I just watched a program on PBS Nova and they were talking about Newtons theory of relativity and how it relates to gravity.  They mentioned a sort of fabric that creates the pull on the Earth.  My question is, how come the other planetes do not have this?
122848
Anything with mass has gravity - the bigger the mass the bigger the gravity.  The moon which is quite small compared to earth has much less gravity - look at the footage of the sapcewalks.  Larger planets such as Jupiter or Saturn have much higher gravity - probably so much so that you'd be crushed under your own weight.\n\nThe moon's gravity affects the earth (most noticably in the tides) and to a much lesser extent the other bodies in the solar system affects the earth.
644090
I think the catch to your question is that "gravity would pull us away from the sun at a faster rate tus making gravity faster then light" is complete nonsense. Gravity is two objects pulling on each other. Gravity in and of itself doesn't pull anything anywhere, and it certainly doesn't pull two things away from each other, particularly if one of those two things has just exploded and no longer exists. If you are suggesting that the gravitational pull from the other planets would then pull us away from the ex-Sun, that might be, but the interaction between the remaining bodies in our solar system would be amazingly complex, not easily modelled, impacted by the force of the exploding star, and I see no reason at all to believe that it would cause the Earth to move out of orbit fast enough to escape the light coming from the ex-Sun.\n\nComplete gibberish.
257214
All objects have gravity regardless of whether they are moving or not.\n\n  Moving and object faster has no effect on the strength of its gravitational field. You must be thinking along the lines of magnetism or something.\n\n  Gravity depends only on the mass of an object. a piece of paper sitting on a desk has a gravity field. But becuz the paper's mass is soo small, its gravity field is too weak to be noticed (even by a nearby ant).\n\n   To calculate the strength of an objects gravity field the equation is (M1*M2)/(d^(2))  where M1 = the mass of the object ur finding the gravity stregth for, M2= the mass of any reference object you are using to determine the relative strentgh and d^(2) is the distance between the 2 ojects squared.\n\nlooking at that equation you can see that speed and velocity and rotation does not matter.\n\ntherefore any object a person creates will have gravity, just not gravity thats as strong as a planet's. to do that you would have to make an object as massive as a planet!\n\nCelestial bodies rotate because of gravitational forces exerted on them, but the rotations have nothing to do with the strength of the gravity fields itself.
1654
These answers "seem" correct. But Im not sure thats really the case. Within our solar system there is still gravity. What do you think is holding all the planets in place? Perhaps between systems that might be more true.\n\nThe problem is getting a large mass moving fast enough to really be productive. You still need loads of energy to get a real spaceship moving. We just dont have that tech yet. \n\nRight now scientists are working on a plasma engine. Check it out.
310727
No, because gravity is inflicted by the mass of an object... and we have a very massive object near by that will outweigh any gravity caused by a humble golf ball or a slightly proud bowling ball: it's called the Earth.\n\nBasically, gravity is a force of attraction, so a large object will attract a small object. That is what keeps the moon orbiting the Earth, and the planets orbiting the Sun. Even here on Earth objects are attracted to each other, but the Earth's gravity makes that force almost impossible to measure or detect.
591931
Hmm interesting indeed. Well .. let me see what i think (cause i am not 100% sure yet).... Creation will be as a result of a super nova i agree. So all the particles that are produced will be radiating in an anourmous soup or particle matter. They will according to gravitational influences probably form some kind of motive arms of force that will be radial in form arcing away from the epicentre.. The super nova will create a pressure wave of force outwards. Also, in collapsing the black hole will create threads of gravitational pull around them. So it is likely that they will have pushed each other apart. We then have the period where the mass increases the force of gravity. The question now is does the gravity polarise.. i.e. Is there such thing as positive gravity and negative gravity. Well recent work on gravity fields seems to suggest that there are. So if there are two backholes are they polarised in the same way? Hmmm.. can two black holes form a single blackhole? What about the laws of equal and opposite forces? Would that allow two black holes to converge and eventually combine? Sense would suggest that they would stick together in some kind of orbit with each other. Or, would it be a survival of the fittest? OK i am ready to answer Qs 1,2 and 3 now. \n1. space between them would stay fixed in my opinion. But the concept of space and time would become distorted and stretched as they became closer to each other.\n2. They would change their gravitational polarisation in such a way as to make them co-linked but, they would not consume each other.\n3. The laws of matter and time would change for anything caught in the space between their struggle with each other.
