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Mapping a Galactic Transit System

I love the London Underground and have a great fondness for wandering about the city with a tube map stuck in my pocket. My wife and I last did this a few years back, making an early March trip in which we rented a Bloomsbury apartment for ten days and hopped all over the area, station to station, emerging for blustery walks to various historical sites (we were both, at one time, medievalists), then ducking into nearby restaurants for tea and warming up, talking about what we had seen and examining the map for our next stop.

A map of the London Underground is a schematic diagram that has a beauty of its own, reducing a city beyond its topography to a sequence of formalized connections and zones. The fascination is in the abstraction of the familiar, rendering distance and space intelligible. Now look at what we might call a ‘tube map’ of the Milky Way, as produced by Samuel Arbesman, a postdoc at Harvard with an interest in computational sociology and, obviously, big maps.


Click on the image to see Arbesman’s larger version of it, which in turn links to a downloadable PDF. This is the route map of what Arbesman calls the Milky Way Transit Authority, inspired by his recent re-reading of Carl Sagan’s Contact and the notion of a vast subway handling galactic traffic. Remember its main hub?

And swimming into her field of view as the dodec rotated was… a prodigy, a wonder, a miracle. They were upon it almost before they knew it. It filled half the sky. Now they were flying over it. On its surface were hundreds, perhaps thousands, of illuminated doorways, each with a different shape. Many were polygonal or circular or with an elliptical cross section, some had projecting appendages or a sequence of partly overlapping off-center circles. She realized they were docking ports, thousands of different docking ports — some perhaps only meters in size, others clearly kilometers across, or larger. Every one of them, she decided, was the template of some interstellar machine like this one. Big creatures in serious machines had imposing entry posts. Little creatures, like us, had tiny ports. It was a democratic arrangement, with no hint of particularly privileged civilizations. The diversity of ports suggested few social distinctions among the sundry civilizations, but it implied a breathtaking diversity of beings and cultures. Talk about Grand Central Station! she thought.

Well, the London Underground was never like what Ellie Arroway saw, but I still love it. Ramping up to a galactic scale reminds me, too, of Jon Lomberg’s Galaxy Garden, which renders our vast city of stars in the form of a gorgeous botanical display. I think Arbesman is right in saying “…there is power in creating tools for beginning to wrap our minds around the interconnections of our galactic neighborhood.”

Maybe we’re at the dawn of the era when the galaxy will begin to be represented as a more or less familiar place, rather than a vague stripe of stars across the sky, all but unnoticeable unless you get away from city lights in many parts of the world. That sense of context, of our place within that part of the universe that is immediately around us, is one we need to explain and enhance for our children. Astronomy education can do this, and it doesn’t always hurt to include a bit of whimsy — check out Arbesman’s MWTA tote bags!

Comments on this entry are closed.

  • AlfaCentavra March 13, 2009, 10:37

    We must seek ET’s. Why? From ET’s we can receive the very valuable information. For example it could be a new superbomb design. ;-)

    The extraterrestrials can destroy the humans very and very easy. How is it possible? They could give us information which will bring humans to self-destruction.

  • James M. Essig March 13, 2009, 21:22

    Hi Folks;

    One can imagine quite literally a galactic subway system composed of a series of accelerator tubes or mass drivers that is somehow set rotating along with the galaxy.

    The main caveat is that the connections of the tubes and the tubes themselves would need sufficient mechanical strength so as to not pull itself apart under its own rotation induced centripital tension.

    The really cool thing about such a system is that the energy used to accelerate cars within the system could be extracted by magnetic induction breaking and recycled over and over again to accelerate cars or trains down the transit tubes.

    Car acceleration velocities of one G should enable one to sport about anywhere within the Milky Way in one average human familial generation car time. Higher Gs are possible but some sort of G force cancellation would then be required to make the trips confortable and survivable over the long transit times.

    If there is a hyperdimensional component to the Milky Way which has been overlooked by general relativity, perhaps such a system could be extended into or interfaced with higher dimensionsal space time wherein the quantity of traffic could be greatly increased. The travel tubes might not even be required to take the form of wormholes, but rather simply perhaps only electrodynamic mass drivers.

