One of the most frequently misunderstood concepts in science is the reason for Earth’s seasons.
As we experience the September equinox today—anyone try to balance an egg yet?—we thought we’d offer a space-based view of what’s going on.
Around 6 a.m. local time each day, the Sun, Earth, and any geosynchronous satellite
form a right angle, affording a nadir (straight down) view of the
terminator, the edge between the shadows of nightfall and the sunlight
of dusk and dawn.
The shape of this line between night and day varies
with the seasons, which means different lengths of days and differing
amounts of warming sunshine.
(The line is actually a curve because the
Earth is round, but satellite images only show it in two-dimensions.)
The Spinning Enhanced Visible and Infrared Imager (SEVIRI) on EUMETSAT's
Meteosat-9 captured these four views of Earth from geosynchronous
acquired December 21, 2010 - September 20, 2011
acquired December 21, 2010download large winter solstice image (1 MB, JPEG, 3712x3712)
acquired March 20, 2011download large spring equinox image (1 MB, JPEG, 3712x3712)
acquired June 21, 2011download large summer solstice image (1 MB, JPEG, 3712x3712)
acquired September 20, 2011download large fall equinox image (1 MB, JPEG, 3712x3712)
acquired September 19, 2010 - September 19, 2011download high definition animation (23 MB, QuickTime)
The images show how sunlight fell on the Earth on December 21,
2010 (upper left), and March 20 (upper right), June 21 (lower left),
and September 20, 2011 (lower right).
Each image was taken at 6:12 a.m.
On March 20 and September 20, the terminator is a straight
north-south line, and the Sun is said to sit directly above the equator.
On December 21, the Sun resides directly over the Tropic of Capricorn
when viewed from the ground, and sunlight spreads over more of the
On June 21, the Sun sits above the Tropic of
Cancer, spreading more sunlight in the north and turning the tables on
The bulge of our spherical Earth blocks sunlight from the far
hemisphere at the solstices; that same curvature allows the Sun’s rays to spread over more area near the top and bottom of the globe.
Of course, it is not the Sun that is moving north or south through
the seasons, but a change in the orientation and angles between the
Earth and its nearest star.
The axis of the Earth is tilted 23.5 degrees relative to the Sun and the ecliptic plane.
The axis is tilted away from the Sun at the December solstice and
toward the Sun at the June solstice, spreading more and less light on
At the equinoxes, the tilt is at a right angle to the
Sun and the light is spread evenly.
The equinox and changing of the seasons occurs on September 23, 2011
at 9:05 a.m. Universal Time. (Our September image above is a few days
Equinox means "equal night" in Latin, capturing the idea that
daytime and nighttime are equal lengths everywhere on the planet.
is true of the Sun's presence above the horizon, though it does not
account for twilight, when the Sun's rays extend from beyond the horizon
to illuminate our gas-filled atmosphere.
Koen Olthuis (1971) "the Floating Dutchman" studied Architecture and Industrial Design at the Delft University of Technology.
In 2007 he was chosen as nr. 122 on the Time Magazine list of most influential people in the world due to the worldwide interest in water developments.
The French magazine Terra Eco chooses him as one of the 100 green persons that will change the world in 2011. In his vision today's designers are an essential part of the climate change generation and should start to enhance their perspective on urban components to become dynamic instead of static.
His solution called City Apps, are floating urban components that add a certain function to the existing static grid of a city.
Using existing urban water as building ground offers space for new density, offering worldwide opportunities for cities to respond flexibly to climate change and urbanization. The first city, in which this vision is being developed, is The Westland, near The Hague in Holland. This project incorporates both floating social housing, floating islands, and floating apartment buildings. In 2010, the government of the Maldives agreed to develop a floating city, floating islands, floating golf courses, floating hotels and a floating conference centre in a joint venture, as a solution to the problems caused by rising sea levels and also to encourage social and economic advancement. A sustainable future lies beyond the waterfront!
