Since 1970, the annual Earth Day has been a time for us to reflect on the beautiful planet, the third from the sun, that we call home. Twenty years after that groundbreaking year, we received another impetus to ponder our planet when NASA’s Voyager 1 took a shot of the Earth at a distance of 3.7 billion miles. Our home suddenly became the “pale, blue dot” in the great cosmos.
Dr. Carl Sagan—astrochemist, astronomer and author of more than 600 scientific papers, popular articles and books—was responsible for that now iconic photo. A member of the Voyager Imaging Team, Dr. Sagan had the idea to ask NASA to command Voyager 1 to turn its camera around and take a photograph of Earth.
That vulnerable, fragile speck that we now know Earth to be has fascinated us since we first began to walk across its surface. And with good reason: in addition to being our home and the place where life as we know it originated, it remains the only planet we know of where life thrives.
Lately, the coronavirus pandemic has made me think about the Earth a little more. Perhaps we should have treated our planet with more kindness; tread more gently. Now seems like the right time to contemplate some truths about Earth. Below, are some of my favorites.
1. Earth is old
Researchers calculate the age of the Earth by dating both the oldest rocks on the planet and the meteorites that have been discovered here (meteorites and the Earth formed at the same time, when the solar system was dawning). The Earth is about 4.54 billion years old.
2. Earth is on the move
You may feel like you’re standing still, but you’re actually moving very fast. Depending on where you are on the globe, you could be spinning through space at more than 1,000 miles per hour. People on the equator move the fastest, while those located on the North or South Pole go the slowest. The effect is much like a basketball spinning on your finger: a random point on the ball’s equator has farther to go in a single spin than a spot near your finger. Thus, the point on the equator is moving faster.
In addition to this whirling, you’re also moving around the sun at 67,000 miles per hour.
3. Earth once had a supercontinent and one giant sea
The Earth’s continents are thought to have collided to become supercontinents and broken apart again several times in the planet’s 4.54-billion-year history. The most recent supercontinent was Pangaea, which began to split about 200 million years ago. The landmasses that comprised Pangaea eventually drifted into the current configuration of continents.
With one massive supercontinent, there was just one giant sea, which was called Panthalassa.
4. Earth’s magnetic north wanders
Geophysicists believe that Earth has a magnetic field because of the hot, liquid metal that sloshes around its solid iron core. This flow of liquid creates electric currents, which, in turn, generate a magnetic field.
Since the early 19th century, Earth’s magnetic north has been creeping northward by more than 600 miles, according to NASA scientists. The rate of this movement has increased to about 40 miles per year currently, compared with the 10 miles per year estimated in the 20th century. Earth’s magnetic field also varies in strength, and recently it was found to be weakening.
It’s the Earth’s magnetic field that causes compass needles to point north, no matter which way that you turn. However, the magnetic polarity of the Earth doesn’t always stay the same, and the magnetic field can flip—every 400,000 years or so. So far, such flips haven’t seemed to cause any harm to Earth’s life, and another one isn’t likely to happen for at least another 1,000 years. It’s guessed that when a flip does occur, compass needles will point in many different directions for a few centuries until everything settles down, and then compasses will point south instead of north.
5. Earth is highly electric
There are about 6,000 lightning flashes around the Earth every minute. A single stroke of lightning can heat the air to about 54,000 degrees Fahrenheit, causing the air to expand rapidly. That ballooning air creates a shock wave and ultimately a boom, better known as thunder.
6. Earth used to be purple
Ancient microbes may have used a molecule other than chlorophyll to harness the sun’s rays, one that gave the organisms a violet hue.
Some researchers think chlorophyll appeared after another light-sensitive molecule called retinal was already present on early Earth. Retinal, today found in the plum-colored membrane of a photosynthetic microbe called halobacteria, absorbs green light and reflects back red and violet light, the combination of which appears purple.
7. Earth rocks recycle
Earth’s rock cycle transforms igneous rocks to sedimentary rocks to metamorphic rocks and back again. The planet is constantly recycling its material through tectonic movements, which drag surface rocks back down below the surface to become magma and then spews them back out from volcanoes.