    I have always been enamored with such concepts well before I even new the basic equations of Lorentz Transformation or for that matter, even high school algebra. I remember having some dream as an 6 or 7 year old at night wherein I imagined traveling down a highway in some sort of dark environment in a car at light speed. Obviously, my childish images of what it would be like to travel down such a road at C, were whoafullly inaccurate, but the dream left so much of an impression on me that I still think of the dream at times when I am driving long distances at night.

    Either way, the concept of a Milky Way Subway is indeed very whimsical and might actually be built at some future time frame. Everytime I ride on the Washinton D.C. Metro Subway, I seem to start thinking about such travel as well as wormhole travel. The small subway fare is worth the mental imagery.



  • andy March 14, 2009, 7:43

    Why’d you want a matter-based system? The mechanical strength issue would be far worse than for ringworlds or Dyson shells.

    Use Krasnikov tubes instead. They have the advantage of being able to do FTL.

  • Didac March 14, 2009, 7:59

    Maybe there is a Milky Way Subway functioning now, or out of function since a couple hundred millions of years. But if there is no Milky Way Subway by now (more than ten billion years after the first stars in the galaxy)…

  • george scaglione March 14, 2009, 9:51

    alpha,about that superbomb design we might be able to get – lol!!!!! – i fear you might not be wrong but still in an oronic why i found your comment very funny!! thank you george ps i can only once again thank everyone for the great thoughts above…KEEP THINKING everybody! that is how we will eventually get all that we want! transit system peace warp,fusion, antimatter drives etc etc you name it!

  • Casey C. March 14, 2009, 14:07

    What I don’t understand is that we have limited ourselves to thinking within the confines of what “laws” exists; And yet we introduce paradoxes. Space-time is a construct, therefore there is a framework to reverse engineer. In the “big bang” what came first; Light or Expansion? I believe there is another way in which we can go about looking or creating spacetravel. Light can be slowed and it proves that it cannot be the fastest. I believe there is an underlying factor that we are missing. I look at research work on “manifolds” and realize there are behaviors that reflect another manner of space. We just need to put our fingers on it. Gravity, mass, and I believe TIME is a by-product of this.

  • James M. Essig March 14, 2009, 15:43

    Hi Andy;

    Thanks for the insights regarding Krasnikov tubes.

    The mechanical strength properties of such a material based galactic tubes transit system would indeed need to be much superior to that of ring worlds or Dyson Spheres, however, perhaps the issues of such strength requirements might be mitigated if the tubes were of a spiraling form of layout much like the spiral arms of the Milky Way Galaxy. The tubes could more or less rotate at naturally set velocities with the natural rotation rates the exist at each differential radial position from the galactic center.

    In the case that the transit tubes would stretch as a result of differing angular rotation rates at differing radial distances from the center of the Galaxy, perhaps the tubes could have some sort of nanotech based self assembly feature by which they would incorporate interstellar gas into their composition thus causing a gradual elongation of the tubes. A growth in tube length of one micrometer per meter per year, would enable the tubes to double in length in only one million years, a growth in tube length of only one nanometer per meter per year would result in the doubling of the tube length on one billion years which should be more that adequate for matching the elongation rate of the spiral arms of the Milky Way Galaxy.

    The tubes might also be composed of some form of high strain capable elastic material so that they can stretch as the natural dynamics of relative rotation rates at differing radial distances from the center of the Milky Way would tend to stretch the tubes out. If the tubes could stretch like rubber bands, they might be able to double their length every 3 billion years and still not snap after 10 billion years. The gradual incorporation of material into the tubes from the interstellar medium would no doubt mitigate this problem.

    Alternatively, the tubes might be constructed of exotic materials such as some form of femtometer or so thick stabilized neutronium or quarkonium. One square meter of femtometer thick sheet of neutronium has a mass of only one metric ton and so a 100,000 light year long tube of neutronium with a linear mass density of 1,000 metric tons per meter would have a mass of only (10 EXP 5)(10 EXP 13)(10 EXP 3)(10 EXP 3) metric tons or 10 EXP 24 metric tons or about 0.001 solar masses. An assemblage of such tubes composed of a billion such highway travel tubes would only have a mass of one million solar masses or about one 3 millionth of the mass of the Galaxy.

