How the tides REALLY work
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- Опубликовано: 9 июн 2024
- Learn more at Waterlust.com
Join marine physicist Dr. Patrick Rynne as he explores the science behind the tides, what creates earth's tidal bulges, and why the tides are bigger in some places than others.
Special thanks to artist Sarah Cameron Sunde who provided some awesome timelapses of the tidal cycle from her project "36.5 / A Durational Performance with the Sea, 2013 - 2022". If you're a fan of the tide, definitely check out her work at www.36pt5.org
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This is a wonderful piece of work. It makes a relatively complex thing easier to understand, without dumbing it down. Excellent eductation going on here.
This is a wonderful piece of shit. Excellent eductation for sheep.
I was a commercial fisherman. Maine USA. TIDE IS 10 feet. Florida is 1 foot. LOL. There is no bulge. The earth is flat.
@jiphy did you ever fall off the edge and hit your head?
Oh it is dumb as hell what this show spews. Open your eyes we are stationary.
For millions of years we chase a sun going 500k miles per our as we go around it at 66k miles per hour and spin at 1,000 mph at the equator.
We still see the same constellations with no parallax.
In winter say we are at 3 o'clock and in summer we are at 9 o'clock, right window left window yet the same view. Bullshit
Can't work
There is no tide on Earth
Tides are long waves across the oceans. They are caused by the gravitational force exerted on the earth by the moon and to a lesser extent by the sun. Wiki.
In fact, tides are an artifact of the up and down movement of coastlines in a stable ocean, caused by thermal expansion of the earth's crust due to sunlight moving westward.
Some coasts have no tides, some have only one tide, some have two tides, and some have four tides per day. Tides vary in height from 0 feet to 50 feet and move at different speeds and in different directions.
It is impossible for the moon's gravity to cause tides. Do you agree?
The music is very distracting and loud on headphones. Only saying this because otherwise this is a fantastic explanation! The animations make it so intuitive, appreciate all the work and I hope you make more. Thank you!
Exactly!!¡
agree
Great. Now I can’t ignore it.
It was perfect for me at every volume his voice was just louder
Music is a bit loud and distracting, but great and informative video!
*_Uninformative Vídeo_*_ would be better, don’t you think?_
Someone told every youtuber you need music with your talking. I also find it distracting.
Sometimes, less is more
Hopefully he will reload this, without the noise, and speak slower.
Science teacher and long term sailor here saying Thank you. What a great explanation. It cleared up a few points I couldn't quite get. Excellent education.
5:16 decompose the vectors from the upper and lower planet. You get arrows pointing perpendicular to the poles of the planet. This pushes water out to the sides. Why wasnt this included here? Also, the COG from the moon/earth system is on the moons side of the earth, making the ‘’polar force push’’ greater on one side.
Just for future reference: the Bay of Fundy, with its funky resonance, has a counterexample. The Gulf of Thailand experiences one teeny tide per day. Very weird if you're planning your diving or navigation.
Whoa, we didn't know that. Will check it out. Thanks for sharing
This is the first time I've actually understood the tidal mechanism.
The bit about the water being "left behind" was key.
Well explained!
Thank you! We find that to be an "ah ha" moment as well. Glad you found it helpful. More ocean science videos like this to come, stay tuned.
You’re recent success has obviously gone to your heads. That’s a real shame, considering I tried to give you the clues to explain this mechanism correctly. There is no “left behind” moment or linear acceleration in the earth-moon system. The only “ah ha” moment should have been your realisation that we’ve made a mistake here, and aren’t understanding the true implications of Newtonian Mechanics.
@@Waterlustsurely, in order for the water to be "left behind", then the earth would have to accelerate quite quickly TOWARD THE MOON.
How can that be possible if the earth gravity is "six times stronger" than the moon's?
@@waynemoore8615 the rate doesn’t matter as much as the difference in rates. The difference in accelerations between Earth’s core and the fluid on its surface is very small, but because water can flow so easily and the ocean’s are connected, that small difference can produce noticeable changes in sea level.
⚖🗿The balance point of the rotating system is inside the Earth, not it´s center but shifted to the Moon.
So I would say centrifugal force causes the left behind bulge. 🪐🌀🌛Atmosphere should be affected a bit, too.
I'm 67 and no one has ever been able to satisfactorily explain tides to me...until now!!! THANKYOU!
Our pleasure! So glad it was helpful
While a good explanation of the "tidal forces" between objects, they are not strong enough to cause ocean tides. You have to account for centrifugal forces on Moon and Earth orbiting their center of mass. See Richard Feynman, Lectures on Physics, section 7-4.
You are entirely correct. Never doubt the inspirational teaching of Professor Richard P. Feynman, he wrote the book on Physics education in six easy pieces. The barycentre is key to a correct understanding of tidal formation. I could guide you to his explanation, but you’ll have to endure viewing my cartoon first, which was inspired by his lecture on Gravitation.
You are entirely incorrect. Centrifugal forces are simply centripetal forces that are perceived in a different reference frame.
It's like putting a camera on Newton's apple and dropping it. Is the Earth accelerating toward the apple? No. But centrifugal forces would say such a thing because of the incorrect reference frame.
@@MultiPleaserthe earth is accelerating towards the Apple in an infinitesimally small way though. That’s how gravity works. Objects are attracted to one another based on their mass. While the earth exerts a force on the Apple and it accelerates towards the ground (center of the earths mass), the earth in turn is accelerating towards the the surface of the apple (center of its mass).
@@MultiPleasersurely an apple dropping to earth would be a linear force.
Why are you saying its is a centrifugal force?
@@waynemoore8615 I did not. I said it's LIKE the Earth being drawn to the apple b/c of the different reference frame.
That's the first time I've seen the "four little planets" explanation, or the ellipse-forming simulation. Very cool, very clear, and much more satisfying than the "traditional" explanations. Well done!
The four planets model was our "aha moment", glad you found it helpful!
I agree. I learned this from PBS Spacetime. Their visualization was of the whole earth with connected oceans. Showing it with the tiny planets, or particles, you are clearly able to see why the elongation happens on both sides of Earth. It also makes it easier to explain to someone else.
Best Tide explainer I’ve ever seen, and I’ve been interested in this topic for decades.
The very best explanation that I have seen. I understand the science and I watch certain vids to discover who does not, or cannot explain the science. You clearly know, and you can explain.
That was SO WELL done!!! A wealth of information in a beautifully illustrative short video. So many questions that I've had about tides became clear in a matter of moments.
Right on! That was the goal. Glad you enjoyed it. More marine science videos like this coming, stay tuned!
at 2:53 the statement "bigger objects create stronger gravitational forces than smaller ones" should have been worded "more massive objects.....less massive ones".
Good point
I thought the opposite side bulge was created because the moon and earth system rotate around a point that is located between the earth and moon, creating the 2 bulges. Isn't this true also to some extent?
You are absolutely correct and not only is it true to some extent, it’s also true in every extent. Although, it’s more of a revolving orbital motion around a common centre of gravity between the earth and moon, that gives rise to an outward tidal force across the diameter of the earth. Unfortunately, this well made presentation fell into the trap of trying to explain everything with the gravitational differential, and neglected the actual presence of inertial motion.
A science book I read gave the most basic simple explanation I have heard.
It said the moon pulls the water towards it on the near side, and pulls the earth away from the water on the opposite side.
It said thats why the tides have a higher and lower high tide each day.
Made a lot of sense to me.
