Astronomy Without A Telescope – Warp Drive On Paper

by Steve Nerlich on October 30, 2010

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It's sixteen years since Miguel Alcubierre suggested that faster-than-light travel might be achieved by generating a warp bubble that contracts space-time ahead of the spaceship and expands it behind. Now a metamaterial test laboratory is available to see if this idea really could work. Image sourced from: andersoninstitute.com

The Alcubierre drive is one of the better known warp drive on paper models – where a possible method of warp drive seems to work mathematically as long as you don’t get too hung up on real world physics and some pesky boundary issues.

Recently the Alcubierre drive concept has been tested within mathematically modeled metamaterial – which can provide a rough analogy of space-time. Interestingly, in turns out that under these conditions the Alcubierre drive is unable to break the light barrier – but quite capable of doing 25% of light speed, which is not what you would call slow.

OK, so two conceptual issues to grapple with here. What the heck is an Alcubierre drive – and what the heck is metamaterial?

The Alcubierre drive is a kind of mathematical thought experiment where you imagine your spacecraft has a drive mechanism capable of warping a bubble of space-time such that the component of bubble in front of you contracts bringing points ahead of you closer – while the bubble behind you expands, moving what’s behind you further away.

This warped geometry moves the spacecraft forward, like a surfer on a wave of space-time. Maintaining this warp dynamically and continuously as the ship moves forward could result in faster-than-light velocities from the point of view of an observer outside the bubble – while the ship hardly moves at all relative to the local space-time within the bubble. Indeed throughout the journey the crew experience free fall conditions and are not troubled by G forces.

Standard images used to describe the Alcubierre drive. Left: Want to make the Kessel run in 12 parsecs? No problem - just compress the Kessel run into 12 parsecs. Right: The Alcubierre concept can be thought of as a spaceship surfing on a wave of space-time. Images sourced from daviddarling.info.

Some limitations of the Alcubierre drive model are that although the mathematics can suggest that forward movement of the ship is theoretically possible, how it might start and then later stop at its destination are not clear. The mechanism underlying generation of the bubble also remains to be explained. To warp space-time, you must redistribute mass or energy density in some way. If this involves pushing particles out to the edges of the bubble this risks a situation where particles at the boundary of the bubble would be moving faster than light within the frame of reference of space-time external to the bubble – which would violate a fundamental principle of general relativity.

There are various work-around solutions proposed, involving negative energy, exotic matter and tachyons – although you are well down the rabbit-hole by this stage. Nonetheless, if you can believe six impossible things before breakfast, then why not an Alcubierre drive too.

Now, metamaterials are matrix-like structures with geometric properties that can control and shape electromagnetic waves (as well as acoustic or seismic waves). To date, such materials have not only been theorized, but built – at least with the capacity to manipulate long wavelength radiation. But theoretically, very finely precisioned metamaterials might be able to manipulate optical and shorter wavelengths – creating the potential for invisibility cloaks and spacecraft cloaking devices… at least, theoretically.

Anyhow, metamaterials capable of manipulating most of the electromagnetic spectrum can be mathematically modeled – even if they can’t be built with current technologies. This modeling has been used to create virtual black holes and investigate the likelihood of Hawking radiation – so why not use the same approach to test an Alcubierre warp drive?

It turns out that the material parameters of even so-called ‘perfect’ metamaterial will not allow the Alcubierre drive to break light speed, but will allow it to achieve 25% light speed – being around 75,000 kilometres a second. This gets you to the Alpha Centauri system in about seventeen years, assuming acceleration and deceleration are only small components of the journey.

Whether the limitations imposed by metamaterial in this test are an indication that it cannot adequately emulate the warping of space-time – which the Alcubierre drive needs to break light speed – or whether the Alcubierre drive just can’t do it, remains an open question. What’s surprising and encouraging is that the drive could actually work… a bit.

Further reading: Smolyaninov, I. Metamaterial-based model of the Alcubierre warp drive.

