The Earth is often compared to a majestic blue marble, especially by those privileged few who have gazed upon it from orbit. This is due to the prevalence of water on the planet’s surface. While water itself is not blue, water gives off blue light upon reflection.
For those of us confined to living on the surface, the fact that our world is mostly covered in water is a well known fact. But how much of our planet is made up of water, exactly? Like most facts pertaining to our world, the answer is a little more complicated than you might think, and takes into account a number of different qualifications.
Sources of Water:
In simplest terms, water makes up about 71% of the Earth’s surface, while the other 29% consists of continents and islands. To break the numbers down, 96.5% of all the Earth’s water is contained within the oceans as salt water, while the remaining 3.5% is freshwater lakes and frozen water locked up in glaciers and the polar ice caps.
Of that fresh water, almost all of it takes the form of ice: 69% of it, to be exact. If you could melt all that ice, and the Earth’s surface was perfectly smooth, the sea levels would rise to an altitude of 2.7 km.
Illustration showing all of Earth’s water, liquid fresh water, and water in lakes and rivers. Credit: Howard Perlman, USGS/illustraion by Jack Cook, WHOI
Aside from the water that exists in ice form, there is also the staggering amount of water that exists beneath the Earth’s surface. If you were to gather all the Earth’s fresh water together as a single mass (as shown in the image above) it is estimated that it would measure some 1,386 million cubic kilometers (km3) in volume.
Meanwhile, the amount of water that exists as groundwater, rivers, lakes, and streams would constitute just over 10.6 million km3, which works out to a little over 0.7%. Seen in this context, the limited and precious nature of freshwater becomes truly clear.
Volume vs. Mass:
But how much of Earth is water – i.e. how much water contributes to the actual mass of the planet? This includes not just the surface of the Earth, but inside as well. In terms of volume, all of the water on Earth works out to about 1.386 billion cubic kilometers (km³) or 332.5 million cubic miles (mi³) of space.
But in terms of mas, scientists calculate that the oceans on Earth weight about 1.35 x 1018 metric tonnes (1.488 x 1018 US tons), which is the equivalent of 1.35 billion trillion kg, or 2976 trillion trillion pounds. This is just 1/4400 the total mass of the Earth, which means that while the oceans cover 71% of the Earth’s surface, they only account for 0.02% of our planet’s total mass.
Many theories about the origins of water on Earth attribute it to collisions with comets and asteroids. Credit: NASA/JPL/Caltech
Source of Earth’s Water:
The origin of water on the Earth’s surface, as well as the fact that it has more water than any other rocky planet in the Solar System, are two of long-standing mysteries concerning our planet. Not that long ago, it was believed that our planet formed dry some 4.6 billion years ago, with high-energy impacts creating a molten surface on the infant Earth.
According to this theory, water was brought to the world’s oceans thanks to icy comets, trans-Neptunian objects or water-rich meteoroids (protoplanets) from the outer reaches of the main asteroid belt colliding with the Earth.
However, more recent research conducted by the Woods Hole Oceanographic Institution (WHOI) in Woods Hole, Massachusetts, has pushed the date of these origins back further. According to this new study, the world’s oceans also date back 4.6 billion years, when all the worlds of the inner Solar System were still forming.
This conclusion was reached by examining meteorites thought to have formed at different times in the history of the Solar System. Carbonaceous chondrite, the oldest meteorites that have been dated to the very earliest days of the Solar System, were found to have the same chemistry as those originating from protoplanets like Vesta. This includes a significance presence of water.
These meteorites are dated to the same epoch in which water was believed to have formed on Earth – some 11 million years after the formation of the Solar System. In short, it now appears that meteorites were depositing water on Earth in its earliest days.
While not ruling out the possibility that some of the water that covers 71 percent of Earth today may have arrived later, these findings suggest that there was enough already here for life to have begun earlier than thought.
It’s a dangerous universe out there, for a budding young space-faring species.
