No ET! Ever?

[Anomalocaris]

Our ability to detext e.t. Life is limited by the paradigm w use. We look for stars with planets in a comfort zone suitable for carbon-based life forms. Life forms based on other elements such as sulfur are outside our circle of awaremess, so we haven't developed a paradigm that would allow us to detest such life.

Except through sheer baseless fantasy, we have not yet been able to dream up, even at high level, how life can be possible without some chemical basis that would allow the formation of a very large variety of very complex, interacting molecules, and some medium that dissolve constituents of these molecules to transport them to a central location, without also instantly destroying these molecules once they form.

We may not yet know much of all there is to know about physics, but we think we have a good working knowledge of chemistry.  Chemistry say there is strong reason to suppose the rather unique chemicals and physical properties of water and carbon make these two by far the best candidates to fulfill the above stated conditions.

So it's not just because earth life is water and carbon based. It's no other chemical can come close to providing a similarly board basis for metabolism and genetic inheritance.