[Prof_Sai]

The following is a strange argument, with a strange conclusion, so I'll just jump into it:

1) All life on Earth expands and adapts to fill any available nitch. This is a central part of what life is; constant reproduction and evolution is why life forms continue to thrive while any non living structure decays.

2) If humans learned how to escape their solar system, the same rules of expansion would apply across the galaxy. It might take less then a million years for humans to colonize every star in the Milky Way.

3) But the universe is 20 billion years old! If humans could spread across the galaxy that fast, why hasn't some alien race already done this? With so many suns existing for so long, is it realistic to think that our ordinary planet has produced the first intelligent life form?

4) So where are the aliens? Something must be stopping all alien civilizations from expanding into space. Maybe there is a secret barrier to space travel. Maybe all intelligence ultimately destroys itself.

Or maybe they start playing with physics that has a small chance of creating a black hole.