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Natural Science Forum / Earth Science / Oceanography / September 2005Tides
Tides, Seiches, River Bores, Storm Surges and Tidal Waves. Johannes Keppler and Gallileo Gallilei once argued over whether the moon was the main cause of the tides. Whilst massive assumptions that dont stand up to any scrutiny are applied in the description of how the moon is involved with the tides, no lien is given to the existence of any input from the moon in the other phenomenae. The accepted theory of lunar influence on tides is that the moon raises small particles which tend to follow it. Meanwhile over on the other side of the planet these particles, flowing away from the altazimuth, cause high tides on that side of the earth at the same time. Discrepancies in the observed times of high tide are explained as friction. Some obvious problems with this theory: 1. On the opposite side of the earth when these tides are supposed to occur by default as it were, the tides are often a little higher than those upon which the moon is alledged to have a direct bearing. 2. The direct gravity idea should show that the highest tides tend to occur over the tropics, certainly at no time should they fail to form highest peaks and troughs at greater latitudes than 28 north or south. In these lower latitues both the sun and the moon are overhead. 3. In winter, the times of sunrise vary by many hours when compared to the times of sunrise in summer. The time of moonrise varies even more wildly EVERY MONTH not every year. 4. Water, even sea water, is considered a nearly perfect fluid. 5. According to the Cavendish experiment, the moon should (if the above silliness hold true) attract heavier particles with more alacrity than it does air and seawater. And of course it should show peaks in the atmosphere far greater than is the present case. (The tropopause is higher in lower latitudes due to the temperature. At least the differences involved are more easily equated to that. For with the above silliness, the upper atmosphere should be 1/80th of the distance to the moon.) The renaissance is generally counted as to have started some time around the era in which Johannes Keppler and Gallileo Gallilei lived. The times before then are sometimes spoken of as the dark ages, when natural phenomenae were ascribed to supernatural causes. We can now explain most of them in terms of schoolboy phyics. We believe we now live in an age of reason and light. It would seem we are still stumbling blindly in the dark over more than a few things. >Tides, Seiches, River Bores, Storm Surges and Tidal Waves. > [quoted text clipped - 11 lines] >Discrepancies in the observed times of high tide are explained as >friction. I don't know where you got this from, but it's quite incorrect. The main element for the age of the tide (difference between time of overhead or directly opposite moon and high tide) is the limit in ocean wave speed relative to the motion of the moon. Ocean waves propagate at ca. 200 m/s while the apparent motion of the moon is ca 450 m/s (at the equator). For a reasonable discussion of the tidal force and ocean response, see, for example, Gill, A. E., Atmosphere-Ocean Dynamics, Academic Press, 1982. [snip] >It would seem we are still stumbling blindly in the dark over more than >a few things. But if you look to sources of illumination, you'll do better.  SignatureRobert Grumbine http://www.radix.net/~bobg/ Science faqs and amateur activities notes and links. Sagredo (Galileo Galilei) "You present these recondite matters with too much evidence and ease; this great facility makes them less appreciated than they would be had they been presented in a more abstruse manner." Two New Sciences > >Tides, Seiches, River Bores, Storm Surges and Tidal Waves. > > [quoted text clipped - 29 lines] > > But if you look to sources of illumination, you'll do better. A simpler explanation can be found in a bottle of pancake syrup. Tip it over: observe why it there is a delay in reaching the maximum or minimum tide levels. > >Discrepancies in the observed times of high tide are explained as > >friction. > I don't know where you got this from, but it's quite incorrect. > The main element for the age of the tide (difference between time > of overhead or directly opposite moon and high tide) is the limit > in ocean wave speed relative to the motion of the moon. Ocean waves > propagate at ca. 200 m/s while the apparent motion of the moon > is ca 450 m/s (at the equator). It is based on an essay in the Encyclopeadia Britannica 1986 edition discussing the work of George Darwin. The actual method for forcasting tides can not be done using theory. What is done is that a series of reading is taken over an