Tag Archives: Science Fiction

Time Travel Without the Paradoxes

Time Travel Without the Paradoxes

It’s one of the most popular ideas in fiction — travelling back through time to alter the course of history. The idea of travelling through time — more than we do every day that is — isn’t just the remit of science fiction writers though. Many physicists have also considered the plausibility of time travel, especially since Einstein’s theory of special relativity changed our concept of what time actually is. 

Yet, as many science fiction epics warn, such a journey through time could carry with it some heavy consequences. 

Ray Bradbury’s short story ‘A Sound of Thunder’ centres around a group of time travellers who blunder into prehistory, making changes that have horrendous repercussions for their world. In an even more horrific example of a paradox, during an award-winning episode of the animated sci-fi sitcom Futurama, the series’ hapless hero Fry travels back in the past and in the ultimate grandfather paradox, kills his supposed gramps. Then, after ‘encounter’ with his grandmother, Fry realises why he hasn’t faded from reality, he is his own grandfather. 

Many theorists have also considered methods of time travel without the risk of paradox. Techniques that don’t require the rather extreme measure of getting overly friendly with one’s own grandmother Fry. These paradox-escape mechanisms range from aspects of mathematics to interpretations of quantum weirdness. 

ZME’s non-copyright infringing time machine. Any resemblance to existing time travel devices is purely coincidental *cough* (Christopher Braun CC by SA 1.0/ Robert Lea)

Before looking at those paradox escape plans it’s worth examining just how special relativity changed our thinking about time, and why it started theoretical physicists really thinking about time travel. 

Luckily at ZME Science, we have a pleasingly non-copyright infringing time machine to travel back to the past. Let’s step into this strange old phone booth, take a trip to the 80s to pick up Marty and then journey back to 1905, the year Albert Einstein published ‘Zur Elektrodynamik bewegter Körper’ or ‘On the Electrodynamics of Moving Bodies.’ The paper that gave birth to special relativity. 

Don’t worry Marty… You’ll be home before you know it… Probably.

A Trip to 1905: Einstein’s Spacetime is Born

As Marty reads the chronometer and discovers that we have arrived in 1905, he questions why this year is so important? At this point, physics is undergoing a revolution that will give rise to not just a new theory of gravity, but also will reveal the counter-intuitive and somewhat worrisome world of the very small. And a patent clerk in Bern, Switzerland , who will be at the centre of this revolution,  is about to have a very good year. 

The fifth year of the 20th Century will come to be referred to as Albert Einstein’s ‘Annus mirabilis’ — or miracle year — and for good reason. The physicist will publish four papers in 1905, the first describing the photoelectric effect, the second detailing Brownian motion. But, as impressive those achievements are–one will see him awarded the Nobel after all–it’s the third and fourth papers we are interested in. 

1905: young Albert Einstein contenplates the future, unaware he is about to change the way we think about time and space forever. (Original Author Unknown)
1905: young Albert Einstein contemplates the future, unaware he is about to change the way we think about time and space forever. (Original Author Unknown)

In these papers, Einstein will first introduce special relativity and then will describe mass-energy equivalence most famously represented by the reduced equation E=mc². It’s no exaggeration to say that these works will change how we think of reality entirely — especially from a physics standpoint. 

Special relativity takes time — and whereas it had previously been believed to be its own separate entity — unites it with the four known dimensions of space. This creates a single fabric— spacetime. But the changes to the concept of time didn’t end there. Special relativity suggests that time is different depending on how one journeys through it. The faster an object moves the more time ‘dilates’ for that object. 

This idea of time running differently in different reference frames is how relativity gets its name. The most famous example for the time difference is the ‘twin paradox.’

Meet twin sisters Stella and Terra. Stella is about to undertake a mission to a distant star in a craft that is capable of travelling at near the speed of light, leaving her sister, Terra, behind on Earth. 

A spacetime diagram of Terra’s journey through spacetime, against her twin Stella’s. Less ‘proper time’ passes for Stella than Terra meaning when she returnes to Earth Terra has aged more than she has. (Robert Lea)

After travelling away from Earth at near the speed of light, then undertaking a return journey at a similar speed, Stella touches down and exits her craft to be greeter by Terra who has aged more in relation to herself. More time has passed for the ‘static’ Earthbound twin than for her sister who underwent the journey into space.

Thus, one could consider Stella to have travelled forward in time. How else could a pair of twins come to be of considerably different ages? That’s great, but what about moving backwards through time? 

Well, if the faster a particle in a reference frame moves, the ‘slower’ time progresses in that frame, it raises the question, is there a speed at which time stands still? And if so, is there a speed beyond this at which time would move backwards? 

A visualisation of a tachyon. Because a tachyon would always travel faster than light, it would not be possible to see it approaching. After a tachyon has passed nearby, an observer would be able to see two images of it, appearing and departing in opposite directions.
(Wiki CC by SA 3.0)

Tachyons are hypothetical particles that travel faster than the speed of light — roughly considered as the speed at which time would stand still — and thus, would move backwards rather than forwards in time. The existence of tachyons would open up the possibility that our space-bound sister could receive a signal from Terra and send her back a tachyon response. Due to the nature of tachyons, this response could be received by Terra before she sent the initial signal.

Here’s where that becomes dangerous; what if Stella sends a tachyon signal back that says ‘Don’t signal me’? Then the original signal isn’t sent, leading to the question; what is Stella responding to?

Or in an even more extreme example; what if Stella sends a tachyon signal back that is intercepted by herself before she embarks on her journey, and that signal makes her decide not to embark on that journey in the first place? Then she’ll never be in space to send the tachyon signal… but, if that signal isn’t sent then she would have embarked on the journey…

And that’s the nature of the causality violating paradoxes that could arise from even the ability to send a signal back through time. Is there a way out of this paradox?

Maybe…

Interlude. From the Journal of Albert Einstein

27th September 1905

A most astounding thing happened today. A young man in extraordinary attire visited me at the patent office. Introducing himself as ‘Marty’ the youngster proceeded to question me about my paper ‘On the Electrodynamics of Moving Bodies‘– a surprise especially as it was only published yesterday.

In particular, the boy wanted to know about my theory’s implications on time travel! A pure flight of fancy of course… Unless… For another time perhaps.

If this wasn’t already unusual to the extreme, after our talk, I walked Marty to the banks of the Aare river where he told me that his transportation awaited him. I was, of course expecting a boat. I was therefore stunned when the boy stepped into a battered red box, which then simply disappeared.

I would say this was a figment of my overworked imagination, a result of tiredness arising from working the patent office during the day and writing papers at night. That is, were I the only witness!