From schools at sea to a city that perpetually sails the oceans, is
climate change creating a bold new era of floating urban design?
Until the late 1980s, nestled behind the Yan Ma Tei breakwater in
Hong Kong's Causeway Bay, you could find tens of thousands of
boat-dwellers who formed a bustling, floating district.
were members of the Tanka community, and their ancestors were fishermen
who retreated from warfare on land to live permanently in their vessels.
Until the mid-20th century, these traditional outcasts were forbidden
even to step ashore.
The typhoon shelter was famous for its
restaurants' cuisine – including Under Bridge Spicy Crab – and it was a
nightlife hub, alive with mahjong games and hired singers.
sampan (flat boats) catered to the floating district's needs.
may seem like science fiction, but as rising sea levels threaten
low-lying nations around the world, neighbourhoods like this may become
Whereas some coastal cities
will double down on sea defences, others are beginning to explore a
solution that welcomes approaching tides.
What if our cities themselves
were to take to the seas?
Grocery store in Makoko, Lagos, Nigeria. Photograph: Devesh Uba
A floating village at London's Royal Docks has the official nod, and
Rotterdam has a Rijnhaven waterfront development experiment well under
Eventually, whole neighbourhoods of water-threatened land could be
given over to the seas.
After decades of speculation and small-scale
applications, the floating solution is finally enjoying political
momentum – and serious investment.
The immediate and most numerous victims of climate change are sure to be in the developing world. In Lagos, the sprawling slum of Makoko regularly suffers floods, and its stilted houses are shored up with each new inundation.
It's under threat of razing by authorities.
The Nigerian-born architect Kunlé Adeyemi
proposes a series of A-frame floating houses to replace the existing
As proof of concept, his team constructed a floating school for
Still, many buildings do not make a city: infrastructure
remains a problem here.
One solution would be to use docking stations
with centralised services, rather like hooking up a caravan to power,
water and drainage lines at a campground.
You could extend an
existing city like London into the water quite far before ever being
seriously challenged by infrastructure issues.
But some ideas for
floating life move well beyond the urban extension model.
In the 1960s,
futurist Buckminster Fuller designed a floating city, Triton, for
100,000 residents, and even had his plans approved by the US Navy. UK
designer Phil Pauley has updated Fuller's geodesic concept: a ring of
spherical modules, his SubBiosphere2 would float in fair weather, then submerge whenever the seas became rough.
architect Jacque Fresco, meanwhile, foresees a time when humans must
colonise the sea, to escape land made uninhabitable by overpopulation.
He has spent his career designing cities of the future, and himself
lives in a dome-shaped prototype. Fresco's floating city designs –
generally gear-shaped – prescribe the use of "memory metals". Compressed
into small cubes, they are easily towed out to sea, where they can be
snapped back to the size of buildings.
Sub-Biosphere 2 is a closed, self-sustaining underwater habitat designed by Phil Pauley
Mobility among the waves lends floating communities a degree of political independence. The Seasteading Institute,
founded by Patri Friedman (grandson of Milton), proposes a series of
floating villages, and claims to be in active negotiations with
potential host nations that would give the villages political autonomy.
Billed as a startup incubator for political systems, the aquatic
communities would serve as experiments in governance – and represent a
rejection of what Seasteaders see as big government intrusion.
The Seasteading Institute proposes a series of floating villages – and
claims to be in active negotiations with potential host nations.
Photograph: Seasteading Institute
In an implementation plan for these Seasteading cities
[pdf], the Dutch engineering firm DeltaSync has proposed a modular
It too would have movable parts, for gradual growth
and financing, and a dynamic geography: if new friends decide to be
neighbours, they could simply tow their houses together.
the villages would aggregate in protected waters.
Later, they would cut
ties with land altogether.
That's when all the trappings of civic life
would be either abandoned or reproduced in microcosm on the rafted
Many of the technical components of DeltaSync's plan are
well-trodden territory for engineers.
