What Would Happen if the Earth Spun in the Opposite Direction?

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Issue 11, Volume 111

By Hellen Luo 

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Approximately 4.5 billion years ago, a molecular cloud of disturbed gas and dust began to collapse inward as the force of gravity pulled everything together, forming the solar nebula. At the center of this huge rotating disk, particles of gas and dust accreted into a dense ball of gas—the prestellar core of the Sun. When the core gradually reached a temperature of 10 million Kelvin and was hot enough to generate energy through nuclear fusion, the Sun contracted until it arrived at a state of hydrostatic equilibrium and officially became a main-sequence star. Consequently, leftover particles in the outer rings began to clump up into larger particles, in which solar winds blew away the lighter materials and left only the heavy, rocky ones to transform into smaller terrestrial planets, namely Earth. Ever since, our earth has been rotating on its axis in the same prograde direction as the Sun, from west to east, completing a full rotation every 23.9 hours at a speed of 1,670 kilometers (1,040 miles) an hour.

Venus is the only planet in the solar system that rotates backwards, though Uranus rotates at an extreme angle of 98 degrees. Scientists hypothesize that Uranus’s unusual rotation is due to a massive collision with another celestial object, such as an asteroid, that disturbed its original rotation. Meanwhile, other scientists believe that instead of a single collision, the sideways spin is likely to be caused by several smaller crashes that knocked the planet on its side. Regardless, it would also most likely require a significant asteroid impact or a number of mini-bumps for Earth to start rotating in the opposite direction. “That event itself would [be] disastrous,” astronomy and astrophysics professor from Penn State University Kevin Luhman said. However, let’s say we take a remote controller and magically reverse the rotation without experiencing dramatic calamity. What exactly would happen if the Earth began to spin in the opposite direction?

One of the most consequential effects of the Earth’s axial rotation is the Coriolis effect, which is largely responsible for the deflecting pattern of wind motion and air circulation to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. If the Earth were to spin backward, the pattern of the Coriolis effect would be upended such that the entire climate system of our planet would be disturbed. BBC meteorologist Peter Gibbs explains, “The Coriolis effect transfers the spin of the Earth into the circular motion of winds around a weather system. [...] Reverse the rotation of the Earth and you put the storms into reverse too.”

The reverse in the spin of the Earth would indicate a reverse in the directions of trade winds such that the ones normally blowing from the northeast will now come from the northwest. With reversed directions, westbound flights would suddenly be much shorter than eastbound flights. This change could also reverse the direction of natural disasters, including typhoons and hurricanes. For instance, a cyclonic rotation would no longer spin counterclockwise in the Northern Hemisphere or clockwise in the Southern Hemisphere, causing the location of storms and affected areas to change on a global scale.

A group of scientists led by Florian Ziemen conducted a simulation at the Max Planck Institute for Meteorology in Hamburg, Germany to model the effects of the Earth spinning backward by fast-forwarding the virtual calendar of the model up to 7,000 years in the future. They found that the dissolved oxygen levels in the northern Indian Ocean would dramatically decrease as the depth of the water column increases. This unusual phenomenon is mainly caused by the interplay of circulation and high biological production in that specific region, forcing many species of microorganisms to consume nitrates instead of oxygen. Cyanobacteria, however, do not necessarily need nitrates for survival, allowing them to thrive in areas with low levels of nitrate. As a result, cyanobacteria would become the dominant biological producers in many marine ecosystems. An excessive number of cyanobacterial blooms could use up even more oxygen and block out sunlight for organisms that reside below the water surface, causing a major environmental problem that would disrupt the balance of aquatic life.

Besides the Coriolis effect and biological activities, the normal rotation of the Earth plays an important role in distributing the location of different biomes, like deserts, forests, and swamps, on the planet. According to Ziemen’s team’s model, the Sahara desert would surprisingly disappear and the Middle East would receive sufficient precipitation to support plant growth. On the other hand, deserts would move to the southeastern regions of the United States and large parts of Brazil and Argentina, which could potentially displace the habitats of species and reverse economic development in those areas.

In fact, Earth would become a greener planet if its rotation were in the opposite retrograde direction. Deserts would shrink from 42 million square kilometers to 31 million kilometers. Additionally, carbon dioxide emissions—one of the main greenhouse gases—are undoubtedly the foremost contributing factor to accelerating global warming. Since plants use carbon dioxide as one of their reactants to produce carbohydrates through photosynthesis, more plants would absorb more carbon dioxide from the atmosphere. Therefore, if the Earth were to spin backwards, the effects of climate change and global warming would decrease as terrestrial ecosystems would now allow more plant life to emerge.

In that case, the reversed spin of our planet may not be as catastrophic as it sounds. Research studies on our planet’s rotational direction have provoked a considerable number of debates and discussions on whether a backward-spinning Earth would be a better place to live than our present Earth. Though studies have shown that a backward-spinning Earth will be less affected by global warming, we should avoid relying on these hypothetical phenomena unless they result from a much more costly and disastrous event; instead, we should search for solutions that are within the range of our abilities and develop plans accordingly to resolve the climate change crisis.

Nevertheless, a non-rotating Earth would actually cause severe and undesirable consequences. Earth’s spin is responsible for generating the magnetic field that surrounds our planet, which provides us protection against the harmful ultraviolet radiation from the sun. Without the magnetic field, organisms would be bombarded with radiation and the atmosphere would be blown away by solar winds. As long as the Earth does not stop rotating, the prospect of a backward-spinning Earth allows scientists to explore the different aspects of our planet’s potential and reach a new level of understanding of Earth as a whole.