A young man also saw the box vanish, and his shock must have been more extreme than mine for he stumbled into the river disappearing beneath its surface.

His body has not yet been recovered… I fear the worst.

Present Day: The Self Correcting Universe

As the battered old phone box rematerializes in the present day, Marty is determined to seek out an academic answer to the time travel paradox recounted to him in 1905. 

He pays a visit to the University of Queensland where Bachelor of Advanced Science student Germain Tobar has been investigating the possibility of time travel. Under the supervision of physicist Dr Fabio Costa, Tobar believes that a mathematical ‘out’ from time travel paradoxes may be possible.

“Classical dynamics says if you know the state of a system at a particular time, this can tell us the entire history of the system,” Tobar explains. “For example, if I know the current position and velocity of an object falling under the force of gravity, I can calculate where it will be at any time.

“However, Einstein’s theory of general relativity predicts the existence of time loops or time travel — where an event can be both in the past and future of itself — theoretically turning the study of dynamics on its head.”

Tobar believes that the solution to time travel paradoxes is the fact that the Universe ‘corrects itself’ to remove the causality violation. Events will occur in such a way that paradoxes will be removed.

So, take our twin dilemma. As you recall Stella has sent herself a tachyon message that has persuaded her younger self not to head into space. Tobar’s theory — which he and his supervisor Costa say they arrived at mathematically by squaring the numbers involved in time travel calculations — suggests that one of two things could happen.

Some event would force Stella to head into space, she could accidentally stumble into the capsule perhaps, or receive a better incentive to head out on her journey. Or another event could send out the tachyon signal, perhaps Stella could accidentally receive the signal from her replacement astronomer. 

“No matter what you did, the salient events would just recalibrate around you,” says Tobar. “Try as you might, to create a paradox, the events will always adjust themselves, to avoid any inconsistency.

“The range of mathematical processes we discovered show that time travel with free will is logically possible in our universe without any paradox.”

The Novikov self-consistency principle
The Novikov self-consistency principle (Brightroundircle/ Robert Lea)

Tobar’s solution is similar in many ways to he Novikov self-consistency principle — also known as Niven’s Law of the conservation of history — developed by Russian physicist Igor Dmitriyevich Novikov in the late 1970s. This theory suggested the use of geodesics similar to those used to describe the curvature of space in Einstein’s theory of general relativity to describe the curvature of time. 

These closed time-like curves (CTCs) would prevent the violation of any causally linked events that lie on the same curve. It also suggests that time-travel would only be possible in areas where these CTCs exist, such as in the presence of wormholes as speculated by Kip Thorne and colleagues in the 1988 paper “Wormholes, Time Machines, and the Weak Energy Condition”. The events would cyclical and self-consistent. 

The difference is, whereas Tobar suggests a self-correcting Universe, this idea strongly implies that time-travellers would not be able to change the past, whether this means they are physically prevented or whether they actually lack the ability to chose to do so. In our twin analogy, Stella’s replacement sends out a tachyon signal and travelling along a CTC, it knocks itself off course, meaning Stella receives rather than its intended target.

After listening to Tobar, strolling back to his time machine Marty takes a short cut through the local graveyard. Amongst the gravestones baring unfamiliar dates and names, he notices something worrying–chilling, in fact. There chiselled in ageing stone, his grandfather’s name.

The date of his death reads 27th September 1905. 

Interlude: From the Journal of Albert Einstein

29th September 1905

This morning the Emmenthaler Nachrichten reports that the body of the unfortunate young man who I witnessed fall into the Aare has been recovered. The paper even printed a picture of the young man. 

I had not realised at the time, but the boy bares the most remarkable resemblance to Marty — the unusually dressed youngster who visited with me the very day the boy fell…

Strange I such think of Marty’s attire so frequently, the young man told me his garish armless jacket, flannel shirt and ‘jeans’ were ‘all the rage in the ‘86.’ 

Yet, though I was seven in 1886 and have many vague memories from that year, I certainly do not remember such colourful clothes…

Lost in Time: How Quantum Physics provides an Escape Route From Time Travel Paradoxes

Marty folds the copy of the Emmenthaler Nachrichten up and places it on the floor of the cursed time machine that seems to have condemned him. The local paper has confirmed his worst fears; his trip to the past to visit Einstein doomed his grandfather. 

After confirming his ancestry, he knows he is caught in a paradox. He waits to be wiped from time…

After some time, Marty wonders how it could possibly be that he still lives? Quantum physics, or more specifically one interpretation of it has the answer. A way to escape the (literal) grandfather paradox. 

The double slit experiment (Robert Lea)

The ‘many worlds’ interpretation of quantum mechanics was first suggested by Hugh Everett III in the 1950s as a solution to the problem of wave-function collapse demonstrated in Young’s infamous double-slit experiment.

As the electron is travelling it can be described as a wavefunction with a finite probability of passing through either slit S1 or slit S2. When the electron appears on the screen it isn’t smeared across it as a wave would be. It’s resolved as a particle-like point. We call this the collapse of the wavefunction as wave-like behaviour has disappeared, and it’s a key factor of the so-called Copenhagen interpretation of quantum mechanics.

The question remained, why does the wavefunction collapse? Hugh Everett asked a different question; does the wavefunction collapse at all?

The Many Worlds Interpretation of Quantum Physics (Robert Lea)



Everett imagined a situation in which instead of the wavefunction collapsing it continues to grow exponentially. So much so that eventually the entire universe is encompassed as just one of two possible states. A ‘world’ in which the particle passed through S1, and a world where the particle passed through S2.

Everett also stated the same ‘splitting’ of states would occur for all quantum events, with different outcomes existing in different worlds in a superposition of states. The wavefunction simply looks like it has collapsed to us because we occupy one of these worlds. We are in a superposition of states and are forbidden from seeing the other outcome of the experiment.

Marty realises that when he arrived back in 1905, a worldline split occurred. He is no longer in the world he came from– which he labels World 1. Instead, he has created and occupies a new world. When he travels forward in time to speak to Tobar he travels along the timeline of this world–World 2.

This makes total sense. In the world Marty left, a phone box never appeared on the banks of the Aera on September 27th 1905. This world is intrinsically different than the one he left.

What happens as a result of Marty’s first journey to 1905 according to the Many World’s Interpretation (Robert Lea)

He never existed in this world and in truth he hasn’t actually killed his grandfather. His grandfather exists safe and sound back in 1905 of World 1. If the Many World’s Interpretation of quantum physics is the correct solution to the grandfather paradox, however, then Marty can never return to World 1. It’s intrinsic to this interpretation that superpositioned worlds cannot interact with each other.

