Novel bacterial species found trapped in Greenland’s ice

A team of Penn State scientists has discovered a new ultra-small species of bacteria that has survived for more than 120,000 years within the ice of a Greenland glacier at a depth of nearly two miles. The microorganism’s ability to persist in this low-temperature, high-pressure, reduced-oxygen and nutrient-poor habitat makes it particularly useful for studying how life, in general, can survive in a variety of extreme environments on Earth and possibly elsewhere in the solar system. 

The work will be presented by Jennifer Loveland-Curtze, a senior research associate in the laboratory led by Jean Brenchley, professor of biochemistry and molecular biology at Penn State, at 10:30 a.m. June 3 at the 108th American Society for Microbiology General Meeting in Boston. (Extreme Environments-I, poster N-156).

This new species is among the ubiquitous, yet mysterious, ultra-small bacteria, which are so tiny that the cells are able to pass through microbiological filters. In fact, some species have been found living in the ultra-purified water used for dialysis. “Ultra-small cells could be unknown contaminants in media and medical solutions that are thought to have been sterilized using filters,” said Loveland-Curtze.

The ultra-small size of the new species could be one explanation for why it was able to survive for so long in the Greenland glacier. Called Chryseobacterium greenlandensis, the species is related genetically to certain bacteria found in fish, marine mud and the roots of some plants. The organism is one of only about 10 scientifically described new species originating from polar ice and glaciers.

To study the bacterium in the laboratory, the research team, which also includes Senior Research Associate Vanya Miteva, filtered the cells from melted ice and incubated them in the cold in low-nutrient, oxygen-free solutions. The scientists then characterized the genetic, physiological, biochemical and structural features of the species. The team hopes that its studies of this species, as well as others living in the Greenland glacier, will reveal more about how cells survive and how they may alter their biochemistry and physiology over time.

“Microbes comprise up to one-third or more of the Earth’s biomass, yet fewer than 8,000 microbes have been described out of the approximately 3,000,000 that are presumed to exist,” said Loveland-Curtze. “The description of this one species is a significant step in the overall endeavor to discover, cultivate and use the special features held by these organisms.”

This research was supported by the National Science Foundation, the United States Department of Energy, and the National Aeronautics and Space Administration.

Test offers a genetic excuse for laziness

A simple test could soon identify whether difficulty in getting out of bed in the morning is down to genes or pure laziness.

	Scientists say that some of us are night owls by nature

Scientists say that some of us are night owls by nature - late to rise and late to go to bed - while others are larks, genetically programmed to wake early.

They have developed a swab test that can identify a person’s natural tendency to wake early or late from cells collected from inside the cheek.

Discussions are under way with Boots to develop an over-the-counter version.

It raises the possibility of workers who are repeatedly late being asked by their bosses to take a test to show whether or not they have a genetic excuse. The test was demonstrated by researchers from the School of Medicine at Swansea University on visitors to the Cheltenham Science Festival.

“The novel technique we have developed at Swansea is entirely non-invasive, so we can use it at a public event,” explained Dr Sarah Forbes-Robertson, who worked on the project with Dr Adeel Siddiqui and Alison Baird. “Previously you needed to take blood sample. Our technique allows us to get a useable sample just by swabbing the inside of an individual’s cheek.”

The test can reveal the activity of a number of different genes that control the “natural” pattern of wake and sleep - the circadian rhythm.

One gene, known as Per2, is especially active at around 4am, and is associated with sleeping. Another, known as REV-ERB, seems to work in opposition to Per2, having its peak activity at around 4pm, and is thought to be associated with wakefulness.

Of her own patterns, Dr Forbes Robertson said: “My peak of Per2 - the ’sleep’ gene - is at 6am rather than at the usual 4am. So I really do have a genetic excuse for not being able to manage early morning meetings. To get a full and accurate picture of someone’s natural circadian rhythm you would need to take samples four hourly over a full day and night, and also look at all the genes involved.

“But by taking samples at 4pm and 5pm to assess the activity of the REV-ERB gene, we will be able to see if patterns of peak gene expression are shifted forwards or back in time from the norm of 4pm. If your peak is earlier than 4pm it would indicate that you are a natural early bird, if you peak later than 5pm then you are more of a night owl.”

