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TVIW: From Wormholes to Orion

People keep asking what I think about Christopher Nolan’s new film ‘Interstellar.’ The answer is that I haven’t seen it yet, but plan to early next week. Some of the attendees of the Tennessee Valley Interstellar Workshop were planning to see the film on the event’s third day, but I couldn’t stick around long enough to join them. I’ve already got Kip Thorne’s The Science of Interstellar queued up, but I don’t want to get into it before actually seeing the film. I’m hoping to get Larry Klaes, our resident film critic, to review Nolan’s work in these pages.

Through the Wormhole

Wormholes are familiar turf to Al Jackson, who spoke at TVIW on the development of our ideas on the subject in science and in fiction. Al’s background in general relativity is strong, and because I usually manage to get him aside for conversation at these events, I get to take advantage of his good humor by asking what must seem like simplistic questions that he always answers with clarity. Even so, I’ve asked both Al and Marc Millis to write up their talks in Oak Ridge, because both of them get into areas of physics that push beyond my skillset.

wormhole1

Al’s opening slide was what he described as a ‘traversable wormhole,’ and indeed it was, a shiny red apple with a wormhole on its face. What we really want to do, of course, is to connect two pieces of spacetime, an idea that has percolated through Einstein’s General Relativity down through Schwarzchild, Wheeler, Morris and Thorne. The science fiction precedents are rich, with a classic appearance in Robert Heinlein’s Starman Jones (1953), the best of his juveniles, in my opinion. Thus our hero Max explains how to get around the universe:

You can’t go faster than light, not in our space. If you do, you burst out of it. Buf it you do it where space is folded back and congruent, you pop right back into our space again but it’s a long way off. How far off depends on how it’s folded. And that depends on the mass in the space, in a complicated fashion that can’t be described in words but can be calculated.

I chuckled when Al showed this slide because the night before we had talked about Heinlein over a beer in the hotel bar and discovered our common admiration for Starman Jones, whose description of ‘astrogators’ — a profession I dearly wanted to achieve when I read this book as a boy — shows how important it is to be precisely where you need to be before you go “poking through anomalies that have been calculated but never tried.” Great read.

If natural wormholes exist, we do have at least one paper on how they might be located, a team effort from John Cramer, Robert Forward, Michael Morris, Matt Visser, Gregory Benford and Geoffrey Landis. As opposed to gravitational lensing, where the image of a distant galaxy has been magnified by the gravitational influence of an intervening galaxy, a wormhole should show a negative mass signature, which means that it defocuses light instead of focusing it.

Al described what an interesting signature this would be to look for. If the wormhole moves between the observer and another star, the light would suddenly defocus, but as it continues to cross in front of the star, a spike of light would occur. So there’s your wormhole detection: Two spikes of light with a dip in the middle, an anomalous and intriguing observation! It’s also one, I’ll hasten to add, that’s never been found. Maybe we can manufacture wormholes? Al described plucking a tiny wormhole from the quantum Planck foam, the math of which implies we’d have to be way up the Kardashev scale to pull off any such feat. For now, about the best we can manage is to keep our eyes open for that astronomical signature, which would at least indicate wormholes actually exist. The paper cited above, by the way, is “Natural Wormholes as Gravitational Lenses,” Physical Review D (March 15, 1995): pp. 3124–27.

wormhole_2

Enter the Space Drive

To dig into wormholes, the new Thorne book would probably be a good starter, though I base this only on reviews, as I haven’t gotten into it yet. Frontiers of Propulsion Science (2009) also offers a look into the previous scholarship on wormhole physics and if you really want to dig deep, there’s Matt Visser’s Lorentzian Wormholes: From Einstein to Hawking (American Institute of Physics, 1996). I wanted to talk wormholes with Marc Millis, who co-edited the Frontiers of Propulsion Science book with Eric Davis, but the tight schedule in Oak Ridge and Marc’s need to return to Ohio forced a delay.

mmillis

In any event, Millis has been working on space drives rather than wormholes, the former being ways of moving a spacecraft without rockets or sails. Is it possible to make something move without expelling any reaction mass (rockets) or in some way beaming momentum to it (lightsails)? We don’t know, but the topic gets us into the subject of inertial frames — frames of reference defined by the fact that the law of inertia holds within them, so that objects observed from this frame will resist changes to their velocity. Juggling balls on a train moving at a constant speed (and absent visual or sound cues), you could not determine whether the train was in motion or parked. The constant-velocity train is considered an inertial frame of reference.

Within the inertial frame, in other words, Newton’s laws of motion hold. An accelerating frame of reference is considered a non-inertial frame because the law of inertia is not maintained in it. If the conductor pulls the emergency brake on the train, you are pushed forward suddenly in this decelerating frame of reference. From the standpoint of the ground (an inertial frame), you aboard the train simply continue with your forward motion when the brake is applied.

We have no good answers on what causes an inertial frame to exist, an area where unsolved physics regarding the coupling of gravitation and inertia to other fundamental forces leave open the possibility that one could be used to manipulate the other. We’re at the early stages of such investigations, asking whether an inertial frame is an intrinsic property of space itself, or whether it somehow involves, as Ernst Mach believed, a relationship with all matter in the universe. That leaves us in the domain of thought experiments, which Millis illustrated in a series of slides that I hope he will discuss further in an article here.

Fusion’s Interstellar Prospects

Rob Swinney, who is the head of Project Icarus, used his time at TVIW to look at a subject that would seem to be far less theoretical than wormholes and space drives, but which still has defeated our best efforts at making it happen. The subject is fusion and how to drive a starship with it. The Daedalus design of the 1970s was based on inertial confinement fusion, using electron beams to ignite fusion in fuel pellets of deuterium and helium-3. Icarus is the ongoing attempt to re-think that early Daedalus work in light of advances in technology since.