With all due respect David, are you absolutely sure what you were reading was a science book and not a comic? If the earth was pulled “away” from the water on the opposite side…then the earth would continue moving towards the moon. That is Isaac Newton’s First Law of Motion. The tidal acceleration at the centre of the Earth is most definitely *zero* and the water on the opposite side is most definitely pushed “away” from the Earth. That is why there is two high tides each day. Makes a lot more sense to me.
@@wavydaveyparker , I never said it was correct. I simply pointed out that a book on science gave an alternate explanation that was very easy to understand and made sense, because two bodies exert gravitational forces on each other.
It also explained the two high tides we have each day with one being a "higher" high tide versus the other.
It also highlights an issue with inaccurate science information being published, and not just in this book.
Here's an example: It is impossible for gravity to create a star by the current model of a collapsing nebula of hydrogen gas.
Gravity simply can't pull the gas anywhere near tightly enough to form a star. The heat would easily overcome gravity as cause the gas to stay dissipated. Ever opened a tank valve at 3,000 psi, and seen the incredible force that the gas has, as it escapes?
Charles Law precludes star formation from happening by gravitational collapse.
The gravitational force causing collapse can't get anywhere near the level necessary to complete the process. Eventually the heat would easily overcome gravity.
And yet, we still see this being taught as how stars are formed.
Then we have the issue of planet formation. That doesn't pass muster either, but I won't go into that.
My point is, even accepted science being taught at the highest levels, in books other than the one I mentioned are not always accurate, and yet, it is still being taught.
Looks like they teach from comic books as well.
I'm curious how you might explain star formation?
(Academics are aware of these issues, but continue to teach them, and we blindly accept them as fact.
Then, to make it worse, a "rescue device" is tossed out there, rather than simply scratch our heads, and say, "We honestly don't know".
One such rescue device is this: An exploding supernova caused gravitational waves that compacted the gas tightly enough to allow gravity to take over. A child could see through all the holes in that.)
@@wavydaveyparker ,
NATIONAL GEOGRAPHIC had this to say about how tides form.
***I AM NOT SAYING IT'S CORRECT; ONLY THAT THE INFORMATION IS OUT THERE***
"The tidal force exerted by the moon is strongest on the side of the Earth facing the moon. It is weakest on the side of the Earth facing the opposite direction. These differences in gravitational force allow the ocean to bulge outward in two places at the same time. One bulge occurs on the side of the Earth facing the moon. This is the moon’s direct tidal force pulling the ocean toward it. The other bulge occurs on the opposite side of the Earth. Here, the ocean bulges in the opposite direction of the moon, not toward it. The bulge may be understood as the moon’s tidal force pulling the planet (not the ocean) toward it."
education.nationalgeographic.org/resource/cause-effect-tides/
Idk. A course in GR might help you model this more accurately.
I had read a good explanation for tides before, but the video explained it beautifully and in more detail, particularly the tidal constituents and their relative timings.
This is why I pay an internet provider.
Also, seeing a totally unexpected glimpse (09:54) of my hometown in this video was a nice bonus.
Great Job, complete, clear and concise at the same time. Thank you !!
Great job for giving a 80% complete explanation for the marines tides, but as I'm picky, I'm missing the "jewel on top of the crow" which would make this video really outstanding: the explanation about amphidromic points and the influence of the Coriolis force on all this moving water! You did the same trick as those videos that present the two bulges and says "too complicated to explain".
sounds like we need to do a follow-up video! We always struggle with figuring out how much information is too much or too little. Thanks for the feedback!
@@Waterlustthanks for the great work you have done here in this video- just one request in your next video please keep the music down and your voice up so I can focus on the information better.
Thanks anyway.
@@sydanas7564 will do!
I grew up in Anchorage Alaska and they have the 4th biggest tidal change in the world and are number 1 for cities in the United States. Anchorage sits on a peninsula in Cook Inlet with Turnagain Arm to the south and Knik Arm to the north. The tidal change between high and low tide averages just around 30 feet and going up to over 33 feet for Anchorage and Turnagain Arm. Surfers and paddle boarders regularly ride the bore tides that occur when the tide is coming back in. They can ride the bore tide for miles if they’re lucky. But when the tide is low Turnagain Arm becomes a mudflat with just the river channels flowing through it. The mud is sticky and nasty and snags unsuspecting people in when they unknowingly walk on the mud. The extreme tides makes Turnagain Arm unusable for boats really because of its shallow depths.
Such an amazing part of the world! We have a video about the physics of tidal bores too that you might enjoy
I remember learning about this when I traveled to Alaska in the summer of 2022 for a vacation. We were on a train and traveling next to some of those mud flats and a tour guide was talking about it.
OMG - I spent 4 years in Alaska as a young kid(Elmendorf AFB) and always thought it was pronounced Ptarmigan after the fowl! Crazy. I guess if I had paid more attention to my Alaskan History, I would have known better. Thanks.
Fun fact: while mass is measured in kg in scientific units, weight is a force and is measured in newtons, named after that guy who watch an apple fall. There are just under ten newtons in the force exerted on a one kg mass (the exact number is equal too the acceleration of gravity).
That means that an apple typically weighs around one newton. Nice!
That's cool!
Another Fun fact: A one Kg apple would not weigh around around one Newton in space, because the apple would be weightless. Exactly like the astronauts on board the space station. Fortunately, their orbital motion (inertia) balances the gravitational attraction (gravity) of the earth. Nice!
@@wavydaveyparker almost... if you take into account microtides within any orbiting platform then the strictly weightless result only apple-ies of the centre of mass of the fruit lies on a two dimensional curved surface passing through the centre of gravity of the spacecraft.
I agree totally that anywhere in board it's going to be a long way short of the one newton I claimed.
almost… if you take into account the tides on an orbiting Earth platform then the strictly weightless result only apple-ies onto a three dimensional surface passing through the centre of the Earth.
Why do you think Newton asked himself the question, “Does the Moon also fall?”
I would give this a Two-Thumbs-Up. As said in other comments, it takes a complex subject and explains it so more of us laymen can understand it.
👍😉👍
Glad it was helpful! More marine science content like this coming. Stay tuned
One of the best science videos on RUclips. Informative, beautiful and entertaining!
Stoked you liked it! More marine science videos like this coming so stay tuned!
Waterlust crushed it! One of the best videos Ixve ever seen, in any subject. Not too long, not too short. Very well done. Take a victory lap!
Thanks so much, we try to find the right balance. Always a challenge!
Nailed it - best explanation of ocean tides I have ever heard.
hellz ya! Thanks Blake
This is outstanding! Would love to see more of these! I learned a lot!
Thanks so much. More coming! Stay tuned
@@Waterlust EINSTEIN IS UNCOVERED AND OUTSMARTED BY FRANK MARTIN DIMEGLIO:
WHAT IS E=MC2 is dimensionally consistent, AS TIME is NECESSARILY possible/potential AND actual ON/IN BALANCE; AS ELECTROMAGNETISM/energy is CLEARLY AND NECESSARILY proven to be gravity (ON/IN BALANCE); AS the rotation of WHAT IS THE MOON matches the revolution. Indeed, consider what is the man (AND THE EYE ON BALANCE) who IS standing on what is THE EARTH/ground; AS touch AND feeling BLEND; AS ELECTROMAGNETISM/energy is CLEARLY AND NECESSARILY proven to be gravity (ON/IN BALANCE). Indeed, WHAT IS GRAVITY is, ON BALANCE, an INTERACTION that cannot be shielded or blocked. GREAT. BALANCE AND completeness go hand in hand, AS it all CLEARLY makes perfect sense ON BALANCE. Magnificent.
