The Earth Isn’t a Perfect Sphere

If you had to make a model of the solar system in an elementary science class, your nine planets (or eight, depending on your age) were likely perfect foam spheres. While that’s a pretty good approximation, it’s not entirely accurate. The Earth is actually an irregularly shaped ellipsoid — its middle bulges due to the centrifugal force of its constant rotation. Scientists have determined that the Earth’s sea level is actually about 13 miles farther from its center at the equator than at the poles. Plus, the Earth’s shape is constantly changing.

One Day on Earth Wasn’t Always 24 Hours Long

When Homo sapiens began walking the Earth some 400,000 years ago, a day was basically 24 hours long — but that hasn’t always been the case. Scientists from Kyoto University estimate that when the moon first formed a few billion years ago, it spun around the Earth at a much closer distance than it does today, which affected the Earth’s own rotation. By their calculations, when life first appeared 3.6 billion years ago, an Earth day (one full rotation of the planet) was only 12 hours long. As the moon slowly distanced itself from Earth, the days grew longer, lasting 18 hours around the emergence of photosynthesis and 23 hours when multicellular life first took form. Research in 2021 discovered that the Earth is now spinning ever-so-slightly faster than it was 50 years ago, a major headache for physicists, astronomers, and computer programmers everywhere.

Earth May Have Once Been a Giant Snowball

The Earth has experienced plenty of ice ages throughout its existence, with the most recent reaching its apex 20,000 years ago. But none of these world-changing cold snaps were quite like the Cryogenian Period, when some scientists believe the Earth froze over to the point where there was ice near the equator, a phenomenon known as “Snowball Earth.” Studies have shown that during this period Earth experienced a runaway temperature effect as ice sheets reflected sunlight before it could warm the ground, which in turn created more ice … which in turn created more surface area to reflect incoming sunlight.

100 Lightning Bolts Strike Earth Every Second on Average

The Earth’s atmosphere is filled with electricity. Every second, 100 cloud-to-ground lightning strikes hit the Earth. Considering that most lightning only takes place in clouds and never hits the ground, that makes the Earth quite an electrifying place. Lightning happens because air in clouds acts as an insulator between positive and negative charges that exist within clouds and between clouds and the ground. When these opposite charges build up enough, the air can no longer insulate and breaks down — a phenomenon we experience as lightning. To add even more drama, lightning traveling at 200,000,000 mph superheats the surrounding air to 50,000 degrees Fahrenheit — that’s nearly five times hotter than the surface of the sun — but only for a fraction of a second. This intense heat causes air to expand and vibrate, creating thunder. But while lightning is indeed common, only one out of every 5,000 Americans will be struck by it during their lifetime.

The Earth’s Surface Is “Recycled” Every 500 Million Years

Approximately every 27 days, humans replace their skin, and the Earth undergoes a similar process — it just takes 500 million years. As tectonic plates ram into each other, creating what’s called subduction zones (the Ring of Fire volcanic chain, for example, is a series of subduction zones bordering the Pacific Plate), the plates dip below lighter continental plates. The subducted rock is heated into magma and becomes future lava plumes forming new land masses. Scientists used to believe that this process took nearly 2 billion years to complete, but new analysis of basaltic lava on Mauna Loa volcano in Hawaii proves that Earth recycles its “skin” in about a quarter of that time, or every 500 million years.

The Earth’s Core Is as Hot as the Sun’s Surface

The core of the Earth contains two parts. First is the inner core, essentially a dense ball of iron with a radius of 758 miles that’s under incredible pressures of 3.6 million atmospheres — about 360 million times more pressure than on the Earth’s surface. Although the temperature far exceeds the heat required to turn iron into molten goo, this intense pressure keeps the iron from melting. Second is the liquid outer core, which separates the inner core from the mantle. Using x-rays to determine the melting point of iron at various atmospheric pressures, scientists discovered that the boundary between the inner and outer cores is in the ballpark of 10,800 degrees Fahrenheit — a little hotter than the surface of the sun. Of course, comparing core to core, the sun scorches the competition at 27 million degrees Fahrenheit, making the Earth’s core feel comparatively temperate.

