabric of space/time?

Probably the same reason muskets, Stirling engines and Leyden jars are no longer in common currency. There is no doubt that modern materials and manufacturing could be used to make far more effective versions of these devices, but they were superseded for good reasons.

Jean Remy said...

We still use muskets.

A modern rifle uses the exact same fundamental physical properties of a rapidly expanding gas created by igniting a powder to propel a small lead slug down a tube.

We still use Stirling Engines.

The Mars Science Lab project is running tests on SRG, a prototype Stirling engine using a pellet of Pu238 as heat source.

We still use Leyden Jars.

Capacitors are more advanced Leyden jars that use better materials to the exact same effect, the storing of electrical potential in plates separated by a dialectric.

Do not confuse advances in technology with the abandonment of the scientific principles behind obsolete technology. Once again, science is additive, not substitutive. You do not abandon previous discoveries in your foray forward, you add to your arsenal of knowledge.

Unless you can create wormhole "rifles" or wormhole "grenade launchers" or any form of wormhole weapon that does less than slag an entire planet, you will not abandon previous types of weaponry or devices. So far we have not come up with any form of technology that renders all previous discoveries moot.

The nuclear bomb has not slowed or even stopped the creation of powerful conventional bombs. In your theory, since we can split the atom there's no need for Daisy-Cutters and MOAB. Evidently the US Army believes differently.

Science is like a Swiss Army knife over a Bowie Knife. Sure you can open a can of baked beans with a Bowie, but it's a lot less messy to use the can opener. If you're careful you can pick your teeth with a Bowie, but you know, toothpick works just as well without the whole cutting your nose off accidentally issue. And I wouldn't want to try and open a bottle of Mouton-Rothschild 1892 with a Bowie. Not that you couldn't open it with a Bowie Knife, but you might want to enjoy the contents.

Rick said...

Jean beat me to the punch: An assault rifle is simply a musket - more precisely an arquebus - with rapid fire capability and some other refinements.

(A musket was originally an armor piercing super-arquebus. As armor disappeared it shrank back down to arquebus dimensions.)

Chemical explosives and propellants are so compact and powerful that even another scientific revolution may not displace them in weapons, just as nuclear energy has only displaced them for Really Huge Explosions.

Or it could go the other way just as well, with a new physics enabling 'disruptors' or whatever. In that case chemical-powered guns might fall out of use entirely, or survive for use in a pinch, more or less the way the bayonet has survived from the age of edged weapons.

M. D. Van Norman said...

I assume negative energy also creates negative gravity, so the ability to shape it would certainly be useful. Getting some would be the problem.

Presumably tiny quantities could be produced in high-energy particle colliders, but I imagine that the big naturally occurring sources will be out in the intergalactic voids. We could be stuck needing “conventional” starships to collect significant quantities of the stuff.

Luke said...

M. D. Van Norman: We know of several examples of negative energy. It is generally not stuff that is there, but stuff that isn't there. Or perhaps a bit more accurately, precluding even the possibility of stuff being there. For, as it turns out, even the possibility of something is worth a bit of energy.

Perhaps a concrete example would make more sense. In perfectly empty space, you can have all sorts of electromagnetic waves - radio waves, microwaves, infrared, visible light, x-rays, and so forth. The possibility of each and every frequency, direction, and polarization (called a "mode") has a bit of energy. The sum of all those bits of energies-of-possibility (often called "zero point energy") ends us giving our reference point for what zero energy is - it is this value against which other values of energy are measured for determining space-time curvature (for the nit-picky - this neglects dark energy, which is a negligible effect over the scales which we use to build wormholes).

However, all electromagnetic waves are made of electric (and magnetic) fields. Electric fields can be shorted out by a conductor. So, if you have two parallel conductive surfaces, the only electromagnetic waves that can exist between them are those in which the electric field is zero at the surfaces. This restriction means you can only have an integer or half-integer number of wavelengths of EM waves between the two conductors. In particular, wavelengths of EM radiation that are longer than twice the spacing between the two conductors simply cannot exist between those two plates. Since the space between the plates does not allow the possibility of those waves existing, they cannot contribute their energy to the total energy of the space between the plates. Thus, the space between the plates has less energy than space in which there is no such restriction. Since we measure the energy relative to the energy with all the modes of EM radiation allowed, the region between the plates has a negative energy density.

