Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: bobdihi on 09/06/2018 17:48:16
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How big the body of water must be to experience notable low and high tides?
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Notable tides, by which I assume you mean larger than average, are the result of local geography. Often due to a funneling effect which concentrates the water flow eg Bristol Channel in UK. Also due to resonance effects eg Bay of Fundy USA.
Most areas also experience higher (& lower) tides each month when the sun and moon work in cooperation (or opposition). See spring and neap tides.
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Possibly "notable" = observable/measurable (?)
I've no idea of the answer in that case, but it would differ from Colin's.
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That will depend on the gravitational gradient involved. A droplet of water will experience very significant tides as it nears a small black hole.
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It's all a matter of geography. The middle of the Atlantic scarcely experiences any tidal range at all, but it's several thousand miles wide, so an inch fall in the middle will produce a 30 inch rise in the English Channel. That said, the entrance to the Mediterranean is also narrow but the Med is much bigger than the North Sea, so the tidal range around Italy is negligible - hence Venice is a very different city from Southampton!
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Possibly "notable" = observable/measurable (?)
I've no idea of the answer in that case, but it would differ from Colin's.
Ok, let’s go with that definition.
Tides will occur in any body of water - even a bathtub - but the size of tide depends on the length of the body of water. Looking at a practical example, NOAA have studied the Great Lakes and true tides (changes in water level caused by the gravitational forces of the sun and moon) do occur, however, the spring tide is less than 5cm. These minor variations are masked by the greater fluctuations in lake levels produced by wind and barometric pressure changes. So the Great Lakes are considered to be non-tidal.
The Mediterranean is also considered non tidal but can have up to 1m tides due to local funnelling effects, usually much less eg 0.3m.
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The effects of the tides can be seen in bodies smaller than 1cm across: marine invertebrates.
They have a body clock which is tied to the tides, even when they are removed from the ocean.
The real test would be to see if this clock remains locked to the tides after they have been removed from the sea.
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2 Comments:
First, the Bay of Fundy is in Canada, not in the USA.
Second, I've heard of a laser apparatus used to measure the lunar tide in a cup of water.
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The effects of the tides can be seen in bodies smaller than 1cm across: marine invertebrates.
They have a body clock which is tied to the tides, even when they are removed from the ocean.
The real test would be to see if this clock remains locked to the tides after they have been removed from the sea.
I´m afraid you are mixing two aspects, two sides of the "coin" tides ...
Let us consider only Moon related "global" tides, as if with no continents.
In an instant, Moon pull on small bodies is constant across them, and NO proper tidal effects occur. BUT that pull DOES change with time: when at sublunar area, it is bigger than when further away, and the angle between that pull vector and the body weight also changes. Objects kind of lighten when under the Moon, no matter where they are, at sea or removed from it ...
Those really tiny weight changes occur with same period (maximum weight some six hours before and after the minimum), just because their causes are the same. Therefore they are also a little stronger when Sun effects add to Moon´s, that is, app. a couple of days after full and new Moon´s.
And most living beings, we included, somehow are affected by those changes, though it is not always perceptible.
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Therefore they are also a little stronger when Sun effects add to Moon´s, that is, app. a couple of days after full and new Moon´s.
Sorry ... There I was the "mixer" of things!. That couple of day delay, being due to details connected to "spacial" circumstances, only counts for ocean tides.
Every day minimum weight of objects is exactly when Moon is over the object position meridian (and when over the antipodes), and monthly bigger daily changes are exactly when full and new Moons.
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The amplitude of the tides does not depend on the size of the reservoir.
The amplitude of the tides depends on the speed of water rotation, in the lakes of the seas and oceans..
The list of seas with an average swirl speed of more than 0.5 km / h, and an average tidal wave height of more than 5 cm:
Irish Sea, North Sea, Barents Sea, Baffin Sea, White Sea, Bering Sea, Sea of Okhotsk, Arabian Sea, Sargasso Sea, Hudson Bay, Maine Bay, Gulf of Alaska. etc..
The list of seas with an average swirl speed of less than 0.5 km / h, and an average tidal wave height of less than 5 cm:
The Baltic Sea, the Greenland Sea, the Black Sea, the Sea of Azov, the Caspian Sea, the Chukchi Sea, the Kara Sea, the Laptev Sea, the Red Sea, the Marmara Sea, the Caribbean Sea, the Sea of Japan, the Gulf of Mexico, etc.
Note: The height of the tidal wave (soliton) and the amplitude of the tides is not the same..
Tides is the result of the rotation of the Earth and whirlpools
https://www.thenakedscientists.com/forum/index.php?topic=73127.0
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The amplitude of the tides does not depend on the size of the reservoir.
LOL
Do you look forward to watching the 20 foot changes in liquid level in a glass of orange juice.