The Earth Is 10,000 Times Older Than Humans

Some 4.5 billion years ago, gravity attracted various space gases and dust to form the Earth, kickstarting the Hadean eon. This eon is fittingly named after Hades, the Greek god of the underworld, because of the hellish 600 million years of hard work required to form the Earth’s crust. From there, it took another 300 million for microbial life to show up, another 3.2 billion years for life to take off thanks to the Cambrian explosion, and yet another 525 million years or so for a particular ape-like species to walk upright. A few million years after this ancient ancestor, the first modern humans began populating the planet some 400,000 years ago. All told, that makes Earth more than 10,000 times older than humans.

The Remnants of an Ancient Planet Might Be Buried Inside the Earth

The Earth’s birth some 4.6 billion years ago was a pretty raucous one. Scientists refer to Earth’s first 600 million years as the “Hadean Eon,” a reference to the fact that the planet was little more than a quagmire of molten rock at the time. During this stretch of years, the Earth was also constantly bombarded by planetesimals (small bodies of rock or ice) that existed in the sun’s protoplanetary disk — a dense field of gas, dust, and rock that orbits newly formed stars. One of the biggest of these celestial bodies was a Mars-sized protoplanet named Theia, which scientists theorize smashed into Earth only 30 million to 100 million years after the solar system’s formation. The resulting collision was so cataclysmic that the debris ejected into space formed Earth’s moon (possibly in a matter of hours). In 2021, a geologic survey uncovered mysterious rocks at the base of the planet’s mantle, suggesting that remnants of this ancient run-in might still be found within the Earth itself.

The Driest Place on Earth Hasn’t Seen Rain for 2 Million Years

Today, impressive deserts like the Sahara, Mojave, Atacama, and Gobi dot Earth’s surface — but none compares to the McMurdo Dry Valleys. Named after Scottish polar explorer Archibald McMurdo, this impressively dry landscape is found in Antarctica, which is technically the largest desert in the world due to its immensely arid conditions and lack of liquid water. But even in this punishing environment, the McMurdo Dry Valleys stand alone, as they haven’t seen a drop of rain in more than 2 million years. Yes, million.

This extreme dryness is because of a meteorological phenomenon known as katabatic winds, which pull heavy, moisture-filled air down and away from these particular valleys. This creates an incredibly dry landscape filled with mostly rocks and photosynthetic bacteria. Because of these parched conditions, scientists consider the McMurdo Dry Valleys the closest imitation of the Martian surface found on Earth.

Certain Areas of Earth Experience Gravity Differently

From our perspective on Earth, gravity feels like an indelible constant. However, gravity is just a calculation between mass and distance, so once you leave the familiar cosmological confines of Earth, gravity can vary widely from planet to planet, star to star, or basically anything with significant amounts of mass. But you don’t have to leave Earth to experience this for yourself. The Hudson Bay region in northeastern Canada experiences some of the weakest levels of gravity on Earth. This doesn’t mean Canadians are moonwalking their way to the grocery store, but residents of the area do weigh one-tenth of an ounce less than they would if they lived elsewhere.

This gravitational anomaly actually has two causes. The first is what’s known as mantle convection, when super-hot magma moves continuously under the Earth’s crust in a circular motion, causing certain areas to sink slightly. One of these sinking regions, which are known as subduction zones, occurs directly beneath the Hudson Bay region, which makes up for more than half of the area’s “missing gravity.”

The other cause dates back to the last ice age. As massive, 2-mile-thick ice sheets retreated from what is now Hudson Bay, they left giant impressions of condensed rock in their wake (causing less mass). Scientists say gravity is slowly returning to normal levels in Hudson Bay as the rock rebounds at about half-an-inch per year, but residents still have 5,000 years or so to experience their gravity-induced weight loss.

The Highest Point From the Earth’s Center Isn’t Everest

What is the world’s tallest mountain? The answer is actually deviously complicated. Most people likely think it’s Sagarmatha, otherwise known as Mount Everest, and in a way, they’re not wrong. At 29,032 feet tall, the Himalayan giant is the highest point above global mean sea level. But then there’s Hawaii’s Mauna Kea, a mountain that stands some ​​33,500 feet but with more than half of its rocky stature hidden below the surface of the Pacific. And there is a third contender, and it's a mountain that few people could even point out on a map. Ecuador’s Mount Chimborazo isn’t anything special — in fact, it’s only the 39th tallest peak in the Andes. But Chimborazo has a secret geographic advantage in the form of Earth’s equatorial bulge. The Earth isn’t a perfect sphere (see above) and because of its natural centrifugal bulge around its waistline, this relatively inconspicuous mountain is actually the highest terrestrial point from the center of the Earth — a full 2,072 meters (nearly 6,800 feet) higher than its Himalayan competition.