By Frank Martin DiMeglio
The sun's tide-generating force is about half that of the moon. One half times one third is one sixth. Consider what is water. The density of what is the Sun is believed to be about one quarter of that of what is THE EARTH. The diameter of WHAT IS THE MOON is about one quarter of that of what is THE EARTH. The density of the human body is about the same as water. Lava is about three times as dense as water. Pure water is about half as dense as packed sand/wet packed sand. We can multiply one fourth times two thirds in order to ALSO get the surface gravity on the Moon in comparison with what is THE EARTH/ground. The gravity of the Sun upon the Moon is about TWICE that of what is THE EARTH. The lunar crust is about TWICE as thick on the far side of what is the Moon. Notice what is the TRANSLUCENT AND BLUE sky ON BALANCE. The maria (lunar “seas”) do occupy ONE THIRD of the visible near side of what is the Moon. One half times one third is one sixth. What is E=MC2 is taken directly from F=ma, AS TIME is NECESSARILY possible/potential AND actual ON/IN BALANCE; AS ELECTROMAGNETISM/energy is CLEARLY AND NECESSARILY proven to be gravity (ON/IN BALANCE); AS the rotation of WHAT IS THE MOON matches the revolution. Consider what is the orange AND setting Sun ON BALANCE. Consider what is THE EYE ON BALANCE. Consider what is the fully illuminated AND setting/WHITE MOON ON BALANCE !!! What is E=MC2 is dimensionally consistent. The land surface area of what is THE EARTH is 29 percent. This is EXACTLY between (ON BALANCE) what is one third AND what is one fourth. The maria occupy one sixth of what is the Moon. The BULK DENSITY of what is the Moon is comparable to that of (volcanic) basaltic lavas on what is THE EARTH/ground. Consider what are the tides. ONE HALF times one third is one sixth. ONE QUARTER times two thirds is one sixth. What is gravity is, ON BALANCE, an INTERACTION that cannot be shielded or blocked. CLEAR water comes from what is THE EYE (ON BALANCE). ON BALANCE, what is THE EARTH is ALSO BLUE !!! GREAT. BALANCE AND completeness go hand in hand. What is LAVA IS ORANGE, AND it is even blood red. Awesome. Yellow is the hottest color of lava. Blue is the hottest flame color. Note: Consider what is the blue flame. The lunar surface is chiefly composed of pumice. Volcanic ash is present as well. The topologic range (lowest to highest spots) on what is the Moon IS about THE SAME as that of THE EARTH (i.e., about 15 kilometers). This is the approximate distance from the very bottom of the Marianas trench to the top of the Himalayan mountains. Magnificent. The bottom line: What is gravity goes way beyond what Einstein tried to lay claim to (and to descriptively isolate). That is abundantly CLEAR. He never nearly understood what is TIME.
By Frank Martin DiMeglio
In understanding SPACE, what is gravity, TIME, AND time dilation (ON BALANCE), it is important is it to understand what is a BALANCED displacement of what is SPACE. ELECTROMAGNETISM/energy is gravity ON/IN BALANCE.
Consider what is E=MC2. TIME is NECESSARILY possible/potential AND actual ON/IN BALANCE. Consider TIME AND time dilation ON BALANCE. (c squared CLEARLY represents a dimension of SPACE ON BALANCE.) Indeed, the stars are POINTS in the night sky ON BALANCE. The rotation of WHAT IS THE MOON matches the revolution. Consider what is THE EYE, AND notice what is the TRANSLUCENT AND BLUE sky ON BALANCE. NOW, consider what is the BALANCED MIDDLE DISTANCE in/of SPACE. CLEARLY, BALANCED inertia/INERTIAL RESISTANCE is fundamental (ON BALANCE). “Mass"/ENERGY IS GRAVITY. ON BALANCE, consider what is the orange (AND setting) Sun. “Mass"/ENERGY involves BALANCED inertia/INERTIAL RESISTANCE consistent WITH/as what is BALANCED electromagnetic/gravitational force/ENERGY, AS ELECTROMAGNETISM/energy is CLEARLY AND NECESSARILY proven to be gravity (ON/IN BALANCE); AS gravity/acceleration involves BALANCED inertia/INERTIAL RESISTANCE (ON BALANCE) consistent WITH E=MC2, F=ma, TIME, AND time dilation ON BALANCE. This CLEARLY AND NECESSARILY represents, DESCRIBES, AND INVOLVES what is possible/potential AND actual ON/IN BALANCE, AS ELECTROMAGNETISM/energy is CLEARLY (AND NECESSARILY) proven to be gravity (ON/IN BALANCE). Notice what is the fully illuminated (AND setting/WHITE) MOON ON BALANCE. Great. TIME is NECESSARILY possible/potential AND actual ON/IN BALANCE. Indeed, inertia/INERTIAL RESISTANCE is proportional to (or BALANCED with/AS) GRAVITATIONAL force/ENERGY; AS ELECTROMAGNETISM/energy is CLEARLY AND NECESSARILY proven to be gravity (ON/IN BALANCE). This CLEARLY explains what is E=MC2 AND F=ma ON BALANCE, AS TIME is NECESSARILY possible/potential AND actual ON/IN BALANCE !! (Consider TIME AND time dilation ON BALANCE.) Great. Indeed, consider WHAT IS THE EARTH/ground ON BALANCE. I have mathematically proven why the rotation of WHAT IS THE MOON matches the revolution, AS ELECTROMAGNETISM/energy is CLEARLY (AND NECESSARILY) proven to be gravity (ON/IN BALANCE). Consider TIME AND time dilation ON BALANCE, AS the stars AND PLANETS are POINTS in the night sky ON BALANCE; AS c squared CLEARLY represents a dimension of SPACE ON BALANCE. (Consider what is THE EYE ON BALANCE.) I have mathematically proven what is the fourth dimension, AS ELECTROMAGNETISM/energy is CLEARLY AND NECESSARILY proven to be gravity (ON/IN BALANCE) !!! I have explained why what are OBJECTS may fall at the SAME RATE.
By Frank Martin DiMeglio
The ocean tide bulges don't actually line up perfectly with the moon, but are dragged forward by the rotation of the Earth. This misalignment of the tidal bulges is what permits the tides to slow the rotation of the Earth and accelerate the Moon to an increasingly higher orbit.
Thank you for this complete explanation of all the tides. Both lunar and solar. I realize their are more but knowing just those and how they interact satisfies my curiosity.
So glad you enjoyed it! Most of the significant tides on Earth can be explained with just the moon and sun, so you've got the important ones covered!
Best explanation I've heard ... will share this with many. I look forward to watching some of your other videos ... cheers
Excellent presentation! As a coastal engineer I’m familiar with tidal constituents and where they come from, but this is an unusually lucid explanation of this complex phenomenon which, as you said, many textbooks still get wrong. Next video, maybe you can tackle why referring to tsunamis as “tidal waves” is just wrong!
Right on! We call out the tsunami/tidal wave confusion in our video about tidal bores! ruclips.net/video/F-EoL4Jf7ug/видео.html
Wow, I finally get tides! Insane how other videos and explanations in my textbooks growing up skipped all this. Thanks a bunch!!
As a kid I'm the 1960's the tides were a huge part of my life, even in winter, we lived right on the coast of the northeast Atlantic, those deep green waters are in my blood.
What a wonderfully clear, interesting explanation of tides. I, too, was taught the over-simplified version of how the sun and moon cause the earth to bulge, but never why the OPPOSITE also bulges...only that it does. If they just would have mentioned Newton's discovery to us, it would have been easy to figure that out, and, I would have understood why the moons of gas giants have a hard time surviving. Now I understand! Thank you for that knowledge!!!