Although not a perfect circle, the cycle works like this: magma from deep within the Earth emerges and hardens into igneous rock. Tectonic processes then uplift that rock to the surface, where erosion shaves bits off. These tiny fragments get deposited and buried, and the pressure from above compacts them into sedimentary rocks, such as sandstone. If sedimentary rocks get buried even deeper, they “cook” under lots of pressure and heat into metamorphic rocks. If metamorphic rocks get caught in a subduction zone where one piece of crust is pushing under another, they may find themselves transformed back into magma.
8. Earth rocks can walk
Rocks can walk on Earth, and they do at the pancake-flat lake bed called Racetrack Playa in Death Valley. In some cases, rocks that weigh tens or hundreds of pounds have moved as far as 820 feet. These stone journeys have been blamed on everything from magnetic fields to space aliens to pranksters.
But in 2006, Ralph Lorenz, a NASA scientist investigating weather conditions on other planets, took an interest in the Death Valley rocks. He developed a kitchen-table model—using an ordinary plastic container—to show how the rocks may be gliding across the lake bed’s surface.
He took a small rock, put it in a piece of Tupperware and filled the container with an inch of water so that a bit of the rock stuck out. He then placed the container in a freezer, ending up with a small slab of ice with a rock embedded in it. He removed the ice-bound rock and placed it in a large tray of water with sand at the bottom. When he gently blew on the rock, it moved across the water, scraping a trail in the sand. He calculated that under certain winter conditions in Death Valley, enough ice and meltwater from the surrounding hills could form to float the rocks across the muddy bottom of Racetrack Playa in a light breeze, leaving a trail in the mud as the rocks moved.
9. Earth once had two moons
There is only one natural satellite of the planet Earth: the moon. As a percentage of the size of the body it orbits, the moon is the largest satellite of any planet in our solar system. In real terms, however, it is only the fifth largest natural satellite.
But Earth may once have had two moons. A tiny second moon—about 750 miles wide—may have orbited Earth before it catastrophically slammed into the other one. This clash may explain why the two sides of the surviving lunar satellite are so different from each other.
Our home planet also has two co-orbital satellites, asteroids called 3753 Cruithne and 2002 AA29. 3753 Cruithne is three miles in diameter and is sometimes called Earth’s current second moon. It doesn’t actually orbit the Earth but has a synchronized orbit with it that makes it look like it’s following us. In reality, it’s on its own, distinct path around the sun.
2002 AA29 is only 70 to 300 feet in diameter and makes a horseshoe orbit around the Earth that brings it close to the planet every 95 years. In about 600 years, it will appear to circle Earth in a quasi-satellite orbit. Scientists have suggested that it might make a good target for a space exploration mission.
10. Earth is covered in seas
The existence of our oceans is attributed to two sources. The first of these is the Earth itself. It is conjectured that large amounts of water vapor were trapped within the Earth during its formation. Over time, the planet’s geological mechanisms, primarily volcanic activity, released this water vapor into the atmosphere. There, it condensed and fell to the Earth as precipitation.
Today, oceans cover 70 percent of the Earth’s surface, yet humans have only explored about 5 percent, meaning that we’ve never seen 95 percent of our vast seas.
Ninety-seven percent of the water on Earth is saltwater; only 3 percent is fresh. Of that 3 percent, more than 2 percent is frozen in ice sheets and glaciers. Less than 1 percent of the freshwater is found in lakes, rivers and underground.
The Pacific Ocean is by far Earth’s largest ocean basin, covering an area of about 59 million square miles and containing more than half of the free water on Earth, according to the National Oceanic and Atmospheric Administration (NOAA). The Pacific is so big that all of the world’s continents could fit into it.
Due to the amount of water covering the Earth, it would be one of the brightest planets to look upon from a distance because the water would reflect the sun’s rays.
