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I know that tide is caused by the gravitational pull of moon but what I don't know is how it effects on water. I have actually these doubts.

  1. Why does gravity of the moon creates tides only in water?

  2. Are there other things (other than water) where tides are created in earth( I have heard that, in some moons of Jupiter tides(of ground) can be found on the surface due to Jupiter's gravity)?

  3. If we take a bowl of some length; lets say 30 cm diameter and fill it with water and keep it in a full moon night. Whether it will create tide?

  4. If moons gravitational pull can cause tides in seas, then why a sailor can't feel the gravitational pull of moon?

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(1) Rather complicated, has to do with centripetal force as well as gravity. (2) Yes, but it will be only for gas giants. (3) No, see (1). 4) Since there are other, stronger unbalanced forces eclipsing it. And he's tiny. See (1).$$\text{}$$ These are slightly related, so I won't tell you to split them. It would have been better to make (1) your main question, ask (4) as a separate one, and stuff (2) and (3) into (1) as supplementaries--they're sort of trivial if (1) is already answered IMO. – Manishearth Apr 16 '12 at 6:05
Maybe interesting in this respect is Jupiters moon Io en.wikipedia.org/wiki/Io_%28moon%29 This moon has active vulcanoes, that cannot be explained by it size. These are caused by tidal effects. Not on water, but on solid material. – Bernhard Apr 16 '12 at 6:51

2 Answers

up vote 4 down vote accepted

You ask:

How gravity of the moon creates tides only in water?

This is wrong. Tides are created by the moon on all materials on earth that have some elasticity. The raising and falling of the ground has been measured at the beams in CERN, for example. The solid ground tides are called earth tides and their height can be 40cm.

Is any things( other than water) also create tides in earth( i heard that some moons in Jupiter has tides(of ground) on the surface due to Jupiter's gravity)?

You mean "get tides", not "create tides". It is the moon mainly and not the water that creates the tides.

There is some effect in the tides from the large planets and the sun's gravitational field. That is why tide tables are needed. The source is not one. Yes there are tides on planets that have moons and some elasticity in their composition.

If we take a bowl of some length; lets say 30 cm diameter and fill it with water and kept it in a full moon night whether it will create tides?

You should measure the bowl during the tide cycle, which is close to a 12 hour one ; the full moon or not is a secondary effect. Look at the explanation in the link. You will need accurate measurements and to consult tide tables for your particular location.

If moons gravitational pull can cause tides in seas, then why a sailor cant feel the gravitational pull of moon?

The sailor and all of us feel the vector sum of the gravitational forces impinging on us at our location. One cannot distinguish the individual components unless on does a fit to the components of known gravitational sources. We are not equipped biologically for that , so it must not offer an evolutionary advantage :) . The water is lifted and the boat is lifted with the water, no?

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Does it really mean a bowl of water lift up?? I guess, tides are formed in oceans because there's room for water to rise from the low tide region. In a bowl, every part of the water experience same pull, and hence basically because the pull is not strong enough to change the density of liquid so the level should remain same!!! – Vineet Menon Apr 16 '12 at 9:25
@VineetMenon if you look at the link, you will see that every twelve hours or so even the ground we stand on is pulled by the moon+. Everything moves up, including the bowl of water. In addition, because water has different "elasticity" the water in the bowl will be affected differently than the table and one might be able to measure the difference with accurate enough methods. I would think interferometry to start with. Now if we are talking of tide within the bowl of water, i.e. the surface pulled more than the botom, the effect would be infinitessimally small, although there in principle. – anna v Apr 16 '12 at 10:50
I think the most visible effect on the water in the bowl would be when water is pulled left and right. When moon is exactly above the bowl, I doubt there would be any visible effect. Except that the weight of the ball+water will be a tiny fraction smaller... – Pygmalion Apr 16 '12 at 13:56
   Explaining Gravity


   The explanation of gravity will lead us to understand the law which describes the nature of all things in the Universe or The Fundamental Law Of the Universe ( F.L.U ).
        In principle, the Fundamental Law of the Universe describes the nature of all things in the Universe inclusive intelligibility and the mechanism of life, providing us with the explanation of the physical objects from the microscopic-scale (quarks,leptons,atoms) to the macroscopic-scale (planets,stars,galaxies,cluster of galaxies) of the Universe. The definition of F.L.U. derives from the behaviour of a system of opposites structured as an mechanism which represents a model for all objects in the Universe. The structure and the way this mechanism behaves are based on the principle of first cause. Knowing the first cause, from which this principle emerged, we can explain all things in the Universe, in the sense that F.L.U provides us with the patterns of similarities for reviling the truth about the reality of all things. From this, we can assume, that a fundamental or elementary particle ( quark,lepton ) forms an mechanism which its structured similar to the mechanism of a planet, star, galaxy and the whole Universe.            
         At the macroscopic scale of the Universe, the explanations through this model of mechanism correspond with statistical surveying of the visible structure in the Universe, to the prediction of cosmic microwave background and the bottom up structure formation. Moreover, F.L.U.explains: the various astronomical observations of galaxies and galaxy clusters; the behaviour of the early Universe including the nucleosynthesis process; the behaviour of the later Universe and the expansion process; the cause of the Big Bang; the cyclic model of the Universe and its limits for space and time; all the astronomical observations without recourse to some of the alternative theories (modified gravity,and quantum gravity), and with no need of non-baryonic matter (dark matter and dark energy) to explain the large scale structure of the Universe.  Time and space represent the fundamental characteristics of this model of mechanism which explains the various gravitational mysteries from first principles, not through empirical methods. In relation to planet Earth, F.L.U.explains: 