What a wonderfully clear and interesting comment. Yes, Newton firmly established that a common centre of gravity was a prerequisite for all celestial bodies in motion. This wobbly inertial movement is definitely the main cause behind the tides, although it still required the insights of Laplace to complete the picture. Thanks
What's amazing is that something as ancient, familiar and well-studied as the tides, still have more that can be learned about them.
I think this video came up in my feed because i have been researching the size of ancient tides going back to when the moon originally formed. I saw a post on Quora complete with math that suggested ancient tides were over a kilometer high. Since its formation, the moon has been slowly spiralling outward from the Earth and slowing its primary's rotation in the process. Not only did Earth have tsunamis of water sloshing around every few hours but likely also tides of lava oozing from the partially cooled and tortured crust. Would love to see a video about Ancient Tides of the Early Earth. We look at the moon as a beautiful and peaceful symbol of serenity but in the early years of the planet, it was more like a blender. A blender powered by a chainsaw.
This is a fascinating subject!
In an above comment I did a quick calculation and estimated the Roche limit is about 15,000 miles, which is where the Moon formed. Perhaps 16,000 miles.
So, that's 4 times the Earth's radius, so orbital period would be 4 to the 3/2 power, which is 4 times 1.414, which is about 5.6 times greater than the ISS's 1.5 hour orbit, so about 8.5 hours.
Oh, crud. The Earth was rotating about once every 4 hours. Shoot. Well, I guess the tidal "wave" would come by about twice every 4 hours.
Dang, that's fast! At the equator, that's 25,000 miles per 2 hours, about 12,500 miles per bour.!
Finally, an easy to understand explanation
This is the best video, and first understandable explanation I have found so far. Kudos!
Very entertaining! However, why do you only consider the ‘tidal force’ in linear ‘free-fall’ motion? We get the exact same results when we experience a ‘tidal force’ in orbital ‘free-fall’ motion around a common centre of mass. And its certainly safer, more realistic and adheres to the accepted laws of Motion, which were laid out by that Newton guy you mentioned, and we wouldn’t have to contend with any messy unavoidable collisions? Which wouldn’t be very environmentally sound for any of us! Anyway, I enjoyed the presentation and congratulations. Take care.
We present the context of linear acceleration as it's far simpler to illustrate to a layperson. The stretching effect caused by gravitational fields is the same whether an object is accelerating through them linearly or centripetally.
@@Waterlust That’s interesting and thanks for bothering to reply, it’s much appreciated. Maybe it’s just me, but I distinctly got the impression from your beautifully animated introduction, that you wanted to get away from the usual, boring, monotone, layperson speak, where lesser competent content creators, unlike yourselves, usually say, “there is a bulge on the far side and don’t ask why? It’s just there???” I honestly think your superbly produced production deserved better…than to just say, the Earth accelerates towards the Moon leaving water behind. It’s just a shame, when you were so close to providing the correct answer for, “why tides really happen?”
The ‘squeezing’ effect on oceans - _and it’s not a ‘stretching’ effect, because water cannot be stretched_ - caused by gravitational fields is not the same whether an object is accelerating through them linearly or centripetally.
If it’s linearly, then the end result is destruction and we get rapidly increasing tides.
If it’s centripetally then, the earth and moon are in a balanced orbital motion around a barycentre and inertia has to be recognised, and then we can all gratefully, continue to correctly predict and experience our wonderful tidal systems every single day.
However, who am I to talk? … Just someone who was taught Physics correctly at school I guess, by an extremely good teacher - but who cares! Thanks for the chat.
@@wavydaveyparker Interesting stuff! We think there can be legitimate debate regarding which term, “squeeze” or “stretch” should be used…but the overall message is that the gradient in gravitational fields, and the motion it produces, produces deformation of celestial bodies, including the tides.
The idea of using the centrifugal “force” to justify the far side deformation is interesting and we’ve seen it widely used. Our problem with it is that it's a little misleading and in some cases insufficient. Centrifugal forces are “apparent forces”, they don’t explain why tidal force deformation happens in linear acceleration cases (as modeled in Matlab in the video), and why tidal force deformation is always symmetric, regardless of the celestial body or its orbit.
An explanation based solely on gravitational fields doesn’t seem to have these problems, while also preserving the physics of inertia and the apparent centrifugal forces of orbits. The idea that the planet accelerates away from water on the far side is equivalent to saying the water experiences a centrifugal force due to the orbit. It's just presenting it in a different way.
That’s at least our perspective on it….it’s a fascinating subject and we enjoy thought provoking discussing about it! Thanks for participating
@@Waterlust And I wholeheartedly agree, the Astronomical part of the discussion is a fascinating subject and I thank you for engaging in this thought provoking friendly chat. I certainly don’t want our conversation to detract from your otherwise excellent video, which I still think is very interesting and well made. And, at least you didn’t bring up the crazy idea of planets performing ridiculous start-stop motions and partial bulge filling, which I’m sure you’d agree is totally misleading. _I did make a daft little video about that if you’re interested? 😄 any kind support is always welcome!_ …
Anyway, here’s the thing! Your first sentence summed up the confusion most people face when thinking about gravity and orbits…
_“The overall message is that the gradient in gravitational fields, and the motion it produces, produces deformation of celestial bodies, including the tides.”_
The gradient in gravitational fields does produce deformation of celestial bodies in the form of tides. However, they have nothing to do with the actual motion of planets, that is the sole domain of inertia. The planets don’t move because of gravity, they move because they initially had inertia, and wish to continue in there straight line paths forever. It’s only when gravity gets involved that there motion is shaped, into what we perceive as orbits in a curved space.
Now, I don’t want to get into ‘apparent’ forces and reference frames here, because I’ve been over that a jizillion times!!…despite to say, that gravity itself can also be considered as a ‘fictitious’ force. So, instead I’ll finish with something you might like to consider if you decide to produce a possible follow up video, because this is where you came so agonisingly close to being right on point!
Stick with the concept of ‘free-fall’ … which you alluded to in your video. What Newton concluded and what Professor Brian Greene demonstrated in an excellent video on Relativity, was that when a celestial body is in orbit around a barycentre, it experiences a zero ‘net’ acceleration at its centre. The tidal force is caused from this point outwards. Tides are actually formed by the buildup of lateral, hydrostatic pressure in the oceans on either side…and, when I say, ‘side’ I mean near and far.
However, that just my considered opinion, based on the scientific evidence provided by my teachers, but what do they know! Nothing!! … That’s what?
Kind regards, wavy.
@@wavydaveyparker Interesting points, though the inertia mechanism wouldn't result in tidal bulges in linearly accelerating celestial bodies, it would only apply when there is an orbit. Though, do linearly accelerating celestial bodies have tidal bulges?…we’re not sure there are any documented cases of that. We also wonder how the bulges end up being symmetrical. The inertia argument only applies to the bulge on the far side, so what about the close side? The explanations we've seen say that the bulge on the close side is caused by gravitational attraction, while the far side is inertia, and yet somehow...they are both the same magnitude. We haven’t done the math, but that seems a little fishy.
One idea we had is to simulate a cluster of particles in the way we did in the video with Matlab. Instead of using the universal law of gravitation to calculate all the forces, we could create a virtual world where the gravitational force between objects is not distance dependent (in other words, the force of gravity = G*M1*M2). In that fake world, orbits could still be maintained, and we could model a cluster of particles orbiting another celestial body. If the cluster is deformed in the way we see in real life, it would support the idea that inertia is the dominant mechanism. But If it isn’t, it would mean that the gradient of gravity is responsible.