Platforms and mooring systems are
not so different from those required for large boats or oil rigs.
with reclaimed land, floating additions to city infrastructure are
becoming a regular part of municipal planning.
Airports are particularly
prime for floating: they essentially require a large platform that is
close to the destination city without being intrusive.
infrastructure solutions, they range from the well-tested to the
The abundant wind available at sea could power turbines.
Ocean thermal energy conversion could harness the temperature difference
between the surface and the depths – a process that also provides fresh
water as a byproduct.
DeltaSync even envisions residents cultivating
aquaculture in lieu of gardens, manufacturing their food requirements
from nutrients found in upwellings at the edge of continental shelves.
so-called "Blue Revolution" in aquaculture would be required for the oceans
to provide this level of sustenance.
(Even without cities at sea,
though, ocean harvesting may be our best hope, as land-based agriculture
faces salinated soils and a critical phosphorus shortage.)
Ooffshore eco-platforms : The Stewards of the Seas
untethered floating societies, it's not just physical infrastructure
that needs to be planned out – it's the social infrastructure, too.
Floating citizens still need jobs to do; they need to do their shopping
and educate their children.
When the worst happens, they need access to
A full-service floating city already exists for residents of The World,
a 644-foot yacht that continuously circles the planet.
2002, the ship contains 165 condominium spaces that sell for millions.
And it may soon be upstaged. Freedom Ship
would essentially be a mile-long flat-bottomed barge with a high-rise
building on top.
Weighing 3 million tonnes and with a top speed of 10
knots, the floating city would circle the globe every three years,
stopping 12 miles offshore at each port for a week at a time.
ferries would connect the 40,000 residents and 20,000 crew to the
mainland and bring back visitors.
"We won't just be visiting those
countries," says Freedom Ship director and executive vice president
"We anticipate those countries visiting us."
Ship's size – and its $11bn price tag – gives it a credibility problem.
But Gooch has "two or three irons in the fire in Asia" to secure his
team's capital for the three-year construction process.
It will be too
big for any existing shipyard to build, so the ship must be constructed
in pieces and – a familiar idea by now – towed out to be assembled at
Credibility problem? … the perpetually sailing Freedom Ship would
have enough room for 50,000 permanent residents.
The thriving Hong Kong sampan-dwelling community of Causeway Bay was
not to last.
There was no garbage or sewerage treatment system, and fire
constantly threatened the wooden structures.
Breakwaters that made up
the typhoon shelter also limited water circulation, leaving pollution to accumulate in the harbour.
The wastewater from the moored vessels combined with leaked sewer
discharge and storm drain runoff to create unsanitary living conditions.
When Tanka families were offered public housing
on land in the 1980s, most chose this option.
Now only a few
traditional sampans are left, used as ferries to take tourists to their
luxury yachts. Despite sewerage improvement schemes, E Coli levels
remain high, and tests show alarmingly high levels of tributyltin, a
toxic biocide, in the water.
If floating communities are the way of the
future, we will have to learn this lesson well: we can no longer simply
outrun our own refuse.
Untethering from land seems a big moment
for a floating city, akin to blasting off to colonise another planet.
reject our ancestral habitat to this degree seems like hubris.
could a group of people survive alone among the waves?
But it is a
fallacy to imagine we're self-sustaining even in our land-based
Many of our essential goods arrive by tanker anyway – a
sea-based location would be all the more convenient.
impractical utopias, floating cities could be every bit as integrated
into global society as the ones we already have on land.
All margins of ice sheet now unstable—and contributing to sea level rise
An international team of scientists has discovered that the last
remaining stable portion of the Greenland ice sheet is stable no more.
The finding, which will likely boost estimates of expected
global sea level rise in the future, appears in the March 16 issue of
the journal Nature Climate Change [DOI:10.1038/NCLIMATE2161].
The new result focuses on ice loss due to a major retreat of an
outlet glacier connected to a long “river” of ice—known as an ice
stream—that drains ice from the interior of the ice sheet.
Open water in northeast Greenland, where ice loss is accelerating.