Astronomy study proves mathematics theorem

A gravitational lens can do more than reveal details of the distant universe. In an unexpected collision of astrophysics and algebra, it seems that this cosmic mirage can also be used to peer into the heart of pure mathematics.

In a gravitational lens, the gravity of stars and other matter can bend the light of a much more distant star or galaxy, often fracturing it into several separate images (see image at right). Several years ago, Sun Hong Rhie, then at the University of Notre Dame in Indiana, US, was trying to calculate just how many images there can be.

It depends on the shape of the lens – that is, how the intervening matter is scattered. Rhie was looking at a lens consisting of a cluster of small, dense objects such as stars or planets. If the light from a distant galaxy reaches us having passed through a cluster of say, four stars, she wondered, then how many images might we see?

She managed to construct a case where just four stars could split the galaxy into 15 separate images, by arranging three stars in an equilateral triangle and putting a fourth in the middle.

Later, she found that a similar shape works in general for a lens made of n stars (as long as there are more than one), producing 5n - 5 images. She suspected that was the maximum number possible, but she couldn’t prove it.

At about the same time, two mathematicians were working on a seemingly unrelated problem. They were trying to extend one of the foundation stones of mathematics, called the fundamental theorem of algebra.

Algebraic roots

It governs polynomial equations, which involve a variable raised to powers. For example, the equation x³ + 4x - 3 = 0 is a polynomial of degree three – the highest power of x is x³.

The fundamental theorem of algebra, proved back in the 18^th century, says that a polynomial of degree n has exactly n solutions. (Though in general, the variable x has to be a complex number, involving the square root of -1.)

“The fundamental theorem of algebra has been a true beacon, where modern algebra started,” says Dmitry Khavinson of the University of South Florida in Tampa, US.

Khavinson and Genevra Neumann of the University of Northern Iowa in Cedar Falls, US, wanted to take this further, by looking at more complicated mathematical objects called rational harmonic functions. These involve one polynomial divided by another.

Upper limit

In 2004, they proved that for one simple class of rational harmonic functions, there could never be more than 5n - 5 solutions. But they couldn’t prove that this was the tightest possible limit; the true limit could have been lower.

It turned out that Khavinson and Neumann were working on the same problem as Rhie. To calculate the position of images in a gravitational lens, you must solve an equation containing a rational harmonic function.

When mathematician Jeff Rabin of the University of California, San Diego, US, pointed out a preprint describing Rhie’s work, the two pieces fell into place. Rhie’s lens completes the mathematicians’ proof, and their work confirms her conjecture. So 5n - 5 is the true upper limit for lensed images.

“This kind of exchange of ideas between math and physics is important to both fields,” Rabin told New Scientist.

Rhie no longer works in academia, having run out of funding. “I didn’t even bother to submit my papers to journals because I had been so much harassed by the referees [of earlier papers],” she told New Scientist. “I was new to gravitational lensing at that time. What I said and the way I said it must have been unfamiliar to the gravitational lensing experts.”

Spread out

Theoretically, the work is valid for any type of gravitational lens, but its practical applications are not yet clear. That’s because the objects in Rhie’s sample lens all lie in the same plane and are simple point sources, with nothing between them.

Actual gravitational lenses tend to be much more complicated, and can be made up of clusters of hundreds of galaxies. These are spread out over large regions of space and contain a lot of gas between and within individual galaxies.

And although there are gravitational lenses comprised of just a few stars or planets, they produce images that are too close together for present-day telescopes to resolve.

But such “microlensing” can reveal the existence of planets around other stars. And in the future, a technique called optical interferometry, which links together the observations of more than one telescope, might make it possible to see the multiple lensed images produced by the planets of another star system.

Company Unveils Hydrogen Hybrid Supercar: Available Fall 2008

Ronn Motors of Austin, Texas, yesterday unveiled what they’re calling “the key to a new generation of “green cars.” The company’s Chief Executive Officer, Ronn Maxwell, had this to say about it:

“What we are revealing today is an innovation in the automotive industry and demonstrates American ingenuity at a time of real need. We’re designing and building cars with performance components and unique styling with the objective of making the new environmentally friendly vehicle stand out with never before seen style and approximately 40 mpg plus efficiency.”

