What Physics Teachers Get Wrong About Tides! | Space Time | PBS Digital Studios

[@ScienceAsylum]

Dude, you just blew my mind. I'm a physics teacher. Thank you for the correction. I will not make this mistake in the future. I've only had moments like this a few times in my life, but they have a way of making you feel enlightened and guilty at the same time.

[@merloon]

***** Of course you realize that you now can't explain what causes tides without first imparting a total understanding of spacetime and general relativity. Do you really want to have to go there?

[@ScienceAsylum]

merloon Relativity is not necessary here because the gravity is too weak and the effects aren't all that sensitive. Did you watch the video? He mentioned this. All you need to add to the explanation is a bit of fluid pressure.

[@merloon]

***** I stand enlightened.

[@pbsspacetime]

***** Hey! You've posted some comments on the past few episodes, and I don't mean to ignore you. Just stretched a little thin. But I did want to say (in response to something you asked me one or two episodes back) that I don't mind at all if you help answer viewers' questions (so long as you inject disclaimers when you aren't sure about something). On the contrary -- I appreciate it, and one thing we're trying to do here at the show is be informative enough to both laypeople _and_ people with physics/math backgrounds that we'll get a good chunk of the latter showing up in the comments sections to help out the former. So by all means, carry on. I can't answer everyone myself, and I appreciate all the help I can get. Where do you teach (like what country, age group, etc)?

[@ScienceAsylum]

PBS Space Time Thanks for the reply. I never got the impression I was being ignored :-) You have a popular channel, so I'm sure you're busy. I'm also happy to be involved (or help out) in conversations in the comments when I know something about the topic. I would never claim absolute certainty when I don't have it. It always drove me crazy when my teachers did that. I've been teaching college part-time in southeast Michigan at several different schools for almost 10 years now (currently at one university and one community college). I have a masters degree in physics and did my thesis on white dwarf stars. A couple years ago I started a science KZbin channel and I love it, but it's kind of hard to get noticed these days. I do what I can.

[@tibees]

awesome to see so many people updating their knowledge based on new information and not being salty about it

[@janpeternelj2309]

Haha every huge physics YT channel creator is here ^^

[@GumaroRVillamil]

I don't get why there are some many dislikes. On a learning channel you're supposed to learn new things. KZbin being KZbin, I guess

[@SkywalkerSamadhi]

That is the Way

[@dwayneroseborough4403]

@@GumaroRVillamil I'll assume there are dislikes because this is a person's simple rite to either agree or disagree with the video. There is false information about the great lakes for example.

[@GumaroRVillamil]

@@dwayneroseborough4403 how is it false information? The Great Lakes gravitational tide is only a few centimeters (couple of inches) compared to several meters for the ocean. It's so small it's easily overshadowed by other effects they essentially have no tides.

[@friendlyfire7861]

Two things: 1. You would have done well to show why the arrows go left on the left side of the screen. It seems by your logic they would go out. 2. Why do you have the tides occurring at the north and south poles????????????

[@yourguard4]

1. The explanation for that starts at 02:50 Imagine you (the ocean facing away from the moon) are walking behind another person (center of earth). Both of you walk in the same direction. But the person in front of you is walking faster. So from the perspective of the person in front of you, you seem to move away in the opposite direction, even when you actually walk in the same direction. 2. In case you mean the picture at 05:20 - Well spottet :D I dont think they did that on purpose.

[@friendlyfire7861]

@@yourguard4 Thanks for the heads-up. As it happens, the penny dropped a few hours later when I remembered the pseudo-force; until then, I was thinking in terms of the later portion where I was still thinking that, well, if the gravity is pointing toward the moon, shouldn't those acceleration vectors on the far side also face in; he did explain it, so that was my misapprehension. If he had shown the arrow going the other direction at 5:03 as well as the one going toward the moon, I think that would have spelled it out a little better for the dim ones like me. I understand that you can't please everyone though, and as I am constantly reminded, my "limitations know no bounds." Also appreciate corroboration on the other observation. That's where I started thinking I was either missing something big, or he was 😂 It so happens that other videos I looked up showed the correct orientation of the earth but likewise didn't spell out that last little bit. It might be worth bearing in mind for anyone who makes a similar video in the future since that opposite bulge is the hard part to understand. I can remember one or two science teachers talking about gravity and then kind of saying whatever, whatever, of course there is a bulge on the other side too, whatever, whatever--oh, Is that the bell? Class dismissed. 😞

[@from_nowhere]

@@friendlyfire7861An interesting reply, but … IT DOESN’T WORK LOCALLY, ONLY ON MASSIVE DISTANCES LIKE BETWEEN GALAXIES. The Earth is neither static nor accelerating in a straight line motion. According to correct physics, we introduce an “apparent” force into the non-inertial frame, so as to be able to treat the earth-moon system as an inertial frame of rest. That’s what I was taught at school. The tide on the far-side (away from the moon) is caused by the resultant factor of this introduced force, which acts in a direction opposite to the gravitational attraction. Therefore, it’s called a “centrifugal” effect. This video forgot to mention the existence of a Barycentre. Nice talking to you. Happy New Year.

[@xochitlfischer6453]

Thanks, that’s how I’ve always imagined it. The analogy about people walking increasingly faster towards the moon is misleading, because the person at the centre of the earth is actually walking in a circle around the common centre of mass, and from there perspective, witnesses the other two walking away from them. Due to the combination of gravity and the pseudo-force, mentioned by “friendlyfire” above. Thank you both for explaining this so clearly and humorously for me.👆

[@friendlyfire7861]

@@from_nowhere 🤣🤣. Thanks for the clarifications, and HNY to you, too.

[@crystalclark3509]

I will now not cover tides and gravity in my class today, as I need to watch this video again - I found it hard to follow the fast talking, but I obviously need to learn more and not be so confused before attempting to teach it! Thank you.

[@wavydaveyparker]

Hello Crystal, with a name like that, I’m positive you’ll shine in the classroom, when the confusion clears? Please let me put this, as politely, as possible. If you need any help in understanding this video further, then I am available…and I promise to talk very slooowly!! 😅 Until you’ve understood and feel confident in teaching gravity and tides to your class. Kind regards.

[@vishnu437]

Yes, too much fast talking here, & in many other, otherwise, good online presentations. But, voila, KZbin has a solution for these motor mouths. Just go into "Settings" and click on a slower speed (probably .75x) and let his, likely over-caffeinated, brain relax. (Also a good trick for actually being able to follow the action in basketball games :)

[@mylesmackey2430]

The extent to which you guys interact with channel followers is incredible. I've never seen a channel attempt to answer so many viewer's questions and with such detail and genuine interest. Keep up the great work, this channel is amazing!

[@feynstein1004]

That's what I admired the most about this channel. I feel like they don't do that as much these days.

[@tylerquinlan2613]

@Science Revolution 🤡😂😂😂😂😂😂😂😂😂 Man. This is some next level cognitive dissonance.

[@AshPragasam]

6:53 "A human is basically a big sack of water" I had to pause and look at the wall for a few hours

[@jadely77]

This is the first time I’ve ever seen anyone outside my family talking about having to look at a wall in contemplation.

[@AshPragasam]

@@jadely77 maybe we are related

[@GandharaBlogspotCa]

Even the human body is affected by the moon and the sun.

[@johnunderwood-hp8rj]

A walking mudball if you want to be technical.

[@pierfrancescopeperoni]

@@GandharaBlogspotCa I'm squeezing.

[@mickblock]

This guy speaks so clearly. I don't always understand what he's explaining, but I'm always impressed about how well he speaks. I seriously am curious to know if this guy has ever mispronounced a word or uttered "uuuuhm."

[@edwardsheets]

+Michael Block I agree, this guy was great. I don't know why they felt the need to get a new host.

[@kerianos]

+Michael Block Well he might just have a script, right?

[@mickblock]

Duh.Really?:)

[@2010RSHACKS]

+Michael Block Checkout 10:45

[@mickeydonald1530]

That cracks in voice proves he is human like rest of us👀

[@jhettema715]

Man , forced staying home really gives the possibility to learn things. Thanks!

[@777Skeptic]

And PBS has the good stuff!

[@siobhangraham7280]

The force isnt "fake," it exists - you can find terms for it in the frame of the earth when you derive Newton's laws of motion. It's a fictive force - which means it arises as an interaction between an object and the frame, rather than between objects.

