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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."

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NSF/LIGO/Sonoma State University/A. Simonnet
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Space
Astronomers Observe a New Kind of Massive Cosmic Collision for the First Time
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NSF/LIGO/Sonoma State University/A. Simonnet

For the first time, astronomers have detected the colossal blast produced by the merger of two neutron stars—and they've recorded it both via the gravitational waves the event produced, as well as the flash of light it emitted.

Physicists believe that the pair of neutron stars—ultra-dense stars formed when a massive star collapses, following a supernova explosion—had been locked in a death spiral just before their final collision and merger. As they spiraled inward, a burst of gravitational waves was released; when they finally smashed together, high-energy electromagnetic radiation known as gamma rays were emitted. In the days that followed, electromagnetic radiation at many other wavelengths—X-rays, ultraviolet, optical, infrared, and radio waves—were released. (Imagine all the instruments in an orchestra, from the lowest bassoons to the highest piccolos, playing a short, loud note all at once.)

This is the first time such a collision has been observed, as well as the first time that both kinds of observations—gravitational waves and electromagnetic radiation—have been recorded from the same event, a feat that required co-operation among some 70 different observatories around the world, including ground-based observatories, orbiting telescopes, the U.S. LIGO (Laser Interferometer Gravitational-Wave Observatory), and European Virgo gravitational wave detectors.

"For me, it feels like the dawning of a next era in astrophysics," Julie McEnery, project scientist for NASA's Fermi Gamma-ray Space Telescope, one of the first instruments to record the burst of energy from the cosmic collision, tells Mental Floss. "With this observation, we've connected these new gravitational wave observations to the rest of the observations that we've been doing in astrophysics for a very long time."

A BREAKTHROUGH ON SEVERAL FRONTS

The observations represent a breakthrough on several fronts. Until now, the only events detected via gravitational waves have been mergers of black holes; with these new results, it seems likely that gravitational wave technology—which is still in its infancy—will open many new phenomena to scientific scrutiny. At the same time, very little was known about the physics of neutron stars—especially their violent, final moments—until now. The observations are also shedding new light on the origin of gamma-ray bursts (GRBs)—extremely energetic explosions seen in distant galaxies. As well, the research may offer clues as to how the heavier elements, such as gold, platinum, and uranium, formed.

Astronomers around the world are thrilled by the latest findings, as today's flurry of excitement attests. The LIGO-Virgo results are being published today in the journal Physical Review Letters; further articles are due to be published in other journals, including Nature and Science, in the weeks ahead. Scientists also described the findings today at press briefings hosted by the National Science Foundation (the agency that funds LIGO) in Washington, and at the headquarters of the European Southern Observatory in Garching, Germany.

(Rumors of the breakthrough had been swirling for weeks; in August, astronomer J. Craig Wheeler of the University of Texas at Austin tweeted, "New LIGO. Source with optical counterpart. Blow your sox off!" He and another scientist who tweeted have since apologized for doing so prematurely, but this morning, minutes after the news officially broke, Wheeler tweeted, "Socks off!") 

The neutron star merger happened in a galaxy known as NGC 4993, located some 130 million light years from our own Milky Way, in the direction of the southern constellation Hydra.

Gravitational wave astronomy is barely a year and a half old. The first detection of gravitational waves—physicists describe them as ripples in space-time—came in fall 2015, when the signal from a pair of merging black holes was recorded by the LIGO detectors. The discovery was announced in February 2016 to great fanfare, and was honored with this year's Nobel Prize in Physics. Virgo, a European gravitational wave detector, went online in 2007 and was upgraded last year; together, they allow astronomers to accurately pin down the location of gravitational wave sources for the first time. The addition of Virgo also allows for a greater sensitivity than LIGO could achieve on its own.

LIGO previously recorded four different instances of colliding black holes—objects with masses between seven times the mass of the Sun and a bit less than 40 times the mass of the Sun. This new signal was weaker than that produced by the black holes, but also lasted longer, persisting for about 100 seconds; the data suggested the objects were too small to be black holes, but instead were neutron stars, with masses of about 1.1 and 1.6 times the Sun's mass. (In spite of their heft, neutron stars are tiny, with diameters of only a dozen or so miles.) Another key difference is that while black hole collisions can be detected only via gravitational waves—black holes are black, after all—neutron star collisions can actually be seen.

"EXACTLY WHAT WE'D HOPE TO SEE"

When the gravitational wave signal was recorded, on the morning of August 17, observatories around the world were notified and began scanning the sky in search of an optical counterpart. Even before the LIGO bulletin went out, however, the orbiting Fermi telescope, which can receive high-energy gamma rays from all directions in the sky at once, had caught something, receiving a signal less than two seconds after the gravitational wave signal tripped the LIGO detectors. This was presumed to be a gamma-ray burst, an explosion of gamma rays seen in deep space. Astronomers had recorded such bursts sporadically since the 1960s; however, their physical cause was never certain. Merging neutron stars had been a suggested culprit for at least some of these explosions.