Killer comets, planet sterilizing gamma ray bursts, and death rocks from above are all potential hazards that an adolescent civilization has to watch out for.
This week offers two close shaves, as newly discovered Near Earth Asteroids (NEAs) 2014 WC201 and 2014 WX202 pass by the Earth-Moon system.
The passage of 2014 WC201 is coming right up tonight, as the 27-metre space rock passes about 570,000 kilometres from the Earth. That’s 1.4 times farther than the distance from the Earth to the Moon.
And the good news is, the Virtual Telescope Project will be bringing the passage of 2014 WC201 live tonight starting at 23:00 Universal Time/6:00 PM EST.
Shining at an absolute magnitude of +26, 2014 WC201 will be visible as a +13 apparent magnitude “star” at closest approach at 4:51 UT (December 2nd)/11:51 PM EST (December 1st) moving through the constellation Ursa Major. This puts it within range of a large backyard telescope, though the 80% illuminated waxing gibbous Moon will definitely be a mitigating factor for observation.
The JPL Horizons ephemerides generator is an excellent place to start for crafting accurate coordinates for the asteroid for your location.
A capture of NEO 2003 DZ15 from 2015. Credit: The Virtual Telescope Project.
At an estimated 27 metres/81 feet in size, 2014 WC201 will no doubt draw “house-sized” or “building-sized” comparisons in the press. Larger than an F-15 jet fighter, asteroids such as WC201 cry out for some fresh new descriptive comparisons. Perhaps, as we near a “Star Wars year” in 2015, we could refer to 2014 WC201 as X-wing sized?
Another Apollo NEO also makes a close pass by the Earth this week, as 6-metre 2014 WX202 passes 400,000 kilometres (about the same average distance as the Earth to the Moon) from us at 19:56 UT/2:56 PM EST on December 7th. Though closer than WC201, WX202 is much smaller and won’t be a good target for backyard scopes. Gianluca Masi over at the Virtual Telescope Project also notes that WX202 will also be a difficult target due to the nearly Full Moon later this week.
The orbital path of NEO asteroid 2014 WX202. Credit: NASA/JPL
The last Full Moon of 2014 occurs on December 6th at 6:26 AM EST/11:26 Universal Time.
2014 WX202 has also generated some interest in the minor planet community due to its low velocity approach relative to the Earth. This, coupled with its Earth-like orbit, is suggestive of something that may have escaped the Earth-Moon system. Could WX202 be returning space junk or lunar ejecta? It’s happened before, as old Apollo hardware and boosters from China’s Chang’e missions have been initially identified as Near Earth Asteroids.
The Earth also occasionally hosts a temporary “quasi-moon,” as last occurred in 2006 with the capture of RH120. 2014 WX202 makes a series of more distant passes in the 2030s, and perhaps it will make the short list of near Earth asteroids for humans to explore in the coming decades.
And speaking of which, humanity is making two steps in this direction this week, with two high profile space launches.
First up is the launch of JAXA’s Hayabusa 2 from the Tanegashima Space Center on December 3rd at 4:22 UT/11:22 PM EST. The follow up to the Hayabusa asteroid sample return mission, Hayabusa 2 will rendezvous with asteroid 1999 JU3 in 2018 and return samples to Earth in late 2020. The vidcast for the launch of Hayabusa 2 goes live at 3:00 UT/10:00 PM EST on Tuesday, December 2nd.
And the next mission paving the way towards first boot prints on an asteroid is the launch of a Delta 4 Heavy rocket with EFT-1 from Cape Canaveral this Thursday morning on December 4th near sunrise at 7:05 AM EST/12:05 UT. EFT-1 is uncrewed, and will test key technologies including reentry on its two orbit flight. Expect to see crewed missions of Orion to begin around 2020, with a mission to an Earth crossing asteroid sometime in the decade after that.
NASA gotchu: An artist’s rendition of a future asteroid capture. Credit: NASA.
