The Physics of Lightsabers
“But the sword of Michael from the armoury of God was given him tempered so, that neither
keen nor solid might resist that edge”
– John Milton, Paradise Lost
Photons are massless particles. Moreover, photons have no repulsive characteristic and beams of light don't cease to propagate 3-feet out from their source. These are the principal reasons why laser beams don't behave like their cinematic-counterparts and usually enough evidence for the discerning movie-goer to realize lightsabers aren't very realistic.
Still, the idea hasn’t been totally neglected by science. Lightsabers have been discussed seriously in a variety of formats, ranging from online articles like this one, to television expos and even a few technical papers.
In fact, one simple way to use a laser as a lightsaber would be mounting a reflector plate 3-feet out from the source of the light. This would allow for the terminating-beams associated with lightsabers. However, if the lasers are as powerful as they’re depicted on film, the telescoping reflector plates would be severed when the two sabers clash.
But the bigger issue that would cripple any lightsaber is cooling. The bulky cooling systems required to prevent industrial cutting-lasers from over heating are also the principle reason we have yet to produce any other type of handheld laser weapon. Additionally, the type of laser(s) we’re discussing would require a high-capacity, yet compact power-supply that simply can’t be produced with current technology.
Running a current through the telescoping shaft could hypothetically resolve the issue of the lightsabers dismantling one another. The lightsabers would be kept intact by a mutual magnetic repulsion generated by the current preventing the laser beams from severing the reflectors. However, there are still ascetic qualities of lasers that might be considered unappealing for a lightsaber.
One in-particular is that the beam would actually be invisible, this is contrary to most people’s assumption that lasers produce visible beams of light. While you’ve probably seen visible laser beams being used in nightclubs or concerts, it is only because the light is being bounced off of air molecules in an atmosphere that is artificially dense. These venues intentionally employ smoke or fog machines for the purpose of creating visually stunning laser-shows, but a laser operating in a normal atmosphere where molecules are more diffuse will still be invisible.[a]
Though these attributes would all be very undesirable in a lightsaber, new research suggests that macroscopic quantum phenomena may subvert the unwieldy awkwardness of traditional lasers. Several years ago a team of researchers out of Harvard University made headlines when they accidentally encountered groups of photons forming ‘molecules’ after being fired through a cloud of laser-cooled rubidium atoms. Time Magazine gleefully quoted Harvard professor Mikhail Lukin stating: “It’s not an in-apt analogy to compare this to lightsabers,” and “its similar to what we see in the movies.”.
While its correct to say these ‘Photonic Molecules’ can cluster together in such a way that a visible beam suitable for a lightsaber could theoretically be formed, photons still carry zero mass and when two beams intersect they still pass unimpeded. What’s more prohibitive is that even if one assumes a 3-foot beam could actually be generated by a device as compact as the hilt of a sword, a very high-amplitude laser would still be required. Therefore this concept consequently faces the same heat-dispersion and power-supply impracticalities as the more rudimentary concept.
Still, none of the above arguments actually rule out lightsabers all-together. In fact, the most well-established lightsaber-hypothesis to-date, isn’t a laser at all.
In his 2008 book Physics of the Impossible (and later in a documentary titled “Can you build a real lightsaber?”) renowned physicist Michio Kaku depicted lightsabers as an extended plasma-torch, a device which, in theory, could actually be constructed and seemed to resolve most of the aforementioned non-sense with lasers. This device is essentially a hilt with a telescoping ceramic pipe where a plasma is heated to 12000°C and vented to containment within an electromagnetic field. All this being powered by yet-to-be-developed high-capacity batteries made possible by future nanotechnology.
A lightsaber like this could actually even be built today with the proper alternative power source. Patents filed in the 1950s for pocket-size radioactive batteries could achieve ratings comparable to the mains and sufficient to supply the plasma-torch. Though the obvious fear of health-hazards and potential of criminals weaponizing nuclear material has prevented the production of such batteries. Regardless, due to Kaku’s expositions, for a brief period lightsabers actually seemed to have a conceptual framework grounded in real science.