We don’t think it would be that tough to model….maybe a project for next week!
I never knew the opposite tide was a problematic issue - even 30 years ago at school we were taught the concept of the earth moving toward the moon and leaving the bulge on the far side 🤷♂️
Indeed, this has become a problem with the rise of 'internet opinions', where people proclaim them, without really listening to those who disagree.
Many, with limited knowledge of physics, have found an alternative way to explain the 'far side tide', using an explanation based on inertial forces. This can indeed be done correctly, although most of them do not work it out correctly. But, having gotten wind of this method, many have concluded that any explanation, without Centrifugal Force, must be wrong.
If they took time to listen and consider they would eventually find out that both methods are the exact same thing, just regarded in different reference frames.
Thank you so much, excellent video.
finally a logical and simple explanation that matches actual observation of the tides, the popular explanations never sat ok with me because they never did.
Great work, I'm a kayak instructor and the over-simplified "two bulges" diagram is such a massive sticking point when teaching tide theory. Thanks for going the extra mile, will definitely be sharing this with students.
Glad you found it helpful. More marine science videos like this coming, stay tuned!
I wish you wouldn’t Mr Waters, because this isn’t how the tidal waters work. Please stick with Newton’s Equilibrium Theory first, and then move onto the Dynamic Theory, which was discovered by Euler and Laplace.
The best explanation of tides I have seen so far on RUclips.
I wish you had added some additional examples of where and how resonance results in high tides. For example Incheon, South Korea has 34 foot tides but the coastline does not seem to resemble the Bay of Fundy.
South Korea is a developed country, and as such it uses metric, so that would be a 10m tide, not 34 foot. There's only 3 undeveloped countries still using imperial units.
Best explanation ever regarding the tides. Thank you.
Right on! Glad you found it helpful
Awesome video! This is the BEST explanation of tides👍👍
Very clear explanation, i love the part where you split the planet in 4, a very nice way to move toward a gravitational field notion. I will sure reuse it!
My understanding has always be that although the maximum of the gravitation field is just 'below' the moon (on the moon-earth axis, moon side) as you explain and draw, the inertia of a body of water makes it that the actual bulge is 'late', by an amount that from memory is close to 90° so that at the end, the bulge of water is about opposite to where it is classically drawn.
As it makes the explanation a bit more confusing, i tend to just add this notion after where your nice video brings us.
Super interesting, we hadn't heard about an offset between the tidal bulges and the earth-moon line caused by inertia/earth's rotation. We're not sure that actually happens, we will have to read up more on it! One point we'd bring up is that the concept of the tidal bulges is somewhat simplified since the planet isn't entirely covered in water (land affects things), and there are many "bulges" in different locations simultaneously. The classic example of the moon bulges is specific to the M2. One way we like to look at it, is that each "bulge" is a wave, and each wave is traveling around the planet. Sometimes multiple waves hit the same place at the same time (eg: spring tides), and the location of land masses can interrupt how fast the waves make their way around the planet. NOAA has a nice discussion about this at the link below...though they do suggest that if the earth were entirely covered in water, the bulges would align with the axis of the respective celestial bodies causing them. Though at the same time, just because NOAA says it, doesn't mean it's necessarily true... oceanservice.noaa.gov/facts/moon-tide.html
@@Waterlust I've not been able to find the book where i think i read the 'around 90° offset' (cause it was a borrowed paper one), only its reference so far. The wikipedia article hints at this offset by saying 'The moment of highest tide is not necessarily when the Moon is nearest to zenith or nadir' but is non commital on how much of an offset we could expect in general. The Bathymetry chapter (en.wikipedia.org/wiki/Tide#Bathymetry) gives an example of 2 and a half hour offset for Norfolk, Virginia, so more like 40° in this case.
I totally agree that the coastal effect have a lot more impact (including in delaying the tidal wave), but they are also a lot more difficult to explain in simple terms. M2 bulge is the first thing to explain, but i'm just worried that drawing it aligned with the bulge in the gravity field is giving a too simple but too inaccurate result.
The tidal bulge does preceed the Moon and accelerates it tangentially, which makes it move away from the Earth and slow down.
The tidal bulge also slows down the Earth's daily rotation, because the Moon is pulling back on the Earth as well.
From old memory, the Earth started out with about a 4 hour day and the Moon's orbit was about 6 hours. But, because the tidal bulge preceeds the Moon by a few degrees (definitely not 90, but more like the 30 mentioned in a reply) the Moon is accelerated just like when your hand moves in a circle ahead of the rock in your sling, as you accelerate a stone in order to slay Goliath.
The leather string becomes more taught and stretches as the stone speeds up and centripetal forces increase.
So, the Moon moves away from the Earth because as an orbiting object accelerates, it doesn't speed up, but rather increases in orbital radius, and slows down.
Right now the Moon is retreating from the Earth about 1.5 inches a year as I recall. It might be 2 cm, which is 4/5ths of an inch. Might want to check that. Anyways, it's about the speed of continental drift: slow.
The Moon is currently moving just over 2000 mph, maybe 2200. But it varies a lot thanks to the very elliptical orbit.
When the Moon first formed, and had a 6 hour orbit (just outside the Roche limit you talked about) it's velocity was a lot closer to the International Space Station's 17,500 mph.
Equations exist for determining the Roche limit, and as I recall they are typically a ratio of radii, adjusted for density. Since the Moon's density is half of the Earth's, and it's radius is 3.666 times less, then the Roche limit is... guessing around 15,000 miles. That's a lot closer than the current 239,000 mile average.
If my guess is correct, and orbital radius started out at 15,000 miles, then orbital period was about 5 times longer than the ISS, so about 7.5 hours.
Tides were insaely high and very fast, and probably eroded entire continents, if there were any after the crazy impact than formed the Moon.
What a fun, engaging, and educational video!! Awesome job team!
Awww thanks Jake!!
Seems to have made the topic unnecessarily complicated. I still don't know how the tides work despite spending a great amount of time at the seaside.
This is the future of education. You need to start a home school curriculum with these types of videos. Great job!
Very good explanation. Now, can you explain why the Moon is slowly drifting away from us instead of spiraling in towards us?
will have to make a separate video about that!
Why this video has so little likes is beyond me. Great work.
the algorithm hasn't graced us with its attention yet
If you want more likes, turn down the background audio to a minimum of a third of the speakers volume. Sounds more like a music video instead of a very interesting and educational video. That's just my opinion but I have a feeling much of your viewing audience would agree
Fantastic video. Thank you for making such educational content!
Our pleasure Susan! Our hope with these videos is to create material that is both entertaining and educational!
This is a brilliant explanation!!
On fact you have left out is the drag or lag factor. Spring tide low is always at about 9am in the morning where I am. If you look at your illustrations of the bulge this should be at 6am when the sun and moon is rising but it takes place about 3hrs later.
Great point!
So are the tides dependent on the fact that the moon orbits the earth? If the moon where to suddenly be in geosynchronous orbit, would we then only experience a consistent high tide on the same side of the planet, as the water that needed to "catch up" would effectively eventually catch up to the rest of the water being pulled by the moon?
We would say the tides are dependent on the gravitational fields that nearby massive bodies create (the moon, sun, etc..) and that the two bulges should occur regardless of the specific type of orbit. If a planet is accelerating through another massive body’s gravitational field, it will experience tidal forces.
