Canadian Geese. Image take near Lakeview, OR. Image from: Bureau of Land Management
A new study conducted by researchers EricVaillancourt andJean-MichelWeber at the University of Ottawa examined blood sugar regulation in a bird that specialize in long distance migration, the Canada goose (Branta canadensis, image above). As referenced in the study published in the American Journal of Physiology – Regulatory, Integrative and Comparative Physiology, Canadian geese migrate approximately 7,000 km on their way to the Arctic, a trip that includes non-stop flights of up to 1,000 km at a time.
Map of Canadian goose migration from the Wisconsin Sea Grant.
Maintaining normal blood sugar levels in humans requires the effects of two hormones that act in opposition to each other: insulin which decreases blood sugar after a meal and glucagon that ensures blood sugar does not drop too low during fasting. Glucagon is also important in blood sugar regulation during prolonged fasting in birds. A new study examined the effects of glucagon in migratory Canadian geese. Administering glucagon to the birds increased the mobilization of glucose by 50% resulting in 90% higher blood glucose concentrations. These findings suggest that during prolonged fasting associated with migration, glucagon may function to ensure glucose homeostastis in Canadian geese.
Source:
Vaillancourt E, Weber J-M. Fuel metabolism in Canada geese: effects of glucagon on glucose kinetics. American Journal of Physiology – Regulatory, Integrative and ComparativePhysiology.Published 24 June 2015Vol.no. ,DOI: 10.1152/ajpregu.00080.2015
from ScienceBlogs http://ift.tt/1Lz9smc
Canadian Geese. Image take near Lakeview, OR. Image from: Bureau of Land Management
A new study conducted by researchers EricVaillancourt andJean-MichelWeber at the University of Ottawa examined blood sugar regulation in a bird that specialize in long distance migration, the Canada goose (Branta canadensis, image above). As referenced in the study published in the American Journal of Physiology – Regulatory, Integrative and Comparative Physiology, Canadian geese migrate approximately 7,000 km on their way to the Arctic, a trip that includes non-stop flights of up to 1,000 km at a time.
Map of Canadian goose migration from the Wisconsin Sea Grant.
Maintaining normal blood sugar levels in humans requires the effects of two hormones that act in opposition to each other: insulin which decreases blood sugar after a meal and glucagon that ensures blood sugar does not drop too low during fasting. Glucagon is also important in blood sugar regulation during prolonged fasting in birds. A new study examined the effects of glucagon in migratory Canadian geese. Administering glucagon to the birds increased the mobilization of glucose by 50% resulting in 90% higher blood glucose concentrations. These findings suggest that during prolonged fasting associated with migration, glucagon may function to ensure glucose homeostastis in Canadian geese.
Source:
Vaillancourt E, Weber J-M. Fuel metabolism in Canada geese: effects of glucagon on glucose kinetics. American Journal of Physiology – Regulatory, Integrative and ComparativePhysiology.Published 24 June 2015Vol.no. ,DOI: 10.1152/ajpregu.00080.2015
A view of Comet 67P/Churyumov-Gerasimenko from Rosetta, showing the spacecraft’s huge solar panels. This “selfie” was actually taken by Philae while still attached on Sep. 7, 2014. Image credit: ESA/Rosetta/Philae/CIVA
Space scientists’ joy at renewing contact with their comet lander Philae has turned to frustration over efforts to establish a stable connection between the probe and its mothership Rosetta.
Since Philae phoned home on June 13 for the first time after losing power last November, communications have been intermittent. Confirmed contacts have occurred during seven spells on June 14, 19, 20, 21, 23, and 24 but have not been enough to allow a useful exchange of data.
Reporting on the European Space Agency’s (ESA) Rosetta blog, space science editor Emily Baldwin says that contact on June 19, for example, was stable but split into two periods lasting just two minutes each. A link on June 23 lasted only 20 seconds and was unstable. The following day, a 20-minute link was established, but the quality was patchy, allowing just 80 packets of telemetry to be received.
Part of the problem is the geometry of the two spacecraft as they study Comet 67P/Churyumov-Gerasimenko. Rosetta is orbiting the comet, but the comet itself is also rotating with a period of 12.4 hours, which means that Philae’s landing site is not always in view of Rosetta. The comet’s rotation also means that there are periods when Philae is out of sunlight and so failing to generate enough power via its solar panels to communicate.
Computer models of how the comet is rotating beneath Rosetta suggest to the mission team that there should be windows during which they achieve contact between the mothership and Philae lasting between a few tens of minutes and up to three hours. The dream situation at such times would be for Philae to be powered-up and listening for Rosetta, establishing a link and then transmitting data, with a minimum contact period lasting at least 50 minutes. Dr Baldwin explains that the lander holds two mass memories and it takes about 20 minutes to send the contents of each to the orbiter.