And there are some decent prospects to catch sight of EFT-1 on its first pass prior to its orbit raising burn over the Atlantic. Assuming EFT-1 lifts off at the beginning of its launch window, western Australia may see a good dusk pass 55 minutes after liftoff, and the southwestern U.S. may see a visible pass at dawn about 95 minutes after EFT-1 leaves the pad.
The footprint of EFT-1 on its first North American pass. Credit: Orbitron.
We’ll be tracking these prospects as the mission evolves on launch day via Twitter, and NASA TV will carry the launch live starting at 4:30 AM EST/9:30 UT.
The Orion capsule will come in hot on reentry at a blistering 32,000 kilometres per hour over four hours after liftoff in a reentry reminiscent of the early Apollo era.
Of course, if an asteroid the size of WC201 was on a collision course with the Earth it could spell a very bad day, at least in local terms. For comparison, the 2013 Chelyabinsk meteor was estimated to be 18 metres in size, and the 1908 Tunguska impactor was estimated to be 60 metres across. And about 50,000 years ago, a 50 metre in diameter space rock came blazing in over the ponderosa pine trees near what would one day be the city of Flagstaff, Arizona to create the 1,200 metre diameter Barringer Meteor Crater you can visit today.
A fragment of the Barringer meteorite on display at the Lowell Observatory. Photo by author.
All the more reason to study hazardous space rocks and the technology needed to reach one in the event that we one day need to move one out of the way!
One day – and it really is only matter of time – humans will set foot on the surfaces of other far-flung worlds in our Solar System, leaving the Earth and Moon far behind to wander the valleys of Mars, trek across the ice of Europa, and perhaps even soar through the skies of Titan like winged creatures from ancient legends. But until then we must rely on the exploration of our robotic emissaries and our own boundless imagination and curiosity to picture what such voyages would be like. Here in “Wanderers,” video artist Erik Wernquist has used both resources in abundance to visualize fascinating off-world adventures yet to be undertaken by generations to come. Continue reading “This Short Film is a Stunning Preview of Human Space Exploration”
Here’s our most-recommended holiday gift every year: The Year In Space Calendar! And for 2015 it’s back, it’s big and it’s what every space enthusiast will enjoy all year. The gigantic wall calendar is full of amazing color images, daily space facts, historical references, and it even shows you where you can look in the sky for all the best astronomical sights. The 2015 version of Steve Cariddi’s wonderful Year in Space wall and desk calendars are now available to order, perfect for your Cyber Monday shopping.
The gorgeous wall calendar has over 120 crisp color images and is larger, more lavishly illustrated, and packed with more information than any other space-themed wall calendar. It’s a huge 16″ x 22″ when hanging up!
Published in cooperation with The Planetary Society, the Year In Space calendar takes you on a year-long guided tour of the Universe, providing in-depth info on human space flight, planetary exploration, and deep sky wonders. You’ll even see Universe Today featured in this calendar!
Other features of the Year In Space calendar:
– Background info and fun facts
– A sky summary of where to find naked-eye planets
– Space history dates
– Major holidays (U.S. and Canada)
– Daily Moon phases
– A mini-biography of famous astronomer, scientist, or astronaut each month
These calendars normally sell for $17.95, but Universe Today readers can buy the calendar for only $13.95 or less (using the “Internet” discount), and get free U.S. shipping and discounted international shipping. There are also volume discounts. Check out all the details here.
Artist's impression of the Jupiter Icy Moons Explorer (JUICE) near Jupiter and one of its moons, Europa. Credit: ESA/AOES
It takes years of painstaking work to get a spacecraft off the ground. So when you have a spacecraft like JUICE (the Jupiter Icy Moons Explorer) set to launch in 2022, you need to back up about a decade to get things figured out. How will the spacecraft get there? What science instruments will it carry? What will the spacecraft look like and what systems will support its work?
