If you go out hiking this weekend and somehow find yourself hopelessly lost in the wilderness, but suddenly remember you have a compass with you, you can use it to find north because the needle always points towards the Earth’s geographic north pole, which never changes… right?
Wrong, wrong, and wrong. And this video from MinutePhysics explains why.
(But still bring a compass with you. They do come in handy.)
An aurora seen from the International Space Station on September 26, 2011. Credit: NASA.
Astronauts have tried to explain the view of Earth from space, with many saying that there just aren’t the words to describe how beautiful it is. In the latest episode of the “Science Garage,” recent ISS astronauts Tom Marshburn and Chris Hadfield might do the best job so far of relating not only the “incredible and unwrapping perspective of looking at the Earth,” but how it changed their perspective of humanity. Hadfield compares coming into the cupola of the International Space Station as being like “entering the Sistine Chapel.”
China's now-industrialized Pearl River Delta, seen in October 1973 (top) and January 2003 (bottom)
Since the launch of its first satellite in 1972, the eight NASA/USGS Landsat satellites have made the longest continuous observations of Earth’s surface, providing invaluable data for research in agriculture, geology, forestry, regional planning, education, mapping, global change research, as well as important emergency response and disaster relief information. In addition, having such a long span of data allows us to easily see the expansion of human development in many areas — unprecedented before-and-after views of city growth seen from space.
These images, taken over the course of the Landsat program, illustrate the visible impact of over three decades of human development:
Chandler, Arizona imaged in 1985 (top) and 2011 (bottom.) As its economy shifted from agriculture to manufacturing and electronics, Chandler’s population multiplied 8 times to over 236,000.The explosion of Istanbul’s population from 2 to 13 million people is evident in these Landsat images, comparing 1975 to 2011. Vegetation appears red in the imaging wavelengths used here.A few years ago one of the fastest-growing cities in the US, Las Vegas is seen here in images taken in 1984 (top) and 2011 (bottom.) The sprawling development — as well as the decrease in water level of Lake Mead — is evident.Some of the most dramatic — and rapid — changes have occurred in Dubai, whose palm- and continent-shaped artificial islands suddenly appear between images taken in 2000 (top) and 2010 (bottom.) Once barely visible against the desert landscape, Dubai is now an international center of business, tourism, and oil production.
The Landsat Program is a series of Earth-observing satellite missions jointly managed by NASA and the U.S. Geological Survey. In 1972, the launch of ERTS-1 (Earth Resources Technology Satellite, later renamed Landsat 1) started the era of a series of satellites that have since continuously acquired space-based land remote sensing data.
The latest satellite in the Landsat series, the Landsat Data Continuity Mission (LDCM) — now named Landsat 8 — was launched on February 11, 2013. Landsat 8 data is now available free to the public online here.
The Day the Earth Smiled: Sneak Preview. In this rare image taken on July 19, 2013, the wide-angle camera on NASA's Cassini spacecraft has captured Saturn's rings and our planet Earth and its moon in the same frame. Image Credit: NASA/JPL-Caltech/Space Science Institute
The Day the Earth Smiled: Sneak Preview
In this rare image taken on July 19, 2013, the wide-angle camera on NASA’s Cassini spacecraft has captured Saturn’s rings and our planet Earth and its moon in the same frame. Image Credit: NASA/JPL-Caltech/Space Science Institute
See below our wider context mosaic of the Earth, Saturn and its majestic rings[/caption]
Breathtaking raw images of the Earth and Saturn system snapped by NASA’s Cassini spacecraft on July 19 during the worldwide ‘Wave at Saturn’ campaign are streaming back across 1 billion miles of interplanetary space.
Science team members are now busily processing the images to create individual color composites and a panoramic view of the ‘pale blue dot’ and the entire Saturnian system.
NASA just released the first individual color composite focusing on Earth – see above. And its spectacular!
See below our preliminary mosaic showing the Earth in context with nearly half of Saturn and floating in between its incomparably majestic rings.