"This is exactly what we'd hoped to see," says McEnery. "A gamma ray burst requires a colossal release of energy, and one of the hypotheses for what powers at least some of them—the ones that have durations of less than two seconds—was the merger of two neutron stars … We had hoped that we would see a gamma ray burst and a gravitational wave signal together, so it's fantastic to finally actually do this."

With preliminary data from LIGO and Virgo, combined with the Fermi data, scientists could tell with reasonable precision what direction in the sky the signal had come from—and dozens of telescopes at observatories around the world, including the U.S. Gemini telescopes, the European Very Large Telescope, and the Hubble Space Telescope, were quickly re-aimed toward Hydra, in the direction of reported signal.

The telescopes at the Las Campanas Observatory in Chile were well-placed for getting a first look—because the bulletin arrived in the morning, however, they had to wait until the sun dropped below the horizon.

"We had about eight to 10 hours, until sunset in Chile, to prepare for this," Maria Drout, an astronomer at the Carnegie Observatories in in Pasadena, California, which runs the Las Campanas telescopes, tells Mental Floss. She was connected by Skype to the astronomers in the control rooms of three different telescopes at Las Campanas, as they prepared to train their telescopes at the target region. "Usually you prepare a month in advance for an observing run on these telescopes, but this was all happening in a few hours," Drout says. She and her colleagues prepared a target list of about 100 galaxies, but less than one-tenth of the way through the list, by luck, they found it: a tiny blip of light in NGC 4993 that wasn't visible on archival images of the same galaxy. (It was the 1-meter Swope telescope that snagged the first images.)

A NEW ERA OF ASTROPHYSICS

When a new star-like object in a distant galaxy is spotted, a typical first guess is that it's a supernova (an exploding star). But this new object was changing very rapidly, growing 100 times dimmer over just a few days while also quickly becoming redder—which supernovae don't do, explains Drout, who is cross-appointed at the Dunlap Institute for Astronomy and Astrophysics at the University of Toronto. "We ended up following it for three weeks or so, and by the end, it was very clear that this [neutron star merger] was what we were looking at," she says.

The researchers say they can't be sure if the resulting object was another, larger neutron star, or whether it would have been so massive that it would have collapsed into a black hole.

As exciting as the original detection of gravitational waves last year was, Drout is looking forward to a new era in which both gravitational waves and traditional telescopes can be used to study the same objects. "We can learn a lot more about these types of extreme systems that exist in the universe, by coupling the two together," she says.

The detection shows that "gravitational wave science is moving from being a physics experiment to being a tool for astronomers," Marcia Rieke, an astronomer at the University of Arizona who is not involved in the current research, tells Mental Floss. "So I think it's a pretty big deal."

Physicists are also learning something new about the origin of the heaviest elements in the periodic table. For many years, these were thought to arise from supernova explosions, but spectroscopic data from the newly observed neutron star merger (in which light is broken up into its component colors) suggests that such explosion produce enormous quantities of heavy elements—including enough gold to put Fort Knox to shame. (The blast is believed to have created some 200 Earth-masses of gold, the scientists say.) "It's telling us that most of the gold that we know about is produced in these mergers, and not in supernovae," McEnery says.

Editor's note: This post has been updated.

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NASA/JPL-Caltech
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Space
Send Your Name to Space on NASA's Latest Mars Lander
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NASA/JPL-Caltech

Humans may not reach Mars until the 2030s (optimistically), but you can get your name there a whole lot sooner. As Space.com reports, NASA is accepting names from the public to be engraved on a small silicon microchip that's being sent into space with their latest Mars lander, InSight.

All you have to do is submit your name online to NASA, and the space agency will put it on the lander—in super-tiny form, of course—which will set off for Mars in May 2018.

This is the public's second shot at getting their name to Mars: NASA first put out a call for names to go to the Red Planet with InSight in 2015. The planned 2016 launch was delayed over an issue with one of the instruments, and since the naming initiative was so popular—almost 827,000 people submitted their names the first time around—they decided to open the opportunity back up and add a second microchip.

A scientist positions the microchip on the InSight lander.
NASA/JPL-Caltech/Lockheed Martin

NASA is encouraging people to sign up even if they've sent in their names for other mission microchips. (The space agency also sent 1.38 million names up with Orion's first test flight in 2014.) You can put your name on both of InSight's microchips, in other words, as well as any future missions. The agency's "frequent flyer" program allows you to keep track of every mission to which your name is attached. Interplanetary fame, here you come.

You can submit your name for the InSight mission until November 1 using this form. If you miss the deadline, though, don't worry too much: You'll soon be able to submit your name for Exploration Mission-1's November 2018 launch.

[h/t Space.com]

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