With reference to the diagrams above, Marty can only move ‘left and down’ or ‘right’–up is a forbidden direction because it’s his presence at a particular moment that creates the new world. This makes total sense, he has changed history and is in a world in which he appeared in 1905. He can’t change that fact.

The non-interaction rule means no matter what measures he takes, every time he travels back into the past he creates a new state and hops ‘down’ to that state and can then only move forward in time (right) on that line.

Marty’s multiple journey’s to the past create further ‘worlds’ (Robert Lea)

So what happens when Marty travels back to the past in an attempt to rescue his world? He inadvertently creates another state–World 3. This world may resemble World 1 & 2 in almost every conceivable way, but according to the application of the interpretation, it is not the same due to one event–one extra phone box on the banks of the River Aare for each journey back.

As Marty continues to attempt to get back to World 1 — his home — he realises he now lives in a world in which one day in September 1905 on the streets of Bern, hundreds of phone box suddenly appeared on the banks of the Aare, and then simply disappeared.

The sudden appearance of hundreds of red telephone boxes around the banks of the River Aare really started to affect property prices. (Britannica)

He also realises that his predicament answers the question ‘if time travellers exist why do they never appear in our time?’ The truth being, that if a person exists in the world from which these travellers departed they can never ‘get back’ to this primary timeline. 

To someone in World 1, the advent of time travel will just result in the gradual disappearance of daring physicists. That’s the moment it dawns on Marty that as far as World 1 — his world — is concerned, he stepped in a phone box one day and vanished, never to return.

Marty escaped the time travel paradox but doomed himself to wander alternate worlds.

Hey… how do we get our time machine back?

[no_toc]

a Representation of the quantum teleport of information from the surface of Earth to space--a sci-fi's fan's dream, almost. ((IMAGE BY CAS))

Quantum Teleportation: Separating Science Fact from Science Fiction

It goes without saying that many terms and concepts from science, and particularly physics, find themselves transported from the pages of journals and reports to the comic book page or TV screen — albeit intrinsically changed. Quantum teleportation is an interesting example of this process working in reverse. 

A recreation of the transporter room from the Enterprise D as featured in the show Star Trek: The Next Generation. Unfortunately, teleportation as made famous by the Star Trek franchise is impossible, but quantum teleportation is no less fascinating. (Konrad Summers/ CC by SA 2.0)

Though physicist and information theorist Charles Bennet took the term ‘teleportation’ from popular culture, quantum teleportation is radically different than the process used by the crew of the Enterprise to ‘beam down’ to an alien vista. But despite this; that image of Kirk, Spock, Bones, and a crew of hapless red shirts travelling down to the surface of a planet and back — albeit minus several of the red shirts — is so ubiquitous it’s hard for even professional physicists to escape.

“Of course, I think of Star Trek where people and things are being ‘beamed-up’,” Ulf Leonhardt from the Department of Physics of Complex Systems at the Weizmann Institute of Science tells me when I ask him what the word ‘teleportation’ means to him. And Leonhardt is no stranger to quantum teleportation either. He is renowned for his work in quantum optics — one the fields in which quantum teleportation is explored, in fact, its no exaggeration to say ‘he wrote the book on it.’

This ubiquity of the pop-culture interpretation of teleportation is a special kind of hindrance when it comes to the understanding of quantum teleportation as the two concepts are so radically different. 

The first, and most radical difference, you won’t be using quantum teleportation to beam to the surface of an alien world or down to the local shops anytime soon. This isn’t because quantum teleportation isn’t up and running; we’ve had the technology in operation since the mid-nineties. It’s because quantum teleportation has nothing to do with the transport of matter.

Mind over Matter–How Quantum Teleportation Shifts Information

The idea of being able to instantly — or almost instantly — relocate matter from one location to another, was granted the name ‘teleportation’ by a purveyor of the weird Charles Fort in his 1931 book ‘Lo!’. But despite this; the idea existed sometime before this.

Many early examples of teleportation were, unsurprisingly, described as being magical in nature, but with the advent of the industrial revolution, remarkable tales of intrigue and suspense began to move away from supernatural explanations to ones of science–albeit none more credible in nature. The first example of matter being transported instantaneously from one location to another being performed ‘scientifically’ occurred in an 1897 novel.

In Fred T. Jane’s ‘To Venus in Five Seconds: An Account of the Strange Disappearance of Thomas Plummer, Pillmaker,’ the titular hero is transported from a pleasant summer house — albeit filled with strange machinery — to the planet Venus where he encounters warring locals and some other displaced Brits. This is the first recorded example of scientific equipment used to transport a hero to the surface of an alien world in fiction, a function which will, of course, become the most infamous use for teleportation.

An illustration from ‘To Venus in Five Seconds: An Account of the Strange Disappearance of Thomas Plummer, Pillmaker,’ by Fred T Jane. Thanks to a teleportation mishap Plummer is menaced by the rather un-PC inhabitants of Venus (A.D. Innes, 1897, the University of Wisconsin – Madison)

But quantum teleportation doesn’t concern the transport of matter — instantly or otherwise — rather it’s about the transmission of information.

“I think for a layman teleportation means instantaneous transport of matter, but a physicist knows that this is impossible,” Leonhardt explains. “Rather, teleportation is the transport of the information of how to assemble matter to make up an object.

“There is zero chance for the instantaneous transport of matter, but a good chance for the transfer of quantum information of not-too-complex systems. Teleporting people is out of the question, though.”

Ulf Leonhardt, author of ‘Essential Quantum Optics’

So if you’re not going to be taking a trip in a teleporter any time soon. With that said, we can investigate the nature of the information that can be sent via quantum teleportation.

From Here to There: State to State Communication

As quantum teleportation doesn’t concern the transmission of matter, but information, it’s more correct to regard it as a form of communication rather than one of transport like its sci-fi counterpart. But that leaves the question, what is being communicated?

“Quantum teleportation is the transport of a quantum state from one object to another,” Leonhardt says. “The quantum state contains all the possible information about the object.”

Thus, quantum teleportation really means transferring the quantum structure of an object from one place to another without the movement of that physical object. This ‘quantum structure’ refers to qualities that a system or a particle can possess, things like momentum, polarization and spin. 

The quantum mechanical counterpart of classical bits can be encoded with a wealth of information (Nicholas Shan)

This information is encoded in qubits — the quantum-mechanical analogue of classical bits. Whereas a bit can only hold the information ‘true’ or ‘false’ a qubit can be encoded with a deep wealth of information. So, quantum teleportation is a mechanism of moving this qubit without moving the particle with which it is associated. This communication requires the system at the starting point and the system representing the endpoint are entangled. 

