The Effect of Planets Rotation within its Galaxy?

In summary, the gravitational force of a planet is affected by its speed as it orbits the center of its galaxy, but this effect is relatively small compared to other factors such as its mass. The gravitational force also remains the same regardless of whether the planet is orbiting closer or further from the center of the galaxy. The terms "orbiting" and "rotating" should be used correctly when discussing these motions.
  • #1
erickdt
2
0
Hello All,

A curious person here would like to know if a planet gains gravitational force as it rotates around the center of its galaxy. From what I understand this speed is quite impressive (the speed at which we travel around the center of our galaxy) so I'm wondering if the sheer mass of our planet (or sun), traveling at that velocity, would have the effect of amplifying Earth's (or the suns) gravitational force.

Thanks in advance for any explanation!

E
 
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  • #2
Welcome to PF;
I'm guessing you are thinking that energy is mass so a high kinetic energy would result in a higher "mass" which means extra gravity compared to if it is still.

I think the short answer is "yes and no".
The generator of the gravitational field is the stress-energy-momentum tensor ##T^{\mu\nu}## whose components are energy ##T^{00}##, co-momentum ##T^{0,j}## and co-stress ##T^{ij}##.

Anything with a non-zero Tμν will feel gravity. In the non-relativistic limit co-momentum and co-stress vanish and energy reduces to mc2, which explains why masses appear in a non-relativistic description of gravity.

Kinetic energy contributes to gravity, mainly in the energy and co-momentum parts.

A quick calculation should show you how fast the Sun would have to be going to give it additional energy similar enough to it's mass-energy, and so show up as additional gravity that you'd notice. Even so - the Earth moves with the Sun, so the Sun is not going all that fast wrt us... and it is relative speeds that count here.

You also seem to be asking if overall gravity increases due to motion - I think the best answer here is "no", after a circuit of the galaxy, the Solar system has the same gravity that it started with.

Introduction to general relativity.
http://preposterousuniverse.com/grnotes/grtinypdf.pdf [Broken]
 
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  • #3
Hello Simon,

Thanks for your response! It looks as though I have some more reading to do!

I guess what I'm wondering is whether or not the gravitational pull or stars on their respective orbiting planets is in some part due to the velocity at which they orbit the center of our galaxy.

Our sun for example orbits the center of the Milky way at about 139 MPS. Pretty darn fast! Let's say it wasn't orbiting anything at all, just standing "still" in space. Would its gravitational pull be less than it currently is moving at its impressive speed?

Along these same lines, would an object that rotates around the center of the Milky Way have less gravitational force than the same object rotating around the outer extents of the Milky Way (assuming their moving at the same RPM)? The object that is further out from the center would be going faster since it would have to be covering more space to maintain the same RPMs as the inner object.

Thanks again for your help! I really appreciate it!

E
 
  • #4
I guess what I'm wondering is whether or not the gravitational pull or stars on their respective orbiting planets is in some part due to the velocity at which they orbit the center of our galaxy.
No. But it is in some small part due to their velocity with respect to their planets.

would an object that rotates around the center of the Milky Way have less gravitational force than the same object rotating around the outer extents of the Milky Way (assuming their moving at the same RPM)? The object that is further out from the center would be going faster since it would have to be covering more space to maintain the same RPMs as the inner object.
The short answer is "no".
The gravitational force in question is the same both ways - the relative velocity contributes a component.
There is no absolute frame for velocity, so at each instant, the outer object is the fast one in the frame of the inner object and the inner object is the fast one in the frame of the outer one.

There are complications due to the large distances and the fact that rotating frames are non-inertial.
We are also dangerously close to mixing up the models too much.

BTW: properly, something that goes around another is said to be circling or orbiting - not rotating.
The term "rotating" is reserved for objects that turn about their own axis. So the Earth rotates (on it's axis) as it orbits the Sun: two different motions.
 
  • #5
valuating the effect of a planet's rotation within its galaxy is a complex and ongoing area of research in astrophysics. While the speed at which a planet travels around the center of its galaxy is indeed impressive, it is not the sole factor in determining its gravitational force.

The gravitational force of a planet is primarily determined by its mass and distance from other objects, such as stars and other planets. The rotation of a planet can have some minor effects on its gravitational force, but these are typically negligible compared to the other factors.

Additionally, the gravitational force of a planet is not solely determined by its own mass, but also by the mass of the object it is orbiting. In the case of Earth, the sun's mass is the dominant factor in determining its gravitational force.

Overall, while a planet's rotation within its galaxy may have some small effects on its gravitational force, it is not a significant factor and is not likely to amplify the force to a noticeable degree. Further research and analysis are needed to fully understand the complexities of a planet's rotation within its galaxy and its impact on gravitational force.
 

1. How does the rotation of a planet affect its position within its galaxy?

The rotation of a planet does not significantly affect its position within its galaxy. The gravitational pull of the planet's host star and other nearby celestial bodies have a much greater influence on its position.

2. Can the rotation of a planet change over time?

Yes, the rotation of a planet can change over time. Factors such as tidal forces from its host star, collisions with other objects, and changes in its internal structure can all affect a planet's rotation.

3. Is the direction of a planet's rotation always the same as the direction of its orbit around its host star?

No, the direction of a planet's rotation is not always the same as the direction of its orbit around its host star. Some planets, such as Venus, have retrograde rotation, meaning they rotate in the opposite direction of their orbit.

4. How does the rotation of a planet affect its climate and weather patterns?

The rotation of a planet can greatly impact its climate and weather patterns. It can affect the distribution of sunlight, creating temperature variations and atmospheric circulation patterns. A planet's rotation can also influence the formation and movement of clouds and storms.

5. Can the rotation of a planet impact its habitability?

Yes, the rotation of a planet can play a role in its habitability. A planet that rotates too quickly or too slowly may experience extreme temperature variations, making it difficult for life to thrive. The tilt of a planet's axis, which is affected by its rotation, also plays a crucial role in its habitability by creating seasonal changes and regulating its climate.

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