year and the immediate future obtained by interpolation. Most of the cheaper programmes use a plot taken from the last month. For a similar explanation you may want to check out Reeds or the Silk Cut nautical almanacks. Along with the mumbo jumbo accepted at present their is a lot of really useful information for those that have to actually do something with the academical sh.t. There are about 46 "Primary Ports" along the coasts around the British Isles for which the tidal tables have been worked out and which are regularly updated. The secondary ports appear in major shipping catalogues (called almanacs) as river mouths at smaller towns, for which a process of interpolation or exrapolation (I can never remember which is which) is supplied as ready reckoners. Other places along coasts can be guesstimated from those. There are regions (such as the Fenns and the Menai Straights) for which a consumate treatise is elusive. Such places, if they are important industrially (as for example the river Dee, which has a rapidly changing sand bar system that despite constant effort from dredgers and the like really do need local knowledge) require piloting facilities. The primary ports are: Falmouth Devonport, & Dartmouth. Portland, Poole, Southhampton & Portsmouth. Shoreham & Dover. Shhernes, London Bridge, Walton on Naze & Lowestoft. Immingham & Tyne. Leith & Aberdeen. Lerwick. Ullapool & Oban. Greenock. Liverpool & Holyhead. Milford Haven & Avonmouth. Dublin & Cobh. Belfast & Galway. Esbjerg. Heligoland, Cuxhaven & Wilhelshaven. The Hook of Holland & Vissingen. Dieppe, Le Havre & and Cherbourg. San Malo. Saint Peter Port & Saint Helier. Brest. Nil Pointe de Grave Lisboa Gibraltar. > There are about 46 "Primary Ports" along the coasts around the British > Isles for which the tidal tables have been worked out and which are > regularly updated. See more on this at: http://www.bbc.co.uk/weather/coast/tides/southwest.shtml Another page on the BBC web site has this to on the construction of tide tables: The tides are generated by gravitational influences of the Earth-Moon-Sun system, whose astronomical relationship and orbital details are known extremely accurately. Using this information, together with the tidal constants derived from the tidal analyses, the tides can be predicted for any date as far ahead into the future as required. However, for predictions well into the future (many decades) the effects of global sea level rises and changes in seabed topography have to be carefully considered. These may have a significant effect upon local tidal behaviour, and the predictions can only be computed using the tidal data currently available on the UKHO database. So the further ahead we go from the date the tidal data is held on the database, the less reliable the predictions will become. You only have to note the changes in the table of lunar phases over a period of less than an year to realise there is a degree of not quiteness about the above. http://aa.usno.navy.mil/data/docs/MoonPhase.html#y2005 Only minor changes but they are there. As it happens the BBC is a noted pander to accepted academic explanation. But that is just my personal opinion. Don't let my disgust with them throw you off. See for yourself if you agree with them: http://www.bbc.co.uk/weather/features/coast_sea/tidesfaq.shtml Here is a list of lunar phases for 2005. If I can find this thread in an year's time (I will have forgotten all about it long efore then I imagine) I shall post the same table for comparison. NEW MOON FIRST QUARTER FULL MOON LAST QUARTER d h m d h m d h m d h m JAN. 3 17 46 JAN. 10 12 03 JAN. 17 6 57 JAN. 25 10 32 FEB. 2 7 27 FEB. 8 22 28 FEB. 16 0 16 FEB. 24 4 54 MAR. 3 17 36 MAR. 10 9 10 MAR. 17 19 19 MAR. 25 20 58 APR. 2 0 50 APR. 8 20 32 APR. 16 14 37 APR. 24 10 06 MAY 1 6 24 MAY 8 8 45 MAY 16 8 56 MAY 23 20 18 MAY 30 11 47 JUNE 6 21 55 JUNE 15 1 22 JUNE 22 4 14 JUNE 28 18 23 JULY 6 12 02 JULY 14 15 20 JULY 21 11 00 JULY 28 3 19 AUG. 5 3 05 AUG. 13 2 38 AUG. 19 17 53 AUG. 26 15 18 SEPT. 3 18 45 SEPT. 11 11 37 SEPT. 18 2 01 SEPT. 25 6 41 OCT. 3 10 28 OCT. 10 19 01 OCT. 17 12 14 OCT. 25 1 17 NOV. 2 1 24 NOV. 9 1 57 NOV. 16 0 57 NOV. 23 22 11 DEC. 1 15 01 DEC. 8 9 36 DEC. 15 16 15 DEC. 23 19 36 DEC. 31 3 12 Lunar Tides I have a copy of the Encyclopaedia Britannica but it will not work with XP or for some yet to be resolved problem. So some commuting -as and when possible, to my local library is required. It is 3:15 (and counting) on Monday morning so that is out of the question for a few hours. This is the standard newbie level of understanding of tides aka Encarta: The Moon, being much nearer to the Earth than the Sun, is the principal cause of tides. When the Moon is directly over a given point on the