I recently featured this type of hydrogen-on-demand hybrid system in a Gas 2.0 post about potential fuel saving scam devices. At the end of that post I had to say that the jury was still out on these types of systems. There was plenty of back and forth from folks who felt that hydrogen hybrids were scams and those that claimed they had installed the devices and they actually worked.

If Ronn Motors has truly built it into a production supercar, and it works, that would kind of put the kibosh on any naysayers out there now, wouldn’t it? Not only would the development and production of this car validate the functionality of hydrogen hybrids, it also could spur a broader public interest and recognition of the technology.

As of right now, it’s only a test car and some of the quotes from Ronn executives suggest they haven’t actually installed a hydrogen generator into the vehicle yet. But as the Hydrogen Cars & Vehicles blog puts it: “Move over Bugatti, Lamborghini and Saleen, the Ronn Motors Scorpion is a supercar that will scoot 0 to 60 mph in 3.5 seconds and achieve 40 mpg, too.” I mean, if it’s true, this appears to be an awesome development.

Boeing Successfully Fires 25 kW Solid-State Lasers, Laser Weapons One Step Closer to Being a Reality

Boeing has just tested its new thin-disk laser, the most powerful solid-state laser ever made. It fires at over 25 kilowatts, with the scalability proven to go up to a 100 kilowatt laser in the coming years. A 100 kW laser would be the most powerful ever made, one that has a lot of challenges to overcome, including reducing the excess heat generated by such a powerful laser and maintaining the quality of the beam over distances. But even a 25 kW laser is extremely powerful. As the press release says, it “will damage, disable or destroy targets at the speed of light, with little to no collateral damage, supporting missions on the battlefield and in urban operations.” Hit the jump for the full release.

Boeing Fires New Thin-Disk Laser, Achieving Solid-State Laser Milestone

ST. LOUIS, June 03, 2008 — The Boeing Company [NYSE: BA] fired its new thin-disk laser system repeatedly in recent tests, achieving the highest known simultaneous power, beam quality and run time for any solid-state laser to date.

In each laser firing at Boeing’s facility in West Hills, Calif., the high-energy laser achieved power levels of over 25 kilowatts for multi-second durations, with a measured beam quality suitable for a tactical weapon system. The Boeing laser integrates multiple thin-disk lasers into a single system. Through these successful tests, the Boeing team has proven the concept of scalability to a 100-kilowatt-class system based on the same architecture and technology.

“Solid-state lasers will revolutionize the battlefield by giving the warfighter an ultra-precision engagement capability that can dramatically reduce collateral damage,” said Scott Fancher, vice president and general manager of Boeing Missile Defense Systems. “These successful tests show that Boeing has made solid progress toward making this revolutionary capability a reality.”

The thin-disk laser is an initiative to demonstrate that solid-state laser technologies are now ready to move out of the laboratory and into full development as weapon systems. Solid-state lasers are powered by electricity, making them highly mobile and supportable on the battlefield. The Boeing laser represents the most electrically efficient solid-state laser technology known. The system is designed to meet the rapid-fire, rapid-retargeting requirements of area-defense, anti-missile and anti-mortar tactical high-energy laser systems. It is also ideal for non-lethal, ultra-precision strike missions urgently needed by warfighters in war zones.

“This accomplishment demonstrates Boeing’s commitment to advancing the state of the art in directed energy technology,” said Gary Fitzmire, vice president and program director of Boeing Directed Energy Systems. “These successful tests are a significant milestone toward providing reliable and supportable lasers to U.S. warfighters.”

Boeing’s approach incorporates a series of commercial-off-the-shelf, state-of-the-art lasers used in the automotive industry. These industrial lasers have demonstrated exceedingly high reliability, supportability and maintainability.

A high-power solid-state laser will damage, disable or destroy targets at the speed of light, with little to no collateral damage, supporting missions on the battlefield and in urban operations.

