Has it ever been proved that gravity is proportional to mass?

[djHiran]

No! This was an assumption that Newton made and others followed, but since nobody pretends to have actually weighed the Sun or the planets it has never been checked. Laboratory experiments have attempted to check it for small bodies, but (a) it is impossible to separate gravitational from electrostatic effects and (b) we have not been told all the facts. The various anomalies such as variations with temperature and with the coating on the object have not reached the text books.

Perhaps even more relevant are a few chapters in Matt Edwards' book, "Pushing Gravity". Here you will find details of probably the only experimental tests ever to have been made that investigate the possibility of gravitational shielding. They were performed by Quirino Majorana round about 1920. Despite his best efforts they were inconclusive and (like Dayton Miller's work) need to be repeated, the results were compatible with a degree of "gravitational absorption" that would mean that the Sun could be about three times as massive as we currently think.

So, the discussion is open... Please feel free to post your opinion here.

 

[||~R_girl~||]

Well... 1st of al let me start by sayin dat i suck at phy

n r u sayin dat gravity is directly proportional to d weight of a body...? hmmm znt it a constant 4 all d bodies... Dsnt d gravitatinal acceleration remain to b 9.81 for all d bodies on erth regardles of its weight...

Btw js ignore dz if am tokin compltly smthng difrnt cuz i comntd on wat i saw in d title only... Hehe.....

 

[djHiran]

Gravity being directly proportional to the mass of a body is only an assumption in Newtonian physics. r-girl, thats exactly what I meant. here we can start by formulating an equation for the force between two bodies A and B with masses M and m respectively.

Force F = G*M*m*(1/r)^2

Where r is the Newtonian distance (distance at rest) between A and B.

Here G is the proportionality constant.

As to what R-Girl says, G*M*(1/r)^2 = 9.81 m/s^2 and is the notion most of us generally accept. The fact is this 'magical' number is only an experimental measurement, and is subject to a certain error (error theoretically).

We carry out our calculations based on the assumption, and end up with reasonable results. But it is not logical to think that our assumption is correct.

For example, one can say that we stand on the inner surface of a sphere. Based on that assumption one may easily conclude that we can travel all around the world and eventually reach our starting point. Can you conclude that our assumption is correct?

 

[||~R_girl~||]

Gravity being directly proportional to the mass of a body is only an assumption in Newtonian physics. r-girl, thats exactly what I meant. here we can start by formulating an equation for the force between two bodies A and B with masses M and m respectively.

Force F = G*M*m*(1/r)^2

Where r is the Newtonian distance (distance at rest) between A and B.

Here G is the proportionality constant.

As to what R-Girl says, G*M*(1/r)^2 = 9.81 m/s^2 and is the notion most of us generally accept. The fact is this 'magical' number is only an experimental measurement, and is subject to a certain error (error theoretically).

We carry out our calculations based on the assumption, and end up with reasonable results. But it is not logical to think that our assumption is correct.

For example, one can say that we stand on the inner surface of a sphere. Based on that assumption one may easily conclude that we can travel all around the world and eventually reach our starting point. Can you conclude that our assumption is correct?

goshhh.. U sound lyk a nerd no offenc plz... Ur explantion was sooo nyc n clear... Bt u dint get wat i meant in ma previous post.. Did u?
I sed dat it is NOT proportional to d mass.. N u say dat it is... Watevr its value is, D gravity at a certain point is suposd to b d same for ANY object ryt..

Nywy m no gud at diz.. So i quit.. Gud luck wit d discusion..

 

[akolla]

how come gravity propotional to the mass of a body? that is totaly wrong.

 

[akolla]

For example, one can say that we stand on the inner surface of a sphere. Based on that assumption one may easily conclude that we can travel all around the world and eventually reach our starting point. Can you conclude that our assumption is correct?

and can you also explain this more?

 

[Mojo]

I think the issue here is that every one who has commented on this thread so far is assuming that the gravitational force referred to in the initial post is the gravitational force between Earth and another object, whereas I believe that the initial post was referring to the gravitational force between any two objects in space time.

Newtons law of gravitation assumes that there is a force between any two objects in space which attract them to each other and that this force is inversely proportional to the square of the distance between the two objects, where as it is directly proportional to the multiple of the mass of two objects.

