when the earth revolves around the sun, what is conserved?? angular or linear momentum??
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The angular momentum is conserved, and linear is not.\n\nGravity is a central force (meaning one that only depends on the radial distance between objects) and central forces conserve angular momentum.  \n\nA way to think of it is this:  angular momentum is something like mass x radius x linear velocity.  Watch an orbit simulation and you'll notice that as earth gets closer to the sun (radius decreases) it's speed increases.  Also as the earth gets farther from the sun, it slows down.  The two trade off (i.e. increase radius, decrease linear velocity, and vice versa) in a way that their product stays constant.  \n\nThe linear momentum is not constant for the same reason.  Linear momentum is mass x velocity, and from the above it's easy to see that velocity is not constant (there is one wrinkle:  if the orbit is circular then the magnitude of the velocity is constant, but its direction is not; so the velocity, a vector quantity that has magnitude and direction, is changing).\n\n\nI hope that helps.
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The Earth is rotating around an axis (called its rotational axis). Some objects rotate about a horizontal axis, like a rolling log. Some objects, such as a skater, rotate about a vertical axis. The Earth's axis is tipped over about 23.5° from vertical.\n\nHow do we define up and down in space? What would "vertical" mean? For the Earth, we can think of vertical as straight up and down with respect to the plane in which the Earth orbits the Sun (called the ecliptic).\n\nEarth's rotational axis points in the same direction relative to the stars, so that the North Pole points towards the star Polaris. Think of the Earth as a spinning top, tipped over to one side. Over very long time periods (thousands of years) the direction of Earth's axis slowly changes due to precession.\n\nThe Earth rotates around once in 24 hours - that's a rate of 1000 miles per hour!. The time it takes for the Earth to rotate completely around once is what we call a day. It's Earth's rotation that gives us night and day.\n\nThe combined effect of the Earth's tilt and its orbital motion result in the seasons
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I answered this yesterday, but...\n\nWhat makes the Earth Spin...\n\nAngular Momentum. Think of a figure skater pulling their arms closer to their body while spinning, sudennly they are spinning VERY fast, then they let their arms out, and they slow down. This is because the arms still have the same amount of rotational energy as they did when they were further from the body, but when they are pulled close, they don't have as far to go to complete one rotation... the radius and circumference are smaller but the distance covered is the same over the same amount of time. This means faster rotation.\n\nHow does that have anything to do with the Earth? Simple. When the Earth formed, it formed by collecting bits of matter from space, and these bits of matter, ranging from dust to huge asteroids and larger, were all like tiny arms, adding rotational energy to the earth as they came in closer and stuck. \n\nRight now, the moon is slowing the earth's rotation as it slowly moves away from the Earth--again, this is the same process. How can this be when the moon doesn't even touch the Earth? Gravity. Gravity makes the earth and moon behave almost as if they were touching. The short explanation is that the center of gravity of the earth-moon system lies just below the surface of the earth, causing tides. Since the moon is moving away, it requires less orbital velocity to maintain it's orbit, and so the tides slow the earth more as the moon's orbital speed slows.\n\nEventually, the earth and Moon may both be tide-locked to each other, and this will happen long before the earth is tide locked to the sun (the tides have slowed rotation of the earth to the point where it always has one side facing the moon (or sun)).\n\nWhat makes the earth not stop spinning?\n\nAs mentioned before, angular momentum. The earth's surface can be slowed, but that energy has to go somewhere--it goes to speeding up the orbital velocity of the moon, which is why the moon is moving further from the earth...\n\nThe earth is moving around the sun because of the way the sun and all the other stuff in the solar system formed--from a cloud of gas and dust that collapsed into a spinning disk. The mechanics of the whole thing is still being learned and debated. As long as the Earth keeps moving in a straight line perpendicular to a line drawn between the Earth and the Sun, the Earth will continue to fall toward the Sun (by gravity) at exactly the same speed that it is flying perpendicular, and thus, like a ball on a string, it will follow a curved path around the sun.