JUICE just hit another milestone in its development a few days ago, when the European Space Agency gave the go-ahead for the “implementation phase” — the part where the spacecraft design begins to take shape. The major goal of the mission will be to better understand those moons around Jupiter that could be host to life.
The spacecraft will reach Jupiter’s system in 2030 and begin with observations of the mighty planet — the biggest in our Solar System — to learn more about the gas giant’s atmosphere, faint rings and magnetic environment. It also will be responsible for teaching us more about Europa (an icy world that could host a global ocean) and Callisto (a moon pockmarked with the most craters of anything in the Solar System.)
Its major departure from past missions, though, will come when JUICE enters orbit around Ganymede. This will the first time any spacecraft has circled an icy moon repeatedly; past views of the moon have only come through flybys by the passing-through spacecraft (such as Pioneer and Voyager) and the Galileo mission, which stuck around Jupiter’s system in the 1990s and early 2000s.
Ganymede Credit: NASA
With Ganymede, another moon thought to host a global ocean, JUICE will examine its surface and insides. What makes the moon unique in our neighborhood is its ability to create its own magnetic field, which creates interesting effects when it interacts with Jupiter’s intense magnetic environment.
“Jupiter’s diverse Galilean moons – volcanic Io, icy Europa and rock-ice Ganymede and Callisto – make the Jovian system a miniature Solar System in its own right,” the European Space Agency stated when the mission was selected in 2012.
“With Europa, Ganymede and Callisto all thought to host internal oceans, the mission will study the moons as potential habitats for life, addressing two key themes of cosmic vision: what are the conditions for planet formation and the emergence of life, and how does the Solar System work?”
The Big Bang Theory: A history of the Universe starting from a singularity and expanding ever since. Credit: grandunificationtheory.com
Astronomers are pretty sure what happened after the Big Bang, but what came before? What are the leading theories for the causes of the Big Bang?
About 13.8 billion years ago the Universe started with a bang, kicked the doors in, brought fancy cheeses and a bag of ice, spiked the punch bowl and invited the new neighbors over for all-nighter to encompass all all-nighters from that point forward.
But what happened before that?
What was going on before the Big Bang? Usually, we tell the story of the Universe by starting at the Big Bang and then talking about what happened after. Similarly and completely opposite to how astronomers view the Universe… by standing in the present and looking backwards. From here, the furthest we can look back is to the cosmic microwave background, which is about 380,000 years after the big bang.
Before that we couldn’t hope to see a thing, the Universe was just too hot and dense to be transparent. Like pea soup. Soup made of delicious face burning high energy everything.
In traditional stupid earth-bound no-Tardis life unsatisfactory fashion, we can’t actually observe the origin of the Universe from our place in time and space.
Damn you… place in time and space.
Fortunately, the thinky types have come up with some ideas, and they’re all one part crazy, one part mind bendy, and 100% bananas. The first idea is that it all began as a kind of quantum fluctuation that inflated to our present universe.
Artistic view of a radiating black hole. Credit: NASA
Something very, very subtle expanding over time resulting in, as an accidental byproduct, our existence. The alternate idea is that our universe began within a black hole of an older universe.
I’m gonna let you think about that one. Just let your brain simmer there.
There was universe “here”, that isn’t our universe, then that universe became a black hole… and from that black hole formed us and EVERYTHING around us. Literally, everything around us. In every direction we look, and even the stuff we just assume to be out there.
Here’s another one. We see particles popping into existence here in our Universe. What if, after an immense amount of time, a whole Universe’s worth of particles all popped into existence at the same time. Seriously… an immense amount of time, with lots and lots of “almost” universes that didn’t make the cut.
BICEP2 Telescope at twilight at the South Pole, Antartica (Credit: Steffen Richter, Harvard University)
More recently, the BICEP2 team observed what may be evidence of inflation in the early Universe.
Like any claim of this gravity, the result is hotly debated. If the idea of inflation is correct, it is possible that our universe is part of a much larger multiverse. And the most popular form would produce a kind of eternal inflation, where universes are springing up all the time. Ours would just happen to be one of them.