The constant (9.8 m/s^2) is the gravitational acceleration which is a constant for earth ( assuming newtons gravitational law is correct) . But this does not in any way imply that the gravitational force between the earth and any other object is constant . In fact it never is , since its dependant on the mass of the other object and the displacement between the earth and that object.

I think in modern physics, a somewhat different proposition has been forwarded which is attempting to explain gravitational attraction. This proposition suggests that massive objects ( i.e. any object with a mass ) warps the space time around it, and therefore it gives rise to an illusion of one object attracting the other , where as there is no real force between the two objects called gravitational attraction.

For example, if we take a black hole singularity, the mass at the center of the blackhole is infinite, and this will bend the space time around the black hole in such a manner that space-time will collapse in on the blackhole giving the illusion that objects that get close to the black hole are sucked inside, whereas what really happens is that the space time for those objects is warped in a manner where it appears to collapse in on the blackhole RELATIVE to a distant observer who is far enough to not have his/her space time significantly bent by the black hole. Therefore , the gravitational pull between two objects according to this model, is observer dependant, and is the relative difference between the spacetime warp caused by the more massive object , on the spacetime adjacent to the smaller object, and that of the observer

 

[akolla]

I think the issue here is that every one who has commented on this thread so far is assuming that the gravitational force referred to in the initial post is the gravitational force between Earth and another object, whereas I believe that the initial post was referring to the gravitational force between any two objects in space time.

Newtons law of gravitation assumes that there is a force between any two objects in space which attract them to each other and that this force is inversely proportional to the square of the distance between the two objects, where as it is directly proportional to the multiple of the mass of two objects.

The constant (9.8 m/s^2) is the gravitational acceleration which is a constant for earth ( assuming newtons gravitational law is correct) . But this does not in any way imply that the gravitational force between the earth and any other object is constant . In fact it never is , since its dependant on the mass of the other object and the displacement between the earth and that object.

I think in modern physics, a somewhat different proposition has been forwarded which is attempting to explain gravitational attraction. This proposition suggests that massive objects ( i.e. any object with a mass ) warps the space time around it, and therefore it gives rise to an illusion of one object attracting the other , where as there is no real force between the two objects called gravitational attraction.

For example, if we take a black hole singularity, the mass at the center of the blackhole is infinite, and this will bend the space time around the black hole in such a manner that space-time will collapse in on the blackhole giving the illusion that objects that get close to the black hole are sucked inside, whereas what really happens is that the space time for those objects is warped in a manner where it appears to collapse in on the blackhole RELATIVE to a distant observer who is far enough to not have his/her space time significantly bent by the black hole. Therefore , the gravitational pull between two objects according to this model, is observer dependant, and is the relative difference between the spacetime warp caused by the more massive object , on the spacetime adjacent to the smaller object, and that of the observer

aha ! this is what he was talking about. i've got it totaly wrong in my first glance . my knowledge of physics is not that great to discuss something like this, hence i take my comments back. and thanks Mojo for clarifying it.

 

[Mojo]

aha ! this is what he was talking about. i've got it totaly wrong in my first glance . my knowledge of physics is not that great to discuss something like this, hence i take my comments back. and thanks Mojo for clarifying it.

To be honest, I just told you about something I have read, and I dont fully understand it at all. My knowledge of physics is not that great either, but the funny thing is, i think the less physics you know, the more you can think out of the box, because your thinking is then not bound by preconcieved notions.

And please dont take your comments back, since I think its great if every one just openly discuss this. After all, if physics cannot explain natural phenomena in a way that an average layperson like us can understand, what is the point ?

 

[ogsamoda]

What I think is that we can't say that Newton's theories or Einstein's theories are whole truth. What they did was to make a story(theory) to explain a incident that they observed.. As long as those theories can explain our observations scientists will use them...But as the world develops some day there will be new observations which cannot be explained by the remaining theories...then the scientists will make a new story(theory) to explain them. For example... movements of small particles could not be explained by Newtonian physics and scientists introduced Quantum physics to describe them. The history of science is full of these theories....All of them were correct at their time..... If you did Chemistry for A/Ls you know that there was a concept call plum pudding to describe the atoms....We all know how ridiculous this is but those days this was considered the truth because it was sufficient enough to describe the observations of chemists, ........ There are tons of examples like this....I don't know much stories on medicine since I'm a maths guy....