why the magnetic poles are not static, they wonder as much as 15km every year; why the magnetic poles change in size and position and are not at directly opposite positions on the globe; when geomagnetic reversals occur, and others. From the Earth and the Moon interaction, we can explain important observations inclusive the polarisation of gravity.The polarisation of gravity explains the elliptical orbits of planets, the apsides of the planets orbits and more. At the microscopic scale of the Universe, F.L.U. provides us with the explanation of all the mysteries arising when we describe how matter and energy behave at the quantum scale in ways that differ from what experience would lead us to expect. The fundamental or the elementary particles (quarks,leptons) that are described in particles physics through the Standard Model are not fundamental, they represent composite systems. Observables like mass and charge of the particles, which in quantum physics are described as numbers without physical meaning, represent in fact significant manifestations of the composed particles as a unitary system. Also, F.L.U. explains why electrons are confined into clearly defined, quantized orbits, and could jump between these, without getting close to the protons or nucleons of the atoms. Quarks charges(+2/3,-1/3)are not the right ones. F.L.U. allow us to observe the grand unification directly in experiments and unify in a simple and elegant way gravity with the other 3 fundamental forces of nature (electromagnetism,weak and strong forces) and explains why the electric charges of electrons and protons cancel each other exactly to extreme precision, as this property is not explained in the Standard Model of particles physics. The model of nature described by the F.L.U. takes an analogous position to quantum physics and classical physics, resulting in the reconciliation of quantum physics and classical physics.
For understanding gravity we can begin with direct observations on planet Earth for identifying patterns of similarities in its structure which explain the polarisation of gravity. Each pattern is represented by a couple of forms with the same volume of different or contrary elements. On planet Earth, first such a pattern is found on Earth's crust, where the oceanic water and the continental crust represent two contrary elements, and from our data we know that water cover 70% of the planet and the continental crust 30% of the Earth surface, but considering that on continent the crust is in average 30 km thick and the oceanic crust is in average 10 km thick, we can assume that the volume of water and the volume of continental crust on Earth's layer of crust are equals.This pattern of contrary elements ( liquid and water) forms a system of opposites gravitational poles and this fact can be verified in the interaction of the Moon - Earth system.When the Moon orbit the Earth always faces Earth with the same pole of gravity, that means that the Moon will attract one of the two elements that form Earth's layer of crust and repel the other. From direct observation we can see that the Moon is repealing the oceans water by observing the shape of the oceans on the globe when the Moon orbits the Earth, also this fact is proved by direct observations of the ocean's tides, which means low tide when the Moon projection is perpendicular on a spot that we chose on ocean's surface or ocean's shore and almost six hours before the Moon reaches that point and almost six hours after the Moon passes that point the tide is up, this is clear evidence that the Moon repeals the water on Earth's surface. Another pattern of contrary elements that is easy to observe on Earth its represented by the layer of atmosphere, where halve volume of the atmosphere is hot gas during day time and the other halve is cold gas during night time, hot air and cold air as two equal volumes form a system of two contrary elements as gravitational poles of this system. Next system of opposites in describing the Earth its given by the electromagnetic field which extends tens of thousands of km's into space, with the electric and magnetic fields as two contrary elements for defining the gravitational poles for this system. These three systems of opposites ( the crust layer, the atmosphere layer and layer of the electromagnetic field ) interact each other through gravity, and direct observations of this phenomena come from the fallowing examples: The atmosphere, as a system of opposites, changes its position to the Earth's poles between summer and winter interacting with Earth's electromagnetic field, and this explains the 15km migration of magnetic poles every year. With the physical observables that we can measure for the Earth atmosphere and for the Earth electromagnetic field we can succeed in finding the connection of gravity to electromagnetism.
If the distribution of oceans water and the continental crust changes its ratio between north and south hemispheres of the Earth, can lead to the reversal of Earth's magnetic poles, and this reversal also occurs if the inner-core and the outer-core of the Earth are changing their tending of rotating relatively faster or slower one to another. Also, the distribution of oceans water and continental crust on Earth's hemispheres influences the orbit of the Moon.
All the explanations in relation with planet Earth come from observing the interactions between all the layers and sub layers that form the Earth's inner system of opposites, and from the interaction of the Earth's inner system of opposites with the Earth's outer system of opposites. The inner and outer systems of opposites which are structured in an mechanism, represent a model for all the objects in nature. With this model of mechanism its easy to understand that the interaction between two orbiting bodies in the Universe, means attraction and repulsion between them in the same time. Similar to the Moon showing the same gravitational pole when orbits the Earth, all bodies that orbit in Universe are showing the same gravitational pole to the body which they orbit, and this explains the elliptical orbits of planets. For example, when the Earth orbit the Sun, for halve of the orbit the Earth and the Sun are showing the same poles of gravity which explains the perihelion of the planet Earth, and for the second halve of the orbit the Sun and the Earth are showing the opposite poles of gravity and this explains the aphelion of the planet Earth.
These observations and all others that we can obtain directly or through experiments will provide us with the knowledges we need in understanding gravity and the principle which govern our Universe.

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