Partial context mosaic of the Earth and Saturn taken by NASA’s Cassini orbiter on July 19, 2013. This mosaic was assembled from five wide angle camera raw images and offers a sneak peek of the complete panorama. Credit: NASA/JPL-Caltech/Ken Kremer/Marco Di Lorenzo
To capture all of Saturn and its wide swath of rings, Cassini’s wide angle camera snapped a mosaic of 33 footprints.
“At each footprint, images were taken in different spectral filters for a total of 323 images,” says Carolyn Porco, Cassini Imaging Team leader of the Space Science Institute in Boulder, Colo.
Cassini took the pictures of Earth between 2:27 and 2:42 p.m. PDT on Friday, July 19 from a distance of about 898 million miles (1.44 billion kilometers) away from the home to every human being that has ever lived.
The images show the Earth and the Moon as dots barely about a pixel wide but do reveal the ‘pale blue dot’ that is home to all of humanity and our whitish colored neighbor.
Distant views of the Earth from our robotic explorers, especially from the outer reaches of our Solar System, are few and far between, and are therefore events for space and astronomy enthusiasts and everyone else to savor.
“One of the most exciting Cassini events in 2013 will be the unusual opportunity on July 19 to image the whole Saturn system as it is backlit by the sun,” explained Linda Spilker, Cassini project scientist of NASA’s Jet Propulsion Laboratory, Pasadena, Calif.
“With Saturn covering the harsh light of the sun, we will be gathering unique ring science and also catching a glimpse of our very own home planet.”
Cassini previously took an absolutely fabulous mosaic of Saturn and Earth back in 2006 that stands as one of the landmark images of the space age.
Besides being picturesque, such mosaics also serve science. For example, the 2006 image “revealed that the dusty E ring, which is fed by the water-ice plume of the moon Enceladus, had unexpectedly large variations in brightness and color around its orbit,” says Spilker.
“We’ll want to see how that looks seven Earth years and a Saturnian season later, giving us clues to the forces at work in the Saturn system. We’ll do this analysis by collecting data from our visual and infrared mapping spectrometer, composite infrared mapping spectrometer and ultraviolet imaging spectrograph in addition to the imaging cameras.”
This simulated view from NASA’s Cassini spacecraft shows the expected positions of Saturn and Earth on July 19, 2013, around the time Cassini will take Earth’s picture. Cassini will be about 898 million miles (1.44 billion kilometers) away from Earth at the time. That distance is nearly 10 times the distance from the sun to Earth. Image credit: NASA/JPL-Caltech
“July 19 marked the first time people on Earth had advance notice their planet’s portrait was being taken from interplanetary distances,” says NASA.
I waved fondly at Saturn and hope you had the chance to wave at Saturn from all across the globe. NASA reports that nearly 20,000 participated in organized events. Countless others waved too.
Cassini was launched in 1997 and achieved orbit at Saturn in 2004. The mission is scheduled to continue until 2017 when it will commit a suicide death dive into the gas giant.
“We can’t see individual continents or people in this portrait of Earth, but this pale blue dot is a succinct summary of who we were on July 19,” said Spilker in a NASA statement.
“Cassini’s picture reminds us how tiny our home planet is in the vastness of space, and also testifies to the ingenuity of the citizens of this tiny planet to send a robotic spacecraft so far away from home to study Saturn and take a look-back photo of Earth.”
JPL Waves at Saturn
As NASA’s Cassini spacecraft turned its imaging cameras to Earth, scientists, engineers and visitors at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., gathered to wave at our robotic photographer in the Saturn system on July 19, 2013. Credit: NASA/JPL-Caltech
Earth and Moon imaged from Cassini on July 19, 2013
Did you smile and wave at Saturn on Friday? If you did (and even if you didn’t) here’s how you — and everyone else on Earth — looked to the Cassini spacecraft, 898.4 million miles away.
Hope you didn’t blink!
The image above is a color-composite made from raw images acquired by Cassini in red, green, and blue visible light wavelengths. Some of the specks around the edges are background stars, and others are the result of high-energy particle noise, of which some have been digitally removed.