It is also possible that asking what came before the big bang is much like asking what is north of the North Pole. What looks like a beginning in need of a cause may just be due to our own perspective. We like to think of effects always having a cause, but the Universe might be an exception. The Universe might simply be. Because.
You tell us. What was going on before the party started? Let us know in the comments below.
And if you like what you see, come check out our Patreon page and find out how you can get these videos early while helping us bring you more great content!
Artist's conception of the Dawn spacecraft approaching the asteroid Ceres. Credit: NASA/JPL-Caltech
The year 2015 is going to be a big one for far-off spacecraft. Among them is the long-running Dawn mission, which is on its way to the dwarf planet Ceres (by way of Vesta) and should settle into orbit in April after a radiation blast delayed the original flight plan.
And today (Dec. 1) comes a special day for Dawn — when it turns its cameras to Ceres to capture the world, which will appear about nine pixels across. The reason? Besides scientific curiosity, it turns out to be a perfect calibration target, according to NASA.
“One final calibration of the science camera is needed before arrival at Ceres,” wrote Marc Rayman, the mission director at the Jet Propulsion Laboratory, in a recent blog post.
“To accomplish it, the camera needs to take pictures of a target that appears just a few pixels across. The endless sky that surrounds our interplanetary traveler is full of stars, but those beautiful pinpoints of light, while easily detectable, are too small for this specialized measurement. But there is an object that just happens to be the right size. On Dec. 1, Ceres will be about nine pixels in diameter, nearly perfect for this calibration.”
The Dawn spacecraft’s first image of Ceres, taken July 20, 2010. Credit: NASA/JPL-Caltech/MPS/DLR/IDA
This isn’t the first picture of Ceres by Dawn — not by a long-shot — but it sure will loom bigger than you see in the image at left, which was taken in 2010. Dawn hadn’t even arrived at Vesta at the time, the blog post points out, and the spacecraft was about 1,300 times further from Ceres then as it is now. Translating that into visual magnitude, the new pictures of Ceres will show an appearance about as bright as Venus, from Earth’s perspective.
In October, the Dawn blog said that more pictures of Ceres are planned on Jan. 13, when Ceres will appear 25 pixels across. This won’t be quite the best view ever — that was taken by the Hubble Space Telescope, which you can see below, — but just wait a couple of weeks. The mission planners say that by Jan. 26, the images will be slightly better. On Feb. 4, they will be twice as good and by Feb. 20, seven times as good.
As with the calibration photo taken today, these photos in 2015 will have a double purpose: optical navigation. It’s to help the spacecraft figure out where to go, because our pictures of Ceres are so fuzzy that mission planners will need more exact information as the mission proceeds.
You can read more information about the picture-taking, and Dawn’s planned approach to Ceres, in the Nov. 28 entry of the Dawn blog.
Pictures of the asteroid Ceres taken by the Hubble Space Telescope and released in 2005. It shows the asteroid rotating over two hours and 20 minutes, which is about a quarter of a day on Ceres (nine hours). At the time, scientists said the bright spot is a mystery. Credit: NASA, ESA, J. Parker (Southwest Research Institute), P. Thomas (Cornell University), and L. McFadden (University of Maryland, College Park)
And if you’re interested in looking back, here’s an archive to all the past Carnivals of Space. If you’ve got a space-related blog, you should really join the carnival. Just email an entry to [email protected], and the next host will link to it. It will help get awareness out there about your writing, help you meet others in the space community – and community is what blogging is all about. And if you really want to help out, sign up to be a host. Send an email to the above address.