The situation is not helped by the need to keep Rosetta at a greater “safe” distance from Comet 67P at the moment as it becomes more active, warmed by the Sun and spraying jets of gas and dust on its approach to perihelion, the innermost point in its elliptical orbit through the Solar System, on Aug. 13. This greater distance means that Philae’s signal is much weaker than it would otherwise be. How the orbiter is oriented in space, and thus the way its antenna is pointed, can also affect communications.
View larger. | The Philae Lander against black space just off the comet’s surface during the first bounce off Comet 67P/Churyumov–Gerasimenko. Image via ESA ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.
Because the mission scientists are unable to make any changes to Philae at present, their efforts are being focused on changing the orbit and orientation of Rosetta itself, while keeping the spacecraft’s safety the top priority. Its trajectory currently carries it over the comet’s terminator—the boundary between the lit and unlit sides. The ground track of this orbit is being shifted from +55° on June 24 to -8° on June 26, because better quality signals have been received when Rosetta was flying at lower latitudes. Following the landing in November, Rosetta was flying between latitudes of +15° to +25°, and Rosetta will gradually move northwards again from its -8° point to allow mission controllers to assess when it is at its optimum position.
ESA’s Rosetta team is working closely with the Lander Control Centre at the German Aerospace Center (DLR) in Cologne, and the Lander Science Operations and Navigation Centre at the French space agency (CNES) in Toulouse to try to establish a useful and reliable link with Philae again.
Dr. Stephan Ulamec, Philae Project Manager at DLR, told Sen:
We are still trying hard to get longer and stable RF link between Lander and Orbiter.
A view of Comet 67P/Churyumov-Gerasimenko from Rosetta, showing the spacecraft’s huge solar panels. This “selfie” was actually taken by Philae while still attached on Sep. 7, 2014. Image credit: ESA/Rosetta/Philae/CIVA
Space scientists’ joy at renewing contact with their comet lander Philae has turned to frustration over efforts to establish a stable connection between the probe and its mothership Rosetta.
Since Philae phoned home on June 13 for the first time after losing power last November, communications have been intermittent. Confirmed contacts have occurred during seven spells on June 14, 19, 20, 21, 23, and 24 but have not been enough to allow a useful exchange of data.
Reporting on the European Space Agency’s (ESA) Rosetta blog, space science editor Emily Baldwin says that contact on June 19, for example, was stable but split into two periods lasting just two minutes each. A link on June 23 lasted only 20 seconds and was unstable. The following day, a 20-minute link was established, but the quality was patchy, allowing just 80 packets of telemetry to be received.
Part of the problem is the geometry of the two spacecraft as they study Comet 67P/Churyumov-Gerasimenko. Rosetta is orbiting the comet, but the comet itself is also rotating with a period of 12.4 hours, which means that Philae’s landing site is not always in view of Rosetta. The comet’s rotation also means that there are periods when Philae is out of sunlight and so failing to generate enough power via its solar panels to communicate.
Computer models of how the comet is rotating beneath Rosetta suggest to the mission team that there should be windows during which they achieve contact between the mothership and Philae lasting between a few tens of minutes and up to three hours. The dream situation at such times would be for Philae to be powered-up and listening for Rosetta, establishing a link and then transmitting data, with a minimum contact period lasting at least 50 minutes. Dr Baldwin explains that the lander holds two mass memories and it takes about 20 minutes to send the contents of each to the orbiter.
The situation is not helped by the need to keep Rosetta at a greater “safe” distance from Comet 67P at the moment as it becomes more active, warmed by the Sun and spraying jets of gas and dust on its approach to perihelion, the innermost point in its elliptical orbit through the Solar System, on Aug. 13. This greater distance means that Philae’s signal is much weaker than it would otherwise be. How the orbiter is oriented in space, and thus the way its antenna is pointed, can also affect communications.
View larger. | The Philae Lander against black space just off the comet’s surface during the first bounce off Comet 67P/Churyumov–Gerasimenko. Image via ESA ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.
Because the mission scientists are unable to make any changes to Philae at present, their efforts are being focused on changing the orbit and orientation of Rosetta itself, while keeping the spacecraft’s safety the top priority. Its trajectory currently carries it over the comet’s terminator—the boundary between the lit and unlit sides. The ground track of this orbit is being shifted from +55° on June 24 to -8° on June 26, because better quality signals have been received when Rosetta was flying at lower latitudes. Following the landing in November, Rosetta was flying between latitudes of +15° to +25°, and Rosetta will gradually move northwards again from its -8° point to allow mission controllers to assess when it is at its optimum position.
