eli5: Waves come in at New York, and waves come in at Europe. What happens in the middle?

eli5: Waves come in at New York, and waves come in at Europe. What happens in the middle?


Waves are not current. Waves are really just pulses of energy and can pass through each other. They are mostly generated by wind. They can reflect and refract like light. In the middle of the ocean, most of the waves travel in the direction of the wind. When the wind changes direction, the already generated waves will keep traveling in the same direction (and will eventually dissipate) and it will start generating waves in a different direction. As a result, the open ocean has sets of waves traveling in several directions. Form the perspective of a small boat, there will be a main swell and then "under" it, you can usually notice secondary swells traveling in different directions. Waves go slower in shallower water. Like light entering a lens, this causes the waves to turn towards shore. As a result, any waves traveling at an angle towards the beach will get steered straight towards it.


[Video explaining why a slower wave means it turns towards the shore (basically refracts).](https://youtu.be/GoFqMVrkHr0?t=198)


Interesting. But God damn that video is so painful to watch.


I read your comment, thought about what you could have meant, then watched the entire video anyway. I can't remember if that's sadism or masochism at this moment.


masochism for those wondering


Thank you. I never bothered to Google it.


yea you can think of it like m for hurt me. s for hurt someone else lol.


S&M as taught by Barney the Dinosaur


Sesame Street. "S is for sadism"


It's good enough for me. Sadism sadism sadism, sadism starts with... S.


hurt me daddy




Gently hurt a dad this Father's day




> Thank you. I never bothered to Google it. Good choice


Yeah, same here. I even started the video from the very beginning, rather than the timestamp. It's a powerpoint without a presenter. Why did I watch the whole thing?


> It's a powerpoint without a presenter. Pretty sure that's the point, the channel description literally reads "Silent: The teacher can run the video in his class and comment on it in his words in any language and accent."


Ah, I didn't see that. Will then it does a great job at serving its purpose


Or someone wanted to make educational videos but hated the sound of their own voice.


Pretty sure thats the power....point


must... resist... watching... video GAH i failed.


I did NOT fail to *not* watch the video. Watched maybe nine seconds of it. That is a definite WIN!


I didn't learn. I wasn't gonna even click it till I saw the comments dissing the video. Why do I do that to myself?!


You've convinced me. I'm going in


Sadism is telling your friends to watch it


Ok… this doesn’t seem so bad… do they not like it because there’s no sound?… ok what are those squiggles doing… oh … oh my god … oh lord turn it off TURN IT OFF WHAT ARE THE SQUIGGLES DOING OH MY GOD MAKE IT STOP That’s kinda how I felt watching that.


Hahaha this made me lol. Can confirm, video is unnecessary to watch


Sadism refers to someone exhibiting traits like in books written by the Marquis de Sade who philosophically justified doing literally anything that causes pleasure to oneself even at others' expense because he saw it as fulfilling what nature designed us to do. His best known work is 120 Days of Sodom which is about some rich nobles in France who kidnap a bunch of women and kids and basically fuck them to death for 4 months. Sadism then is basically now used to refer to taking pleasure in the pain and suffering of others.


I know I’m late to this comment, but can anyone embroider this last sentence on a pillow? (echoes into the mist) 😂 thanks


Sadist for the poster, masochism for anyone watching after knowing it’s painful to watch.


I‘m confused. I watched the whole video but i don’t know what you are Talking about.


Almost watched it anyway too. You might have saved me.




You are so right. Lots of good information but my eyes were bleeding by the time it ended!!!


By engineers, for engineers. A lot of manuals can be explained that way.


My favourite part is when they start explaining angle of incidence & refraction.


I almost pulled my face off. At that point I was convinced they were just fucking with me.


Painfully awesome…


Funny how if you put it at 2x speed, it seems normal, or even still a little slow.


That’s why light refracts


> Waves are really just pulses of energy and can pass through each other. Like when the beams of light from two flashlights intersect but each continues on as if nothing happened. Or like when many people talk in the same room, but you can hear each one's voice and focus your attention on it.


>Or like when many people talk in the same room, but you can hear each one's voice and focus your attention on it. People can do that?


Today on "finding out you have a sensory processing issue on the internet"!


