re: Something to consider before sending nano-probes speeding off into space

It's my opinion that the odds of hitting another system in our galaxy are low, and hitting an actual planet in that system is well below a fraction of 1%.

Similar to how our crafts go through the asteroid belt easily without even seeing an asteroid

-The mass of our entire solar system is 1.0014 solar masses. So almost all of the mass is located in the sun.
-the diameter of the sun is about 900,000 miles
-from earth to the sun is 93 million miles, which equals 1 AU.
-pluto's average distance from the sun is 40 AU.
-Pluto is 5 light hours from the sun.
-Alpha Centauri is 4.25 light years from the sun.
-you could fit over 7,400 solar systems between here and Alpha Cebtauri (I only included sun to Pluto, not Ort cloud, since we are talking about hitting a habitable planet)

so you could pretty much fit 100 suns between the sun and earth, and 4,000 suns between the earth and Pluto. how many plutos you could fit between Pluto and the sun is mind boggling.
So the odds of randomly passing through our solar system and hitting a planet is very very small, the odds of even hitting a solar system passing through The Galaxy is very small, combined with odds of life on a random planet... I think we are fine

^mass is pretty spread out across the galaxy
: odds it hits nothing>>>odds it hits a star/sun>>>>>>>>>odds it hits a planet