123856
You are correct, but the effects are so insignificant, it doesnt nearly matter.\n\nAll object in the universe have a gravitational attraction to one another.\nTake the Earth and bowling ball example,\nThe Earth exerts a force on the bowling ball, and the bowling ball exerts a force on the Earth.  Both on these forces cause the other object to accelerate towards a common center of mass.  In the case of the Earth's gravitational force on the bowling ball, the force is huge in comparison to the bowling ball's force exerted on the Earth, so much so that we can easily neglect the 2nd force.\n\nLets look at some numbers.....\nIf we say the Earth has a mass of 5.9742 E24 kg and say we will say we have a very heavy bowling ball with a mass of 1000 kg, then we can calculate the gravitaional force between them if we know the distance.  Lets estimate their centers of mass are 6380 (~larger than radius of Earth), we can calculate the gravitational force to be,\nF_g = (G*M*m)/r^2\nF_g = 9789.58 Newtons, which would cause an acceleration of 9.7895 mm/s^2 for the bowling ball and a miniscule 1.63 E-21 m/s^2 for Earth.  To put that in perspective of just how slow acceleration is, if you were to accelerated you car from at a constant acceleration of 1.63 E-21 m/s^2, it would take you about 86500000000000 YEARS to go from 0 to 10 miles per hour!  I think for simplicity sake, Newton did all right.\n\nEDIT:\nYes, the bowling ball very much so does pull on the Earth.  How is the "universe" to know which object is suppose to be the planet and which is the bowling ball?  ALL objects in the universe have a gravititational attraction to ALL other objects.  The Earth pulls in the bowling ball, and the bowling ball pulls on the Earth.  There are 2 equal forces pointed in opposite directions, therefroe momentum is conserved (which is a physical LAW).
90095
the earth doesnt fly towards the sun cuz there r more than one force acting upon it...theres the gravitational pull the sun has on the earth as well as the fact that the moon wants to remain in motion in the same direction.this applies to newtons 1rd law of motion(his first law is that an object will remain at rest until acted upon by another object or it will remain in motion until acted upon by an object..in other words,its inertia)...since the earth has both a side movement and the gravitational pull from the sun...those 2 forces cause the earth to orbit around the sun and not fly towards it or away from it. if u dont understand this...email me (pulga0888@yahoo.com) and ill try to explain it better..........now for ur second question...wat makes the earth spin...the earth spins because of the rotation of the magna and stuff in the earths core..well in the convection zone...im pretty sure thats the answer to the second question but im not positive...if u want me to check then email me.
4454
****Edit based on further details from asker *****\nSailing around the world is sailing within the sperhical confines of our planet.  If there were no athmosphere, or gravity, then we would simply fall off the earth.  However, as gravity is pushing us down, and is affecting the winds, ect within the athmosphere, we are bound to the surface of the water.  \n\nEven though a sphere is included in the define of spheroid, it is a type of spheroid, not the inclusive answer.  The fact that gravity pushes down on us from all around, mainly because the earth is spinning so fast, and other more complicated reasons; the sphereoid holds whatever is on it's surface down to adhere to the confines and shape of such a surface.\n\nEven if the world were flat, or a flattned sphereoid, we woudln't fall off, instead, we'd loop around to the otherside becasue gravity wouldn't allow us to actually 'drop' off the side of the cliff.  The inverse gravity on the other side of the plane would pull us to it's confine, or surface.\n\nSo, there's your answer.  Sorry i didn't get it more clear the first time.\n\nMathamatically you can say that gravity pushes us from all around using a tangent direction.  That means that no matter the point you are on this earth, gravity is pushing down on you within the same confines as any other like region.  As to falling off the earth, if gravity didn't exist, we wouldn't 'fall' exactly; we would more likely be thrown or float off the earth (thrown if the world is spinning).\n\n****End Edit.******\n\nThe world indeed is a sphere, but it is not a perfect sphere, due to the rotation of the earth around it's axis, as well as the rotation of the earth around the sun (central axis), the spinning and speed of the planet make it more of a spehere that jiggles, sometimes squeezed, and sometimes elongated.  But, not by much :) Just a bit :)
154644
What is this gravity that you mention?  :P\n\nGood point tho, funny how it didn't exist until very recently in our history.  *hugs*
232596
You could also talk about the tension on the ropes or chains and explain how the force is perpendicular to the direction of motion and therefore causes a circular or arced path.  It seems obvious because the ropes have a set length, but this is the exact same phenomenon that keeps the earth in orbit.  The gravitational force is perpendicular to the diretion of the earth's movement (on average, of course.  Since the actual orbit is elliptical, it's not a perfect analogy).
