If earths rotation stoped, the moon would be released.

[ttmark]

Y
you call it circular reasoning..

The circular reasoning is because we are using the gravity constant between two equal in mass objects which was measured on Earth to then claim the mass of planetary objects outside of Earth. One must be very careful in doing this because the motion of the bodies within gravitational field must be considered about it's own inertial frame for Newtons laws of motion to work.

 

[DaveC426913]

As you can see in my post, "As you are aware many things can make you experience a different gravity constant". Notice gravity is lower case and referencing an experience felt by a person. This is clearly written referring to a point of reference of someone on Earth.

You have trieds to define the phrase "gravitational constant" several times, incorrectly. Backpedal all you want.

Your personal attacks are unneeded and against forum rules and will be ignored. Please read "Guidelines on Langauge and Attitude:"

I have made no personal attacks; I have pointed out errors. Forum rules do not cover being wrong.


All this aside, your original comment still makes no sense.

...that mass is proportional to gravity in some cases...

In what cases is it not?

 

[narrator]

The gravitational constant is 6.673e_11 m^3/kgs^2(signified by G) and this is the same for all masses.

I had always wondered what that value is and how constant it is. Many thanks. :)

 

[narrator]

that mass is proportional to gravity in some cases

In what cases is it not?

Even as a layman I can see this. As far as I know, mass is always proportional to gravity. Other factors can change the acceleration, but that doesn't affect the proportionality of mass to gravity. We experience a different gravity on the moon because the moon is a different volume of mass and follows the proportion exactly.

As an interesting contradiction though, I was surprised to read about the http://en.wikipedia.org/wiki/Pioneer_anomaly" . Freakish, especially since even cosmology was proven not to be the missing link!

 

[Borek]

As an interesting contradiction though, I was surprised to read about the http://en.wikipedia.org/wiki/Pioneer_anomaly" . Freakish, especially since even cosmology was proven not to be the missing link!

Check out this thread: Pioneer anomaly solved - no need for cosmology.

 

[JaredJames]

ttmark seems to be confusing the force due to gravity on its own and the net force with all other factors involved.

Aside from that note, I don't see what the point of his posts are. Perhaps an explanation ttmark?

 

[narrator]

Check out this thread: Pioneer anomaly solved - no need for cosmology.

A very elegant solution to the puzzle :)

 

[ttmark]

ttmark seems to be confusing the force due to gravity on its own and the net force with all other factors involved.

Aside from that note, I don't see what the point of his posts are. Perhaps an explanation ttmark?

I have been away harvesting wheat all weekend, sorry guys... I do not remember if there is any point, but I do not have time to argue back and forth with the poster who claims I am confused with G or g. If there is any point it is that just because gravity is proportional to mass within our inertial frame of reference does not mean that we know that gravity is caused by mass. So when one is considering planetary objects outside our inertial frame of reference you have to be careful applying the gravity constant because that constant was measured with two objects of equal mass on Earth. So then we go out and assign a mass to every object we see in the sky with this constant, maybe right, never understanding what creates gravity to begin with.

 

[narrator]

So then we go out and assign a mass to every object we see in the sky with this constant, maybe right, never understanding what creates gravity to begin with.

It's not that simple ttmark. Science isn't science without the process of falsification. You don't just apply a value to something then move on. You test to make sure that applying that value actually matches with other evidence. If the constant isn't constant, then observations would have shown that long ago. Orbits alone would disprove it.

The proportionality of gravity to mass has been proven over and over. Other contributions to inertia, force or whatever are also proven. And all of it through science's most rigorous test - falsification.

 

[ttmark]

It's not that simple ttmark. Science isn't science without the process of falsification. You don't just apply a value to something then move on. You test to make sure that applying that value actually matches with other evidence. If the constant isn't constant, then observations would have shown that long ago. Orbits alone would disprove it.

The proportionality of gravity to mass has been proven over and over. Other contributions to inertia, force or whatever are also proven. And all of it through science's most rigorous test - falsification.

My understanding is we took this constant we measured on Earth and used it to establish the mass of the sun based upon Earths orbital period and distance. From there we used this mass of the sun to branch out to the other planets based upon their orbits. Changing the constant would not affect any orbits at all, merely the mass that we claim each is. Is there some over method that can prove this? As I see it right now we are just solving for whatever mass is needed to fit the orbit of the object in question.

 

[narrator]

As I said, it's not that simple. It you were dealing with just one variable, and only ever used that one equation for one thing, then your argument could have merit. But the geometry of space has many equations (including complex calculus) with so many variables that a mountain of anomalies would have proven your case a long time ago. Except perhaps in exotic conditions (black holes, pre-plank time, and quantum physics), the relationship between mass and gravity is proven beyond doubt.

 

[DaveC426913]

My understanding is we took this constant we measured on Earth and used it to establish the mass of the sun based upon Earths orbital period and distance. From there we used this mass of the sun to branch out to the other planets based upon their orbits. Changing the constant would not affect any orbits at all, merely the mass that we claim each is. Is there some over method that can prove this? As I see it right now we are just solving for whatever mass is needed to fit the orbit of the object in question.

There is what is known as a preponderance of evidence. We do not simply take maeasurments in one place and assume it holds everywhere. Our understanding of the cosmos is a collection of many, many interdependent pieces. If our numbers are wrong, it will show up in many places, both in our measurements of the cosmos and in our formulae and theories.