“The quantum state cannot be measured for an individual system, because an observation may ruin it,” Leonhardt explains.

“Entanglement between the two ports of the quantum teleportation system is an essential ingredient.”

Ulf Leonhardt, author of ‘Essential Quantum Optics’

The first experiments with quantum teleportation dealt with the transfer of state information between single entangled photons, but it has since been realised in a variety of quantum systems — electrons, ions, atoms and even superconducting circuits. 

What is important to note though, is that quantum teleportation isn’t simply creating two copies of the same quantum system. In fact, that is something expressly forbidden by the rules of quantum physics. 

No Cloning Around!

Christopher Nolan’s magical 2006 thriller The Prestige–based upon a 1995 novel by Christopher Priest– focuses on the intensifying rivalry of magicians Robert Angier (Hugh Jackman) and Alfred Borden (Christian Bale). The feud consumes both men costing the lives of both their loved ones and ultimately themselves. 

During the course of this self-destruction, in an attempt to out-do Borden’s most spectacular illusion, Angier seeks the help of a fictionalised version of Nikola Tesla. Telsa provides Angier with a teleportation device but warns him of the machine’s terrible cost. 

The inimitable David Bowie as Nikola Tesla in Christopher Nolan’s The Prestige. In the film, Tesla warns an illusionist with a grudge the terrible cost of his teleporter but is not heeded. (Warner Bros. Pictures 2006)

That cost is that every time the machine is used, it creates a copy of Angier. A clone. Meaning that the illusionist must murder the ‘original him’ each time the trick is performed. He dispatches ‘himself’ in a tank of water hidden beneath the stage where the teleport pod sits. A fitting way for a magician to go.

But, on the quantum scale, there are specific rules in place to prevent the cloning of a system every time an act of quantum prestidigitation is performed. Quantum teleportation has a strict ‘no cloning’ rule. “The no-cloning theorem states that one cannot create two identical copies from the same individual quantum system,” Leonhardt states.

“The quantum state is too fragile and would be compromised in such a process.”

Ulf Leonhardt, author of ‘Essential Quantum Optics’

The Heisenberg uncertainty principle is just one of the rules of quantum physics that the successful cloning of a system would jeopardise. The most well-known version of the uncertainty principle, for example, states that it is impossible to precisely measure the momentum and the position of a quantum system. The more precisely one knows one, the less precisely one can know the other. 

But, if quantum teleportation allowed a system to be cloned, then an enterprising researcher could measure the position of the original system and simultaneously measure the momentum of the ‘clone’, thus violating this rule.

In fact, all sorts of messiness would ensue with a system that could be cloned, including, eventually, the possible violation of causality itself. 

That means that quantum teleportation really ‘moves’ the quantum state from one location to another, destroying that state in the original port… Possibly by drowning it in a tank. 

Quantum Teleportation… Not Instantaneous, But ASAP

Despite the fact teleportation mishaps often became the focus of episodes of Star Trek, initially, it was little more than a Deux ex Machina that allowed the story to flow without characters being tied up by long shuttle journeys. In order for the narrative of a concise 42-minute episode of TV to flow in a pleasing way, it was necessary for characters to be able to instantly move from place to place.

Unfortunately, quantum teleportation differs from its pop-culture ancestor in this respect too. 

Quantum Teleportation. Words and Graphic Innebrooks research team
Quantum Teleportation. Words and Graphic Innebrooks research team

Though instant transmission of information in quantum physics does exist in the form of the instant change in an entangled system when a measurement is made on one part of that system. That measurement and the adoption of a state that it causes results in the partner system adopting the corresponding state instantly — even if it is at the opposite side of the Universe.

This apparent violation of the universal speed limit of the speed of light in a vacuum troubled Einstein so much he referred to it as ‘spooky action at a distance’ and suggested that it demonstrated quantum physics was an incomplete theory with hidden variables yet to be discovered. But, this aspect of quantum physics has been confirmed by decades of research after the Austrian physicist’s death.

Quantum physics is complete, information does travel between entangled quantum systems or particles instantaneously. Yet despite the fact that quantum teleportation functions on the basis of entanglement — passing a state between two entangled particles — that doesn’t mean that quantum teleportation can transfer information instantly too. 

That’s because quantum teleportation isn’t entirely quantum.

When a qubit is transmitted from a sender to a receiver — we’ll call them Alice and Bob respectively as has become standard when describing quantum communication — it’s necessary to transmit two bits of classical information per qubit from Alice to Bob.

This means a classical communication channel has to be created so that Alice and Bob can communicate the results of their measurements. If this isn’t done, Alice and Bob have no way to reconstruct the initial state and the reconstruction will be random. 

Thus, the downside of this is that it limits the speed of information transfer to the speed of classic communication. A qubit can’t be reconstructed before the classical information is received. Researchers can use lasers and photons as the basis of this classical communication system, so even though there is a speed limit, it’s the fastest speed achievable. This also means it can be achieved through ‘open space’ without the need for fiber optic cables. 

Or course, that means not only can Kirk not instantly return to the Enterprise, but he can’t even get a ‘beam me up’ command sent instantly.  

Quantum Teleportation in Practice

The most likely use of quantum teleportation is in the development of quantum computing, quantum networks, and eventually, a quantum internet. Currently, academic debate over this quantum future is focused on which quantum teleportation system is most reliable. 

This image shows crystals which contain photonic information after quantum teleportation. (© GAP, University of Geneva (UNIGE))
This image shows crystals which contain photonic information after quantum teleportation. (© GAP, University of Geneva (UNIGE))

In 2015 paper published in Nature Photonics scientists from the Freie Universität Berlin and the Universities of Tokyo and Toronto, performed a comprehensive review of theory and experiment surrounding quantum teleportation, concluding that no technology in isolation yet provides the perfect solution, meaning hybridisation is needed if quantum computing is ever to be a reality.

This means that many physicists are currently working on improving the distances over which quantum teleportation can be achieved and the kind of quantum systems that states can be communicated between. 

An example of this is the fascinating work of Nicholas Gisin at the University of Geneva (UNIGE). Gisin and his team have consistently been at the cutting edge of pushing the distances across which quantum teleportation can be achieved. In a 2014 study, Gisin’s UNIGE team not only pushed the distance across which a state could be teleported — over 25 meters through an optical cable — but they also managed to communicate the state from a photon to a solid crystal, showing that states can be passed between radically divergent systems. 