surface of the Earth, it exerts a powerful pull on the water, which therefore rises above its normal level. Water covering the part of the Earth farthest from the Moon is also subject to this pull, so that another distinct dome of water is formed on the farther side of the Earth providing the basis for a second wave. The lunar wave crest directly beneath the Moon is called direct tide, and the crest on the side of the Earth diametrically opposite is called opposite tide. At both crests, the condition known as high water prevails, while along the circumference of the Earth perpendicular to the direct-opposite tidal axis, phases of low water occur. Low and high waters alternate in a continuous cycle. The variations that naturally occur in the level between successive high water and low water are referred to as the range of the tide. At most shores throughout the world, two high waters and two low waters occur every lunar day, the average length of a lunar day being 24 hr, 50 min, and 28 sec. One of these high waters is caused by the direct-tide crest and the other by the opposite-tide crest. Two successive high waters or low waters are generally of about the same height. At various places outside the Atlantic Ocean, however, these heights vary considerably; this phenomenon, which is known as diurnal inequality, is not completely understood. http://uk.encarta.msn.com/encyclopedia_761561041/Tide.html#endads Newton's Three Laws of Motion Newton's first law of motion states that if all the forces acting on an object is zero, then the object will remain at rest or remain moving at constant velocity. The Second Law Newton's second law relates net force to acceleration. A net force on an object will accelerate it that is, change its velocity. The acceleration will be proportional to the magnitude of the force and in the same direction as the force. The proportional constant is the mass, m = F/a A more massive object will require a greater force for a given acceleration than a less massive one. The Third Law Newton's third law of motion states that when an object exerts a force on another object, it experiences a force in return. The force that object 1 exerts on object 2 must be of the same magnitude as the force that object 2 exerts on object 1 but in the opposite direction. http://uk.encarta.msn.com/encyclopedia_761556906/Mechanics.html Or to put that last bit in perspective: Newton's third law of motion states that when an object exerts a force on another object, it experiences a force in return. The force that the moon exerts on a drop of water must be of the same magnitude as the force that a drop of water exerts on the moon but in the opposite direction. > Newton's third law of motion states that when an object exerts a force > on another object, it experiences a force in return. > > The force that the moon exerts on a drop of water must be of the same > magnitude as the force that a drop of water exerts on the moon but in > the opposite direction. Correct. A drop of water is small and light, so that force can move (well, accelerate) it a lot. The Moon is large and heavy, so the same force doesn't have much effect. Signature"You're not like other people, you do what you want to." -Fleetwood Mac, "Thrown Down" --------------------------------------------------------------- Simon Waldman, UK email: swaldman@firecloud.org.uk --------------------------------------------------------------- >Lunar Tides > [quoted text clipped - 10 lines] >surface of the Earth, it exerts a powerful pull on the water, which >therefore rises above its normal level. Actually, the gravitational field of the sun is far larger at the earth than is the moon's. The tides are not due to the *strength* of the gravitational field, but rather the gradient of the field. >Water covering the part of the >Earth farthest from the Moon is also subject to this pull, Eh? >so that >another distinct dome of water is formed on the farther side of the [quoted text clipped - 18 lines] > >http://uk.encarta.msn.com/encyclopedia_761561041/Tide.html#endads Issac Newton originally explained the tides, but it appears the writers and ediors of Encarta didn't bothe to check on good old Ike; i.e., Encarta got it wrong, wrong, wrong. See http://csep10.phys.utk.edu/astr161/lect/time/tides.html for a correct, if simplified, explanation. I've seen the Britannica explanation and it is correct. ************* DAVE HATUNEN (hatunen@cox.net) ************* * Tucson Arizona, out where the cacti grow * * My typos & mispellings are intentional copyright traps * > Issac Newton originally explained the tides, but it appears the > writers and ediors of Encarta didn't bother to check on good old > Ike; i.e., Encarta got it wrong, wrong, wrong. Actually Newton