Physicists have ’solved’ mystery of levitation

Levitation has been elevated from being pure science fiction to science fact, according to a study reported today by physicists.

 

In theory the discovery could be used to levitate a person

In earlier work the same team of theoretical physicists showed that invisibility cloaks are feasible.

Now, in another report that sounds like it comes out of the pages of a Harry Potter book, the University of St Andrews team has created an ‘incredible levitation effects’ by engineering the force of nature which normally causes objects to stick together.

Professor Ulf Leonhardt and Dr Thomas Philbin, from the University of St Andrews in Scotland, have worked out a way of reversing this pheneomenon, known as the Casimir force, so that it repels instead of attracts.

Their discovery could ultimately lead to frictionless micro-machines with moving parts that levitate But they say that, in principle at least, the same effect could be used to levitate bigger objects too, even a person.

The Casimir force is a consequence of quantum mechanics, the theory that describes the world of atoms and subatomic particles that is not only the most successful theory of physics but also the most baffling.

The force is due to neither electrical charge or gravity, for example, but the fluctuations in all-pervasive energy fields in the intervening empty space between the objects and is one reason atoms stick together, also explaining a “dry glue” effect that enables a gecko to walk across a ceiling.

Now, using a special lens of a kind that has already been built, Prof Ulf Leonhardt and Dr Thomas Philbin report in the New Journal of Physics they can engineer the Casimir force to repel, rather than attact.

Because the Casimir force causes problems for nanotechnologists, who are trying to build electrical circuits and tiny mechanical devices on silicon chips, among other things, the team believes the feat could initially be used to stop tiny objects from sticking to each other.

Prof Leonhardt explained, “The Casimir force is the ultimate cause of friction in the nano-world, in particular in some microelectromechanical systems.

Such systems already play an important role - for example tiny mechanical devices which triggers a car airbag to inflate or those which power tiny ‘lab on chip’ devices used for drugs testing or chemical analysis.

Micro or nano machines could run smoother and with less or no friction at all if one can manipulate the force.” Though it is possible to levitate objects as big as humans, scientists are a long way off developing the technology for such feats, said Dr Philbin.

The practicalities of designing the lens to do this are daunting but not impossible and levitation “could happen over quite a distance”.

Prof Leonhardt leads one of four teams - three of them in Britain - to have put forward a theory in a peer-reviewed journal to achieve invisibility by making light waves flow around an object - just as a river flows undisturbed around a smooth rock.

Discovery of Earth-scale Exoplanet Signals Multitude of Planets in Universe

Astronomers have found the first Earth-sized exoplanet three thousand light years away.  The planet was discovered by the science-fiction-sounding method of gravitational microlensing, and shows that there might be far more planets out there than we ever suspected.

The planet is three times the size of Earth, which might sound like a fairly significant difference but you have to remember that in astronomical terms even being within a factor of ten is an amazing similarity.  Every other exoplanet yet discovered has been much larger, many times the size of our own solar system’s heavyweight gas giant Jupiter.  This is more to do with the sensitivity of our measurements than the makeup of the universe, however, which is where new tools and methods like the Microlensing Observations in Astrophysics (MOA) telescope-camera based in New Zealand come in.

Gravitational lensing was first used as a proof of general relativity, the idea that a massive object like a star bent space and light around it.  If two stars and the Earth are in precise alignment, the middle star will bend the light from the further star towards Earth, making it appear brighter than it otherwise would - that is to say, ‘lensing’ it.  Microlensing studies examine these images even more carefully and can reveal planets orbiting the lens star from minute variations in the focused light.

That’s exactly how the international team of scientists discovered the Earth-scale exoplanet, which you’d really think they’d give a snappier name than MOA-2007-BLG-192Lb.  It’s also interesting because of the star it orbits - which almost isn’t a star at all.  At 6-8% of the sun’s mass it’s tiny, far smaller than any star previously observed to host planets.  There is debate as to whether it can even support fusion reactions, or whether it’s a “brown dwarf” - a failed coulda-been star that never sparked into nuclear light and is now slowly trading internal energy for heat until it runs out and goes cold.

This great success in planetary survey techniques raises hopes for the discovery of many, many more planets - not only do we have an accurate and convincingly demonstrated technology, but it seems we have many more places to point it as well.

