# Could the gravity of a object be directly related to the density

1. Nov 4, 2009

### millman

my son asked me a question that i can not find an answer too and i hope you can all help me :

could the gravity of a object be directly related to the density and speed of the object as it passes through the higs feild ?

2. Nov 4, 2009

### Nickelodeon

Re: gravity

I would have thought that gravity is directly related to the density of an object.
As for the speed of an object, well some say the faster an object is moving the more energy it has which they then equate to an increase in mass and hence it will exert more gravity. I'm not a great fan of that idea. If the object is accelerating then that might be a different case, but just simply floating along with a uniform speed I can't see it.

3. Nov 4, 2009

### TurtleMeister

Re: gravity

According to everything I've studied, the gravitational force produced by an object is directly proportional to it's mass. But I will admit that I have not studied GR, which may have more to say.

4. Nov 4, 2009

### magpies

Re: gravity

Density<-- Change this to Mass I guess... And imo and probably only mine density/mass is just how much space it displaces.

Last edited: Nov 4, 2009
5. Nov 4, 2009

### TurtleMeister

Re: gravity

I think that density is the wrong word to use here. Just changing an objects density will not change the force of it's gravitational field. If I have two objects with the same mass but different densities then they will both still produce the same gravitational force, as long as the distance does not fall below the radius of the larger object.

6. Nov 4, 2009

### Staff: Mentor

Re: gravity

Right - what density affects is only how close you can get to the [center of] the object. If we're talking about the earth orbiting the sun, the density of the sun is completely irrelevant. Someone asked the question just yesterday: If you replace the sun with a black hole of equal mass, what happen's to earths orbit? Answer: Nothing.

7. Nov 4, 2009

### Staff: Mentor

Re: gravity

Well, except for the part where things get dark and start to get cold about 8 minutes later...

8. Nov 4, 2009

### millman

Re: gravity

hahahah at least thats one thing we dont have to worry about

the one question that this has raised with my self is , as we currently stand einsteins theories fail at 2 points one being the event horrizon of a black hole the other the big bang.
what if gravity instead of being one of the 4 forces is in fact a result of dense matter passing through the higs feild the denser the matter the greater the affect the greater the mass?

9. Nov 4, 2009

### Nabeshin

Re: gravity

General relativity actually doesn't fail at the event horizon of a black hole. This is a pretty common misconception. Where GR fails is the singularity of a black hole, and similarly, any proposed singularity at the big bang.

10. Nov 4, 2009

### gutti

Re: gravity

Well many people have studied this, physicists and mathematicians and its shown that gravity is directly proportional to the mass, and density of an object doesn't affect it.
Stated in terms of newtons theory of gravitation, which isn't a totally accurate description of whats going on but close enough for this.
Gravitational force exerted depends on the mass of the object attracting, the mass of the object being attracted and the distance between them.