### The Drake Equation

Frank Drake devised the "Drake equation" - a formula to calculate how many civilisations might be broadcasting radio signals. This is the Drake equation.

## N = R_{*} x f_{p} x n_{e} x f_{l} x f_{i} x f_{c} x L

**R _{*} is the rate starbirth. **

The number of new stars formed in the Galaxy. This is widely accepted by astronomers to be 10 per year.

**f**

_{p}is stars with planets.The percentage of those new stars that form planets.

**n**

_{e}is habitable planets.The number of those planets that are the right distance from their star, and of the right size to be suitable for life.

**f**

_{l}is planets with life.The percentage of those planets on which life has actually evolved.

**f**

_{i}is intelligent life.Percentage of planets where life forms have evolved sufficiently for "intelligent" creature to exist.

**f**

_{c}is communicable life.The percentage of those planets on which intelligent lifeforms have developed technologically so they can communicate with other civilisations.

**L is life span of civilisation.**

The length of time that a technologically advanced civilisation exists and in which it can send a potentially receive signals.