# Are we alone in the Universe? The emergence of life

Previous “Drake Equation” – Next “Fermi Paradox
We are thinking creatures living on a planet orbiting a pretty common star in a pretty common galaxy. Our home planet has been around for about 4.5 billion years, while the Universe is about 13.7 billion years old. We just learned that there are about 1 000 000 000 000 000 000 000 = $$10^{21}$$ planets potentially similar to the Earth in the cosmos, a number larger than the amount of grains of sand found on every beach and every desert on Earth. Are we alone? To answer this question in 1961 scientist Frank Drake formulated his famous equation, which I discussed in the previous post of this series. The Drake equation calculates the number $$N$$ of communicative civilizations in our Galaxy. In its 2015 form it reads:

$$N \approx 2\, f_l \, f_i \, f_c \, L$$