What do you mean by light travelling distance? 1 light year?
They say that there are billions of earth-planets in our galaxy so the chance of aliens existing is extremely high.
We have found several planets but we haven´t found life simply because of the reason that we can´t travel to it.
Hell we can´t even see planets from here, we see fluctuations of the star that the planet orbits.
It´s impossible to tell if there are life forms on those planets if you don´t actually travel to the planet itself.
radio frequencies haha that´s caveman style type of conversations. It would be like sending a text message to someone by taking a piece of rock and etch in the letters then send it down the mountain.
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Milky Way has 2 billion earth like planets. 2 billion.... and we are one of them.
there are about 100 billion sun-like stars in our galaxy.
We have found (February 2011) 1.235 earth planets in our galaxy.
http://www.space.com/11188-alien-earths-planets-sun-stars.html
There may be 500,000 Earth-like planets in our galaxy alone
Yesterday’s announced discovery of Earth-like planet Kepler-22b brought with it renewed speculation over the possibility of life on other worlds. And while the news was exciting, there’s growing evidence that it’s only a drop in the bucket when it comes to finding habitable worlds in our cosmic neighbourhood, Yahoo News reports. Space.com has provided a handy guide to some of the 700 planets discovered by the Kepler telescope outside of our solar system. The findings include “Super-Earth” planets such as Kepler-22b and even possible “Water Worlds,” like the planet GJ 1214b, which may be covered in vast oceans of water. And outside this “habitable zone” are other interesting finds, including several “Rogue Planets” that orbit the Milky Way galaxy independently after they were ejected from their solar system. daily times monitor
http://www.dailytimes.com.pk/default.asp?page=2011\12\08\story_8-12-2011_pg9_6
If we go by the last quote, Let´s assume only 10% of those holds a civilization.
That´s 50.000 different civilizations in our galaxy alone. If we take 10% of those and assume they are highly developed (more then us) you have 5.000 different "species" of aliens.
An extraordinary number even by counting extremely low on earth planets.
So the thought of that at the very least one of these 5.000 civilizations have noticed our planet and solar system should be fairly large considering we with our relatively low-tech equipment have found an incredible amount of planets ourselves.