ESA’s Rosetta team is working closely with the Lander Control Centre at the German Aerospace Center (DLR) in Cologne, and the Lander Science Operations and Navigation Centre at the French space agency (CNES) in Toulouse to try to establish a useful and reliable link with Philae again.
Dr. Stephan Ulamec, Philae Project Manager at DLR, told Sen:
We are still trying hard to get longer and stable RF link between Lander and Orbiter.
On Thursday June 25 forty groups around the country delivered 25,000 petition signatures calling on Hyundai to support good jobs throughout its supply chain. Altogether, about 25 national, state and local organizations—unions, the faith community, community groups, health and safety advocates (COSH groups), student groups and others—participated in the delegations to support workers who are organizing to form their union with the United Auto Workers (UAW).
SoCal COSH and delegation at Hyundai headquarters in Fountain Valley, CA
Workers at Lear Corporation, a Hyundai supplier in Selma, AL, have reported severe and disabling health effects from exposure to isocyanates (toluene diisocyanate (TDI)) while manufacturing car seats. Alarms that signal dangerous levels of the toxic chemical TDI in the air are frequent. Hyundai needs to take responsibility for the working conditions of companies in its supply chain. Lear ignored safety issues to the point that the OSHA stepped in on three separate occasions (e.g., here) to cite the company for breaking health and safety laws.
When one of the workers at the Selma plant—Kimberly King, who suffers from asthma she developed while working with these chemicals at the plant—joined a community delegation this spring to the Hyundai plant in Montgomery AL, Lear fired her, then sued her. A federal court slapped Lear with a restraining order and preliminary injunction, but Kim’s fight to get her job back—and, above all, to make these good, safe, family-sustaining jobs —continues. Workers at the plant make around $12 per hour.
Hyundai has the power to step in and tell Lear to make things right.
Student groups, the AFL-CIO young worker councils, and COSH groups were especially important in getting out the message that all workers deserve fair wages and safe conditions. The delegations delivered a letter from United Students Against Sweatshops reporting that the average starting wage for a job at a Hyundai supplier in the Montgomery, AL, area is just $9.07 per hour, and that three-quarters of those employers hire exclusively through temporary staffing agencies. One shocked dealership manager remarked, “Those are McDonald’s wages!” National COSH and affiliates have highlighted how dangerous TDI and other isocyanate chemicals are to workers and the need to have corporations raise the bar for better safety conditions.
Workers in Selma and elsewhere are fighting to be protected from toxic chemical exposure for all workers. The public needs to know that corporations like Hyundai must step up to the plate and insist that their parts supply chains provide safe and healthy workplaces. Customers need to know that buying a Hyundai car is a vote against social justice if the company refuses to be responsible to workers.
Peter Dooley CSP, CIH is a workplace health and safety consultant with thirty five years of experience in safety inspections, fatality investigations, worker education and other related aspects.
from ScienceBlogs http://ift.tt/1LyC8vP
by Peter Dooley, CSP, CIH
On Thursday June 25 forty groups around the country delivered 25,000 petition signatures calling on Hyundai to support good jobs throughout its supply chain. Altogether, about 25 national, state and local organizations—unions, the faith community, community groups, health and safety advocates (COSH groups), student groups and others—participated in the delegations to support workers who are organizing to form their union with the United Auto Workers (UAW).
SoCal COSH and delegation at Hyundai headquarters in Fountain Valley, CA
Workers at Lear Corporation, a Hyundai supplier in Selma, AL, have reported severe and disabling health effects from exposure to isocyanates (toluene diisocyanate (TDI)) while manufacturing car seats. Alarms that signal dangerous levels of the toxic chemical TDI in the air are frequent. Hyundai needs to take responsibility for the working conditions of companies in its supply chain. Lear ignored safety issues to the point that the OSHA stepped in on three separate occasions (e.g., here) to cite the company for breaking health and safety laws.
When one of the workers at the Selma plant—Kimberly King, who suffers from asthma she developed while working with these chemicals at the plant—joined a community delegation this spring to the Hyundai plant in Montgomery AL, Lear fired her, then sued her. A federal court slapped Lear with a restraining order and preliminary injunction, but Kim’s fight to get her job back—and, above all, to make these good, safe, family-sustaining jobs —continues. Workers at the plant make around $12 per hour.
Hyundai has the power to step in and tell Lear to make things right.
Student groups, the AFL-CIO young worker councils, and COSH groups were especially important in getting out the message that all workers deserve fair wages and safe conditions. The delegations delivered a letter from United Students Against Sweatshops reporting that the average starting wage for a job at a Hyundai supplier in the Montgomery, AL, area is just $9.07 per hour, and that three-quarters of those employers hire exclusively through temporary staffing agencies. One shocked dealership manager remarked, “Those are McDonald’s wages!” National COSH and affiliates have highlighted how dangerous TDI and other isocyanate chemicals are to workers and the need to have corporations raise the bar for better safety conditions.