A survivor in Greenland: A novel bacterial species is found trapped in 120,000-year-old ice

A team of Penn State scientists has discovered a new ultra-small species of bacteria that has survived for more than 120,000 years within the ice of a Greenland glacier at a depth of nearly two miles. The microorganism’s ability to persist in this low-temperature, high-pressure, reduced-oxygen, and nutrient-poor habitat makes it particularly useful for studying how life, in general, can survive in a variety of extreme environments on Earth and possibly elsewhere in the solar system. The work will be presented by Jennifer Loveland-Curtze, a senior research associate in the laboratory led by Jean Brenchley, Professor of Biochemistry and Molecular Biology at Penn State, at the 108th American Society for Microbiology General Meeting in Boston, Massachusetts on 3 June 2008 at 10:30 a.m. (Extreme Environments-I, poster N-156).

Extruding a core: Scientists extrude the core from its barrel with the utmost care. Any butyl acetate on the core surface is carefully cleaned off before sawing the ice into…

This new species is among the ubiquitous, yet mysterious, ultra-small bacteria, which are so tiny that the cells are able to pass through microbiological filters. In fact, some species have been found living in the ultra-purified water used for dialysis. “Ultra-small cells could be unknown contaminants in media and medical solutions that are thought to have been sterilized using filters,” said Loveland-Curtze.

The ultra-small size of the new species could be one explanation for why it was able to survive for so long in the Greenland glacier. Called Chryseobacterium greenlandensis, the species is related genetically to certain bacteria found in fish, marine mud, and the roots of some plants. The organism is one of only about 10 scientifically described new species originating from polar ice and glaciers.

To study the bacterium in the laboratory, the research team, which also includes Senior Research Associate Vanya Miteva, filtered the cells from melted ice and incubated them in the cold in low-nutrient, oxygen-free solutions. The scientists then characterized the genetic, physiological, biochemical, and structural features of the species. The team hopes that its studies of this species, as well as others living in the Greenland glacier, will reveal more about how cells survive and how they may alter their biochemistry and physiology over time. “Microbes comprise up to one-third or more of the Earth’s biomass, yet fewer than 8,000 microbes have been described out of the approximately 3,000,000 that are presumed to exist,” said Loveland-Curtze. “The description of this one species is a significant step in the overall endeavor to discover, cultivate, and use the special features held by these organisms.”

Evolution on a chip

Researchers have created a computer-controlled system that harnesses ‘survival of the fittest’ to generate more efficient enzymes. The method has so far been used to improve an enzyme made of RNA, but could also be employed to study evolution in proteins, viruses and bacteria.

Scientists have previously demonstrated evolution in a test tube, and have used the technique to create molecules with novel or improved activity. A drug called Macugen, for example, which slows some types of vision loss, consists of an RNA molecule created in part by test-tube evolution. Industry scientists have also used the method to boost the activity of a herbicide-neutralizing enzyme and then used that enzyme to create herbicide-resistant plants.

The new method does the same, but under automated computer control. This means the experimental protocol can be followed more rigidly, without the sloppiness caused by human error. And the experiment can run and run tirelessly, giving the molecules more time to evolve. “What’s potentially really cool about it is the prospect of making the process automated and more rigorous,” says Robert Keenan, a biochemist at the University of Chicago in Illinois, who was not affiliated with the study. “It’s limitless what you could do.”

Fertile molecules

Biochemists Brian Paegel and Gerald Joyce of the Scripps Research Institute in La Jolla, California, demonstrated their system by improving the capability of an RNA enzyme to stitch itself to another RNA fragment.

Paegel and Joyce created a population of these RNA enzymes containing mutations at different sites. They then added protein enzymes that would copy any RNA fragments that had successfully sewn together. Joyce refers to such RNA fragments as ‘fertile’ because they are capable of being reproduced.

The researchers loaded their solution onto a chip with tiny chambers that hold minute amounts of liquid, which contained RNA fragments for the enzyme to stitch onto. A computer diluted the sample automatically when it reached a set concentration, supplying fresh liquid containing fewer and fewer RNA fragments. Over time, this meant that only those enzymes that were particularly efficient could continue to generate ‘fertile’ molecules in the RNA-poor environment.