[@perseverancerover]

That is an absolutely exceptional comment. And I totally understand what you’re saying, I’ve never heard it worded like that before, and would’ve used the word ‘apparent’ instead of ‘fictive’, but it was brilliant nonetheless. Thank you. We can consider gravity as a fictive force as well, because it only appears in an accelerated frame, just like you explained.

[@siobhangraham7280]

@@perseverancerover Yep! Apparent is another word I've heard used for it. Also inertial force, pseudo force, and d'Alembert force. They're fascinating interactions, and definitely show how important choosing the right frame is!

[@perseverancerover]

@@siobhangraham7280 Brilliant! I’m literally stunned. *Jean Le Rond d’Alembert* - what an amazing mathematician! - I can’t thank you enough for bringing his work to my attention. How on Earth did I miss that? Would you do me the honour of posting this comment on a silly video called, what atomic school gets wrong about tides! - because you’ve just solved the riddle that been running through my head for ages and the solution was there all along, written down in 1743.

[@siobhangraham7280]

@Science Revolution This is incorrect. The tides are caused by gravitational differentials between two bodies - in the case of Earth's tides, about 90% are due to the gravitational differential between the Earth and Moon, and 10% by the gravitational differential between the Earth and the Sun. When the Moon and Sun are lined up, exceptional high or low tides are seen, depending on whether they're on the same or opposite sides of the Earth.

[@perseverancerover]

@@siobhangraham7280 Once again you are correct and may I just add…that for these gravitational differentials to take effect, there must be a zero point around which they can act. And that is where the ‘d’Alembert’ forces come into play. The ‘net’ acceleration at the centre of the Earth is zero, because it is in orbital motion around the Earth-Moon barycentre and that barycentre is in orbital motion around the Solar System barycentre.

[@brian554xx]

I watched until 2:30, then missed the rest because I switched Earth's gravity off and had to swim very far to reach any air.

[@oortcloud8078]

The perfect comment Brian, although it was six years ago, and you're probably still swimming, hoping to reach some air and find the non-existent moon, which left its orbit when you mistakenly switched off the Earth's gravity. Although, you wouldn't have to contend with any lunar tides, and the solar tides are miniscule in comparison. Good luck with that, and keep swimming.

[@fiveohfivethree]

"Everything I just said is oversimplified" I didn't understand a word you just said. I've never felt so stupid.

[@trishulsolanki5298]

May be stop pandering to the meme culture of today and, as a first step, make effort to spell properly. That might help lift you from that feeling, if you want your situation to be bettered.

[@deusexaethera]

The tides are caused by the difference between the orbital _radius_ of any particular molecule of water in Earth's oceans, vs. the orbital _velocity_ of that molecule, which is the same as the orbital velocity of the rest of the Earth. Oceans on the side of the Earth facing _away_ from the Moon are orbiting the Earth-Moon center-of-gravity at a higher velocity than their orbital radius can support, and so they get flung outward by centrifugal force. Oceans on the side of the Earth facing _towards_ the Moon are orbiting the Earth-Moon center-of-gravity at a lower velocity than their orbital radius requires, so they fall inwards. Both effects cause the oceans in those spots to bulge upwards from the Earth's surface. The same effect causes objects in the lower half of the International Space Station to fall slowly to the bottom and objects in the upper half of the International Space Station to get flung slowly to the top.

[@tonyybandz]

🤣🤣🤣🤣🤣🤣😂😂😂😂

[@orlandomoreno6168]

@@trishulsolanki5298 this is ok boomer material

[@gabrielandradeferraz386]

welcome to science, the more stupid you feel, the more you are learning.

[@ultimatedeatrix9149]

Wow this channel never fails to impress me. I just watched a video on how tides work which was similar to the description he gave in the first 4 minutes and left confused why do the effects only occur in oceans. This video cleared it up so well.

[@MarshmallowRadiation]

This confirms what I've thought for a while: fluid dynamics is frickin weird.

[@GeneralPet]

SafetySkull mindblown

[@jaimeduncan6167]

Noah Fence fluid dynamics is one of the main reasons super computers were build, so you could not be more right.

[@IamGrimalkin]

Jaime Duncan I don't quite see the difference between "supercomputers" and something like say, Colossus. Surely it was "super" for its day?

[@jaimeduncan6167]

IamGrimalkin Colossus was not a stored program machine, and we can argue if it was a truly universal processor. In any case I am not sure what is your point. Could you expand a little so I can reply to you in a more sensitive way?

[@IamGrimalkin]

Jaime Duncan What I mean is, what is the difference between a "supercomputer" and an ordinary early computer. Both of them take up the space of a room. Supercomputers today are much more powerful than them, but a supercomputer in the future may make ours look wimpy.

[@DavidHeizer]

The bit around 7:09, where the surface of the Earth lifts up to meet the elevated swimming pool water, also explains how planets with no liquid oceans can become tidally-locked (as, in fact, is the Moon itself): these forces operate on the whole planet, not just the water. (The oceans just react to it more dramatically.)

[@fivish]

While he is talking, time appears to speed up. Is this because he is talking so fast?

[@oliviamou60]

Everyone: talk too fast No one : Me : doesn't notice a thing because slowed it down to 0.9x

[@litigioussociety4249]

I was watching on 2x speed, so it was actually faster for me.

[@LuisSierra42]

It's time dilation

[@ex3jets]

Bill O'reilly should watch this.

[@Numbers_Game]

ex3jets People laughed at him when he asked "how do you explain the tides?" Perhaps he knew this all along and he was checking other people if they got the right answer. Dun dun dun!

[@daveolsen236]

ex3jets Never a miscommunication!

[@TSCTH]

Science goes into one ear of Bill O'Reilly and out the other... You can't explain that!

[@Epoch11]

NOBUNAGA1991 Bill knows all and now I hear he is passing all that knowledge on to Donald Trump........so America........we gonna be alllll right!

[@yaribsuarez8725]

Mark G JAJAJAJA

[@dwayneroseborough4403]

Very interesting, but having lived 40 years around the great lakes I can tell you that tides are indeed very noticeable, so much that it factors into launching a boat for example. The flight locks in Niagara need to factor in the tides when raising or lowering a ship as well.

[@andyveh221]

The locks look interesting, see en.wikipedia.org/wiki/Flight_of_Five_Locks I looked up Welland Canal and couldn't find anything about tides. oceanservice.noaa.gov/facts/gltides.html mentions that tides may be around a few cm. They also mention and link to a phenomenon named "seiche" that can be mistaken for tides.

[@spacebar9733]

I live in California Bay Area and I agree.

[@SharksfootSoup]

OK, then, the mind of this physics teacher changed! I will (a) revise my explanation of tides and (b) mention tides when I talk about pseudoforces, which I never thought of before. It's an awesome example!

[@HebaruSan]

I only discovered this channel after this guy left. :( He's like Carl Sagan on hard mode.

[@fruit21orn-imsin12]

left? really? why he left? idk about that

[@Trump-a-Tron]

@@fruit21orn-imsin12 3 year old comment just cracked me up! xD _"He's like Carl Sagan on hard mode."_

[@jamesbarker6373]

He is like Carl Sagan without the frustrated know it all attitude

[@rhoddryice5412]

Matt is way better. This guy's voice is annoying.

[@randomguy263]

Well, I prefer Matt.

[@garysmith1135]

I liked when you talked about the nooks and crannies having larger tides. It's comparable to what makes the windy city so windy.

[@nothingnewhere6551]

Great video! I was a physics major. My class was taught that there were imperceptible tidal effects on both land and inland water bodies because of tidal forces. There is a mathematical approach to this in the undergraduate text Thorton's Classical Dynamics of Particles and Systems using similar assumptions -- for anyone who is interested. It gives functions for these tidal forces that can be used to calculate a vector at any point - using those assumptions. Going through it you will get math for what the man in the video is presenting. Although I think the title is a bit misleading, partially because I wasn't taught the incorrect way he mentioned at the Community College, Undergraduate, or Graduate level, the detail he stresses is an important one and often left out. I really enjoyed this video, thanks!

[@nothingnewhere6551]

@el profe vinagre I have not said anything incorrect friend. You are right to mention rotation around a center of mass. Because this is often a preferred coordinate system to deal with rotating bodies.