But like Daedalus, Icarus will need to use fusion to push the starship to interstellar speeds. Robert Freeland and Andreas Hein, also active players in Icarus, were also in Oak Ridge, and although Andreas was involved with a different topic entirely (see yesterday’s post), Robert was able to update us on the current status of the Icarus work. He illustrated one possibility using Z-pinch methods that can confine a plasma to heat it to fusion conditions.

Three designs are still in play at Icarus, with the Z-pinch version (Freeland coined it ‘Firefly’ because of the intense glow of waste heat that would be generated) relying on the same Z-pinch phenomenon we see in lightning. The trick with Z-pinch is to get the plasma moving fast enough to create a pinch that is free of hydrodynamic instabilities, but Icarus is tracking ongoing work at the University of Washington on the matter. As to fuel, the team has abandoned deuterium/helium-3 in favor of deuterium/deuterium fusion, a choice that must flow from the problem of obtaining the helium-3, which Daedalus assumed would be mined at Jupiter.

Freeland described the Firefly design as having an exhaust velocity of 10,000 kilometers per second, with a 25 year acceleration period to reach cruise speed. The cost: $35 billion a year spread out over 15 years. I noted in Rob Swinney’s talk that the Icarus team is also designing interstellar precursor missions, with the idea of building a roadmap. All told, 35,000 hours of volunteer research are expected to go into this project (I believe Daedalus was 10,000), with the goal of not just reaching another star but decelerating at the target to allow close study.

icarus_pathfinder_vasimr_1l

Image: Artist’s conception of Icarus Pathfinder. Credit: Adrian Mann.

Let me also mention a design from the past that antedates Daedalus, which was begun in 1973. Brent Ziarnick is a major in the US Air Force who described the ARPA-funded work on nuclear pulse propulsion that grew into Orion, with work at General Atomics from 1958 to 1965. Orion was designed around the idea of setting off nuclear charges behind the spacecraft, which would be protected by an ablation shield and a shock absorber system to cushion the blasts.

We’ve discussed Orion often in these pages as a project that might have opened up the outer Solar System, and conceivably produced an interstellar prototype if Freeman Dyson’s 1968 paper on a long-haul Orion driven by fusion charges had been followed up. Ziarnick’s fascinating talk explained how the military had viewed Orion. Think of an enormous ‘battleship’ of a spacecraft that could house a nuclear deterrent in a place that Soviet weaponry couldn’t reach. At least, that was how some saw the Cold War possibilities in the early years of the 1960s.

The military was at this time looking at stretch goals that went way beyond the current state of the art in Project Mercury, and had considered systems like Dyna-Soar, an early spaceplane design. With a variety of manned space ideas in motion and nuclear thermal rocket engines under investigation, a strategic space base that would be invulnerable to a first strike won support all the way up the command chain to Thomas Power at the Strategic Air Command and Curtis LeMay, who was then Chief of Staff of the USAF. Ziarnick followed Orion’s budget fortunes as it ran into opposition from Robert McNamara and ultimately Harold Brown, who worked under McNamara as director of defense research and engineering from 1961 to 1965.

Orion would eventually be derailed by the Atmospheric Test Ban Treaty of 1963, but the idea still has its proponents as a way of pushing huge payloads to deep space. Ziarnick called Orion ‘Starfleet Deferred’ rather than ‘Starflight Denied,’ and noted the possibility of renewed testing of pulse propulsion without nuclear pulse units. The military lesson from Orion:

“The military is not against high tech and will support interstellar research if they can find a defense reason to justify it. We learn from Orion that junior officers can convince senior leaders, that operational commanders like revolutionary tech. Budget hawks distrust revolutionary tech. Interstellar development will be decided by political, international, defense and other concerns.”

Several other novel propulsion ideas, as well as a book signing event, will wrap up my coverage of the Tennessee Valley Interstellar Workshop tomorrow.

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Comments on this entry are closed.

  • Alex Tolley November 20, 2014, 13:17

    Just how big would the wormhole have to be to make the described signature? Is it possible that we need to assume large wormholes in order to see such signatures, and their absence (so far) is due to this assumption?

    My thought is that if wormholes can be made at the micro scale, rather than large physical objects like star ships traversing them, traversal is by means of light carrying information. This would be like a ST transporter, with the original receiver traveling the scenic route.

    If such a network of micro wormholes existed, they might well be invisible. They would also remove the light barrier protection we assume from malevolent aliens. Aliens could be on our doorstep and we wouldn’t know it.

  • ljk November 20, 2014, 15:12

    Just because the USA is squeamish about building and launching Orion for a number of reasons does not mean at least two other spacefaring superpowers would follow suit.

    China and Russia, in addition to having similar ideologies despite their differences and antagonistic behavior in the past, have the ideal setups for building their own Orions: Well established space and nuclear programs, lots of room to test nuclear devices in the form of remote desert regions, a really strong desire to become THE global superpower, and no one to stop them.

    Now Russia may or may not come through on this due to their economic issues and internal strife, though it would not surprise me if Putin were interested in Orion (note I do NOT think this is a good thing, just pointing out the political possibilities).

    China, however, has been growing steadily in their space efforts. Having Orion would not only gain them rather quick access to the rest of the Sol system (assuming this is what they want; they certainly do seem to want Luna at least and maybe Mars), but the very concept of a spaceship run on exploding nuclear bombs could be enough to intimidate other governments without having to use them or even threaten to do so at all.

    Some may say this is not a good way to get us into the Sol system permanently or onward to the stars. The truth is the modern Space Age began in large part due to rockets that were used in the Second World War as weapons against civilian populations but were later turned into devices for peaceful space exploration. No one but a powerful government is going to build anything like Orion or something else that can get us to the stars. The hope is that if Orion does happen – and I am only pointing out the plausibility of the situation, not that I know it will happen if ever – then perhaps they will also become instruments of science and exploration.