183386
This is usually called tidal friction.\n\nThe gravitational flux between two bodies is simply the well-know gravitational equation.  Calculating the heat absorbed/lost by a planet is another much more complicated matter.  There are several mathematical models used, but since some constants aren't well-known, the models usually have a large amount of error.  These are problems that people get Ph.D's just for doing a small amount of work on them, so they're not simple or easily solved systems.\n\nThe earth's oceans are currently assumed to absorb a lot of the energy, so it doesn't go directly into the Earth's crust.  \n\nSee the (vague) reference below.
76842
2 masses dropped from a given height are subject to air resitance (assumed: only phy resistance)...thus earth's pull on either is same & ofcourse insignificant. On the contrary two masses rolled from the top of a slope are subject to the earth's terrain & friction. Also it is believed that the earth's gravitational pull could slightly vary  from point A to B. These "could" cause a variance in their acc.\n\nI believe we're looking at objects of the same mass here.
359829
This paper helps a lot:\nIn the simple Newtonian model, gravity propagates instantaneously: the force exerted by a massive object points directly toward that object's present position.  For example, even though the Sun is 500 light seconds from the Earth, Newtonian gravity describes a force on Earth directed towards the Sun's position "now," not its position 500 seconds ago.  Putting a "light travel delay" (technically called "retardation") into Newtonian gravity would make orbits unstable, leading to predictions that clearly contradict Solar System observations.\n\nIn general relativity, on the other hand, gravity propagates at the speed of light; that is, the motion of a massive object creates a distortion in the curvature of spacetime that moves outward at light speed.  This might seem to contradict the Solar System observations described above, but remember that general relativity is conceptually very different from Newtonian gravity, so a direct comparison is not so simple.  Strictly speaking, gravity is not a "force" in general relativity, and a description in terms of speed and direction can be tricky.  For weak fields, though, one can describe the theory in a sort of Newtonian language.  In that case, one finds that the "force" in GR is not quite central--it does not point directly towards the source of the gravitational field--and that it depends on velocity as well as position.  The net result is that the effect of propagation delay is almost exactly cancelled, and general relativity very nearly reproduces the Newtonian result.\n{end quote}\nhttp://math.ucr.edu/home/baez/physics/Relativity/GR/grav_speed.html
57573
The Earth was formed spinning (like a top) and it just hasn't stopped spinning since then.  There is very little friction that would slow it down (space is pretty empty).\n\nThere are different theories as to why it was created spinning.  But most likely it formed from gas and dust that was swirling, and that angular momentum is still with us today.
236359
I will state this here, in yet another question: THERE IS NO SUCH THING AS CENTRFUGAL FORCE!! Look it up in a basic physics textbook like Giancoli or Serway. Or even do a google search. You have to understand what reference frame you're talking about. The fact that your body tends to want to move to the outside of the curve when your car goes around in a circle has nothing to do with anything other than the fact that your body wants to keep going along in a straight line (conservation of momentum), but the car gets in front of it at every turn (semi pun intended). What is actually happening is that the car is an accelerating reference frame.\n\nAs for the moon/earth question... imagine a man 6' tall throws a tennis ball horizonatally with respect to the earth's surface. The ball will go forward a certain distance (because of it's velocity tangential to the earth's surface) as it falls the ~6' to the ground (because gravity pulls it down). The faster he throws the ball (horizontally), the further it will go before it hits the ground. If he throws it fast enough then the amount that the ball travels forward and the amount that it drops towards the earth's surface can match the curvature of the earth, and the ball will orbit the planet (neglecting air resistance, as we physicists always do) and come around and bonk the thrower in the back of the head. The moon is just a much larger tennis ball, thrown by a much larger man.\n\nYour eqn. is correct, but it only describes the force acting upon the moon. It is not the equation of motion, which detirmines what actually happens to the moon. The equation of motion is:\n\nF = m * a  (F = force, m = mass of moon, a = acceleration of moon around earth)\n\nIn the case of the circular motion of the moon around the earth, "a" is defined by:\n\na = (v^2)/r (where v is the magnitude of the velocity of the moon and r is the center-to-center distance from the earth to the moon)\n\nPlugging one into the other you get:\n\nG * M * m/r^2 = m * (v^2)/r (where M is the earth's mass)\n--> G * M/r = v^2\n\nSo, as long as the tangential velocity, v = sqrt(G * M/r), the moon falls just enough towards the earth as it travels just enough tangentially second by second, that it continues to orbit around the earth. (Note: there is NO CENTRIFUGAL FORCE anywhere in any of these eqns.!!)
246558
two reasons, gravity and angular momentum.  Gravity tends to pull matter into one centralized spot, but angular momentum must be conserved.  That mass that escaped being part of the sun attracted mass to centralized locations, what became the planets, flattening things out to a disk shape