[@stuartrenwickcarson1]

So many factors to explain a seemingly simple phenomenon. Great video. Great comments pointing out that the moon does not orbit the Earth, rather they both orbit their common center of gravity so from the POV of a frame of reference at that shared center of gravity there is an apparent centrifugal force that adds to the tidal bulge on the far side from the moon. The only factor I didn’t see mentioned in the video or comments was resonance. From a rotating frame of reference on Earth the tides are sloshing back and forth in big “basins” for the oceans and smaller basins for lakes. The resonant frequency of water sloshing in a basin varies by size from about 1 second for a teacup (which is why tea spills so easily when you walk at about 1 second per step). “Basins” with a resonant frequency close to 12 hours will get bigger tides as the oscillation of forces will align with the resonant frequency. Veritaseum has a great video on using analog computers (pulleys, wheels, rotating spheres etc) to calculate tides. Incredibly ingenious.

[@Morningstar437]

I still Dont get this, they all say the bulge is already there, if bulge of water is always there how come entire earth is rotating under that bulge without being drowned? Does this also means that all fishes and turtles stays on the same bulge and earth just is sweeping under them. My head is spinning 😅

[@wavydaveyparker]

Hi again, that’s actually really funny, but I titled my video to match this…it’s called, what *school* gets wrong about tides! I have already begun writing a reply to your head spinning 😅 but, you’ll have to comment on my cartoon if you want to read it. Thanks for your determination to find the answers you seek. 😇 My head is spinning now 😅

[@DevinDTV]

The bulge is there, but it's less than a meter tall at the equator. What do you think happens when the shore, which slopes up to a height much more than 1 meter, sweeps under this bulge? The first (less than one) meter gets submerged, and the rest doesn't.

[@SpeakerMunkey]

4:04 "so should sand and rocks" well my friend they are. There are places in the world, in-land, where the water table lowers during high tide as the rocks are spread apart from the lunar gravity, opening up gaps for the water to occupy. A bit like decompressing a sponge. I encourage everyone to read The Ascent of Gravity by Marcus Chown - mind blowing book! Anyway, good video even if you are shouting the whole way through.

[@sasmitha8446]

I wish there was a channel like this for biology!

[@sasmitha8446]

Nooooooo Khan Academy is nowhere near as good man. I want discussions, not lectures. 🤕

[@rappelz2011]

check out this channel AK LECTURES

[@BaconSizzle48]

"minute earth" is a great but different option for life sciences.

[@Naurto58]

That is not biology though, that is experiments from all fields that explain the process of that experiment for the sake of understanding it rather than just teach a theory.

[@ECxTheMaster]

look up "crashcourse biology"

[@POWERBUT]

I didn't realize my understanding was so ridiculously far off. Noted.

[@arshiazarrin]

POWERBUT You always know how much you know less than how much you dont know; you know?

[@neutronstar6739]

POWERBUT good thing my understanding not far off...

[@TheWormzerjr]

Do you want to know how far off 99 percent of people are off. click my name to watch part 8

[@Amamos]

I've been trying to understand the two tides a day for over an hour now from many sources. I clearly see you know what you are talking about. But I still can't understand the most important part, the directions of the tidal vectors. I can see the 0 degree, point A, vector being a rotation inward, but not a direct 180 degree arrow. Also, can't understand a 350 degree vector pointing away from the moon side, neither the 270 degree one totally opposing the moon. Can you or any other viewer help me with this? Thanks!

[@wavydaveyparker]

Hello Alexandre, well as a matter of fact…Yes, I can. And I’d really like to help ease your confusion. (btw, is that a underwater fur-seal in your pictogram? Nice!) What you’ve amazingly managed to spot there, is the only misleading part in this otherwise excellent video. However, I’m now becoming increasingly fed up trying to explain this to everyone, when all I receive in return are insults or no reply. I didn’t make this video, but pbs seem incapable of answering there viewers legitimate questions. So, can I politely ask you to watch my own daft little video, which you-tube kindly buried ages ago! And comment there, because I’ve already answered your excellent questions on a number of occasions. Thank you!

[@Amamos]

@@wavydaveyparker Nice, thanks a lot! Going to watch it right now. In case anyone also wants, it's very easy to find, it's the first video upon clicking on his name (at least today it is, 12/20/22, hehe)

[@zenastronomy]

I believe. but i could be wrong. vector forces are relative. they take direction into account. in this diagram, he didn't mention it. but it's done from the point of view of you being right bang in the centre yellow dot. if you were standing in that dot, from your relative point of view. the moon's gravity would stretch the entire body of water towards the moon. but because the side of the moon is being pulled and thus stretched more strongly, due to being closer. and the side furthest away from the moon being pulled and stretched more slowly, due to being further away. from your perspective an illusion takes place. where it looks like the left side is actually moving out left, whilst the right side us moving right. from your perspective in the middle, the earth is being stretched left and right. this is a perspective illusion. if you were standing outside of the earth looking at the diagram. all the arrows would be pointing right, but the ones on the right would be bigger. i believe they call this two different perspectives, either an inertial or non inertial frame of reference.

[@wavydaveyparker]

@@zenastronomy That is an interesting comment Zen, but what you’ve just described there is “free-fall” motion in a straight-line! Also known as, “Einstein’s Happy Thought.” Can I politely ask you to follow Alexandre’s friendly advice above, and I’d be more than happy to discuss this reference frame misconception with you there. Thank you!

[@Smullet90]

No trigger warning and now I'm back on the pods.

[@whedonobsessed]

*adding to Watch Later for when I'm caffeinated enough to understand this*

[@wilfdarr]

I did my grade 5 science fair project on gravity and tides, and got a really good mark. Looking back, I deserved an F. Good to know, considering I actually use what I thought I knew now when I'm sailing. Thanks for clearing this all up!

[@wilfdarr]

@Science Revolution You claim tides are caused by the sun: why are there two tides (one at night) and why are they 12 hours AND 25 minutes apart? Also, the tidal bulge actually travels 2400 miles per hour, but nothing else you said was correct, so why would that be.

[@wilfdarr]

@Science Revolution Full moon, New moon, the moon's size doesn't change! But yes, everyone else is stupid, definitely not you. In English we have a saying, “it's better to be thought a fool than to open your mouth and remove all doubt”: you have removed all doubt!

[@seanh5505]

And just as it goes with every episode you post, what I thought I knew turned out to be incorrect and you broke it down and totally schooled this fool. That pimple analogy you used is such a clever way of explaining tides and it's really easy to understand. So much so, in fact, that I'm actually surprised I never heard it before. It's even got the added bonus of explaining the absence of tides in lakes, it's got it all...the "simple pimple analogy" 4 life homie. You're damn good at spelling out some of the most hard-to-grasp stuff in a way that is surprisingly easy to understand. I've said it before (as have many others), but you will be sincerely missed, Gabe. Do you have any idea how many hearts you're breaking by leaving us? Don't you care?! There are still things left that you haven't simplified for us, so as soon as you just explain how everything works everywhere in the universe then you'll be free to go. Kidding aside though, while I'm bummed you're leaving I am really looking forward to what the last few topics that you cover are going to be. Hopefully about things that can charm you up and down but are also strange from the top to the bottom (OK now I'm just being TOO obvious). Anyway, I'm sure whatever you decided to do the last few episodes about will be interesting, easy to understand, and accurate. OK I think I've already hailed you enough in this comment so I'll shut up now. Much obliged for all you do, Gabraham.

[@ericlarue8010]

No , the opposite bulge doesn't look like anti gravity. It looks like outward excelleration due to centrifugal force of the earth and moon orbiting each other around the bary center. The moon also has bulges but no tides because it doesn't rotate relative to earth.

[@wavydaveyparker]

That is an ‘excelleration’ comment Eric and I applaud your mention of the barycentre. It often gets overlooked and it was an unfortunate mistake by the creator to leave it out of his calculations? Can I just politely suggest one thing though…Since, a lot of people have trouble understanding the simple concept of ‘inertia’ behaving like a ‘force’ … maybe we can treat it like an ‘anti-gravity’ effect or better still … a ‘perceived’ gravity effect. They’re both essentially the same thing after all? Take care.

[@gueswho1968]

I don't completely understand this, but this is the potential of the internet. Thank you.