After 500 rounds of growth and dilution, the solutions contained an enzyme that had accumulated 11 mutations and performed 90-times better than the starting molecule². The end result was unpredictable, says Joyce. Some of the mutations diminished enzyme performance on their own, but became advantageous when combined with other mutations.

Why stop at 500 iterations? Joyce gives two reasons. First, the researchers realized they were approaching a theoretical limit on enzyme performance. But the experiment was also nearing its 500th iteration the night that Trevor Hoffman, a baseball player for the San Diego Padres, earned his 500th ‘saved’ win. A local newspaper printed a picture of Padres celebrating on the field with a large screen behind him reading “Trevor Hoffman 500”. Joyce, a Padres fan, altered the image to read “On-Chip Dilutions 500”, posted it in his lab, and decided to stop the experiment there.

Precision control

Overall, the experiment is similar to one performed in Joyce’s lab more than a decade ago³, but automated control of the system represents a significant improvement, says Joyce. Manually diluting the solutions was a source of aggravation and error, he notes. “You’d grow and dilute, grow and dilute, but you didn’t know for sure what was going on in the tube,” he says. “You’d wonder: ‘Should I transfer it now? It’s about 10pm. I think I’ll just stick it in the freezer and pick this up again in the morning.’”

The chips will be useful for studying RNA evolution, agrees Jack Szostak of Harvard Medical School in Boston, Massachusetts. “This is great work,” he says. “It shows in a very clear way that a population of replicating sequences will inevitably evolve as more fit sequences arise.”

Although the system works well for RNA, Keenan notes that it will not address one of the most difficult steps in creating commercial enzymes: getting the enzyme to work in a living organism. Conditions in a test tube or on a chip are unlikely to replicate the environment of a human or a plant, he notes. “Sometimes you go to put your winning molecule in the plant and it just doesn’t work,” says Keenan.

But the method could aid the search for enzymes that do not exist in nature. In that case, says Keenan, generating an enzyme with any activity at all is a huge challenge. “If you can find any activity, then you’ve got your foot in the door,” he says.

Atomic rhythms give precise fix

In the late 18th Century, Captain Cook set out on a voyage of discovery clutching a pocket watch to help him keep track of his location.

The timepiece, which he described as “our faithful guide”, was accurate to a couple of seconds per month, and helped fix the position of his ship to a distance of two nautical miles.

Two hundred years later, the general principle of using clocks to aid navigation still stands. But the latest generation of timepiece, to be launched into space onboard the Giove-B satellite, is a world away from Captain Cook’s.

“Such a clock has never been flown,” Pierre Waller, an engineer at the European Space Agency (Esa), told BBC News.

The beating heart of Giove-B, the second test spacecraft for Europe’s Galileo global satellite-navigation system, is a hydrogen maser atomic clock.

Following its launch from the Baikonaur Cosmodrome in Kazakhstan, it will become the most precise time piece to orbit the Earth. It will be accurate to one billionth of a second per day, or one second in three million years.

On board Galileo - as with GPS - we have to take into account two different relativistic effects Pierre Waller Pros and cons of Europe’s ‘GPS’

By comparison, a typical wristwatch is accurate to about one second per day.

This precision is needed, say the scientists who built the system, because even tiny errors can cause sat-nav handsets to be way out.

A slip of just one second, for example, would produce location inaccuracies of around 300,000 km, approaching the distance from the Earth to the Moon.

If the technology is shown to be successful, it will be built into all 30 of Galileo’s operational satellites, eventually allowing users to pinpoint their location with an error of just one metre, compared to the several metres experienced with current GPS technology.

“Everything has been verified on the ground - on paper - but now we want to verify and validate all of these assumptions on board,” said Mr Waller.

“For me, this is really the challenge of Giove-B.”

Precise fix

The principles of satellite-navigation are well understood. Clocks are the core of all systems and are used to generate a time code which is continuously transmitted from the satellites.