Knowledge is relative to time...Says Prof. Nalin De Silva.... We can only say that this theory was correct in it's days....We cannot say any theory will be correct forever......

So what we should do is to find out whether these theories are sufficient enough to explain our observations, if not introduce another theory without checking whether these theories are correct or not......Because Theories are just stories to explain the behavior of universe....It's not correct that things happen according to the theories....But Theories are introduced to explain the observations of man....

 

[djHiran]

I think the issue here is that every one who has commented on this thread so far is assuming that the gravitational force referred to in the initial post is the gravitational force between Earth and another object, whereas I believe that the initial post was referring to the gravitational force between any two objects in space time.

Yes that exactly is friend, it is just R girl's post led to me describe based on Earth's gravitational field. Thats just for explanatory purpose.

The constant (9.8 m/s^2) is the gravitational acceleration which is a constant for earth ( assuming newtons gravitational law is correct) . But this does not in any way imply that the gravitational force between the earth and any other object is constant . In fact it never is , since its dependant on the mass of the other object and the displacement between the earth and that object.

Yest but what I was trying to say that G here is not a prime constant. One can see this even by analyzing dimensions.

I think in modern physics, a somewhat different proposition has been forwarded which is attempting to explain gravitational attraction. This proposition suggests that massive objects ( i.e. any object with a mass ) warps the space time around it, and therefore it gives rise to an illusion of one object attracting the other , where as there is no real force between the two objects called gravitational attraction.

That modern idea is based on Special Theory of Relativity. But I believe it is totally or at most incorrect. If you are ready to think open minded, I can show some points that disprove Special Theory of Relativity.

 

[Sherlock1950]

The Bigger / heavier objects must have far more gravitational force thn smaller objects...

How otherwise can you explain a black hole ??

 

[madurax86]

Well... 1st of al let me start by sayin dat i suck at phy

n r u sayin dat gravity is directly proportional to d weight of a body...? hmmm znt it a constant 4 all d bodies... Dsnt d gravitatinal acceleration remain to b 9.81 for all d bodies on erth regardles of its weight...

Btw js ignore dz if am tokin compltly smthng difrnt cuz i comntd on wat i saw in d title only... Hehe.....

That only works when you take mg as the only force(generated by gravity)
it changes when you think of 3 planets and about the interference that one planet gets from other 2
f=mg is just one case

 

[senira]

ammo i dnt kno much abt science

 

[djHiran]

The Bigger / heavier objects must have far more gravitational force thn smaller objects...

How otherwise can you explain a black hole ??

You made a good point.
We come to the conclusion that a black hole is heavier by observing its gravitational force and then again applying the Newtonian equations that we 'think' to be true. Dude, can you prove that result is true by actually measuring the mass of that particular black hole?

That is the crisis

 

[prasadana2]

i cant understand any thing.. i did commerce..

 

[OptiplexFx]

Has it ever been proved that gravity is proportional to mass?

No I don’t think so. AFAIK no one still knows how exactly gravity works. The problem lies between connecting the concept of gravity which is relatively well explained in the theory of large things or what we normally call the theory of General relativity and the concept of mass that is explained in theory of small things what we call Quantum mechanics.

In the smallest of scales the particle connected to mass is called a Higgs boson (this is a concept in advanced particle physics which I have no idea) and the theoretical particle connected to gravity is called a mass less particle called graviton. I don’t know how these two connects or if there a connection at all. But according to many scientists figuring out the graviton is the key to figuring out gravity and everything else.

I am interested in learning about this stuff , but when I get in to deep concepts like Sting theory and M theory etc.. which are supposed to link ideas of quantum mechanics and general relativity my brain just overloads, and it all becomes a blur .

 

[||~R_girl~||]

That only works when you take mg as the only force(generated by gravity)
it changes when you think of 3 planets and about the interference that one planet gets from other 2
f=mg is just one case

ive never gone further dan f=mg. lol
so ma knwldge here is very narrow!!

 

[smallvilleclerk50]

sounds interesting, carry on broz, im listening

 

[madurax86]

ive never gone further dan f=mg. lol
so ma knwldge here is very narrow!!

mg doesnt stay a constant either its accurate at to about 200m from sea level after that it's change has to be taken in to account
eve thought it is not proportional to mass may be its proportional to something that mass is proportional to ... dont know for sure