The Drake Equation

Calculating the possibility of life

A 360º photo of the Milky Way seen from Death Valley, USA.

Image and more details may be found at http://antwrp.gsfc.nasa.gov/apod/ap070508.html

Is there life out there?

• Since the 1960’s astronomers have been trying to work out the probability of contacting extra-terrestrial life.

• To work out the overall probability we need to ‘guestimate’ the probability of a number of factors occurring.

R*,the rate of formation of stars in our galaxy

fp, the fraction of stars that have planets around them

ne, the number of suitable planets in each planetary system

fl the fraction of suitable planets which develop life

fi the fraction of life-bearing planets which develop intelligent life

ft the fraction of intelligent life bearing planets which develop technology

L, the length of time the civilisation releases signals into space

What if they’ve already tried to contact us and

we missed the call?

The Drake Equation

• To work out the number of civilisations in our galaxy with whom we might have a hope of communicating we multiply all these factors together.

LffnfRN tlep *

• Different astronomers and cosmologists use different values for each of these factors.

• However, it is generally thought that there is a finite chance of contacting extraterrestrial intelligent beings.