video never. had at the back of those. songs to sing along to download to use the code from super. to be able to. have varied causes of interactive exercises are available at d.f.w. dot com slashdot internet and on facebook in the app store. learn german for free w. . well come see tomorrow today the science show on d w. this time we go to the beach where surfing physics teacher explains what waves are all about. we'll hear from an acoustics experts why the sound of waves is so relaxing. but waves can also have

huge destructive power scientists are trying to predict rogue waves. oceans are in constant motion waves pocket the surface of the water but ways are not equally high all over at the equator they tend to be more shallow at higher latitudes they're stronger. a wave can traverse entire oceans but it's not actually the water itself that is moving with the wave confusing let's head to the shore and find out about waves and where they come from. the atlantic coast of portugal and spain towards waves large and small per surfers of all novels of ability. as an enthusiastic wave rider. he's also

a physics teacher so he knows something about how waves form and what surfers find really epic a perfectly shaped long way surfing requires practice and patience with all your good stuff and it's often just luck you have to be in the right place at the right time there are so many factors the height of the tide the way in the wave period that play a role and sometimes there's just a tiny window maybe half an hour a day when you get good ways and the rest is rubbish you know. this looks like a good moment. the surfing science teacher seizes the opportunity. but what parent wakes exact. weights are the transfer of energy. transfer energy. so far today's waves have been pretty tame let's do an experiment on the beach and

i ask a question it's astounding we can see how the wave is being propagated through the length of the cloth his shaking is providing the energy that's being transferred. but what does a wave in a towel have in common with a wave in the ocean. more than you might think. whether it's a towel wave or a water wave hit or the waves transport energy not matter. even though that might not be obvious that seen from the beach the water is just the transport medium. just like the surfers waiting on their boards the molecules in the water don't move over great distances the waves propagates much faster 0 that is the energy in waves come from it. it depends on what kind of hoops we're talking about. the moon this gravitational force keeps the ocean in. ocean. it's attraction

produces the rising and falling sea levels known as ebb and flow. but the waves that interest surfers are generated by the wind what matters is how strongly and how long it loads it gets the water particles moving. here's a simulation the hairdryer makes a wind which makes waves. planes can travel for days and hundreds of kilometers from their place of origin in the middle of the ocean to the coast. long and shallow waves tend to travel faster than the short highly ones which slow themselves down. within the waves the water particles follow circular or orbital paths. that this orbital movement extends deep down in the water the deeper the water the

smaller the radius of the circular motion but one thing is circling the water particles at the seabed they're stopped and then. that in a shallow water waves place. breakers are typical shallow water waves. they occur when the water particles below the surface are slowed at the bottom of the particles above continue to move on their circular patterns unhindered. to. be unchecked water particles move upward making the wave tower up at the shore and then break. to the delight of the surfers. ya block not it makes you happy it's very exhausting

by night time you're totally knocked out of but happy you forget all the everyday stress it's just great. but the best breaks don't come on demand which is why this evening i'm curious he got is still in the water waiting for that perfect wave. that waits can also be scary in the past sail is reported towering waves that suddenly erodes out of nowhere on the open ocean but scientists dismissed these accounts until the mid 990 s. that is when a so-called rope weight was documented on an oil rig in the north sea. this 3 clay measured 25 metres in height. now researchers are trying to understand and recreate these monsters. can you show waves that are between 8 and 10 meters high are commonplace but at any

given time anywhere in the wild there are likely to be 10 or so rogue waves up to 30 metres in height. they appear suddenly and without warning. scientists recreate rogue waves here in the wave basin of the new push concious institute in hanover here the water isn't whipped up by storms or currents the waves are generated by these panels which are controlled by a computer. they enable the scientists to simulate nearly every kind of wave at a scale of $1.00 to $75.00 everything from small harmless ocean swells to gigantic monster waves on the way for me to shows the current height of the way. up and is going to simulate the drought in a way the 1st rogue wave ever documented it was measured on always drop an oil rig in $1009.00. 5 i didn't notice we can see it clearly in this north sea story it

shows 8 to 10 meter high waves on average during the storm then here we see an extreme of that a wave that's 25 meters high a rogue wave months of. what's unique about rogue waves is that they're $2.00 to $3.00 times higher than the highest waves around them. and that also makes them $2.00 to $3.00 times as steep. a rogue wave has almost 10 times as much force as a normal way. for a long time it was a mystery how a wave more than 20 metres high could suddenly arise in a storm of 8 metre high waves but only to vanish shortly thereafter. the explanation waves don't spread out equally in the water waves with shorter wavelengths in which the troughs and crests quickly follow each other only move