failed to explain it and no-one since has come up with the answer either. Lord Kelvin came up with the tidal calculator but it is not an explanation of tides. > See http://csep10.phys.utk.edu/astr161/lect/time/tides.html for a > correct, if simplified, explanation. Why the link -which also fails masterfully btw, has to work with San Fransisco and Galveston (some 35 degrees apart) when the more acceptable division is New Orleans, Fiji, Calcutta and Portsmouth (all some 90 degrees apart) is beyond me New Orleans has diurnal tides I believe. The links both describe a semidiurnal. No idea how the bulge on the far side is caused. That was the main point of the original post by the way. It doen't fit the basic physics on which the universe runs. Fiji's tides are timed to the sun. Portsmouth has a double high and low water. How is that due to the moon? How is the fact that the tides one end of the channel it is in the middle of, can have high tide when the other end has low tide if the link is correct? > I've seen the Britannica explanation and it is correct. I finally got my disk working but I can't take to the interface at all. Sooooo It's back to the library. > Portsmouth has a double high and low water. How is that due to the > moon? I can't answer most of the rest of this post. But the reason that the Solent (the area between the Isle of Wight and the mainland) gets double tides is simply that the "surge" of water that is making its way along the English Channel enters the Solent from one end and then, a couple of hours later, also enters the Solent from the other end. Or at least, that's how I've always understood it. It makes intuitive sense to me. Followups set to sci.geo.oceanography, as this has sod all to do with earthquakes. Signature"I believe we are on an irreversible trend toward more freedom and democracy - but that could change." - Dan Quayle --------------------------------------------------------------- Simon Waldman, UK email: swaldman@firecloud.org.uk --------------------------------------------------------------- The tide are measured at a location and the data is analised using FFT to produce the tidal harmonics. This separates the different inflences on the tides such as S2 being the larger tidal input of the sun and M2 being the same for the moon. It should be noted that although M2 is the most important tidal input for most of the world. there are some places where the solar input is actually greater. I have always understood these differences to be due to Amphidromic systems where the "wave" of the tide, when nearing a coast would rotate around a point so that tidal times are defined by that arrangement more than the simle moon -sun orientation. Feel free to correct me if I am wrong. I have none of my papers with me and mearly remembering college 7 years ago. Stephen Redford > > Portsmouth has a double high and low water. How is that due to the > > moon? > I can't answer most of the rest of this post. But the reason that the > Solent (the area between the Isle of Wight and the mainland) gets double > tides is simply that the "surge" of water that is making its way along > the English Channel enters the Solent from one end and then, a couple of > hours later, also enters the Solent from the other end. You can't answer this one too neither, since it requires you to denounce the "fact" that a pull causes a surge that ddrags water thither and yon. > Or at least, that's how I've always understood it. It makes intuitive > sense to me. Intuitive sense. Isn't that the reason most gullible or ignorant people presume they understand most things? Not least among those, the tides. > Followups set to sci.geo.oceanography, as this has sod all to do with > earthquakes. Actually this has quite a lot to do with earthquakes not least of the reasons being the ignorance among the regulars there about tides. "SteveR" <s.redford@gmail.com> wrote in message news:1107956169.429456.238110@l41g2000cwc.googlegroups.com > The tide are measured at a location and the data is analysed using FFT > to produce the tidal harmonics. This separates the different influences > on the tides such as S2 being the larger tidal input of the sun and M2 > being x for the moon. It should be noted that although M2 is the > most important tidal input for most of the world, there are some places > where the solar input is actually greater. Could you explain the terms FFT and Amphidromic for the sake of those whose half open minds are already jading shallowly? > I have always understood > these differences to be due to Amphidromic systems where the "wave" of > the tide, when nearing a coast would rotate around a point so that > tidal times are defined by that arrangement more than the simple moon > -sun