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## Metamaterials Developed To Bend Sound Waves, Deflect Tsunamis110

cold fjord writes in with this story about some new possible applications for metamaterials. "A new way of assembling things, called metamaterials, may in the not too distant future help to protect a building from earthquakes by bending seismic waves around it. Similarly, tsunami waves could be bent around towns, and sound waves bent around a room to make it soundproof. ... Metamaterials are simply materials that exhibit properties not found in nature, such as the way they absorb or reflect light. The key is in how they're made. By assembling the material — from photonic crystals to wire and foam — at a scale smaller than the length of the wave you're seeking to manipulate, the wave can, in theory, be bent to will. ... Ong and others say ... they could be used to redirect other kinds of waves, including mechanical waves such as sound and ocean waves. French researchers earlier this year, for example, diverted seismic waves around specially placed holes in the ground, reflecting the waves backward. Ong points to the possibility of using what has been learned in reconfiguring the geometry of materials to divert tsunamis from strategic buildings.'"
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## Metamaterials Developed To Bend Sound Waves, Deflect Tsunamis

• #### Tsunami "Bending" can't work (Score:2, Insightful)

You are talking about redirecting amounts of energy in a wall of water than may be 10-20 feet high or more, yet it comes in as a solid wave and the elevation stays at that height causing water to move inland extremely fast for a long time.

It would be easy to calculate what amount of energy that would be in a width of a town: E = .5 * mass x v^2. You are talking about amounts of energy that would dwarf anything a major multi-unit power plant could produce.

• #### Re:Tsunami "Bending" can't work (Score:5, Informative)

on Friday December 27, 2013 @01:59AM (#45794119)

You are talking about redirecting amounts of energy in a wall of water than may be 10-20 feet high or more, yet it comes in as a solid wave and the elevation stays at that height causing water to move inland extremely fast for a long time.

It would be easy to calculate what amount of energy that would be in a width of a town: E = .5 * mass x v^2. You are talking about amounts of energy that would dwarf anything a major multi-unit power plant could produce.

Some scientists working with this sort of approach seem to think there is some potential for handling seismic energy.

How to Repel an Earthquake [sciencemag.org]

"It's very cool stuff," says Ulf Leonhardt, a theoretical physicist at the University of St. Andrews in the United Kingdom who was not involved with the study. "It's a step toward manipulating seismic waves and done in a genius way." ...

The scientists created their jumbo-sized metamaterial in August 2012 by drilling holes in a thick bed of silt and clay near the city of Grenoble in the French Alps. The cylindrical holes stretched down about 5 meters into the earth, but were also skinny, only 32 centimeters wide. They were arranged in a rectangular grid of three rows of 10 holes each. The holes changed the density and stiffness of the earth and, thus, the speed and direction of vibrations rippling through the ground, forming a seismic metamaterial. The scientists then shook the earth on one side of the grid using a vibrating soil-compacting machine that they had placed underground. That machine created 50 seismic surface waves per second with a wavelength of 1.56 meters—about the same as the distance between the holes, though shorter than typical wavelengths from earthquakes.

Sensors placed throughout the site showed that the waves couldn't get past the grid of holes, bouncing off of it instead, the researchers report in a paper posted on the arXiv online preprint server. The waves just barely got by the second row of holes and couldn't even touch the third row, leaving the ground on the other side unshaken.

• #### Re: (Score:2)

Are you aware that the tsunami which generated the 2011 Japan tsunami occurred out in the middle of the ocean?

Its not the seismic activity you need to stop, its the wall of water caused by said seismic activity.

• #### Re: (Score:2)

Yes, I'm aware. But the parent post was commenting on the amount of energy required. Wouldn't the energy of the tsunami be comparable to the event that created it? If seismic energy is manageable despite the magnitude then I would expect that the energy of a tsunami would be manageable, but the form would obviously be different. It may be that the form renders it infeasible, just not the magnitude.

• #### Re:Tsunami "Bending" can't work (Score:4, Funny)

on Friday December 27, 2013 @02:53AM (#45794265)

Because, as we all know, if you deal with a really large amount of energy, physics can't possibly work.