  • Enzo November 20, 2014, 15:44

    I find wormholes one of the most underwhelming forms of space travel.
    Even if wormholes exist and can be safely traversed, I’ve never heard of any way you could decide your destination. Since space is essentially 100%
    empty, there is almost certainty to end up nowhere near any stars, let alone
    an interesting one.
    Interesting sure, good for traveling ? I’m not sure.
    Things are even worse if the wormhole need to be harvested from the
    quantum foam and then enlarged : then you would be essentially guaranteed
    of their randomness.

  • RobFlores November 20, 2014, 16:41

    I want to interject one of the hypothesis of the causes of inertia.
    Ernst Mach, believed that objects resist a change of acceleration because
    all future and past objects in the entire universe interact with it. (Mach’s principle,
    Is there an experiment to test if this is right?
    There are some very interesting implications if this were true, which affects wormholes and warp drives and their plausibility and power needs.

  • ljk November 20, 2014, 17:53

    Regarding the randomness of cosmic wormholes, this is why even the wormholes used in Carl Sagan’s science fiction novel Contact were all part of an artificial transit system, where really advanced ETI created them throughout the Universe – and likely created the Universe as well.

    The wormholes of Orion’s Arm also tend to be artificial and therefore controlled in terms of destinations. See their detailed FAQ here:

    http://www.orionsarm.com/xcms.php?r=oa-faq&topic=Wormholes

    Other complications regarding the use of “real” wormholes in our Universe:

    We don’t know where any are. Unlike with Interstellar, one has not been conveniently placed relatively nearby so far as we know. If the nearest one is light years away, we might as well stick with nonflashy sublight propulsion plans.

    As with warp drive, creating a wormhole always seems to involve “exotic” matter, which is often ill-defined or turns out to involve materials and technologies way beyond our current means.

    Once again, let us please focus on what we know and what we have when it comes to interstellar travel, even if our starprobes won’t look or act like the USS Enterprise. I think we will make many important related discoveries along the way as we work towards this goal, rather than wishing for a near-magical method of zipping across the galaxy in seconds.

  • Al Jackson November 20, 2014, 18:07

    For those who have seen Interstellar and want to to see if one can have a traversable wormhole, a neutron star, two planets and a rotating black hole all in the same scenario there is Kip Thorne’s The Science of Interstellar, W. W. Norton & Company; 1 edition (November 7, 2014). Thorne’s account is non technical (which means non mathematical) and everything is indeed explained, even with Throne biting his tongue at times. A more expansive account is in Thorne (January 1, 1995). Black Holes and Time Warps: Einstein’s Outrageous Legacy, W. W. Norton & Company. The best account of General Relativity I know of.

    My favorite science writer , these days, is Dennis Overbye of the NY Times, his comments on Interstellar are here:
    http://www.nytimes.com/2014/11/18/science/interstellar-the-cinema-of-physicists.html

    On a personal note I did not know the film would come out during the TVIW when I submitted the talk early in the year!

    Heinlein’s description of the ‘anomolies’ is quite eerie. A lot of writers had used multiply connected topology in their prose SF going back to the early 1930’s and Asimov had ‘jump drives’ in Foundation as early as 1940. Heinlein , in Starman Jones aced it! I read this when I was about 14 and it stuck , I too consider ‘Jones’ Heinlein’s best so-called juvie tho I have read it more as an adult. While von Braun was responsible for my life in manned space flight Heinlein got me into General Relativity.
    I knew enough math by the late 60 to read and collect John Wheeler’s works on GR, Black Holes (he coined the name) and Wormholes (he coined that name too). My hopes for FTL travel were dashed when I went to study GR in Austin as the University of Texas. My adviser pointed out to me that Wheeler and Fuller has shown that if you go into a Schwarzschild wormhole you die! It had been known for a long time that ordinary black holes would kill you. This was shown for rotating black holes, Kerr BH’s too.
    So I was quite surprised when Morris and Thorne showed a fix-up in the late 80’s , sticking with classical GR and quantum field theory physics did not rule out FTL! Research on this goes on to this day.
    Engineering ,as in ‘bending metal’, a traversable wormhole is ‘indistinguishable from magic’ territory. However they might be made in the Big Bang as the hypothetical ‘primordial black holes’ are, that would bring us back to Heinlein and Starman Jones where ‘anomolies’ are naturally occurring!

  • Dr. Eric W. Davis November 20, 2014, 18:35

    The presence of naturally occurring “exotic matter” (negative mass-energy) in space is predicted to produce a unique signature corresponding to lensing, chromaticity and intensity effects in micro- and macro-lensing events on galactic and extragalactic/cosmological scales [1 – 6]. It has been shown that these effects provide a specific signature that allows for discrimination between ordinary (positive mass-energy) and negative mass-energy lenses via the spectral analysis of astronomical lensing events. Theoretical modeling of negative mass-energy lensing effects has led to intense astronomical searches for naturally occurring traversable wormholes in the universe. Computer model simulations and comparison of their results with recent satellite observations of gamma ray bursts (GRBs) has shown that putative negative mass-energy (i.e., traversable wormhole) lensing events very closely resemble the main features of some GRBs. Other research has found that current observational data suggest that large amounts of naturally occurring “exotic matter” must have existed sometime between the epoch of galaxy formation and the present in order to (properly) quantitatively account for the “age-of-the-oldest-stars-in-the-galactic halo” problem and the cosmological evolution parameters [7].