The Rosetta stone, now displayed at the British Museum in London, was used by Jean-Francois Champollion to decipher Egyptian heiroglyphics, Credit: Hans Hillewaert, British Museum
On television and in the movies, it’s so easy. Aliens almost always speak English (at least in America they do). If it’s explained at all, we are typically told that they learned it by intercepting communications with our astronauts, or tapping into our television broadcasts. A universal translator device instantly abolishes communication difficulties. Hollywood aliens are, of course, human beings in costumes (these days augmented by computer graphics). They are equipped, as are we all, with a human brain, a human larynx, and human vocal cords; all singular products of the distinctive evolutionary history of our species.
Real extraterrestrials, if they exist, will be the product of a different evolutionary history, played out on another world.
They will know no human language, and be unfamiliar with the typical activities of human beings. Here on Earth no archeologist has ever deciphered an ancient script without knowing the language it corresponds to, even though such scripts deal with recognizable human activities. How could we ever devise a message that aliens could understand? Could we ever understand a message they sent to us? Communicating with alien minds may be one of the most daunting challenges the human intellect has ever faced.
In mid-November, the SETI Institute in Mountain View, California sponsored an academic conference on the problem interstellar communication ‘Communicating across the Cosmos’. The conference drew 17 speakers from a variety of disciplines, including linguistics, anthropology, archeology, mathematics, cognitive science, radio astronomy, and art. In this final installment, we will search for clues to a solution to the daunting problem of making ourselves understood to an extraterrestrial civilization.
Conference presenter and archeologist Paul Wason believes that the history of archeology provides an important lesson for how we might devise a message that can be deciphered by extraterrestrials. In the early 19th century the French archeologist Jean-Francois Champollion solved one of the great riddles of his field by deciphering Egyptian hieroglyphics. The critical clue was provided by an artifact discovered in 1799 in an Egyptian town that Europeans called Rosetta. It became known as the Rosetta stone.
The stone contained the same inscription in three different scripts. One of them was Egyptian hieroglyphics, and another was Greek, which Champollion knew how to read. Champollion used the Greek to decipher the hieroglyphics. Could we use the same strategy to create a cosmic Rosetta stone? Like Wason, Carl Sagan also grasped the importance of the Rosetta stone, and discussed it extensively in his 1980’s book and television series Cosmos. To create a cosmic Rosetta stone, we would need a language to stand in the role of Greek. It would need to be known both to us, and to the aliens. Could there possibly be such a thing?
Many mathematicians and physical scientists involved in SETI believe that mathematical and physical concepts could play the needed role. According to mathematician and conference speaker Carl DeVito, the natural numbers (0, 1, 2, 3 …) are useful to humans in dealing with the cyclical processes that are a everywhere in nature, and probably arise universally in the minds of intelligent beings. Astronomers have strong evidence that the laws of physics and chemistry worked out in laboratories here on Earth hold everywhere in the universe. That being the case, they hope that humans and aliens share a common understanding of basic concepts in these fields. If this is so, then such concepts might play the same role that Greek did for Champollion. SETI pioneers Carl Sagan and Frank Drake, along with their collaborators, employed a rudimentary version of this strategy when they constructed the message encoded on the phonographic record launched into space in 1977 aboard the Voyager 1 and 2 spacecraft. These spacecraft hurtled into interstellar space following the completion of their missions to explore the outer solar system.