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Yes, the Sun revolves around it's own axis, just like the Earth.  It spins around every 27 days.  It just doesn't ORBIT anything.\n\nedit: actually, it orbits the galaxy.  Takes a few hundred million years.
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linear momentum of a moving body is the "thing" that keeps it moving, given by mass x velocity.\n\nangular momentum is the same "thing" that keeps an object spinning about its axis.
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A person's angular momentum is I*w (should be omega, but I don't have that on my keyboard.)  Omega is the angular velocity, how fast a person is spinning.  Just as momentum is conserved, as is angular momentum.\n\nI is the rotational inertia, aka the moment of intertia.  The most simple way to determine this value is mass*distance^2.  By lowering the radius, the angular velocity must be increased to conserve angular momentum.
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Kepler's Laws \nIllustration of elliptical orbit of a planet with the sun at the left focus. The semi-major and semi-minor axes are denoted by  and . The shaded triangular area element is needed for the discussion of Kepler's second law. Perihelion and aphelion are respectively the points on the orbit nearest and farthest from the sun. Note that at perihelion and aphelion the velocity is purely tangential, i. e., the velocity component along the radius vector is zero.  \nJohannes Kepler, using data compiled by Tycho Brahe, inferred three laws governing the motions of planets in the solar system: \nPlanets move in elliptical orbits with the sun at one focus. \nEqual areas are swept out in equal times by the line connecting the sun and the planet. \nThe square of the period of revolution of the planet around the sun is proportional to the cube of the semi-major axis of the ellipse. \nThese laws were instrumental in the development of modern mechanics and the universal law of gravitation by Isaac Newton. \nShowing that the first law is consistent with Newtonian mechanics is mathematically more difficult than we can undertake in this course. However, the second law turns out to be a simple consequence of the conservation of angular momentum. It shows an elliptical orbit with the area swept out as a planet moves from position 1 to position 2. We estimate this area as , where we have ignored the small unshaded part of the area to the right of the shaded triangle. The distance traveled by the planet in time  is , so the magnitude of the velocity is . However, in computing the angular momentum, we need the tangential component of the velocity, i. e., the component normal to the radius vector . This is simply . The angular momentum is , where  is the mass of the planet. Combining this with the formula for  results in \nSince gravitation is a central force, angular momentum is conserved, which means that  is constant. Thus, we have shown that conservation of angular momentum is equivalent to Kepler's second law. \nKepler's third law turns out to be a consequence of the universal law of gravitation. We can prove this for circular orbits. We know that a planet moving in a circular orbit around the sun is accelerating toward the sun with the centripetal acceleration , where  is the speed of the planet's motion in its orbit and  is the orbit's radius. This acceleration is caused by the gravitational force, so we can equate the force divided by the planetary mass to , resulting in where  is the mass of the sun. This may be solved for Eliminating  in favor of the period of revolution  results in ...This agrees with Kepler's third law since the semi-major axis of a circle is simply the radius .
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(a) The angular speed of the earth is the circumference of the orbit divided by the time taken to complete one orbit.\n\nAngular speed = (2*pi rad) / 3.16x10^7s = 1.987x10^-7 rad/s. \n\n(b) The tangential speed is the same as the angular speed, but in different units (probably m/s).\n\n1 rev/yr * (1/3.16x10^7) yrs * (2*pi*r)m/rev = 29810 m/s\n\n(c) The magnitude of the centripetal acceleration is the radius times the angular speed squared.\n\na = r*w^2 = 1.50x10^11 * (1.987x10^-7)^2 = 5.924x10^-3 m/s^2\n\nThe direction is toward the sun.
