8 Things You Need to Know About Earth

It's probably best that we don't think too much about the Earth. After all, it's a tiny orb spinning more than 1000 mph at the equator while simultaneously zipping through space at 67,000 miles per hour. It circles a mysterious, 10,000°F fusion reactor that's more than 100 times its size, and spends most of its orbit narrowly (in a cosmic sense) avoiding collisions with giant chunks of rock that could practically wipe its surface clean. But if you're feeling brave, here are a few things you might not know about Earth. Mental Floss spoke to Josh Willis, a climate scientist at NASA's Jet Propulsion Laboratory, about the planet we call home.


The Earth orbits the Sun at approximately 93 million miles. As you probably know, at this distance it takes one year for the Earth to complete a revolution, and 24 hours to complete one rotation. The surface of the Earth has temperatures ranging from -126°F to 136°F. The planet is about 7900 miles in diameter (though the deepest we've ever drilled is 7.6 miles). There are 332,519,000 cubic miles of water on the planet, which is enough that, if the water broke from the Earth and organized itself into a sphere, it would have a diameter of 860 miles—about 40 percent that of the Moon.


The first photograph of Earth from space was taken in 1946. It's a grainy, black-and-white shot of a tiny slice of our world, curved with the ink of space as a backdrop. In 1960, weather satellites began sending photographs back to Earth, images that were still hideously deformed but scientifically valuable, especially for meteorologists, who now had stunning views of cloud systems from which to work. NASA's ATS-III satellite in 1967 returned the first color images of the full Earth. Now at last, we could see our living world, ringed in space and wrapped in billowing clouds.

On Christmas Eve, 1968, Apollo 8 astronaut William Anders sent back "Earthrise," a now-iconic photograph of a fragile cerulean orb rising over the lunar surface. But the most famous photograph of the Earth, by far, was taken about four years later, on December 7, 1972: the "Blue Marble." You've probably seen it countless times, enough that when you think of the Earth, that's what you think of. You may be less familiar with how astronaut Harrison Schmitt described the sight to Mission Control: "I'll tell you, if there ever was a fragile-appearing piece of blue in space, it's the Earth right now."


The Earth is the first planet, moving outward from the Sun, that possesses a moon. We call our moon "The Moon" (which will be a real headache centuries from now, when we've colonized the solar system). Every 27.32 days, the Moon completes an orbit of the Earth, which is why it has phases. When the Earth is between the Sun and the Moon, we see the Moon in full illumination (a round orb). As it circles the Earth, less and less of its visible surface is illuminated, until at last the Moon is between the Sun and the Earth. At that point, the "far side" of the Moon is in full illumination, and from our perspective, the Moon is receiving no light at all. The cycle then repeats itself, with more of its disc being illuminated as the month elapses, until it is again full. Because the length of the Moon's orbit is just shy of a month, every so often a month (which, itself, derives from the word "moon") has two full Moons, the second of which is colloquially called a Blue Moon.

The moon does spin, but in synchronous rotation with the Earth. In other words, it spins at the same speed as its orbit. As a result, the Earth only ever gets to see one side of our only natural satellite. The best guess for the origin of the Moon involves an object the size of Mars smashing into the Earth 4.5 billion years ago, sending debris into space. This debris organized itself into a molten form of the alabaster orb we know and love. Within 100 million years, an early crust had begun to form. Today, the Moon influences the tides of the ocean and eases our axial wobble, keeping things (more or less) nice and stable—a perfect condition for life.


When it comes to life, there are a lot of maybes in the solar system. Maybe Mars supported life billions of years ago. Maybe Europa is teeming with life today. The problem is that there is no evidence anywhere of anything that wiggles, walks, or swims … except for one place. Earth is the only body in the universe known to harbor life. And it has been tough going! Four billion years ago, the Earth's surface was sterilized during the Late Heavy Bombardment, when asteroids pilloried the inner solar system. To get some idea of what things must have been like during the LHB, look at the Moon. Most of its craters were formed during that time. Life survived on Earth in large part thanks to the hydrothermal vents at the bottom of the ocean.

There have been five mass extinctions on Earth, the worst of which (the Permian-Triassic, or "P-T Event") was 250 million years ago, wiping out 96 percent of sea species and nearly three-quarters of land vertebrates. Sixty-six million years ago, the Chicxulub impact wiped out 75 percent of all life, and ended the reign of the dinosaurs. Things recovered nicely, though, and today, biologists think there are 8.7 million species of life on Earth. That's not bad considering the universe's apparent hostility to life, and makes what we have going here all the more special and worth preserving. And we'd better get on it: Many scientists argue that we're in the midst of a sixth mass extinction—and we can only partially blame it on cats.