An image encoded on the phonographic record carried aboard Voyager 1 and 2, intended to communicate how humans symbolize basic mathematical concepts. The left side depicts how humans, in western culture, represent the natural numbers using binary code and Arabic numerals. The vertical lines indicate binary ‘1’, and the horizontal lines binary ‘0’. On the right, additional numerals are given, and the use of scientific notation, and the operations of addition, multiplication, and division are depicted. Credit: Frank DrakeAn image encoded on the Voyager record intended to communicate standards of time, mass, and length to an extraterrestrial viewer, using basic concepts in physics encoded symbolically. In the upper right corner, each circle symbolizes a hydrogen atom. The diagram as a whole symbolizes a transition of the spin state of the electron. This transition involves the emission of a microwave radio wave of wavelength 21 centimeters, which is symbolized on the right side of the diagram. Radio emissions produced by this transition occurring in clouds of hydrogen gas in interstellar space are well known to radio astronomers. The wavelength is used as the standard of length (1 L). The time that this transition takes to occur is used as the unit of time (1t) and the mass of a hydrogen atom (1 M) is used as the standard of mass. Various units of measurement used by humans are then defined in terms of these standards. The units are then used throughout the pictorial portion of the message to indicate masses, lengths and times. Credit: Frank Drake
Sagan, Drake, and their collaborators first used symbols in an attempt to communicate how humans represent the natural numbers using binary and base ten numerals. They used another set of symbols to depict some properties of the hydrogen atom, which they used to establish standards of distance and time. The distance and time standards were used repeatedly throughout the digital image portion of the message to specify the sizes and time scales depicted. The Voyager record included a greeting from then President Carter encoded as English text. Sagan, Drake, and their collaborators didn’t even attempt the monumental, and perhaps impossible, task of explaining President Carter’s text statement using their Rosetta stone.
Much like Wason and Sagan, computer scientist and conference presenter Kim Binsted, felt that the solution to interstellar communication lies in constructing a pidgin, a simplified version of a language developed to communicate between groups that share no language in common. She was doubtful though, that a cosmic Rosetta stone based on physics and math would let humans and aliens communicate about anything other than physics and math. It might never, for example, provide a way to convey the President’s good wishes. The hieroglyphics of the Rosetta stone were decipherable, in part, because they described the familiar human activities of an Egyptian pharaoh. Humans are clueless about what sorts of activities aliens typically engage in, and aliens are equally clueless about us. It’s hard to see how a Rosetta stone based on physics could bridge this sort of gap.
Philosophers Nicholas Rescher and Andre Kukla, neither of whom presented at the conference, have raised a more fundamental objection. They question whether extraterrestrials would use the same concepts to understand the physical and chemical world that we do. The concepts that modern western science uses to understand the physical world surely reflect the structure of that world. But they also reflect the history of our culture and the structure of our minds. Since aliens would differ from humans on both counts, it’s at least possible that their physical, and even their mathematical concepts might be different from ours. If that’s so, then physics can’t play the role that Greek did for Champollion. Every path forward is full of unknowns and difficulties, and Kim Binsted doubts a solution is possible.
There is a glimmering of hope for another kind of Rosetta stone based on another sort of “Greek”. Given the central role that visual images played in the Voyager message, it’s surprising that image based communication strategies didn’t receive greater emphasis at the conference. It’s true that here on Earth; animals have evolved a wide variety of non-visual ways to sense their surroundings. Some fishes can sense their environments by generating and detecting electric fields in the water. Many fish can use fields of water flow around their bodies to detect nearby objects. Bats, along with dolphins and whales, have evolved a sonar system, emitting sounds and analyzing their returning echoes. Scorpions can sense ground vibrations, elephants can hear sounds below the range of human hearing, and dogs have a remarkably acute sense of smell, to name just a few examples. Still, almost every Earthly animal has eyes of some sort.
Earthly evolution has invented vision several times, in different animal lineages. Vision is especially important for larger animals that live on land. This is because larger bodies can make larger eyes and larger eyes can give sharper vision and better light gathering abilities. Land environments are typically better lit than aquatic ones. Birds and mammals are the Earthly animals with the biggest and most sophisticated brains, and they also have the most acute vision.