@@Waterlust But that's what I mean... if the moon stopped orbiting the earth and stayed in the exact spot relative to the earth, the earth is no longer accelerating through the moon's gravitational field.. it is just sitting in it.. Would we still have the tides (ignoring the sun's impact, etc)? Perhaps I misunderstood this all...
@@paulslund1 Understanding your question a bit more now.... If the Earth were in synchronous orbit with respect to the moon, then the same locations on Earth would always be facing the moon, and the tidal bulges the Moon’s gravitational field creates would stay in the same place. This would result in permanently high tides and low tides that wouldn’t change in time.
Interestingly, this already is happening on the moon! The moon is in synchronous orbit with respect to the Earth, so the same side of the moon always faces the earth. This causes the tidal bulges on the moon to be permanently oriented, with the side facing Earth and facing away from Earth being slightly bulged out.
@@Waterlust Thank you again! So I guess I was pretty close with my assumption.. I thought that in the case of a permanent high tide/low tide scenario, that the high tide would only be on the side facing the moon, and the low tide on the opposite side (as that water "caught up" with the rest of the water.. but your description of the bulges on both sides of the moon indicates this isn't so....
@@paulslund1 yes, because it’s still in a constant state of acceleration, the two bulges would remain. The bulges would only go away if the Earth stopped accelerating towards the moon. Great question!
90% of commenters who wrote something like "the best explanation of tides I ever heard" did not understand the explanation but were persuaded or manipulated by the video into the sense of understanding. They think they understand but they do not. They will realize they do not understand once they try to explain tides to a third person.
Hmmm, that's an interesting take. Personally, we find that using the linear acceleration model to illustrate the deformation of planets accelerating in gravitational fields is quite easy to explain to people. We just did it the other day at breakfast using salt and pepper shakers to illustrate, and the person we showed understood it immediately 🤷♀
Brilliantly explained
excellent video. Great explanation of a complex topic.
I liked the way you explained how the high tide travels overland from the east coast of America to the Pacific coast!!! Oh, wait, it doesn't. In fact in the North Pacific the tide sloshes back and forth, first going eastward to the west coast of USA then back westward to Japan. The 'bulge' under the Moon is not how the tides work.
The tidal bulges caused by nearby celestial bodies are observable phenomenon, and not only applies to oceans, but other fluids, planetary rings, and even the shape of entire planets. What you’re describing is how the ocean tidal wave propagates around our planet, which you are correct, is highly influenced by bathymetry. But the underlying force driving all of this are the bulges created by gravitational fields from nearby celestial bodies. We have a new video coming out next week that looks at tidal bores and explores the concept of a “tidal wave” in greater detail. Stay tuned!
Here's that new video we mentioned before that discusses the "wave" like nature of tidal waves. ruclips.net/video/F-EoL4Jf7ug/видео.html
A rather poor explanation of the tide on the opposite side to the moon. Both Earth and Moon rotate about the barycentre of the Earth-Moon system. This point is not at the centre of the Earth, rather nearer to the side facing the Moon, about 4700 km from the centre of the Earth. The far side of the earth is then rotating around the barycentre, which explains the lower tides on that side.
I live near the bay of Fundy! Hopewell rocks is amazing, you can literally walk on the sea floor.
The Bay Of Fundy is incredible! If you haven't already seen it, you'll like the video we made on Tidal Bores that includes surfing the bore in Moncton! ruclips.net/video/F-EoL4Jf7ug/видео.html
I have no interest in tidal forces, but holy crap I couldn’t stop watching this video.
Awesome! You gotta admit though, the tides are pretty cool eh?
Gosh I could live without the unnecessary background music.
This is incorrect. Water dropping in a vacuum will assume a spherical shape not an elongated 'double bulge'. Why? because the two tides are not explained by linear acceleration they are only explained by circular acceleration i.e. centrifugal forces. Swing the Earth in a circle around the Moon and the water bulges away from the Moon, the Moon's gravity makes the water bulge towards the Moon. S0, the Earth rotates around the Moon and the Moon rotates around the Earth. both around a point called the Bari centre. This is the cause of the two tides.
You are absolutely correct, but unfortunately you're slightly late to the party, because the people behind this don't actually care about teaching physics correctly, and sadly enjoy continuing the spread of misinformation about tides, and becoming popular in the process. However, I applaud your effort and commitment to seeking and spreading the truth about tidal formation. Well done.
the view count analogy is incredible... perfectly described in the first minute.
exceptional essay. excellent work.
With high school education, that was a beautiful explanation,thank you dearly.
Glad you enjoyed it! More videos like this coming soon about other cool ocean science topics
I wonder how many have considered a different point of view, take for instance, in an "enclosed cosmology", you would have not "magical" force of gravity, but simply a pressure differential. It could be that simple, as is water in large volume conforming to its container and seeking it own level at rest.
it is totally valid to point out that the theory of gravity is just that, a theory. So far it's the best we have, but there are still many mysteries in the universe!
This does not align with my observations. A number of years ago I was fishing in Martinez Ca., about 25 miles up the California delta from the Pacific shore. Coincidentally there was a lunar eclipse right at midnight, putting the moon directly over my head and the sun directly under my feet. Instead of an unusually high tide as pictured in your animations, I observed just the opposite- the lowest tide I have ever seen in my life. It must have been -8 feet! So even this lesson, while well made must be in error. Martinez tides lag San Francisco by only an hour and a half.
I agree with you.
I think the Moon's relationship with the tides is more independent or more complex. U feel sure they're related as everything is, but the tides and phases if the Moon don't correlate as they say.
I wonder if the tides have more to do with the underground pumping that results in mountain springs feeding lakes and waterfalls at 12,000 ft+ as in Titicaca in Bolivia.
Interesting thoughts. You know there may be something to that. @@Myfriendwaits
The problem with the Waterlust explanation is that it (like almost all other explanations) assumes that the oceans take the 'two bulges' shape. In that case you should, indeed, have experienced a high springtide on that particular night.
The tricky part is that the gravitational forces do, indeed, have that 'two bulges' shape, but that the earth's oceans react very differently to what you would expect. In short; only 'partial bulges' manage to form in the southern oceans of our planet. From there, portions of their energy transfer northward in the form of long-period shallow waves, subject to the hydrodynamics of the ocean basins, coriolis force and atmospheric conditions. Just google 'global tides animation' and watch them go. The portions which reach the shore around San Francisco have been travelling for more than a day. This is why the highest spring tide levels typically occur there one or two days after the full moon or the new moon.
But the most important thing to realize is that they are a secundary, induced effect, which, at the time of observation, is not directly being caused by any gravitational influence from the moon above your head. That took place, more than a day ago, far away.
Perhaps then, two nights after my pier fishing night there may have been an even greater effect. @@TribusMontibus
Love how he mocks textbooks about the moons' gravity affecting tidal waves, then proceeds to say the exact same thing.
Sounds like you didn’t watch the video 🙄
that was sooo helpful thank you!
The bulge is a result of spinning faster at the equator than the poles
This is incorrect. That would result in high tides around the equator all the time, which is not the case.
@@Waterlust speed at equator is
x miles for 24 hours vs
speed at the pole y when y is z miles=o>
Just the difference in speeds and distances is almost infinite!
The bulge is the pull of gravity vs speed of rotation!
It doesn’t mean that the tides, gravity of moon, are disturbed by the rotation or speed!
It’s all relative! E=mc2!
That is correct.