Nah I know I have ADHD. Diagnosed at 42.


Yeah I was 30 before I realized hearing literally everyone within earshot at once, all the time, was abnormal.




Don't fall for that .... this a trap... you will die


I can only focus on the voice of someone other than the person I'm trying to have a conversation with.


Clearly you gotta talk to the right people


That's ADHD friend, welcome to the club.


sensory (specifically auditory) processing issues are not exclusive to ADHD


It is quite a hurdle for autistic people who often cannot


And many people with ADHD. And people with other auditory processing disorders.


Haha, I kinda feel you on this one. I have an extraordinarily hard time tuning out secondary conversation. Interestingly, when I've taken shrooms, I suddenly gain the ability to focus on a single audio stream, like tuning into a radio station. It feels like a superpower.


I can relate. When taking shrooms, I can pick up individual instruments in a song much more easily than normal. It even gets easier to understand spoken Japanese, a language I'm learning but am by no means proficient in. A similar thing happens with vision; I feel like I can stare off in the distance and focus on a specific area and almost zoom in as though I'm using binoculars. These effects make sense if the theory about psychedelic mushrooms turning off the brain's natural filter (that tunes out a lot of the information we receive on a regular basis to prevent our senses from being overwhelmed) is correct.


>These effects make sense if the theory about psychedelic mushrooms turning off the brain's natural filter (that tunes out a lot of the information we receive on a regular basis to prevent our senses from being overwhelmed) is correct. If I understand, isn't this a similar phenomenon described by people with autism (without the shrooms)?


As a person with autism who frequently does shrooms… no


> I can pick up individual instruments in a song much more easily Even just weed improves my ability to do this! When I'm nice and high I like to put headphones on and listen to music bc I notice each part of the song rather than just the whole.


It makes me so happy when I see mention of psychs outside drug specific subreddits


Yeah, the world is starting to grow in the right ways


This hits home


I´m even worse. As soon as there is any crosstalk, or an ambient noise loud enough like a vacuum cleaner I can't understand any of it. I actually thought that there was something wrong with my hearing but when I went and got it chercked it turned out it wasn't just fine, but extraordinarily good across the frequency spectrum, and I scored well above average in the higher frequencies.


Two conversations? No problem. Three conversations? I'm sorry, your words what got the mixed fuck ah you no what pencil Jesus happen with um crap Bethany seat Chomsky fear no popopo su hill te shar em kuf. Say again?


Fuck, I tried to read that as an actual sentence and fried my brain to shit.


Occasionally, barely


I have single side deafness and I definitely cannot


So I've heard (pardon the pun).


Yes, it's called the cocktail party effect.


You might have autism


Diagnosed with ADHD at 42.


And sometimes it’s a particle


"Why not both?" - Louis de Broglie


"Why not" - Zoidberg


If you're interested, there's also a phenomenon called cross seas. It seems to illustrate u/bob4apples points about waves continuing even though the wind changed and they eventually run into other waves. Apparently the angle of the waves coming together is very dangerous for boats. https://bit.ly/2TGG7DI Edit: shortened the link


It's not that something magical happens as a result of the waves coming together, but that there is no direction for the vessel to turn to avoid being broadsided. Boats are designed to cut through waves by pointing straight at them. One good wave to the side of the vessel and it can be upside down.


If you'd like to see a real-time map of what's being described in this post, check out [windy.com's wave visualization](https://www.windy.com/-Waves-waves?waves,49.382,-65.281,5). You can see the district areas of different wave directions, even flip back and forth to compare it with wind.


First image is wind in the Atlantic right now: https://i.imgur.com/SVHqm1H.jpg Second image is the waves in the Atlantic right now https://i.imgur.com/cB0QPvw.png


Also, regarding the waves, it's not the water that travels in the wave direction, but the energy of the wave in it. The water just goes up and down like a piece of wood floating on the surface (assuming that the wind isn't pushing the wood with it). The energy is basically the molecules of water getting compressed, feeling sick of it and expanding. The wind causes the water to compress when it pushes on it, or, in the case of a tsunami, the humongous stones (earth crust) from the bottom of the sea when they move around.