The Moon is the bright dot just below and to the left of Earth. (An original raw image can be seen here.)
Cassini acquired the images while capturing views of Saturn in eclipse against the Sun between 22:24:00 UTC on July 19 and 02:43:00 UTC on July 20 (6:24 to 10:43 pm EDT July 19.) On Cassini time, the Earth imaging took place between 22:47:13 UTC (6:47:13 pm EDT) and 23:01:56 UTC (7:01:56 pm EDT) on the 19th.
Full mosaic arrangement acquired by Cassini on July 19-20 UTC. Earth was positioned just below the planet. (NASA/JPL-Caltech/SSI)
The world was invited to “Wave at Saturn” beginning 5:27 pm EDT on Friday — which allowed enough time for the photons from a waving world to actually reach Cassini’s camera just beyond Saturn, 1.44 billion kilometers away. (Did you wave? I did!) It was the first time Earth’s population was made aware beforehand that their picture would be taken from such a cosmic distance.
A crowd gathered on the mall at NASA’s Jet Propulsion Laboratory in Pasadena to wave at Saturn on July 19 (NASA/JPL-Caltech)
The image of our planet and moon, seen as merely a couple of bright points of light against the blackness of space, recalls Sagan’s poignant “pale blue dot” passage from Cosmos…
“From this distant vantage point, the Earth might not seem of any particular interest. But for us, it’s different. Consider again 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 “pale blue dot” of Earth captured by Voyager 1 in Feb. 1990 (NASA/JPL)
The Earth is a very small stage in a vast cosmic arena. 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. 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.
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.”
— Carl Sagan (1934–1996)
A full mosaic of Cassini’s imaging of Saturn silhouetted against the Sun is expected in the coming weeks.
UPDATE: Here’s another RGB color composite, made from raw images acquired with Cassini’s wide-angle camera. It shows a view of Saturn and the rings in eclipse as seen from below and behind, backlit by the Sun. Earth is the bright point light near the center. (See original here.)
Raw image (RGB composite) of Saturn in eclipse with Earth in the distance — just a pale blue dot. (NASA/JPL-Caltech/SSI. Composite by J. Major.)
Images: NASA/JPL-Caltech/Space Science Institute. Composites by Jason Major.
Collisions of neutron stars produce powerful gamma-ray bursts – and heavy elements like gold (Credit: Dana Berry, SkyWorks Digital, Inc.)
Are you wearing a gold ring? Or perhaps gold-plated earrings? Maybe you have some gold fillings in your teeth… for that matter, the human body itself naturally contains gold — 0.000014%, to be exact! But regardless of where and how much of the precious yellow metal you may have with you at this very moment, it all ultimately came from the same place.
And no, I don’t mean Fort Knox, the jewelry store, or even under the ground — all the gold on Earth likely originated from violent collisions between neutron stars, billions of years in the past.
Recent research by scientists at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts has revealed that considerable amounts of gold — along with other heavy elements — are produced during impacts between neutron stars, the super-dense remains of stars originally 1.4 to 9 times the mass of our Sun.
The team’s investigation of a short-duration gamma-ray outburst that occurred in June (GRB 130603B) showed a surprising residual near-infrared glow, possibly from a cloud of material created during the stellar merger. This cloud is thought to contain a considerable amount of freshly-minted heavy elements, including gold.
“We estimate that the amount of gold produced and ejected during the merger of the two neutron stars may be as large as 10 moon masses – quite a lot of bling!” said lead author Edo Berger.
“With this remnant of a dead neutron star, I thee wed.” (FreeDigitalPhotos.net/bigjom)
The mass of the Moon is 7.347 x 1022 kg… about 1.2% the mass of Earth. The collision between these neutron stars then, 3.9 billion light-years away, produced 10 times that much gold based on the team’s estimates.
Quite a lot of bling, indeed.
Gamma-ray bursts come in two varieties – long and short – depending on the duration of the gamma-ray flash. GRB 130603B, detected by NASA’s Swift satellite on June 3rd, lasted for less than two-tenths of a second.
