I once watched a tv program on the possibility of alien life. The program intrigued me in the possibility that life as we know it might not be as limited. Some possibilities that entertained me are: 1) alien life might not need DNA to transfer traits to the next generations. 2) They might be gas, or a smell( to us). 3) might take advantage of the "strong force", and live on the surface of a neutron star 4) they might not be detachable by our eyes, becuase of "longer wavelength"( don t know).. blah blah.. etc... Any comments? Are there necessary constraits to life? Are there some criterion for life? What are the possibilities? and limitations?