Are alien environments likely to be well lit? Exoplanet hunters have focused their efforts on finding planets like the Earth, rocky terrestrial planets at the right distance from their star for temperatures to be in the range where water is a liquid. They have shown us that such worlds are fairly commonplace in the cosmos. The daytime surfaces of these exoplanets are likely to be flooded with visible light, just as is Earth. This light may be necessary for life on such a world, because most life on Earth depends on the energy of sunlight as trapped by green plants. For large, land dwelling animals in this kind of environment, vision provides more information, at a distance, than any other sense can. Since it evolved numerous times on Earth, it’s likely to do so elsewhere as well. With a lens at the front and a sheet of light sensing cells at the back, the eye of a squid is remarkably similar to our own. Squids are part of a group of animals called molluscs, which also includes slugs, snails, and shellfish. Molluscs are very distantly related to the vertebrates (animals with backbones, a group which includes humans). The most recent common ancestor of molluscs and vertebrates was a simple worm-like creature that lived more than 600 million years ago. The two groups have followed an independent course of evolution ever since. The fact that molluscs evolved complex brains and bodies along a different evolutionary path than vertebrates makes them a good model for understanding some of the ways in which extraterrestrials, with an entirely separate evolutionary history, might be different from or similar to us. One group of molluscs, the cephalopods, a group which includes squids, octopuses, and cuttlefish, have evolved the largest and most complex brains of any invertebrates. Despite their separate evolutionary origin, the eyes of cephalopods are remarkably similar to vertebrate eyes, a phenomenon known as convergent evolution. Evolution solved similar problems in similar ways. Perhaps, even on another planet, evolution solves similar problems in similar ways. If aliens, like cephalopods, have some visual similarities to us, then visual images may be useful in interstellar messages. Credit: Carl Chun Die Cephaloden
The human visual system gathers information about a three dimensional world of objects and surfaces, partly by using motion cues. We have the ability to represent that world in two dimensions, using images. Kim Binsted worried that an alien visual system might not be capable of making sense of pictures made by humans. This worry was a potent one for the stick figures and line drawings that played such a prominent role in the pioneering interstellar messages of the 70’s. Those kinds of depictions use abstract visual conventions that an alien viewer might find impossible to figure out. Today, though, we needn’t worry about stick figures, because the information revolution gives us the ability to send high definition video. Still, we can’t be sure what an alien visual system would make of imagery encoded with the human visual system in mind.
Video imagery may provide a promising complement or alternative to the abstractions of physics and chemistry as the “Greek” for a cosmic Rosetta stone. If the aliens live on a planet like Earth, with liquid water on its surface, then we will share a mutual familiarity with water’s many manifestations. Just like us, aliens will have seen rain and snow, oceans, rivers, lakes, ponds, clouds, fog, and rainbows. If they have a sense of hearing, over a range of sound frequencies at least somewhat similar to ours, they will have heard waves crashing on beaches, rain hitting the ground, gurgling brooks, and the splash of a pebble dropped into a pond. When the senses work together to confirm one another, the certainty of perceptual recognition is even greater.
An audio-video movie depicting the mutually familiar phenomena of water could be just the bridge we need to cross the gulf of mutual incomprehension. This splashy, gurgling “Greek” could be the key to helping the aliens understand our audio-visual and still images, and ultimately, our symbols. As with the Voyager record, a simpler symbol system would first be needed to communicate to the aliens about how to view and listen to the presentation. That might be a big stumbling block. In the case of Voyager, a stylus head for playing the record was included on the spacecraft, which made it simpler to explain how to play it. A Rosetta stone that led the extraterrestrials to an understanding of our images could provide a means of communication extending well beyond the topics of physics, chemistry, and math. Several conference participants felt that imagery might help to convey things about human altruism, cooperation, morality, and aesthetic sensibilities.
The main message of the ‘Communicating across the Cosmos’ conference is a recognition of just how hard the problem of making ourselves understood to aliens will be. Kim Binsted ended her talk on a faint note of optimism. Even if all else fails, she supposed, there is something we can still communicate to the aliens. She showed a slide of her home doorbell. When it rings, she said, it conveys the message that someone is there, and where they are. It shows intent to communicate, and a benign willingness to reveal one’s presence. Even if it can’t be interpreted, an interstellar message conveys the information that a doorbell conveys. That message, the message that someone is there, would still be of monumental importance. Even an interstellar message that can’t be deciphered still tells us what a doorbell tells us: that someone is there. Credit: Jim Kuhn
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