Photo by Finn Bo Madsen, courtesy of The Ohio State University.
The Zachariae ice stream retreated
about 20 kilometers (12.4 miles) over the last decade, the researchers
For comparison, one of the fastest moving glaciers, the Jakobshavn ice stream in southwest Greenland, has retreated 35 kilometers (21.7 miles) over the last 150 years. Ice streams drain ice basins, the same way the Amazon River drains the very large Amazon water basin.
Zachariae is the largest ice stream in a drainage basin that covers 16
percent of the Greenland ice sheet—an area twice as large as the one
drained by Jakobshavn.
Composite photograph of a GNET GPS unit implanted in the southeastern Greenland bedrock.
Image by Dana Caccamise, courtesy of Ohio State University.
This paper represents the latest finding from GNET, the GPS network in Greenland that measures ice loss by weighing the ice sheet as it presses down on the bedrock.
“Northeast Greenland is very cold. It used to be considered the
last stable part of the Greenland ice sheet,” explained GNET lead
investigator Michael Bevis of
The Ohio State University. “This study shows that ice loss in the
northeast is now accelerating. So, now it seems that all of the margins
of the Greenland ice sheet are unstable.”
This map shows major ice drainages in Greenland, along with measured ice surface velocities.
The northeast Greenland ice stream (NEGIS) now appears to be retreating as rapidly, or perhaps more rapidly, than other parts of the ice sheet, including Jakobshavn Isbræ (JI), Helheim Glacier (HG) and Kangerdlugssuaq (KG).
Catchments for those regions are outlined on the map.
(Image credit: The Ohio State University, Natural History Museum of Denmark)
Historically, Zachariae drained slowly, since it had to fight
its way through a bay choked with floating ice debris.
Now that the ice
is retreating, the ice barrier in the bay is reduced, allowing the
glacier to speed up—and draw down the ice mass from the entire basin.
“This suggests a possible positive feedback mechanism whereby
retreat of the outlet glacier, in part due to warming of the air and in
part due to glacier dynamics, leads to increased dynamic loss of ice
upstream. This suggests that Greenland's contribution to global sea
level rise may be even higher in the future,” said Bevis, who is also
the Ohio Eminent Scholar in Geodynamics and professor of earth sciences at Ohio State.
Study leader Shfaqat Abbas Khan, a senior researcher at the National Space Institute at the Technical University of Denmark, said that the finding is cause for concern.
“The fact that the mass loss of the Greenland Ice Sheet has
generally increased over the last decades is well known,” Khan said,
“but the increasing contribution from the northeastern part of the ice
sheet is new and very surprising.”
GNET, short for “Greenland GPS Network,” uses the earth’s
natural elasticity to measure the mass of the ice sheet. As previous
Ohio State studies revealed, ice weighs down bedrock, and when the ice
melts away, the bedrock rises measurably in response.
More than 50 GNET
stations along Greenland’s coast weigh the ice sheet like a giant
They found that the northeast Greenland ice sheet lost about 10 billion tons of ice per year from April 2003 to April 2012.
According to previous measurements and aerial photographs, the
northeast Greenland ice sheet margin appeared to be stable for 25
Around that time, a string of especially warm summers
triggered increased melting and calving events, which have continued to
the present day.
A large calving event at the Zachariae glacier made the news in
May 2013, and Khan and his team witnessed and filmed a similar event in
This map shows difference from average wind speed across the Northern Hemisphere for January-February 2014. Blues indicate areas with wind speeds that were higher than the 1981-2010 average; browns indicate winds were lower than average.
In the North Atlantic, an unusually high number of hurricane-force storms have left splashes of dark blue off southeastern Greenland, Norway, Europe, and the western Mediterranean.
(Map credit: NOAA)
Increased ice flow in this region is particularly troubling,
Khan said, because the northeast ice stream stretches more than 600
kilometers (about 373 miles) into the center of the ice sheet, where it
connects with the heart of Greenland’s ice reservoir.
