Mount Etna on the Italian island of Sicily erupts again after exploding several times earlier this month. The caldera spewed out smoke and dust as lava poured from the most active volcano in Europe. It has been particularly active recently, after a new crater formed on the south eastern side of the mountain. Near-by residents were not in danger as this latest eruption continued. Report by Thomas Magill.
Offering new insights into our fragile polar regions, ESA’s CryoSat mission has provided three consecutive years of Arctic sea-ice thickness measurements, which show that the ice continues to thin.
Although satellites have witnessed a downward trend in the extent of sea ice over the last two decades, it is essential to have accurate information on the mass or volume of ice being lost. This is a more accurate measure of the changes taking place.
Along with observations of ice extent, CryoSat’s measurements of thickness now span from October 2010 to April 2013, allowing scientists to work out the real loss of ice, monitor seasonal change and identify trends.
“From the satellite’s measurements we can see that some parts of the ice pack ice have thinned more rapidly than others, but there has been a decrease in the volume of winter and summer ice over the past three years.
“The volume of the sea ice at the end of last winter was less than 15 000 cubic km, which is lower than any other year going into summer and indicates less winter growth than usual.”
While it seems unlikely that a record minimum of sea-ice extent will be set this September, the thinner ice at the start of summer could mean that the actual volume of ice may reach a new low.
Rachel Tilling, PhD student at University College London, who is working with the CryoSat data stated, “Readings from CryoSat in October, when the ice starts to refreeze, will confirm this either way.”
Moreover, scientists can look forward to a continued stream of this vital information from CryoSat for some time.
“CryoSat has been in orbit since 2010 and with the satellite still in excellent health it is now set to continue providing precision measurements until 2017,” said ESA’s Tommaso Parrinello, who is responsible for the mission.
Much of the success in the way the mission’s radar height measurements are exploited to understand ice change is thanks to Prof. Seymour Laxon from University College London who passed away in January as the result of an accident.
Light clocks A and B moving horizontally through space. According to length contraction, clock A should tick faster than clock B.
In a new study, scientists argue that there is no length contraction, and both clocks should tick at the same rate in accordance with special relativity.
Image credit: Sorli and Fiscaletti.
Philosophers have debated the nature of time long before Einstein and modern physics but in the 106 years since Einstein, the prevailing view in physics has been that time serves as the fourth dimension of space, an arena represented mathematically as 4D Minkowski spacetime.
In a new study, Sorli and Fiscaletti have shown that two phenomena of special relativity - time dilation and length contraction, can be better described within the framework of a 3D space with time as the quantity used to measure change (i.e., photon motion) in this space.
The scientists have published their article in a recent issue of Physics Essays. The work builds on their previous articles, in which they have investigated the definition of time as a “numerical order of material change.”
The main concepts of special relativity - that the speed of light is the same in all inertial reference frames, and that there is no absolute reference frame - are traditionally formulated within the framework of Minkowski spacetime.
In this framework, the three spatial dimensions are intuitively visualized, while the time dimension is mathematically represented by an imaginary coordinate, and cannot be visualized in a concrete way.
In their paper, Sorli and Fiscaletti argue that, while the concepts of special relativity are sound, the introduction of 4D Minkowski spacetime has created a century-long misunderstanding of time as the fourth dimension of space that lacks any experimental support.
They argue that well-known time dilation experiments, such as those demonstrating that clocks do in fact run slower in high-speed airplanes than at rest, support special relativity and time dilation but not necessarily Minkowski spacetime or length contraction.
According to the conventional view, clocks run slower at high speeds due to the nature of Minkowski spacetime itself as a result of both time dilation and length contraction.
But Sorli and Fiscaletti argue that the slow clocks can better be described by the relative velocity between the two reference frames, which the clocks measure, not which the clocks are apart of. In this view, space and time are two separate entities.
“With clocks we measure the numerical order of motion in 3D space,” Sorli reported. “Time is 'separated' from space in a sense that time is not a fourth dimension of space.
Instead, time as a numerical order of change exists in a 3D space. Our model on space and time is founded on measurement and corresponds better to physical reality.”
To illustrate the difference between the two views of time, Sorli and Fiscaletti consider an experiment involving two light clocks.
Each clock's ticking mechanism consists of a photon being reflected back and forth between two mirrors, so that a photon's path from one mirror to the other represents one tick of the clock.
The clocks are arranged perpendicular to each other on a platform, with clock A oriented horizontally and clock B vertically.
When the platform is moved horizontally at a high speed, then according to the length contraction phenomenon in 4D spacetime, clock A should shrink so that its photon has a shorter path to travel, causing it to tick faster than clock B.
But Sorli and Fiscaletti argue that the length contraction of clock A and subsequent difference in the ticking rates of clocks A and B do not agree with special relativity, which postulates that the speed of light is constant in all inertial reference frames.
They say that, keeping the photon speed the same for both clocks, both clocks should tick at the same rate with no length contraction for clock A.
They mathematically demonstrate how to resolve the problem in this way by replacing Minkowski 4D spacetime with a 3D space involving Galilean transformations for three spatial coordinates X, Y, and Z, and a mathematical equation (Selleri's formalism) for the transformation of the velocity of material change, which is completely independent of the spatial coordinates.
Video of Mock Discussion on Time and Space
Sorli explained that this idea that both photon clocks tick at the same rate is not at odds with the experiments with flying clocks and other tests that have measured time dilation. This difference, he says, is due to a difference between photon clocks and atom-based clocks.
“The rate of photon clocks in faster inertial systems will not slow down with regard to the photon clocks in a rest inertial system because the speed of light is constant in all inertial systems,” he said.
“The rate of atom clocks will slow down because the 'relativity' of physical phenomena starts at the scale of pi mesons.”
