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khurram usman
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i mean when the moon is full like during 10-20 of lunar month the tides are higher but y?even when the moon isn't full its still there whole in sky? what is the reason?
Oops...I was thinking about the effects of the moon only. I'm sure you're right about what the OP was after.nasu said:The relative height of the tides depends on the relative positions of Sun, Moon and Earth.
The phases of the moon are given by the same thing.
Maximum height of the tides happens at new moon too (see neap and spring tides).
Measured or predicted would show much the same - because the predictions are so reliable, once there had been enough data collected. We virtually stake our lives on the predictions.nasu said:These values are measured and they are for the same place. I mentioned the calculated ones as a secondary bit of info. I don't know the basis for their predictions.
The data seem to show a periodic, reproducible difference between the two tides from a 24 hour period. It appears to be a global effect and not a local one. The actual pattern and height varies wildly, as you mentioned. However the difference is there for most locations. Maybe the local conditions may reduce the difference. On some islands or bays in the Caribbean seems to be only one high tide every 24 hours (Lime Tree Bay is an example) which may be an overlap of two 12 hour peaks.
It seems that the two bulges may have different heights unless there is another effect.
Do you have any reference regarding the forces on the two sides being equal (or almost)?
That is a simplified (over simplified) view of the tides. There is no such wave. Think about it in terms of North America+South America and Africa+Eurasia. These constitute two huge north-south barriers that utterly preclude the existence of such a wave.sophiecentaur said:The tide, itself, consists of a wave which sweeps around the World about once a day with two main components with phases which depend on the relative Sun - Moon positions.
Actually, over three dozen of them. This is a much better model of how the tides work.You need to rely on the analysis of records for anyone place and come up with about a dozen 'harmonic constants'.
Yes, I agree. But you've got to start somewhere and, after the simple discussion of the forces, the notion of a wave sloshing around the Earth is the next thing to think of. It's only in the Southern Ocean that any such wave could hope to propagate. I wonder . . .D H said:That is a simplified (over simplified) view of the tides. There is no such wave. Think about it in terms of North America+South America and Africa+Eurasia. These constitute two huge north-south barriers that utterly preclude the existence of such a wave.
Fundy tides are outrageous! When my wife and I took her mother and aunt on a tour of the Maritimes, we managed to time our visit to Hopewell Rocks so that we arrived at low tide and got to walk around on the sea-floor with those "flowerpots" looming above us. It was pretty darned humbling!sophiecentaur said:I believe there are some places which are dominated by an approximate 24hr resonance and some places where there is a resonance nearer 25 hours. This will produce exaggerated effects from either Sun or Moon, depending on the resonant frequency. See the tides in the Bay of Fundy - 13m range!.
sophiecentaur said:Actually. the forces 'away' and 'towards' the moon (ref the Earth's frame of reference) are more or less equal on either side. The Earth/Moon system is rotating around their common CM (ignore the Sun, for now) which is inside the Earth but offset from its centre (the Earth has a 28 day 'wobble'). If you calculate the sum of gravitational and rotational forces on either side of the Earth's surface, you get pretty well the same answer.
Adding the effect of the Sun's field produces Spring and Neap tides, depending on the alignment. Something that still amazes me, however, is that the small difference in direction, depending on how near the Moon and Sun are relative to the ecliptic, makes such a massive difference to the tidal ranges at the solstices compared with at the Equinoxes.
olivermsun said:http://marine.rutgers.edu/dmcs/ms503/2007/Tides1.htm
Look under "tide generating forces" to see how the forces at zenith and nadir are almost exactly (but not quite) equal.
Sorry. I don't understand. Could I have it in words of one syllable or less?Pythagorean said:So I guess what you're saying is that the gradient comes more from the distribution of centripetal force across the Earth (i.e, as R away from earth-moon COM system)?
Center of earth, not Earth-Moon CoM.Pythagorean said:So I guess what you're saying is that the gradient comes more from the distribution of centripetal force across the Earth (i.e, as R away from earth-moon COM system)?
As they are shown only for about two days, they are both. Or it's hard to say. Taking Boston, on July 11-12 as an example, the smaller maxima are in the morning (around 9-10 AM, it's hard to read the graphs) and the larger ones in the evening (9-10 PM).sophiecentaur said:Measured or predicted would show much the same -
Do the figures you have seen show a higher or lower high tide on the side towards or away from the Moon or the are they day /night related?
Local configuration can be critical, as in the Bay of Fundy situation. Width-restriction and slope of the sea-bottom can result in massive tidal variations. These large variations helped settlers on the west shore of Nova Scotia to flush salt out of salt-marshes very quickly with their clever dikes and flapper-valves, using local streams to rinse out the salt.nasu said:I looked only at a few locations in the English channel (French side). It looks a little more complicated. Maybe due to local configuration.
That is just a function of the fact that tides in Boston are a function of the principal lunar semidiurnal (M2) plus, to a lesser extent, the larger lunar elliptic semidiurnal (N2), principal solar semidiurnal (S2), and the two lunar diurnal terms (K1 and O1). The relation between the smaller and larger maxima will vary over the month, year, and even longer. It is similar to the concept of beats in acoustics (wiki: http://en.wikipedia.org/wiki/Beat_(acoustics)).nasu said:As they are shown only for about two days, they are both. Or it's hard to say. Taking Boston, on July 11-12 as an example, the smaller maxima are in the morning (around 9-10 AM, it's hard to read the graphs) and the larger ones in the evening (9-10 PM).
D H said:That is just a function of the fact that tides in Boston are a function of the principal lunar semidiurnal (M2) plus, to a lesser extent, the larger lunar elliptic semidiurnal (N2), principal solar semidiurnal (S2), and the two lunar diurnal terms (K1 and O1). The relation between the smaller and larger maxima will vary over the month, year, and even longer. It is similar to the concept of beats in acoustics (wiki: http://en.wikipedia.org/wiki/Beat_(acoustics)).
This site specifies harmonic constituents of the tides for Boston: http://co-ops.nos.noaa.gov/data_menu.shtml?stn=8443970%20Boston,%20MA&type=Harmonic%20Constituents
The moon's gravitational pull is the main factor that causes tides on Earth. The moon's gravity affects the Earth's oceans, causing them to bulge slightly on the side closest to the moon and on the opposite side, creating high tides. The areas in between experience low tides.
Tides occur twice a day, approximately every 12 hours and 25 minutes. This is due to the Earth's rotation and the moon's orbit around the Earth.
No, the moon's position in relation to the Earth can affect the size and strength of tides. When the moon is closer to the Earth, the gravitational pull is stronger, resulting in higher high tides and lower low tides. This is known as a spring tide. When the moon is further away, the gravitational pull is weaker, resulting in lower high tides and higher low tides, known as a neap tide.
Yes, the moon's gravitational pull affects all bodies of water on Earth, including oceans, lakes, and even large rivers. However, the magnitude of this effect may vary depending on the size and depth of the body of water.
Yes, the sun also has a gravitational pull on Earth's oceans, although it is not as strong as the moon's. When the sun, moon, and Earth are aligned, their combined gravitational pull results in higher high tides and lower low tides, known as a king tide. Other factors such as the shape of the coastline, wind patterns, and ocean currents can also affect tides.