Workers in Selma and elsewhere are fighting to be protected from toxic chemical exposure for all workers. The public needs to know that corporations like Hyundai must step up to the plate and insist that their parts supply chains provide safe and healthy workplaces. Customers need to know that buying a Hyundai car is a vote against social justice if the company refuses to be responsible to workers.
Peter Dooley CSP, CIH is a workplace health and safety consultant with thirty five years of experience in safety inspections, fatality investigations, worker education and other related aspects.
“Now, Venus is an extremely hostile environment, and as such presents a lot of challenges for a science fiction author who wants to create life there. However, as I began to research it more thoroughly, I found myself intrigued by the possibilities the world offers.” –Sarah Zettel
Of all the worlds in our Solar System, Venus is perhaps the most like Earth. It’s the closest to us in size, in mass, in orbit, and in elemental content. The biggest difference, of course, is Venus’ atmosphere.
Over 90 times as thick as Earth’s and composed of carbon dioxide and thick sulfuric acid clouds, the surface of Venus is at a constant 465°C (870 °F), making it the hottest planet in the Solar System. Yet we’ve both landed on the surface and imaged the entire world through its clouds, finding out exactly what the Venusian surface looks like.
“Now, Venus is an extremely hostile environment, and as such presents a lot of challenges for a science fiction author who wants to create life there. However, as I began to research it more thoroughly, I found myself intrigued by the possibilities the world offers.” –Sarah Zettel
Of all the worlds in our Solar System, Venus is perhaps the most like Earth. It’s the closest to us in size, in mass, in orbit, and in elemental content. The biggest difference, of course, is Venus’ atmosphere.
Over 90 times as thick as Earth’s and composed of carbon dioxide and thick sulfuric acid clouds, the surface of Venus is at a constant 465°C (870 °F), making it the hottest planet in the Solar System. Yet we’ve both landed on the surface and imaged the entire world through its clouds, finding out exactly what the Venusian surface looks like.
A leap second will be added to official timekeeping on Tuesday, June 30, 2015. That means your day – and my day and everyone’s day – will officially be one second longer.
Leap seconds have been added 25 times since 1972. They’re inserted at the end of the last day of either June or December. This time, it will be just before 8 p.m. EDT (midnight UTC) on June 30. The extra second is added to our official timekeeping mainly to keep our increasingly electronic world in sync. The most recent such leap second was added on June 30, 2012, and the one before that was December 31, 2008.
Why do we need a leap second? Isn’t the length of our day set by the rotation of the Earth? Like the ancients who insisted that all motion in the heavens must be perfect, uniform and unvarying, many of us today assume that the Earth’s rotation – its spin on its axis – is perfectly steady. We learned, correctly, that the sun, moon, stars and planets parade across our sky because the Earth turns. So it is easy to understand why we assume that the Earth’s rotation is precise and unwavering. Yet Earth’s rotation does not stay perfectly steady.
Instead, compared to modern timekeeping methods such as atomic clocks, the Earth is a notoriously poor timepiece. Not only is Earth’s spin slowing down, but it also is subject to effects that cannot even be predicted well.
The last leap second was added on June 30, 2012 just before midnight UTC. Image via NASA
Ocean tides are what is causing Earth to slow down in its rotation
If you have ever been to the beach, you will be familiar with the main reason our planet is slowing down. That reason is ocean tides. As our planet rotates, it plows past the great watery bulges (raised mostly by the gravitational interaction of the Earth and moon), which serves to slow it down much like a brake on a rotating wheel. This effect is small, actually very small. According to calculations based on the timing of ancient astronomical events (eclipses), the Earth’s rotation has slowed down by about .0015 to .002 seconds per day per century.
That in itself is not much, and is not enough to justify adding a “leap second” every few years, as has been done since 1972. The length of a day today is almost imperceptibly longer than the length as the same day last year. In the 1800s, a day was defined as 86,400 seconds. Today it is 86,400.002 seconds, roughly.
The discrepancy comes by comparing the Earth’s daily rotation relative to astronomical objects (which show the planet slowing down), to a extremely high precision atomic clock (which is accurate to about a billionth of a second per day).
This U.S. Naval Observatory graphic depicts small changes in the rate at which Earth spins.
Chip scale atomic clock, introduced by U.S. National Institute of Standards and Technology in 2004. Time is now measured using stable atomic clocks. Meanwhile, the rotation of Earth is much more variable.
The Earth is slowing down, very slowly. It takes about 100 years for Earth’s rotation to add just 0.002 seconds to the time it takes Earth to spin once on its axis. What happens, though, is that the daily 0.002-second difference between the original definition of a day as being 86,400 seconds builds up.