"Global warming is real, it's caused by people, and it's a big problem," Willis told Mental Floss. "Every year the impacts of human-caused climate change get bigger and bigger, and are felt more and more across the planet." We feel the effects of climate change today, but the worst is yet to come, both in terms of economic and social disruption. "Right now we have a choice about what kind of planet we want to have in the future. And the choice is: Do we want to continue to burn fossil fuels and heat up the Earth, or do we want to try and stabilize our climate and keep it more or less like we've had it for the last 10,000 years?"


Carl Sagan once observed that, to scale, the Earth's atmosphere is about as thick as the gloss coating on a globe. Our oceans, meanwhile, make Earth the only known planet with stable water at its surface. (Icy moons like Europa and Enceladus have subsurface oceans of liquid water, and Titan, in addition to a possible subsurface ocean of water, has vast lakes of liquid methane covering its surface.)

The problem is, we're causing those water levels to rise. NASA's Jason-3 spacecraft measures the height of the ocean with 1-inch accuracy. Every 10 days, it collects data on the entire ocean, revealing details about such things as ocean currents and how they change, tilts in the ocean's surface, and the average volume of the ocean. "The oceans are growing for two reasons," says Willis. "One is because they absorb heat trapped by the greenhouse gases, and the other is that the ice in places like Greenland and Antarctica and tiny glaciers all across the planet are all melting and adding extra water to the oceans. And so this satellite measures these things combined, and in a way it's really taking the pulse of our planet."

A decade ago, the ice sheets in Greenland and Antarctica were thought of as stable. They are the last remaining ice sheets that cover huge land masses, and today they are disappearing. In 50 years, their melting will be the dominant source of global sea level rise. "Every time a big discovery is made," says Willis, "it seems like the picture is worse than we thought it was. The possibility for really rapid ice loss and rapid sea level rise is greater than we thought."


The oceans remain a giant unknown for scientists. Knowing more about them would answer many of our questions about life and the life of the Earth. "Two-thirds of the planet is covered with water, and you can't see through it. And you can't shoot microwaves through it, and radio waves, and all the other kinds of things that we use even to measure other planets," Willis says. "If you probe the ocean, there are still a lot of big mysteries down there."

To understand how oceans really work would explain, for example, where the heat from global warming is going. Though the oceans absorb 95 percent of the heat trapped by greenhouse gases, it's still a mystery where that heat energy actually goes. Similar questions exist as to how the oceans interact with ice sheets.

Considering the stakes, it seems like an intense study of the Earth and its oceans is in order. And yet the same people who claim there isn't enough evidence to explain climate change want to slash the budgets of missions designed to find the requested evidence. Among the missions set to be killed are the PACE satellite, over a decade in development and designed to study the interaction of the ocean and the atmosphere, and the CLARREO pathfinder mission, which would cut the time necessary to predict climate change in half. (An extra 20 years to prepare for climate change would save the world $10 trillion.)


But it will take a concerted effort to change our behavior—before it's too late. "We think of global warming as something that happens in our cities, and it is happening there, but really 95 percent of the heat that's being trapped is going in the oceans. And I don't think people realize that. It just seems like, well, we're getting the brunt of global warming here in Los Angeles—but that's not true, really. It's the sea life and the oceans that are getting the brunt of the change," says Willis.

"One thing we should keep in mind is that all hope is not lost," he continues. "We are beginning to see changes in our economy, we're beginning to see the growth of renewable energy, and the strong desire to move to a fuel source that doesn't cook us, and I think that's a good thing. A lot of it happens at local and state levels now, but it's beginning to have an impact for real around the world."

July Is the Best Time to See Saturn and Its Rings This Year

NASA/JPL/Space Science Institute
NASA/JPL/Space Science Institute

Saturn is the second-biggest planet in our solar system, boasting 95 times the mass of Earth. Even though it's located hundreds of millions of miles away, Saturn is still clearly visible in the night sky during certain times of the year. As EarthSky reports, July is the best month to spot the gas giant, and if you're using a telescope, you may even see its rings and its largest moon.

On July 9, 2019, Saturn entered something called opposition with Earth. This occurs when our planet falls directly in line between Saturn and the Sun. When it's in opposition, Saturn is at its closest point to Earth in its orbit (about 746 million miles away). Due to its position in relation to our planet and the Sun, Saturn also appears especially clear and bright.

Just because opposition has passed doesn't mean your chance to spot Saturn from your backyard is over. The planet may no longer be at peak visibility, but during the weeks and even months surrounding opposition, Saturn will still be close to Earth and easily observable with the naked eye. Without any special tools, Saturn will appear as a bright golden star. If you're using a telescope, look for the planet's iconic rings. Titan, the largest of its 62 moons, may also be visible through a telescope.

