When it seemed that everything possible had already been seen, China arrives and once again turns into reality what seemed like a true chimera. Beijing has shifted the earth’s axis, modifying the length of the day. Obviously, it has not been done on purpose (it has been an indirect effect of an engineering work), but it is the consequence of its economic and energy development. The Three Gorges Dam, nestled majestically on the Yangtze River, is not only a titanic feat of modern engineering, but also a reminder of how humanity can leave its mark on planetary systems. This concrete colossus, capable of containing up to 39.3 billion cubic meters of water, subtly alters the rotation and axis of the Earth. With a barely perceptible impact, it lengthens the length of the day by 0.06 microseconds and shifts the Earth’s axis about 80 centimeters to the east.. Like an echo in the cosmos, the dam’s influence highlights how our buildings can compete with natural phenomena of colossal magnitude, such as earthquakes or tsunamis.
Built between 1994 and 2012, the Three Gorges Dam not only generates energy equivalent to about 22 nuclear plants, but has also dramatically transformed the Yangtze ecosystem. Although its hydroelectric capacity mitigates carbon emissions, Its construction displaced 1.3 million people and altered the habitat of multiple species. This dilemma symbolizes the duality inherent in human progress: energy benefits versus social and environmental costs. Despite all this impact, Beijing has recently approved the construction of another dam that will be much larger than the Three Gorges.
The rotational effect, a dance of balance
The impact of the Three Gorges Dam on the Earth’s rotation is a metaphor for the dance of balance between nature and human engineering. The concentration of such an amount of water increases the planet’s moment of inertia, slightly slowing its spin, just as a figure skater slows down by extending his arms.
From the specialized environment, astronoo They explain it as follows: an accumulation of a mass of water (39.3 billion cubic meters of water) occurs and is stored at a higher altitude than the average land surface in that region. When this water moves from the river (at a lower level) to the reservoir (at a higher level), changes the distribution of the Earth’s mass.
By storing a large amount of water at a higher altitude, the Earth’s moment of inertia increases. In fact, the further the mass is from the axis of rotation, the more it contributes to increasing the moment of inertia. A decrease in the Earth’s angular velocity means that it takes the Earth a little longer to complete one rotationwhich translates into a very minimal increase in the length of the day, they assure from this medium.
Another more graphic way of looking at it is the following: the concept of moment of inertia is key to understanding this phenomenon. The further a mass is from its axis of rotation, the greater its ability to slow down rotation. The massive accumulation of water in the reservoir, located far from the earth’s axis, acts like a gigantic weightaffecting in a tiny but tangible way the balance of the planet. This physical principle, although abstruse, exemplifies how even a seemingly localized action can have consequences on a planetary scale.
Although the effect is almost imperceptible in practical terms, its measurement highlights science’s ability to detect even the faintest whispers of our influence on Earth. This phenomenon, however, pales in comparison to the changes caused by natural disasters, such as the earthquake in Chile in 2010 or the tsunami in Southeast Asia in 2004, which also altered the Earth’s rotation.
An axis that moves under our footprint
Between 1993 and 2010, human activities, including the construction of the Three Gorges Dam, shifted the Earth’s axis 80 centimeters to the east, according to studies published in Geophysical Research Letters. This phenomenon, measured with millimeter precision, illustrates how the redistribution of masses, such as the 39.3 billion cubic meters of water retained by the dam or the 2,150 gigatonnes of groundwater pumped and discharged into the oceans, affects the balance of the planet. Although this change is minuscule from an everyday perspective, its measurement demonstrates the cumulative reach of our interventions.
In this way, the Three Gorges Dam stands as a symbol of the Anthropocene era (the concept ‘anthropocene’ was popularized in the year 2000 by the Dutch chemist Paul Crutzenwinner of the Nobel Prize in chemistry in 1995, to designate a new geological epoch characterized by the impact of man on the Earth), where human activities begin to compete with geological forces.
This rotational impact, although minor compared to natural disasters, highlights the immense accumulated power of modern engineering. Beyond its numbers and measurements, the dam raises questions about our responsibility in managing projects of such magnitude. As an imposing reminder of the human capacity to alter the natural course of the Earth, it invites us to reflect on the type of mark we want to leave on our planet.
This type of pharaonic works also generate certain tensions between countries, especially when natural resources are shared, as is the case with the Nile River in Africa, where the colossal Ethiopian Renaissance Dam has put Egypt and Sudan on a war footing against Ethiopia.
A legacy for posterity
The Three Gorges Dam is a landmark that transcends its original function of generating power or controlling floods. It is a monument to the ambition of a giant that wants to become the greatest economic power in the world and to do so it needs to generate energy in abundance. While analyzing its effects on the Earth’s rotation, it is worth remembering that human impact, although sometimes imperceptible, can resonate through the ages.
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