[@MrBenny10101]

Tide Goes In, Tide Go out, can't explain that

[@ytsas45488]

+MrBenny10101 He just did.

[@rudykrish3869]

+Aaron Cruz he is making fun of bill o reily..lol

[@iprimoonanollie2598]

bread goes in, toast comes out, you can't explain that

[@TIMEtoRIDE900]

Tide goes in, stains come out !

[@stonestreaker]

Never a miscommunication.

[@David-fe1qz]

I was really hoping you would bring up equipotential surfaces. Water is pretty neat in that it maps out a single equipotential surface (which is a surface running perpendicular to the net force), so once you add in the pseudo-forces (or fake forces in this video), the tides just pop out as a result of the equipotential surface.

[@crowguy506]

After all the time it is still fascinating that it actually makes sense to switch the speed of his videos to 0,75 and get a reasonable pace without even noticing a slo-mo until the music begins. Actually you get a quarter of a video „for free“ compared to new videos.

[@mwm48]

Darkest eye circles I’ve ever seen. That’s how you know he’s legit.

[@antebellum1776]

Thank you for the visual representation of what you're talking about. It makes everything a million times easier to understand, especially for someone who isn't a native English speaker and doesn't really know all the terminology. Really great video! You got yourself a new subscriber.

[@peekeyeseek]

This is gonna go right over my head. But I'm watching it anyway.

[@bobbyharper8710]

"Tide goes in, tide goes out. Never a miscommunication. You can’t explain that. You can’t explain why the tide goes in.”

[@yaribsuarez8725]

Bill O'reilly jajajaja

[@Niamaru]

Bobby Harper making sure this was here

[@alcoholbadweedgood]

Bobby Harper Food goes in, poop comes out. You can't explain that.

[@thewarri0r9]

Bobby Harper I think the reason why tide goes in is gravity of the earth pulling back the tide, i may be wrong

[@bobbyharper8710]

thewarri0r9 We're having fun with a Bill O'Reilly statement about tides.

[@SchemeTintFocus]

I am so glad I heard this. The earth is rotating so fast, it makes far more sense that tides are caused by inertia, rather than anti gravity.

[@perseverancerover]

That is actually a brilliant comment David. Maybe we can think of inertia has behaving like some form of anti-gravity or ‘perceived’ gravity. It would certainly answer the question of the the far-side bulge, better than some peculiar explanations that exist on you tube.

[@krissto22]

@@perseverancerover I was thinking of the same. What doesn’t make sense to me is that if the moon gravity can impact such huge body of water what about the space junk/satellites, ISS, etc.? They don’t change their position. It never made sense to me. The way it was explained in here we’d get much bigger tides at the tropics rather than as high as Canada, but then why does it happen twice? 🤔

[@perseverancerover]

@@krissto22 Hello Kriss, thank you for your reply and I totally understand. Can I politely suggest you find this video: *What Atomic School Gets Wrong About Tides! | Inertia | And Spacetime.* - As there are some comments there, which might help answer your questions and a 👍 support would be much appreciated, as I’m getting tired of continually repeating myself in other peoples videos. Thank you.

[@krissto22]

@@perseverancerover I totally understand. I wasn’t expecting this speedy reply. I’ll check that out. Thanks.

[@fpdima]

I took up sailing as a hobby and wanted to know about tides and why they happen. This was an excellent explanation. Thanks!!!

[@--dh--]

Anyone sent this to Bill O'Reilly yet?

[@gogglesow1358]

awAdmin EARTH IS FLAT EXCEPT JESUS BILL OREILY IS A PROPHET WILL NOT LISTEN TO THESE LIES

[@antebellum1776]

@@gogglesow1358 You're joking right?

[@Jesse3beards]

Can't explain that

[@WiscoDrinks]

just found a new channel to binge watch.. time to blast off.

[@andynz7]

I miss these early spacetime vids!!

[@mouduge]

Great video! One crucial point you haven't mentioned is the importance of resonance. The Moon squeezes the oceans at different places across time, and this creates very low frequency waves. In some places, depending on the space between continents, some waves will be amplified by resonance. You have probably tried this before: you are in your bath and you move forwards and backwards: even if you don't move much, if you do so at the right frequency, the wave will grow larger and larger, until water spills out of the bath. This resonance effect is quite important (as are nooks and crannies, as you mentioned), and it also explains in part why there are not tides in lakes: there is not enough water for resonance effects to build up. Another interesting thing about it, is that much of this resonance effect builds up close to Antartica, since it is the only place on Earth where waves will not be stopped by any continent as the Earth rotates. This is why a high tide first hits the South West of France before it reaches the North East. The depth of the ocean is also crucial: since the English channel, between France and England, is pretty shallow, the tide takes hours to cross it. So it's actually high tide in the South-West of the channel while it's still low tide in the Nord-East, just a couple hundred kilometers away. Another fun fact is that the Large Hadron Collider is so large and sensitive to movements, that Earth tides can actually be observed (one side of the loop will be higher than the other, due to tidal forces).

[@rafaelmolinanavas8862]

Please kindly have a look at two comments I posted a couple of days ago ... It might interest you.

[@makisjnx007]

You two are insane

[@dud621]

This is like my fourth time watching this video over a few years and this is the first time I actually understand it lmao

[@kfossa344]

52 is a magical age

[@ihaveshitonmyhead9821]

Wait huh? How!?? I'm still struggling to understand... Is it because Earth is actually attracted to the moon's gravity and so the earth move towards the moon and like the opposite side of the earth that's not facing the moon falls behind?? English isn't my first language and although that might be a non-valid reason. I want to still understand it, but though I have to rely on simpler terms.

[@youtoober2013]

I was always confused, _every_ time I saw an explanation. The whole time I'm thinking... I get why it rises on the moon side, but WHY THE OTHER?! (not plausible) Low key I led my whole life just ignoring that other tide (and bathtubs). This immediately made much more sense. It's where you said "here's that refresher course" that I realized why they don't teach this in high-school. Almost like in order to answer one answer accurately, you have to answer all of them first.

[@friendlyfire7861]

I remember my teacher kinda skipping the part about the other bulge. They'd kind of gloss over it.

[@geoffsmith3263]

Good video. I saw this explanation many years ago in the Encyclopedia Brittanica and that has been the way I have always understood tides. I am constantly amazed at how many wrong explanations are out there.

[@mdmobashshir432]

0:38 Kurzgesagt!! but they never made a video about tide.

[@InHumanoXY]

+Mobashshir Feroz I was going to say the same. I love Kurzgesagt. And that is how they animate the planet, haha. :v

[@mdmobashshir432]

Humano InHumano Well and their recent animating skills have improved exponentially. and there theme music is just in my head, all the time..

[@InHumanoXY]

+Mobashshir Feroz only bad thing is that Kurzgesagt has less videos, although they are very good.

[@YouAintGotNoTegridyBoi]

I've already been rather aware of these facts, it seemed to directly correlate with my understanding of earth's physics. I remember correcting my sailing instructors in the past on how tides work, they disagreed with my view that it was actually all a result of an individually negligible amount of force being multiplied by massive amounts of water. Thank you for providing context and figures to explain my preconceptions, now I'm secure in this knowledge because of you.

[@TribusMontibus]

Excellent! Just about the only correct explanation I’ve seen on KZbin. 👍🏻

[@RevolutionibusOrbiumCoelestium]

At 5:03 can someone explain how the tidal acceleration vectors to the left hand side of point A work? ie on the opposite side of the earth from the moon? I must be missing something.

[@JonGiuliani]

I worked it out. OMG it's true, it pushes back away from the moon. He really should have done the diagram for the left side points. Work out the "vectors" of a point left of A, call it B. Being B farther away from the moon its attraction is smaller than A and the centre. When you subtract the centre from the B vector you're left with a backwards vector. Mind blown

[@claudio_motta]

i think he missed it but i will try to help you with what i did understand starting from the initial A location, you can see that when you move point A to the left, the distance from the point A to the moon will increase (until you reach the earth-moon line, that is its max). with that in mind and "aware" that the gravitation force is inversely proportional to the square of the distance, you can see that the value of the force at the point A due to the moon's gravity decreases as you move it, you can imagine (or draw) the force vectors due to the moon at the center of the earth and point A, then you change the inertial reference frame to non-inertial earth reference frame (as he did before) and add the vectors, and you should find the same as he shows there it's the opposite when you move the initial point A to the right: the distance from the point A to the moon will decrease (until you reach the earth-moon line that is its min) and the value of the force of the gravity will increase at point A. you change your inertial reference frame to non-inertial earth reference frame and add the vectors and boom! there it is. feel free to disagree or to ask me to explain better =)

[@RevolutionibusOrbiumCoelestium]

Ok it took a while but I finally got it! This guy explains it better: kzbin.info/www/bejne/a2m7gquga9RoiLs

[@sivansharma5027]

@@RevolutionibusOrbiumCoelestium dude, thanks for that! This is legit a much better explanation

[@SvenPek]

@@RevolutionibusOrbiumCoelestium It is sadly also the wrong explanation as pointed out in this video. The vector explanation is correct though! Your videos explanation of the tides is not.

