of all the incredible stuff out there in space, globular clusters are surely among the most mind-blowing when you pause and consider what could be going on deep inside their luminous cores. these vast blobs of light are made of millions of stars, some of which could be the cradle of civilisations, distant in time and space

to make sense of the sheer numbers and possibilities, Dr. Frank Drake devised a famous equation while working as a radio astronomer at the National Radio Astronomy Observatory in Green Bank, West Virginia. the Drake Equation, as it has famously become known, was first presented in 1961 and is usually written:

N = R* • fp • ne • fl • fi • fc • L


N = the number of civilizations in The Milky Way Galaxy whose electromagnetic emissions are detectable

R* =the rate of formation of stars suitable for the development of intelligent life

fp = the fraction of those stars with planetary systems

ne = the number of planets, per solar system, with an environment suitable for life

fl = the fraction of suitable planets on which life actually appears

fi = the fraction of life bearing planets on which intelligent life emerges

fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space

L = the length of time such civilizations release detectable signals into space

now, to celebrate the publication of a special issue of International Journal of Astrobiology, two articles are being made freely available to the public. the first is a retrospective written by Drake, while the second article explores equation in light of the Fermi paradox: which basically asks, if stars and planets are so common, where are all the aliens?

the two papers, listed below, are available free for three months:

"Reflections on the equation", F. Drake

"A joint analysis of the Drake Equation and the Fermi Paradox", N. Prantzos