11. Earth has two tallest mountains
The tallest mountain on Earth is either Mount Everest, located in Nepal and Tibet, or Mauna Kea, an inactive volcano in Hawaii. The summit of Mount Everest is higher above sea level than the summit of any other mountain, extending about 29,029 feet. Mauna Kea’s summit is at 13,796 feet above sea level, but it extends about 19,700 below the Pacific Ocean. Therefore, according to NOAA, when measured from its true base deep beneath the water’s surface to its summit, Mauna Kea rises more than 33,496 feet, nearly a mile taller than Mount Everest.
12. Earth’s hottest spot is in Death Valley, California
The mercury in Death Valley, California, hit 134 degrees Fahrenheit on July 10, 1913, making it the hottest spot on Earth ever recorded, according to the World Meteorological Organization. The previous record of 136.4 degrees Fahrenheit, claimed by El Azizia, Libya, in 1922, was disqualified 90 years later. The organization noted that the measurement could have been off by as much as seven degrees due to the type of surface it was recorded on.
13. Earth’s coldest location is in Antarctica
You would expect that the coldest place on Earth would be found at one of the poles, but just how chilly it can get is astounding.
The lowest temperature ever recorded on Earth came from Russia’s Vostok Station in Antarctica, where the air plunged to a bone-chilling minus 128.6 degrees Fahrenheit on July 21,1983, according to the U.S. Geological Survey.
14. Earth’s driest spot is in the Atacama Desert
One-third of the Earth’s surface is either partially or totally desert. But the driest nonpolar spot on Earth is the Atacama Desert of Chile and Peru. In the center of this desert, there are places where rain has never been recorded.
15. Earth’s wettest place is in India
Mawsynram, a village in the East Khasi Hills district of Meghalaya State in northeastern India, is the wettest place in the world. Every year, this village is battered by more than 472 inches of rain.
The heavy rainfall is due to summer air currents that sweep over the steaming floodplains of Bangladesh, gathering moisture as they move north. When the resulting clouds hit the steep hills, they are squeezed through a narrow gap and compressed to the stage where they can no longer hold their moisture, causing near-constant rain.
Yet, this region is an exercise in extremes. December and January are the driest months in Mawsynram, when the rainfall can trickle down to around two inches.
16. Earth’s most-open-space place is in Greenland
If you like solitude, Greenland may your place. This autonomous territory boasts the least population density of any on Earth. As of 2020, 56,081 people lived in 836,300 square miles of elbow room. However, most of the settlements in Greenland are clustered on the coast, so the number is somewhat misleading.
17. Earth’s largest terrestrial organism by area is a fungus
Naming the largest organisms now found on Earth is a bit tricky, as they can be determined according to various aspects of an organism’s size, such as area, height, length, mass or even genome size, the total amount of DNA contained within one copy of a single complete genome.
However, when it comes to largest terrestrial organism, scientists now say that it is a fungus called Armillaria solidipes, or the honey fungus. In 1992, researchers reporting in the science journal Nature revealed a honey fungus that spans 2,200 acres (almost four square miles) in the Malheur National Forest in Oregon.
One note: the Great Barrier Reef is the world’s largest structure composed of living entities, stretching 1,200 miles, but it contains many organisms of many types of species
18. Earth’s largest terrestrial organism by mass is trees
If we measure organisms by mass and if we consider clonal colonies as being singular entities, the prize for largest would go to Pando, a clonal colony of quaking aspen trees, located in the Fishlake National Forest at the western edge of the Colorado Plateau in south-central Utah.
Pando occupies 106 acres and is estimated to weigh collectively 6,600 tons, making it the heaviest known organism. The root system of Pando, at an estimated 80,000 years old, is among the oldest known living organisms.
Pando is also thought to be dying. Though the exact reasons are not known, they may include drought, grazing, human development and fire suppression.
But even if such clonal colonies are excluded, trees retain their dominance in this category, with the giant sequoia being the most massive tree. One in particular, the General Sherman giant sequoia, is the largest known tree by volume on the planet. General Sherman’s trunk contains slightly more than 52,500 cubic feet of material.