[@gunlovingliberal1706]

This video contains one of the best explanations for tides I have read. Thank you.

[@LoveDoctorNL]

Tide comes in, tide goes out... you can't explain that 🤣

[@kobirrajib]

Problem is you forgot the rotation of earth. Otherwise you should have already understood

[@amdenis]

Great job. I have had that almost exact conversation with friends and others in physics for decades, and it really helps explain the need for detailed, progressively constructed analysis. We did a Matlab/Simulink on an SGI Onyx II in 1997 for other purposes, which also showed the potential to affect bodies of water when we added the fluid dynamics layer to the analysis. We were surprised that the effect was enough to show that even a glass of water exhibited that effect in a measurable way near the molecular scale. BTW, although we were doing it as an outgrowth of a commercial project, and our simulations indicated that the effect was greatest for the small, localized body of water (e.g. a glass of water) at 45 degrees to perpendicular to the moon on the side of the moon. We later assumed, although we didn’t validate it or do additional work on it, that this could mean that the second order differential of the vector differential was greatest at that point for all bodies of water. We got busy with life and projects, but there are interesting implications if that is correct. Just some food for thought.

[@TheCorrectionist1984]

Can you explain the vectors pointing away from the moon on the bulge opposite of the moon? The hydraulic explanation makes so much sense but i don't understand those vectors as the result of gravity. I thought it's more like squeezing a ballon around it's circumference and then both ends bulge.

[@ldouglassbottorff9792]

Best explanation of tides I have found on KZbin.

[@stefanoalto1759]

I know an even better one 😃 check out Tribus Montibus Oceanography

[@cortster12]

3:52 I love the animator of this. The Fluttershy and Rainbow Dash cameo was a nice touch.

[@ten.seconds]

cortster12 Ponies are the new apples in explaining physics.

[@pbsspacetime]

cortster12 He's great, right? Michael Leng, here at Kornhaber Brown.

[@SMacCuUladh]

this presenter is one of the best i've ever seen, great communication, great energy, get him on tv!

[@rKhighlight]

SMacCuUladh pls dont, KZbin is a far better format for stuff like this and especially his style of explaining things.

[@chavab8753]

recently Neil deGrasse Tyson was on an interview showing an animation of the water bulging as in this video. He showed the earth apparently moving under the water to meet up with the bulges, instead of the bulges impacting the land masses. It almost seemed to imply that the earth would rotate under a giant ocean instead of the water following the inertial frame of the earth. The interviewer's comment was "mind blown". Not especially insightful. The more I thought about it, the less sense it made. Everyone neglects the continents, which are non-trivial. Did anyone see this interview? Was it correct at all? I'll admit to being more confused than ever.

[@pusingfismat7099]

It's just another simplification. Sure, there are borderline between land and water where tidal current impacts the shoreline. Hence the actual, precise tide cycle at different places might vary. But overall, such drowned-Earth model isn't entirely wrong since ⅔ of land is submerged. It serves the purpose of showing that the average cycle is due to land rotating with different rate than the tidal bulge.

[@MostlyPennyCat]

Many years too late, but the reason there are tides of different heights is _actually_ because Slartibartfast designed it that way.

[@tohellorbarbados4902]

Thank you, Slartibartfast. You can go now...

[@mirkopolyak3592]

Don’t panic! ;-)

[@Christophe_L]

Amazing explanation. It feels like some day, "high school" will just be a well curated KZbin playlist.

[@tocodelray]

And then Covid happened and your comment came true.

[@Christophe_L]

@@tocodelray Hah. Well spotted.

[@dwamenaboateng468]

My daughter was having a hard time getting this at school. She now gets it thanks

[@picotingle]

Thank you so VERY MUCH! At last a coherent explanation for BOTH tidal bulges. I have been so frustrated looking at the conventional explanations which are descriptions not fully explaining the second bulge. Great work restoring my confidence in the scientific method.

[@Biskawow]

Cant wait to get invited to a party so I can explain to everyone how everything they think they knew about the tides is wrong. I'll be the most popular guy there!

[@bipedalbob]

Yeah cause everybody loves a no it all.

[@WellMefisto]

When you get the party, everyone else has had also seen the video... 😒

[@bipedalbob]

Very interesting, and how did you figure this all out. Not the stuff about tides that are accepted science but your theory on how tides occur if not from gravitational pull of the moon?

[@bipedalbob]

@Science Revolution so you have proof of your theory's or will I just see blabbeda blabbeda blabbeda.

[@Biskawow]

@@bipedalbob you can see words? Whooooaaa

[@samson7383]

The tidal bore in st. John New Brunswick is truly amazing to watch they call it reversing falls

[@prjndigo]

He missed the gravitational offset of the focus of earth's gravity due to the moon. It is actually very important.

[@OriginalOmgCow]

It's a popsci channel pretending to be more what did you expect.

[@nihonsuki]

Thank you! I learned this in my first fluid mechanics course in college over 40 years ago, and have been teaching/correcting people ever since. Another thing they get wrong is how airplanes fly.

[@Faint366]

nihonsuki ok, so now I’m curious. Does the shape of the wing force excess air underneath to increase the pressure below and cause a decrease in pressure above allowing the plane to lift or is that wrong?

[@nihonsuki]

Faint366 I'm not sure what you mean by excess air, but the wing diverts air downward, thus producing lift. A flat plate can do this, as well as your hand held outside a moving car. Wings are shaped to improve efficiency and increase stall margin.

[@deldia]

@@nihonsuki yes but really it accelerates air downwards so produces and equal and opposite force.

[@jensonee]

thanks, at 75 i feel happy just listening and watching these videos. and look over there are a lot more!! and yeah, i do have a monthly contribution going to spacetime.

[@leo_tra]

Great video! thanks! One thing I still don`t get, though. At 5:09, it is clear to me why the vectors on the right side of the Earth point towards the Moon; shouldn`t the same idea be applied to the vectors on the left side as well? They would all be pointing to the Moon, but not as much as the ones closer to it. But in the video the vectors are pointing away from the Moon, as if they`re being repelled. Why is that, please?

[@leo_tra]

@@cybermonkeys I don't think I know anybody called WD. Anyway, even more interested in your reply if you can really fit those 2 expressions in it 👍

[@pratikjeware1892]

@@leo_tra That is because the vectors are drawn relative to the reference frame of the earth. Let me give an example: Let there be 3 cars: A,B and C moving in the same direction on a straight road such that A is ahead of B which in turn is ahead of C. i.e. ->C-> B -> A ->. Now, let the speeds of A,B and C be 10mph, 5 mph and 3mph respectively with respect to an observer standing on the road. Hence, with respect to the observer, on road, the velocity vectors of the 3 cars point in one direction only. But, what does an observer inside the car B see? According to the observer inside the car B, the car C is moving backwards with speed 2 mph (5-3), while, the car A is moving ahead with speed 5mph (10-5).

[@wavydaveyparker]

@@pratikjeware1892 Yes Pratik, and the driver in car B is going nowhere in a straight line (5-5=0) Except in a curved orbit around the common centre of mass! My comment section is still open to insults, if you can get by the guard dogs and barbed wire fence, erected by you tube that is? Take care

[@hayesbrown1021]

Hey man, rewatch from 3:10, that got me too. But it’s all relative to the CENTER of the earth. So B is not accelerating to the moon as quick as the center. So that means it is accelerating the other way!

[@pwolkowicki]

Thanks for the explanation. I could't understand, how the buldge on the oposite side could form, as gravity from Earth and Moon should add, to make the oposite.