Gisin’s research is constantly being improved upon thus the distance across which a quantum state can be transmitted is stretching. And this includes maybe finally reaching the ‘final frontier.’

Space: Probably Not The Final Frontier for Quantum Teleportation

In July this year, scientists finally made teleportation to space a reality , maybe offering some compensation to disappointed sci-fi fans.

a Representation of the quantum teleport of information from the surface of Earth to space--a sci-fi's fan's dream, almost. ((IMAGE BY CAS))
Representation of the quantum teleport of information from the surface of Earth to space–a sci-fi’s fan’s dream, almost. ((IMAGE BY CAS))


In a series of experiments, described by a paper published in the journal Science an international team of researchers described the communication of a quantum state into space and across a distance of up to 870 miles to the Chinese quantum-enabled satellite Micius. The research represented the first meaningful quantum optical experiment to test the fundamental physics existing between quantum theory and gravity. 

Soon, a new Chinese satellite will orbit Earth a distance up to sixty times greater than that between Micius–launched in 2016– and the planet’s surface. This will allow researchers to push the boundaries of quantum teleportation even further.

(GRAPHIC) C. BICKEL/SCIENCE; (DATA) JIAN-WEI PAN

Ulf Leonhardt believes, however, that our understanding of quantum teleportation and our concept of what is achievable within will eventually become as outmoded as the science described in the escapades of Thomas Plummer.

“I like science fiction as scenarios of social thought experiments, but not so much for technological dreams,” Leonhardt says. “It is amusing to browse through Victorian science fiction. They projected their world of steel and steam into the future, which clearly shows the limits of technological imagination.”

 “Our modern projections will share the same fate.”

Ulf Leonhardt, author of ‘Essential Quantum Optics’

Sources and Further Reading

Leonhardt. L, ‘Essential Quantum Optics,’ Cambridge University Press, [2010].

Bussières. F, Clausen. C, Gisin. N, et al, ‘Quantum teleportation from a telecom-wavelength photon to a solid-state quantum memory,’ Nature Photonics, [2014]

Pirandola. S, Eisert. J, Weedbrook. C, et al, ‘Advances in quantum teleportation,’ Nature Photonics, [2015]

A Journey through Multiverses, Hidden Dimensions, and Many Worlds

A Journey through Multiverses, Hidden Dimensions, and Many Worlds

‘Alternate worlds’ are such a staple of genre television, movies, and fiction and what better challenge to face the hero of a serialised story than to face down an evil doppelganger? How will they overcome a corrupted version of themselves, identical in every way barring their lack of moral fortitude… and sometimes with a beard? 

No platform has embraced the idea of the alternate world more than the superhero comic book. Since the Silver Age of comics during the 1950s and 60s, Marvel and DC have thrilled their readers with tales of alternate worlds and altered heroes and villains. DC’s ‘Infinite Earths’ and ‘Elseworlds’ grew so complicated and convoluted decades after the Flash took a trip to the rather dismissively named ‘Earth-2’ to meet his predecessor, the Golden Age Flash, that in 1986 they had to hold a ‘clearance event’ to get rid of some of this excess baggage… A situation the publisher has had to repeat several times since. 

Most of us won’t be surprised to learn that the idea of ‘alternative universes’ is a facet of science, particularly of physics. But actually, the idea of ‘many worlds’ and that of a ‘multiverse’ of alternative universes arise from very different and disparate concepts.

A Journey through Multiverses, Hidden Dimensions, and Many Worlds
A Journey through Multiverses, Hidden Dimensions, and Many Worlds. (Robert Lea)


The former is an idea born of what is known as the wave-function collapse or measurement problem of quantum mechanics, whilst the latter is a proposition born from cosmology and the question of what existed ‘before’ our Universe began its process of rapid inflation and what exists outside of it now. Likewise, these parallel worlds are often referred to as ‘alternative dimensions’ — another phrase that can be found in the physics textbook, but with a radically different meaning than presented in sci-fi. 

These ideas, whilst suffering from some conflation in the minds of some science fiction writers and fans, could not be more different; one suggests an infinite number of almost identical Universes, whilst another suggests a finite set of Universes existing in their own bubbles. Some of which are anything but similar. And third, refers to hidden ‘directions’ curled up within the familiar 3 -D space that we inhabit. 

So, sit down with your evil twin, and whilst admiring their impressive goatee, take a journey with ZME Science through these hidden dimensions, many worlds and bubble-universes. And where better to begin our journey than at the beginning. 

Meeting the Multiverse

“For a start, how is the existence of the other universes to be tested? To be sure, all cosmologists accept that there are some regions of the universe that lie beyond the reach of our telescopes, but somewhere on the slippery slope between that and the idea that there is an infinite number of universes, credibility reaches a limit.” 

Paul Davies, A Brief History of the Multiverse.

There was a time when the word ‘universe’ referred to everything is existence, but modern cosmology has changed this concept irrevokably. There is now the possibility of being ‘outside’ the Universe. In fact, our Universe maybe just a small part of of a much larger patchwork.

As Paul Davies states above, one of the most dangerous things about the concept of a ‘multiverse’ — a stack of Universes placed alongside each other, is how close it veers towards mysticism. This becomes even more of an issue when considering that even many proponents of this hypothetical idea doubt that it could ever really be experimentally tested.

For others, however; the question is fundamental to science, and the closer we come to a complete picture of our Universe we come to, the more tempting it is to consider others.

Bubble boy: Some iterations of multiverse theory suggest that universes inflate side by side in seperate ‘bubbles’ each possing different physical laws. (Robert Lea)

Fred Adams, an American astrophysicist and Ta-You Wu Collegiate Professor of Physics at the University of Michigan, sees the need for a series of alternative or parallel universes as a necessary extension of the fact that our’s is just too convenient. Why is the Universe ‘fine-tuned’ for life? “The laws of physics are described by a collection of fundamental constants that could, in principle, take on different values,” Adams explains. “Determining the range of constants that allows for a working universe helps quantify the degree to which our Universe is special — or not.”

Adams suggests that our Universe has just the right parameters to support the formation of structure, stars, planets, and even biological systems, but there may be a multitude of ‘empty’ Universes where the conditions were not quite so favourable. And, on the other hand, Adams suggests that there could be universes alongside ours even more favourable to the development of such objects. Universes that are, therefore, even more, favourable to life. That is as much as one could expect to a hypothesised set of over 10⁵⁰⁰ universes. 

But, with even such a large set of ‘alternate Universes’ the chances of finding another ‘you’ is still pretty slim. Especially as the laws of physics in these worlds are likely to be radically different, some even precluding the clustering of fundamental particles and the formation of large scale bodies like stars and planets.