    Via Ref. 1, when background light rays strike a negative energy lensing region, they are swept out of the central region thus creating an umbra region of zero intensity. At the edges of the umbra the rays accumulate and create a rainbow-like caustic with enhanced light intensity. The lensing of a negative energy region is not analogous to a diverging lens because in certain circumstances it can produce more light enhancement than does the lensing of an equivalent positive mass-energy region. Real background sources in lensing events can have non-uniform brightness distributions on their surfaces and a dependency of their emission with the observing frequency. These complications can result in chromaticity effects, i.e., in spectral changes induced by differential lensing during the event. The quantification of such effects is quite lengthy, somewhat model dependent, and with recent application only to astronomical lensing events. Suffice it to say that future work is necessary to scale down the predicted lensing parameters and characterize their effects for lab experiments in which the negative energy will not be of astronomical magnitude. Present ultrahigh-speed optics and optical cavities, lasers, photonic crystal (and switching) technology, sensitive nano-sensor technology, and other techniques are very likely capable of detecting the very small magnitude lensing effects expected in lab experiments.

    References:
    1. Cramer, J. G., et al., “Natural wormholes as gravitational lenses,” Phys. Rev. D, Vol. 51, 1995, pp. 3117-3120.
    2. Torres, D. F., Anchordoqui, L. A., and Romero, G. E., “Wormholes, Gamma Ray Bursts and the Amount of Negative Mass in the Universe,” Mod. Phys. Lett. A, Vol. 13, 1998, pp. 1575-1581.
    3. Torres, D. F., Romero, G. E., and Anchordoqui, L. A., “Might some gamma ray bursts be an observable signature of natural wormholes?,” Phys. Rev. D, Vol. 58, 1998, 123001.
    4. Anchordoqui, L. A., et al., “In Search for Natural Wormholes,” Mod. Phys. Lett. A, Vol. 14, 1999, pp. 791-797.
    5. Safonova, M., Torres, D. F., and Romero, G. E., “Macrolensing Signatures of Large-Scale Violations of the Weak Energy Condition,” Mod. Phys. Lett. A, Vol. 16, 2001, pp. 153-162.
    6. Eiroa, E., Romero, G. E., and Torres, D. F., “Chromaticity Effects in Microlensing by Wormholes,” Mod. Phys. Lett. A, Vol. 16, 2001, pp. 973-983.
    7. Visser, M., “Energy Conditions in the Epoch of Galaxy Formation,” Science, Vol. 276, 1997, pp. 88-90.

  • Marc Millis November 20, 2014, 19:37

    For those interested in Mach’s Principle, in depth, may I suggest this reference. It is at the graduate level.

    Barbour & Pfister (eds) Mach’s Principle from Newton’s Bucket to Quantum Gravity, Birkhäuser, 1995

  • Gerry November 20, 2014, 20:59

    Another interesting book on the wormhole topic written by a physicist, and which I haven’t seen mentioned before, is “The Physics of Stargates” by Enrico Rodrigo (Eridanus Press, 2010). It gets a favorable rating on Amazon from Jack Sarfatti…

    To the question of wormholes being of limited use for travel because of the inability to control where they lead–some speculations I have encountered envision the process of wormhole creation/expansion yielding two tiny mouths that are initially separated by a microscopic distance. One mouth is then towed or otherwise accelerated toward a distant location at less than light-speed, while the other mouth remains behind. They are inflated to macroscopic size once the distant mouth reaches its destination.

    This method, which is imagined in the Orion’s Arm ‘hard’ sci-fi universe, allows for a sort of “FTL” that avoids some of the causality problems…as long as relativistic time-dilation is taken into account, and the wormhole mouths aren’t ever positioned so as to create a time machine (cf. Roman Ring).

  • NS November 21, 2014, 1:24

    IIRC (can’ find a link) there has already been a search for gamma rays from a starship with anti-matter burning engines, albeit unsuccessful. Would “the intense glow of waste heat that would be generated [by a fusion-drive starship]” be worth looking for as well? Maybe in infrared wavelengths?

  • Al Jackson November 21, 2014, 9:37

    Last notes:
    @Alex Tolley
    As far as I know observability of traversable wormholes piggy backs on astronomy gravitational lensing programs , that is ‘positive’ gravitational masses. Even the various estimates of primordial (positive) mass black holes come from observational astronomy looking for high energy objects to planets and even Kepler data has been used. From papers on observability looks like stellar mass wormholes are the most observable. Primordial black holes range in mass from tiny up to galaxy. However I have not seen, yet, a definitive study of the formation of traversable wormholes in the early universe.
    @Enzo
    For intra-universe traversable wormhole it totally unclear if one can specify a destination even if one could manufacture the thing. However if one were to find ‘naturally occurring’ traversable wormhole it would be real boon to go several many light years to ‘somewhere’! After all if I entered the Lottery to win 100 million dollars and only won 1 million would I throw that ticket away?

  • Marc Millis November 21, 2014, 11:08

    More about inertia and Mach:

    There are between 8-21 versions of Mach’s Principle that have been advanced into mathematical representations. Some of these have been ruled out, but others remain options to explore. So far, there is no firm way to test these that I know about. The versions that exists – at least to the extent that I’ve looked them up – have not been matured to the point where they are applied to predict observables.

    Relevant natural phenomena that might pertain, and which where not known about during the heyday of such pursuits, include: (1) Galactic rotation/gravitation anomalies, (2) Anomalous galactic gravitational lensing [1&2lead to “Dark Matter” hypotheses], (3) Cosmic Microwave Background, (4) Hubble red-shifts, and (5) quantum vacuum energy.

    For example, the hunt for “Dark Matter” began as one hypothesis to explain what is keeping rotating galaxies from flying apart… or to explain the higher gravitational lensing than can be accounted for by the estimates of the mass of the visible matter in those galaxies. I have not yet found any of those Machian versions applied to these phenomena to see if they can be explained by a non-uniform inertial frame due to the distribution of galactic matter, ala Mach. Then again, I’ve not been looking for that for very long.

    Most of these approaches were hot topics around the turn of the last century (1880’s-1920’s) and fell to the back burner with the advent of the geometric (curved) spacetime formalisms. It was presumed that Einstein’s geometric General Relativity would have resolved the questions about the origins of inertial frames, but that was not to be.

    Now, with the mismatch between the existing theories and those observed anomalies, some researchers (like myself) are revisiting those older notions to see if they can lead to a better fit to physical observables.

