With reference to “Where are the aliens?” (December 22), one of the greatest scientific mysteries is, are we alone in the universe? The sheer number of planets increases the probability that Earth-like planets exist. Many astronomers estimate that we’ll find a life-bearing planet within 25-30 years if we know what to look for. Life could be different from what we are familiar with on Earth. Until we have the technology to travel close to the speed of light, we may never know. There may well be life — and intelligent life — beyond our solar system, but how could we