Theoretically speaking, can a rocky planet of the size of Jupiter exist? If not, why not?

It is necessary to understand the structure of planets underneath their atmospheres. It is common to state the diameter of Jupiter in relation to its atmospheric diameter instead of the liquid metallic hydrogen surface. This is because we did not understand the composition of gas giants in the past and the definition remained with us to this day.

This is similar to stating that Earth is the diameter of its mesosphere instead of measuring the diameter of Earth at the continental/oceanic surface. While it is true that the atmospheres are less dense than actual surfaces, the gravity at the liquid metallic surface of Jupiter is still 2.5 times that on the surface of Earth. The greater the gravity, of course the larger and denser bone structure needs to be to carry the weight and movements of the organism.

One would need to seek the estimations of a professional biologist regarding the most massive organism which could potentially exist but clearly the answer is not infinite nor is the sky the limit. Could organisms evolve under gravitational conditions 2.5 x Earth? Yes if a multitude of required conditions also exist, but those creatures would not be exactly like those on Earth if that is your question.

The hypothetical designs of such creatures would again be best left to an experienced exobiologist. Jupiter has been a major influence upon the trajectory of asteroids and comets within our Solar System. Such planets not only attract more of these but also are responsible for sending them into trajectories where they leave our Solar System.

Undeniably, planets with stronger gravitational systems would attract more bolides. Avoiding these long enough for life forms to arise and evolve is partially a matter of random chance. It must be noted that the cause of the Late Heavy Bombardment is still not known.

Therefore, the size of the planet is not the only consideration when it comes down to bolide impact causes. It is essential that the planet have not just an atmosphere (which it would have given its gravity) but an iron core which would create a solar radiation deflecting magnetosphere. Harmful radiation would need to be kept from reaching the planetary surface as much as bolide impacts for life to succeed.

The problem with such a large atmosphere is that it creates pressures which alter the normal geological structures of the planet. Therefore, the surface (below the atmosphere) would most likely not be a solid but instead be a toxic liquid which would be the real cause of not supporting life forms.

Solid rock is 10,000s of times denser than gaseous elements, the planet could possibly have a mass greater than a brown dwarf - a failed star. It's mass could be that of a red dwarf star. But a mass that small may unlikely be enough for pressures at the core to convert carbon into other elements, like silicon.

But the core would still be very energetic. Extreme geology. Magma chambers incredibly long, The heat pressure causing those magma chambers would be amazingly great.

Unknown if it would ever reach the crust. I think no life could evolve on a planet that massive. Because not only would life have the gravity, but so would the trees, food, water, etc. The gravity might not even allow rain clouds to become large enough for plenty of rain.

And since the planet is rock, which is far denser than gases, the gravity of a planet that massive would be much greater than a red dwarf that massive. So rain clouds might not even form. And water pressures in the ocean would be too much for marine life to evolve.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.