    That’s the short version of the situation.

    Marc

  • Anthony Mugan November 21, 2014, 16:16

    Fascinating discussion…may I ask a question?

    Would similar optical phenomena as those described by Dr Davis above ( central umbra surrounded by a brighter area) also apply to other hypothetical propulsion models using negative energy ( or a negative refractive index of space time in ‘metric engineering’ models such as those discussed by Puthoff et al?
    Would we expect such optical effects to be preferrentially observed from certain angles of observation rather than others, depending on the space time geometry?

    Apologies if these are stupid questions…

  • Dr. Eric W. Davis November 21, 2014, 18:26

    Anthony Mugan: Most definitely not a stupid question.

    The optical phenomenon that was calculated and modeled for traversable wormholes does not apply to any of the warp drive spacetimes, because their geometries are very different from the traversable wormhole geometries and subsequently so is the way that the negative vacuum energy is deployed to produce the different type (traversable wormhole, warp drive) of spacetime geometries. Via a Popular Science article some few years ago or so, I am aware that some Germans (not named) had done optical calculations for the Alcubierre warp drive and provided a realistic computer simulation of what a warp drive (bubble) would look like to ground observers on Earth as the warp bubble moves across the viewer’s night sky from left to right. The article published three panels showing how that looked at three different positions (and times) in the sky with the Milky Way in the background. It does not look anything like the rainbow caustics and light intensity enhancement associated with traversable wormholes.

    Hal Puthoff is my boss and I know that he, and myself, has not done any optical modeling for his spacetime metric engineering concept, which behaves essentially the same as General Relativity theory to first order. We derived a faster-than-light metric model where the index of refraction of the vacuum is less than one, which produced a hybrid wormhole/warp drive effect. But we never published it because more theoretical work needs to be done to be sure that it didn’t break any rules. Other priorities put that in the backburner.

    I am not aware of whether micro- or macro-lensing effects in spacetime have any dependence on preferential observing angles. I would think that they wouldn’t have such because of the geometrical symmetries that are built into all spacetime metrics, especially the warp drive and wormhole metrics.

  • Al Jackson November 21, 2014, 19:19

    @Anthony Mugan
    If you mean Alcubierre’s warp drive … the problem there was been reducing the amount of negative mass or energy needed to make the the thing work (well this is problem for traversable wormholes too). Some claims have been made that the amount of negative mass can be reduced to very small size.
    In gravitational lens astronomy the more mass the bigger the effect. ‘Natural’ wormholes might have a stellar amount of exotic mass in them making them more observable.
    The small amount of negative mass wanted for the Alcubierre drive makes lensing much more difficult.
    The ‘warp’ drive might have other observable consequences , one them disasterous!
    Namely one may destroy one’s destination on arrival!
    I will try to write about this someday.

  • G. Cecil November 21, 2014, 23:53

    Actually one should not ignore the Fermi Haze around the Galactic Center. It’s spatially extended according to the latest template fits and doesn’t seem to match the distribution expected for an unresolved pulsar population. OK, decaying dark matter or many star-ship gamma-ray wakes, take your pick.

    See Interstellar in IMAX for the visuals but turn off your brain, my astro students (and I) were underwhelmed. Kubrick nailed awe and mystery, apes and monoliths trump drones and unfunny bots.

  • Anthony Mugan November 22, 2014, 9:00

    Thank you, Dr Davis

  • william November 23, 2014, 3:51

    I wanted to add this to the discussion on ‘Interstellar’ since it was related to directly to the idea behind wormholes. I saw the movie just last Thursday night and I consider it to be much better good, then a lot of people have been going on about. It also raised some questions for me that I wanted to ask of Dr. Davis here in this discussion.

    That there was a great deal of the science in this movie, which did in fact be spot on. For example, during a rather dramatic space docking under relatively difficult conditions was exactly portrayed as it would be in a realistic situation. Matthew McConaughey the main character in the movie was portrayed as an exemplary space pilot who performed this docking maneuver.

    However, I can say that based on the imagery showing that no human being could directly perform this maneuver unless he had assistance of a computer. It brought to mind what I heard about the Apollo missions; namely, that NONE of the astronauts who flew a simulator freestyle down to the moon without the assistance of the computer was successful. All pilots in the simulator showed they would crash if left to their own devices.

    The fact in point is that a voyage to the moon (or anywhere else for that matter) would be impossible without a computerized assistance.

    Now for my questions. Someone said earlier in the discussion thread that if a wormhole could be in fact be created, how would you do so, such that your destination would exist after its creation ? Also too, given a wormhole that’s created is there any idea as to what would be its internal lenght ?

    Also, hypothetically, if you were in transit through this wormhole, if one was to go perpendicular to the axis of the tunnel and in effect ‘pierce’ the wall of the wormhole where would you be in doing so ?

  • Brett Bellmore November 23, 2014, 9:44

    I’m reminded of “Dispora”, by Greg Egan. In it, a huge program is pursued to generate an artificial wormhole. In the end it succeeds, and… Due to unanticipated physics, the interior length of the wormhole turns out to always be the same as the exterior length.

    Seriously, while the early SF wormhole stories posited that the universe, while from our perspective flat enough, from an ‘outside’ perspective was like a crumpled sheet of paper, there isn’t any real reason to suppose that wormholes would actually provide shortcuts. In a universe with nearly ‘flat’ space time, they shouldn’t.

  • Alex Tolley November 23, 2014, 18:20

    If the universe is a hologram, does this offer any possibilities. We know that holograms contain all the information distributed across their surfaces, so that 2 projected images are also potentially very close on the 2D holographic material. If we could understand the projection, then does this offer a possible fast traversal of the universe. (Similarly, if the universe is a simulation).

    Is this a possibility, or just a fanciful red herring?