Just fyi, there isn't really any compression of the water happening in the water (that would take crazy amounts of force), it's more like what you said in the first paragraph. It's sort of a bundle of energy that flows through the water and generates localized motion at the location of the wave


u/ANGLV3TH is correct, any force on water causes a corresponding compression of that water. It's just that the resulting compression is very low for the force applied (modulus of elasticity is high). It is said it is incompressible because compared to gaseous fluids it is practically incompressible, it can transmit high forces with very small changes to volume. For understanding fluid dynamics, the incompressible analogy usually captures the physics of what is going on, but it isn't perfectly accurate of the true physics. So what you said is true, it takes a crazy amount of force to compress water to a noticeable change in volume. But waves do work by having oscillating patterns of particle compression to transmit energy. (I'm pretty sure I got that all correct but it's 4am and I could have made an error in my explanation.)


I know all of that. Treating water as incompressible is an accurate enough approximation for almost all cases. My point was that the amplitude of the wave is not caused by compression of the water. Just fyi, it takes 2 MPa (~20atm) of pressure to increase the density of water by 0.1% There will be differential pressures and pressure gradients, but the effects of compression will be negligible


What happens with rapidly changing wind direction, would that store energy in the waves and make them stronger?


Depends on if the frequency lines up


I have follow up questions: How fast does the wave change it's speed? So, let's say a wave is going in a particular direction and hits shallow water. Is this change in speed gradual or is it instantaneous? If it is gradual, how is that rate affected?


Wait, waves are not created by wind? They are created with the changing of the tides. And the tides are created by the gravity of the moon, isn’t it? I was always taught that are oceans are basically drawn towards the moon, resulting in a predictable tide. And the movement of all that water causes the most important waves. Edit; thanks all for jumping in and giving me a much needed and long overdue education on the matter. I love reading it and learning from it!


Ocean waves have multiple sources.


Blow up a nuke under water and waves move out at 360 degrees. Waves are generated by energetic forces acting on the water.


Uhm, that's not how it works. In the oceans, tides are actually the water moving toward the external gravitational forces -- Sun and Moon -- sloshing the water back and forth over time. Tidal action only creates "waves" as a side effect, normally when the sloshing water runs into something, like a continent. Because they allow the water to flow around them, islands rarely have any significant [tidal range](https://en.wikipedia.org/wiki/Tidal_range). One of the more spectacular tidal events is a [tidal bore](https://en.wikipedia.org/wiki/Tidal_bore), like [this one in China](https://www.youtube.com/watch?v=k6fr6GUSmAA). [Ocean currents](https://en.wikipedia.org/wiki/Ocean_current) are water *moving* along a path primarily because of imbalances in heat and density -- here are the [Northern Pacific Ocean currents](https://www.windy.com/-Currents-currents?cmems,currents,17.765,-171.024,4) as shown at windy.com (a great site for hours of discovery). Like in the atmosphere, ocean currents can occur at multiple depths, moving in different directions. Some very deep, cold currents move at very slow speeds. Ocean currents, for the most part, do not directly create waves. [Wind waves](https://en.wikipedia.org/wiki/Wind_wave) are caused by friction between moving air and water. They can be tiny ripples, or ship-swallowing monsters. [Wind fetch](https://en.wikipedia.org/wiki/Wind_fetch) is a fascinating rabbit hole to go down. Wind waves are mostly a "local" effect, for various definitions of "local". [Ocean swells](https://en.wikipedia.org/wiki/Swell_\(ocean\)) are sort of wind waves that grew up. They are normally the result of prolonged wind blowing in a particular direction. Here in N. California, our predominant swells are from the NW and are generated by big storms in the Gulf of Alaska, and from major systems as far away as Japan. It is not uncommon for us to have multiple swell-sets moving in different directions from different storms. Wind waves and ocean swells are *not* water moving, they are pulses of energy moving *through the water*. Tidal waves, tsunamis, and megatsunamis are other fun rabbit holes to go down.


Moon doesn't create tsunamis, but shifting plate tectonic actions do. I would think tsunamis make the most important waves, followed by hurricanes. The moon just makes a bulge in the surface of the ocean that hits any shore twice a day, called the high tide.


> Wait, waves are not created by wind? Then explain how waves are so much worse during a storm, it certainly isn't because the moon is being sporadic in its motion... lol Everything that acts on the water will create waves but wind is the most major contributor.


