What Physics Teachers Get Wrong About Tides! | Space Time | PBS Digital Studios
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We all know tides have something to do with gravity from the Moon and Sun, but if gravity affects the motion of all objects equally, then how come oceans have large tides while other bodies of water don't? It's because your mental picture of the tides is probably WRONG!!! Join Gabe on this week’s episode of PBS Space Time as he sets the record straight on tidal force, gravitational differential and what role the moon actually plays in tides. Why don't lakes have tides? Watch the episode to find out!
Emily Rice (NASA Space Apps Challenge talk on Exoplanet Atmospheres):
• Space Apps NYC 2015 - ...
about.me/emilyrice
Sean Carroll (lecture notes on general relativity):
ned.ipac.caltech.edu/level5/Ma...
For Additional Info on tides:
• The Tides • Tides: Crash Course As...
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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.
***** 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?
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.
***** I stand enlightened.
***** 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)?
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 TH-cam channel and I love it, but it's kind of hard to get noticed these days. I do what I can.
awesome to see so many people updating their knowledge based on new information and not being salty about it
Haha every huge physics YT channel creator is here ^^
I don't get why there are some many dislikes. On a learning channel you're supposed to learn new things.
TH-cam being TH-cam, I guess
That is the Way
@@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.
@@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.
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.
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.
If gravity is the curvature of space-time, then is it the change in this curvature that accounts for the two high tides on opposite sides of the earth? He keeps saying the "Pulling Down" of gravity on the earth is weaker on both sides where there is a high tide, but in other videos he says gravity is space-time and is not a force that pulls? How does the moon affect the low earth orbit on the space station then?
Yes, too much fast talking here, & in many other, otherwise, good online presentations. But, voila, TH-cam 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 :)
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????????????
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.
@@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. 😞
@@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.
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.👆
@@from_nowhere 🤣🤣. Thanks for the clarifications, and HNY to you, too.
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!
That's what I admired the most about this channel. I feel like they don't do that as much these days.
@Science Revolution 🤡😂😂😂😂😂😂😂😂😂 Man. This is some next level cognitive dissonance.
6:53 "A human is basically a big sack of water" I had to pause and look at the wall for a few hours
This is the first time I’ve ever seen anyone outside my family talking about having to look at a wall in contemplation.
@@jadely77 maybe we are related
Even the human body is affected by the moon and the sun.
A walking mudball if you want to be technical.
@@GandharaBlogspotCa I'm squeezing.
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 😅
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 😅
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.
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.
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."
+Michael Block I agree, this guy was great. I don't know why they felt the need to get a new host.
+Michael Block Well he might just have a script, right?
Duh.Really?:)
+Michael Block Checkout 10:45
That cracks in voice proves he is human like rest of us👀
"Everything I just said is oversimplified" I didn't understand a word you just said. I've never felt so stupid.
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.
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.
🤣🤣🤣🤣🤣🤣😂😂😂😂
@@trishulsolanki5298 this is ok boomer material
welcome to science, the more stupid you feel, the more you are learning.
Man , forced staying home really gives the possibility to learn things. Thanks!
And PBS has the good stuff!
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.)
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.
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.
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!
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!
@@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)
@@Amamos If gravity is the curvature of space-time, then is it the change in this curvature that accounts for the two high tides on opposite sides of the earth? He keeps saying the "Pulling Down" of gravity on the earth is weaker on both sides where there is a high tide, but in other videos he says gravity is space-time and is not a force that pulls? How does the moon affect the low earth orbit on the space station then?
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.
@@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!
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.
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.
@@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!
@@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.
@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.
@@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.
I liked when you talked about the nooks and crannies having larger tides. It's comparable to what makes the windy city so windy.
This confirms what I've thought for a while: fluid dynamics is frickin weird.
SafetySkull mindblown
Noah Fence fluid dynamics is one of the main reasons super computers were build, so you could not be more right.
Jaime Duncan I don't quite see the difference between "supercomputers" and something like say, Colossus. Surely it was "super" for its day?
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?
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.
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.
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!
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!
@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.
Bill O'reilly should watch this.
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!
ex3jets Never a miscommunication!
Science goes into one ear of Bill O'Reilly and out the other... You can't explain that!
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!