[@peterbartley9155]

Pawel W look at his arrows in the picture that shows the bulges. The gravitation effects diminish and the tidal forces then squeeze the water away in the same way it’s squeezed toward the moon.

[@deusexaethera]

The tides are caused by the difference between the orbital _radius_ of any particular molecule of water in Earth's oceans, vs. the orbital _velocity_ of that molecule, which is the same as the orbital velocity of the rest of the Earth. Oceans on the side of the Earth facing _away_ from the Moon are orbiting the Earth-Moon center-of-gravity at a higher velocity than their orbital radius can support, and so they get flung outward by centrifugal force. Oceans on the side of the Earth facing _towards_ the Moon are orbiting the Earth-Moon center-of-gravity at a lower velocity than their orbital radius requires, so they fall inwards. Both effects cause the oceans in those spots to bulge upwards from the Earth's surface. The same effect causes objects in the lower half of the International Space Station to fall slowly to the bottom and objects in the upper half of the International Space Station to get flung slowly to the top.

[@GumaroRVillamil]

He explains it at 2:45. It has to do with the frame of reference. Point A accelerates towards the Moon faster than the center of the Earth, the center of the Earth accelerates faster than point B, therefore from our perspective, point B also seems to be moving away from the Earth. Tidal force, like centrifugal force, is a fictitious force. From our perspective it seems like the tidal force s lifting the oceans at both sides, but that's not what's happening. Remember, the water is not being pulled "outward" or "up". The sum of the force vectors acting on water molecules perpendicular to the Earth-Moon line displace the water molecules towards the Earth-Moon line forming both "bulges". It requires enormous surface area for those tiny force vectors to add up. That is why you only see a significant tide on the ocean.

[@iteggspert9508]

Clearly explained. From all theories about moon tides, I'll take a ride with these explanations.

[@wavydaveyparker]

An expertly written comment from an ‘eggspert’ and I hope you enjoy the ‘ride’ on this ‘correct’ explanation. However, are you not even slightly curious as to why the Earth in this video is remaining perfectly static and stationary, whilst this ‘squishing’ - ‘non-pulling’ action takes place? … I mean we all know that the Earth is…undoubtedly, in orbital motion around the Sun…Right? - Well, the answer is that the Earth is in a ‘free-fall’ motion around the Earth-Moon Barycentre and the Earth-Sun Barycentre, so therefore, we can temporarily treat the centre of the Earth as a static point in space, because the resultant accelerations there balance to zero! So, I hope you found my little intervention on your orbital ‘ride’ interesting and will add it to the ‘eggspert’ things you’ve learnt? Unless you knew this already and I’ve just wasted my time typing. Kind regards.

[@weirdyoda04]

This video has ruined my life. Now every time someone I look up to even briefly talks about tides it shatters my illusion that they are anything more than human. I also resent that I've been taught incorrectly about something so basic my whole life.

[@flowinsounds]

welcome to physics.

[@smoofoperator]

+Vijay Vaddi which is evident in your spelling of taught. You're very right, your spelling does nothing to diminish your point, and I'm only having fun. :)

[@Songer80]

He didn't explain anything about tides either. What he said was that tangential forces causes water to be higher along the equator (basically). Then the planet would just have a "belt" of water around its waist. So what makes it go in and out twice a day at certain places( the definition of a tide)? He didn't explain that. Very disappointed the producers missed that or did I miss something. I don't watch TV so I don't know the joke about O'Reilly.

[@Eric14492]

+ChefHomesteadMaker The rising and falling of the ocean we experience is caused when the earth turns through the two tidal bulges, which are fixed in a line between the earth and moon. The tidal bulges are not “a belt of water around its waist”, or equator. I can understand why you might think that from looking at the 2D diagram. A better analogy is the shape of a football. It has a bulge at each end. Put a football on a table, and spin it slowly horizontally. From a fixed point on the table, the surface of the football will rise and fall away from you, twice, each “day”. Gabe did mention this in the video, he just didn’t emphasize that part because that part isn’t what is commonly misunderstood. I hope this helps.

[@thernandez44]

Oh boy, have I got something to tell you about air foils...

[@2014andBeyonD]

So basically it is the moon, just not in the classical way of understanding.

[@slehar]

Simpler explanation: Focus not on A or B along the sun-earth line, but as you suggest, check points "C" and "D" at the "top" and "bottom" on the earth. You draw their tidal force lines tilted. But consider that the ocean can only flow sideways, not up or down, the tidal effect on oceans at C and D are PARALLEL TO THE SURFACE, one half toward the sun, the other half away, and thus it is the horizontal TIDAL GRADIENT at C and D that "pump" the water in opposite directions.

[@eliaskoff]

Newton's Third Law: For every action, there is an equal and opposite reaction.

[@wavydaveyparker]

Hi Elias, that is indeed a very accurate citation of Newton’s Third Law. And I’m extremely intrigued as to why you would mention it here? Maybe you’d like to discuss this further on the video I made, explaining why Newton’s Laws are still important when dealing with tidal formation! Take care.

[@eliaskoff]

@@wavydaveyparker I mentioned the law because of the shape of the water that bulges from both sides, although it is the force that acts towards the moon, and there is no force on the other side. Thank you

[@wavydaveyparker]

@@eliaskoff That is absolutely correct Elias! And the reason there doesn’t appear to be a force acting on the far side, is because this video fails to mention the most important element behind Planetary Motion and the force caused by this orbital movement, directly balances with the gravitational attraction of the Moon, in exact accordance with the Newtonian Law you mentioned. Please search out my video and I’d be more than happy to explain further, because if I ever decide to make another video explaining tides, then your input would be very helpful. Thanks

[@Drew_Hurst]

I was also looking for a comment on why B would also bulge on the far side of the Earth away from the moon at 0:54 because that is not at all plausible.

[@wavydaveyparker]

@@Drew_Hurst Well Drew, if you can get passed the you tube security on my video? I’d be more that happy to explain! Peace and love to all. Cheers

[@happylittlemonk]

Hi, thanks for the video. As we know continental plate float on magma. They move and get pushed against each other and the pressure builds up to a point that one day it gives way and causes earth quake. I once thought that if the Moon causes tides in the way you just described then surely it can also trigger earthquake are areas of the plates that are about to snap. Then I realised one scientist has already guessed that and predicted a minor earthquake and guessed the time exactly right. So I was wondering if you could investigate that and make a video on it as no one seems to be aware of that.

[@halbrown7121]

"Tidal forces" are those forces that act perpendicular to the gravitational force. This is what would cause the "1000 mile man" to be squeezed inward as he falls from space to the earth, assuming of course that he falls feet first. They are the forces that would allow you to determine that you were in a gravitational field and not in a rocket ship for example that is accelerating at g.

[@gottabweird]

But does this mean the atmosphere can experience tides??

[@HidrogenoyMau]

gottabweird unlike water which is practically incompressible the atmosphere is compressible, so I'd assume that tides in the atmosphere would be barely noticeable.

[@gottabweird]

Mau dL one would then still expect a change in pressure in conjonction with the tides

[@HidrogenoyMau]

gottabweird Yeah, I thought so too, I have no idea how'd that could play out with the weather,

[@gottabweird]

Mau dL um... interesting question.

[@stevepittman3770]

Mau dL Since weather is (as I understand it) a combination of thermal energy from the sun and varying pressure, I imagine 'tidal pressure' within the atmosphere would contribute at least to some probably small degree to weather formation.

[@rh001YT]

At the beginning the hyper gentleman says oceans have tides, but lakes bathtubs and cups of coffee don't. Then near the end of the discussion on tides he says that lakes, bathtubs and cups of coffee do have tides, but their too small to notice. Anyway, while it might be technically incorrect to say the moon lifts the oceans to make high tides, there's not much difference - only a semantic difference - between directly raising the water or pinching it up. The moon is still causing the varying tides according to it's location. A better analogy than popping a pimple by squeezing around it's base might be those pimple popping gadgets that push on the base while sucking up and out on the pimple. But the pimple popping analogy is not very good anyway as it does not include the earth's role in deflecting the pull of the moon somewhat towards the earth's center. I will say that thinking of the moon as squeezing on the earth does a better job of explaining high tide on the side of the earth just under the moon and the opposite side as well. The pimple analogy is even worse in that regard.

