Gravity push or pull

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noahnott

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First off: im new <br /><br />I bet this is a simple or already asked question. Does gravity push or pull, or neither? I was just having a little argument with a classmate about it. I kept switching sides between push and pull =P
 
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kmarinas86

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Think of two ice skaters. Pushing would cause them to move away from each other. Pulling would bring them closer.
 
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noahnott

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Thats not really what i meant. I meant you know how magnets "attract" or pull on one another. So does gravity act like a magnet, or are there little somethings going inward (being gravity) which is a push (this would kinda be like pressure pushing on everything instead of pulling). I know im confusing.
 
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siarad

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Well if you believe in Einsteins contorting of space, the 'bowling ball' model then I guess it pushes. By what mechanism mass connects to space I know not.
 
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harmonicaman

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<i>"By what mechanism mass connects to space I know not."</i><br /><br />I believe gravity is caused by the basic conflict between all the "m" and "E", (static mass and energy) in the universe and "c", (the continuous expansion of space and time).<br /><br />These two entities are not compatible. The "m" and "E" was all created at the time of the Big Bang and does not change. <sup>(1.)</sup> The "c" is constantly being created and must eddy around the existing "m" and "E", and this interaction manifests itself as gravity -- or in other words, the curvature of time and space bending around mass is what we observe as gravity. It isn't really a force at all, just an attribute of E=mc<sup>2</sup> within our expanding singularity universe.
 
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mvisvitae

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In reply to:<br /><br />or in other words, the curvature of time and space bending around mass is what we observe as gravity. It isn't really a force at all, just an attribute of E=mc2 within our expanding singularity universe. <br /> *****************************************<br /><br />MIT proved that gravity was not a constant [9.8 meters per second squared]...therefore neither is the curvature of time and space bending around mass.<br />c2 = Em/vt <br /><br />Also if you can square the speed of light then you can cube it......and therefore exponentiate it to infinity<br /><br />Note: Every action has an equal and opposite reaction
 
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kyle_baron

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<i><br />Does gravity push or pull, or neither?</i><br /><br />You left out the answer in your question. The answer is that gravity does both actions, it pushes and pulls, or attracts, and repells. We all know that gravity attracts, or pulls matter inward. A perfect example of gravity pushing or repelling is when a star goes Super Nova. The outer layer collapses (implodes), falling inward towards an iron core. Once the gases hit the iron core, they repell, push, or bounce off the core, and the star explodes. <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>
 
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vogon13

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Do I infer from your statement that when you hoist a Dr. Pepper, gravity repels the glass from the table and impels it towards your lips?<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>
 
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doubletruncation

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While it's clear that we don't really know everything about how gravity works (our fundamental theory of gravity is inconsistent with our fundamental theories of other forces), if you were asked on a physics test whether gravity pushes or pulls, I think the answer would be simply that it attracts (so I would say "pulls"). Absent any other pushes or pulls, two objects with mass will accelerate towards each other by Gm1m2/r^2 - whether you would call that a push or a pull is a bit of a symantics issue (my preference would be for pull). This is the Newtonian point of view, and from this point of view there really is nothing more to gravity than the force specified by the above law, why it happens or if there's some sort of medium that transfers the force (instantaneously in Newton's theory) are questions that are not addressed by Newton's theory of gravity. In Einstein's theory of gravity, gravity is not a force so it neither pushes nor pulls. Instead, energy(mass)/momentum cause space to be curved. Absent any forces (not gravity) objects will travel on the straightest possible line that they can through space/time, which to many observers will appear to be curved. That of course is not a very good explanation of Einstein's theory (so don't feel dumb if it didn't make much sense <img src="/images/icons/smile.gif" />), to really explain the theory in a way that makes sense I think requires a lot of math/physics which you can learn over time if you wanted, but suffice it to say that I think gravity neither pushes nor pulls from Einstein's point of view. <br /><br />Some other posters made reference to the bounce at the core of a supernova. I could be wrong, but as I understand it, the bounce itself is caused by processes other than gravity. (If I remember right, the current theory is that a sound wave causes the star to bounce back in supernova - that would mean electromagnetic forces are responsible for the bounce). While there are some experiments that might be interpre <div class="Discussion_UserSignature"> </div>
 
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torino10

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I was under the impression that gravity is an attraction force so I would guess pull. As a side question can changes in gravitational fields have effects that move faster than light?<br /><br />
 