“This implies that changes at the margin can affect the mass
balance deep in the center of the ice sheet. Furthermore, due to the
huge size of the northeast Greenland ice stream, it has the potential of
significantly changing the total mass balance of the ice sheet in the
near future,” he added.
Bevis agreed: “The fact that this ice loss is associated with a
major ice stream that channels ice from deep in the interior of the ice
sheet does add some additional concern about what might happen.”
The Greenland ice sheet is thought to be one of the largest
contributors to global sea level rise over the past 20 years, accounting
for 0.5 millimeters of the current total of 3.2 millimeters of sea
level rise per year.
A great white shark
called Lydia is about to make history as the first of its species to be
seen crossing from one side of the Atlantic to the other.
The satellite-tagged 4.4m-long female is currently swimming
above the mid-Atlantic ridge - which marks a rough boundary line between
east and west.
Lydia was first tagged off Florida as part of the Ocearch scientific project.
The shark has travelled more than 30,500km (19,000 miles) since the tracking device was attached.
Dr Gregory Skomal, senior fisheries biologist
with Massachusetts Marine Fisheries, told BBC News: "No white sharks
have crossed from west to east or east to west."
Lydia is now roughly 1,600km (1,000 miles) from the coasts of
County Cork in Ireland and Cornwall in Britain, and nearly 4,800km
(3,000 miles) from Jacksonville, Florida, where she was tagged by scientists in March 2013.
Researchers are using a hydraulic platform to tag the sharks safely - including Lydia (pictured)
Dr Skomal explained: "Although Lydia is closer to Europe than
North America, she technically does not cross the Atlantic until she
crosses the mid-Atlantic ridge, which she has yet to do.
"She would be the first documented white shark to cross into the eastern Atlantic."
The mere act of tagging a great white shark (Carcharodon carcharias)
is a feat in itself.
The scientists have been using a custom-built
34,000kg (75,000lb) capacity hydraulic platform, operated from their
research vessel the M/V Ocearch, to safely lift mature sharks so that
researchers can tag and study them.
Lydia is over the underwater mountain system
known as the Mid-Atlantic ridge and is now roughly 1,600km (1,000 miles)
away from the British Isles see Ocearch shark tracker
The Ocearch project was initiated to gather data on the movements,
biology and health of sharks for conservation purposes as well as for
public safety and education.
Though Lydia's journey is impressive, the sharks are known for their marathon migrations of thousands of kilometres.
A great white nicknamed Nicole travelled from South Africa to Australia and back - a circuit of more than 20,000km (12,400 miles) - over a period of nine months between November 2003 and August 2004.
As for where Lydia might go next, Dr Skomal explained: "We
have no idea how far she will go, but Europe, the Med, and the coast of
Africa are all feasible."
BBC : Transatlantic great white shark 'may be pregnant'
Wired : Spending 15 minutes with a great white shark on a boat deck
Soft robots — which don’t just have soft exteriors but are also powered
by fluid flowing through flexible channels — have become a sufficiently
popular research topic that they now have their own journal, Soft Robotics.
In the first issue of that journal, out this month, MIT researchers
report the first self-contained autonomous soft robot capable of rapid
body motion: a “fish” that can execute an escape maneuver, convulsing
its body to change direction in just a fraction of a second, or almost
as quickly as a real fish can.
“We’re excited about soft robots
for a variety of reasons,” says Daniela Rus, a professor of computer
science and engineering, director of MIT’s Computer Science and
Artificial Intelligence Laboratory, and one of the researchers who
designed and built the fish.
“As robots penetrate the physical world and
start interacting with people more and more, it’s much easier to make
robots safe if their bodies are so wonderfully soft that there’s no
danger if they whack you.”