One of the more popular ideas for how a series of Universes could grow and co-exist is the inflationary multiverse theory. Introduced by Paul Steinhardt, Albert Einstein Professor in Science at Princeton University, in 1983 and adapted and advanced by such luminaries in physics as Alan Guth, this theory suggests the idea that inflation doesn’t end with our Universe. It could be eternal with the totality of space broken up into bubbles or patches. Each of these bubbles could possess different physical laws, just as Adams puts forward. 

This idea of eternal inflation does run into the problem that it may well be untestable and thus, unfalsifiable, a key aspect of a scientific theory according to one of history’s most important philosophers of science, Karl Popper. However, this doesn’t deter supporters of the theory, with Alan Guth, in particular arguing that a multiverse is simply a logical extension of the fact we have found our own Universe to be undergoing inflation. 

“It’s hard to build models of inflation that don’t lead to a multiverse. It’s not impossible, so I think there’s still certainly research that needs to be done,” Guth remarked during a news conference in 2014. “But most models of inflation do lead to a multiverse, and evidence for inflation will be pushing us in the direction of taking the idea of a multiverse seriously.”

Another interesting concept for the structure and arrangement of this multiverse is American theoretical physicist, mathematician, and string theorist, Brian Greene’s ‘Brane theory.’ This posits that our Universe and all others sit on a vast membrane located in a higher dimension. Alongside it reside all other universes.

As these universes move around this ‘brane’ they occasionally collide, with each other. These bumps release vast amounts of energy causing ‘big bangs’ to occur and lead to the birth of further universes. 

Greene’s theory is classified as a superstring theory, a hypothetical concept that underlies all physics and unites quantum physics and general relativity — putting forward a theory of quantum gravity. But, superstring theories are in need of an added element, with this need dictating where our trip must head next — in search of hidden dimensions. 

‘I Need Some Space.’ Exploring Hidden Dimensions

“If string theory is right, the microscopic fabric of our universe is a richly intertwined multidimensional labyrinth within which the strings of the universe endlessly twist and vibrate, rhythmically beating out the laws of the cosmos.”

Brian Greene, The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory

The statement that string theory–which suggests that fundamental particles are string-like loops vibrating in space–is in need of ‘hidden dimensions’ may initially summon images of alternate universes occupied by all manner of strange creatures, maybe even an alternative version of you, but, your evil beard wearing doppelganger may find the kind of ‘alternate dimensions’ discussed in string theory a bit of a tight squeeze.

An artist’s concept of hidden dimensions curled-up within the three spatial dimensions of spacetime. (World Science Festival)

One of the exciting things about superstring theories is that, unlike other theories in physics, this class of explanations are able to predict the number of dimensions that the spacetime platform in which they play out possesses. To explain this a little better; general relativity — the geometrical theory of gravity developed by Einstein — plays out in four dimensions, x, y, and z — the spatial dimensions, and time. 

But, this dimensional prediction alludes that string theory requires ten — possibly eleven, maybe even 26 — dimensions to be consistent. This fact leaves a very pressing and pertinent question; where the heck are these other six or seven (or 22!) dimensions? Why do we only perceive the world in four dimensions?

The most simple and straightforward way of answering these questions is to suggest that these added dimensions are ‘curled up’ hidden within the three spatial dimensions of which we are aware. Physicists define this as these dimensions being ‘compacted on an internal manifold’ but for our purposes, it’s just as easy as thinking of them as being very small.

This idea referred to as ‘compactification’ actually predates string theory. It was first put forward by Theodor Kaluza and Oskar Klein in the 1920s, the eponymous theory which introduced compactification was a suggestion to unify gravity and electromagnetism. It’s perhaps ironic it now finds itself employed to unite gravity and quantum mechanics.

The idea of dimensions being hidden due to size isn’t as counter-intuitive and extraordinary as it may initially appear. Think about a cylinder. When held close the object appears 3 dimensional, but take that cylinder to a sufficient distance and it will appear two-dimensional.

Analogously, at low energies and the scale at which we view the Universe, space appears 3-dimensional with us aware of that four dimension — time. At sufficiently high energies, however, these hidden dimensions may become observable. Thus, the search for such hidden dimensions is now focused on particle accelerators such as the Large Hadron Collider (LHC). 

That’s now two disciplines within physics scoured and no evil-doppelgangers to be found. Can quantum physics rescue this much-loved sci-fi trope? 

Many Worlds, Many Yous? 

“I am about to say something that might sound lunatic…” 

Erwin Schrodinger about to discuss in public the idea of many worlds existing simultaneously for the first time, 1952, (possibly apocryphal).

It’s a well-established rule of quantum physics that things are always found in the last place you look*; so it is fitting that the last realm of physics we search for our counterparts is the quantum realm. 

The ‘Many Worlds’ interpretation of quantum physics, first suggested by Hugh Everett III in the mid-1950s, suggests a solution to the problem of wave-function collapse in quantum mechanics. It was decades, however, before physcists began to take it seriously.

Many Worlds, Many Earths, Many yous. (Robert Lea)

Here’s the problem it attempts to answer; whilst conducting the famous double-slit experiment researchers find that electrons propagate as waves yet interact with other systems as particles — appearing as a single spot on a fluorescent detector. Likewise, when given a binary choice between two slits an electron will pass through as a wave unless a detector is placed on the side of the slit. The attempt to detect which slit an electron passed through causes it to ‘choose’ either slit A or slit B.

The Copenhagen interpretation of quantum mechanics suggests this choice arises from the collapse of the wavefunction–wave-like behaviour being destroyed and giving way to particle-like action. The only problem; there is no solid answer to what causes this collapse.

The Many Worlds interpretation suggests another way around the collapse issue; maybe there is no collapse. Everett suggested that instead of collapsing, the wave function grows exponentially, quickly engulfing the researchers, their lab, planet, galaxy, and then their entire Universe.

Therefore, whereas in the Copenhagen interpretation the electron goes through either slit A or slit B, the Many Worlds interpretation says the electron goes through both and when the researchers examine which slit the electron passed through, what they are actually discovering is if they are in a universe in which the electron went through slit A, or if they are in a universe in which it went through slit B. 

So, how does this reflect on the chances of finding your doppelganger? Well, it makes it a certainty. In fact, one of the problems that many physicists have with the the ‘Many Worlds’ interpretation is the fact that it creates the need for infinite worlds. If you consider just the act of turning on a lightbulb, the photons streaming everywhere, there should be a world for every outcome of every interaction. 

