Is it possible for space craft to cover the enormous distances of outer space?
For technically superior civilizations it certainly would. The Extraterrestrials might even be here already - only - they do not make themselves known.
The Italian Nuclear Physicist Enrico Fermi had asked himself the same question, although with a slightly different slant. In Chicago in 1942 he actuated the first controlled nuclear chain reaction and later joined the "Manhattan Project". Under this assumed name American scientists were developing the Atom bomb in a research laboratory in Los Alamos. Ferni pondered about one of the most basic questions of mankind: Are we the only technologically developed civilization in this Universe?
Where are the Extraterrestrials?
During the search for an answer to this question he came to the following assumption: If there were but only one race in the Milky Way who was able to do interstellar travels, then they would be able to cover the whole Galaxy within 20 - 40 Million years. Doing this, they could go to all inhabited planets and colonize them (this would happen with below speed of light). Therefore it is obvious that large numbers of civilizations are present in our galactic neighbourhoods. However, unto this day there is no sign of their existence.
So, where are they?
We have several answers to this: Either there are civilizations with technical knowledge who are not more advanced than us and are not able to space travel. Or, they could have colonized neighbouring worlds (having skipped the earth), or, there are none and we are the only civilization with an advanced technology in the Milky Way. The "Fermi-Paradox", which made scientific history: The idea that there are many technologically advanced civilizations in our Universe is a paradox since our observations seem to confirm the opposite and this implies that either our understanding or our observations are faulty and incomplete. ...