To catch a prime view of Saturn, look up on a clear night any time from now through September 2019. At sunset, look above the southeastern sky for white-yellow star. Saturn will appear in the southern part of the sky in the middle of the night and disappear over the northwest horizon at sunrise. Saturn's opposition comes just one month after Jupiter's, which means the solar system's largest planet also looks particularly big and bright this time of year.

[h/t EarthSky]

8 Facts About David Bowie's 'Space Oddity'

Express/Express/Getty Images
Express/Express/Getty Images

Fifty years ago, on July 24, 1969, astronauts walked on the Moon for the first time. Just a few weeks earlier, another space-age event had rocked the world: David Bowie’s single “Space Oddity” hit airwaves. The song, whose lyrics tell the story of an astronaut’s doomed journey into space, helped propel the artist to icon status, and five decades later, it’s still one of his most popular works. In honor of its 50th anniversary, here are some facts about the stellar track.

1. "Space Oddity" was inspired by 2001: A Space Odyssey.

Many listeners assumed that "Space Oddity" was riffing on the Apollo 11 Moon landing of 1969, but it was actually inspired by a Stanley Kubrick film released a year earlier. Bowie watched 2001: A Space Odyssey multiple times when it premiered in theaters in 1968. “It was the sense of isolation I related to,” Bowie told Classic Rock in 2012. “I found the whole thing amazing. I was out of my gourd, very stoned when I went to see it—several times—and it was really a revelation to me. It got the song flowing.”

2. "Space Oddity" was also inspired by heartbreak.

The track was also partly inspired by the more universal experience of heartbreak. Bowie wrote the song after ending his relationship with actress Hermione Farthingale. The break inspired several songs, including “Letter to Hermione” and “Life on Mars,” and in “Space Oddity,” Bowie’s post-breakup loneliness and melancholy is especially apparent.

3. "Space Oddity" helped him sign a record deal.

In 1969, a few years into David Bowie’s career, the musician recorded a demo tape with plans to use it to land a deal with Mercury Records. That tape featured an early iteration of “Space Oddity,” and based on the demo, Mercury signed him for a one-album deal. But the song failed to win over one producer. Tony Visconti, who produced Bowie’s self-titled 1969 album, thought the song was a cheap attempt to cash in on the Apollo 11 mission, and he tapped someone else to produce that particular single.

4. The BBC played "Space Oddity" during the Moon landing.

"Space Oddity" was released on July 11, 1969—just five days before NASA launched Apollo 11. The song doesn’t exactly sound like promotional material for the mission. It ends on a somber note, with Major Tom "floating in a tin can" through space. But the timing and general subject matter were too perfect for the BBC to resist. The network played the track over footage of the Moon landing. Bowie later remarked upon the situation, saying, "Obviously, some BBC official said, 'Oh, right then, that space song, Major Tom, blah blah blah, that’ll be great. 'Um, but he gets stranded in space, sir.' Nobody had the heart to tell the producer that."

5. David Bowie recorded an Italian version of "Space Oddity."

The same year "Space Oddity" was released, a different version David Bowie recorded with Italian lyrics was played by radio stations in Italy. Instead of directly translating the English words, the Italian songwriter Mogul was hired to write new lyrics practically from scratch. "Ragazzo Solo, Ragazza Sola" ("Lonely Boy, Lonely Girl") is a straightforward love song, and Major Tom is never mentioned.

6. Major Tom appeared in future songs.

Major Tom, the fictional astronaut at the center of "Space Oddity," is one of the most iconic characters invented for a pop song. It took a decade for him to resurface in David Bowie’s discography. In his 1980 single "Ashes to Ashes," the artists presents a different version of the character, singing: "We know Major Tom's a junkie/Strung out in heaven's high/Hitting an all-time low." Bowie also references Major Tom in "Hallo Spaceboy" from the 1995 album Outside.

7. "Space Oddity" is featured in Chris Hadfield's ISS music video.

When choosing a song for the first music filmed in space, Canadian astronaut Chris Hadfield naturally went with David Bowie’s out-of-this-world anthem. The video above was recorded on the International Space Station in 2013, with Hadfield playing guitar and singing from space and other performers providing musical accompaniment from Earth. Some lyrics were tweaked for the cover. Hadfield mentions the "Soyuz hatch" of the capsule that would eventually shuttle him to Earth.

8. "Space Oddity" played on the Tesla that Elon Musk sent to space.

Dummy in Tesla roadster in space with Earth in background.
SpaceX via Getty Images

In 2018, Elon Musk used SpaceX's Falcon Heavy rocket to launch his Tesla Roadster into space. The car was decked out with pop culture Easter eggs—according to Musk, "Space Oddity" was playing over the car’s radio system during the historic journey. The dummy’s name, Starman, is the name of another space-themed song on Bowie's 1972 masterpiece The Rise and Fall of Ziggy Stardust and the Spiders from Mars.