He also explained that, without length contraction, time dilation exists but in a different way than usually thought.
“Time dilatation exists not in the sense that time as a fourth dimension of space dilates and as a result the clock rate is slower,” he explained.
“Time dilatation simply means that, in a faster inertial system, the velocity of change slows down and this is valid for all observers.
GPS confirms that clocks in orbit stations have different rates from the clocks on the surface of the planet, and this difference is valid for observers that are on the orbit station and on the surface of the planet.
So interpreted, 'time dilatation' does not require 'length contraction,' which as we show in our paper leads to a contradiction by the light clocks differently positioned in a moving inertial system.”
He added that the alternative definition of time also agrees with the notion of time held by the mathematician and philosopher Kurt Gödel.
“The definition of time as a numerical order of change in space is replacing the 106-year-old concept of time as a physical dimension in which change runs,” Sorli said.
“We consider time being only a mathematical quantity of change that we measure with clocks. This is in accord with a Gödel view of time.
By 1949, Gödel had produced a remarkable proof: 'In any universe described by the theory of relativity, time cannot exist.'
Our research confirms Gödel's vision: time is not a physical dimension of space through which one could travel into the past or future.”
In the future, Sorli and Fiscaletti plan to investigate how this view of time fits with the broader surroundings.
They note that other researchers have investigated abolishing the idea of spacetime in favour of separate space and time entities, but often suggest that this perspective is best formulated within the framework of an ether, a physical medium permeating all of space.
In contrast, Sorli and Fiscaletti think that the idea can be better modeled within the framework of a 3D quantum vacuum.
Rather than viewing space as a medium that carries light, light's propagation is governed by the electromagnetic properties (the permeability and permittivity) of the quantum vacuum.
“We are developing a mathematical model where gravity is a result of the diminished energy density of a 3D quantum vacuum caused by the presence of a given stellar object or material body,” Sorli said.
"Inertial mass and gravitational mass have the same origin: diminished energy density of a quantum vacuum."
"This model gives exact calculations for the Mercury perihelion precession as calculations of the general theory of relativity.”
More information: Amrit Sorli and Davide Fiscaletti. “Special theory of relativity in a three-dimensional Euclidean space.” Physics Essays: March 2012, Vol. 25, No. 1, pp. 141-143. DOI: 10.4006/0836-1398-25.1.141
La Niña continues to strengthen in the Pacific Ocean, as shown in the latest satellite data of sea surface heights from the NASA/European Ocean Surface Topography Mission/Jason-2 satellite.
The image is based on the average of 10 days of data centred on Sept. 3, 2010. Higher (warmer) than normal sea surface heights are indicated by yellows and reds, while lower (cooler) than normal sea surface heights are depicted in blues and purples.
Green indicates near-normal conditions. According to NASA climatologist Bill Patzert "This La Niña could deepen the drought in the already parched Southwest and could also worsen conditions that have fuelled Southern California's recent deadly wildfires"
Anchovy, the most fished species in the world, is at historic highs in Peru that may be short-lived due to climate change and overfishing.
Peru's fleet can catch around 20,000 tonnes each day in a four-kilometer (2.48-mile) radius.
In contrast, a European zone where a ban is in effect through at least 2010, the catch level has been set at between 20,000 and 30,000 tonnes of adult anchovy.
For the past four years, anchovy stock has enjoyed protected status in the Bay of Biscay along the western coast of France and the northern coast of Spain.
In Peru's Pacific fringe, fed by cold, rich waters of the low-salinity Humboldt Current, the Peruvian anchoveta -- Engraulis ringens -- is king.
With some six to eight million tonnes fished each year, the Andean country and its 2,800 kilometers (1,740 miles) of coastland reap the lion's share of the tiny fish, ahead of Chile's one million tonnes annually.
Anchovies, which measure 12 to 19 centimeters (4.7 to 7.5 inches) as adult fish, account for eight percent of global catch, including all species and types of water.
But a study by the Peruvian Marine Research Institute (IMARPE) late last year found that anchovies were not always so abundant in Peru, where they were scarce four centuries ago.
During this mini-ice age, a slight drop in temperature that lasted from around 1400 to 1820, warmer water conditions paradoxically prevailed in the Humboldt ecosystem, explained researchers led by marine biologist Dimitri Gutierrez.
There were less cold water currents and thus less anchovies.
"We can of course think that one day, we will fall back into unproductive conditions, that everything could fall apart," said Arnaud Bertrand, oceanographer at Lima's Research Institute for Development.
Climate change has already made a dent on this portion of the Pacific Ocean, where 10 percent of global fishing takes place on less than one percent of its surface.
In 1972-73 and then 1981-82, aggressive cycles of the El Nino weather phenomenon -- which causes abnormal warming of the Pacific Ocean -- coupled with overfishing of up to 12 million tonnes per year led to a collapse of the anchovy stock and industry.
Studies have shown that civilizations that prospered along this deserted coastline thanks to maritime resources have come and gone according to major climate variations.
The Caral-Supe civilization, the earliest known urban settlement in the Americas, thus thrived for nearly 1,500 years until some 3,500 years ago.
Peru, which produces half of the world's fish flour -- pulverized fish protein, is now taking steps to protect its precious resource.
It is reducing its fishing fleet to 1,400 boats, adjusting its fishing practices, as well as closely following catches and scientific observations.
This year, Peru imposed individual quotas per boat and on the amount of fish that can be netted over several days. It is part of a move to respond to warming that tends to take place in oceanic zones lacking oxygen.
Betrand noted that despite accounting for the biggest stock in the world, anchovies are seldom used for human food, crushed instead into a fine flour to make animal feed for fowl, pigs and farm-raised fish.
Buzz Lightyear returns to Earth aboard space shuttle Discovery, after spending 15 months aboard the International Space Station. 
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