In our galaxy, stars are distributed such that there is a star roughly every light year.
The actual distance between them depends on where we are within the galaxy - stars are
closer together near the center and they are spread farther apart in, for example, our
neighborhood, the outer spiral arms.
The closest star to our Sun is a little over four light years away, but even at this relatively
close distance, getting to it may prove impractical. The distances to even our closest stellar
neighbors is daunting; the voyage plagued by the painfully slow speeds we are forced
to abide.
The current state of our technology limits how fast we're able to go. Our foreseeable
future does not seem to disclose a path to enabling the very fast speeds required for
convenient and speedy interstellar journeys.
As an example, let's take a look at how our current interstellar probes are doing. The
Pioneer 10 and 11, and the Voyager I and 2 probes are all on a trajectory out of our
solar system and will eventually reach the stars.
As of March 27th, 2011, Voyager I, the most distant of the probes, was 116 astronomical
units, or 17 435 946 096 kilometers away and is speeding away at 17 km every second.
If we include it's circular trajectory as it left Earth and past the outer planets,
the Voyager 1 probe has travelled a total of 19 billion kilometers since it was launched
in 1977.
Now that it has finally left the boundaries of our solar system, it's speed isn't likely
to change very much in the future, so we can use its current speed to answer the question,
how long will it take to get to the stars?
At this velocity, Voyager is on pace to traverse one light year in 17,500 years. Slowly but
surely both Voyager probes will reach the stars. In about 40,000 years, Voyager I will
roam within 1.6 light years of the star AC+793888 in the constellation Camelopardalis.
In 296,000 years, Voyager 2 will pass within 4.3 light years of Sirius, the sixth closest
star to us in the constellation Canis Major.
These are the fastest vehicles ever constructed by human beings and their arrival time to
the stars is measured in tens of thousands of years.
To take almost 300,000 years to travel to the sixth closest star does not make for practical,
convenient journeys within our galaxy. Either we must invent new technologies to speed up
our spacecraft, or build generation ships that would land our very distant decendants
on the shores of another world.
Pioneers 1 and 2, along with the Voyager probes are inching their way into the vast reaches
of interstellar space. While the pioneer spacecraft are no longer functioning, both of the Voyager
probes are still active. Still recording data, their distant, feeble signals reaching Earth
in a whisper.
As they finally make their way past the closest stars to our Sun, they will act as our emissaries,
carrying an interstellar greeting card filled with images and sounds of the planet that
sent them on their way.
It isn't likely that anyone will ever open our greeting card, but the fact they every
probe we've launched outside of our solar system carries one, reflects the hope that
if anyone does, they've likely managed to survive The Great Filter and are successfully
living among the stars.