by Lauren Lim
Photo by Neven Krcmarek on Unsplash
For millennia, humans observed the moon in the night sky, rising in the sun’s absence and fading as day arrives. Ancient civilizations told countless stories about the moon such as the Chinese legend of Chang’E who flew to the moon with a rabbit or the Greek belief that the titan goddess Selene drives the moon chariot across the sky each night. What we now know as a solar eclipse—when the positions of the earth, sun, and moon line up so that the moon obscures the sun temporarily—was once believed to be a Chinese dragon, or perhaps the decapitated head of the Indian demon Rahu, eating the sun every now and then (Petruzzello, 2021). In response, the Chinese scared off the dragon with loud drumming while the Hindus thought the sun passed back out Rahu’s throat since he had only half a neck. Of course, we now know what the moon truly is— a mostly spherical object made of rock and metals that likely split off from the Earth some 4.5 billion years ago—but it has far more effect on life on Earth than one might imagine (Cain, 2015).
Let’s start with something most people know: Tides are caused by the moon’s gravitational pull. But how does this work, and why is it important? As the Earth rotates, the moon’s gravitational pull distorts the Earth and its oceans slightly ("Tides | Moon in Motion – Moon: NASA Science", 2021). This happens on both sides of the Earth, because of the centrifugal force generated by the Earth’s spinning (Society, 2021). Over the course of a day, most shorelines will experience two high tides and two low tides since there is a bulge of water on each side of the planet. While the sun also affects tides, the main force involved is the moon (Society, 2021). But what relevance does this have to life on Earth? The intertidal region, the area that alternates between being exposed to air and sun during low tide and being submerged by the high tide, may have been an important site for the origin of life. Without a moon, or with a smaller one, tides may not have been strong enough to wash certain carbon-based compounds, which may have seeded life, into the water (Comins, 2008). Molecular biologist Richard Lathe also speculates that the intertidal areas of early Earth provided ideal conditions for proto-nucleic acid to form. DNA and RNA, now known as some of the most fundamental elements of life, could have originated from these early compounds (Dorminey, 2009).
Now, intertidal zones are homes to a variety of species that survive and thrive in both conditions. Tides also create tidal pools, small pockets of water in intertidal zones even during low tide, which form part of a diverse ecosystem that many predators depend on as a food source (Society, 2021). Additionally, many intertidal species, including some birds and marine animals, move in synchrony with the tides, in what is known as tidal migration (Gibson, 2003). The purpose of these regular journeys can range from hunting and reproduction to avoiding predators. A great example is mollusks, such as clams and oysters, which use the tide itself to move around. Overall, many organisms have evolved around shorelines, demonstrating one aspect of the moon’s role in the daily rhythm of life on earth.
The moon’s other influences on animals have little to do with the tide. One example is the dung beetle, which, according to senior curator at the National History Museum Dr. Tom White, “[relies] on polarisation patterns specific to moonlight in order to navigate and orientate themselves and travel safely home”(Lotzof, 2021). He also explains that, based on water temperature, salinity levels, and the lunar cycle, corals can synchronize their release of sperm and eggs. This spawning period changes every year and always comes after a full moon, but scientists are still uncertain how exactly corals time it so perfectly. Some fish and worms also breed according to moon cycles. Similarly, Barau’s petrels time their migrations based on the length of day and always arrive at their breeding ground, Reunion Island, on a full moon, but not necessarily the same time every year (Lotzof, 2021).
The moon also influences the length of Earth’s days, the stability of its rotation, and its climate, which indirectly affects all life in ways we are only beginning to understand such as human emotions and sleep quality (Comins, 2008). While there are many things we have yet to discover, our understanding of the small white orb we see in the night sky has come incredibly far from the myths and legends of our ancestors.
References
Cain, F. (2015). Did we need the moon for life?. Phys.org. Retrieved 14 November 2021, from https://phys.org/news/2015-11-moon-life.html.
Comins, N. (2008). What would happen to Earth if the moon was only half as massive?. Scientific American. Retrieved 14 November 2021, from https://www.scientificamerican.com/article/half-mass-moon/.
Dorminey, B. (2009). Without the Moon, Would There Be Life on Earth?. Scientific American. Retrieved 14 November 2021, from https://www.scientificamerican.com/article/moon-life-tides/.
Gibson, R. (2003). Go with the flow: tidal migration in marine animals. Hydrobiologia, 503(1-3), 153-161. https://doi.org/10.1023/b:hydr.0000008488.33614.62
Lotzof, K. (2021). How does the Moon affect life on Earth?. Nhm.ac.uk. Retrieved 14 November 2021, from https://www.nhm.ac.uk/discover/how-does-the-moon-affect-life-on-earth.html.
Petruzzello, M. (2021). The Sun Was Eaten: 6 Ways Cultures Have Explained Eclipses. Encyclopedia Britannica. Retrieved 14 November 2021, from https://www.britannica.com/list/the-sun-was-eaten-6-ways-cultures-have-explained-eclipses.
Society, N. (2021). Tide. National Geographic Society. Retrieved 14 November 2021, from https://www.nationalgeographic.org/encyclopedia/tide/.
Tides | Moon in Motion – Moon: NASA Science. Moon: NASA Science. (2021). Retrieved 14 November 2021, from https://moon.nasa.gov/moon-in-motion/tides/.
Comments