[@jdgrahamo]

rh001YT It is not just a semantic difference. The difference between pushing and pulling is not semantic.

[@pbsspacetime]

Gammel Prutte rh001YT I agree, it's less a semantic difference and more a _quantitative_ one. The pulling effect is, of course, there. But on a _liquid_, its effect is, quite literally, millions of times smaller in magnitude than the lateral effect. Almost all of the pressure variations along the ocean that accompany tidal bulges are due to the lateral (tangential) piece of the tidal force, not the radial one (which is easily "matched" by the sea floor and ends up doing very little to the ocean levels on its own). So may the pimple isn't the best analogy -- I'm not saying I have a perfect metaphor. But my primary goal with this video was to combat the *widespread* misconception that the "pulling" effect is somehow the sole or primary mechanism behind tidal bulges in the ocean, which isn't possible in the specific case of the Moon, Sun and Earth's oceans.

[@rh001YT]

Gammel Prutte Hi! In the case being considered here, actually the moon is only pulling, but the pull of the moon in conjunction with the spin and gravity of the earth results in a vector that seems to be pushing. It is worthwhile to note that this explanation was moon-centric. It would make more sense I think to describe the tidal effect from an earth-centric point of view, as the earth has the greater mass. And in any event, from the POV of mass warpage of space time, the influence of the moon on the earth and vice-versa is neither a pull or a push but a warp, each body affecting the other through the medium of space time warping, but the larger mass having the greater effect. Between the earth and the moon the steepness of the curvature of space-time caused by either object alone is a little less steep where the masses are closest, a little more steep where they are furthest, and the result looks like a pinch.

[@rh001YT]

PBS Space Time HI! but in fact the pulling effect of the moon is the primary and only cause of tidal bulges, or high tides and low tides. Take the moon away and there will be no tides. As an engineer I can visualize how the pull force of the moon, pulling on all of the Earth, is redirected by the Earths gravity and spin inertia into another vector, but the average high-schooler may not yet have enough mechanical background to visualize that, even though you did draw the resultant vectors. I am thinking a better analogy would be to show the moon as an octopus, with maybe 50 or 100 tentacles, no one tentacle being strong enough to do much, but the totality of the tentacles attaching evenly across the surface of Earth facing the moon-octopus would result in a squeeze on the elastic, water part of earth, yet still the moon-octopus can't pull the Earth into it's maw as it is too weak. At best it can squeeze a bit. To complete that analogy the earth would have to be animated also, as it should be since it too has it's forces, and so the Earth and it's waters could be shown to be resisting the octopus-moon, it's elastic water shell being squeezed a bit by more by the octopus moon due to the Earth's pull back, or it's gravity or inertia. Sorry if I seem too critical but as an analog engineer I am a bit sensitive to analogies cuz the tighter the analogy the more likely it will be useful towards figuring out what to do next.

[@pbsspacetime]

rh001YT I don't disagree with your point about analogies. Ultimately, we make some editorial choices in the interest of time and presentation. But all analogies have flaws. For instance, your octopus analogy is pretty good, but we then have to address why the octopus is somehow "not strong enough" to pull Earth into its maw (when that's not the case at all -- it's that the planet's motion is circular, which is something we were trying to sidestep in the interest of focusing on the one misconception we wanted to address). In the end, most analogies fail at some level or other, and it isn't always easy to predict which erroneous portions people will take too literally. Know what I mean? But otherwise, I'm with you -- I am perennially in search of less misleading analogies, but they're not always easy to find (and sometimes, they just don't exist).

[@EpsilonEridani_]

"We don't see things levitate during high tide." How cool would that be though.

[@anushkakaushik982]

Why are the tidal vectors on the left portion directed towards left side? When the moon is attracting them from the right side?

[@perseverancerover]

Good question. Maybe it has something to do with the tidal force or motion around a barycentre or free fall or that for every action there is an equal and opposite reaction?

[@anushkakaushik982]

@@perseverancerover the explanation in the video for the vectors on the right side of the earth does not fit to the left portion.

[@perseverancerover]

@@anushkakaushik982 An excellent observation anushka. This video has correctly taken the centre of the earth as it starting position and run its tidal analysis from this point. That is perfectly valid, because the earth is in motion around the barycentre and the resultant forces at the centre are zero. Using the tidal force equation from this point, results in tidal vectors of equal value pointing in opposite directions from the centre outwards. However, I don’t expect you to believe me, as no one ever does and just ends up insulting me! Take care and it was nice talking to you.

[@anushkakaushik982]

@@perseverancerover I will have to learn more about barycentre in order to comprehend what you are trying to say

[@perseverancerover]

@@anushkakaushik982 Thanks, I really appreciate that. If you can find a video called, what atomic school gets wrong about tides! then it might help. All I can say is that you’re on the right track. Ask yourself why anything stays in orbit? And you’ll find that there has to be a balance between orbital motion and gravity. The ocean on the far-side isn’t balanced and wants to continue in a straight line motion away from the earth. Take care and keep thinking critically my friend.

[@lokynokey4822]

Does the atmosphere have tides?

[@rhamph]

Pretty sure the answer is "yes", but there's so much noise due to weather and the like that you'd never notice.

[@mudkip_btw]

LokyNoKey It's hard to measure the 'air level' while water level is easily measured. The atmosphere doesn't have a neat surface like the ocean does

[@Tomyb15]

LokyNoKey I think he answered a similar question in the next video. I remember he said that it does but it wasn't very noticeable because weather.

[@usbgus]

I don't know about the atmosphere but the land mass has tides. We can't really experience them first hand for a variety of reasons but we can measure them.

[@CyberSystemOverload]

This is what I love about Science and its teachers. Zero hesitation to say "We were wrong, heres the correction!" Great video, will remember the squeeze analogy now!

[@lalglassblower1821]

Unfortunately, it not always a *zero* hesitation, as the current state of tidal explanations on the tube clearly shows, but I get your point. Nice one.

[@andyveh221]

If I as physics teacher did say something wrong, I must correct myself as soon as I notice that it's wrong. That's because it's easy for students to show me the correct physics. So I don't have a choice.

[@lalglassblower1821]

@@andyveh221 Yes, I agree Andy, but let’s take this video as an example. Please explain to me, as a physics teacher, why is there no mention of orbital motion, orbital velocity, inertial effects or the factual existence of a common centre of gravity? They all have an obvious effect on the tidal motions on our planet. However, the physics teacher here, neglected to mention anything and concocted a fanciful story about switching off gravity and moving little dots towards the Moon? So, he has no choice, but to correct his explanation, or does he?

[@TribusMontibus]

@@lalglassblower1821He would explain to you that there are multiple ways to arrive at the same force components. Dependent on the reference frame you use to account for forces and reactions, you need or needn't explain certain thing. If you regard moon and earth in a rotating reference frame based on the barycenter, for instance, you need to include such components. If you regard the system in an inertial reference frame, it would be wrong to do so, rather than 'obvious'.

[@dvl973]

I love this show. Seriously.

[@ianschutt6242]

It's taken me 67 years to get this understood....Well actually 15 minutes after 66.99years of not "Getting it"!

[@stiiigert]

I don't get how this is any different from any other explanation that teachers always have given. The earths gravity is slightly countered by moons gravity (in other words "pulled"), more closer to the moon, less farther from the moon, so water builds up closest to the moon. I've never heard any other explanation than this

[@deusexaethera]

@@stiiigert: It's not because the Moon is pulling on the oceans. The tides are caused by the difference between the orbital _radius_ of any particular molecule of water in Earth's oceans, vs. the orbital _velocity_ of that molecule, which is the same as the orbital velocity of the rest of the Earth. Oceans on the side of the Earth facing _away_ from the Moon are orbiting the Earth-Moon center-of-gravity at a higher velocity than their orbital radius can support, and so they get flung outward by centrifugal force. Oceans on the side of the Earth facing _towards_ the Moon are orbiting the Earth-Moon center-of-gravity at a lower velocity than their orbital radius requires, so they fall inwards. Both effects cause the oceans in those spots to bulge upwards from the Earth's surface. The same effect causes objects in the lower half of the International Space Station to fall slowly to the bottom and objects in the upper half of the International Space Station to get flung slowly to the top.

