How do Tides Work? How does the Moon Cause the Tides?

Here we will discuss the cause of the ocean tides. A rising tide is when the water level rises, and a falling tide is when the water level goes down. We call this the tide coming in and the tide going out. The tides on Earth are caused by the gravitational pull of the moon. On the side of earth facing the moon, the ocean feels a stronger force of gravity than on the far side of the Earth. Since the gravitational force is an inverse square law, the difference in gravitational pull is very different on opposite sides of the earth. This causes the oceans to bulge, and this is what we notice as the tides on earth. There are two tides per day because the moon's gravity causes two ocean bulges on Earth.

[pre-faelliteray]

The Earth is neither static nor accelerating in a straight line motion. Imagine firing the Earth and Moon from two huge cannons and watch them both *orbit* around their common centre of gravity and you’ll have the correct answer to lunar tidal formation.

[wavydaveyparker]

When Issac Newton first proposed the theory of Gravitation in his _‘Principia’, _ around 300 years ago! He unfortunately, neglected to give us the mechanism by which _‘gravity’_ worked! However, he did provide us with some very beautiful and simple equations, to correctly calculate the movement of Planets. His problem started with his acceptance of _‘absolute time’_ and distinguishing the difference between _‘gravitational’_ and _‘inertial’_ mass, which he considered to be equivalent, but being the genius he undoubtedly was, he agonised over that conclusion and knew it might not be completely accurate.

It wasn’t until Albert Einstein around 200 years later, that we were finally given the more complete answer to gravity, when he told us that the natural state of things is _‘free fall’_ ... and the _‘mass’_ of an object had the potential to curve the space around itself, within the confines of his proposed idea of _‘spacetime’, _ which he presented in his brilliant theory of General Relativity.... _I hope that helps?_ 🙃

As for the tides... well, they’re not that difficult to understand really? Think of it like this... At the very centre of the Earth, there is a centripetal ‘force’ of gravity pulling it towards the Moon... And there is also a centrifugal ‘force’ _(I use the terms loosely, because they are ‘apparent’ forces in an inertial frame, but the Earth-Moon system is definitely a revolving, non-inertial frame and they exist)_ due to the inertia of the moving objects wanting to continue in straight lines!

These two effects ‘balance’ according to Newton’s Third Law and the orbits continue, because the ‘net’ forces at there centres are zero. The centres of the Earth and Moon are indeed moving on spacetime paths, and don’t experience a net acceleration, because they are in *free-fall* around their *barycentre, * but still under the influence of a non-uniform gravitational field.

When we work out the tides, we use the ‘tidal force’ equations, which effect an object from the *centre* outwards.

Therefore, ‘No!’ pulling, or tugging away from oceans or moving towards the moon filling up bulges is necessary. Just the knowledge to realise that the Earth-Moon system operates like any two-body problem.

Of course, we then have to correctly apply the method of resolving these associated acceleration vectors into there respective components and recognise the buildup of sideways pressure in the underlying water column, which is what actually drives the tidal systems, but that’s not my particular area of expertise?

Take care and thank you so much for a valiant attempt to explain the tides and leaving so many questions unanswered?

Regards Wavy 👋.

[annettelupau]

As the Earth rotates around the barycenter of the earth/moon system, a "sloshing" of the water causes additional tidal forces on top of your description.

"sloshing" - I couldn't think of a better word at this time. LOL

I am glad, though, that you did not talk about the full moon some how causing higher tides. LOL That one always gets me laughing.

[richardplinston]

He does not appear to know that there is a Barrycenter for the Earth-Moon system. That is the Moon is not orbiting the Earth, both are orbiting the Barrycenter which is some distance from the Earth's center (but still inside the Earth). This causes a centrifugal force that is greater on the side away from the Moon and less on the side facing the Moon.

[bazsnell]

Gravity is NOT a Force!!
There are numerous YouTube proper science and physics channels explaining this.

[bassline]

This video isn't only a lesson in how tides work but it would be an incredible instruction video for future teachers. This is how you explain stuff.

[josemariatrueba]

Nice, but your enthusiastic and convincing explanation of the very complex fenome of tides is wrong, because there is a very important couple of things missing...

1. Moon does not orbit around the earth, but moon and earth are BOTH orbiting around their common center of gravity, their common baricenter, located much closer to the center of the earth than to the center of the moon because the moon is lighter. Galileo was not exactly right, nor was everybody else arguing him in those days becsuse bith sun and earth are orbiting around their common baricenter too.