Just being facetious 😅: Wave pools at water parks are marvels of engineering. The first step of putting a miniature moon into geosynchronous orbit is the easy part. Controlling it's movements to generate those fun waves is the tricky bit and that's why water park tickets cost so much. Also, I think it's fantastic that the commenter is trying to learn more about the subject and asking questions. More people need to do this.


There are many different types of wave in the ocean. Tides are one type of wave (extremely long wavelength waves that have a time period on the order of hours to days) generated by the gradient in the graviational attraction between the earth and the moon (and the sun), whereas wind waves are another type of wave (generated by the winds).


Tide waves are generated by the Sun and the Moon. Storm waves are generated by the storm (wind). When you drop a stone to the ocean, there will be waves generated by your stone (small, but still...) Majority of waves, that we think of when we talk about waves, are wind generated waves.


Giant waves in between. They are harder to notice because the whole ocean is moving/they are more underwater. Imagine the earth is a cup of water, and if you move it around, the water goes from one side to the other, you don't really notice the peak of the water moving in the middle but you do when it hits the sides. Now imagine the cup is a ball (Earth) instead and gravity is holding the water in at all angles, give it a spin and that's what we got.


>Imagine a cup is a ball Mate you’ve broken my brain.


cup = ball


Cup the balls?


Two balls, one cup?


I was scrolling down and I anticipated this… good… this is good.


The day I'm unprepared for a two girls, one cup reference, is the day I turn in my gun and badge and walk into the sunset. And they day I walk into the sunset is the day I am able to walk at the 30km/s necessary to lower my orbital pariapsis to intercept with the sun.


I was having a good day Until this and hay fever fucked me up


fuck hay fever goddamn


Trust mine to get worse the day I DON’T bring my eye drops


Cup and Ball Torture?


Someone had to do it.


Better be. Otherwise, there would be a lot more injuries in sports, especially in baseball.


Two Girls, One Cup


One video, no more internet today


[Cradle the balls](https://youtu.be/YgU0YytQVbs)


Work the shaft


Poor Pyrion.




[cup and ball hog?](https://youtu.be/_t-kMYIRMME)


assume spherical cow


Physicist confirmed




Please stop I already tried to pour water into my ball they are not the same.


Put more mass into the ball until the water is trapped on the surface.


Where do we find a ball the size of your mom? How do we get your mom in the ball? I’m just kidding lol


Well I do know how to fit a pair of balls in your mom, so maybe we can extrapolate from there.


You put the balls in the ass? Impressive. Maybe earth and moon are just a pair of balls in an ass.


Flat earth, proved


Take that black science man


I fucking roared at this lmao


assume spherical cow


Topologically a cup and a ball are the same


Luckily our planet is a flat disk so you can just picture a shallow cup, no imagination required.


i mean can you imagine if it were a sphere? The water would fall down the sides and there would be no more ocean.


Well, there isn't any more Ocean. All the ocean is already there.


Was gonna say this.. I almost had a seizure reading that


Can someone explain gravity like this guy is 5 please?


If you hang two things in space, they start to move towards each other. The heavier the things are, the more they accelerate. The earth is just a very big thing and all the stuff on it is a bunch of little things. So we're moving towards the big thing always. We experience this as "things being up and down." That's if you're 5. It gets way cooler though.


> That's if you're 5. It gets way cooler though. [Astrophysicist explains gravity to a child, teen, college student, grad student, and an expert.](https://www.youtube.com/watch?v=QcUey-DVYjk)


Here's an Eli10: Imagine an ordinary bed sheet, being stretched out in all the edges. Put some sand on it. Some of the sand might cluster together, pushing down the sheet, pulling in more sand, pulling more stuff in, and so on. Now imagine the sheet is 3d space, and the sand is atoms. That's if you're 10. It gets way cooler though.


If you could put the universe into a tube, you'd end up with a very long tube. Umm, probably extending twice the size of the universe, because when you collapse the universe it expands and, uhhh, you wouldn't want to put it into a tube.


Everyone knows a cup is a donut.


You’re a donut.


Topologically speaking, yes, humans are donuts. That is, unless you have piercings.


and you ignore the nose/sinuses.