Salacious October 31, 2010 at 3:26 PM

Steve; The useful arithmetic calculation method of time elapsed appears on pg.7 of the linked article above, (I.e. Equ.15 &16).

Torbjorn Larsson OM October 31, 2010 at 3:31 PM

Einstein, the greatest carbon copy of them all, is right, a Lorentzian wormhole is possible.

I don’t think so, for two reasons:

1) There is, besides the quantum physics, a classical paradox problem with GR wormholes that in principle permits instant “time” travel.

2) Besides that we know in general that time travel would break physics severely so that everything would be equally algorithmically easy, same complexity of all systems. But that isn’t what we observe.

Speaking of logically, I will nitpick your joke and point out that technically we aren’t “carbon copies” but “ribosome-made replicas” since the genome isn’t a blueprint for construction but a recipe for development and control. Just my logical 2 $ (from keyboard inflation – swedish keyboard :-D), because the confused and confusing “blueprint” strawman is so often seen.

cactusmush October 31, 2010 at 5:52 PM

So wait… The other day everyone was freaking out because the 1928 cell-phone post “did not belong on this web-site”….

But here, an article which admits to the following – I quote>>> ….”.as long as you don’t get too hung up on real world physics and some pesky boundary issues”…. is perfectly ok.

In other words > lame oft-repeated baseless sci-fi pseudo science accompanied by lame power-point quallity visual = ok
but
>lame time-travel psuedo science based on a misinterpreted film clip = “it does not belong on this website”.

Just putting things in context. Nonsense dressed up as science fantasy = nonsense dressed up as paranormal fantasy.

Personally, I accept speculation posted in articles for the perpose of discourse. It adds value to this excellent website. I am amazed by the fact that otherwise sceptical individuals are aroused by fictional speculative science – if said speculation is accompanied by cheap powerpoint visuals – but not 1928 film footage..

I look forward to your continued efforts to produce a “warp-drive”. Please make sure you translate your scientifically validated specs into Klingon………… For this – I am sure you think – will add legitimacy to your venture.

Duncan Ivry October 31, 2010 at 6:10 PM

Steve Nerlich, thank you for your answer.

“I don’t know that you can ever get prescriptive about what ‘good science’ is.”

This should be a matter of course, but, sigh, okay … There is a rather broad consensus in the community of physicists about what good physical science is. The consensus is practiced in physics as a academic discipline and outside of academics, and you will realize it — more or less –, e.g. when you want to get a job as a physicist, when you want to publish in a physics journal, and when you want to acquire a contract. As a good physicist you use a methodical approach to compare the implications of a theory with conclusions drawn from experiments; these have to be documented well; theories are open for falsification; etc. This should suffice.

Some notes:
- Since Thomas Kuhn’s “The Structure of Scientific Revolutions” we should be aware of the above being “normal” science in contrast to when a paradigmatic shift happens, e.g. from “Newton” to “Einstein”.
- There are people with an education in physics, and there are certain institutions, journals and peer reviewers, who or which, respectively, are not as professional as they should be.

The situation regarding warp space is like this (annoyingly repeating myself):
- Many years of theoretical musings without experiments have gone by.
- The theory in question is *not* implied by Einstein’s gravity theory.
- Einstein’s theory is supported by a great amount of data from lab experiments and from observations outside.
- Warp space theory is *not* supported by experimental data or other observations.
- Rare proposals for experiments testing warp space give no reason why the experiments could or should work.

“… you don’t find that out unless you take a walk down them”

Okay, sometimes you really have to go down more and more alleys. But this is not the case here. As I found in the pertinent, original, scientific publications, the authors go down the same or nearly the same alleys again and again, they “continue chewing …”

“If there’s a problem here, perhaps it’s credulous journalism over-interpreting scientific baby steps.”

I told you, that I have gone through the pertinent articles, including that of Smolyaninov, didn’t I? Crystal clear: original, *scientific* articles of the proponents of those theories themselves, no journalism involved. And I found the deficiencies in *scientific* publications.