2. The Newtonian forces of gravity between moon and earth are unable to be felt because they are exactly counteracted by the fact that both celestial bodies are in orbit, same as the weight of an astronaut of the ISS cannot be felt, even if it's still pretty strong at an altitude of arounds 400 Km because his or her weight up there is as high as an 80% of the astronaut weight at he surface of the earth. Gravity is there but cannot be felt, nor the vectors pictured, because the astronaut's weight (force of gravity) seems zero counteracted from the force of spinning at a fast angular speed of one turn in around a 90 minutes period orbit.
The force of gravity between moon and earth of course does exist, but appears to be non existent because it's counteracted by the fact that both moon and earth are in orbit spinning at an angular speed slower than the ISS, of one turn in a period of those mentioned 27 days.

There is one thing that should not be mentioned when explaining tides which is the force of gravity between moon and earth, because luckily this force is counteracted by the centrifugal force coming from the fact that both moon and earth are spinning in orbit.

Precisely is the same centrifugal force that drys our clothes in a washing machine what nullifies the gravity between earth and moon, thank goodness!
Because otherwise the force of gravity applied to moon and earth would cause an initial acceleration excerpted to both moon and earth resulting in a movement at an increasing speed.
An instant later the distance between moon and earth will be smaller resulting in a new force of gravity stronger than before, causing a stronger acceleration until moon and earth will collapse in a very small amount of time.

You have been using the force of gravity between moon and earth, picturing those vectors when this force should be removed from the explanation.... thank goodness!

I think that it would be worth to try a new enthusiastic explanation. I do like your style. Go ahead!

[Nightcrawler]

Dr. JASON,
you are such an extraordinary professor. You explain complicated subjects in a very understandable and practical manner. You make difficult things very easy to understand. You are truly one of a kind. You are a legend.
We love you.

You are unbelievably a great professor.

Thank you thank you

[hossainalomgir]

Dr. Jason, I'm 55 and used to be a science enthusiast. Entering into arena of science again to recall what i have learned in school. You are the best science teacher i ever had. God Bless!

[bucs]

The passion of this Engineer is mind blowing, the details of the way things are explain are second to none. This man not only has full knowledge on the matters he teaches, not only he explains in very absorbable way, but he loves what he does. I believe in Engineers; can't say it enough: It is a pleasure, Sir!

[anthonygregg]

Thankyou sir for an amazing lesson. I am so much more interested in science as you explain things so well.

[baker.marafat]

I listen to you the whole lecture and I agree with you 80%
my name is Baker and I am from Jordan but I am living in Illinois right now the part which doesn't resonate with me is the bulging at the opposite side of the earth I actually agree about what you illustrate about the victors in deferent directions and all that and then you assure the bulging from the other part is real no doubt about it, so if that is the case then I would say the reason because the water pulled out as a conic shape due to the gravity of the moon then there was a drop of water at the north and south poles let us say a kind of water vacuum happened at these poles left the other part of the ocean loosely connected, and with the power of the centrifugal force of earth rotation give good chance for the water to be pulled away from the earth causing that opposite bulging this is my prospective . So what you think?

[tajudeennuhu]

Wonderful, your lessons make me more inquisitive about learning. Thanks!

[siddhantkohli]

Dr.Jason, one of the best teachers I have come across on this platform, I want to thank you for the efforts you do in your simple sweet yet inclusive videos . Keep it up professor

[betaorionis]

Excellent job, very well explained. But it’s going to be difficult to understand for people without a certain knowledge of physics and vectors.

[matselmgren]

The moon does not go around the center of the earth. The Moon-Earth system goes around a common center of gravity. This is located at a point on an imaginary line between the midpoints of the moon and the earth approximately midway between the midpoint of the earth and the surface of the earth. Around this point the globe rotates once a month. This rotation creates, via centrifugal forces, a "water bulge" on opposite sides of the globe. The bulge that is directed towards the moon becomes extra high due to the gravitational pull from there.
These two tidal waves orbit the Earth due to the Earth's rotation. Time The size of the water depends, among other things, on the depth of the sea and the appearance of the coasts. When the tidal waves are pushed into the wedge between England and France, the tide can vary by up to 10 m in extreme cases (when the sun's gravity also cooperates in the race)

[leonardkipngeno]

Am not convinced with the last explanation, how do the vectors go backwards, I think let's just use the simple explanation of centripetal and centrifugal forces, and bulging on the other side, as the distribution of the same force acting contralateral, though I don't know if it Will be okay. This might make sense if you will think about the water, if the earth would move faster on its axis.Think about.This might make the bulge on the side of the moon abit bigger than on the contralateral side as well, since the moon, exerts some little pull.So my big question in this, particular explanation is why are the vectors going backwards, to the direction of the moon's pull? Kindly.

[eugenepluta]

I always thought the buldge on the opposite side of earth was the result of tidal forces exeterd by the sun. Had no idea vector forces are at play. Once again, blew my mind!

[HomeMadeBoards]

YouTube's great father, that every kid wanted and needed, thank you Jason 👍

[juliocesarugarteliborio]

You are great in explanation!
I wish I had someone great like you to teach me when I was young. Would be more interesting to learn more mathematics and physics. 👍