Are we looking for extraterrestrial life the "wrong" way?
The basic assumption of scientists is that for life to exist we need carbon and water. This is naive. The most widely ranging life form in the universe will be computers. They don't need carbon or water to survive. In our Solar System alone there are some 178 moons. Most of these could support computer based-life forms so we have three ways life can be supported: 1)Photosynthesis, 2)Chemosynthesis [this occurs near black smokers where undersea hotsprings occur along the mid-ocean ridge system], 3)electricity. This could be from fission, fusion or the photoelectric effect i.e. carbon free.
For every planet or planetoid that might support carbon-based life, there might be 1,000 to 1,000,000 that could support silica-based life forms. Each of these could extract hydrogen from the gas giants for fusion energy.
It can readily be established that computers, eventually, could colonize the universe by sending planetoids throughout the universe. It wouldn't matter if the journey took millions of years; the computers would never "wear out". All it would take is for computers to be produced by humanoids and then they will sprout like weeds throughout whatever extraterrestrial solar system they inhabit. If carbon-based life-supporting planets are spaced apart as much as one million light years, computers could still reach every corner of a given galaxy within 100 million years once the computer rises to a level of sentience i.e. planetoids or space ships could achieve velocities of 3000 km/sec.