Lawrence B. Crowell October 31, 2010 at 6:57 PM

The Alcubierre warp drive is implied by Einstein’s general relativity. It is a solution which is permitted if you relax the Hawking-Penrose conditions on energy. The solution space to the Einstein field equations are not all physically real. A similar thing actually happens with the Maxwell gauge field theory of electromagnetism in classical wave theory. Quantum electrodynamics cleared some of that up.

LC

Torbjorn Larsson OM October 31, 2010 at 11:59 PM

@ Cactusmuch:

[What a stingy handle, btw.]

I am amazed by the fact that otherwise sceptical individuals are aroused by fictional speculative science – if said speculation is accompanied by cheap powerpoint visuals – but not 1928 film footage.

I don’t think anyone was aroused by the speculative science, which is a downer, but by that the concept has a (putative) actual material counterpart, in analogy with “cloak technology” say. And as “cloak technology” far from actual or perhaps even practical use. Then again, those optical tweezers … who knew!?

Any 1928 cell phones from clips are anecdote from pareidolia or “photoshop”, you would have to provide actual evidence. They belong to the class of “UFO sightings” and not science.

@ Duncan Ivry:

a paradigmatic shift happens

That is a funny reference in this discussion, since Kuhn was a philosopher that promoted an untested (I believe) theory.

I’m not conversant with him or his work, but I’ve seen an armchair critique that amounted to something like “a) most scientists detest Kuhn b) he proposed ~ 20 definitions for paradigm, none of them testable; take your pick”. Looked like a fun topic to me. :-D

@ Lawrence B Crowell:

It is a solution which is permitted if you relax the Hawking-Penrose conditions on energy.

In any case GR doesn’t have well and uniquely defined global energy IIRC & AFAIU (having not studied GR, so here’s some more armchair waving from the public stands), so I’m sure you can shoehorn funny and/or unphysical solutions in.

For example, when you want to know the energy of the universe presumably you have to use its Lagrangian and study the dynamic system behavior instead of GR directly. (I have waved that particular reference around so many times I’ll provide it on request this time around.)

Steve Nerlich November 1, 2010 at 1:48 AM

@Duncan Ivry

Thanks again. I sense the frustration and share a bit of it. I have had a go at passing a skeptical eye over the Pioneer anomaly; the universe in a wormhole; and variable speed of light cosmologies in previous AWATs. All these ideas are (probably) fundamentally flawed, but it’s useful working up an argument as to why they are, even if the outcome is just to confirm that current theory is still the best thing around. Anyhow, I’m no scientist – just a hack science journalist.

Lawrence B. Crowell November 1, 2010 at 3:22 AM

Torbjorn Larsson OM: Physical gravity probably does obey the Hawking-Penrose energy condition. General relativity by itself does not. The HP energy condition is, or really are for there are several cases of them, something you have to include. So for somebody who is interested in the foundations of physics and given to mathematical relationships this is interesting to work on. Somehow quantum physics enters into the picture,

The Lagrangian is defined on 1/2 the phase space variables, where it is defined on configuration variables. The Lagrangian defines the action

dS = Ldt = pdq – Hdt,

and the Hamiltionian, which contains energy content, is a Lagrange multiplier that gives the contact manifold of integration. For general relativity the lapse variable N (sort of like a time) and the Hamiltonian obey NH = 0. General relativity is really funny with respect to energy, and in fact there is no general theorem about general relativity which gives conservation of energy. Strange stuff goes on here.

LC

Aqua November 1, 2010 at 8:43 AM

http://science.nasa.gov/media/medialibrary/2010/07/27/bounce_512x288.m1v

Okay.. so this magnetic reconnection or ‘spacequake’ had the energy of a mag. 5.5 earthquake… That’s a lot of energy!

Harvesting that energy might be done by creating the largest induction field one could and attaching via pulsed a magnetic field to portions of that E/M wave?

