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.

1. EARTH, BY THE NUMBERS.

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.

2. SEEING IS BELIEVING.

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."

3. WE HAVE A NATURAL SATELLITE.

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.

4. LIFE FINDS A WAY …

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.

5. … BUT WE'RE DOING A POOR JOB OF PRESERVING IT.

"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?"

6. THE WATER IS RISING.

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."

7. THERE MAY BE ANSWERS UNDERWATER.

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.)

8. THERE IS STILL HOPE FOR OUR PALE BLUE DOT.

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."

How to See the Full Sturgeon Moon on Thursday

Brook Mitchell, Stringer/Getty Images
Brook Mitchell, Stringer/Getty Images

The full moon of every month has a special nickname. Some—like September's harvest moon, December's cold moon, and May's flower moon—have obvious connections to their seasons, while other names are harder to decode. August's sturgeon moon is an example of the latter. It may not be the prettiest lunar title in The Old Farmer's Almanac, but that doesn't mean the event itself on August 15, 2019 won't be a spectacular sight to behold.

What is a Full Sturgeon Moon?

The first (and normally the only) full moon that occurs in August is called a sturgeon moon. The name may have originated with Native American tribes living around the Great Lakes in the Midwest and Lake Champlain in New England. These bodies of water contain lake sturgeon, a species of freshwater fish that grows up to 6.5 feet in length and can live 55 years or longer. August's full moon was dubbed the sturgeon moon to reflect its harvesting season. This full moon is sometimes called the green corn moon, the grain moon, and the blackberry moon for similar reasons.

When to See the Full Sturgeon Moon

On Thursday, August 15, the full sturgeon moon will be highly visible around sunrise and sunset. The satellite will be 99.9 percent illuminated by the sun when it sets Thursday morning at 5:57 a.m EDT—just nine minutes before dawn. On the West Coast, the setting moon will coincide perfectly with the rising sun at 6:15 a.m. PDT.

If you aren't interested in getting out of bed early to catch the sturgeon moon, wait until Thursday evening to look to the horizon. Twenty-seven minutes after sunset, the full moon will rise on the East Coast at 8:21 p.m. EDT. On the West Coast it rises at 8:10 p.m. PDT, 30 minutes after the sun sets.

The moon generally looks bigger and brighter when it's near the horizon, so twilight and dawn are ideal times to catch the spectacle. But it's worth taking another peek at the sky closer to midnight Thursday night; the Perseid meteor shower is currently active, and though the light of the moon may wash them out, you're most likely to spot a shooting star in the late night and early morning hours.

A Full Harvest Moon Is Coming in September

suerob/iStock via Getty Images
suerob/iStock via Getty Images

The Old Farmer's Almanac lists a special name for every month's full moon, from January's wolf moon to December's cold moon. Even if you're just a casual astronomy fan, you've likely heard the name of September's full moon. The harvest moon is the full moon that falls closest to the fall equinox, and it's associated with festivals celebrating the arrival of autumn. Here's what you need to know before catching the event this year.

What is a harvest moon?

You may have heard that the harvest moon is special because it appears larger and darker in the night sky. This may be true depending on what time of night you look at it, but these features are not unique to the harvest moon.

Throughout the year, the moon rises on average 50 minutes later each night than it did the night before. This window shrinks in the days surrounding the fall equinox. In mid-latitudes, the moon will rise over the horizon only 25 minutes to 30 minutes later night after night. This means the moonrise will occur around sunset several evenings in a row.

So what does this mean for the harvest moon? If you're already watching the sunset and you catch the moonrise at the same time, it will appear bigger than usual thanks to something called the moon illusion. It may also take on an orange-y hue because you're gazing at it through the thick filter of the Earth's atmosphere, which absorbs blue light and projects red light. So if you've only seen the full harvest moon around sunset, you may think it always looks especially big and orange, while in reality, any full moon will look that way when it's just above the horizon.

When to See the Harvest Moon

This year, the harvest moon will be visible the night of Saturday, September 14—about a week before the fall equinox on September 23. The moon will reach its fullest state at 12:33 a.m. ET—but if you're still convinced it's not a true harvest moon without that pumpkin-orange color, you can look for it at moonrise at 7:33 p.m. on September 13.

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