So where are they? The speed of light seems to be another universal constant. They are mostly too far away to get here, or even to communicate their existence.
Too far away for carbon based life, but if by some bizarre happenstance there was silicon based life somewhere, chances are good that it would be much more long-lived than carbon based life forms. Fifty years is a long time for us, but fifty thousand years might be the blink of an eye for silicon based life.