orientation. I posted a pic of co-tidal lines here: http://groups.msn.com/Weatherlore/general.msnw?action=get_message&mview=0&ID_Mes sage=268 Most library hubs in the UK will have a decent enough reference centre to get a look at books on the subject. Wouldn't you know it but my biro ran out when I was writing the source for the photocopy. Introduction to Physical and Biologic(al?) Ocean.........?? By ....? King. > Feel free to correct me if I am wrong. I have none of my papers with me > and merely remembering college 7 years ago. I'm zenning most of this too. Intuitively? I haven't the access to the books I once had. Mind you it's been interesting relearning it all again. Sorry to have to post your reply with the dimmo's but if you wanted to have this discussion with me it had to be with the input going to both groups. If you and dickhead up there^ don't like it, then start your own thread. >>Michael Mcneil wrote: >>>Portsmouth has a double high and low water. How is that due to the >>>moon? [quoted text clipped - 7 lines] > You can't answer this one too neither, since it requires you to denounce > the "fact" that a pull causes a surge that ddrags water thither and yon. I'm sorry, but I don't understand your sentence. If you can rephrase it comprehensibly I'll endeavour to respond. >>Or at least, that's how I've always understood it. It makes intuitive >>sense to me. > > Intuitive sense. Isn't that the reason most gullible or ignorant people > presume they understand most things? Not least among those, the tides. Possibly. That doesn't mean it has to be wrong. >>Followups set to sci.geo.oceanography, as this has sod all to do with >>earthquakes. > > Actually this has quite a lot to do with earthquakes not least of the > reasons being the ignorance among the regulars there about tides. The regulars of sci.geo.earthquakes being ignorant about tides does not make a discussion of tides relevant to sci.geo.earthquakes. I am quite ignorant of cookery, but that doesn't mean that people should crosspost about cookery into unrelated groups that I frequent. I'm sure that if people from sci.geo.earthquakes want to learn about tides and other topics related to oceanography, they are quite capable of subscribing themselves to sci.geo.oceanography. <snip of what seems to be a reply to somebody else's post, appended to the end of this post for no immediately obvious reason> -Simon. Signature"Crime does not pay... as well as politics." -- Alfred E. Newman --------------------------------------------------------------- Simon Waldman, UK email: swaldman@firecloud.org.uk --------------------------------------------------------------- >The regulars of sci.geo.earthquakes being ignorant about tides does not >make a discussion of tides relevant to sci.geo.earthquakes. I am quite [quoted text clipped - 4 lines] >tides and other topics related to oceanography, they are quite capable >of subscribing themselves to sci.geo.oceanography. The tides are relevant to sci.geo.earthquakes if you wish to address the common claim that earthquakes can be caused by the alignment of earth, moon and sun, so you might suspend your snottiness accordingly and find other windmills to tilt at. ************* DAVE HATUNEN (hatunen@cox.net) ************* * Tucson Arizona, out where the cacti grow * * My typos & mispellings are intentional copyright traps * > The tides are relevant to sci.geo.earthquakes if you wish to > address the common claim that earthquakes can be caused by the > alignment of earth, moon and sun, so you might suspend your > snottiness accordingly and find other windmills to tilt at. My reasoning too. The twit is probably just miffed that no-one ever posts to sci.geo.oceanography. Besides the chat on sci.geo.earthquakes recently was full of stuff about tidal waves. Concerning which I have yet to see a scientific explanation about why the shock did not induce more chaotic splashing instead of the cohesive system that was invoked. What sort of discussions were they? Nothing but bickering over words. And were there a higher class of discussion about tidal waves in any of the myriad threads on sci.geo.oceanography? Speaking of which, just what sort of posts has the twit posted there? I don't remember coming across anything of any calibre. >>The tides are relevant to sci.geo.earthquakes if you wish to >>address the common claim that earthquakes can be caused by the >>alignment of earth, moon and sun, so you might suspend your >>snottiness accordingly and find other windmills to tilt at. > > My reasoning too. I stand corrected. My apologies to anybody who I offended. I felt that I would be doing a good turn by setting followups, as I didn't see that what I was writing (about my understanding of tides in the Solent) had