Although the gamma rays disappeared quickly, GRB 130603B also displayed a slowly fading glow dominated by infrared light. Its brightness and behavior didn’t match the typical “afterglow” created when a high-speed jet of particles slams into the surrounding environment.
Instead, the glow behaved like it came from exotic radioactive elements. The neutron-rich material ejected by colliding neutron stars can generate such elements, which then undergo radioactive decay, emitting a glow that’s dominated by infrared light – exactly what the team observed.
“We’ve been looking for a ‘smoking gun’ to link a short gamma-ray burst with a neutron star collision,” said Wen-fai Fong, a graduate student at CfA and a co-author of the paper. “The radioactive glow from GRB 130603B may be that smoking gun.”
The team calculates that about one-hundredth of a solar mass of material was ejected by the gamma-ray burst, some of which was gold. By combining the estimated gold produced by a single short GRB with the number of such explosions that have likely occurred over the entire age of the Universe, all the gold in the cosmos – and thus on Earth – may very well have come from such gamma-ray bursts.
Watch an animation of two colliding neutron stars along with the resulting GRB below (Credit: Dana Berry, SkyWorks Digital, Inc.):
How much gold is there on Earth, by the way? Since most of it lies deep inside Earth’s core and is thus unreachable, the total amount ever retrieved by humans over the course of history is surprisingly small: about 172,000 tonnes, or enough to make a cube 20.7 meters (68 feet) per side (based on the Thomson Reuters GFMS annual survey.) Some other estimates put this amount at slightly more or less, but the bottom line is that there really isn’t all that much gold available in Earth’s crust… which is partly what makes it (and other “precious” metals) so valuable.
And perhaps the knowledge that every single ounce of that gold was created by dead stars smashing together billions of years ago in some distant part of the Universe would add to that value.
“To paraphrase Carl Sagan, we are all star stuff, and our jewelry is colliding-star stuff,” Berger said.
The team’s findings were presented today in a press conference at the CfA in Cambridge. (See the paper here.)
The Pacific Ring of Fire, a strong of volcanic . Credit:
The Pacific Ring of Fire wraps around the Pacific Ocean, including countries like Japan, Canada, New Zealand and Chile. And the inhabitants within those countries are prone to… oh… killer earthquakes, volcanoes and tsunamis. Let’s chat about the history of this region and the kinds of risks they face.
And the podcast is also available as a video, as Fraser and Pamela now record Astronomy Cast as part of a Google+ Hangout (usually recorded every Monday at 3 pm Eastern Time):
This graphic shows the view of Earth and the portion of its surface that will be illuminated during the Earth imaging event by the Cassini spacecraft on July 19, 2013. Credit: NASA/JPL-Caltech.
July 19, 2013 will be a day that we should really all try to get along. Isn’t that a noble goal? And you can be a part of it in several different ways. In a special project, the Cassini spacecraft will be taking an image of Earth, from the spacecraft’s orbit around Saturn. Specifically, Cassini will be on the far side of Saturn when it snaps a picture of “us” between 21:27 to 21:42 UTC (5:27-5:42 pm EDT.) Cassini will be in just the right spot that it can “see” Earth, but Saturn will be blocking the glare from the Sun. There will likely be a dramatic view of Saturn and its rings in the foreground, with Earth off in the distance. Our home planet won’t be much more than a few pixels in the image, but it will be “us, …everyone you love, everyone you know, everyone you ever heard of, every human being who ever was,” as Carl Sagan said about the Pale Blue Dot image taken by the Voyager spacecraft.
“It will be a day to revel in the extraordinary achievements in the exploration of our solar system that have made such an interplanetary photo session possible,” said Cassini imaging team leader Carolyn Porco of the Space Science Institute, who had the idea for this special image. “And it will be a day for all of us to smile and celebrate life on the Pale Blue Dot.”
First, while Earth has been imaged before from other distant spacecraft (the famous Pale Blue Dot image and Cassini has taken pictures of Earth before) this is the first time that many of the inhabitants of Earth will know the image is being taken – hence the invitation to smile and wave.