  • Al Jackson November 24, 2014, 9:19

    @William
    Since I was one of the Lunar Module instructors during Apollo I can answer about manual operations during Apollo.
    We had manual procedures for all maneuvers during an Apollo mission, except for Saturn V ascent*, that was an abort, and Lunar descent. I don’t think the crew ever wanted to do a descent with out the primary computer, I think it could have been done but we never practiced it. For Lunar missions the crew did practice Lunar descents from CM un-docking to final landing. The crew did practice manual landing from 500 feet a lot, I am not sure but all the flights were landed manually. If one lost the primary GN&C during descent there was an abort… there was a backup GN&C system aboard the LM. The crew practiced an untold number of aborts (to rendezvous) everywhere within the descent trajectory. The also practiced manual ascent and rendezvous, had too. All crews could do this.
    On CM side , loss of the Primary Guidance and Navigation & Control computer (the PNGCS) would have aborted trans-lunar injection. I know that when they went to non-free-return trajectories there was some practice of LOI using the LM descent engine , as was done on Apollo 13, but don’t know if that was tried manually. It was possible to do mid-course maneuvers manually , and was done on Apollo 13 , with the LM!
    Manual rendezvous was one of the highest priorities and all the crews could do that.
    There is one thing , without the PNGCS and The Deep Space Network doing Apollo in the late 1960’s would have next to impossible.

    Note on the Shuttle.
    Besides ascent were was on crucial maneuver that the crew could never do in the simulator. That was the so called Dutch-roll at entry, this maneuver moved the ‘hot spot’ on the tiles around for no burn through. Wikipedia says the crew could fly entry manually , and it’s possible they could, sure would try, but no one ever succeed in the Shuttle Mission Simulator. (Landing was manual and some astronauts , a few, could do 0,0,0 touch downs.)

    *At one point it it was thought possible to fly the Saturn V ascent manually into orbit. That was an astronaut idea, but proved way too dangerous , never simulated or practiced.

  • ljk November 24, 2014, 9:55

    May we have some clarification here: If our Universe is flat or open then a cosmic wormhole may not make much of a difference if at all? And what is this about the wormhole destroying the destination?

  • Al Jackson November 24, 2014, 11:02

    @ljk
    Remember this is not ‘flat’ in the sense of 3-dimensional space , space-time is four dimensional.
    Our universe is globally flat, on average, over large distance scales. Locally it is very much curved (around planets, stars, galaxies, etc.). Wormholes, were they to exist, would just be another example of local curvature that doesn’t effect the global, average curvature. So a wormhole can connect two places in an average globally flat space-time, in fact that is one of the boundary conditions , that the space-time at the entry and exit of a wormhole be asymptotically flat , that is a long way away from the wormhole.

    The destruction of destination does not apply to wormholes but to the Alcubierre ‘warp drive’.

  • ljk November 24, 2014, 13:22

    ‘Interstellar’ Science: Is Wormhole Travel Possible?

    by Mike Wall, Space.com Senior Writer

    Date: 24 November 2014 Time: 07:00 AM ET

    Sci-fi fans who hope humanity can one day zoom to distant corners of the universe via wormholes, as astronauts do in the recent film “Interstellar,” shouldn’t hold their breath.

    Wormholes are theoretical tunnels through the fabric of space-time that could potentially allow rapid travel between widely separated points — from one galaxy to another, for example, as depicted in Christopher Nolan’s “Interstellar,” which opened in theaters around the world earlier this month.

    While wormholes are possible according to Einstein’s theory of general relativity, such exotic voyages will likely remain in the realm of science fiction, said renowned astrophysicist Kip Thorne of the California Institute of Technology in Pasadena, who served as an adviser and executive producer on “Interstellar.”

    Full article here:

    http://m.space.com/27845-interstellar-movie-wormhole-travel-feasibility.html

    To quote:

    “The jury is not in, so we just don’t know,” Thorne, one of the world’s leading authorities on relativity, black holes and wormholes, told Space.com. “But there are very strong indications that wormholes that a human could travel through are forbidden by the laws of physics. That’s sad, that’s unfortunate, but that’s the direction in which things are pointing.”

    The major barrier has to do with a wormhole’s instability, he said.

    “Wormholes — if you don’t have something threading through them to hold them open — the walls will basically collapse so fast that nothing can go through them,” Thorne said.

    Holding wormholes open would require the insertion of something that anti-gravitates — namely, negative energy. Negative energy has been created in the lab via quantum effects, Thorne said: One region of space borrows energy from another region that didn’t have any to begin with, creating a deficit.

    “So it does happen in physics,” he said. “But we have very strong, but not firm, indications that you can never get enough negative energy that repels and keeps the wormhole’s walls open; you can never get enough to do that.”

    Furthermore, traversable wormholes — if they can exist at all — almost certainly cannot occur naturally, Thorne added. That is, they must be created by an advanced civilization.

  • ljk November 24, 2014, 14:43

    Strange thrust: the unproven science that could propel our children into space

    For many decades, a fantasy among space enthusiasts has been to invent a device that produces a net thrust in one direction, without any need for reaction mass. Of course, a reactionless space drive of this type is impossible. Or is it?

    By Charles Platt

    Published 4:00 am Mon, Nov 24, 2014

    Full article here:

    http://boingboing.net/2014/11/24/the-quest-for-a-reactionless-s.html

  • Geoffrey Hillend November 24, 2014, 16:26

    I don’t think that anything that does not use a space warp can result in a propulsion engine that does not have a reaction mass at least not on the large scale. Anything limited to classical physical must remain trapped in it and that is what I think about the physics in the above article.

  • Geoffrey Hillend November 24, 2014, 16:27

    Excuse me for the double negative. I think that anything that does not use a space warp cannot result in a propulsion system that has no reaction mass.

  • Geoffrey Hillend November 24, 2014, 16:29

    Lets try again. I think that anything that does not use a space warp can result in a propulsion system that does not have a reaction mass.