I like using a sphere of ultra light composite geodesic structure to build a sturdy(!) 10 KM diameter superconducting antenna frame, which would support spiderweb fashion the field generator and vessel – suspended separately. The nuclear powered field generator creates a magnetic bubble around the spacecraft which rides the wave front(s) as they pass to accelerate thereby ‘surfing’ those waves…

Aqua November 1, 2010 at 8:48 AM

Then… to get back… you tack.

Aqua November 1, 2010 at 9:20 AM

The shape of the magnetic field could be controlled by passing current through any of several thousand antennas mounted on the vertices of the spherical structure.

How fast would I get ‘fried’ in a device like this at one of the Lagrangian Points? LOL!

oTay… on the other hand, what would it be like to ‘play around’ in Jupiter or Saturn’s mag. fields for some kicks? If you get where I’m going?

Torbjorn Larsson OM November 1, 2010 at 11:22 AM

Physical gravity probably does obey the Hawking-Penrose energy condition.

Surely that must be a controversial claim!? As mentioned, my knowledge of GR is a null set, so I look at this from an armchair perspective:

AFAIU there are Penrose–Hawking singularity theorems, that rely on extending energy conditions to high energies, i.e. in effect outside the known quantizable effective theory which breaks down there. (The quantized term series diverge.)

Also I note that HPSTs, which aren’t a unique theorem, mostly rely on the different energy conditions so again aren’t unique.

There doesn’t seem to be a well defined sense where physical gravity obeys an energy condition!? The work I linked to [edit in posting: omitted to link to this time around, I see] shows that the universe does so in a standard cosmology setting with gravity and matter, with a resulting energy that corresponds to the average energy density of spacetime and with conservation of energy in the thermodynamical sense.

I assume the strange stuff happens when GR, an effective theory, is applied to unphysical systems where it strictly doesn’t. Somewhat akin to arguing that singularity theorems, that points to unphysical solutions and so are “effective” in some loose sense, describes the actual physics of singularities.

Another source of strange stuff could be that local solutions are non-unique, as opposed to the one they (that paper again) found for cosmology. Then again, maybe their technique hasn’t been used elsewhere as of yet.

Aqua November 1, 2010 at 1:52 PM

Plasma from a fission reaction would be used to power a MHD electric generator. That power would be distributed via woven superconducting carbon nanotubes to thousands of superconducting electromagnets mounted on the surface of the sphere. Energizing combined magnets will be used to create and shape the desired fields.

Aqua November 1, 2010 at 1:54 PM

Anyway.. that’s the best ‘warp drive’/wave rider I could come up with! ~@; )

Lawrence B. Crowell November 2, 2010 at 4:00 AM

The Hawking-Penrose singularity theorems are different from the Hawking-Penrose energy conditions: The strong, dominant and weak energy conditions. For those who know what tensors are the momentum-energy tensor T_{ab} is the source of the curvature of spacetime. The indices are a = {0,1,2,3}, for 0 corresponding to time and 1, 2, 3, corresponding to special directions (denoted with middle index I or j), such as x, y, and z in Cartesian coordinates. Here T_{00} = energy, T_{ii} = p_i = momentum and there can be off diagonal terms as well, which I will not discuss. These energy conditions are

Strong T_{ab}U^aU^b >= 0

Dominant: For U^a a timelike vector T_{ab}U^a is also timelike

Weak: T_{00} >= 0.

The weak condition is the most general, and called weak because it imposes the least restrictions general relativity.

The weak energy condition for a quantum source is the averaged weak energy condition >= 0, is compatible with quantum mechanics or quantum field theory, for it provides a minimal energy level so quantum eigenvalues of energy have a minimum. If this is violated there is no minimal bound on the eigen-spectrum of the quantum field. This causes all sort of havoc with physics.

LC

Lawrence B. Crowell November 2, 2010 at 4:01 AM

I said above special directions, where I meant spatial directions.

LC

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