• #### Re: (Score:3)

Can you walk through walls? Become invisible? Bend tsunamis?
Hang on for a shocking discovery that will rock your world!
One little trick that can hack physics!

• #### Re: (Score:2)

Can you walk through walls

Yes - damn those termites!

Become invisible

Yes - dark in here isn't it?

Bend tsunamis

No, but that city it washed over diverted the flow. Maybe doing something like the physical features that diverted the flow can be exploited to divert another one so it could do less damage. If only there was an article about such a thing.

Science! It works bitches!

They said antigravity would never work, but then they had not yet met Elisha Otis's Elevator!
In other words if you haven't worked it

• #### Re: (Score:2)

"Can you walk through walls?" Yep. Doors exist. "Become invisible?" Turn off the light. "Bend tsunamis?" Build a sandbar.

"Hang on for a shocking discovery that will rock your world!" Nope. A rolling stone gathers no moss.

"One little trick that can hack physics!" Physicists Hate This One Weird Trick! [nasa.gov]

• #### Re: (Score:3, Informative)

Yeah, but the solution to the problem in high energy physics is to make sure the high energy things don't touch anything important.

So, in this case, all we need to do is to levitate the ocean.

And you do realise that the mass of these pulses that LHC is trying to bend is only a tenth of a millionth of a gram? Tsunamis weigh quite a bit more than that.

But jesting aside, the article does look mostly bullshit, as it's highly inappropriate to model tsunamis as waves and solutions as working upon waves. They're s
• #### Re: (Score:1)

by Anonymous Coward

But jesting aside, the article does look mostly bullshit, as it's highly inappropriate to model tsunamis as waves and solutions as working upon waves. They're so low frequency they're effectively DC. That's why in the term "tidal wave" is inappropriate - the "tidal" part is fine - in fact, it's almost perfect - it's the "wave" part that's misleading.

No, this is BS right here. Considering for some time there have been well developed models of tsunamis used to predict potential dangers and setup tsunami warnings, treating the tsunamis as waves. Their wavelength may be quite long, and knowing what a soliton is might help, but they are still waves.

And the reason researchers think the term tidal wave is inappropriate has everything to do with the word "tidal" which is the opposite of perfect, since tsunamis have little to nothing to do with tides. If yo

• #### Re: (Score:2)

You're confusing "actually tides" and "like tides". The closest thing to a tsunami is a tide. Tsunamis are about as tidal as you can get without actually being tides.

Yes, you can model the uninterrupted propagation of tsunamis as waves. Yes, you can model the diffraction around island-sided opjects as waves. Yes, you can model the propagation of tsunamis down channels as waves, solitons as you say. But no, humans cannot realisitically use meta-material approaches to modifying tsunamis in order to protect ag
• #### Tsunami "Bending" happens (Score:3)

Coastlines do it. Features on the ground do it. Stop thinking in terms of energy versus energy because that's not what is being suggested. It's not about matadors headbutting bulls but instead getting them to move in a path at an angle that won't hit them.
• #### Re: (Score:2)

The greatest amount of damage from tsunamis happens when *other things* bend the tsunami. Anything which diverts the energy away from one thing diverts it towards another thing. Heaven help you if you've got two things diverting the energy towards you, such as sides of a bay, as then you're more likely to have an e^-kd rather than k.d^-2 reduction in energy (an extreme - compare losses in fibre optics to the inverse square law).
• #### Re: (Score:2)

Sure, but if everyone could divert the Tsunamis back into the open ocean, they'd dissipate eventually.

A bigger problem is that their large-scale test involved changing the composition of an entire area between source and sensor. So are we supposed to build umpty-zillion pillars in the ocean or something? Probably infeasible.

• #### Energy level doesn't matter in this case. (Score:2)

You are talking about redirecting amounts of energy in a wall of water than may be 10-20 feet high or more, yet it comes in as a solid wave and the elevation stays at that height causing water to move inland extremely fast for a long time.

It would be easy to calculate what amount of energy that would be in a width of a town: ...

Yes, you are. So what? That energy is spread out over a very wide area. You're talking about building a "lens" over a similarly wide area - out where the "tsunami" is a gentle (th

• #### Re: (Score:2)

Dude, what dont you understand? Metamaterials can bends soundwaves, tsunamis are just big waves, therefore metamaterials can bend tsunamis.