  • Geoffrey Hillend November 24, 2014, 16:33

    It can’t hurt to make experiments with conventional physics to look for a reactionless mass though.

  • ljk November 24, 2014, 18:10

    Al Jackson said on November 24, 2014 at 11:02:

    “The destruction of destination does not apply to wormholes but to the Alcubierre ‘warp drive’.”

    Sounds like it could make for an even more devastating weapon than slamming a starship into a target at relativistic (but still sublight) speeds.

    Maybe that is another reason we have yet to pick up any FTL starship signatures – though let’s face it, another even bigger answer is that very few SETI efforts have so far been focused on such detections.

  • RobFlores November 24, 2014, 19:07

    So if the Mach effect thrusters from the article above are shown to work
    does this mean that some versions of the Mach Theory of Inertia are
    proven?

    I can see why some are skeptical, comparing it to gravity shielding
    or via absurdist reductionist argument that such an effect would lead to perpetual motion type violations of science laws. But since we
    are dealing with varying electric charges and not matter, there might be
    a loophole.

    I am surprise they cant get funding to try and use a series of CUBE SAT
    to do proof of theory and concept.

  • william November 24, 2014, 19:43

    @Mr. Jackson,

    the information concerning the fact that no manual dissent without the lunar guidance computer was ever successful in a simulation environment comes from a book I have been reading that is very thorough and informative.

  • Alex Tolley November 24, 2014, 19:53

    Interesting that Platt is so supportive of Woodward, yet was famously vehemently disbelieving of the concept of downwind faster than the wind (DWFTTW) which proved spectacularly workable. I haven’t the capability to assess Woodward’s work, but the effect is very small . Even if the effect was very large, it would still need at least the the equivalent energy input as the velocity, otherwise it violate conservation of energy. So we aren’t talking about spacecraft that can travel to the stars will relatively little energy, like “inertialess drives”. OTOH, it might make a good candidate for beamed power within the solar system and beyond.

  • william November 25, 2014, 2:01

    I remember the name of the book now, Mr. Jackson. It’s titled ‘Digital Apollo’ and in the discussion. It turns from test pilots in the 1950s to the various stages in which the Apollo computer and the lander computer was integrated into the requirements of the program. That’s where I got the information that none of the astronauts were successful in bringing down the craft freestyle. Although I do realize that as you said, a great deal of practice was putting into aboard simulations at any point during the dissent maneuvers.

    My point is that in the context of what was discussed earlier, ‘Interstellar’ movie that showed very clearly, I feel the degree to which in the real world computers would be required to do anything it and everything that would be going on. In short, as you stated, there really wasn’t any piloting per se, but rather a degree of human integration into the various steps that the computer would ultimately have to execute.

    As a bit of an aside (but not actually). There’s a very interesting article concerning the Mars one attempt to place people on the planet. I felt that it had as much rubble once to interstellar exploration as it does to its actual planetary aspects. Its link is:

    http://theweek.com/article/index/271973/what-would-it-take-for-humans-to-build-a-settlement-on-mars

  • ljk November 25, 2014, 9:28

    The book on the Apollo Lunar Module computer developed by MIT:

    http://web.mit.edu/digitalapollo/

    A video of a talk on Digital Apollo by the author:

    Published on June 3, 2014

    David A. Mindell, Professor of Aeronautics and Astronautics at MIT, talks about the use of robots in extreme environments like the deep sea, aircraft, and outer space, and how humans operate with and through robots and automated systems. His most recent book, Digital Apollo, explores how human pilots and automated systems worked together to put a man on the moon.

    https://www.youtube.com/watch?v=MG_-1099UM8

    More about the Apollo 11 lunar landing than you ever thought possible:

    http://www.doneyles.com/LM/Tales.html

    Moonjs: An Online Apollo Guidance Computer (AGC) Simulator

    http://svtsim.com/moonjs/agc.html

  • Andrew Palfreyman November 25, 2014, 19:42

    The only worthwhile comment on that boingboing article was from Keith Henson, bless his cotton socks. He nailed it.

  • Alex Tolley November 25, 2014, 22:21

    @Andrew – unless the energy required is at least larger than the energy in the momentum. That could be quite efficient. Beam the energy to the ship and you would have a nice transport system.
    Woodward has a long way to go to show a viable space dive. I’m skeptical of success.

  • Eniac November 25, 2014, 23:34

    Again, everyone seems to be forgetting that the fuel we carry aboard a rocket has two purposes: Reaction mass and source of power. All a “reactionless drive” could do would take away the first purpose. You would still have to find a way to supply it with power, without carrying fuel. Otherwise, the rocket equation applies as is, reactionless drive or not.

    If you try to actually calculate the power needed for accelerating a craft using a reactionless drive you will run into another serious problem: It takes less energy to accelerate from 0 to 1 km/s than it takes to accelerate from 10 to 11 km/s. This apparent paradox can be resolved by taking the reaction mass into account. So what if there is none? Do we throw out the concept of relativity and the inertial reference frame? This is just one way of seeing that the very concept of a reactionless drive is absurd.

  • Brett Bellmore November 26, 2014, 7:06

    Anyway, seriously: Can anyone produce a real reason to suppose that wormholes, if you can generate/find them, will actually provide shortcuts?

    That they would provide shortcuts in SF was dictated by plot necessity. I can’t think of any other basis for expecting it.

  • Al Jackson November 26, 2014, 10:24

    @ljk
    We used to go to MIT , not often, with the flight crews during Apollo.
    MIT did the flight software. They had a ‘simulator’.
    It was a bare room with the hardware interface and a flight computer.
    It had a briar patch of wires and tools , looked like an electronics junk yard!
    However everything worked!
    That’s when I knew those MIT guys knew what they were doing!*

    Remember one time when some program didn’t work, they called some guy who came in wearing a suit and tie but looked like he had sleep in it for two weeks. He came in smoking a cigerette , rumpled hair, went to paper listing of the program (written in assembly language) about 2 ft thick , thumbed through it, said “there’s you problem right there”, left.
    It was amazing.