Unfortunately for our purposes, the density of negative energy is very weak for reasonable plate separations. You would need your plates to be closer together than an atom to hold open useful wormholes - a meaningless distinction for materials made out of atoms. We might make use of similar effects from different kinds of barriers. We know that the event horizon of a black hole has a negative energy density from much the same sort of effect. Perhaps the space-time of a wormhole could be curved to only allow very restricted sets of modes of vibration - not only of EM radiation but also of gravitational radiation, gluons, weak vector bosons, leptons, and quarks. This might be able to hold up the wormhole, by using its own shape to support itself.

Of course, if you did find particles that naturally have negative energy, those would work, too.

M. D. Van Norman said...

Actually, I was thinking of “dark energy” and “negative energy” as being the same thing. My mistake. Dark energy, then, would be the “cosmological constant” (AKA quintessence, AKA antigravity, etc.), the force that is continuing to accelerate the expansion of the universe.

I’m assuming we still don’t know much about the stuff. However, I figured it might be handy for prying open wormholes.

Anonymous said...

So...the answer to my questions is...maybe? Kinda-sorta? We think think so, yes? Wow. Pretty sure, until we actually find or make one of the silly things and find out how wrong or right we are about them.


Anonymous said...

Ok, after reading that last post, it really sounded I apologize for being so condicending.


Luke said...

M. D. Van Norman: After checking some of my references, it looks like a cosmological constant will not suffice for propping open wormholes. Going into the reasons will probably bore people here, although I can drone on about the technicalities of weak energy conditions and null energy conditions if anyone wants to hear about it. Thus, unfortunately, dark energy does not serve our purpose. You are right, we still don't know much about it, although it is thought to be a property of the vacuum state of the universe.

Luke said...

Ferrell: While we can put some bounds on what is possible, and deliver a few simple theoretical examples, there is a lot we do not know about wormholes. From the point of view of an author, this is a good thing! If the author wants his wormholes to have 1,000 km long tunnels, that must be carefully navigated by trained experts, he can have it so. If he wants characters that are still recognizably human to not be able to go where they will, he can say that the minimum mass of a wormhole is slightly more than that of Jupiter - far beyond what people are capable of engineering - and all travelers have to use ancient relics of a long vanished race.

Anonymous said...

Going back to the idea of a bypass line from Terra Nova to Johnsworld to avoid the congestion at Earth:

If wormhole mouths can be inflated/deflated at will, Terra Nova could just create a wormhole pair, set the mouths to the size of a packing crate, and ship one end through the Terra Nova-Earth wormhole, and then through the Earth-Johnsworld wormhole. The new wormhole could then be inflated up to train-car size creating a direct link between Terra Nova and Johnsworld.

The new connection is essentially completely space-like since the wormhole network connects Terra Nova to Johnsworld at the same time in the co-moving reference frame, and the transport of the new wormhole mouth occurred at non-relativistic speeds. So the resulting loop is no closer to time-like than the original pair of wormholes connecting the three stars.


Anonymous said...

I have some concerns with the overall premise of having point-to-point wormhole connections to distant planets.

I understand that the local conservation of mass-energy (as viewed from asymptotically flat space, yadda yadda) removes the problem of the two planets being at points of different gravitational potential energy, but I don't see how the space-time patch between the mouths would handle them being in different accelerating frames of reference.

Let's say one end in on Earth's surface and the other on the Moon's. I'm not sure how the 9.8 m/s^2 accelerating frame would mesh with with 1.6 m/s^2 accelerating frame through the wormhole connection.

Obviously these problems operating on different planetary surfaces would be multiplied during the process of shooting one mouth out of an electric cannon towards another star.

Is there some natural way that the accelerating frames of reference should mesh, or would you need to dynamically maintain extreme density distributions of mass-energy to make it happen?


Eric said...

Matthew, that wormhole trio scheme you mentioned looks crazy enough it just might work. You'd have to be exceptionally careful during transit, though, to avoid making even a slightly timelike path when you've just gone through the first wormhole connection carrying your worm-minihole. Get the movement and/or timing wrong and you could make someone very angry when their wormhole suddenly collapses/explodes/wings off into the void. Once you've made it to your final destination (without wrecking the rest of the network along the way), as long as you're extremely careful about the Δt differences between your wormhole and the others along that path, your new connection ought to be fine.
Once again, any loop will need constant adjustment to make sure it doesn't turn into a timelike path (your margin of error is going to be proportional to the distance between mouths of consecutive WH's in the loop relative to the distance between the mouths of a single wormhole, i.e. the distance of a few light-hours relative to the distance of several light-years in the case of the Interstellar Transit Loop - means a tiny margin for error).

