I am so glad you asked.
It is explicitly stated that life is still open to possibility, and if life did flourish, it would be very different than we now know it to be. The author explores a simple example of having two identical moons, one at its current position from Earth, and another at half its distance from Earth. Nocturnal species would have much more difficulty surviving due to the fact that there would be, at times, a full moon in the night sky that covers four times the area that our Moon now covers. This is four times the amount of reflected sunlight, and Earth’s night would be four times brighter than it currently is. Not to mention, at times, having the outer Moon also visible from behind. Requiring highly refined camouflage would also initiate sharper hunting skills, which could possibly lead to more intelligent species.
Also, our “month” had been determined by the Moon’s cycle of phases, namely being about 29.5 days, roughly a 30 calendar day. With having an extra moon, not only would their orbits be more elliptical (thus the phases of the moon varying less uniformly,) but their would be two moons to keep track of, rendering our current calendar useless. Intelligent life, I imagine, would rely more on the inner moon, which would have a much higher orbital frequency (Kepler’s second law) and this calendar “month” would possibly have less days. That, or a combination of both moon’s orbital periods would allow for a highly complicated calendar system.
The inner moon would create high water tides about eight times higher than currently experienced by our Moon. Furthermore, there would also be higher land tides, which would cause a more geologically active Earth. The inner moon would be active with spectacular volcanoes that would cause matter to enter the Earth’s atmosphere. Their sky would continually be filled with meteors.
Lastly, the two moons would be destined to collide. As our Moon is, the inner moon would be continually escaping the Earth’s gravitational tug, but would do so at a faster rate than the outer moon. As they collide, lava would be ejected into space, and large enough impacts on the Earth to cause extinction would follow.