[@njnear]

I really appreciate the explanation. It makes perfect sense. One small critique that may be confusing people. Isn’t the orientation of the earth wrong starting at 3:40 and 4:44? This orientation implies that the tides would be pulled towards the poles and also implies that the moon is in a polar orbit? The earth appears to be tilted by 90 degrees relative the moons orbital plane.

[@psammiad]

I once had to listen to a man talking about tides for 15 whole minutes. He was a tidal bore.

[@Neonvarun]

What the hell?

[@BertleMcGertle]

I was only a few minutes into the video before I realized I misread the tidal.

[@Jesse3beards]

You want me to call the relaxi taxi for you, psammiad? Edit: psammiad edited his comment. Don’t remember what it said originally though, sorry.

[@TheArora3]

So the old Billo was right "Tide Goes In, Tide Goes Out, nobody knows why"

[@technicaldifficultysupport]

Where did this guy go? I want to continue to watch him.

[@douglashanson7489]

@ t= 7:33 ..."The sun is more massive, yes, but it's also much FURTHER away..." correction: "FARTHER." 'farther' relates to distance 'further' relates to degree.

[@jeremymerkt3526]

Douglas Hanson You Nazi

[@Gribbo9999]

Thanks Dad. Sorry Father.

[@rowleyj31]

Under those definitions, wouldn't "further" be the proper usage since plank time is the primary unit used to talk about distance of spacial objects among astro-physicists? Miles, kilometers, and light years, or ideas of distance, are used for laymen explanations.

[@Mr.MT3]

I wonder if someone with a better understanding of gravity/water can explain this. Why does water act as one body, e.g. the oceans in this model, but other substances no? Shouldn't most things on earth react in this way? Wouldn't, at the very least, things like lava flow be nearly as heavily affected, presuming our understanding of the composition of earth is correct? If the lava is deeper within the earth and subject to more gravity, is it enough to make the differences negligible? Or would that lend one towards wondering what the origins of plate tectonics are, and if magma flow directed by the moons gravity is not what's responsible ultimately for the movement of the continents?

[@wavydaveyparker]

Hello Matt, I hope you’re not just a prankster, because you’re comment is actually quite thought provoking, so I’m going to attempt an *honest* reply, although I’ve also been known to play a few pranks occasionally, which you’ll discover if you can kindly find my cartoon on the misconception of crediting tides solely to gravitational effects. You practically answered your own questions there, because you identified the one failing in this otherwise accurate tidal explanation. The Earth is not stationary, everything has movement. Water, fluid magma, and lava all flow, and this motion has everything to do with inertia, momentum and energy. The Earth and Moon are a dynamic conjoined system. Inertia is what drives it apart and gravity is what keeps it together, and these two effects maintain a precarious balance. The Earth spins on its axis and revolves around a common centre of gravity, and this persistent motion causes internal stresses, which leads to tides, magma flows and shifts in the movement of tectonic plates. An acknowledgement for my efforts in typing this would be greatly appreciated. Many thanks

[@Mr.MT3]

@@wavydaveyparker greatly appreciate the reply! It really is all quite magnificent when you start to put it all together. A great harmony of motion. Appreciate you shedding a little more light on the matter! Definitely have a few more areas to dig into on my own to broaden my understanding here, thanks for helping paint a better picture for me!

[@wavydaveyparker]

@@Mr.MT3 Thank you so much for replying Matt, that really means a lot, as I’ve been pondering the same questions for sometime now, and you’d be more than welcome to drop a comment on my cartoon and let me know how you’re getting on, with painting a picture of the harmony of motion. I might even be able to help you with a few colours for your palette. The most amazing and magnificent thing about this avalanche of discovery, as Feynman would say, is that it all began around 300 years ago, when a young man, who happened to be hiding in the countryside, to avoid the plague in London. Happened to notice an apple falling from a tree in his orchard, and asked himself the innocuous question, “Does the Moon also Fall?” … And of course that young man was none other than Isaac Newton. Good luck with your digging my friend.

[@Mr.MT3]

@@wavydaveyparker of course my friend! Thank you for your thoughtful and informative reply! Letting you know I was actually serious about my inquiry and not pulling your leg was the least I could do! And I apologize this reply has taken some time as well, I'm something of an anti social butterfly at most times lol. But I appreciate the offer and will most definitely be dropping by your channel! I've been pondering the same things all my life as well, I think most of us have to one degree or another, but not everyone makes it as much of a focus. For me, the answers have always lead to bigger questions, and I think for you as well. It's a great thing, albeit a bit burdensome at times lol. If you don't ask the big questions, you can't answer them. Always great to meet a like minded soul. I'll definitely be dropping by your channel to say hello!

[@wavydaveyparker]

@@Mr.MT3 Hi Merry Matt, 😁 you’re more than welcome my friend, and the thoughtful reply is graciously received. I can only hope that one day, I might be able to type this response in answer to one of those bigger questions you just mentioned, when you drop by to say, Ciao! _(although, I’m not Italian!)_ Have a great day.

[@ChimeraActual]

Hmm, perhaps living by the ocean in New England made us care about this more than most, but what you said is what I was taught in high school back in the '60's. On the other hand, tangentially, we weren't taught about tectonic plates back then.

[@SpectatorAlius]

@Chimera Well no, of course not. Tectonic Plates were not yet established theory in the 1960s; it was in the late 1950s and early 1960s that "seafloor spreading" was measured and found to confirm the theory of Tectonic Plates. Before then, it was not considered well enough established to teach in schools.

[@ChimeraActual]

My poinnt. And also a tidal effect, at least partially.

[@ComandanteJ]

Hmn.... turns out you actually CAN explain that!

[@dustman96]

While I appreciate the clarification, this video was way too all over the place and fast paced to be easily understood. I think this could be presented in a much less confusing fashion.

[@saggitt]

Feel free to pause the video and think if you need to.

[@meir5740]

So much in this video was difficult to pull off and wonderfully executed

[@gavrielcohen7606]

My whole lifes a lieeeeeeeeeeee!

[@stephhill4155]

“I have over simplified this”..... I still didn’t understand a thing 🤨

[@varveklis5]

watch it again! for me, it helped :D

[@orglancs]

Nor did I. I lasted until about 5:00 and then gave up as darkness and confusion descended upon me. It would have helped if he had spoken more slowly, wouldn't it? Physicists seem quite unable to explain things to those of us with no feeling for the subject. I have never been able to follow a single explanation by a physicist to the end. I would just love to understand basic physics.

[@deusexaethera]

Cliffs: The Moon's gravity isn't _pulling the ocean up,_ it's negating some of Earth's gravity in the high-tide regions so the full force of Earth's gravity in the low-tide regions can _pull the ocean down._ Furthermore, the Moon's gravity is pulling down-and-sideways on the water in the low-tide regions, reinforcing the Earth's gravity in those regions. The displaced water has to go somewhere, so it flows into the high-tide areas where Earth's gravity is weakened by the Moon's influence. Lakes, bathtubs, and cups of coffee don't experience tides because they aren't connected to any reservoirs of liquid elsewhere that are experiencing a different gravitational force, so there is no flow of liquid from one location to another.

[@quixotic7460]

Comparing the tides to a pimple is a first, i gotta say. Props for creativity, Gabe! The pimple-tide is stuck to my brain forever

[@cryvsspy]

the explanation at the 5 minute mark is wrong. The side of the earth opposite the moon would not be repelled by the moon, just attracted less.

[@somerandomdude5237]

From what I understand with the example from the video, the explanation at the 5 minute mark is not wrong, it's showing the "tidal acceleration" in reference to the center of the earth. NOT the acceleration. So yes I think you're right in saying it is "attracted less" but from the reference of the center of the earth it "looks" like that far side is accelerating away, which is called tidal acceleration which he explained earlier. That's how I understand it at least :)

[@MikeRosoftJH]

+cryvsspy Well, yes and no. The Moon's gravity accelerates the oceans on the side closer to the Moon more than the Earth itself, and the oceans on the far side less than the Earth. (Here we assume that Earth [minus the oceans] is rigid, so Moon's gravity doesn't deform it - it just uniformly accelerates it.) The observer on the Earth will see that the oceans on the near side are accelerated towards the Moon, and the oceans on the far side are accelerated away from it; he can describe this acceleration as a fictitious tidal force. (Likewise, the centrifugal force is a fictitious force - in an inertial frame it doesn't exist - but its effects are very real.)