And if that hasn’t boggled your mind, consider it in light of the multiverse and hidden dimensions. Every one of these worlds that branches out has its own hidden dimensions curled up within it AND carries with it its own version of the multiverse starting with one difference: slit A not slit B. 

So, how does this reflect on the chances of finding your doppelganger? Well, it makes it a certainty. In fact, one of the problems that many physicists have with the the ‘Many Worlds’ interpretation is the fact that it creates the need for infinite worlds.

If you consider just the act of turning on a lightbulb, the photons streaming everywhere, there should be a world for every outcome of every interaction. 

And rather than starting from the bottom-up as a universe inflating in a bubble would, this new world has a head-start, everything that already exists is there present and correct. The physical laws are identical, large-scale structure exists and so do you.

And if that hasn’t boggled your mind, consider it in light of the multiverse and hidden dimensions. Every one of these worlds that branches out has its own hidden dimensions curled up within it AND carries with it its own version of the multiverse starting with one difference: slit A not slit B. 

Me, is that you?

“Penny, while I subscribe to the many-worlds theory which posits the existence of an infinite number of Sheldons in an infinite number of universes, I assure you in none of them am I dancing.”

Sheldon Cooper, The Big Bang Theory

Even with all this in mind and us determining that if the Many Worlds interpretation of quantum physics is true there almost infinite versions of ‘you’ out there, what are the chances of finding one that is *cues ominous music* PURE EVIL… possibly, with a beard…

He or she is out there… Exactly the same as you, just evil… Plus beard. (Robert Lea)

Just like the electron faced with the ‘choice’ of which slit to pass through, every time you are faced with a choice, no matter how minute, neurons fire in your brain corresponding to the decision you make. Thus, it’s quite possible that there is a version of you out there who always made the wrong choice. In fact, if there are infinite worlds, it’s a certainty. 

The rotter.

The main issue with the Many Worlds interpretation is the idea of its testability. One of the rules of the Many Worlds interpretation is the inability of these worlds to interact. 

Suggestions have been made regards falsifying Many Worlds but they all require placing a macroscopic object into a quantum ‘superposition.’ This is something that is currently beyond experimental limits, though researchers are constantly finding quantum effects in increasingly larger collections of atoms.

Likewise, the idea of the Multiverse is currently untestable. Doing so would probably require viewing the edge of our Universal bubble, and as this is accelerating away from us, possibly faster than light, as the Universe expands that isn’t likely to happen.

At the moment, the most likely of the ideas discussed above to be evidenced is that of hidden dimensions. These could ‘unfurl’ from the 3 spatial dimensions of our visible Universe at high energies. Energy levels that were present in the early universe and could conceivably be reached at the LHC after it’s high luminosity upgrades. 

Just don’t expect to be faced with your bearded, evil, but otherwise exact duplicate from another world any time soon… Probably. 

*There’s probably a universe where this is true, anyway.

Lucian of Samosata’s ship getting swept up to the moon by a tempest.

First SciFi novel ever: A 2nd century AD book about traveling to outer space, meeting aliens and Homer

Lucian of Samsota. Image: Wikimedia Commons

Lucian of Samsota. Image: Wikimedia Commons

Some argue that the first genuine science fiction novel is Mary Shelley’s Frankenstein, where technology bordering necromancy is used to reanimate the dead. But labeling what falls under science fiction can be troublesome. Christopher McKitterick says that in the strict etymological sense, it’s literature about scientific discovery or technological change, but then argues that this definition misses the mark; instead Mckiterrick believes “SF is about how we have changed, how external change affects us, how things we do change the world around us, and how we will continue to change over time.” What about works of fiction written in a time when science wasn’t even considered a distinct field, separate from natural philosophy, or study of religious truth, etc? Depending on how you class what makes science fiction, Lucian of Samosata’s “True Stories” might be the first science fiction novel. The characters venture to distant realms including the moon, the sun, and strange planets and islands. The star protagonist is Lucian himself who happens to stumble upon aliens on the moon and finds himself in the midst of a war between the lunar and sun empires.

Written in 2AD Roman Syria, True Stories parodies Lucian’s contemporary authors who would write various books filled with superstitions and mythology, but labeled them as “true stories.” Here’s a summary via Wikipedia:

“In True Stories, Lucian and a company of adventuring heroes sailing westward through the Pillars of Hercules (the Strait of Gibraltar) in order to explore lands and inhabitants beyond the Ocean, are blown off course by a strong wind, and after 79 days come to an island. This island is home to a river of wine filled with fish and bears, a marker indicating that Heracles and Dionysos have traveled to this point, along with normal footprints and giant footprints.

Lucian of Samosata’s ship getting swept up to the moon by a tempest.

Lucian of Samosata’s ship getting swept up to the moon by a tempest.

Shortly after leaving the island, they are lifted up by a whirlwind and after seven days deposited on the Moon. There they find themselves embroiled in a full-scale war between the king of the Moon and the king of the Sun over colonisation of the Morning Star, involving armies including such exotica as stalk-and-mushroom men, acorn-dogs (“dog-faced men fighting on winged acorns”), and cloud-centaurs. Unusually, the Sun, Moon, stars and planets are portrayed as locales, each with its unique geographic details and inhabitants. The war is finally won by the Sun’s armies clouding the Moon over. Details of the Moon follow; there are no women, and children grow inside the calf of men.

After returning to Earth, the adventurers become trapped in a giant whale; inside the 200-mile-long animal, there live many groups of people whom they rout in war. They also reach a sea of milk, an island of cheese and the isle of the blessed. There Lucian meets the heroes of the Trojan War, other mythical men and animals, and even Homer. They find Herodotus being eternally punished for the “lies” he published in his Histories.

After leaving the Island of the Blessed, they deliver a letter to Calypso given to them by Odysseus explaining that he wishes he had stayed with her so he could have lived eternally. They then discover a chasm in the Ocean, but eventually sail around it, discover a far-off continent and decide to explore it. The book ends rather abruptly with Lucian saying that their adventure there will be the subject of following books.”

So, more fantasy than science fiction? I guess it’s best we leave it to art and literature historians to settle the matters. What’s certain is that this is a hilarious book, and I can’t help being amazed on how imaginative Lucian was. For Lucian himself, however, I suspect the novel was quite a serious matter. No one today (I hope) still believes nymphs, minotaurs or centaurs are real, but in Lucian’s day there were still many people who took these creatures and fables as literally true. True Stories, who’s title is intentionally mocking, alluded to these superstitions, exaggerating accounts even by mythical standards to awake even a glimmer of skepticism in the reader’s mind. Ever witty, Lucian made sure gullible readers won’t fall into thinking his novel is actually a true story with the disclaimer that the accounts described are “things I have neither seen nor experienced nor heard tell of from anybody else; things, what is more, that do not in fact exist and could not ever exist at all. So my readers must not believe a word I say.”

