'Spacetime Cloak' could conceal events


November 17, 2010

Scientists have determined that it's theoretically  possible to create a spacetime cloak that hides entire events from view

Scientists have determined that it's theoretically possible to create a spacetime cloak that hides entire events from view

Take some light bending metamaterials, incorporate them into flexible fabric and you have yourself an invisibility cloak. That's the theory anyway, and it doesn't stop at hiding objects. Building on the optical invisibility research of Professor Sir John Pendry, researchers from Imperial College, London, have now proposed that similar metamaterials could be used to conceal entire events – get ready for the "Spacetime Cloak".

According to Prof. Martin McCall, leader of the research project, it should be possible to use metamaterials to "open up" light by speeding up the leading half of the light waves while slowing down the trailing half. This would create a “corridor” between the two halves, at which point their source would not be observable – this is the point in spacetime at which energy, information or matter could be secretly moved or manipulated. The leading light waves would then be slowed back down to normal speed, while the trailing waves would be sped up, so they could catch up and seamlessly close the gap. To an observer’s eyes receiving those light waves, it would look like one continuous, uneventful scene.

The Imperial College team use the analogy of a pedestrian crossing a busy road. If the lead cars speed up and the trailing cars slow down, a gap opens between them which the pedestrian could run through. If the trailing cars then catch back up to the lead cars, all that someone watching the traffic head-on would observe is a steady stream of cars, with no pedestrian to be seen.

While it’s questionable whether we’ll be seeing spacetime cloaks anytime particularly soon, the technology could also be used in signal processing and computing. An optical data channel, for instance, could be interrupted so that a calculation could be performed for a parallel channel. That interruption would then be hidden, allowing for continuous processing.

“We're sure that there are many other possibilities opened up by our introduction of the concept of the spacetime cloak,” said McCall, “but as it's still theoretical at this stage we still need to work out the concrete details for our proposed applications.”

The research was published this week in Journal of Optics.

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away. All articles by Ben Coxworth

what a load of rubbish!

Firstly you can\'t speed light up any faster than the speed of light in a vaccuum. You can slow it down less or slow it down more.

By the time it reaches your eyes, presuming your eyes are in air, it will all be going the same speed again.

And there\'s no light that doesn\'t actually go through and be visible.

As for this slowing down the start and speeding up the tail nonsense so they overlap. Even if you could do that, you\'d maybe see the end of the event before the start. But you\'d still see it all.

Don\'t give these people any money please.


What an absolute load of hogwash.

Facebook User

Obviously, you guys don\'t know about meta-materials. Light has already been slowed down within certain materials.. I believe what they\'re talking about is a more sophisticated level of slowing down and speeding up light.

Up to you if you don\'t want to look into the research already done on this subject.

Samuel Cheney

You\'re right.

These highly intelligent people at one of the top 10 universities in the world, couldn\'t possibly know what they\'re talking about.

They\'re bound to have announced something that can be knocked apart by some guy on the internet in seconds.


Phil Clemow

conceal events? the spin doctors have been doing this for years without the help of physics.

Cowfy Kaufman

I guess I missed something that happened in the world of physics since I was in school, but isn\'t the speed of time constant? So how exactly do you \"speed it up\"? For that matter, how do you slow down the speed of light? I recognize that we do not fully understand all the laws of physics and there will doubtless be discoveries that may re-write our understanding of these laws. So, those of you who are saying it can be done, please provide links, references etc so I can read up on it. This is really exciting stuff!

I do agree with Adrien... from my limited understanding of the properties of light, even if you were able to \"speed up\" the leading light rays, wouldn\'t that mean that they would get to your eye before whatever other light rays were ahead of them... and even though this would not necessarily result in you seeing the end of an event before it\'s beginning, it would certainly cause a noticeable distortion because of the potential to receive two off-sync rays of light relating to the same source at exactly the same time.

The only way I see to avoid this would be if the source were not changing (i.e. either emitting or reflecting a constant stream of light at a steady wavelength) and you catch the very initial rays, or if you work only with light rays that you initiate yourself - kind of like if you turn on a flashlight and then manipulate the very first burst of rays...

In any case all this assumes that you have total control over all other potential sources of light -- so you are either working in absolute pitch blackness (in which case yay, congratulations, you already achieved invisibility so why this costly investment to achieve redundancy?) or you are able to manipulate the receiver\'s eye. Either way, real world application doesn\'t seem very feasible to me.

That being said, I am curious to know how this research develops... and if it will really require us to change our understanding of the laws of Physics. Exciting stuff! :)


meta materials all have one amazing property. They don\'t exist.