Unfortunately, less than a decade after Kaku’s book, physicist Martin Archer authored a discourse regarding the conceptual plasma-saber in a 2016 article published on the website The Conversation. In the article, Archer describes a phenomenon known to plasma physicists as magnetic reconnection. In-short, if two of Kaku’s plasma beams come into contact as they do on film, a deadly exothermic release of plasma would occur:
“When two plasma blades clash it is almost impossible to avoid magnetic reconnection, with the results being an explosive release of the plasma contained in both sabers. This would mean that, if you were in a lightsaber duel, both you and your opponent would have body parts vaporised in a single clash!”
– Martin Archer, 2016
Even neglecting the possibility of lethal ion emissions, plasma-sabers would also suffer ascetic deficiencies. Because a magnetic field is being used to contain the plasma, it would be difficult to build a plasma lightsaber with the homogeneous beam depicted in the movies. Instead of the linear beam emblematic of lightsabers, a plasma-saber would widen at the center as the ionized gas is forced to follow along the magnetic field lines (see Magnetic Mirror, Wikipedia).
For these and a variety of other reasons, it seems unlikely lightsabers or anything similar will ever become more than a quaint intellectual curiosity. But in the spirit of such curiosities, we’ll explore some alternative solutions to the lightsaber-conjecture beginning with a brief look at the connection between the fictional weapon and what might be considered it’s closest science-fiction relative, ‘free-standing holograms’.
In 1946, Dennis Gabor invented the hologram mathematically, he demonstrated that the information of a three-dimensional object can be encoded in the interference pattern of a beam of light, which is more-or-less two-dimensional. After the beam contacts a two-dimensional surface/storage medium, the image can be reconstructed and viewed in three-dimensions from any angle. The advent of lasers made the projection of these patterns much more practical and holographic projections have become relatively common-place.
But the mid-air displays
of Star Wars are
entirely different from actual holography for much the same reason lasers are
different from lightsabers, namely, a laser can’t be projected to an
arbitrary endpoint in three-dimensional space. Adding to the confusion,
the colloquialism ‘hologram’ has also been misapplied to a technique commonly used to display renderings of deceased entertainers, also known as Pepper’s Ghost. (This is an optical illusion that requires the projector to cast the image on a partially-silvered sheet of plastic or glass which gives the impression of the person or object’s presence in the scene.)
The idea of a free-standing hologram is entirely fictitious and the use of the term hologram is a misnomer that has little relevance to Gabor’s original mathematical concept regarding interference patterns. However this hasn’t stopped some researchers from pursuing a real-life equivalent under the more appropriate title of Volumetric Displays.
Recently a group out of Bringham Young University made advances in this emerging field using lasers to construct three-dimensional projections in mid-air. Their technology, called an Optical-Trap Display, is bridging the gap between science fiction ‘holograms’ and physics. The method uses heat from low-wavelength (nearly invisible) 405 nm lasers to quickly accelerate micrometer scale cellulose particles with precision. When the particle is trapped by the heat, colored lasers are projected on it’s surface, illuminating the particle from any angle. When many particles are manipulated in concert, digitally-stored three-dimensional objects can be projected in mid-air and currently achieve a framerate of about 10fps.
So it raises the question, if its relatively easy to generate a 3D light-sculpture in mid-air, why not lightsaber beams too?
Simply put, while these systems can indeed generate three-dimensional luminescent structures, generating a beam capable of burning would be impossible. This is because photophoretic-trapping is highly sensitive to both airflow and heat, in other words, the particles would be dislodged from the laser as soon as the beam moved or exceeded a certain temperature.
Beyond the physical restraints, the overarching problem is the high cost of production for such a niche tool. For example, suppose a company were seeking to develop something similar to a lightsaber, or more specifically, a sword-like energy weapon to double as a thermal cutting-tool. In this case, every functional attribute could be achieved by a high-voltage baton with a standard plasma-torch at the tip. Not only could this device be retractable and compact, but the power requirements could be accomplished by an ordinary lithium-ion battery. A comparatively low-cost alternative that meets every conceivable utility of a lightsaber.
Because the basic concepts behind these plasma weapons don't directly violate the laws of physics, it can be assumed that some incarnation of the lightsaber is in-fact achievable, however not necessarily practical. Even in consideration of alternative arguments such as those above, a real lightsaber would still have few legitimate applications.
Proceed to the Next Post:
What's Wrong with Trump's ‘Space Force’
Comments
Post a Comment