Hot Air Balloons for Artillery spotting

fallsfromtrees wrote:

TN4994 wrote:Any gas is a collection of molecules that are attracted to each other by gravitational pull. These in turn are acted upon by the Earth's gravitational pull. Some more than others.

The gravitational pull between gas molecules is negligible. I think what you were trying to say is that some molecules are heavier than others, which is true, and that buoyancy is related to the displacement differential between a volume of lighter gas and a heavier gas. The same principle is true for a properly shaped chunk of steel. Normally a block of steel will sink in water, but form it into a bowl shape (or boat shape) such that the weight of the water displaced by the shape is greater than the weight of the steel shape, it will float.

There you go, getting Archimedes into the picture. But I take your liquid water and condense the molecules by lowering the temperature thus slowing the descent of the square block of steel. I forget where the experiment was conducted where one metal sank into another metal.
Back to gravitational pull of molucules. It's relative to outside forces. But in normal circumstances anytime we speak of lighter than air, we imply that air has weight. Now, all we have to do is agree on the definition of air.

Fallsfromtrees: I think I see what you're posting about now with buoyancy. Please excuse me, sometimes I can be so dense.

TN4994 wrote:Fallsfromtrees: I think I see what you're posting about now with buoyancy. Please excuse me, sometimes I can be so dense.

You have been warned about the puns. Very shortly I will have to hunt you down and punnish you.

fallsfromtrees wrote:

TN4994 wrote:Fallsfromtrees: I think I see what you're posting about now with buoyancy. Please excuse me, sometimes I can be so dense.

You have been warned about the puns. Very shortly I will have to hunt you down and punnish you.

I think several of us are suffering from punnishment.

fallsfromtrees wrote:

TN4994 wrote:Fallsfromtrees: I think I see what you're posting about now with buoyancy. Please excuse me, sometimes I can be so dense.

You have been warned about the puns. Very shortly I will have to hunt you down and punnish you.

Yah,think I can't take the pressure?
What depths are you willing to go in serving up the puns lament?

Thanks to all the planetary scientists for keeping me right.

TN4994 wrote:And tbere are gaseous giants in the universe withould any solid foundation.

If you mean that there are planets where there is no distinct solid surface, that is true. If you mean there are planets without a rocky core, that is probably not true.

SWM wrote:

TN4994 wrote:And tbere are gaseous giants in the universe withould any solid foundation.

If you mean that there are planets where there is no distinct solid surface, that is true. If you mean there are planets without a rocky core, that is probably not true.

Define rocky.
And isn't our sun a gaseous giant?

TN4994 wrote:

SWM wrote:If you mean that there are planets where there is no distinct solid surface, that is true. If you mean there are planets without a rocky core, that is probably not true.

Define rocky.
And isn't our sun a gaseous giant?

No, our sun is not a gaseous giant. It is a star. There are fundamental differences in the formation of a star and a planet. The brown dwarfs cross the line between star and planet. But our sun is far far larger than a brown dwarf, and is in no way a gaseous planet.

By rocky, I mean a core composed primarily of silicate and metallic materials, in solid form. All planets form initially from rocky components. The only way to have gas collapse into a body without a rocky core is if it is a stellar-sized mass of gas, forming a star. Gas is too hot and diffuse in a proto-planetary system to collapse unless it is gathered in by an existing gravitional field, i.e. the protostar itself or one of the rocky bodies forming around it. Eventually, the remaining gas is swept away by the newborn star once it reaches ignition.

SWM wrote:No, our sun is not a gaseous giant. It is a star. There are fundamental differences in the formation of a star and a planet. The brown dwarfs cross the line between star and planet. But our sun is far far larger than a brown dwarf, and is in no way a gaseous planet.

By rocky, I mean a core composed primarily of silicate and metallic materials, in solid form. All planets form initially from rocky components. The only way to have gas collapse into a body without a rocky core is if it is a stellar-sized mass of gas, forming a star. Gas is too hot and diffuse in a proto-planetary system to collapse unless it is gathered in by an existing gravitional field, i.e. the protostar itself or one of the rocky bodies forming around it. Eventually, the remaining gas is swept away by the newborn star once it reaches ignition.

Thanks for the clarification. I remember being taught that the stars were the only true gas giants, planets like Jupiter were gas laden planets (Pluto was still a planet then), the asteroid belt was either a planet that blew apart or was about to form. Other than Rocky and Bullwinkle making friends with moon-men, that's about it. OK, we did cover the Solar System and space objects like natural satellites, comets, and meteors.