Page "Fermi paradox" Paragraph 14

The Fermi paradox can be asked in two ways.

The first is, " Why are no aliens or their artifacts physically here?

" If interstellar travel is possible, even the " slow " kind nearly within the reach of Earth technology, then it would only take from 5 million to 50 million years to colonize the galaxy.

This is a relatively small amount of time on a geological scale, let alone a cosmological one.

Since there are many stars older than the Sun, or since intelligent life might have evolved earlier elsewhere, the question then becomes why the galaxy has not been colonized already.

Even if colonization is impractical or undesirable to all alien civilizations, large-scale exploration of the galaxy is still possible ; the means of exploration and theoretical probes involved are discussed extensively below.

However, no signs of either colonization or exploration have been generally acknowledged.