- A recent review of the scientific literature shows that the gravitational forces that cause the tides are also associated with the rhythms of organisms such as plants, crustaceans and corals.
- Researchers say gravitational cycles are not being accounted for in scientific experiments that otherwise control for various environmental factors in the laboratory.
- In the field of gravitational effects, many practices that are repeated out of popular wisdom, such as the best time to cut wood or plant crops, still don’t have scientific backing.
Electrical engineer Cristiano de Mello Gallep was working in a biophotonics laboratory in the city of Limeira, in Brazil’s São Paulo state, trying to measure self-luminescence in organisms — the ability of plants to glow in the dark, essentially. The experiments with seed germination took days, and Gallep, a researcher at the University of Campinas (Unicamp), noted that variations in the growth curve of plants made it impossible to compare the tests when conducted on different days or even at different times.
“So we went after the literature,” he says. “It seems pretty obvious after we find out, but what varies day to day, month to month and also throughout the year is the gravity that causes the tides, the most visible effect that everyone knows of.”
So Gallep expanded the scope of his tests to other types of seeds, and combined them with the results obtained from partner laboratories, publishing his findings in 2014.
Reviewing that information and taking into account two other studies on the subject, Gallep and biologist Daniel Robert from the University of Bristol in the U.K. have now come out with an extensive meta-analysis to show evidence that the rhythmic activity of organisms is closely associated with the effects of the sun and moon’s gravitational forces on the Earth.
One of the earlier studies in the meta-analysis, published in 1965, demonstrated that, in a laboratory with controlled water conditions and without the influence of ocean tides, crustaceans maintained a pattern of behavior and swimming consistent with the timing of the tides in the locale near where they had been collected. Another study, published in 1985, pointed to the variation, also in a controlled lab, in the reproduction of coral colonies according to gravitational changes.
Rhythm of the tides
Within the confines of a scientific research lab, the leaves of plants sway. And no sea breeze is capable of penetrating this environment of closely controlled variables. Yet a 2015 study had already shown that the oscillation patterns in the leaves of different species were synchronized with local tidal patterns.
“Every time the plant raised or lowered its leaf, it coincided with an inflection: the tide is rising, the tide is going down,” Gallep says. “And even plants that have always grown in the same controlled light, without exposure to the sun, continue to do so.”
Researchers and keen observers of nature have been concerned with biological cycles and rhythms for centuries. Back in the early 18th century, Swedish botanist Carl Linnaeus, one of the most important in Western science history, predicted the times that the petals of different flowers would open and close. When studying the impact of light and dark conditions on plants in 1729, Jean-Jacques de Mairan, a French astronomer credited with laying the foundation for modern chronobiology, said that plants sense the sun without seeing it. Since then, knowledge about biological mechanisms has greatly expanded.
“Every living thing oscillates. Matter itself oscillates. But it oscillates in temporal patterns that escape our perception,” says Luiz Silveira Menna Barreto, coordinator of the Multidisciplinary Group of Biological Development and Rhythms at the University of São Paulo (USP), which was not involved in Gallep’s meta-analysis.
“The authors revived this possibility that gravitational cycles are partly determinant of rhythmicity,” Menna Barreto says of the new paper. “At the beginning of chronobiology, the environmental light-dark cycle was the dominant cycle and the so-called circadian rhythms, which coincide with night and day, were the most important rhythms. This is no longer accepted today.”
The right moon
Pointing to the importance of the effects of gravitational forces, the meta-analysis says that this variable has gone largely uncounted for in scientific experiments described as free experiments — those with a number of controlled environmental factors. In addition to the constancy of light, humidity and temperature, there are other patterns that impact organisms, such as fluctuations in the geomagnetic field and flow of cosmic rays. The gravimetric tide itself cannot be discounted in laboratory conditions, but the observation of a larger set of variables can provide richer and more structured information about the organisms under analysis.
“The authors say that these gravitational waves were present on Earth ever since the beginning of life and they persist to this day. It is possible that organisms have a history in relation to these gravitational cycles,” Menna Barreto says, pointing to the need for scientists to include the history of organisms in their research. “By including the history of organisms, we can no longer say that rats, nocturnal animals, are good models for the study of the human nervous system. They’re not,” he says.
For Menna Barreto, also a professor at the USP School of Arts, Sciences and Humanities, science is not static. “Science does not own the truth. It produces knowledge that is continuously being discussed and superseded. Science is dynamic.”
In the field of gravitational effects, many observations don’t yet have scientific backing. “Nowadays, we intervene in things in such an artificial manner that we no longer see the most natural processes. This doesn’t mean they don’t exist and it doesn’t mean they’re superstition either,” Gallep says, noting that anyone who lives on a farm knows when they have the right moon for fishing and the right moon for cutting wood.
“People see when a pattern works and they keep repeating it,” he says. “It wasn’t some nonsense that someone just came up with. It was an observed fact. We just haven’t scientifically detailed the process yet.”
Banner image by Francesco Gallarotti/Unsplash.
de Mello Gallep, C. (2014). Ultraweak, spontaneous photon emission in seedlings: Toxicological and chronobiological applications. Luminescence, 29(8), 963-968. doi:10.1002/bio.2658
de Mello Gallep, C., & Robert, D. (2021). Are cyclic plant and animal behaviours driven by gravimetric mechanical forces? Journal of Experimental Botany, 73(4), 1093-1103. doi:10.1093/jxb/erab462
Enright, J. T. (1965). Entrainment of a tidal rhythm. Science, 147(3660), 864-867. doi:10.1126/science.147.3660.864
Jokiel, P. L., Ito, R. Y., & Liu, P. M. (1985). Night irradiance and synchronization of lunar release of planula larvae in the reef coral Pocillopora damicornis. Marine Biology, 88(2), 167-174. doi:10.1007/bf00397164
Barlow, P. W. (2015). Leaf movements and their relationship with the lunisolar gravitational force. Annals of Botany, 116(2), 149-187. doi:10.1093/aob/mcv096
This story was reported by Mongabay’s Brazil team and first published here on our Brazil site on Feb. 24, 2022.