After one day is it 0.002 seconds. After two days it is 0.004 seconds. After three days it is 0.006 seconds and so on. After about a year and a half, the difference mounts to about 1 second. It is this difference that requires the addition of a leap second.
The situation is not quite that clear cut, however. The figure of 0.002 seconds per day per century is an average and it can, and does, change. For example, you might recall that the Fukushima earthquake in 2011 resulted from displacements of portions of the Earth’s crust that actually speeded up the Earth’s rotation, shortening the day by 1.6 millionth of a second! While that is not much, keep in mind that such changes are cumulative, too.
Other short term and unpredictable changes can be caused by a variety of events, ranging from slight changes in the distribution of mass in the Earth’s molten outer core, to movement of large masses of ice near the poles, and even density and angular momentum variations in the Earth’s atmosphere.
The bottom line is that the actual variation day to day is not always plus 2 milliseconds. According to a U.S. Naval Observatory document, between 1973 to 2008, it has ranged from a plus 4 milliseconds to a minus 1 millisecond. Over time, that could necessitate a negative leap second, signifying an increase in the Earth’s rotation speed, but since the concept was introduced in 1973, this has never been done.
Telecommunications relies on precise timing, and the addition of a leap second forces many systems to be turned off for a second every year or two.
This all may seem pretty esoteric and unimportant, but not to the telecommunications industry.
We’ll say here that everyone thinks a leap second is a good idea. The International Telecommunications Union (ITU), a United Nations body that governs some global issues related to time, has been contemplating leap seconds for some time. They considered abolishing the practice, but in late January 2012 – with delegates from more than 150 nations meeting in Geneva – the ITU decided to defer a proposal to dump the leap second until their 2015 meeting. That meeting is not scheduled until this October, but the decision to add the leap second on June 30 has been deemed necessary.
So consider the ITU’s situation. Telecommunications relies on precise timing, and the addition of a leap second forces many systems to be turned off for a second every year of two. To get all such systems in a global industry cycled on and off in sync can be a major headache. Consider also that the global positioning system (GPS) does not use the leap second system, which causes further confusion. Many in the industry feel that the periodic addition of a “leap second” to keep the to measurements in step is cumbersome and wasteful.
Although dropping the idea of a leap second would be a convenience for telecommunication and other industries, in the long (very long) run, it would cause clocks to get out of synch with the Sun, eventually causing 12 p.m. (noon) to occur in the middle of the night, for example. But at the current rate of change in Earth’s rotation rate, it would take about 5,000 years to amass just a one-hour difference between the Earth’s actual rotation rate and the atomic clock.
But how, you may ask, do we even measure such small changes in the Earth’s rotation? Historically, astronomers (such as those at Britain’s famed Royal Greenwich Observatory near London) have used a telescope to watch a star pass through their eyepiece, crossing an imaginary line called the meridian. Then they time how long it takes for the Earth to bring that around star back around to cross the meridian again. This is highly accurate for everyday purposes, but for scientific use it is limited in accuracy because of the wavelengths used and the murkiness of the atmosphere.
A much more accurate method is to use two or more radio telescopes separated by thousands of miles, in a technique called Very Long Baseline Interferometry. By carefully combining the data from each of the telescopes, astronomers effectively have a telescope thousands of miles in size, which provides much greater resolution (detecting fine detail) and measurement of position. This allows them to determine the planet’s rotation rate to an accuracy of less than a thousandth of a second. They do not observe stars, however, but very distant objects called quasars. The NASA video below will tell you more …
Bottom line: A leap second will be added to the clock on June 30, 2015. Leap sOeconds have been added every so often since 1972. The last one was June 30, 2012. The International Telecommunications Union (ITU), a U.N. body that governs some global issues related to time, has considered abolishing the practice of inserting a leap second into official time-keeping. But the ITU decided in 2012 to defer a proposal to dump the leap second until October, 2015. Stay tuned, timekeepers!
A leap second will be added to official timekeeping on Tuesday, June 30, 2015. That means your day – and my day and everyone’s day – will officially be one second longer.
Leap seconds have been added 25 times since 1972. They’re inserted at the end of the last day of either June or December. This time, it will be just before 8 p.m. EDT (midnight UTC) on June 30. The extra second is added to our official timekeeping mainly to keep our increasingly electronic world in sync. The most recent such leap second was added on June 30, 2012, and the one before that was December 31, 2008.
Why do we need a leap second? Isn’t the length of our day set by the rotation of the Earth? Like the ancients who insisted that all motion in the heavens must be perfect, uniform and unvarying, many of us today assume that the Earth’s rotation – its spin on its axis – is perfectly steady. We learned, correctly, that the sun, moon, stars and planets parade across our sky because the Earth turns. So it is easy to understand why we assume that the Earth’s rotation is precise and unwavering. Yet Earth’s rotation does not stay perfectly steady.
