The Drake equation which is used to describe a rough estimate of possible ET civilizations that is able to communicate with us does not take into account the abundance of the chemical elements in the universe.

The equation is:

$$ N = R_* ~ f_p ~ n_e ~ f_l ~ f_i ~ f_c ~ L $$

$N$ = 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.

$f_p$ = The fraction of those stars with planetary systems.

$n_e$ = The number of planets, per solar system, with an environment suitable for life.

$f_l$ = The fraction of suitable planets on which life actually appears.

$f_i$ = The fraction of life bearing planets on which intelligent life emerges.

$f_c$ = 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.

but so far, there is no number for the density nor the abundance of chemical elements, even though life actually depends on various elements

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    $\begingroup$ No advanced civilization would ever want to communicate with such silly and self destructing creatures like us. $\endgroup$ – safesphere Dec 1 '18 at 4:22
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    $\begingroup$ This would be covered by "ne" in your list. $\endgroup$ – Mitchell Porter Dec 1 '18 at 4:31
  • $\begingroup$ it's not detail though because most planet are made up of gases. and "what is suitable for life" is very wide place to define $\endgroup$ – Omar Adel Dec 1 '18 at 5:06
  • $\begingroup$ @NimbleDickCrabb Exactly. So by this argument, also the relative abundance of elements doesn't give any more information than what is already contained in $n_e$. Depending on how you define 'life', $n_e$ is larger or smaller and accounts for all factors that determine how frequent environments are that can sustain life. $\endgroup$ – ahemmetter Dec 4 '18 at 8:33

This is included in $n_e$.

The elements heavier than lithium were mostly made in generation II stars then spread out by supernovae. The abundances of these elements are all correlated, so a stellar system that has enough oxygen, silicon and aluminium to make planets like the Earth automatically has enough carbon, nitrogen and oxygen to make the life forms that infest it.

That means we don't have to worry specifically about the abundances of the life forming elements. We need only include the number of Earth like planets.


The Drake equation is based on a steady state assumption. It describes a galaxy where civilizations appear and disappear at the same rate. Hence it does not handle changes in arrival time (or very long lived civilizations that would still be accumulating).


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