Do the math. Speed of light in vaccuum is 2.997925 x 10 ^8 m/s

you want to cloak an event that lasts 1ms

you have a theoretical material that has a refractive index of 10. That\'s over twice the refractive index of Sililcon, which is the highest listed on wikipedia.

that means the event you want to cloak needs to be sandwiched in between 2 blocks of material each 299m wide. which you are able to move in and out of the way instantaneously. LHC couldn\'t even move that much mass that quickly.

Santa Claus delivering all the presents on Christmas eve is much more plausible.


We\'ve had materials to \"slow down\" light for\'s called \"glass\" or other refractive materials. They bend light (e.g. spectacles) by slowing down the light, which causes it to bend. The amount of bending (or slowing) is the material\'s refractive index.

Doc Rings, MD Ophthalmology

Matt Rings

Whatever the opinions of those who are against the theory of invisibility cloaks, I am all for it and all because, who knows, great discoveries are often the source of greater developments that were initially totally unrelated! So, come on guys, let\'s support this stuff!!

datche p

Anybody claiming that this isn\'t possible obviously hasn\'t done their research. Read a few articles that AREN\'T from wikipedia, and come back here. Meta-materials are existent, and have been proven to be effective. Also, are you aware that there are many, MANY things moving beyond the speed of light right now? Sure, the speed of light is the constant within the universe, and nothing in the universe can move faster than the speed of light, however, E=MC(squared) does not apply to the universe itself. If the entire universe is expanding at a rate beyond the speed if light, then the objects within the universe are too. There are many things in the universe that we will never see, because they are moving away from us faster than the speed of light. This of course has nothing to do with what is said in the article, and is only a response to those saying that nothing can move faster than the speed of light.

Michael Bennett II

Maybe this is possible, maybe it isn\'t. But there\'s one thing that people are forgetting: this kind of science isn\'t important!

Let\'s say you want to conceal an event that takes like... 10 seconds to happen. So there\'s a 10 second gap in the light rays. After that, the trailing rays must catch up with the leading part, which also takes time. Depending on how much you want to accelerate/decelerate light, closing the gap is bound to take a lot longer than the length of event x, because I don\'t suppose we\'re planning on changing the speed of light by 50% or so. And you don\'t want the end ot the heading part to reach the observer before the start of the trailing part catches up, because then the observer would notice a gap in the light.

Let\'s suppose it\'ll take a minute to close the gap (we\'d still have to adjust light speed considerably). That still means the event will have to take place at least 70 light seconds away from the observer\'s position... That\'s over 20 mln kilometers! At such a distance you wouldn\'t see a passing train if it were on fire!

And the bigger the event you want to conceal, the further away it will NEED to happen. You\'d probably be better off asking the US military or some government agency to conceal the event the old-fashioned way: no witnesses!


Doc Rings and... Michael Christopher Bennett II ...

Point out the material that makes light faster... that makes a light wave faster... even that which makes slowed down light faster. Once you slow it down, how do you speed it up?

We can all come up with \'concepts\' that seem like... oh... \'magic\' (see Arthur C Clarke) ...but I don\'t claim to be able to change universal constants. MCB, we do live -inside- the universe, even if it is expanding. If you\'re going to stipulate that \"many, many\" things are moving faster than light within our universe, be kind enough to provide the link(s) that describes them... or else the rest of us can make our fanciful claims and putdowns of this \'discovery\'... without foundation, or your counterpoint, also. The existence of tachyons has not been proven.

If you just speed up all the light waves associated with an event, it might just fail to register, and then who needs to slow them down again... however, the result might be \'brighter\', and thus noticable. If you just slow down the light waves, I\'d expect the result to be \'dimmer\' or \'interfered\' and also noticable. Slowing and speeding does not -remove- the light of events, it merely interferes them. The event itself would still need to be invisible... not giving off any light.

The traffic analogy is poor... if the observer is within sight of the person crossing traffic, they would still see that person, or notice their change in position at least. If they\'re not within sight of that person... then, duh, they wouldn\'t see them... invisibility! ...and traffic could have come to a complete stop... at, say, a stop light... and a herd could pass in front of them, then the light turns green... and farther away down the freeway, there might be no noticable gap in traffic. Imagine! Stopping light... and starting it up again. If you could work in the dark... oh, but you have a different kind of light for your work, in front of that stopped traffic, you say? Ahhhh... Anti-light. Yes. Mmm. (ring up the guys in white, boys, we got another one.) Ok, maybe you have special glasses for ultra ultra violet work.

If they want to talk about datacomm applications... maybe they should stick to data transmission materials with which we actually work.


So this is basically using the same theory of a Star Trek like \"Warp\" Bubble?

look up Miguel Alcubierre....

Kristopher Rapier

Why would anyone want this!! thats horrible! why would you want to \"conceal events\" unless your doing something horrific! i hope to god that this concept dies away.

Alex Broderick
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