The ingredients for complex life

This week we’ve looked at extreme events on cosmological and geological timescales.

In Activity 2, Dr Morten Andersen explained how Earth was formed and took the shape we know today.

In Activity 3, Dr Ernest Chi Fru, focussed in on events that highlight the importance of CO₂ in the atmosphere (without it the planet would be inhospitably cold) and oxygen – without which life would not exist.

Given that we need extreme, i.e. rare and large events to be able to support intelligent life, are we unique in the universe? Or did other intelligent lifeforms evolve on other planets? Humans have pondered about this question through the ages.

The Drake equation

Let’s go back to the Drake equation. Earlier we calculated how many planets in our galaxy could support life. We can adopt the same equation with a couple of additions to consider whether other planets can and have supported intelligent life.

First, let’s redefine N as follows:

N = the number of civilisations (intelligent life) in our galaxy

N = R* x fp x ne x fl x fi x L

Step 1

Step 2

Step 3

Calculating N

N = R* x fp x ne x fl x fi x L = 7/year x 1 x 3/8 x 1/3 x 1 x 10⁵ year = 87500

N = R* x fp x ne x fl x fi x L = 7/year x 1 x 3/8 x 1/3 x 1/87500 x 10⁵ year = 1

Our answers are not meant to be precise, rather they help us reflect on the conditions that are necessary for life.

Based on these potential answers we could conclude that we expect roughly between 1 and 87500 (could be rounded to 100000 if we are generous) habitable planets in our galaxy that have life on them.

Although the most optimistic estimate might seem like a lot, our galaxy is so large it would be like finding a needle in a haystack.

Over to you

• What are your reflections on these answers?
• Does it make you think differently about our planet and galaxy?
• If so in what ways?