astrodidact:

Planck Time

What is the smallest unit of time you can conceive? A second? A millisecond? Hard to say seeing as how time is relative. Under the right circumstances, hours can fly by and seconds can feel like a lifetime. But unfortunately for physicists, time is not something that can be delt with so philosophically. And since they deal with cosmological forces both infinitesimally large and small, they need units that can objectively measure them. When it comes to dealing with the small, Planck Time is the measurement of choice. Named after German physicist Max Planck, the founder of quantum theory, a unit of Planck time is the time it takes for light to travel, in a vacuum, a single unit of Planck length. Taken together, they part of the larger system of natural units known as Planck units.

Originally proposed in 1899 by German physicist Max Planck, Planck units are physical units of measurement defined exclusively in terms of five universal physical constants. These are the Gravitational constant (G), the Reduced Planck constant (h), the speed of light in a vacuum (c), the Coulomb constant(ke or k), and Boltzmann’s constant (kB, sometimes k). Each of these constants can be associated with at least one fundamental physical theory: c with special relativity, G with general relativity and Newtonian gravity, with quantum mechanics, with electrostatics, and kB with statistical mechanics and thermodynamics. They were invented as a means of simplifying the particular algebraic expressions appearing in theoretical physics, especially in quantum mechanics.

Ultimately, Planck time is derived from the field of mathematical physics known as dimensional analysis, which studies units of measurement and physical constants. The Planck time is the unique combination of the gravitational constant G, the relativity constant c, and the quantum constant h, to produce a constant with units of time. They are often semi-humorously referred to by physicists as “God’s units” because eliminate anthropocentric arbitrariness from the system of units, unlike the meter and second, which exist for purely historical reasons and are not derived from nature. Some challenges to Planck’s Time have been mounted. For example, in 2003 during the analysis of the Hubble Space Telescope Deep Field images, some scientists speculated that where there are space-time fluctuations on the Planck scale, images of extremely distant objects should be blurry. The Hubble images, they claimed, were too sharp for this to be the case. Other scientists disagreed with this assumption however, with some saying the fluctuations would be too small to be observable, others saying that the speculated blurring effect that was expected was off by a very large magnitude. A unit of Planck Time can be expressed (in the third picture).

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Source: astrodidact

spaceplasma: An Expanding Bubble in Space A star 40 times more massive than our sun is blowing a giant bubble of material into space. In this colorful picture, the Hubble Telescope captured a glimpse of the expanding bubble, dubbed the Bubble Nebula (NGC 7635). The beefy star [lower center] is embedded in the bright blue bubble. The stellar powerhouse is so hot that it is quickly shedding material into space. The dense gas surrounding the star is shaping the castoff material into a bubble. The bubble’s surface is not smooth like a soap bubble’s. Its rippled appearance is due to encounters with gases of different thickness. The nebula is 6 light-years wide and is expanding at 4 million miles per hour (7 million kilometers per hour). The nebula is 7,100 light-years from Earth in the constellation Cassiopeia. Image Credit: NASA, Donald Walter (South Carolina State University), Paul Scowen and Brian Moore (Arizona State University)
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spaceplasma:

An Expanding Bubble in Space

A star 40 times more massive than our sun is blowing a giant bubble of material into space. In this colorful picture, the Hubble Telescope captured a glimpse of the expanding bubble, dubbed the Bubble Nebula (NGC 7635). The beefy star [lower center] is embedded in the bright blue bubble. The stellar powerhouse is so hot that it is quickly shedding material into space. The dense gas surrounding the star is shaping the castoff material into a bubble. The bubble’s surface is not smooth like a soap bubble’s. Its rippled appearance is due to encounters with gases of different thickness. The nebula is 6 light-years wide and is expanding at 4 million miles per hour (7 million kilometers per hour). The nebula is 7,100 light-years from Earth in the constellation Cassiopeia.

Image Credit: NASA, Donald Walter (South Carolina State University), Paul Scowen and Brian Moore (Arizona State University)

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Source: spaceplasma

christinetheastrophysicist: Cosmic flashes could herald birth of black holes The birth of a black hole may be signalled by a characteristic cosmic flash, according to researchers in the US. It was previously thought that only the most massive of black holes would produce gamma-ray bursts – narrow beams of electromagnetic radiation that shoot out of the poles of the collapsing star – when they form. But other dying stars were thought to produce a black hole without any kind of flash – seemingly disappearing from the visible sky in an event known as an “unnova”. The US researchers’ work suggests that unnovae might also have their own characteristic flash, allowing astronomers to witness the birth of stellar- and intermediate-mass black holes. Read More.
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christinetheastrophysicist:

Cosmic flashes could herald birth of black holes

The birth of a black hole may be signalled by a characteristic cosmic flash, according to researchers in the US. It was previously thought that only the most massive of black holes would produce gamma-ray bursts – narrow beams of electromagnetic radiation that shoot out of the poles of the collapsing star – when they form. But other dying stars were thought to produce a black hole without any kind of flash – seemingly disappearing from the visible sky in an event known as an “unnova”. The US researchers’ work suggests that unnovae might also have their own characteristic flash, allowing astronomers to witness the birth of stellar- and intermediate-mass black holes.

