Is density of a material affected by gravity? If so

[liubare]

I was pondering this while I was staring at a salad dressing bottle at home (an oily dressing that doesn't stay mixed when untouched for a period of time...), how well could you mix (shake up) a bottle with different oils in a micro-gravity environment, if at all?

Moreover, my actual question is about the planets in our solar system. I noticed after (beyond) Mars it is essentially all gas planets (aside from the various belts of asteroids), could this be caused by the similar material separation I observe with a salad dressing?
The 'heavier' materials, while the planets were forming, would 'fall to the bottom' (closer to the sun) and the lighter matter would be further out?
If my idea is correct, then wouldn't that make Saturn 'lighter' than Jupiter; Uranus 'lighter' than Saturn? etc, etc.

I apologize if this has been asked already, I've had no luck finding it in the search bar...

 

[mathman]

http://en.wikipedia.org/wiki/Formation_and_evolution_of_the_Solar_System#Formation_of_planets

Temperature seems to have been the main reason the inner planets are rocky and the outer planets are gas giants.

 

[DavidKutzler]

All matter has mass and occupies space (i.e., has volume). Density is defined as mass over volume (D = m/V). Mass is independent of gravity, unlike weight, which is the force exerted by mass due to the acceleration of gravity (F = ma). Volume is dependent on pressure, i.e., the same mass will have a greater density if it is compressed to a smaller volume because it makes the denominator of the density equation smaller. Gravity is a force that can compress matter, so the answer to your original question is YES, gravity does affect density. The answer to your real question is more complicated. Many "hot Jupiters" have been identified orbiting stars, that is, gas giants in very close orbits to their stars. Why our solar system sorted itself out the way it did is likely not clearly understood, but I doubt that it has anything to do with density.

 

[D H]

Moreover, my actual question is about the planets in our solar system. I noticed after (beyond) Mars it is essentially all gas planets (aside from the various belts of asteroids), could this be caused by the similar material separation I observe with a salad dressing?
The 'heavier' materials, while the planets were forming, would 'fall to the bottom' (closer to the sun) and the lighter matter would be further out?

That's not how planets form. As mathman noted, it was temperature driven. Gas giants need low temperatures to form. They couldn't have formed close into infant sun. Terrestrial planets could form there, but they wouldn't have been able to get massive enough to hold the ices, volatiles, and gases that form much of the giant planets. So where did that lighter stuff go? Simple. When the infant sun ignited as a star, the radiation pressure blew all the incorporated dust and gas out of the solar system.

The answer to your real question is more complicated. Many "hot Jupiters" have been identified orbiting stars, that is, gas giants in very close orbits to their stars.

The current thinking is that those hot Jupiters formed far from their parent stars but migrated inwards during planetary formation. Astrophysicists are almost certain that they couldn't have formed close in; it doesn't make sense. For more info, google "type II migration".

 

[pmacias]

Yes, density of a material can be affected by gravity. In fact, density is defined as the mass of a substance per unit volume, and mass is directly related to gravity. The more mass a substance has, the stronger its gravitational pull will be. This is why objects with a higher density, such as a rock, will feel heavier than objects with a lower density, such as a balloon, due to the difference in gravitational pull.

In terms of mixing oils in a micro-gravity environment, it would be difficult to achieve a thorough mixing as there is no force of gravity to help distribute the different densities of the oils. However, other forces such as surface tension and viscosity may still play a role in the mixing process.

As for the formation of gas planets in our solar system, your analogy to salad dressing is not quite accurate. The formation of planets is a complex process that involves many factors, including the materials present, temperature, and pressure. The gas giants in our solar system, such as Jupiter and Saturn, are thought to have formed from a large amount of gas and dust, while the inner rocky planets formed from heavier materials that were able to withstand higher temperatures and pressures closer to the sun.

In conclusion, while density can be affected by gravity, the formation of planets is a much more complicated process that involves many other factors besides just density.