any relevance to earthquakes, and did so. I happened to be feeling rather irritable at the time that I received the reply to this, and since the reason given for the relevance of the crossposting was a nonsensical one (something that I still believe), I was overly sarcastic. This was, indeed, uncalled for. > The twit is probably just miffed that no-one ever > posts to sci.geo.oceanography. Assuming that "the twit" refers to me: Not at all. I am generally a lurker on s.g.o, and even though it is a low-traffic group I learn a great deal from the few posts that do appear. > Speaking of which, just what sort of posts has the twit posted there? > > I don't remember coming across anything of any calibre. Indeed not. I mostly lurk there as I'm no great expert on the matters discussed. Signature--------------------------------------------------------------- Simon Waldman, UK email: swaldman@firecloud.org.uk --------------------------------------------------------------- > I stand corrected. My apologies to anybody who I offended. You are replying to one of sci.geo.earthquakes resident k00ks. KF McNeil. Lossless compression. And don't worry about offending him. > My apologies to anybody who I offended. No need to appologise there are a lot worse things going on in sge. Being one of the main culprits I tend to behave rather worse than most. No excuses though and no appologies too, neither. I have come across a nice essay on the subject of tides in the book I stole the reproduction of co-tidal lines from: Introduction to Physical and Biological Oceanography. I'll post more later. Most of it is repeated in a slightly more concise form in Brown's Nautical Almanac (I doubt it is still in production these days with satellite navigation and global communication as well as computed data so readily available.) The gist is still the same though. (It's just the sightings tables have gone with the sextant, making the need for a new text book each year unecessary.) I am sorry I am so churlish. I keep meaning to change but I can't be bothered. Introduction to Physical & Biological Oceanography ISBN: 0844804002 Author: Cuchlaine King >> Issac Newton originally explained the tides, but it appears the >> writers and ediors of Encarta didn't bother to check on good old [quoted text clipped - 3 lines] >the answer either. Lord Kelvin came up with the tidal calculator but it >is not an explanation of tides. Oh, dear. Most of us who studied physics have always assumed Ike got it right. Not least because we're able to perform the same rather trivial calculations he used. What part do you claim he got wrong and/or what is the correct explanation? ************* DAVE HATUNEN (hatunen@cox.net) ************* * Tucson Arizona, out where the cacti grow * * My typos & mispellings are intentional copyright traps * > Oh, dear. Most of us who studied physics have always assumed Ike > got it right. Not least because we're able to perform the same > rather trivial calculations he used. What part do you claim he > got wrong and/or what is the correct explanation? Ike? I was talking about Isaac Newton. If you remember reading his book, he did admit that the calculations he was using could not explain the behaviour of tides except for the Aethiope Sea. ISTR he only said a part of that too. I do have a link to Pricipia online but AOL is playing silly buggers with my links at the moment. Nothing stopping you from looking for one though. I can't quote you chapter and verse but a re-read is always worthwhile with such a masterpiece of logic. Have fun. >> Oh, dear. Most of us who studied physics have always assumed Ike >> got it right. Not least because we're able to perform the same [quoted text clipped - 13 lines] >though. I can't quote you chapter and verse but a re-read is always >worthwhile with such a masterpiece of logic. You may have noticed that the Encarta article I was responding to addresssed the general theory of the tides, not the specific locational variances. And Newton was quite correct in his general theory of the tides and Encarta is wrong. ************* DAVE HATUNEN (hatunen@cox.net) ************* * Tucson Arizona, out where the cacti grow * * My typos & mispellings are intentional copyright traps * > You may have noticed that the Encarta article I was responding to > addresssed the general theory of the tides, not the specific > locational variances. And Newton was quite correct in his general > theory of the tides and Encarta is wrong. Here is the link I have: http://members.tripod.com/~gravitee/toc.htm Search for yourself and see what he had to say about tides. Make sure you have your pop-up controls switched on as it is a really drech site, full of banners and pop up crapware. >> You may have noticed that