If you’re curious, you can download the whole book, translated into English from Greek, here.

You can read the entire thing here.

scifi_timeline_chart

A timeline chart of SciFi predictions that eventually became true

I pride myself as being a science fiction buff. Asimov, Clark, Wells, Jules Verne – we’ve all come to love these classics. What makes people so fond of science fiction, though? One may argue that it’s these novel’s uncanny ability to dwell the human mind into uncharted areas, all while keeping everything in a realm of feasibility. You’ll find some really crazy ideas, but if you think really hard about it you’ll find that there’s no particular reason why that wouldn’t be possible in the future, however distant it may be. Below you can read a really awesome timeline chart which showcases some of the most famous predictions appearing in SciFi novels which became reality.

Miss anything important from the list? Leave a comment below the post. Credit:   Isabelle Turner  of Printerinks.

scifi_timeline_chart

One in five Brits believe lightsabers are real. Science or Fiction?


While a number of today’s science innovations which most of us take for granted, like airplanes, automobiles, computers or space flight, have been outlined by imaginative science fiction writers before they were possible, it seems there’s a concerning blurred line between what has actually been made possible by science and what is of the realm of science fiction in the minds of some Britons.

One in five Brits, for example, believe that the light sabers like the one any sane child of the last century has witnessed in the epic Star Wars flicks are real – a statistic furnished by Birmingham Science City, revealed in a survey, launched at the start of National Science and Engineering Week (11-20 March). According to the survey:

• More than a fifth of adults believe light sabers exist.
• Almost 25 percent of people believe humans can be teleported.
• Nearly 50 percent of adults believe that memory-erasing technology exists.
• More than 40 percent believe that hover boards exist.
• Almost one-fifth of adults believe they can see gravity.

“We commissioned the survey to see how blurred the lines between science fact and fiction have become,” said Pam Waddell, director of Birmingham Science City.

“While films and TV can be acknowledged as creating confusion, it is also worth highlighting how advanced science has now become, and many things deemed only possible in fiction have now become reality or are nearing creation due to the advancements of science,” she added.

If you’d like to test your knowledge of science fiction and fact, take this very short Birmingham Science City quiz, and then compare your answers to how 3,000 others did.

National Science and Engineering Week runs through March 20 in the U.K.

‘2012’ – most absurd science fiction movie ever

We're all going to die in 2012; because the Aztecs said so...

I’m gonna be honest with you – I didn’t see ‘2012’; honestly, I tried to. I started watching it two times, but it was just too stupid – and not the kind of funny stupid, the kind that just takes all the pleasure of watching (if you have a slight idea about what they’re saying in there). A number of NASA specialists however, decided they have to be more patient than me and watched it from start to end. Their conclusion ? It is the most absurd science fiction movie ever to be made.

The film that grossed more than £490 million at the box office and stared John Cusack, Danny Glover, Thandie Newton and Chiwetel Ejiofor may have been a success from an income point of view, but it had a whole lot of people worrying about absurd things; a whole number of concerned viewers actually called NASA and asked for an explanation. The response was loud and clear: it is a perfect example of bad science on the big screen.

‘The film makers took advantage of public worries about the so-called end of the world as apparently predicted by the Mayans of Central America, whose calendar ends on December 21st, 2012,’ he added.

Researchers from NASA have criticized other movies, such as Armageddon, The 6th Day, Volcano and Chain Reaction for their inaccurate scientific content, but they also said that movies that have had success can be also accurate, citing Gattaca and Blade Runner as examples.

Invisibility: another sci-fi dream come true?

Invisible Man
Photo by Firentzesca

Recently, attempts to make “cloaking technology” possible have reached a great level, with major break throws. Among mentionable achievements, more notable are the work of Oleg Gadomsky, a Russian professor that managed to redirect light around objects and that of the people from the University of Maryland, who reported the successful cloaking of small 2D objects from all light waves.

Now, Scientists have created two new types of materials that can bend light the wrong way, creating the first step toward an invisibility cloaking device. The people behind this major achievement are the researchers at the Nanoscale Science and Engineering Center at the University of California, Berkeley, being the first to manage to cloak 3D materials.

One approach uses a type of fishnet of metal layers to reverse the direction of light, while another uses tiny silver wires, both at the nanoscale level. Both are so-called metamaterials — artificially engineered structures that have properties not seen in nature, such as negative refractive index.

The materials were developed by two separate teams, both under the leadership of Xiang Zhang of the Nanoscale Science and Engineering Center at the University of California, Berkeley with U.S. government funding. One team reported its findings in the journal Science and the other in the journal Nature.

Don’t treat the issue too seriously though. We’re a long way from witnessing the presence of invisible people on the street or the cloaking of whole buildings. Far from it. Here’s what Jason Valentine, one of the members of the projects, had to say.

“We are not actually cloaking anything,” Valentine said in a telephone interview. “I don’t think we have to worry about invisible people walking around any time soon. To be honest, we are just at the beginning of doing anything like that.”Valentine’s team made a material that affects light near the visible spectrum, in a region used in fiber optics.

“In naturally occurring material, the index of refraction, a measure of how light bends in a medium, is positive,” he said.

“When you see a fish in the water, the fish will appear to be in front of the position it really is. Or if you put a stick in the water, the stick seems to bend away from you.”

Fishnet On the left is the conceptual rendered “fishnet” design for the second cloaking material. The actual produced material is seen on the right in an electron microscope picture. It is capable of bending light backwards.

What’s a negative index of refraction, you ask?

“Instead of the fish appearing to be slightly ahead of where it is in the water, it would actually appear to be above the water’s surface,” Valentine said. “It’s kind of weird.”

For a metamaterial to produce negative refraction, it must have a structural array smaller than the wavelength of the electromagnetic radiation being used. Some groups managed it with very thin layers, virtually only one atom thick, but these materials were not practical to work with and absorbed a great deal of the light directed at it.

“What we have done is taken that material and made it much thicker,” Valentine said.

His team, whose work is reported in Nature, used stacked silver and metal dielectric layers stacked on top of each other and then punched through with holes. “We call it a fishnet,” Valentine said.

Immediate applications might be superior optical devices, Valentine said — perhaps a microscope that could see a living virus.

“However, cloaking may be something that this material could be used for in the future,” he said. “You’d have to wrap whatever you wanted to cloak in the material. It would just send light around. By sending light around the object that is to be cloaked, you don’t see it.”