19. Earth’s largest animal is a blue whale
The blue whale is thought to be the largest animal ever to have lived. The maximum recorded weight was 190 tons for a blue whale measuring 91 feet; but longer blue whales, up to 110 feet, have been recorded but not weighed.
The African savanna elephant (or African bush elephant) is the largest living land animal. A native of various open habitats in sub-Saharan Africa, this pachyderm is commonly born weighing about 220 pounds. According to the 2008 book titled Animal Records from the London, England, Natural History Museum, the largest elephant ever recorded was shot in Angola in 1974. It was a male measuring 35 feet from trunk to tail and 13.7 feet lying on its side in a projected line from the highest point of the shoulder to the base of the forefoot, indicating a standing shoulder height of 13 feet. He had a computed weight of 12.25 tons.
The title of longest noncolonial animal is probably owned by the lion’s mane jellyfish. One had tentacles that reached 120 feet.
20. Earth has more viruses than there are stars in the universe
Earth is teeming with viruses. There are an estimated 10 nonillion (a number equal to 1 followed by 30 zeros) individual viruses on the planet—enough to assign one to every star in the universe 100 million times over.
21. Earth is awash with snow crystals
As a person who likes the cold, this is another of my favorite Earth facts. Each winter, about 1 septillion (1 followed by 24 zeros, or a trillion trillion) snow crystals drop from the sky.
22. Earth’s Route 66 is longer than the distance to the Earth’s core
Those who are fans of road trips will like this fact.
“The boundary between Earth’s mantle and core is roughly 1,864 miles below our feet—a little less than the total length of America’s ‘Mother Road’, Route 66,” seismologist Jennifer Jackson of Caltech once told Popular Mechanics magazine. Route 66 is 2,448 miles long.
23. Earth’s first ozone hole is still healing
The Earth has an ozone layer which protects it from harmful solar radiation. This shell is a special type of oxygen that absorbs most of the sun’s powerful ultraviolet rays.
Scientists discovered the first hole in the ozone layer—located directly above Antarctica—in 1985. The Montreal Protocol of 1987 was the first plan approved by every country in the United Nations to focus on the restriction of chlorofluorocarbons (CFCs that emitted ozone-destroying chlorines).
In 2017, NASA announced that the ozone hole was the weakest since 1988 because of warm stratospheric conditions. In 2018, a United Nations report announced it is expected to recover in the 2060s.
24. Earth’s skies dazzle with dancing lights
Earth’s magnetic field (see no. 4, above) shields us from high-energy particles launched at us from the sun and from elsewhere in the cosmos. But due to the field’s structure, some particles get funneled to Earth’s poles and collide with our atmosphere, yielding auroras, the natural fireworks known by some as the northern lights (or aurora borealis) and the southern lights (or aurora australis).
25. Earth’s naming remains a mystery
It’s believed that the name Earth is around 1,000 years old. Our planet is the only one in our solar system not to be named after a Greek or Roman deity. Although only Mars, Mercury, Jupiter, Saturn and Venus were named during ancient times—because they were visible to the naked eye—the Roman method of naming planets was retained after the discovery of Neptune and Uranus.
One idea of the source of the name is that the word Earth is an old Germanic word (erde) that means “the ground.” Another thought is that Earth is derived from the Old English word eor(th)e/ertha, as well as the Anglo-Saxon word erda, which means “ground” or “soil.”
But the handle’s creator is unknown.
Earth also has a nickname. When astronauts first went into space, they looked back at the Earth with human eyes for the first time. Seeing 70 percent of the globe covered in oceans (see no. 10), they called our home “the Blue Planet.”
Pale, blue dot
Dr. Carl Sagon wrote a beautiful elegy to Earth after seeing the Voyager I image. He penned:
“Look again at that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every ‘superstar,’ every ‘supreme leader,’ every saint and sinner in the history of our species lived there—on a mote of dust suspended in a sunbeam.
“The Earth is a very small stage in a vast cosmic arena. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot.
“Our posturings, our imagined self-importance, the delusion that we have some privileged position in the universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves.
“The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.
“It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we’ve ever known.”
Here’s to finding your true places and natural habitats,