Mark G JAJAJAJA
You're a guy on the internet who talks quickly and briefly about things I'm not involved directly in at all, most if my friends aren't interested, but have always had an underlying interest. Point being I've no reason to be influenced by your life, yet I'm really gutted that you're leaving PBS Space Time. I really enjoy these vids bro, they're fast enough information to challenge me when taking it in and I rarely get that in day to day life now. You're pure information and no fluff, that's becoming impossible to find these days. I missed it till I found these videos and will again once you're gone. I guess I'm just trying to say thank you. :)
I have waited for that video for years! Thank you!
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.
I wish there was a channel like this for biology!
Nooooooo Khan Academy is nowhere near as good man. I want discussions, not lectures. 🤕
check out this channel
AK LECTURES
"minute earth" is a great but different option for life sciences.
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.
look up "crashcourse biology"
I didn't realize my understanding was so ridiculously far off. Noted.
POWERBUT You always know how much you know less than how much you dont know; you know?
POWERBUT good thing my understanding not far off...
Do you want to know how far off 99 percent of people are off. click my name to watch part 8
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!
@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.
@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!
Excellent! Just about the only correct explanation I’ve seen on TH-cam. 👍🏻
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.
I only discovered this channel after this guy left. :(
He's like Carl Sagan on hard mode.
left? really? why he left? idk about that
@@fruit21orn-imsin12 3 year old comment just cracked me up! xD _"He's like Carl Sagan on hard mode."_
He is like Carl Sagan without the frustrated know it all attitude
Matt is way better. This guy's voice is annoying.
Well, I prefer Matt.
Darkest eye circles I’ve ever seen. That’s how you know he’s legit.
I've been misunderstanding this totally. Thank you!!
just found a new channel to binge watch.. time to blast off.
"Tide goes in, tide goes out. Never a miscommunication. You can’t explain that. You can’t explain why the tide goes in.”
Bill O'reilly jajajaja
Bobby Harper making sure this was here
Bobby Harper Food goes in, poop comes out. You can't explain that.
Bobby Harper I think the reason why tide goes in is gravity of the earth pulling back the tide, i may be wrong
thewarri0r9 We're having fun with a Bill O'Reilly statement about tides.
Awesome. Thanks for the insightful clarification!
So much in this video was difficult to pull off and wonderfully executed
This is gonna go right over my head.
But I'm watching it anyway.
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.
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.
I live in California Bay Area and I agree.
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.
I miss these early spacetime vids!!
This video contains one of the best explanations for tides I have read. Thank you.
After about five and a half minutes into this video I decided that tides aren't important enough for me to understand.
shoesheep 🤣😂🤣😂
@M Detlef
Nah...you'll simply have a dead person who didn't understand tides drowned by a bunch of fools who did! 😜
For me its 3 and half.... Btw cmnt👌
🤣🤣🤣🤣
A simulation gone amuck.
On the water, understanding ties can be the difference between life and death. Very important if you are a sailor.
I took up sailing as a hobby and wanted to know about tides and why they happen. This was an excellent explanation. Thanks!!!
Very enlightening! Thank you!
*adding to Watch Later for when I'm caffeinated enough to understand this*
While he is talking, time appears to speed up. Is this because he is talking so fast?
Everyone: talk too fast
No one :
Me : doesn't notice a thing because slowed it down to 0.9x
I was watching on 2x speed, so it was actually faster for me.
It's time dilation
Fantastic explanation! Thanks man.
Thank you for such a simple and clear explanation.
Tide Goes In, Tide Go out, can't explain that
+MrBenny10101 He just did.
+Aaron Cruz he is making fun of bill o reily..lol
bread goes in, toast comes out, you can't explain that
Tide goes in, stains come out !
Never a miscommunication.
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.
Thank you! I actually understood this.
I have heard this global tidal explanation on other YT channels and your rendition is definitely the best and makes the most sense! BTW, you have a new subscriber! 👍👍👏👏
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.
No trigger warning and now I'm back on the pods.
Thanks, very well done!
Super awesome! I had no idea. Thank you
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.
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.
This is like my fourth time watching this video over a few years and this is the first time I actually understand it lmao
52 is a magical age
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.
Thankyou it was great to learn with you 😊
The tidal bore in st. John New Brunswick is truly amazing to watch they call it reversing falls
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.