Instead, compared to modern timekeeping methods such as atomic clocks, the Earth is a notoriously poor timepiece. Not only is Earth’s spin slowing down, but it also is subject to effects that cannot even be predicted well.
The last leap second was added on June 30, 2012 just before midnight UTC. Image via NASA
Ocean tides are what is causing Earth to slow down in its rotation
If you have ever been to the beach, you will be familiar with the main reason our planet is slowing down. That reason is ocean tides. As our planet rotates, it plows past the great watery bulges (raised mostly by the gravitational interaction of the Earth and moon), which serves to slow it down much like a brake on a rotating wheel. This effect is small, actually very small. According to calculations based on the timing of ancient astronomical events (eclipses), the Earth’s rotation has slowed down by about .0015 to .002 seconds per day per century.
That in itself is not much, and is not enough to justify adding a “leap second” every few years, as has been done since 1972. The length of a day today is almost imperceptibly longer than the length as the same day last year. In the 1800s, a day was defined as 86,400 seconds. Today it is 86,400.002 seconds, roughly.
The discrepancy comes by comparing the Earth’s daily rotation relative to astronomical objects (which show the planet slowing down), to a extremely high precision atomic clock (which is accurate to about a billionth of a second per day).
This U.S. Naval Observatory graphic depicts small changes in the rate at which Earth spins.
Chip scale atomic clock, introduced by U.S. National Institute of Standards and Technology in 2004. Time is now measured using stable atomic clocks. Meanwhile, the rotation of Earth is much more variable.
The Earth is slowing down, very slowly. It takes about 100 years for Earth’s rotation to add just 0.002 seconds to the time it takes Earth to spin once on its axis. What happens, though, is that the daily 0.002-second difference between the original definition of a day as being 86,400 seconds builds up.
After one day is it 0.002 seconds. After two days it is 0.004 seconds. After three days it is 0.006 seconds and so on. After about a year and a half, the difference mounts to about 1 second. It is this difference that requires the addition of a leap second.
The situation is not quite that clear cut, however. The figure of 0.002 seconds per day per century is an average and it can, and does, change. For example, you might recall that the Fukushima earthquake in 2011 resulted from displacements of portions of the Earth’s crust that actually speeded up the Earth’s rotation, shortening the day by 1.6 millionth of a second! While that is not much, keep in mind that such changes are cumulative, too.
Other short term and unpredictable changes can be caused by a variety of events, ranging from slight changes in the distribution of mass in the Earth’s molten outer core, to movement of large masses of ice near the poles, and even density and angular momentum variations in the Earth’s atmosphere.
The bottom line is that the actual variation day to day is not always plus 2 milliseconds. According to a U.S. Naval Observatory document, between 1973 to 2008, it has ranged from a plus 4 milliseconds to a minus 1 millisecond. Over time, that could necessitate a negative leap second, signifying an increase in the Earth’s rotation speed, but since the concept was introduced in 1973, this has never been done.
Telecommunications relies on precise timing, and the addition of a leap second forces many systems to be turned off for a second every year or two.
This all may seem pretty esoteric and unimportant, but not to the telecommunications industry.
We’ll say here that everyone thinks a leap second is a good idea. The International Telecommunications Union (ITU), a United Nations body that governs some global issues related to time, has been contemplating leap seconds for some time. They considered abolishing the practice, but in late January 2012 – with delegates from more than 150 nations meeting in Geneva – the ITU decided to defer a proposal to dump the leap second until their 2015 meeting. That meeting is not scheduled until this October, but the decision to add the leap second on June 30 has been deemed necessary.
So consider the ITU’s situation. Telecommunications relies on precise timing, and the addition of a leap second forces many systems to be turned off for a second every year of two. To get all such systems in a global industry cycled on and off in sync can be a major headache. Consider also that the global positioning system (GPS) does not use the leap second system, which causes further confusion. Many in the industry feel that the periodic addition of a “leap second” to keep the to measurements in step is cumbersome and wasteful.
Although dropping the idea of a leap second would be a convenience for telecommunication and other industries, in the long (very long) run, it would cause clocks to get out of synch with the Sun, eventually causing 12 p.m. (noon) to occur in the middle of the night, for example. But at the current rate of change in Earth’s rotation rate, it would take about 5,000 years to amass just a one-hour difference between the Earth’s actual rotation rate and the atomic clock.