    *Funny, Feynman has the story about two particle accelerators he saw when a student, the one that looked
    immaculate did not work, the one that looked like a pile of trash did!

  • Eniac November 26, 2014, 12:01

    To elaborate on my second point above, here is part of the comment by Keith Henson (referred to here earlier) on this article:

    Easy thought experiment, put one on a frictionless skateboard in a vacuum. It will accelerate as long as it has power. When it gets to a high enough speed, lower a wheel connected to a generator that makes more power than the drive needs. Tap it and supply the whole world.

    This ingenious thought experiment shows that a reactionless drive is equivalent to a perpetual motion machine. Of course, in practice, you would put the thrusters at the periphery of a rotating wheel so it could easily be used to drive a generator. Forget propulsion, go for the free energy!

    Before you say that the generated power may simply not be enough to power the drive, consider that the generated power can be increased arbitrarily by increasing the thruster velocity, while keeping the thrust, and thus the consumed power, the same.

  • Ron S November 26, 2014, 15:31

    I recall that the fiction of reactionless (or space) drive was originally invented to allow for passenger comfort due to the obvious need for high acceleration in any sort of effective space vehicle. This is a drive that acts on all matter within the ship’s volume, not just on the propellant or engine.

    But magic wands are addictive. Once you’ve made one problem disappear by waving it around it’s difficult to stop. So you then make the energy/propellant problem disappear as well. It is a magic wand after all. Some fiction writers try to make the solution seem credible by declaring that the drive “borrows” energy/momentum from a parallel universe or hyperspace and balances the books by returning it later. Or they make the one-way energy flow somehow beneficial to both sides (our universe and the other).

    Perhaps the best fictional reactionless drive is the Alcubierre warp drive, since it is at least (mostly) mathematically rigorous and does act on everything within a volume. Even so the “propellant” and the technology to manipulate it do not exist, and probably cannot exist.

  • Alex Tolley November 26, 2014, 16:03

    @Al Jackson “went to paper listing of the program (written in assembly language) about 2 ft thick , thumbed through it, said “there’s you problem right there”, left.”

    It seems unlikely that he was looking at a fanfold listing of an assembly language program. More likely it was a dump of a crashed program and he simply found the point where the program failed.

  • Alex Tolley November 26, 2014, 16:12

    @Eniac

    Before you say that the generated power may simply not be enough to power the drive, consider that the generated power can be increased arbitrarily by increasing the thruster velocity, while keeping the thrust, and thus the consumed power, the same.

    That is an assumption you are making, not one that is necessarily true. Right now it is probably fair to say that the drive is consuming a lot more energy than is gained with the thrust. There is no reason to assume a priori that this will be false for an advanced drive. While I am extremely skeptical of this drive effect being real, I don’t think your thought experiment is good enough to dismiss it so simply.

  • Eniac November 26, 2014, 19:06

    @Alex: I think you may not have followed the argument to completion. To get the perpetual motion machine, you need only one assumption: That the power input to a drive producing a constant level of thrust is not dependent on the velocity of the craft. Here is how:

    1) The energy used up by the drive operated at power P during a brief time period delta-t is E-in = P * delta-t
    2) The kinetic energy added to a craft accelerated with force F during delta-t is E-out = F delta-x = F v delta-t.

    Since P and F are constant, you can pick a v in the above equation that satisfies v > P/F, which makes E-out > E-in, the characteristic of perpetual motion.

    Now, for a very inefficient drive this velocity may be impractically large, but this is a thought experiment, after all.

    Actually, if you set v = c, you get exactly the power/thrust relationship of the well known photon drive, so I guess this argument just proves you cannot do any better than that.

  • Eniac November 26, 2014, 20:49

    In other words, the common flashlight is the most efficient reaction-mass-less drive there will ever be.

  • Brett Bellmore November 27, 2014, 13:07

    No a common flashlight isn’t a reaction massless drive. It’s a reaction drive, the reaction mass happens to be in the form of light. E=MC2, light has mass.

  • Alex Tolley November 27, 2014, 13:34

    @Eniac
    Since P = Fv, you cannot just arbitrarily pick a v to create perpetual motion.
    v must always be < c.
    As v increases towards c, mass increases, so P = Fv = mav (F=ma), acceleration will decrease, so that v is constrained.
    As long as the constraints are respected, I do not see why this should invalidate the drive. There is no demand that the drive has to be very energy efficient, just better at attaining high velocity than the rocket equation.
    It may be that the drive cannot accelerate better than a solar sail, it's main benefit being it is small and easily deployable. Power might come from solar collectors, a beam or a nuclear generator.

    So I maintain that one cannot rule this out by this math. There may well be other ways to rule it out, but if so, where are the critiques by physicists, e.g. like those of Sawyer's em drive? I see little of that in the Wikipedia article: http://en.wikipedia.org/wiki/Woodward_effect

    As I have said, I am very skeptical myself, but if Woodward can generate a large, unambiguous effect, then he has something. So far the effect is so small that we cannot rule out some standard physical explanation that he is missing.

  • Rob Henry November 27, 2014, 16:29

    Sorry Alex and Eniac if I’m a little lost here, but didn’t that wacky March’s principle require that some region of spacetime not having enough ‘experience’ to work out its reference frame. Doesn’t that mean we can only use it on a route once (say directly from Alpha Centauri to Sol). So… a way to extract huge amounts of mass-energy from a naive vacuum I can understand – perpetual motion no. As for where to borrow the energy from what is all that dark matter anyway?

  • Eniac November 28, 2014, 19:36

    @Brett: Not reaction-less, but reaction-mass-less. A flashlight does not need a tank of photons, it operates on energy alone, just like those space drives.