What Pulls the Sun? Understanding Gravitational Pull and Mass Effect

[michelrochette]

I can "understand" the gravitational pull of the sun on the Earth and the Earth mass effect toward the moon, but what pull the sun?

a neophyte.

 

[Astronuc]

The sun is part of the Milky Way Galaxy, a large collection of stars. The Milky Galaxy is a spiral galaxy, although apparently recent observations indicate it is a barred sprial galaxy. It's neighor, the Andromeda Galaxy (M31, NGC 224), which we can see, is a spiral galaxy.

http://en.wikipedia.org/wiki/Milky_Way
http://en.wikipedia.org/wiki/Barred_spiral_galaxy

http://seds.org/messier/more/mw.html
http://www.windows.ucar.edu/tour/link=/the_universe/Milkyway.html&edu=mid

http://en.wikipedia.org/wiki/Andromeda_Galaxy

http://www.windows.ucar.edu/tour/link=/the_universe/Spirals.html

 

[-RA-]

I can "understand" the gravitational pull of the sun on the Earth and the Earth mass effect toward the moon, but what pull the sun?

I think that the only other force that really effects the path of sun (and thus the rest of the solar system with it) is the gravity from the assumed 'super massive black hole' at the centre.

I would presume that gravity works completely differently on a galactic scale, as you don't see any other galaxy shaped objects on smaller scales. I think I'm correct in saying that galaxy formation is still not fully explained by gravity alone yet?

 

[HallsofIvy]

Also, obviously, the Earth pulls on the sun just as hard as the sun pulls on the earth!

 

[SpaceTiger]

I would presume that gravity works completely differently on a galactic scale, as you don't see any other galaxy shaped objects on smaller scales. I think I'm correct in saying that galaxy formation is still not fully explained by gravity alone yet?

Galaxy formation will never be fully explained by gravity alone, it involves both gas dynamics and magnetic fields.

 

[michelrochette]

Isaac Newton found out that the strength of the pull of gravity weakens the farther you get away from an object, in proportion to 1/(r*r), where r is the distance you are away from the center. The strength of the gravitational pull is also proportional to the mass of the object.

The nearest star, Proxima Centauri, is 4.3 light-years away, so stars do not have any pull on each other. i assume that the mass of a black hole is the only thing that can pull the sun.

Am I right?

 

[Garth]

Isaac Newton found out that the strength of the pull of gravity weakens the farther you get away from an object, in proportion to 1/(r*r), where r is the distance you are away from the center. The strength of the gravitational pull is also proportional to the mass of the object.

The nearest star, Proxima Centauri, is 4.3 light-years away, so stars do not have any pull on each other. i assume that the mass of a black hole is the only thing that can pull the sun.

Am I right?

Welcome to these Forums michelrochette and keep asking the questions!

In this case you are not right, although you did give the answer yourself, stars do have a gravitational attraction to each other, however, because as you correctly say the acceleration, or 'pull', is proportional to 1/r² the attraction of the solar system towards an individual, even the nearest, star is incredibly weak.

However there are about 2 x10¹¹ stars in our galaxy and their combined pull is sufficient to keep our solar system in orbit around the galactic centre. Our orbital velocity is about 0.1% the speed of light and it takes the solar system ~ 'quarter' of a billion (10⁹) years to make one orbital revolution.

Garth

 

[michelrochette]

@Garth
Thank you for your clear answer!