But how, you may ask, do we even measure such small changes in the Earth’s rotation? Historically, astronomers (such as those at Britain’s famed Royal Greenwich Observatory near London) have used a telescope to watch a star pass through their eyepiece, crossing an imaginary line called the meridian. Then they time how long it takes for the Earth to bring that around star back around to cross the meridian again. This is highly accurate for everyday purposes, but for scientific use it is limited in accuracy because of the wavelengths used and the murkiness of the atmosphere.
A much more accurate method is to use two or more radio telescopes separated by thousands of miles, in a technique called Very Long Baseline Interferometry. By carefully combining the data from each of the telescopes, astronomers effectively have a telescope thousands of miles in size, which provides much greater resolution (detecting fine detail) and measurement of position. This allows them to determine the planet’s rotation rate to an accuracy of less than a thousandth of a second. They do not observe stars, however, but very distant objects called quasars. The NASA video below will tell you more …
Bottom line: A leap second will be added to the clock on June 30, 2015. Leap sOeconds have been added every so often since 1972. The last one was June 30, 2012. The International Telecommunications Union (ITU), a U.N. body that governs some global issues related to time, has considered abolishing the practice of inserting a leap second into official time-keeping. But the ITU decided in 2012 to defer a proposal to dump the leap second until October, 2015. Stay tuned, timekeepers!
Wet suit? ✓
Breathing apparatus? ✓
Submarine that would make even the least claustrophobic person twitch? ✓
Submarine storage container belonging to an International Submarine Races team at NAVSEA Warfare Center – Carderock Division. (Photo: Yolanda R. Arrington/Defense Media Activity/Released)
That must mean it’s time for the 13th International Submarine Races, or ISR.
University teams from around the globe converged on Naval Surface Warfare CenterCarderock Division in Bethesda, Maryland, June 22 – 26 to show off their feats of engineering.
History
University submarine teams prepare for the morning’s start of the International Submarine Races on June 25, 2015 at NAVSEA Warfare Center – Carderock Division. (Photo: Yolanda R. Arrington/Defense Media Activity/Released)
Human-powered submarine races were first held in 1989 in Florida with 19 teams from various universities and groups. In addition to university participants, the biennial event also welcomes younger science, technology, engineering and math students to learn about engineering and build underwater vehicles. The submarines can be one or two person vehicles and are propeller or non-propeller driven.
This year, 26 teams showcased their single- and double-occupancy human-powered underwater vehicles in the 3,200-foot-long David Taylor tow tank. Reaching depths of 20 feet, the teams pushed their subs underwater while one or two team members released the hatch and entered the vehicles – all while underwater.
Navy Welcome
In a written message to the student participants, U.S. Navy Capt. Rich Blank, commander of the Carderock Division, welcomed the submarine racers and encouraged their development as scientists and engineers. “Your participation in the ISR is an important component of our innovative culture — pushing the boundaries of what you think is possible, tackling new challenges head-on, and thinking outside the box in creative ways,” Blank said.
Blank also used the event as an opportunity to encourage team members to consider Navy careers. “The exact qualities that make you a competitive candidate in the ISR are the skills we look for in our world-class workforce,” Blank added.
Why They Do It
Vincent Smart, a repeat ISR participant, traveled to Maryland from Quebec, Canada. His team, the Montreal-based Archimede, has modeled its vehicle after a tuna fish. And, they’ve had good results with it, so much that they’ve used the single-person “Archimede VI MK II” vehicle in three races.
The Virginia Tech HPS team works on its “Phantom 6″ vehicle outside the International Submarine Races on June 25, 2015 at NAVSEA Warfare Center – Carderock Division. (Photo: Yolanda R. Arrington/Defense Media Activity/Released)
Thomas Maulbeck, a freshman from Virginia Beach, Virginia, majoring in material science engineering, is on the Virginia Tech HPS team, racing the “Phantom 6.” It’s his first year participating in the ISR. The 2-person “Phantom 6” vehicle has been in use for eight years. The team’s goal is to get it to complete a run so that it can be decommissioned for the next step of Virginia Tech’s ISR quest, the “Phantom 7.”
“Our whole team is volunteers. We don’t get credit. We’re here because we want to be here. This program supplements what I get in the classroom,” Maulbeck said.
Winners
The winners take home trophies or plaques, and various amounts of cash awards. The winning teams were announced late Friday, June 26.
One person – propeller: WASUB 5, Delft University (Delft, Netherlands)
One person – propeller (woman): WHAT SUB DAWG, University of Washington (Seattle, Washington)
One person – non-propeller: TANIWHA, University of Auckland (Auckland, New Zealand)
One person – non-propeller (woman): INIA, Rhein-Waal University of Applied Science (Kleve, NRW, Germany)
Two person – propeller: OMER 9, École de Technologie Supérieure (Montreal, Québec, Canada)
Two person – propeller (woman): FAU-BOAT II, Florida Atlantic University (Boca Raton, Florida)
Visit our Facebook and Twitter pages for more videos and photos from the ISR!