“When you pick up that signal on the ground you can look at the time code [which] tells you when the satellite sent it out,” explained Dr Peter Whibberley, of the National Physical Laboratory (NPL) in the UK.

“If you measure its time of arrival against the clock in your receiver, you know how long that signal took to get to you.”

This allows the distance from receiver to satellite to be calculated.

“If you have three satellites in view, you can triangulate yourself on the surface of the Earth,” explained Dr Whibberley. A fourth satellite allows a precise fix.

“This whole process relies on satellites sending out very precisely timed signals.”

The more accurate the time signal, the more accurate the fix. And currently, the most accurate timepieces are atomic clocks.

Like conventional chronometers, these use a physical constant to measure the passing of time. But instead of the regular tick-tock of a pendulum, they use atoms switching between different energy states.

When an atom flips between a high and low energy state, it releases energy at a very precise frequency. Measuring this change and using it as an input into a counter produces an accurate measure of time.

The main clock onboard Giove-B uses hydrogen as an atomic source. This emits microwave radiation which is used as an input to “calibrate” a quartz crystal, similar to those found in a regular wristwatch.

“A clock is a generator of a periodic signal,” said Mr Waller. “Our periodic signal here is generated by quartz and we are using the [hydrogen] atoms to lock this quartz.”

Relative times

Although the resulting time signal is accurate to within one nanosecond a day, the fact that the satellite is orbiting the Earth at a height of 23,222km (14,430 miles), means the signal must be tweaked before it is relayed.

The more accurate the time signal, the more accurate the fix. And currently, the most accurate timepieces are atomic clocks.

Like conventional chronometers, these use a physical constant to measure the passing of time. But instead of the regular tick-tock of a pendulum, they use atoms switching between different energy states.

When an atom flips between a high and low energy state, it releases energy at a very precise frequency. Measuring this change and using it as an input into a counter produces an accurate measure of time.

The main clock onboard Giove-B uses hydrogen as an atomic source. This emits microwave radiation which is used as an input to “calibrate” a quartz crystal, similar to those found in a regular wristwatch.

“A clock is a generator of a periodic signal,” said Mr Waller. “Our periodic signal here is generated by quartz and we are using the [hydrogen] atoms to lock this quartz.”

Relative times

Although the resulting time signal is accurate to within one nanosecond a day, the fact that the satellite is orbiting the Earth at a height of 23,222km (14,430 miles), means the signal must be tweaked before it is relayed.

“The stability of the active maser is roughly one order of magnitude better,” explained Mr Waller. “But as a result the active maser is roughly five to 10 times heavier and bulkier.”

With weight and space at a premium onboard Giove-B, active maser technology was not an option.

In addition, the craft must pack two more atomic clocks into its chassis.

These back-up atomic chronometers use rubidium and are accurate to 10 nanoseconds per day.

One will be permanently running as a “hot” backup for the hydrogen maser, instantly taking over should it fail. The second rubidium clock will act as a so-called “cold” spare.

The final Galileo satellites will contain four clocks - two hydrogen masers and two which use rubidium.

This combination should ensure that the constellation, set to be up and running by the end of 2013, will offer uninterrupted and unparalleled accuracy on the ground.

In addition, it should improve the precision time services that have become so critical to economic activity, such as time-stamping of financial transactions and co-ordinating e-mail systems.

But soon even these clocks may be consigned to history alongside Captain Cook’s pocket watch.

Scientists at NPL are currently working on next-generation optical clocks, which use the frequency of light to help measure the passage of time.

“The basic principle is the same as the current generation of clocks,” explained Dr Whibberley.

However, using light allows a more stable clock to be built.

“They could be placed on satellites to give much more precise time keeping, and that promises even greater performance in positioning,” he said

“They could potentially be one hundred times more accurate.”

Satellite-navigation systems determine a position by measuring the distances to a number of known locations - the spacecraft constellation in orbit

In practice, a sat-nav receiver will capture atomic-clock time signals sent from the satellites and convert them into the respective distances

A sat-nav device will use the data sent from at least four satellites to get the very best estimate of its position - whether on the ground or in the sky

The whole system is monitored from the ground to ensure satellite clocks do not drift and give out timings that might mislead the user