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Angular momentum is conserved,\n\nAngular momentum is (inertia * angular velocity)\n\nInertia for a disk = .5*mass*radius*radius = 0.5 * 5.6 * .2 * .2\n\nThe initial angular momentum is then: 0.5 * 5.6 *.2 * .2 * 1.8 (note that is in rev/s)\n\nThe inertia for the clay is: 0.5 * 3.1 * .04 * .04\n\nThe final angular momentum of disk and clay is then: 0.5 * ((3.1 * .04 * .04) + (5.6 * .2 * .2)) * f   where f is the answer you are looking for.\n\nInitial angular momentum = final angular momentum:\n0.5 * 5.6 *.2 * .2 * 1.8 = 0.5 * ((3.1 * .04 * .04) + (5.6 * .2 * .2)) * f or\n\nf = (5.6 *.2 * .2 * 1.8)/((3.1 * .04 * .04) + (5.6 * .2 * .2)) in rev/sec
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The earth turns with respect to the motion of force which was placed upon it with in the vacuum of space, and also with respect to the vacuum of space there is no friction to slow it down, therefor it shall continue to spin forever if it's motion is uninterrupted, or unaltered by another matter energy object of aether large size, or fast speed impacting it with direct respect to the angle of the interaction.\n\nas for your second question the axis is the center point at which the spin turns, and is therefore recognized by us with respect to the earths motion spin as the axis, and if the motion and direction of spin were changed tomorrow to be perpendicular of that which it is today, then the new axis would be perceived tomorrow as existing at some point at which we recognize the equator today.
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The Earth rotates on its access and revolves around the Sun.
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There is rotation-the spinning of Earth on its axis\nAnd:\nThere is revolution-The orbiting of Earth around the sun
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If you're speaking of the motion of Earth on it's axis or it's rotation about the sun, the answer is the scientific principle of Inertia, read now!\n\nThe principle of inertia is one of the fundamental laws of classical physics which are used to describe the motion of matter and how it is affected by applied forces.Inertia is the property of an object to resist changes in velocity unless acted upon by an outside force.Inertia is dependent upon the mass and shape of the object. The concept of inertia is today most commonly defined using Sir Isaac Newton's First Law of Motion, which states:\n\nEvery body perseveres in its state of being at rest or of moving uniformly straight ahead, except insofar as it is compelled to change its state by forces impressed. [Cohen & Whitman 1999 translation]\n\nThe description of inertia presented by Newton's law is still considered the standard for classical physics. However, it has also been refined and expanded over time to reflect developments in understanding of relativity and quantum physics which have led to somewhat different (and more mathematical) interpretations in some of those fields.\n\nNow read more at the links below:
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Ask your son to turn around in a circle once per day.  That is the rate  of the earth spinning.   One rotation per day.  Did he get dizzy?  \n\nSpinning is angular speed or angular frequency( the rate it turns through an angle), not the speed, tangent to the circumference of the earth.\n\nThe earth spinning is improperly linked to 1000 mph.  The earth spins one time per day.  The surface velocity is 1000mph at the outer surface of the earth, but that is just like going straight at 1000mph.\n\nThe surface speed of the earth is undetectably with out a frame of reference.  Just as speeding in a car...without looking out the window, you don't know if you are moving that fast.  We only detect a change, acceleration.  The earth spins so slowly, we don't detect the angular frequency as being dizzy.
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It's pretty arbitrary isn't it? Look down on the North pole and the earth is turning clockwise, look down on the South Pole and it's the other way around.\n\nA more interesting question is: why are (almost) all planets orbiting and rotating in the same direction?\n\nThe solar system, earth included, is supposed to have formed from a dust cloud that contracted due to gravity. This cloud rotated in a certain way. As spin has to be conserved, all bodies in the solar system rotate in the same way.
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Due to the direction of rotation of the earth, remember the sun is not actually moving at all we are rotation and rotating around the sun (days, years).  Galilao got into a lot of trouble with the vatican to teach us this :)
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The Earth spins from west to east at about 900 mph. Looking from above the Earth's North Pole, the Earth rotates counter-clockwise around the Sun.