the Encarta article I was responding to >> addresssed the general theory of the tides, not the specific [quoted text clipped - 4 lines] >http://members.tripod.com/~gravitee/toc.htm >Search for yourself and see what he had to say about tides. Unfortunately, it does not appear anything in that link addresses the tides, the tides appearing in Book II. ************* DAVE HATUNEN (hatunen@cox.net) ************* * Tucson Arizona, out where the cacti grow * * My typos & mispellings are intentional copyright traps * "Up antenna!" Mike! I don't mean to flame you. But, in the below discussion you mention that New Orleans might be a good place from which to compare tide generation. FYI: The tides in New Orleans are so controlled by the Mississippi River that NOAA (the Natioanl Oceanic and Atmospheric Administration, an agency within the U.S.Department of Commerce) does not have a tide gage at New Orleans. Nor do they publish predictions or actual water levels for N.O. The closest tide gage is many miles south of New Orleans at Southwest Pass in the Mississippi delta. New Orleans is on the Mississippi River not on the Gulf of Mexico. For a rather good explanation of tidal forces, go to: http://www.co-ops.nos.noaa.gov/restles1.html I suspect that CO-OPS knows more about tides than either Britannica or Encarta. B² "Down antenna" >> Issac Newton originally explained the tides, but it appears the >> writers and ediors of Encarta didn't bother to check on good old [quoted text clipped - 33 lines] > Sooooo > It's back to the library. > "Up antenna!" > Mike! I don't mean to flame you. But, in the below discussion you mention > that New Orleans might be a good place from which to compare tide > generation. I was being clever. I knew that New Orleans didn't fit either simple descriptions. I didn't know it was an even better example. Thanks for the input. > FYI: The tides in New Orleans are so controlled by the Mississippi River > that NOAA (the Natioanl Oceanic and Atmospheric Administration, an agency > within the U.S.Department of Commerce) does not have a tide gage at New > Orleans. Nor do they publish predictions or actual water levels for N.O. > The closest tide gage is many miles south of New Orleans at Southwest Pass > in the Mississippi delta. When in the future this all crops up again and I attempt to disabuse the next generation of indoctrinated monkeys I will bear all this in mind. No one here want to mention Fiji? > New Orleans is on the Mississippi River not on the Gulf of Mexico. I always thought the Mississippi rolled out into the Gulf. I am rather lackadaisical in my research (relying on my ablity to know it all.) > For a rather good explanation of tidal forces, go to: > http://www.co-ops.nos.noaa.gov/restles1.html > I suspect that CO-OPS knows more about tides than either Britannica or > Encarta. Got it bookmarked. But I suspect the reason is that tides in the region are so small that compared to river spates due to rainfall etc., having a prediction is pointless It's horses for courses with encyclopaedae. The Encarta is geared for schoolchildren and the home environment and as such aught to be more dilligent in its presentation of facts as it is indoctrinating young minds. The Enc. Brit. should be on the ball too, as it is written by the expert's experts. The plain fact is even I make mistakes. (And sometimes I admit to them.) >> New Orleans is on the Mississippi River not on the Gulf of Mexico. > >I always thought the Mississippi rolled out into the Gulf. I am rather >lackadaisical in my research (relying on my ablity to know it all.) By that reasoning Minneapolis is on the Gulf of Mexico. ************* DAVE HATUNEN (hatunen@cox.net) ************* * Tucson Arizona, out where the cacti grow * * My typos & mispellings are intentional copyright traps * > >> New Orleans is on the Mississippi River not on the Gulf of Mexico. > >I always thought the Mississippi rolled out into the Gulf. I am rather > >lackadaisical in my research (relying on my ablity to know it all.) Or rather by my schoolboy's atlas, the connurbation stretches over to the Mississippi Sound. The globe I usually reach for first is not detailed enough for me to distinguish how far up the delta New Orleans really is. Well I learned something. Who knows if I will ever find it more useful than to belabour holders of deeply entrenched ideas with. Or at least attempt to muddy the waters enough to get some grey matter stirred. NBL; I know. Just for the record, none of this quotes me. >> >> New Orleans is on the Mississippi River not on the Gulf of Mexico. > [quoted text clipped - 14 lines] > >NBL; I know. ************* DAVE HATUNEN (hatunen@cox.net) ************* * Tucson Arizona, out where the cacti grow * * My typos & mispellings are intentional copyright traps * Who said that? >Who said that? Who said what? ************* DAVE HATUNEN (hatunen@cox.net) ************* * Tucson Arizona, out where the cacti grow * * My typos & mispellings are intentional copyright traps * NOW have I rather passed over than thoroughly surveied all Britaine, namely those two most flourishing Kingdomes England and Scotland. And whereas I am now to crosse the seas for Ireland and the rest of the Isles, if I praemise some few lines touching the British sea, I hope it shall not seeme a crooked course or an extravagant digression. 