However, if you think that Earth is alone in this regard, it might be as low as 1 in 100,000,000,000.

However, that may be too optimistic, so you might expect that 1 in 10, 1 in 100, or 1 in 1,000,000 develop life. Scientists studying the origin of life think that, given the right conditions (temperature, presence of water, etc.), life may develop on every Earth-like world, or f l = 1. For f l, you have to make an educated guess. If it is common, you might estimate say 2 objects per Solar System for n e. What we still do not know is if our Solar System is common or rare. So, in the Solar System there is definitely one, and maybe more than one, planet (or moon) capable of supporting life. Europa, Ganymede, and Titan are outside of the CHZ, but may have environments that can support life. Venus and Mars are either close or in the CHZ depending on the model used. The rest of the values in the equation require you to either extrapolate using limited information or outright guess.įor n e, we can use the Solar System as a guide. Also, from our observations of stars with protoplanetary disks and with extrasolar planets, we think that f p is likely 1 or close to 1, too. That number appears to be very close to 1 star per year. For example, we can estimate R * from our observations of star forming regions in the Galaxy.

Several of these terms have values that we can estimate with some degree of accuracy.

L = the average lifetime of those civilizations that develop technology for communication.

f c = the fraction of those intelligent civilizations that develop technology for communication.

f i = the fraction of those planets with life where intelligent life develops.

f l = the fraction of those planets that can support life on which life actually develops.

n e = the average number of planets per planetary system that have an environment that can support life.

f p = the fraction of those stars that have a planet or planets.

R* = the rate at which stars capable of supporting life form in our Galaxy.

N = number of civilizations in the Milky Way Galaxy that are capable of producing signals that we can detect on Earth.

The equation is: N = ( R * ) × ( f p ) × ( n e ) × ( f l ) × ( f i ) × ( f c ) × ( L ) With this equation, you can estimate the number of communicating, intelligent civilizations that currently exist in the Milky Way. One of the tools that you can use to consider this topic is known as the Drake Equation, after astronomer Frank Drake who proposed it in the early 1960s. This does not mean that scientists have completely ruled out the possibility of intelligent life in the Milky Way Galaxy, though.

Scientists expect that, if we discover life on Mars, it will most likely be simple bacterial life and not humanoid aliens like most of the martians you have seen in movies. Drake Equation: How Many of Them Are Out There?.

Civ 6 on towards the stars