SCIENCE!

• #### Re: (Score:2)

I can redirect the energy of a 4000 pound vehicle doing 75MPH with only my little finger. It's just a matter of where and how the force is applied. Remember, the objective isn't to counter the energy, it's to redirect it a bit.

• #### divert tsunamis from strategic buildings (Score:2, Insightful)

by Anonymous Coward

and towards some poor fishing village full of primitive natives nobody cares about..

• #### Build a great harbor without a seawall! (Score:3)

divert tsunamis from strategic buildings and towards some poor fishing village full of primitive natives nobody cares about.

How about building a great harbor and calm beach without a seawall, bracketed by two regions where the surfing is GREAT!

• #### Re: (Score:2)

Who is that even supposed to be a criticism of, and why is it insightful?

• #### Or send it back out to sea. (Score:2)

divert tsunamis from strategic buildings and towards some poor fishing village full of primitive natives nobody cares about.

You can also use this to send the wave back out to sea - and defocus it while you're at it, so it's just a slightly higher wave than usual when it finally gets to another piece of land.

This is what happens to it when it hits shore: Some of it bounces and is diffused - or possibly focussed. By doing this intelligently we can make it SMALLER when it hits the "secon

• #### Re: (Score:2)

Yup, we need to focus all tsunamis on Somalia. That will stop piracy and put an end to starvation in Somalia - since there won't be anybody there after a while.
• #### Re: (Score:3)

Or we could focus tsunamis - and all other waves - to a reservoir and let it drain back to sea through turbines. Or we could build concentrated tidal power plants. Or whatever.

• #### Re: (Score:2)

Since the focusing is frequency dependent, I don't think you could use the same structure to focus both tsunami and ordinary waves. Still, you may have the inspiration for a new form of wave driven generator.

Tsunami's are infrequent enough that aiming them at a reservoir to power a generator would be rather inefficient. I doubt it could be cost effective. And since it's salt water, most other uses of the reservoir would be impratctical. It would be nice if you could just bend it 90 degrees, but I think

• #### Re: (Score:2)

No no no that would never happen. I'm sure the plan would be to redirect it to circle on itself so it gets dizzy and falls down ... or form a giant vortex that sucks the entire earth into another dimension.

• #### Deflector shields (Score:4, Interesting)

on Friday December 27, 2013 @12:58AM (#45793867)

I don't think anyone ever expected that something akin to actual deflector shields for use on earth might be practical anytime soon, that they would always be the stuff of science fiction. At least this offers the possibility of actually making something like them with matter and not a theoretical energy shield requiring massive nuclear reactors.

Very interesting stuff - Metamaterials [popsci.com]

• #### Scale smaller than the wavelength? (Score:3)

on Friday December 27, 2013 @01:01AM (#45793879)

Yes. The size of the structures may be smaller then the wavelength of interest. But they must be assembled in an array of a size on the order of the wavefront you want to divert. So you can redirect a seismic wave away from a town with an array of holes. Each hole might be of manageable size. But the array would be on the order of the same size as the town. That's a lot of holes and a lot of property you are going to be perforating.

• #### Re: (Score:3)

I saw these items that you might find interesting.

How to Repel an Earthquake [sciencemag.org]
How to prevent earthquake damage: make buildings invisible [phys.org]
Seismic Metamaterials Could Cloak Dams and Power Stations [technologyreview.com]

• #### So put it under a freeway! (Score:4, Interesting)

on Friday December 27, 2013 @04:28AM (#45794557) Journal

Each hole might be of manageable size. But the array would be on the order of the same size as the town. That's a lot of holes and a lot of property you are going to be perforating.

It must be on the scale of the town IN ONE DIMENSION. Linear-square law: The bigger the area you're protecting, the lower the percentage of the area you need to perforate.

So you need to perforate a strip around the town to do this? Do it while you're ALREADY perforating such a strip. Like when you're building (or revamping) the next beltway-freeway around the city of interest, or approving a rezoning for the construction of a new outer subdivision.