M. D. Van Norman said...

To bring the discussion back a little closer to reality, how might a wormhole transportation network be detected at interstellar distances?

Jean Remy said...

Threading a wormhole through a wormhole? Isn't that asking for trouble? Is that even possible? It seems to me even trying that would cause a lot of weird interactions. I mean you're basically sending space warped into non-Euclidean geometry *through* space warped into non-Euclidean geometry.

This sounds like the kind of thing that could create a paradox that will destroy the Universe. Or we could get lucky and it is localized and will only affect our Galaxy.

Luke said...

Matthew: Like Eric, it looks to me like your method for creating loops out to work. Also like Eric, it looks to me like you will need to be careful about keeping your time lags carefully tuned. As with the four-leg-loop, you can gain a bit of tolerance by putting the ends of the wormhole that completes the loop several light hours away from the ends of the first two legs.

As for the question of what happens when you have wormhole ends on planets with different gravities - the answer is that we simply do not know. As far as I am aware, all theoretical investigations of wormholes have had isolated wormhole mouths in otherwise flat space-time. However, we can make some guesses as to what happens. To do so, I will make an analogy with the behavior of electric charges and fields as they approach a wormhole.

Imagine a positive charge located some distance away from a (uncharged) wormhole mouth. Field lines radiate away from this charge in all directions. It is important to note for our purposes that field lines can only start on positive charges and can only end on negative charges. Since the source charge is initially far away from the wormhole, almost none of its field lines will go through the wormhole - they radiate away into the more or less flat space-time.

Now imagine bringing the source charge closer to the wormhole. Those field lines cannot break - they must remain outside the wormhole mouth. These field lines are bending away from the wormhole mouth, as if they are being repelled by it. This is the same behavior as if the wormhole had acquired an electric dipole, with the positive side of the dipole pointing toward the source charge and the negative side pointing away.

As an aside, you can now see why the wormhole will acquire the charge of anything that goes through it. If you send the source charge through the wormhole, the field lines must still connect back into the flat space-time region where the source charge used to be. They will thread through the wormhole to emerge through the mouth, looking for all the world like a positive charge.

But now lets take this analogy to gravitation. A nearby mass will have its gravitational field lines repelled so as to bend around the wormhole. It will appear as if the source mass induces a mass dipole in the wormhole mouth. This will be superimposed on any mass that the wormhole already has. Since the direction of force is always along the field lines and the magnitude of the force is proportional to the density of field lines, as you approach the wormhole mouth the gravity of the planet will seem to fade away and you will be left with only the gravity due to the mass of the wormhole end.

To be rigorous, we would need to solve this problem using Einstein's field equations for general relativity rather than the Newtonian approach of treating gravity as a field. However, this analogy does work in other situations, so it might not be too far from the truth here.


Luke said...

Jean Remy: The geometry of threading one wormhole through another works out, and there are no known physical mechanisms that would prevent this from happening. Whether there are unknown physical mechanisms that would cause problems is an issue for the author to sort out.

You can think of it like this - imagine a ball with two handles - loops that are stuck onto the ball like coffee-cup handles, sort of like this .
The two handles are the wormholes, and the ball is our normal space (just space now, not space-time). The places where the handles are attached can move around the surface of the ball, just as we can move wormhole mouths around. Now note that the surface of the handles is just an extention of the surface of the ball. There is no reason one end of a handle couldn't drift up onto the surface of the other handle, then go across it and out through the other end. That's how the geometry of moving one wormhole through another would work - except in 3+1 dimensional space-time rather than a 2 dimensional spatial surface.


Eric said...


I'm not sure. Given Luke's description of the effect of wormhole mouths on electric charge and gravitational fields, I wonder if a wormhole mouth might create the opposite of gravitational lensing (a diverging rather than converging lens effect). If that were the case, how big would the effect be? No idea. Could we detect it? Maybe (YMMV).

Anonymous said...


Dazzler weapons have been used by police and military forces in limited roles. And at least one moron in my city was hit with criminal charges when he shone his laser-pointer at aircraft. Including the police helicopter.


Rick said...

I think the detectability of wormholes, like most things about them, is currently author's choice. In fact the only really mandatory element, in story terms, is FTL restrictions that rule out timelike paths (and make loops very restrictive).

Usability as weapons, detectability, physical stargate structures or otherwise, location on a planet or in deep space, all seems that it can be pretty much finagled as desired.