relatively slowly. waves with long wave lengths are faster. they can catch up with shorter ones. when that happens they can combine to create a higher way. if several waves join together in this way they can become a rogue wave. broke waves are extremely steep a ship has no chance of sailing over the crest of a rogue wave as it can with an ordinary one instead the water crashes over it. the water masses collide with the structures on deck with tremendous force in a real scenario at sea this would break the ship's windows and bend heavy steel elements. scientists can simulate monster waves in a laboratory but what they really want to know. is under what conditions and how

often such waves will occur in nature. what is the likelihood of a freak wave forming. previous estimates had suggested that the probability of finding a way higher than 10 meters in a heavy storm would only be 0.03 percent. but measurements show that giant waves occur much more frequently the actual chance of waves forming that are at least 10 meters high is closer to one percent. decline in the classical approach of here's to the theory that every wave has a certain energy that the energy of one wave can sometimes overlay that of another to form a particularly high wave and that the component waves each with their own energy can thereafter continue on their way for. newer approaches theorize that energy can

also be transferred from one wave to another and that this 2nd wave moves on with somewhat more energy and the 1st one was somewhat less it was when you can. surf the waves would take on energy from their neighbors and grow at their expense into rogue waves that can endanger even big ships at sea. this is not a rogue wave but it's a nami tsunamis are not generated by wind at the surface but on the sea bed usually by earthquakes when tectonic plates colline releasing massive amounts of energy and displacing huge volumes of water. that are at it seats anomalies are still relatively small waves traveling fast. but when they reach the shore they slow and

the water piles up into towering waves dozens of meters high which can destroy everything in their path. waves and only powerful they're also pretty loud. they can get up to 100 decibels that's as noisy as a jackhammer 10 meters away. the sound is generated when the waves break but despite the volume the sound of waves is generally perceived as relaxing. waves break on the shore it day and night and have been doing so for millions of years. nobody seems to mind the noise in fact most really enjoy the sound

why is that. if anyone knows the answer then scientists at the frown hoover institute for building physics based in stuttgart germany. this is our echo chamber music to test absorbers. peter punched ed and his colleagues research how people experience the sounds that surround them the field is called psychoacoustics they also develop products. here they're working on a booth with sound absorbing properties where one can conduct private conversations without being overheard. this chamber is anechoic that is totally soundproof it's used to test things but it's not actually pleasant to spend time man. this is to lecture and it's perhaps rather too quiet we're not built to hear nothing at all it's we can't close our ears in contrast to our eyes how is

our own original vigilance system warning us of dangers seen our hearing is always switched on designed to receive signals and issue warnings to protect us from harm seeking. for good falzon to violently supervolcano. this kind of sound is better than silence if we want to relax. i just like. that has to do with the structure of waves. it's not a uniform constant noise with the same volume but rather it rises and recedes regularly it's. like the surging is a very relaxing kind of sound for us very familiar and with positive associations. for. prostitution acetates your own and white pink and brown noise are characterized by equal intensity at different

frequencies the sound of waves exemplifies that when you give oyster and the sounds of produced as water slaps on to water and displaces add went out without movement there would be no noise just in order to be of equal kind toward. people like certain kinds of sound with or without ocean waves technically generated white noise is sometimes even deployed in workplaces it can disguise other sounds. and it can be soothing. and see this kind of noise doesn't carry information so after a while our brains infer that they don't need to do anything until in the noise out all register it's. when feud even gets hutto so that is why it feels relaxing. by listening it's not real silence there is something bad but it's not threatening

his take it's not telling us anything so we can just relax your attitude as you incent by 2. waves might still primal anxiety and let us sleep easy but one of the ocean is far away. is highway noise and effective substitute. is one for been traffic noise isn't all that different when the vehicles are just passing by at a constant speed and not starting and stopping the stuff once again the sound is continuous over time and have a constant volume because the cars are driving at around the same speed but i live in the fog so i get on with michael a from his we need. so in a sense listening to a highway should be a good law by except our brains link the sounds to the cars about any associations are anything but mellow traffic speed concentration stress

i believe the sound of waves by contrast feels friendly reminds us of the cation or allows our minds to simply go blank. we understand facebook what you think of when you hear the sound of waves. myra or from venezuela loves the sound of waves and says nothing is more relaxing than the sea and its waves. every writes from indonesia that the sea is amazing almost alive it's always rippling sometimes slowly sometimes strongly and sometimes it's terrifying. for pius the sound of waves is very familiar. he wrote to us and she saw healy that he's a skilled swimmer and that's what he knows. that the water from indonesia is more interested in the ocean waves as