• #### Re: (Score:1)

I'm not sure whether I understand the principles correctly, but if you can conjure up something that deflects seismic waves, you wouldn't need to drill holes under the entire city. All you'd need is a ring of deflectors around the city large enough to deflect a decent earthquake. The city would then only be unprotected in the unlikely event the epicenter is directly beneath the city. Even if that is, for some reason, impossible, underground work is required in most cities on a regular basis anyway. One cou
• #### Re: (Score:2)

It's a bit trickier than that. You need a precisely spaced grid of materials with a different density. Holes aren't necessary. This kind of thing up above grould has been done with grids of posts. But if you're using holes, you can't run a sewer in the same area. It ruins the "crystal" structure.

• #### Better idea (Score:1)

by Anonymous Coward

Deflect tsunamis away from towns with atomic blasts.

• #### Even Better idea (Score:3)

Deflect towns away from tsunamis with atomic blasts.

• #### "Developed" = "Imagined" (Score:2)

Metamaterials Developed To Bend Sound Waves, Deflect Tsunamis

Is it really "developed" when it's not actually been made yet? It's a bit like saying "Nuclear bombs developed to send man into space" when talking about Project Orion. [wikipedia.org]

I don't think much of their "related" articles either:

ASTEROID MINERS PREPARING FOR GOLD RUSH IN SPACE
SATELLITE IMAGE SUGGESTS NORTH KOREA HAS RESTARTED NUCLEAR REACTOR
DEPRESSION AFFECTS MEN AND WOMEN EQUALLY: STUDY
PRESIDENT OBAMA TO NAME FURMAN AS CHIEF ECONOMIST
ASPIRIN TIED TO LOWER RISK OF SKIN CANCER

• #### Re: (Score:2)

Metamaterials Developed To Bend Sound Waves, Deflect Tsunamis

Is it really "developed" when it's not actually been made yet?

No, it's not, but making grandiose claims about what something could become in mere decades (just possibly, if everything falls perfectly into place) is how you try to get a bigger slice of the ever dwindling pie of research funding. You need to grossly oversell every result.

For those unaware, due to congressional meddling, the NSF [nsf.gov] effectively now requires you to tell it what great societal or economic problem your research is going to solve in the grant application, i.e. before you even get preliminary dat

• #### Sound proofing... (Score:4, Informative)

on Friday December 27, 2013 @02:57AM (#45794279)

This is where the money in this idea lies. If you had an effective way to completely deaden low-end bass, then you'd dominate the market. Being able to build a whisper quiet nightclub or listening room would be incredible.

I'm about to embark on some deadening and sound proofing in my basement theatre, and I'm now thinking I really need to look into the metamaterial research to see if it can offer anything there.

• #### Re: (Score:3)

Too bad a single setup of meta material typically only works for a very specific wavelength.
So, it could be helpful with applications using a defined wavelength (for example soundproofing an array of many ultrasonic transcievers from each other to reduce interference), but it won't mask you from a wide array of sounds.

• #### Breakwater design (Score:3)

on Friday December 27, 2013 @04:31AM (#45794563)
Breakwater design has changed a lot over the centuries. The primary design will deflect the waves using a heavy earth and rock embankment. Over time, it was found that an embankment made from irregular rocks or concrete castings work better than regular cubes. You could call that a meta material if you want, but it is simply a smart way to combine deflection and interference with the waves to achieve the desired smoothing effect.
• #### Finally (Score:1)

We finally discovered Wakanda!
• #### Metawords (Score:2)

Someone should invent metawords to defelect metawords.

• #### inertia (Score:2)

I'm not a physicist, but I'm pretty sure these materials can't 'bend' inertia and mass, making this talk about diverting tsunami waves sound pure nonsense.
• #### Lex Luthor could use this (Score:2)

Imagine if Lex Luthor controlled a construction company that did major projects around the Los Angeles area. With each project carefully selected by location, he builds, over the years, a lens that will focus earthquake energy onto a specific building to be specified later, perhaps with a tie-in to current events, destroying it completely.

I should note that I haven't really kept up with Lex Luthor's aspirations since the 1978 film [wikipedia.org].

If he could come up with a good way to trigger the earthquake, the film could

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