Citizen Joe said...

One could hypothesize that there are many or few natural wormholes in which the time dilation has already propagated and thus no time travel with their use. Those natural wormholes, from a story perspective would probably require some sort of difficulty accessing them. i.e some sort of lost tech gate opening device. New wormholes could also be created by man with some new tech, however these wormholes would need time to 'mature' by either propagating to their end point or have bad time travel issues. As such, a setting could have both distant transport wormholes as well as time traveling wormholes as the plot demands. Personally, I'd put serious deleterious effects on the time travel ones.

ushumgal said...

I think my brain has finally imploded. Relativity makes me want to curl up in a corner and weep...

However, if I’m not mistaken, short-range wormholes could easily avoid any of the time-machine issues, since the mouths of the wormhole could be moved at slow speeds, so avoiding getting mixed up with all that relativity stuff…

Someone on the other thread mentioned that local wormholes would make great space elevators. But could they not be used in the opposite direction? In effect, they could be a more plausible version of the Star Trek transporter. Starship Indefatigable goes into orbit around unexplored Planet X, sends a wormhole mouth down to the surface, the landing party (led by an unfortunate guy in a red uniform and with no last name) walk into the airlock which leads to the other wormhole mouth and they step onto the surface of the planet. One interesting ramification of this system is that, unlike the transporter, the wormhole works both ways, so conceivably the warlike natives, brandishing their spears and waving their antennae menacingly, could storm the ship via the wormhole. So the wormhole airlock area would likely be fortified in some way.

In fact, short range wormholes would make boarding a viable attack method…indeed, perhaps the preferred method. Open a wormhole mouth in the engineering room of an enemy ship, send your boarders in and seize her. Of course, your ship would be equally vulnerable to such an attack. Which means that those fancy battle-armored marines, not particularly useful in a universe where starships vaporize each other from enormous distances, suddenly become quite important. If wormhole mouths have mass, then they’s have to be shot into the hull of the other ship like a bullet (perhaps a proton-sized bullet), and then inflated. So armor would also be important, and most likely, engagements would take place at a dramatically close range. After all, where is the fun in opening your wormhole mouth in a ship clear across the system?

Anonymous said...

ushumgal said...

Kirk: "Master-at-Arms! Post troops at all critical stations and prepare to repel boarders!"

Something you never hear on the original Star Trek, but it might have lent a slightly piratical air to some of the battle scenes...


Luke said...

ushumgal: With short range wormholes, you will still need to worry about details like forming loops that allow you to go back in time by a microsecond, or returning one of the mouths back very close to the other one, or having a long term wormhole connection between two points with different gravitational potentials (and thus different gravitational time dilations), but you are right - the effect is less extreme and for the purposes you are talking about (instant transport from a spacecraft in orbit to a planet) you really don't need to worry unless the planet already has a pre-existing planetary wormhole transport network.

You do need to take into account local conservation of mass. When you your transporter wormhole lands on the planet, it will need to suck up a lot of stuff (air, dirt, sticks, hapless locals) in order to balance the mass of the guy you will send the other way. This could mean that if you are sending down a landing party of 12 men (1200 kg total, say, including gear), you only need to suck up 1200 kg from the planet plus whatever extra you need as a safety factor. The the natives trying to invade the spacecraft can't send much more than 1200 kg of boarding party onto your spacecraft before the wormhole collapses (probably chopping one of the invaders in half).

Rick said...

The really scary thing is that there are people - including commenters here - who understand General Relativity, or at least can use the mathematical tools.

Using wormholes as a Trek style transporter has some constraints (I believe), but no show stoppers. For that matter the constraints might limit the plot killing problem of getting out of jams too easily.

You can't just open a wormhole somewhere; you have to move the wormhole mouth to that location. But you can position it while the tunnel is smaller than a nucleus, then inflate it, so locked doors are no barrier.

And as you suggest, you'd have to station anti-boarder teams at all critical point, because the attacker is not limited to the airlocks.

Rick said...

Among other things, I can't go back in time to avoid having crossposted with Luke.

Tony said...



Except that frames of reference are not interpenetrable. Nor are they importable. At 1/1200 dilation, for every minute of time that passes at the wormhole mouth on Earth, only 1/20 of a second passes at the moving wormhole mouth. And yes, each wormhole mouth is a distinct object that exists in its own frame of reference. What happens to objects that attmept to transit form one frame of reference to the other, and how the extra-dimensional internalities of the wormhole handle that, is the interesting question.