They're not going to be 1, so you're multiplying fractions. Start with us being the only radio broadcasting life out of 3.5 billion years of species on this pla

They're not going to be 1, so you're multiplying fractions. Start with us being the only radio broadcasting life out of 3.5 billion years of species on this planet, or how long it took to get to multicellular life on a relatively stable world with only occasional mass extinction events that doesn't turn the planet into a Mars or Venus.