A rock seems unlikely to be conscious in any real way. Something as complex as a star, however...maybe all of the humans worshipping the sun throughout many thousands of years were onto something after all.
A rock the size of a human head (or, say, a container of seawater) has just as many electrons, protons, neutrons, photons, and other particles going about their business and doing their little dance, following the same equations of motion as our brains do. They're certainly doing it in different ways, but if you're just looking for complexity, there's no shortage of it. The rock might lack some macroscopic structural change over human timescales, but definitely not the seawater.
I think if you take the perspective that the human brain is conscious but not a brain-sized container of seawater, you need to then look carefully for distinctions between them. "Information processing" or "response to environment" is probably not good enough; the seawater is actually doing all of those, with a unique reaction to any possible input, so you'd have to be more specific.
Probably the only recourse you could look for to make the distinction is to say the brain embeds particular mathematical patterns that the seawater doesn't, such as a compact, stored representation of its environment (or its history of inputs), or a future-looking planning algorithm, or both. I personally take this view (I think of qualia, like "the appearance of a red apple", is just precisely what it feels like to read from the buffered [R,G,B] memory array in my head, filtered through image-recognition networks).
But then if you put your hopes on consciousness originating from those mathematical functions, you have to admit that any analogous expression of those functions in other systems would also be conscious, such as animals and robots.
And worse, once you start thinking about math and how flexible it is, how information is in the eye of the beholder and almost any system that follows certain rules can embed almost any mathematical computation, just like illegible scratches to me are information-rich writing to you, you might have to circle back and that there could be very analogous computations going on inside rocks and seawater. And that brings us back full-circle.
Is a star particularly complex, though? Is there much going on besides a lot of thermonuclear fusion? (Disclaimer: I don't know much about stars or astrophysics, so this question is coming from a place of ignorance.)
I think if you take the perspective that the human brain is conscious but not a brain-sized container of seawater, you need to then look carefully for distinctions between them. "Information processing" or "response to environment" is probably not good enough; the seawater is actually doing all of those, with a unique reaction to any possible input, so you'd have to be more specific.
Probably the only recourse you could look for to make the distinction is to say the brain embeds particular mathematical patterns that the seawater doesn't, such as a compact, stored representation of its environment (or its history of inputs), or a future-looking planning algorithm, or both. I personally take this view (I think of qualia, like "the appearance of a red apple", is just precisely what it feels like to read from the buffered [R,G,B] memory array in my head, filtered through image-recognition networks).
But then if you put your hopes on consciousness originating from those mathematical functions, you have to admit that any analogous expression of those functions in other systems would also be conscious, such as animals and robots.
And worse, once you start thinking about math and how flexible it is, how information is in the eye of the beholder and almost any system that follows certain rules can embed almost any mathematical computation, just like illegible scratches to me are information-rich writing to you, you might have to circle back and that there could be very analogous computations going on inside rocks and seawater. And that brings us back full-circle.