Yolanda R. Arrington is the content manager for Armed with Science. She is a journalist and social media-ista with a flair for moving pictures and writing. ———-
Disclaimer: Re-published content may have been edited for length and clarity. The appearance of hyperlinks does not constitute endorsement by the Department of Defense. For other than authorized activities, such as, military exchanges and Morale, Welfare and Recreation sites, the Department of Defense does not exercise any editorial control over the information you may find at these locations. Such links are provided consistent with the stated purpose of this DoD website.
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Wet suit? ✓
Breathing apparatus? ✓
Submarine that would make even the least claustrophobic person twitch? ✓
Submarine storage container belonging to an International Submarine Races team at NAVSEA Warfare Center – Carderock Division. (Photo: Yolanda R. Arrington/Defense Media Activity/Released)
That must mean it’s time for the 13th International Submarine Races, or ISR.
University teams from around the globe converged on Naval Surface Warfare CenterCarderock Division in Bethesda, Maryland, June 22 – 26 to show off their feats of engineering.
History
University submarine teams prepare for the morning’s start of the International Submarine Races on June 25, 2015 at NAVSEA Warfare Center – Carderock Division. (Photo: Yolanda R. Arrington/Defense Media Activity/Released)
Human-powered submarine races were first held in 1989 in Florida with 19 teams from various universities and groups. In addition to university participants, the biennial event also welcomes younger science, technology, engineering and math students to learn about engineering and build underwater vehicles. The submarines can be one or two person vehicles and are propeller or non-propeller driven.
This year, 26 teams showcased their single- and double-occupancy human-powered underwater vehicles in the 3,200-foot-long David Taylor tow tank. Reaching depths of 20 feet, the teams pushed their subs underwater while one or two team members released the hatch and entered the vehicles – all while underwater.
Navy Welcome
In a written message to the student participants, U.S. Navy Capt. Rich Blank, commander of the Carderock Division, welcomed the submarine racers and encouraged their development as scientists and engineers. “Your participation in the ISR is an important component of our innovative culture — pushing the boundaries of what you think is possible, tackling new challenges head-on, and thinking outside the box in creative ways,” Blank said.
Blank also used the event as an opportunity to encourage team members to consider Navy careers. “The exact qualities that make you a competitive candidate in the ISR are the skills we look for in our world-class workforce,” Blank added.
Why They Do It
Vincent Smart, a repeat ISR participant, traveled to Maryland from Quebec, Canada. His team, the Montreal-based Archimede, has modeled its vehicle after a tuna fish. And, they’ve had good results with it, so much that they’ve used the single-person “Archimede VI MK II” vehicle in three races.
The Virginia Tech HPS team works on its “Phantom 6″ vehicle outside the International Submarine Races on June 25, 2015 at NAVSEA Warfare Center – Carderock Division. (Photo: Yolanda R. Arrington/Defense Media Activity/Released)
Thomas Maulbeck, a freshman from Virginia Beach, Virginia, majoring in material science engineering, is on the Virginia Tech HPS team, racing the “Phantom 6.” It’s his first year participating in the ISR. The 2-person “Phantom 6” vehicle has been in use for eight years. The team’s goal is to get it to complete a run so that it can be decommissioned for the next step of Virginia Tech’s ISR quest, the “Phantom 7.”
“Our whole team is volunteers. We don’t get credit. We’re here because we want to be here. This program supplements what I get in the classroom,” Maulbeck said.
Winners
The winners take home trophies or plaques, and various amounts of cash awards. The winning teams were announced late Friday, June 26.
One person – propeller: WASUB 5, Delft University (Delft, Netherlands)
One person – propeller (woman): WHAT SUB DAWG, University of Washington (Seattle, Washington)
One person – non-propeller: TANIWHA, University of Auckland (Auckland, New Zealand)
One person – non-propeller (woman): INIA, Rhein-Waal University of Applied Science (Kleve, NRW, Germany)
Two person – propeller: OMER 9, École de Technologie Supérieure (Montreal, Québec, Canada)
Two person – propeller (woman): FAU-BOAT II, Florida Atlantic University (Boca Raton, Florida)
Visit our Facebook and Twitter pages for more videos and photos from the ISR!
Yolanda R. Arrington is the content manager for Armed with Science. She is a journalist and social media-ista with a flair for moving pictures and writing. ———-
Disclaimer: Re-published content may have been edited for length and clarity. The appearance of hyperlinks does not constitute endorsement by the Department of Defense. For other than authorized activities, such as, military exchanges and Morale, Welfare and Recreation sites, the Department of Defense does not exercise any editorial control over the information you may find at these locations. Such links are provided consistent with the stated purpose of this DoD website.
