Several theories have been propounded about the possible basis of alien life from a biochemical, evolutionary or morphological viewpoint.
Alien life, such as bacteria, has been theorized by scientists such as Carl Sagan to exist in the Solar System and quite possibly throughout the Universe. Hitherto, no samples of the same have been found though.
Certain scientific-minded people, and a small circle of the scientific world have concluded that there is a strong possibility of the existence of life forms in other planets or stars. How did they conclude that there is intelligent life elsewhere in our galaxy? The Green Bank formula is a way to statistically guess the possible number of intelligent civilisations in our galaxy, the Milky Way. The equation is used to estimate the number of detectable extraterrestrial civilizations in our galaxy. It is used in the fields of exobiology and the search for extraterrestrial intelligence (SETI). The equation was devised by Frank Drake in 1961. Dr Carl Sagan, who was a good friend of Sivaya Subramuniyaswami, had explained the equation in his book, Cosmos.
N = the number of stars or civilizations in our galaxy with which communication might be possible. It is estimated that there are 400 billion stars, and
R* = the average rate of star formation per year in our galaxy
fp = is the number of planets. one in three stars may have a solar system, averaging perhaps 10 planets each, for a total of 1,300 billion planets. Since 1995, more than 6 nearby stars were confirmed to have planets around them.
ne = is the number of planets that can potentially support life per star that has planets. Since life exists on Earth in a wide range of temperature and environment, this is guessed at two per system. That gives a total of 300 billion planets on which life might evolve.
fℓ = the fraction of the above that actually go on to develop life at some point. It was estimated by Carl Sagan (based on the range of scientific opinion) at one in three. That means there might be 100 billion inhabited worlds.
fi = the fraction of the above that actually go on to develop intelligent life. Such a development might be rare, or it might be inevitable. Sagan uses the conservative figure of one in ten. We could have in our galaxy an estimated 10 billion worlds with intelligent life.
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space. This is estimated at one in 10, for a total of one billion technically advanced civilisations in the galaxy.
L = the length of time such civilizations release detectable signals into space. Does an advanced civilisation destroy itself, as we on Earth seem inclined to do, or does it endure for millions of years? If even one percent survive, states Sagan, “The number of such advanced living civilisations is in the millions.”
According to Hindu scriptures, there are innumerable universes to facilitate the fulfillment of the separated desires of innumerable living entities. However, the purpose of such creations is to bring back the deluded souls to correct understanding about the purpose of life. Aside from the innumerable universes which are material, there is also the unlimited spiritual world, where the purified living entities live with perfect conception about life and ultimate reality. The spiritually aspiring saints and devotees, as well as thoughtful men of the material world, have been getting guidance and help from these purified living entities of the spiritual world from time immemorial. However, the relevance of such descriptions has to be evaluated in the context of a correct understanding of geography and science at those times.
Hindu scriptures often speak of the many lokas, or planes of existence, and dvipas, or islands. They talk of beings coming from other lokas to this loka, possibly even of spaceships in which they could travel. These lokas, however, are more commonly interpreted as other dimensions of existence rather than physical planets.
His Divine Grace A.C. Bhaktivedanta Swami Prabhupada, founder of ISKCON, addressed this question in his commentary on Srimad Bhagavatam: “According to Vedic understanding, the entire universe is regarded as an ocean of space. In that ocean there are innumerable planets, and each planet is called a dvipa, or island. The various planets are divided into fourteen lokas. As Priyavrata drove his chariot behind the sun, he created seven different types of oceans and planetary systems, known as Bhuloka.” (Bhag 8:19:19)
Srila Prabhupada also stated that according to the Vedic tradition there are 400,000 species in the universe with humanlike form, many of them advanced beyond us. Other parts of Hindu scripture refer to travel to other worlds. The Rig Veda hymns on death speak of man’s soul traveling to the sun and the moon, then returning to Earth.
[pgs, xxiii-xxiv, Lemurian Scrolls. References had also been made to Vedic Cosmography & Astronomy, Scientific American (Aug, 2002)]