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doubletruncation

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<blockquote><font class="small">In reply to:</font><hr /><p>As a side question can changes in gravitational fields have effects that move faster than light?<p><hr /></p></p></blockquote><br /><br />As far as I know, not in Einstein's theory. There may be some superluminal effect that I'm not aware of - but you can be sure that it wouldn't transmit information faster than the speed of light. Gravitational radiation, for example, propogates at the speed of light. As far as I understand it, it's just like electromagnetic fields where if you make a local change to source of the field the change in the field will propogate out at the speed of light (the change in the electromagnetic field is essentially what light is). So any super-luminal effect would have to be similar to say the shadow of an object moving 1000 km/s away viewed from a location more than 100 times farther from the object than the object is from the light source - if a bunch of observers were to time when the shadow passed them they would conclude that it's moving faster than light, but it's not like they could transmit information to each other via the shadow. <div class="Discussion_UserSignature"> </div>
 
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siarad

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It seems necessary to define the medium.<br />In space it seems to pull but as any sailor or balloonist knows it does both in their medium.
 
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doubletruncation

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<blockquote><font class="small">In reply to:</font><hr /><p>In space it seems to pull but as any sailor or balloonist knows it does both in their medium<p><hr /></p></p></blockquote><br /><br />I think a physicist would attribute the push part of the bouyancy force to electromagnetic forces ultimately responsible for the pressure that holds you up. While the value of the pressure in the fluid is set in part by gravity, I think a physicist would say that gravity is not actually the force that's holding you up. <div class="Discussion_UserSignature"> </div>
 
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a_lost_packet_

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<font color="yellow">noahnott - First off: im new <br /><br />I bet this is a simple or already asked question. Does gravity push or pull, or neither? I was just having a little argument with a classmate about it. I kept switching sides between push and pull =P </font><br /><br />Think about your question for a moment. "Does gravity push or pull, or neither?"<br /><br />What defines it? What is "push?" What is "pull?" Is "pushing" something merely "pulling" it in the opposite direction?<br /><br />Those are relative terms aren't they? Thus, the answer is relative to the observer. In this case; the point at which you define gravity as having acted "from." <br /><br />The best answer, in my opinion, would be that gravity "attracts." <div class="Discussion_UserSignature"> <font size="1">I put on my robe and wizard hat...</font> </div>
 
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kyle_baron

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<i><br />Do I infer from your statement that when you hoist a Dr. Pepper, gravity repels the glass from the table and impels it towards your lips? </i><br /><br />Amusing question. But non of those actions involve negitive PRESSURE. <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>
 
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kyle_baron

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<i><br />so its both if i understood correctly </i><br /><br />Absolutely, according to Physicist Brian Greene. In his own words: According to general relativity, pressure can indirectly exert another force- it can exert a gravitational force- because pressure contributes to the gravitational field. Pressure, like mass and energy, is a source of gravity. And remarkably, if the pressure in the region is negitive, it contributes a gravitational PUSH to the gravitational field permeating the region, not a gravitational pull. <br /> <br /> <br /><br /> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>
 
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vogon13

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The heating at the core of the supernova expanding the materials therein against the pull of gravity is fundamentally different than your muscles hoisting a can of Dr. Pepper against the gravitational field of earth?<br /><br />Howzthatbe ?<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>
 
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doubletruncation

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<blockquote><font class="small">In reply to:</font><hr /><p>And remarkably, if the pressure in the region is negitive, it contributes a gravitational PUSH to the gravitational field permeating the region, not a gravitational pull.<p><hr /></p></p></blockquote><br /><br />Right, which is why dark energy, manifested as a repulsive force giving rise to the accelerated expansion of the universe, can be interpreted as something with negative pressure (and hence repulsive gravity). But, I don't think there are any other examples of a negative pressure substance that we know of. Please correct me if I'm wrong - but where, aside from cosmology, do you have to worry about negative pressure and repulsive gravity? <div class="Discussion_UserSignature"> </div>
 
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kyle_baron

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<i><br />The heating at the core of the supernova expanding the materials therein against the pull of gravity is fundamentally different than your muscles hoisting a can of Dr. Pepper against the gravitational field of earth? <br /><br />Howzthatbe ? </i><br /><br />Alright, my supernova example might not be the best example of negitive pressure along with repulsive gravity, but you're going to have to get off the Dr. Pepper ( it's affecting your spelling/english)<img src="/images/icons/wink.gif" />. Because, as doubletruncation said, negitive pressure along with gravity, are only found in cosmology, not with a can of Dr. Pepper. <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>
 
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alokmohan

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General theory of relativity deals with gravity.Nothing but warping of space time.
 
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