From the upright-walking Australopithecus afarensis to the Tik-Toking Zoomer, we all have one thing in common — we’re from Earth, the third rock from the sun. All recorded (and unrecorded) history has taken place on Earth’s surface, and our very bodies are molded to its particular blend of atmospheric gasses, its constant gravitational pull, and its temperature-perfect distance from the sun. These eight facts will make you appreciate the Earth more than ever, and maybe even make you feel a little bit of pride in being called an Earthling.
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.
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.
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.
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.
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 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.
Some 4.5 billion years ago, gravity attracted various space gasses 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.
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.