The tide doesn't rise and fall!

[srm]

But he's not talking about the fine detail such as tidal waves in the North Sea, but the overall vertical movement which generates, and provides a context for, such local phenomena.

The two - bulges at earth scale and local scale amphidromic points - are not incompatible, they are interrelated.

Having watched the video again I still see it as using the gross oversimplification that is often used to introduce the concept of tidal forces. I have used it for around 25 years as an educator in Maritime Studies. But always with the explanation that it is only applicable on a water world. Then move on to some of the complexities generated by our real world. The tide does go in and out at a given location because on our world the simple bulges do not exist. Tidal forces and the shape of a basin create waves rotating around a local or oceanic scale amphidromic point. There is no simple bulge for us to move into and out of as the planet rotates.

Perhaps the video is an astrophysicist using a poor analogy while trying to make a point about words and language being a simplification as in his final "sunset" comment about one word encompassing a complex set of ideas.

 

[doug748]

I can't see how any of it is possible as the earth is flat ?

Ah, does not matter if the earth is flat or round. Here is proof; boat sailing on a rising tide:



.

 

[boomerangben]

if we agree that tides are caused by the moon and the sun and that the sun and moon only move a relatively small amount relative to the earth between two tides, then how can we question the video?

it doesn’t explain tidal currents, but then it does set out to do so

 

[servus]

Hello there,
Possibly I have missed out some really crucial detail..... but the most interresting part of this very discussion is, how much well intended, educated and honestly thought through response one can trigger by putting some peculiar hogwash - originally formulated, I must admit - into circulation.
Reminds me of the climate discussion, the miraculous multiplication of genders, flat earth etc.
Of course we all know, that the earth is a globe. The misconception is that we live on its outside. We live on the inside! Proof: our shoesoles wear off at toe and heel and not the middle....

 

[RunAgroundHard]

... how can we question the video?

The water molecules that form the bulge are not the same molecules all the time. The water molecules change as the water is in general terms stuck to the surface of the earth. Hence the water molecules must flow. Just like iron filings flow into a magnet held above the pile. The force that causes the bulge is always there but not the water molecules, they change.

 

[RunAgroundHard]

... We live on the inside! Proof: our shoesoles wear off at toe and heel and not the middle....

I have club foot, or rather my heal and toes do not exist. My shoe sole wears in the middle.

 

[servus]

I have club foot, or rather my heal and toes do not exist. My shoe sole wears in the middle.

That would be the exception proving the principle.

 

[LittleSister]

Having watched the video again I still see it as using the gross oversimplification that is often used to introduce the concept of tidal forces. I have used it for around 25 years as an educator in Maritime Studies. But always with the explanation that it is only applicable on a water world. Then move on to some of the complexities generated by our real world. The tide does go in and out at a given location because on our world the simple bulges do not exist. Tidal forces and the shape of a basin create waves rotating around a local or oceanic scale amphidromic point. There is no simple bulge for us to move into and out of as the planet rotates.

Perhaps the video is an astrophysicist using a poor analogy while trying to make a point about words and language being a simplification as in his final "sunset" comment about one word encompassing a complex set of ideas.

I don't understand why you have a problem with what he says, and want to complain he is wrong. He is not wrong, and he is not contradicting any of the detail that you mention and are interested by. Contrary to what you said, he is not making a point about words and language, but about perception. He is offering you (and all of us) us a new perspective on tides to complement and expand, not replace, your (and our) existing knowledge.

It's not a gross oversimplification, because he is neither aiming nor claiming to explain everything about tides, but pointing out one of the fundamentals of them which is often overlooked.

A child would say the tide goes in and out. You and I would say the tide goes up and down (without denying that results in it going in and out from a sloping shore.). He is saying that on a global scale the tidal bulges aren't going up and down (without denying that locally it goes up and down and in and out and round and round), but the rotating Earth's surfaces (and we on them) are moving with respect to those bulges, which in broad terms are 'fixed' facing and opposite the moon.

Like you, I am fascinated by the complexity of the tides, and all the factors that go to make and vary them. The author of the video is also someone who delights in understanding, and explaining, the complexities and the regularities.

 

[johnalison]

He was not offering a different explanation for tides but only pointing out what tides look like if you change your frame of reference from that of us on the Earth to someone else on the Moon or elsewhere. He also manages to do this in a minute or so.

 

[mjcoon]

He was not offering a different explanation for tides but only pointing out what tides look like if you change your frame of reference from that of us on the Earth to someone else on the Moon or elsewhere. He also manages to do this in a minute or so.

And just when we have only recently got used to the idea that the Sun does not zoom across the flat Earth...!
;-)

 

[LittleSister]

And just when we have only recently got used to the idea that the Sun does not zoom across the flat Earth...!
;-)

What will they think of next?

 

[johnalison]

And just when we have only recently got used to the idea that the Sun does not zoom across the flat Earth...!
;-)

It does when I am in my garden. Horse for courses & all that.

 

[AntarcticPilot]

He was not offering a different explanation for tides but only pointing out what tides look like if you change your frame of reference from that of us on the Earth to someone else on the Moon or elsewhere. He also manages to do this in a minute or so.

Another factor is that the pure, gravitational tide only occurs in the middle of oceans in deep water. That tide is not very great - I don't have exact figures, but it's around a metre, and the water movement is almost entirely vertical. The tides we all know and love are the effect of the gravitational tide coming into shallow water and being amplified by the shape of the basin, shallowing water and various resonances - if the natural resonance of the basin happens to be close to the astronomical periods then you get big tides - same effect as if a basin of water starts to slosh as you carry it; if your steps are in time with the period of sloshing, the basin overflows!

 

[jamie N]

The esteemed and popular scientist is ignorant of the truth as he's never sailed on the Pentland Firth.

 

[Frank Holden]

if we agree that tides are caused by the moon and the sun and that the sun and moon only move a relatively small amount relative to the earth between two tides, then how can we question the video?

it doesn’t explain tidal currents, but then it does set out to do so

You've been reading too much Bowditch. In the Anglosphere they are surely tidal streams.
I blame Benjamin Franklin and him naming the Gulf Current the Gulf Stream.

 

[rotrax]

The OP needs to tell the residents of the West side of Littlehampton that the tide does not rise and fall.......................................................

It 'kin well rose a bit above normal during the last two high tides!

The yard, workshops and office at the Hayling Yacht Company flooded too!