Second, Saturn is now visible in the night sky — bright and shining — allowing us a direct line of sight to smile and wave back. No, we can’t see Cassini, but we know it’s there!
Plus, there’s other special chances to submit your own images – of Saturn, and of Earth, or of yourself in the moments Cassini is taking the image.
Astronomers Without Borders is also sponsoring a special Saturn Observing Program, and they are encouraging people and organizations to either organize a special observing event for July 19 (you can register it as an official event here) or to attend an event near you. You can find TDTES events here. This can be a full-blown observing event with telescopes, or just an excuse to get together with friends to go out and look at Saturn in the night sky.
If you’re like me, you don’t change your computer’s desktop background nearly often enough… especially not considering all the fantastic space images that get released on an almost daily basis. But this picture, shared a couple of weeks ago by NASA’s Marshall Space Flight Center on their Flickr stream, really should inspire you to fix that. (I know it did for me!)
Captured by an Expedition 28 crew member aboard the International Space Station, this beautiful image shows a crescent-lit Moon seen through the upper layers of Earth’s atmosphere.
As it circles the globe, the ISS travels an equivalent distance to the Moon and back in about a day, making an excellent platform for viewing the Earth and its atmosphere. This photo shows the limb of Earth near the bottom transitioning into the orange-colored troposphere, the lowest and most dense portion of the Earth’s atmosphere. The troposphere ends abruptly at the tropopause, which appears in the image as the sharp boundary between the orange- and blue- colored atmosphere. Silvery-blue noctilucent clouds extend far above the Earth’s troposphere.
Expedition 28 began on May 23, 2011, with a crew consisting of Andrey Borisenko, Ron Garan, Alexander Samokutyaev, Sergei Volkov, Mike Fossum, and Satoshi Furukawa.
Look up into the night sky and count the moons. You can see only one moon, “the” Moon. But does the Earth have any other moons? Around the Solar System, multiple moons are the rule. Jupiter has 67 natural satellites, even Mars has two asteroid-like moons.
Could Earth have more than one?
Officially, the answer is no. The Earth has a single moon.
Today.
It’s possible Earth had more than one moon in the past, millions or even billions of years ago. Strange terrain on the far side of the Moon could be explained by a second moon crashing into it, depositing a layer of material tens of kilometers deep.
Moons could come and go over the billions of years of the Earth’s history.
For example, Mars has two Moons, but not for long. Phobos, the larger moon, is spiraling inward and expected to crash into the planet within the next 10 million years. And so, in the future, Mars will only have a single Moon, Deimos.
It’s also possible that the Earth might capture a Moon in the future. Neptune’s largest moon, Triton, orbits in the opposite direction from the rest of the moons around the planet. This suggests that Triton was actually a captured Kuiper Belt Object which strayed too close to the planet.
2006 RH120In fact, we did capture a 5-metre asteroid called 2006 RH120. It orbited the Earth four times during 2006/2007 before getting ejected again.
So we can assume events like this have happened in the past.
Additionally, we might have more moons, but they haven’t been discovered yet because they’re just too small. Researchers have calculated that there could be meter-sized asteroids in orbit around the Earth, remaining in orbit for hundreds of years before gravitational interactions push them out again.
And there are other objects that interact with Earth’s orbit in strange ways. Scientists don’t consider them moons, but they do stick around in our neighbourhood:
Asteroid 3753 Cruithne is in an orbital resonance with the Earth. It has a highly eccentric orbit, but takes exactly one year to orbit the Sun. From our perspective, it follows a slow, horse-shoe shaped path across the sky. Since the discovery of Cruithne in 1986, several other resonant near-Earth objects have been discovered.
2007 TK7There’s 2010 TK7, the Earth’s only known Trojan asteroid. It leads the Earth in the exact same orbit around the Sun, in a gravitationally stable point in space.
So, the answer… Earth only has a single Moon. Today. We might have had more moons in the past, and we might capture more in the future, but for right now… enjoy the one we’ve got.
