Life is incredibly hard to arbitrate. Humans have a basic understanding of life, and we define life using different characteristics. This works well on a scale relative to human life on earth, but the simple fact remains that we have no idea what the term "life" encompasses. We only have our small little sample dish here on earth to draw from. Lets take a look at viruses. They are not classified as alive, but why not? Cells require sources of energy to survive. As do viruses. Viruses feed off of the lives of cells to reproduce and evolve. Viruses grow at an alarming rate, and sometimes nothing can stop them until the consume everything they can. Sound familiar? Humans are much the same, except we thrive off of non-living or once-alive parts of matter instead of living forms. Humans and viruses are polar opposites; but in a sense, we are very much the same. My point is, we have no place to classify life. Viruses are alive.
We can't accurately describe what a planet is either.... Look once we stop using our most brilliant minds to make consumer goods and invent and research things for war and profit then we can accurately start labeling the things around us. We just have our energy focused on stupid trivial things right now, we will learn.
Viruses don't seek out the energy they are just a chemical reaction. You see by your definition stars systems and galaxies need to consume energy too and are thus alive. But higher life forms will actually seek out energy actively. Some would argue that Tue search for energy is a reaction to external stimuli. If that's the case then "life" becomes subjective because the line can be drawn anywhere.
As yuri said, you can pretty much draw the line where ever you want. People do it all the time.. If you're going off of the closest scientific "definition", viruses are not alive. They meet the majority of requirements for life, but miss out on the ability to metabolize and cannot reproduce without a cell to infect. It's like the planet definition SniperKitty was talking bout. There technically is a definition for a planet, it has to meet 3 requirements. Orbit around a star, enough mass to be round(ish), and have cleared all the objects in it's orbit. Unfortunately, Pluto has not cleared it's orbit and is considered a dwarf planet. But myself and many others still look at Pluto like a planet even though it's not. If Pluto was allowed to be a planet, we'd have to add a shit load more than just it. So no matter where the line is drawn in the official definition, people will always sway to one side or the other. PS - Saying the humans and viruses are very much the same is dumb, but I don't blame you, I blame The Matrix..
This thread reminded me of one of my favorite songs. The Virus of Life by Slipknot Most people are Knot haters, But if you read the lyrics its brilliant
Prion - Wikipedia, the free encyclopedia Some say these guys are alive. Kind of fall into the same catagory as viruses