What If the Earth Rotated Backwards?

What If the Earth Rotated Backwards?

Since Earth formed about four-and-a-half billion years ago, it has been rotating in one direction – eastward, or counter-clockwise. This fundamental fact is called prograde motion, which means that the Earth spins in the same direction as the sun. Most satellites have a prograde motion around their planets, and most planets have prograde motions around their suns. The only exceptions in our solar system are Venus and Uranus, which spin in the opposite direction, AKA retrograde motion. But the Earth’s prograde preference has always stood. It spins the way it does because that’s the way space made it.

So, what would happen if our planet one day decided to transfer to the retrograde team – an unprecedented switch after four-and-a-half billion years – and spin in the opposite direction?

The good news is that it wouldn’t create total catastrophe (and no, we wouldn’t go back in time like “Superman”). The first and most obvious effect would be the changing sunrise and sunset. Instead of rising in the east and setting in the west, the sun would now rise in the west and set in the east. Weird, right? Assuming that the spin speed of the Earth wouldn’t be affected though, complete rotations would still take 24 hours – so, our days wouldn’t be longer, and our concept of time would not be affected. However, the switching sunsets thing would likely take a long time to get used to!

While on the subject of things that wouldn’t really change; our seasons would stick around for the most part, too. Despite Earth’s retrograde rethink, it would still orbit the sun in the same way. So, as our seasons are dependent on the Earth’s orbit around its star, they’d play out pretty much the same as they do now. Summer still follows Spring. Spring still follows Winter. And so on.

However, that’s about all that would remain unchanged. Everything else would be totally flipped upside down.

First off, the Earth’s spin sets off its Coriolis Force, which dictates its jet streams, which determine global climates and temperatures. On Earth as we know it, these jet streams are used by meteorologists to explain those pesky cold snaps that can make modern winters feel so unbearably cold. And they’re predominantly westerly, meaning they flow from west to east.

The Earth’s rotation also directly influences the trade winds. These are easterly winds found primarily in the tropics. These winds are usually responsible for when and where tropical storms strike on land, as they appear to ‘push’ them across the globe. For example, storms that form over the Atlantic Ocean are blown from the northeast into North America. Trade winds also wield a huge influence on climates around the equator, as they can remove humidity (resulting in desert regions) and provide constant humidity (resulting in rainforests).

Clearly, an Earth that started spinning in the opposite direction would wreak havoc on these natural weather systems that are so dependent on a prograde motion. In fact, it could completely alter our planet’s topography, bringing different ocean and air currents, which in turn would affect the climates and ecosystems on our existing continents. For one thing, a retrograde Earth would potentially be much greener. In a 2018 Max Planck Institute simulation that tested this exact hypothetical scenario, researchers found that desert coverage shrank by about four million square miles – to just 12 million square miles in total. Furthermore, the simulation predicted that the Sahara Desert would likely become lush and green due to massive amounts of precipitation, while never-before-seen deserts could develop in some other areas of Brazil, Argentina, and the United States. And those changes would be mostly down to the shifting jet streams and trade winds.

Similar developments would likely result in bitterly cold winters for Europe, too. While Britain can certainly feel fresh today, thanks to jet streams pushing in from eastern Canada, its climate would become drastically colder should regular Siberian winds set in. In fact, while much of Europe enjoys a relatively warm and humid climate today, the increased winds coming in from northern Russia would gradually turn it into a cold, snowy and shivery landscape for most of the year.

A retrograde Earth would also affect the ocean currents. And these changes would primarily affect coastal cities. For example, the Max Planck Institute sim also predicted that Eastern Russia would be warmer should Earth’s rotation switch, thanks to the development of a new heat-carrying ocean current headed its way. As the currents reverse, seas would theoretically warm eastern coasts and cool western regions. So, it’s entirely possible that cool, wet areas like Maine would heat up, whereas the average temperatures in California would drop. Los Angeles would become the new New York, and vice versa.

The simulation also found that altered ocean currents would potentially result in a rise of cyanobacteria, covering large parts of the Indian Ocean. A type of bacteria found in water, Cyanobacteria feeds on sunlight and looks a little like algae. Seeing as some forms of it also produce cyanotoxins – which can prove extremely damaging to a person’s skin, nervous system, and liver – this particular development could be bad for human health, leading to evacuations from some coastal settlements.

With all of this considered, clearly it wouldn’t just be the literal landscapes that would drastically alter. In just a few centuries, Earth would also have an entirely different economy. The altered trade winds could directly affect actual trade links – even if standard shipping methods change over time. Towns, cities and entire countries would develop completely different climates, resulting in the production of different trading goods and the provision of different services. For example, areas known for wine cultivation like Italy, France, and Spain would suddenly find themselves without their chief export, as their now-freezing weather patterns wouldn’t bring the desired conditions for a rich bottle of red. Similarly, beach resorts built on tourist industries would likely no longer entice visitors with their now lower-than-average daily temperatures. Throw into the confusion that other unknown issues similar to the cyanotoxins mentioned earlier could result in effective no-go zones, and it’s easy to see how a mass migration could unfold, with people wanting to live and work elsewhere.

It wouldn’t just be humans, either. All sorts of established ecosystems would also be turned upside down, with thousands of animal species either moving themselves or else needing to be relocated by conservation experts. The same goes for the planet’s plant life; it’d have to somehow move with the changing climate, or else die out. With desert animals thrown into rainforest conditions, and tropical creatures cast out into dust lands, even a gradual shift would spell trouble and would likely lead to mass extinctions.

Clearly, a backwards-rotating Earth would be a completely different Earth. Entire climates would be altered, established weather patterns would collapse, and long-held landscapes would be irretrievably lost. These changes would result in radically different trade links, as entire economies (and probably entire cultures) would have no choice but to adapt. From global cities to specific ecosystems, we’d see mass migrations of all Earthly species, to try and counteract the monumental shift.

It’s perhaps something we don’t often ponder, but the Earth’s rotation is integral to how we live our lives today, how we lived in the past, and how we would live in the future.