a source of energy and says we might be able to use them to replace fossil fuel and that's true. there have been many attempts to use the forces in the ocean waves to generate electricity we've been successful with other forces of nature solar power for example is most advanced in china india and japan according to the international renewable energy agency. other countries are focusing on wind energy here to china is in 1st place but it's proven very difficult to harness the energy of waves. immensely powerful forces. huge wind generated waves. up the tides controlled by the moon's gravity. with an area of 360000000 square kilometers about 70 percent of the earth's surface is covered by

water. most of it's in the oceans which could be a massive force of climate friendly energy but how can we harness that power tidal amplitudes very dramatically around the globe in parts of western europe there particularly pronounced. the 1st tide mills were built in the middle ages or even earlier they were driven by the daily changes in water levels. in the 1960 s. this idea was picked up again and engineers built the 1st big tidal power station impression the end from. turbines inside the tunnel barrage are driven by the ebb and flow of the ocean. but the engineers and country to prop. i'm only few babies are suitable for this type of power plant and the barrages also disrupt the coastal ecosystem. but that didn't stop them they saw other ways of using marine

energy this time focusing on the strength of waves. wind generation surface waves tend to be large and strong as high latitudes of the northern and southern hemispheres. in scotland in the 1970 s. scientists developed a series of new mechanisms intended to convert the energy of surface waves into electricity many believe the way that energy converters were on the verge of a breakthrough. one such device was called the salters duck named after its inventor stephen salter from edinburgh the duck was tested way tunnels but never on the open sea. eventually these ideas fell by the wayside. in the early 2000 came a new attempt with this snake like offshore device it's linked cylindrical sections

flex and bend in the waves and convert the motion into electricity but it never got past the prototype stage. german engineers are currently testing another system the knee most project involves flotation modules connected to pulleys on the seabed by flexible cables as they're pulled by the motion of the waves a generator transforms the mechanical energy into electricity it's being tested as an addition to offshore wind farms. so far most of the approaches to topping marine power have got nowhere one reason the formidable technical hurdles. wave heights change continually out of the force of the waves to stand up to the biggest waves the machinery has to be very robust but this equipment produces too little energy. when waves are gentler there are many different ways of harnessing wave power but they're all still too expensive to be viable. and want to tidal

energy developers shifted to anchor in the turbines on the sea floor bother than in barrages but underwater repairs are expensive. the latest plus i plot forms have turbines mounted underneath that are more accessible and thus easier to fix when the corrosive salt water damages the machines. although the energy of the wild and salty seas has repeatedly proved difficult to harness many engineers remain optimistic that a breakthrough is just around the corner. because it is red white object even if it is. now it's time for our viewer question this week it comes from morocco i took a look at the ways in the ocean and asked where the water is really transparent.

the water in this class looks transparent. the ocean looks blue book both water on today so why the difference. to understand that we need to delve into physics color is an effect of light and without light everything turns black. the light from the sun made the white but it's actually a mixture of a range of wavelengths some of them are invisible to the human eye like ultraviolet rays other parts of the spectrum are visible to us and we see them as red orange yellow green blue violet. and when they're mixed together we perceive the light as white. so why do. different things have different colors. because they absorb different parts of the light spectrum the rest is reflected and picked up by the receptors in the eye. the

material the jacket is made of absorbs blue green and yellow light red like to be reflected so the jacket looks red. so what's going on with water. close to the shore where the water is shallow the light most and passes through without being absorbed or reflected. by one light rays fall on a larger body of water the red orange yellow components of the light are absorbed more strongly and the blue light is preferentially reflected. so that's why the ocean looks blue it's not because it reflects the sky. divers can observe the effect of absorption as they descend into the depths 1st the

red light disappears then the green and then the yellow what remains is blue light that hasn't been absorbed by the water further down that too is absorbed and you get to a point where no visible light at all has penetrated. so the color of the water seems to have depends on the quantity of it large volumes of water look blue. but a small amount of water appears transparent. you know the science question just ask you'll find us at d. w. dot com slash science and on twitter and facebook. here's a fun fact waves have a strong effect on animals and plants take the panicle. you know those little alfred pods that hear to stones or shells in the water they rely on the waves to bring them they knew trance and the waves determine how long their penises are

where the waves are strong bonnie goes have a shorter penis when the flow is gentle it grows longer and in any case melbourne the coals have the longest penis in proportion to their body length of any animal. that's all for today next time we'll see what happens to the vision of hyper travelling at a 1000 kilometers per hour is not the transport of the future find out next week till then but i.

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