Another reason to study soft robots,
Rus says, is that “with soft machines, the whole robotic planning
In most robotic motion-planning systems, avoiding
collisions with the environment is the highest priority.
leads to inefficient motion, because the robot has to settle for collision-free trajectories that it can find quickly.
soft robots, collision poses little danger to either the robot or the
“In some cases, it is actually advantageous for these
robots to bump into the environment, because they can use these points
of contact as means of getting to the destination faster,” Rus says.
the new robotic fish was designed to explore yet a third advantage of
soft robots: “The fact that the body deforms continuously gives these
machines an infinite range of configurations, and this is not achievable
with machines that are hinged,” Rus says.
The continuous curvature of
the fish’s body when it flexes is what allows it to change direction so
“A rigid-body robot could not do continuous bending,” she says.
robotic fish was built by Andrew Marchese, a graduate student in MIT’s
Department of Electrical Engineering and Computer Science and lead
author on the new paper, where he’s joined by Rus and postdoc Cagdas D.
Each side of the fish’s tail is bored through with a long, tightly
Carbon dioxide released from a canister in the
fish’s abdomen causes the channel to inflate, bending the tail in the
Each half of the fish tail has just two
control parameters: the diameter of the nozzle that releases gas into
the channel and the amount of time it’s left open.
Marchese found that the angle at which the fish changes direction —
which can be as extreme as 100 degrees — is almost entirely determined
by the duration of inflation, while its speed is almost entirely
determined by the nozzle diameter.
That “decoupling” of the two
parameters, he says, is something that biologists had observed in real
“To be honest, that’s not something I designed for,”
Marchese says. “I designed for it to look like a fish, but we got the
same inherent parameter decoupling that real fish have.”
That points to yet another possible application of soft robotics, Rus
says, in biomechanics.
“If you build an artificial creature with a
particular bio-inspired behavior, perhaps the solution for the
engineered behavior could serve as a hypothesis for understanding
whether nature might do it in the same way,” she says.
Marchese built the fish in Rus’ lab, where other researchers are working on printable robotics.
He used the lab’s 3-D printer to build the mold in which he cast the
fish’s tail and head from silicone rubber and the polymer ring that
protects the electronics in the fish’s guts.
A new flexible robotic fish is the first soft robot
with an onboard power source that can move its body at high speed
The long haul
fish can perform 20 or 30 escape maneuvers, depending on their velocity
and angle, before it exhausts its carbon dioxide canister.
comparatively simple maneuver of swimming back and forth across a tank
drains the canister quickly.
“The fish was designed to explore
performance capabilities, not long-term operation,” Marchese says. “Next
steps for future research are taking that system and building something
that’s compromised on performance a little bit but increases
A new version of the fish that should be able to swim
continuously for around 30 minutes will use pumped water instead of
carbon dioxide to inflate the channels, but otherwise, it will use the
same body design, Marchese says.
Rus envisions that such a robot could
infiltrate schools of real fish to gather detailed information about
their behavior in the natural habitat.
“All of our algorithms and
control theory are pretty much designed with the idea that we’ve got
rigid systems with defined joints,” says Barry Trimmer, a biology
professor at Tufts University who specializes in biomimetic soft robots.
“That works really, really well as long as the world is pretty
predictable. If you’re in a world that is not — which, to be honest, is
everywhere outside a factory situation — then you start to lose some of
The premise of soft robotics, Trimmer says, is
that “if we learn how to incorporate all these other sorts of materials
whose response you can’t predict exactly, if we can learn to engineer
that to deal with the uncertainty and still be able to control the
machines, then we’re going to have much better machines.”
researchers’ robot fish “is a great demonstration of that principle,”
Trimmer says. “It’s an early stage of saying, ‘We know the actuator
isn’t giving us all the control we’d like, but can we actually still
exploit it to get the performance we want?’ And they’re able to show
that yes, they can.”
It's just a regular dive off the coast of Mozambique -- a dolphin pod here, a few kingfish there -- until a swarm (and we mean dozens!) of hammerhead sharks show up (01:24).
Here's what it's like to find yourself surrounded by hammerheads!
The distinctive-looking sharks are highly threatened by the fin trade, so it's special to see them converge in such large numbers.