Monday, February 09, 2009, 9:28 pm
Asteroid bound for Earth!
Warn your grandchildren!
* 09 February 2009 by David Shiga
AN ASTEROID that had initially been deemed harmless has turned out to have a slim chance of hitting Earth in 160 years. While that might seem a distant threat, there's far less time available to deflect it off course.
Asteroid 1999 RQ36 was discovered a decade ago, but it was not considered particularly worrisome since it has no chance of striking Earth in the next 100 years - the time frame astronomers routinely use to assess potential threats.
Now, new calculations show a 1 in 1400 chance that it will strike Earth between 2169 and 2199, according to Andrea Milani of the University of Pisa in Italy and colleagues (www.arxiv.org/abs/0901.3631).
With an estimated diameter of 560 metres, 1999 RQ36 is more than twice the size of the better-known asteroid Apophis, which has a 1 in 45,000 chance of hitting Earth in 2036 (New Scientist, 12 July 2008, p 12). Both are large enough to unleash devastating tsunamis if they were to smash into the ocean.
Although 1999 RQ36's potential collision is late in the next century, the window of opportunity to deflect it comes much sooner, prior to a series of close approaches to Earth that the asteroid will make between 2060 and 2080.
The window of opportunity to deflect the asteroid comes much sooner than the potential collision
Asteroid trajectories are bent by Earth's gravity during such near misses, and the amount of bending is highly dependent on how close they get to Earth. A small nudge made ahead of a fly-by will get amplified into a large change in trajectory afterward. In the case of 1999 RQ36, a deflection of less than 1 kilometre would be enough to eliminate any chance of collision in the next century.
But after 2080, the asteroid does not come as close to Earth before the potential impact, so any mission to deflect it would have to nudge the asteroid off course by several tens of kilometres - a much more difficult and expensive proposition.
"That's worth thinking about," says Clark Chapman of the Southwest Research Institute in Boulder, Colorado.
As is often the case, more precise calculations enabled by future observations will most likely rule out a collision. But Milani's team says that routine monitoring of asteroids should be extended to look for potential impacts beyond the 100-year time frame, to identify any other similar cases.
And I thought 2012 was supposedly the mark of the end of the world.
Super clocks: More accurate than time itself!
* 09 February 2009 by Matthew Chalmers
For those physicists and philosophers puzzled by nature's fourth dimension, Patrick Gill has a wry response. "Time," he says, "is what you measure in seconds."
For Gill, that is a statement of professional pride. He is what you might call Britain's top timekeeper. Within the windowless - and largely clockless - cream-brick confines of the UK's National Physical Laboratory (NPL), near London, Gill and his colleagues are busy developing the next, staggeringly accurate generation of atomic clocks. These tiny timepieces are the devices that ensure radio, television and mobile-phone transmissions stay in sync, prevent the internet from turning into a mess of missing data packets, make GPS accurate enough to navigate by, and safeguard electricity grids from blackout. They are, in short, the heartbeat of modern life.
These are momentous times for Gill and others like him in timekeeping laboratories around the world. A new generation of atomic tickers, known as optical clocks, have just wrested the record for accuracy from the ensembles of oscillating caesium atoms that held it for half a century. Soon, the new technology will be so refined that if such a clock had ticked away every second since the big bang 13.7 billion years ago, it would not yet have missed a beat. That is an awesome accomplishment - but it's also a problem. At this astonishing precision, we might have to rethink not only how we measure time, but also our concept of time.
... For more, click here.
From that point, the days were numbered for the traditional astronomical second. In 1967, the base unit of time was officially redefined as "the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom".
That should be all for today's post.
Oops. Umpa-lumpas. Almost forgot..
Create your own Friend Test here
Also, check out this website,
http://www.secret-loves.com/index.php?test=1224577.
Ja-na!~
Also watch...
Freaky Cornstarch Monster.
Warn your grandchildren!
* 09 February 2009 by David Shiga
AN ASTEROID that had initially been deemed harmless has turned out to have a slim chance of hitting Earth in 160 years. While that might seem a distant threat, there's far less time available to deflect it off course.
Asteroid 1999 RQ36 was discovered a decade ago, but it was not considered particularly worrisome since it has no chance of striking Earth in the next 100 years - the time frame astronomers routinely use to assess potential threats.
Now, new calculations show a 1 in 1400 chance that it will strike Earth between 2169 and 2199, according to Andrea Milani of the University of Pisa in Italy and colleagues (www.arxiv.org/abs/0901.3631).
With an estimated diameter of 560 metres, 1999 RQ36 is more than twice the size of the better-known asteroid Apophis, which has a 1 in 45,000 chance of hitting Earth in 2036 (New Scientist, 12 July 2008, p 12). Both are large enough to unleash devastating tsunamis if they were to smash into the ocean.
Although 1999 RQ36's potential collision is late in the next century, the window of opportunity to deflect it comes much sooner, prior to a series of close approaches to Earth that the asteroid will make between 2060 and 2080.
The window of opportunity to deflect the asteroid comes much sooner than the potential collision
Asteroid trajectories are bent by Earth's gravity during such near misses, and the amount of bending is highly dependent on how close they get to Earth. A small nudge made ahead of a fly-by will get amplified into a large change in trajectory afterward. In the case of 1999 RQ36, a deflection of less than 1 kilometre would be enough to eliminate any chance of collision in the next century.
But after 2080, the asteroid does not come as close to Earth before the potential impact, so any mission to deflect it would have to nudge the asteroid off course by several tens of kilometres - a much more difficult and expensive proposition.
"That's worth thinking about," says Clark Chapman of the Southwest Research Institute in Boulder, Colorado.
As is often the case, more precise calculations enabled by future observations will most likely rule out a collision. But Milani's team says that routine monitoring of asteroids should be extended to look for potential impacts beyond the 100-year time frame, to identify any other similar cases.
And I thought 2012 was supposedly the mark of the end of the world.
Super clocks: More accurate than time itself!
* 09 February 2009 by Matthew Chalmers
For those physicists and philosophers puzzled by nature's fourth dimension, Patrick Gill has a wry response. "Time," he says, "is what you measure in seconds."
For Gill, that is a statement of professional pride. He is what you might call Britain's top timekeeper. Within the windowless - and largely clockless - cream-brick confines of the UK's National Physical Laboratory (NPL), near London, Gill and his colleagues are busy developing the next, staggeringly accurate generation of atomic clocks. These tiny timepieces are the devices that ensure radio, television and mobile-phone transmissions stay in sync, prevent the internet from turning into a mess of missing data packets, make GPS accurate enough to navigate by, and safeguard electricity grids from blackout. They are, in short, the heartbeat of modern life.
These are momentous times for Gill and others like him in timekeeping laboratories around the world. A new generation of atomic tickers, known as optical clocks, have just wrested the record for accuracy from the ensembles of oscillating caesium atoms that held it for half a century. Soon, the new technology will be so refined that if such a clock had ticked away every second since the big bang 13.7 billion years ago, it would not yet have missed a beat. That is an awesome accomplishment - but it's also a problem. At this astonishing precision, we might have to rethink not only how we measure time, but also our concept of time.
... For more, click here.
From that point, the days were numbered for the traditional astronomical second. In 1967, the base unit of time was officially redefined as "the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom".
Oops. Umpa-lumpas. Almost forgot..
Create your own Friend Test here
Also, check out this website,
http://www.secret-loves.com/index.php?test=1224577.
Ja-na!~
Also watch...
Freaky Cornstarch Monster.
