Moon's gravity alone cannot create the world's largest tides

Jan 20, 2014 by Andrew Steele, The Conversation
How long can you stay there depends on practice and physics. Credit: elisfanclub

"Tide goes in, tide goes out… you can't explain that." So claimed US talkshow anchor Bill O'Reilly, in a baffling attempt to discredit atheism which became something of a YouTube sensation.

I have been on holiday to Brittany a few times and I was aware the tides there were enormous – but, when I looked into why, I discovered that the reality is even more fascinating and complex than O'Reilly failed to grasp.

Tides around the world can range from almost nothing to over ten metres – so how can the Moon's gravity alone give rise to such a diversity of tides?

Well, it can't – at least, not on its own. The Moon's gravity is strong enough to cause Earth's oceans to oscillate, but it can't account for the the variety of tidal ranges observed. These variations are caused in large part by the physics of waves.

You can think of tides as enormous waves rolling around the circumference of the Earth. The interplay between these gargantuan oscillations, rebounding from continents and interacting with one-another, can allow for huge differences between local tides. The large tidal range in Brittany, for example, is due to a tidal resonance – the cumulative effect of adjacent tidal waves perfectly in sync. If you want to learn more, it's explained in this video:

This video is not supported by your browser at this time.

Tides are also responsible for a host of excellent epiphenomena. For example, the Severn estuary in the UK plays host to the inaptly named Severn bore, which is anything but: a solitary two-metre-high shock wave which glides with an eerie smoothness for twenty miles up the river. Or there is Bodø in Norway, home of the world's largest tidal maelstrom, where the tide rushing through a narrow channel forms tumultuous whirlpools.

"Time and tide wait for no man", or so the saying goes – and there are few more potent everyday examples of the power and indifference of nature. The advance of a spring tide up the Plage Bonaparte (the beach featured in the video) has often left me in awe. And, occasionally, sprinting with armfuls of cricket stuff and deck chairs to avoid them being claimed by the sea.

And if you want to experience the power of tides, I recommend standing in the sea and letting the tide rise up from your feet to your neck. Just make sure you know your physics – pick the biggest tide of the year on a beach with one of the world's largest – or you may find yourself waiting for quite some time.

Explore further: Island channel could power about half of Scotland, study shows

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no fate
1.3 / 5 (4) Jan 20, 2014
The title of this article is beyond accurate. Anyone curious can check out tidal motion "dual bulge" and try explaining it gravitationally. For those who don't know (I didn't until fairly recently) there are always 2 tidal bulges directly opposite of each other on the earths surface moving in unison like two blades of a fan mounted at 180 degrees.
antialias_physorg
4 / 5 (4) Jan 20, 2014
So....tidal engineering? Concentrating tides in select places for powerplants while at the same time making other places safe(er) from extreme (spring)-tides?

Probably much too costly to implement. But would be a nice excercise for fluid mechanics majors.
Jeffhans1
5 / 5 (3) Jan 20, 2014
Our Atmosphere and Magma layers also experience Tidal forces.
Nestle
1.8 / 5 (5) Jan 20, 2014
There are still [http://www.pressh...-31.html]many anomalies[/url] hidden in the tidal physics. In particular, the connections to planetary conjunctions and collinear Earth–Moon Lagrange points may exist there.
nkalanaga
5 / 5 (3) Jan 20, 2014
One also has to consider that only 2/3 of the tidal force comes from the Moon. The rest is due to Solar gravity, and the Moon and Sun seldom pull in the same direction. Most of the variation in tides at a given location is due to their interactions.
Returners
1 / 5 (5) Jan 20, 2014
O'Reilly was talking about something a bit more fundamental than the mathematical relationships of gravity. Dawkins and his side don't even get that though, as they seem to believe he actually said something wrong.

A mathematical relationship is not the same thing as a fundamental causal mechanism, just as saying, "The universe exists," is not the same as talking about why or in what way or how it exists.

Set theory easily disproves Lawrence Krauss and Dawkins on the "E + negative E equals zero" crap.

There is no process, "P," which could be in the set of nothingness, which would be capable of transforming nothingness into the set of existence, and for two reasons:

1, The set nothingness is an empty set, so P cannot be there.

2, The set of existence is everything that is real, so P must be there, always.

Since P is required to be initially in nothingness to make Krauss' position true, but it cannot be in nothingness by definition, then he is easily proven wrong.
Nestle
1 / 5 (3) Jan 20, 2014
IMO the random state is the natural state of existence. The nothingness or static state is artificially leveled flat zero state of reality. Why just zero state? Why not ten or twenty?
Whydening Gyre
5 / 5 (4) Jan 20, 2014
Set theory easily disproves Lawrence Krauss and Dawkins on the "E + negative E equals zero" crap.
There is no process, "P," which could be in the set of nothingness, which would be capable of transforming nothingness into the set of existence, and for two reasons:
1, The set nothingness is an empty set, so P cannot be there.
2, The set of existence is everything that is real, so P must be there, always.
Since P is required to be initially in nothingness to make Krauss' position true, but it cannot be in nothingness by definition, then he is easily proven wrong.

unless you consider that a set of nothing must be a part of the Set of Everything...
by definition, of course....
Whydening Gyre
5 / 5 (1) Jan 20, 2014
IMO the random state is the natural state of existence. The nothingness or static state is artificially leveled flat zero state of reality. Why just zero state? Why not ten or twenty?

Not exactly sure what you're getting at here, but I think it has relevance somehow...
Nestle
2 / 5 (4) Jan 20, 2014
For example, for surface ripples the water surface appears void and empty, not because no molecules exist there, but just because its molecules are randomly arranged. If some regularity or deviation from random state appears there, it manifests itself itself like the density fluctuation, which is scattering the surface ripples, thus serving like the obstacle - and the surface isn't void anymore. The pure random state of highest entropy is indistinguishable from emptiness in this perspective.
Whydening Gyre
5 / 5 (1) Jan 20, 2014
The pure random state of highest entropy is indistinguishable from emptiness in this perspective.

This makes perfect sense. However, someone will say prove it. But, any attempt to do so would violate that state, thereby invalidating the premise... interesting...
cantdrive85
1 / 5 (3) Jan 21, 2014
There are a number of anomalies associated with gravity, such as the "fly by" anomaly;
http://www.scienc...1111.htm
antialias_physorg
5 / 5 (3) Jan 21, 2014
collinear Earth–Moon Lagrange points may exist there.

What are you babbeling about? Earth and Moon are always colinear. And teh Lagrange points of the Moon Earth system are where they are. You don't get additional ones due to tides, because they are caused by the exact forces that determine where the other Lagrange points are.

Pick up your game, Zephyr.
ScooterG
1 / 5 (3) Jan 26, 2014
""Tide goes in, tide goes out… you can't explain that." So claimed US talkshow anchor Bill O'Reilly, in a baffling attempt to discredit atheism which became something of a YouTube sensation."

And this is a baffling attempt to discredit O'Reilly.
Captain Stumpy
5 / 5 (2) Jan 26, 2014
@ScooterG
...in a baffling attempt to discredit atheism which became something of a YouTube sensation."


this is a baffling attempt to discredit O'Reilly

i am not sure where you are going with this...

O'Reilly was effectively refuted by Dr. Neil deGrasse Tyson with Dr. Tyson's video here

https://www.youtu...kg4hMRjs

it appears to me that this article is perhaps an explanation because there are others out there (including new earth creationists) that believe as O'reilly said, therefore the explanation must be shown
especially given the incredible lack of scientific literacy in the US.

This article defines what happens in an easy to understand presentation that is effective and supported by plenty of science...

did you watch the above video?

it is quite good