Pangea Is Only the Latest of Many Past Supercontinents

Look at a world map today, and the continents appear like pieces belonging to an ancient puzzle long disassembled — and that’s basically true. Starting some 200 million years ago, the supercontinent known as Pangea (surrounded by a global ocean called Panthalassa) began to break apart until this slow but steady dance concluded with the seven distinct continents we know today. However, Pangea is really only the latest supercontinent in Earth’s history. In fact, the Earth’s landmasses have been crashing into one another, separating, and crashing into one another again basically since the Earth’s formation. Previous supercontinents include Gondwana and Laurasia, which actually collided to form Pangea in the first place, as well as Pannotia, Rodinia, and Nuna, to name only a few. Just as Pangea isn’t the only supercontinent in Earth’s history, it also won’t be the last. In 200 million years, the Earth will form a new supercontinent, which scientists call Amasia (a portmanteau of America and Asia) as the Pacific Ocean continues to shrink about an inch every year, making the slow continental collision inevitable.

Antarctica Used To Be as Warm as Italy

While Earth has certainly experienced some cold moments (see above), it’s run a fever more than a couple of times. One of those hot spells came during the Cretaceous Period some 90 million years ago, which made the icy snowscape we know as Antarctica a temperate rainforest filled with dino fauna and hothouse flora. Much like today’s anthropogenic climate change, Earth was so warm back in the dino days because of increased carbon dioxide levels, likely originating from massive outpourings of lava around the globe. During this time, sea surface temperatures in the tropics were nearly hot-tub hot at 95 degrees Fahrenheit, and Antarctica enjoyed a climate similar to that of modern Italy. Although Antarctica began cooling after hitting this high temperature mark, it still hosted life well into the Eocene Epoch (55 million to 34 million years ago) and even served as a land bridge for ancient marsupials to migrate from South America into modern-day Australia.

The Earth Is Only One Out of Trillions of Planets in the Milky Way…

The Earth is an incredible place filled with millions of fascinating animals, amazing biomes, and awe-inspiring landscapes, but it’s just one pale blue dot among a sea of planets spread across the Milky Way. By some estimates, our galaxy contains trillions of planets orbiting at least 100 billion stars (not to mention the estimated trillions of rogue planets that are wandering the galaxy without a host star). Despite this estimated abundance of planets, scientists have only confirmed the existence of little more than 5,000 or so exoplanets, a large portion of which are roughly the same size as Earth. The closest of these Earth-like candidates is Proxima Centauri B, which is located only 4 light-years away (or about 24 trillion miles). Although this planet is about 1.27 times as massive as our Earth, its orbital period is only 11 days and its surface is likely bathed in the UV radiation from its red dwarf star, making Earth’s closest exoplanet neighbor a poor candidate for supporting life.

Earth Is the Only Known Planet That Supports Life

Maybe the most amazing fact about Earth is that it’s the only planet we know that supports life at all. A lot of things had to go right for this to be possible. For one, it’s perfectly distanced from the sun in what scientists call “the Goldilocks zone,” because it’s not too hot but also not too cold (most life has a tough time living in temperature extremes). The Earth is also protected from solar radiation thanks to its magnetic field, and kept warm by an insulating blanket we call the atmosphere. And most importantly, it has the right building blocks for life — mainly water and carbon.

While this is Earth’s most distinguishing feature among all the known planets, moons, and exoplanets, it might not always be an outlier. Scientists have classified some exoplanets as “superhabitable,” meaning they have conditions greater than Earth’s for supporting life. Even places like Enceladus, a moon of Saturn, or Europa, a moon of Jupiter, could possibly be hiding life somewhere on its surface or in its oceans. For now, Earth is the lone world teeming with life that we know of — and we couldn’t ask for a better one.