can we find life in other planets of our solar system?
By jaginfo2006
@jaginfo2006 (1757)
India
3 responses
@Withoutwings (6992)
• United States
1 Dec 06
There is an equation called the Drake Equation that gives a means of estimating the number of civilizations capable of communication that are in the Milky Way Galaxy. Dr. Frank Drake devised the equation in 1961 while working on "Project Ozma", a search for artificial signals from two nearby stars. People involved in the Search for ExtraTerrestrial Intelligence (SETI) use the equation today to show that their searches are not in vain.
The Drake Equation, as far as mathematical equations go, is quite simple. It consists of a string of unknowns multiplied by each other - that's it, no integration, no differentiation, nothing more difficult that multiplication. This means that the equation is accessible to pretty much everyone. Here it is:
N = R* fp ne f l fi fc L
Where:
R* is rate of formation of suitable stars (stars like the Sun) in the Milky Way galaxy
fp is the fraction of those stars that have planets
ne is the number of planets capable of sustaining life around each of those stars having planets
fl is the fraction of planets capable of sustaining life that actually evolve life
fi is the fraction of those planets where live has evolved that evolve intelligent life
fc is the fraction of planets with intelligent life that develop the capability to communicate
L is the fraction of the planet's life during which the intelligent life can communicate
The equation looks simple enough, but several of the quantities are unknown, even with our "advanced" knowledge of astronomy. In fact, the only quantity that we can currently say we know with any accuracy is the rate of star formation in the galaxy. Current estimates of the star birth rate in the Milky Way range from about 3 to 10 per year. However, the criteria that these stars be suitable means that they must be F, G or K stars, and these stars account for about 10% of the stars in the Galaxy. That means that 0.3 to 1 suitable stars are born each year.
Astronomers are currently able to detect large planets around other stars, so the fraction of planets with stars may one day be an observable quantity. However, currently only large planets can be detected, so the challenge is extrapolating the number of Earth like planets from the observed systems with large planets. In the not-too-distant future, we may be able to detect smaller planets around nearby stars. In fact, at least one project, Darwin , is underway to detect Earth sized planets around other stars, but it will take many years before this project gets off the ground (literally). Once we've detected extra solar, Earth sized planets, we can make more accurate predictions about how many planets per system are capable of sustaining life. For our own solar system, we would guess that three planets lie in about the right places and are of the right size to sustain life - Venus, Earth and Mars.
Detecting and predicting life on other planets is another order of magnitude (or more) more difficult than detecting Earth sized planets around distant stars. We are currently having a hard enough time determining if life ever existed on Mars, our closest neighbor. This means that all of the other variables in the Drake equation are subject to wild speculation. Fortunately, any of the "f" values are constrained to be between 0 and 1 (since they are fractions), so there is a definite upper limit to those values.
Let's take a stab at some of these numbers. Let N* = 1 (the most optimistic value given above), ne = 2 and L = 10,000 years (maybe a bit optimistic, since we've only been communicating for several decades). Let's try a couple different things for the fractional numbers (fp, fl, fi, fc)
If we let fp = fl = fi = f c = 0.5 (middle of the road), then N = 2,500
If we let fp = fl = fi = f c = 0.1 (one smallish side), then N = 20
If we let fp = fl = fi = f c = 1 (their maximum), then N = 20,000
What does this mean? Well, our Galaxy could be littered with intelligent, communicating civilizations, or we could be fairly unique. Hopefully, future studies of extra solar planets will help to constrain the planetary numbers. The "life" numbers, however, will likely be open to speculation for some time to come.