Extraterrerstrial Life – Have They Been Here? Will We Visit Them? Do They Exist At All?
Let us first talk about the Universe and what we know about it so far.
Cosmos or the Universe as we call it today is believed to consist of more than 150 billions of galaxies.
Typical galaxies range from dwarfs with as few as ten million (107) stars up to giants with one trillion (1012) stars, all orbiting the galaxy’s center of mass. Galaxies can also contain many multiple star systems, star clusters, and various interstellar clouds. The Sun is one of the stars in our Milky Way galaxy; the Solar System includes the Earth and all the other objects that orbit the Sun.