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.
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.
I remember my teacher kinda skipping the part about the other bulge. They'd kind of gloss over it.
Very complete and detailed!!! 👏👏👏👏
There’s an even more detailed account of this same approach in the OTMS-2 video on my channel, if you’re interested in such things.
Thank you for your video.
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?
@@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 👍
@@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).
@@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
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!
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.
thank you for the video i really understand how tides form
I'm always happy to learn new thingsand I definitely learned something new by watching this.
0:38 Kurzgesagt!! but they never made a video about tide.
+Mobashshir Feroz I was going to say the same. I love Kurzgesagt. And that is how they animate the planet, haha. :v
Humano InHumano Well and their recent animating skills have improved exponentially. and there theme music is just in my head, all the time..
+Mobashshir Feroz only bad thing is that Kurzgesagt has less videos, although they are very good.
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.
Incredible delivery and very interesting
I loved this video! I just want to see this concept of how waves worked transferred onto other celestial regions, such as bullet clusters and pulsars!
3:52 I love the animator of this. The Fluttershy and Rainbow Dash cameo was a nice touch.
cortster12 Ponies are the new apples in explaining physics.
cortster12 He's great, right? Michael Leng, here at Kornhaber Brown.
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.
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
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 =)
Ok it took a while but I finally got it!
This guy explains it better:
th-cam.com/video/58XQxj6o5RY/w-d-xo.html
@@RevolutionibusOrbiumCoelestium dude, thanks for that! This is legit a much better explanation
@@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.
you are a legend, thanks for clarifying
Very good and very interested. Thanks.
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.
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.
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.
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.
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.
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.
@@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? 🤔
@@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.
@@perseverancerover I totally understand. I wasn’t expecting this speedy reply. I’ll check that out. Thanks.
Awesome explanation! I learned something new!
Awesome comment! But, would you like to enlighten us to the something ‘new’ you learnt?
@@perseverancerover Um, I learned about what the entire video is about? That tides are about squishing, not pulling. Isn't that the point of this video? To explain that aspect of tides? That's what I learned.
@@eepruls Thank you so much for taking the time to reply with such a thoughtful comment. And, Yes, that is essentially the correct message to takeaway from this video, concerning the tides! 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 for tidal calculations, because the resultant accelerations there balance to zero!
So, I hope you found this interesting and will add it to the ‘new’ things you’ve learnt? Unless you knew this already and I’ve just wasted my time typing. Kind regards.
Best explanation of tides I have found on TH-cam.
I know an even better one 😃 check out Tribus Montibus Oceanography
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).
Please kindly have a look at two comments I posted a couple of days ago ... It might interest you.
You two are insane
Tide comes in, tide goes out... you can't explain that 🤣
Problem is you forgot the rotation of earth. Otherwise you should have already understood
My daughter was having a hard time getting this at school. She now gets it thanks
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
Anyone sent this to Bill O'Reilly yet?
awAdmin EARTH IS FLAT EXCEPT JESUS BILL OREILY IS A PROPHET WILL NOT LISTEN TO THESE LIES
@@gogglesow1358 You're joking right?
Can't explain that
Amazing explanation. It feels like some day, "high school" will just be a well curated TH-cam playlist.
And then Covid happened and your comment came true.
@@tocodelray Hah. Well spotted.
I just learned something new. I did once hear someone mention something about surface area, but I interpreted it differently.
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.
I just realized I've spread so much misinformation by explaining tides wrong.
Thank you so much for clearing this up.
.hes wrong also.
He missed the gravitational offset of the focus of earth's gravity due to the moon. It is actually very important.
It's a popsci channel pretending to be more what did you expect.
I already saw some pretty good tidal explanations, but yours is the clearest and easiest to get without getting into gory math :-)
That was neat. I liked it.
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.
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.
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?
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
@@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!
@@merryprankstermatt 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.
@@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!
@@merryprankstermatt 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.
i just realized the tide concept is misunderstood by many people, thanks man!
I don't completely understand this, but this is the potential of the internet. Thank you.
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.
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.
wow. that was mind blowing for me. like you said, lots of people had misunderstood it, incudling my science teacher.
Thank you very much! Gorgeous!