Oh shit, I forgot people have noses. I guess I'm only a donut during hayfever season.


You also forgot that we have more than one exit. Topologically, humans are overalls.


[More of a 7 holed donut](https://www.youtube.com/watch?v=egEraZP9yXQ)


Only if it has a handle, like a mug. If it doesn’t have a handle it’s just a sphere.


The ball is on a string and attached to the cup!


There's no worry if you don't catch the ball in the cup, and clean-up is as easy as catching a ball in a cup!


found the future topologist


My first true guffaw of the day and the guy on the train next to me thinks the gringo has gone crazy


No, I'm sure he already thought that for some reason or another.


That's not how it works. The Earth doesn't spin around under its oceans and created waves. Waves are simply water movement due to winds, temperature changes, and tidal forces from the moon. If we were in a vacuum, with no moon and no sun, then Earth's water would remain pretty motionless. There would still be some movement due to volcanic activity, and various forces that both life and chemistry impart on the water, but that would be it.


Also, the depth of the ocean in between the coasts makes waves with greater kinetic energy have much smaller peak-to-trough height. So waves in deep water don’t indicate their strength at the surface.


>imagine the cup is a ball assume spherical cow


Mate you forgot the vacuum


It's been a while since I read an ELI5 and thought, blimey that guy nailed it for me. But you did that, so thank you.


Blimey lol


“Blimey ‘Arry!”


2 X universe= Tube


It's not a bowl.


I do this with your son every night......


>Imagine the earth is a cup of water And a giant T-Rex sneaking around is what's causing the waves


Those are not mountains they are waves


So are you saying that if I put a ball inside the ocean and regard it as a reverse spherical cup, then.. I put the whole ocean in a cup! amazing! P.S. Please ignore any ocean suddenly disappearing/moving. Now excuse me as I start planning an unrelated trip.




There are waves in the middle. Waves "come in" because the water is getting shallower as you get close to the beach/coast. In the middle, they just go up and down.


Yeah a wave has speed and the only place to go is up once it gets shallower. Eventually it rises high enough that its momentum topples it over itself


and if there is any change in ground elevation underwater, surprise tsunami!


If there's a reef then you can get perfect surfing waves that break consistently in the same place (for a bit until the tide changes). One of the most famous is Banzai Pipeline and Backdoor in Hawaii which is actually three reefs that work at different times as the tide changes water depth


thank you for restoring my faith in this sub! Reading all the other top comments is so freaking tilting in this thread. Talking about wind deciding the direction in which waves travel or turning cups into balls...? Waves are water molecules in a up-and-down motion, nothing else. You don't need wind for them to propagate over the ocean or any body of water for that matter. Stretch out a bedsheet tight, grab the center and pull it up and let go. As it goes down, waves spread in every direction, just like they would in water. There is literally no sideways motion in there. That only comes into play as waters get shallower. As to what causes the up-and-down motion, that's a whole other question. Ask a geologist, they may have an answer to that.


Lol you're pretty wrong. The individual molecules travel in a circular motion. https://www.acs.psu.edu/drussell/demos/waves/wavemotion.html


Most of all the waves are cause by wind. The friction between the wind and the water causes waves to form. You can verify this by blowing over a pan of water. Especcially in open water, waves can build up energy, becoming very long in wavelength and high in amplitude. Near shores it gets less deep, this forces the waves to become of shorter wavelength and slower. Because of this, the waves always turn towards the shores, and not in the original wind direction. Also, I am surprised by the amount of bad answers i read in this thread. Many people apparently overestimate their knowledge on this.


In addition to this a lot of people are forgetting that local surface winds are generally dominated most of the time by convection, land is hotter than sea. Air over the land heats up and rises causing a suction that draws air in from over the water, meaning that the majority of the wind at the shore is in the on-shore direction. And thus the waves are also driven in that direction by the wind. Lots of locations known for their wind are driven by these types of features.


fascinating thanks




> majority of the wind at the shore is in the on-shore direction Do waves ever go out to see like during a hurricane?