The Earth orbits, revolves, translates around the barycentre. Each point of mass on Earth, maps out a circle of equal radius _(4670km)_ as it orbits. The centrifugal force is equal across the whole earth. And when you subtract that (rω² ~ 3.3x10^-5 m/s²) from the gravitational attraction, which diminishes by the inverse square, and factor in the earth’s own gravitation. You get an acceleration of +/- one ten millionth of a (g) on either side and *zero* at the centre, which is due to the *free-fall* motion experienced by all Planetary bodies, which are in orbital motion in the solar system.
Hence, we get two tides a day as the Earth rotates on its axis, but we have to resolve those acceleration vectors first. Good luck
@@wavydaveyparker another physicist perhaps! I studied at FIT, it was a NASA supplier of professors and teachers. I’m retired now but the bulge is only explained with physics! The centrifugal forces of the earth and the magnetic forces, not gravity, explains the odd shaped oval that is our planet. The bulge is easier to understand if you can understand the formation of the earth and those forces that formed the bulge! During human history, which is very short, the bulge has always been there! Because it’s the shape of the planet, what forces took charge of shaping and when did the bulge happen?
@@Michael-zs6gt Thank you so much for the kind reply sir, I never actually reached the heady heights of NASA, but my Professor at University was an extremely good teacher and a thoroughly engaging individual. I totally agree, the tides can only be explained with Physics, and it’s just a shame the team behind this over-simplified mistake never met my teachers, because their explanation would have made them weep. Take care.
Something isn't adding up here!!!
In reality the tide is *not* highest when the moon is directly overhead.
On a full or new moon, high tide seems to occur at 3 or 4am and 3 or 4pm... lagging by 4 hours after the moon has been overhead.
Check it out yourself with a local tide table.
This doesn't fit with your drawing or explaination. 🤔
Great observations! The specific locations of the bulges don't always align with the overhead position of the moon (or sun). This happens because the tidal wave (the bulges) moves at different rates as it travels around the Earth. The shape of each specific ocean, coastline etc...will affect this. We left finer details like this out because we didn't want to overload viewers with too much information.
Thank you for the insights.
Thank you very much for the video. I felt like a piece of a puzzle clicked to it's place in my head. And this is very satisfying.💡
I think what irks me about this incorrect treatment of tides is that it undoes the good work we try to accomplish in introductory physics courses. We emphasise the correct application of Newton's laws of motion. First we tell the students to identify the body in question, the body to which we will apply Newton's law. Newton’s first law tells us that an object will continue to move on a straight line at a constant speed, unless it’s acted on by an external force. And then it will continue to accelerate in the said direction and not stop. This video is NOT how the tides REALLY work?
What's missing in their explanation ?
@@SebastianBode Centrifugal force is what is missing in this explanation...
What the hell are you talking about. All those smarts and can't get your point across.
@SebastianBode frame of reference is what is missing. The earth is rotating on its axis while orbiting the sun which is orbiting the galactic center. As the earth travels around the sun, the surface water is accelerated east and then west. Water has less mass than rock so it gets accelerated into a higher orbit/radius from the Earth's center. Newton's Laws of Motion accurately describes the Earth's tides. Add in Kepler's laws of motion, the closer to the sun, the greater the acceleration, and you have the king tide occurring the first of the year as the planet makes it closet approach to the sun. But it's on the back side of the planet as this is where the greatest amount of acceleration is taking place.
Galileo theorized that the tides are caused by the earth's motion in space.
GRACE mapped the Earth's wobble and attributed it to redistributed of ground water along the 45 degree latitude. This is where the most acceleration takes place and would have the most impact on the earths rotation.
Gravitational attraction has been disproven. Only diehard relativists are still preaching it because it invalidates their beliefs.
That's your opinion of it ..
Unfortunately, this is not how the tides really work. This video does a nice job of describing the forcing functions, but not the result. We really do not get two tidal bulges. Instead we have a number of amphidromic points in the oceans, and the tides form circular waves around these points. These amphidromic points are points where the tidal range is effectively zero.
While there certainly are finer details related to the shape, position, and motion of Earth’s tidal waves (e.g - the bulges), this video was designed to explain the overarching principles that create them. We may make future videos that get into more of these details down the road, but omitted them from this as we felt it would lead to information overload. We already felt we were pushing our luck with a video over 10 minutes long, but glad to hear people are interested in getting more information.
@@Waterlust the differences I'm describing are not finer details. The actual shape is not two bulges - even though the forcing function is.
If you described this as a description of the "principles that create them" it would be accurate. But in the video you describe the shape of the resulting tides.
@@Rick_Cavallaro We respectfully disagree, but appreciate the feedback!
@@Waterlust we can certainly agree to disagree, but I'd like to know where we disagree. Do we disagree as to the intent of the video? That's fine. But are you saying that fundamentally the tides really do form two bulges (and I don't mean anything terribly precise by that - the circular waves in the ocean are just like those generated by swirling a cup of coffee by moving it in small circles). I maintain that that fundamentally describes the "shape" of the tides, while the two bulges very nicely describes the forcing function.
@@Rick_Cavallarogo make your own video... show us all how it really happens.... otherwise shut the fark up... seems you're one of those types that always has to have the last word...
Clearest explanation I have ever heard! 🙏🏽🙏🏽🙏🏽☀️☀️☀️
Great video! One minor comment. The time for a shallow water wave to traverse the Bay of Fundy (and back) is much less than 12.42 hours. The resonance is with the entire Gulf of Maine.
Great point!
Your explanation of what causes the tides is WRONG. The high tide opposite the Moon is caused by centrifugal force due to the Earth rotating around the Earth/Moon barycenter, which is 1707 km below the surface of the Earth directly under the Moon (Earth's radius is 6378 km), not as you say since the far side of the Earth is farther from the Moon it is accelerating toward the Moon slower. That's WRONG.
No, the centrifugal force explanation is what is actually wrong. "Centrifugal force" is a fiction that can be useful to describe motion in rotating frames of reference, but has no actual explanatory power.
No, the gravitational force explanation is what is actually wrong. "Gravitational Force" is a fiction that can be useful to describe the motion around a barycentre, in a non-inertial frame of reference, but has no actual explanatory power. The two work in combination, as is explained by the National Oceanic and Atmospheric Association.
No, this is NOT how the tides really work. This video perpetuates the fallacy that the tides are directly raised by the Moon’s gravity. They are not. The gravitational force caused by the Moon at Earth’s surface is ten billion times smaller than Earth’s surface gravity. It is impossible to lift anything with such a force differential. To lift something requires a force greater than that body’s weight. Newton realised this and was unable to correctly explain the tides.
The true effect is much more subtle and is not what is claimed here in this video. It took the great mind of Euler, and subsequent work by Laplace, to explain the tides, and Laplace’s Tidal Equations are still in use today. These equations correctly treat the vertical (axial) components of the Moon’s gravity at the surface of the Earth as zero because they are swamped by Earth’s surface gravity. It is the off-axis horizontal components of the Moon’s field that create the tidal bulges. These are tractive, squeezing forces, and although they are tiny, they act in Earth’s horizontal plane and are therefore not overwhelmed by its surface gravity because they are at right angles to it. They are also, crucially, cumulative and above all, convergent. This is sufficient over thousands of square miles of ocean, to raise tides of a few metres in height.
One way to visualise these tractive forces is to consider the direction of the Moon’s gravitational field at various points on the Earth’s surface. Only at the exact sub-lunar and antipodal points is the field purely perpendicular to Earth’s surface. Everywhere else the field has to ‘lean over a bit’ in order to poin at the Moon and this leads to the tractive components in the local horizontal plane. This effect arises because of the key reason that the Earth presents a large extended target to the Moon’s very weak gravity. Most gravitational bodies can be reduced to point-like sources and in nearly all cases this is sufficiently accurate to provide sufficient modelling. But the Earth and Moon are so close that the Earth subtends a large angular diameter when seen from the Moon and THIS is the underlying cause of the tides.