    Still if Krasnikov tubes can be developed, they would be a much better option.



  • Adam March 15, 2009, 18:05


    Neutronium is unstable and decays into a proton/electron plasma with a 15 minute half-life. Neutrons only stay confined under pressure and even then they’re continually decaying and reforming. Quarkonium, when the colour and EM charges are balanced, is stable, but its residual nuclear force is too strong for it to form sheets.

    Higgsinium or monopolium might do – if they can be made. We don’t yet know the properties of higgsinos or even if SUSY explains this Universe’s particle zoo. Garret Lisi’s E8 theory predicts a few new particles, but there’s yet to be any experimental verification of it either.

  • James M. Essig March 16, 2009, 21:05

    Hi Adam;

    Thanks for the info on higgsinium and monopolium.

    It has occurred to me that perhaps solid neutronium might be stabilized using some form of crystaline structure to the neutronium that is not easily produced in nature. Perhaps appropriate arrangement of neutrons by some sort of femtoscale assembly technology could work.

    Another option is that perhaps using rapid integration of neutrons with other unstable particles such as pions or mesons might work wherein the particles as such would influence each other in such a manner that they would form a stable material.

    Quarkonium might be fashioned into microscopic nuggets which would then be bound to each other in a sheet like or 3 -D matrix like pattern.

    I do not have any particular ideas about any such stable arrangments, but if such is possible, it is great material for future soiid state physicists and materials science in general.



  • ljk October 31, 2010, 11:07


    Milky Way Is Square, According To New Galactic Map

    kfc 10/13/2010

    Some of our galaxy’s spiral arms are straight rather than curved, giving the Milky Way a distinctly square look, say astronomers.

    The structure of nearby galaxies such as Andromeda is relatively straightforward to see. But the Milky Way presents an entirely different kind of challenge.

    The problem is that we see the Milky Way edge on, so that nearer stars and clouds are superimposed on more distant ones. Telling these apart is tricky because working out the distance of any astronomical object is hard. And that makes the overall structure a real head scratcher.

    That’s not to say astronomers haven’t got a few tricks up their sleeves to help. The conventional way to work out the structure is a two step process.

    Astronomers first create a model of the galaxy and work out how each part of ought to be moving relative to us.

    Then they scour the Milky Way for clouds of ionised hydrogen. Astronomers can work out the velocity of these clouds by studying the emission spectra and looking for the tell tile shifts in spectral lines that movement causes.

    By matching this measured velocity to the calculated values, astronomers can work out where in the galaxy any cloud should be.

    But this method is notoriously ambiguous, not least because nobody is quite sure how fast the galaxy is rotating, so the model probably has all kinds of errors. Another problem is that stars orbiting the centre of the galaxy at the same distance as us (a large portion of the galaxy, as it turns out) all have a similar velocity. So working out where they are is tricky.

    It’s no surprise, then, that there is little consensus on the exact structure of the Milky Way’s spiral arms.

    Today Jaques Lepine at the University of Sao Paulo in Brazil and a few buddies add a little spice to this mix.

    They’ve studied the spectra produced by clouds of carbon monosulphide, a relatively common component of our galaxy, rather than ionised hydrogen.

    This gave them velocity information for 870 regions of the Milky Way which they’ve used to create a new map of the galaxy with detail never seen before.

    One conclusion is that the Milky Way has an additional spiral arm, not seen in previous surveys of the galaxy. The new arm is about 30,000 light years from the galactic core at a longitude of between 80 and 140 degrees.

    But a bigger surprise is their conclusion that some of the arms in the Milky Way are not curved in the traditional way, but are straight instead. This gives the Milky Way a distinctly squarish look.

    That’s not as outrageous as it sounds. Astronomers know of many galaxies with straight arms, such as M101, the Pinwheel Galaxy, shown above.

    So according to Lepine and co, anybody looking at us from M101 will see a similar kind of squarish structure. Fascinating stuff!

    Ref: arxiv.org/abs/1010.1790: The Spiral Structure Of The Galaxy Revealed By CS Sources And Evidence For The 4:1 Resonance