Yeah sort of. The size and shape of waves are dependent on a lot of factors including the directions of the wind and water and the depth of the water. In the middle of the ocean where the water is effectively 'infinite deep' from the wave's perspective they will generally be blown into large, long rolling waves with sides of relatively shallow angles. As they approach the beach they get pushed up from the bottom and become the much more steep and eventually breaking waves you normally see on the beach. But out in the open ocean those waves will have lots of momentum, and if the wind does a 180, the waves will keep rolling in the 'wrong' direction for a long time due to momentum. When this happens the waves will become steeper on the windward side as the wind pushes into the on-coming wave and this can eventually cause them to become breaking waves even when they are still out in the open. So if you have a strong off-shore breeze it will generally just cause the waves coming in to become steeper. If that breeze stays for a few days you may see the water become very flat as the momentum dies out and the waves start building up in the opposite direction. But you will never see large waves rolling away from the beach because you are always at the start of the wave building process there.


fascinating thanks


fascinating thanks


Ah! Thank you! lol


>Many people apparently overestimate their knowledge on this Welcome to reddit. You must be new here; I'll show you around.




Can confirm, there are no waves on the entire coast of eastern North America, except New York city. Probably why its so popular.


Well OP said New York, which is the state. So the entire Eastern Seaboard was reduced to a state. Being from Jersey, I'm displeased either way. We have like 3 more miles of Atlantic Coastline than NY state, damnit.


The waves pass through each other in the middle. When the waves hit a shoreline some of that energy gets reflected and begins moving in the opposite direction, back towards the other shoreline on the opposite continent. Most waves aren’t perfectly reflected though so they end up moving at angles to each other which allows them to move past one another without too much energy loss. And some waves moving towards the same shoreline will meet up and add together. The moon also adds energy by constantly pulling on the water as it gets closer and farther over the night cycle. You can try the experiment yourself in the bathtub, stay as still as you can and wait for the bathwater to calm to a still state, then just push your hand through the water towards the back of the bathtub and watch the wave bounce off the back. It will then travel towards the front and then bounce towards the back again. Here your hand is adding energy like the moon and you can start to get predictable tides if you add waves at a constant rate.


More waves. Wind blows the water to create most surface level waves. This happens in deep water as well.




I'm sorry but this comment made me laugh, thinking OP is referring to a city instead of a state shows the perspective you have of the world. /s


The waves that come in at Albany are truly inspiring.


We call them “Streamed Hams”






A good way to think about it is if a tsunami was approaching. The tsunami is barely noticeable out in open water below you, but closer to shore you get, depth is lower so the only place the wave has to go is UP.


Wind and waves. Wind blowing across the ocean creates waves that move in the direction of the wind. These waves can travel across entire oceans. So the ocean is full of waves , often moving in different directions. When waves meet, they just pass through each other and continue on their way. So there can be one group of waves moving toward New York and another group of waves heading towards Portugal. If you go to [windy.com](https://www.windy.com/?43.197,-44.297,4) you can see all the different wind patterns. You can zoom in and out using the + and - buttons in the top right, click and drag to check out other areas, and hit the play button on the bottom left to see the wind forecast play out. Spain and Portugal are going to have some great surf in a few days from that cyclonic system heading towards their coasts.


On a related note, can you go under a wave? Like in a sub or scuba diving? How far down do they go?


Waves tend to go in the direction of the prevailing wind. The waves don't actually move, the energy spins in a circular motion. The energy goes down in front of the wave and up in the tail of the wave. The the faster the wind blows over the fetch ( distance and duration the wind blowing the same direction), the more energy builds up. The amplitude of the waves increase as the depth of the water decrease because the circling energy starts pushing against the bottom. When the depth of the water reaches 1.4x the height of the swell, the waves breaks. Swells are measure by period in seconds and amplitude ( ft in USA ). The the larger the period the period the faster the wave energy moves, resulting in a bigger breaking wave. The more quickly the depth of the water changes the more powerful the wave break. Look up the heavy deep water Reef breaks ( Jaws or Pipeline ) vs mushy beach break in the Gulf of Mexico. A seismic wave (tsunami ) is very low amplitude but travels almost 2x as fast as a regular wave.


I dunno, I find all these explanations quite weird for a 5 year old. The water is moving the same anywhere, put a wall /coast anywhere in the ocean and you'll get the same thing. Imagine a pool, water "waves" up on the sides, but it also waves up against you, just because you're in the way