The second or antipodal tidal bulge is correctly explained by this model and this model alone. In systems where the vertical components of the interacting bodies is dominant, a Roche Lobe is formed and this is a single peaked distortion as is found in close binary stars. The Laplace model of the tides correctly predicts domed or flat-topped tidal bulges because at the sub-lunar and antipodal points where the tractive forces converge, the tractive components fall to zero.
To summarise, the tides arise due to tiny but convergent and cumulative forces that squeeze the oceans into bulges like squeezing a balloon. These forces in turn arise because the Earth presents an extended target when seen from the Moon.
We think you missed the message of the video. We’re not saying that gravitational forces “lift” water to create a bulge. In fact, we specifically describe how that line of thinking contradicts the presence of a second high tide on the side of Earth opposite the moon (and sun).
The message of this video is that the shape of gravitational fields (as described by Newton’s law of universal gravitation) and how matter accelerates when exposed to them (Newton’s second law), explain the fundamental origin of the tides. While the works of Euler, Laplace and others can be helpful in understanding some of the finer details, in our opinion they aren’t required in a basic explanation.
@@Waterlust I don’t think I ‘missed the message of the video’ at all. It is misleading because it completely overlooks the key subtleties that give rise to the tides, subtleties that eluded Newton, and which we have now understood for about 250 years. Far from just filling in ‘the finer details’, it is only the Euler-Laplace model that correctly explains the tides. Your Newtonian explanation is simply wrong. You split the Earth up into four and then many separately gravitating bodies. This produces a Roche Lobe which is not how Earth’s tides arise. Your model would apply to everything on the Earth that has mass, not just the seawater, and so does not explain the rising and falling of the oceans. Newton’s Law of Universal Gravitation is inadequate to explain the tides and the great man himself knew this. Your video only quotes Newtonian mechanics so, too, is inadequate. Many non-scientists see through the explanation presented here and query the presence of the second or antipodal tidal bulge which cannot be explained by Newton’s Laws alone.
Wrong! Not only does the Moon's gravity raise the water, it also raises the surface of the Earth in a small "earth tide". We have to apply a correction for this in geophysical gravity observations.
@@Waterlust Newton’s Law of Gravitation does *not* describe the shape of gravitational fields, it only tells us the strength of gravitational attraction. And Gravity is *not* responsible for the Motion of celestial bodies. Remove the gravity, and the planets will still move with a straight line motion, *(Newton’s First Law of Motion).* I thought I’d explained that to you ages ago, but you obviously wasn’t listening. Unfortunately, your video has now attracted some attention and both of the commentators here are right. Your video is misleading, but who really cares, as long as you get the applause.
@@karhukivi No, not wrong at all. I can assure you that Euler and Laplace got it right.
very very well explained, best Ive seen yet and now I get it, thank you!!
Added fun fact: The ocean's friction delays the tides slightly, which gradually slows the Earth's rotation, while accelerating the moon enlarging it's orbit. en.wikipedia.org/wiki/Tidal_acceleration
"Really"? This is just another incomplete take on tides. Centrifugal forces play a relevant role here.
When describing CENTRIPETAL force, which is real, then the imaginary CENTRIFUGAL force is taken care of.
@@MultiPleaser No. When considering a rotating frame of reference (which is the easiest way to figure out tides) then centrifugal force is needed to describe the dynamics of all objects whether they experience a centripetal force or not. Calling it "imaginary" is also besides the point. Gravitation is also not a "real" force but it would be silly to use general relativity in this context. Just do the math an see for yourself. Determine the common center of gravity of earth and moon, calculate the difference in centrifugal acceleration (even if you feel dirty doing it) and compare with the difference of the moon's gravity. It's not difficult.
Too many people think the ocean is being pulled away from the Earth by centrifugal force. That's too confusing and is definitely not what's happening.
Imagine that Earth traveling in a straight line with no Moon or Sun.
Then suddenly there's the Moon at 239,000 miles.
The Earth and oceans will both be pulled towards the Moon and start traveling in a circle.
Because of "tidal forces" the Earth and oceans are stretched into a gnocchi shape, as opposed to being "spaghettified" like when orbiting a black hole.
@MultiPleaser "Too many people think the ocean is being pulled away from the Earth by centrifugal force." Citation needed. What do you find confusing about this?
But, if you really dislike this concept so much, you can, of course, avoid it. Let's ignore the day-night rotation and consider the points of high water on the axis through the respective center of moon and earth. These points move on circles with different radii but with the same angular velocity around the common center of gravity of moon and earth. Therefore, they have to experience different centripetal (yeah) forces. The difference of the two centripetal forces cannot be accounted for by the difference in attraction of the moon (Again, can easily be checked by doing the calculations.). So they have to be produced by additional height of the tidal bulges.
Can we avoid the Italian food names and use "ellipsoid" instead?
There is no tide on Earth
Tides are long waves across the oceans. They are caused by the gravitational force exerted on the earth by the moon and to a lesser extent by the sun. Wiki.
In fact, tides are an artifact of the up and down movement of coastlines in a stable ocean, caused by thermal expansion of the earth's crust due to sunlight moving westward.
Some coasts have no tides, some have only one tide, some have two tides, and some have four tides per day. Tides vary in height from 0 feet to 50 feet and move at different speeds and in different directions.
It is impossible for the moon's gravity to cause tides. Do you agree?
An article that proves all scientists wrong about tides
www.noaa.gov/ocean/fundy-max
The Bay of Fundy is 91 miles long and 30 miles wide inland in an east-west direction.
Thermal expansion of the earth's crust moves the coastline across the leveled ocean, creating the illusion that sea level is rising and falling with the tides.
This article and image shows that the high tide on the west side of the Bay of Fundy is 20 feet and the high tide on the east side is 50 feet at the same time.
This fact proves that the tides in the Bay of Fundy are an illusion of the shoreline moving in the leveled ocean caused by thermal expansion of the earth's crust. It is clear that the eastern side of the Bay of Fundy is more curved than the western side during the thermal expansion.
I learnt something new today! Thanks.
Beautiful thanks, I wish I could explain things with such elegance.
Thanks so much!
Wonderful explanation. Thank you.
Wow this was an amazing video! Thank you for sharing ❤
Nicely done, thanks.
I'm a diver and this was a phenomenal video
I had literally never heard your first, “ simplified common” explanation of tides, but I watched anyway.
The explanation in this video was really good!
Very good explanation! Congratulations!
That's a great explanation, thank you.
Lovely graphics, but no mention of centrifugal effects on tides
I didn't expect to be so wonderstruck. Good Stuff!
With all that accelerating you think we would have run into something by now. Yup, I have no idea whats going on, it works and I go fishing. Good video.
Great video. Very well done❤
This was an excellent video!
This was really good. I watch lots of these kinds of videos, but some leave out certain things that, while they may be obvious to the expert, are not so to the layman. I think you built from very understandable basics up through the more complex systems, without getting into all the messiness that complex systems necessarily contain. It was enough to cover it in summary. Very well thought out and presented!
Really appreciate this! Glad you enjoyed it. More marine science videos to come, stay tuned
brilliantly explained!
Brilliant work !
Really well done. Sending this vid to my friends. Filling a gap in my knowledge of the world is thrilling and this video was that.
Well explained.
I knew lots about the tides, but learnt more. :)