2. Britaine is incompassed round about with the vast and open maine Ocean, which ebbeth and floweth so violently with maine tides that, as Pytheas of Marsiles hath reported, it swelleth 80 cubits about Britaine, and Saint Basile hath tearmed it mare magnum &c., that is, The great Sea and dreadfull to Sailers, Yea and Saint Ambrose wrote thus of it: The great Sea not adventured on by sailers, nor attempted by mariners, is that which with a roaring and surging current environeth Britaine, and reacheth into farre remote parts and so hidden out of sight as that the very fables have not yet come thither. Certes, this sea sometimes overfloweth the fields adjoining, otherwhiles again it retireth and leaveth all bare, and, that I may use the words of Plinie, by reason of this open largenesse it feeleth more effectually the force and influence of the Moone, exercising her powre thereupon without impeachment. And it floweth alwaies up within the land with such violence that it doth not onely drive backe the streames of rivers, but also either overtaketh and surpriseth beasts of the land, or else leaveth behind it those of the sea. For there have bin seene in every age, to the great astonishment of the beholders, so many and so huge Sea-monsters left on drie land upon our shore that Horace sang this note not without good cause: > Who said that? Noe aediea butteth yt ame onne ye ynternette soe ytte myst be anne tuethe. {Alle ofn eate} William Camden, Britannia (1607)? > NOW have I rather passed over than thoroughly surveied all Britaine, > namely those two most flourishing Kingdomes England and Scotland. And [quoted text clipped - 37 lines] > > {Alle ofn eate} > William Camden, > Britannia (1607)? Beg pardon for the late reply. I have been having too much fun trolling and flaming and otherwhiles etceterra, president Bush and his handlers. <Slap> Naughty Mike </slap> I have lost the link. I may have it on my desktop or lost somewherre yne ye bowles of my computer. Blowed if I can understand what makes msn's desktop search work. (I aught to stick with the file search engine in the start menu.) Sorry. The point I was was making was the ancient reliance on the presumption about the lunar theory of raisng tides predates most renaissance thinking. Consider (if you have the mathematical ability) how the genii (such as Poncelet) at the turn of the 19th century might have applied calculus and the duality of linear motion to the behaviour of gravitational attractive forces on the chords the sun and moon produce, had there not been a war on. There is certainly no restriction on paper to the link between tides and the recipocrity of quakes. From what little I understand of the subject at least. There may be restrictions of course. Giant ones no doubt; that I in my ignorance can't even begin to grasp. But I live in the school of the keep it really simple stupid, -for obvious reasons. > Consider (if you have the mathematical ability) how the genii (such as > Poncelet) at the turn of the 19th century might have applied calculus > and the duality of linear motion to the behaviour of gravitational > attractive forces on the chords the sun and moon produce, had there not > been a war on. OOF! There is a hell of a lot of stuff out there on this duality thing. I can not locate what I am after but the idea works like this: View the earth as a disk (the conic section in the theory I was thinking of) and the tangents forming the chord are those of the line(s) of sight of the moon (and sun.) The triangle formed as the tangents, produce a chord that divides the earth into day or night. (There is a tidal day as well as the normally accepted term. It is commonly thought of as being 55 minutes longer than the normal one. Obviously not true for a variety of astronomical reasons. But the geometry is there.) Anyway; draw a series of these chords as the "day" changes and join the dots. Can anyone on sci.maths make some sense of that for me, please? And use small words an idiot can follow, I beg you? <Big snip> Umm, we've got a cat 5 hurricane going, Mick. What? No earthquake predictions? |
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