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Variation in tides
According to a local old sea dog, there is a 50 year cycle to the height of
tides superimposed on the usual new/full moon / sun distance, cyclic variation. If there is indeed such an influence , would any one know what it is - earth's precession ? |
#2
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Variation in tides
It's not the earth's precession, that has a cycle of about 26000 years. (I
think) Regards Colin Dawson www.cjdawson.com "n cook" wrote in message ... According to a local old sea dog, there is a 50 year cycle to the height of tides superimposed on the usual new/full moon / sun distance, cyclic variation. If there is indeed such an influence , would any one know what it is - earth's precession ? |
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Variation in tides
Hello
This has prompted a question I have not worked out the answer but is probably a very easy one and everybody else probably knows the answer. If the moon goes round the earth once about 25 hours and is the main effect on the tides why do we get 2 high tides in 25 hours and not one regards Paul "n cook" wrote in message ... According to a local old sea dog, there is a 50 year cycle to the height of tides superimposed on the usual new/full moon / sun distance, cyclic variation. If there is indeed such an influence , would any one know what it is - earth's precession ? |
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Variation in tides
p forsdick wrote in message
. uk... Hello This has prompted a question I have not worked out the answer but is probably a very easy one and everybody else probably knows the answer. If the moon goes round the earth once about 25 hours and is the main effect on the tides why do we get 2 high tides in 25 hours and not one regards Paul "n cook" wrote in message ... According to a local old sea dog, there is a 50 year cycle to the height of tides superimposed on the usual new/full moon / sun distance, cyclic variation. If there is indeed such an influence , would any one know what it is - earth's precession ? Tidal effects not travelling at 1000 mph (1000 times 24 = earth circumference) is probably something to do with that effect |
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Variation in tides
"p forsdick" wrote in message . uk... Hello This has prompted a question I have not worked out the answer but is probably a very easy one and everybody else probably knows the answer. If the moon goes round the earth once about 25 hours and is the main effect on the tides why do we get 2 high tides in 25 hours and not one regards Paul It is wrong to think of the tides as being caused by the Moon 'pulling'. The key is that the whole 'Earth-Moon' system, is orbiting around their common mass centre (actually inside the Earth). In it's simplest form, the bit of the Earth closest to the Moon, gets pulled more, and bulges upwards towards the Moon, but at the same time, the part furthest away, gets pulled less, and with the centripetal effect, bulges up in the opposite direction. Worse, the actual 'tides', lag the pull, and can get accelerated/decelerated by the local geography, so (for example), there are places that actually get four tides (or more!) a day, as the water takes different routes round the local land masses. Best Wishes |
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Variation in tides
"n cook" wrote in message
... According to a local old sea dog, there is a 50 year cycle to the height of tides superimposed on the usual new/full moon / sun distance, cyclic variation. If there is indeed such an influence , would any one know what it is - earth's precession ? A good reference:: http://home.hiwaay.net/~krcool/Astro/moon/moontides/ |
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Variation in tides
"Roger Hamlett" wrote in message
... "p forsdick" wrote in message . uk... Hello This has prompted a question I have not worked out the answer but is probably a very easy one and everybody else probably knows the answer. If the moon goes round the earth once about 25 hours and is the main effect on the tides why do we get 2 high tides in 25 hours and not one regards Paul It is wrong to think of the tides as being caused by the Moon 'pulling'. The key is that the whole 'Earth-Moon' system, is orbiting around their common mass centre (actually inside the Earth). In it's simplest form, the bit of the Earth closest to the Moon, gets pulled more, and bulges upwards towards the Moon, but at the same time, the part furthest away, gets pulled less, and with the centripetal effect, bulges up in the opposite direction. Worse, the actual 'tides', lag the pull, and can get accelerated/decelerated by the local geography, so (for example), there are places that actually get four tides (or more!) a day, as the water takes different routes round the local land masses. Best Wishes Damn it! The first message i actually had an accurate answer to and someone beat me to it ): |
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Variation in tides
"Robert Geake" wrote in message ... "Roger Hamlett" wrote in message ... "p forsdick" wrote in message . uk... Hello This has prompted a question I have not worked out the answer but is probably a very easy one and everybody else probably knows the answer. If the moon goes round the earth once about 25 hours and is the main effect on the tides why do we get 2 high tides in 25 hours and not one regards Paul It is wrong to think of the tides as being caused by the Moon 'pulling'. The key is that the whole 'Earth-Moon' system, is orbiting around their common mass centre (actually inside the Earth). In it's simplest form, the bit of the Earth closest to the Moon, gets pulled more, and bulges upwards towards the Moon, but at the same time, the part furthest away, gets pulled less, and with the centripetal effect, bulges up in the opposite direction. Worse, the actual 'tides', lag the pull, and can get accelerated/decelerated by the local geography, so (for example), there are places that actually get four tides (or more!) a day, as the water takes different routes round the local land masses. Best Wishes Damn it! The first message i actually had an accurate answer to and someone beat me to it ): Your reference, was much more complete though. :-) Best Wishes |
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Variation in tides
JRS: In article , dated Thu, 6 Jul 2006
06:44:04 remote, seen in news:uk.sci.astronomy, n cook posted : According to a local old sea dog, there is a 50 year cycle to the height of tides superimposed on the usual new/full moon / sun distance, cyclic variation. If there is indeed such an influence , would any one know what it is - earth's precession ? Never heard of it; and if it existed I'd have expected to have done so. It seems unlikely that it's the 260th harmonic of the Earth's precession, or the third sub-harmonic of the Metonic cycle, or the Jubilee cycle. Paul Forsdick : see Tides then Sea-Tides, indexed at the top of URL:http://www.merlyn.demon.co.uk/gravity0.htm. -- © John Stockton, Surrey, UK. Turnpike v4.00 MIME. © Web URL:http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms & links; Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc. No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News. |
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Variation in tides
p forsdick wrote:
If the moon goes round the earth once about 25 hours and is the main effect on the tides why do we get 2 high tides in 25 hours and not one http://astunit.com/tutorials/tides.htm Best, Stephen Remove footfrommouth to reply -- + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Stephen Tonkin | ATM Resources; Astro-Tutorials; Astro Books + + (N51.162 E0.995) | http://astunit.com + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + |
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