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(via scinerds)

Source: physicsworld.com

ikenbot: Boldly Go? Can Humanity Afford ‘Star Trek’-Like Space Exploration? The public has no shortage of enthusiasm for fictional spacefarers, as this weekend’s box-office win by the newest “Star Trek” film proves. Yet the real-life U.S. space agency finds itself strapped for cash these days. With federal budgets tightening and NASA feeling the pinch, some space advocates are asking, “Can humans afford to reach the stars?” Believe it or not, experts are looking into the finances of not just relatively short-term missions to Mars and the moon, but also long-term prospects of ‘Trek’-ian proportions. It may be possible to find the money, they say, but it would likely take some policy changes — and those changes could start today. Captain, we don’t have the funding! “Star Trek: Into Darkness” brought in about $84 million in its opening weekend — just a month after NASA cut $200 million from its planetary-sciences budget. (In an odd move, NASA’s newest budget explicitly states that it will notfund any missions to Europa, the ice-moon of Jupiter that stands as one of the solar system’s best candidates for supporting life, noted Casey Dreier, an advocacy and outreach strategist at The Planetary Society, a nonprofit organization devoted to planetary exploration.) Those cuts come as NASA and the rest of the federal government negotiate sequestration cuts, which could trim $7 billion from NASA’s ledgers next year if the reductions are maintained. But even without the sequester, NASA hasn’t commanded the kind of money needed for real, ambitious space travel in decades, said Marc Millis, a former NASA propulsion physicist and founder of the Tau Zero Foundation, which is dedicated to interstellar travel. After hitting an apex with the Apollo moon program, NASA’s purse shrunk considerably and has stayed stagnant since, Millis said. NASA’s funds reached about 4.5 percent of the total federal budget during the Apollo era, Millis calculated. By 2009, NASA’s share had fallen to about 0.5 percent. “The amount that’s devoted to NASA now is enough to keep it going,” he said. “But to do really cool space travel is not possible now.” Essentially, the agency has floated along on autopilot, clutching at relatively low-hanging fruit, like the space-shuttle missions, said Paul Gilster, who researches and writes about interstellar technologies for Tau Zero. “We should have something else than just going ‘round and ‘round the Earth,” he said.
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ikenbot:

Boldly Go? Can Humanity Afford ‘Star Trek’-Like Space Exploration?

The public has no shortage of enthusiasm for fictional spacefarers, as this weekend’s box-office win by the newest “Star Trek” film proves. Yet the real-life U.S. space agency finds itself strapped for cash these days. With federal budgets tightening and NASA feeling the pinch, some space advocates are asking, “Can humans afford to reach the stars?”

Believe it or not, experts are looking into the finances of not just relatively short-term missions to Mars and the moon, but also long-term prospects of ‘Trek’-ian proportions. It may be possible to find the money, they say, but it would likely take some policy changes — and those changes could start today.

Captain, we don’t have the funding!

“Star Trek: Into Darkness” brought in about $84 million in its opening weekend — just a month after NASA cut $200 million from its planetary-sciences budget. (In an odd move, NASA’s newest budget explicitly states that it will notfund any missions to Europa, the ice-moon of Jupiter that stands as one of the solar system’s best candidates for supporting life, noted Casey Dreier, an advocacy and outreach strategist at The Planetary Society, a nonprofit organization devoted to planetary exploration.)

Those cuts come as NASA and the rest of the federal government negotiate sequestration cuts, which could trim $7 billion from NASA’s ledgers next year if the reductions are maintained.

But even without the sequester, NASA hasn’t commanded the kind of money needed for real, ambitious space travel in decades, said Marc Millis, a former NASA propulsion physicist and founder of the Tau Zero Foundation, which is dedicated to interstellar travel.

After hitting an apex with the Apollo moon program, NASA’s purse shrunk considerably and has stayed stagnant since, Millis said. NASA’s funds reached about 4.5 percent of the total federal budget during the Apollo era, Millis calculated. By 2009, NASA’s share had fallen to about 0.5 percent. “The amount that’s devoted to NASA now is enough to keep it going,” he said. “But to do really cool space travel is not possible now.”

Essentially, the agency has floated along on autopilot, clutching at relatively low-hanging fruit, like the space-shuttle missions, said Paul Gilster, who researches and writes about interstellar technologies for Tau Zero. “We should have something else than just going ‘round and ‘round the Earth,” he said.

(via we-are-star-stuff)

Source: space.com

ikenbot: Huge Asteroid to Fly Past Earth This Month A big asteroid will cruise by Earth at the end of the month, making its closest approach to our planet for at least the next two centuries. Image: The asteroid 1998 QE2, which is about 1.7 miles (2.7 kilometers) long, will come within 3.6 million miles (5.8 million km) of Earth on May 31, 2013. Credit: NASA/JPL-Caltech The May 31 flyby of asteroid 1998 QE2, which is about 1.7 miles (2.7 kilometers) long, poses no threat to Earth. The space rock will come within 3.6 million miles (5.8 million km) of our planet — about 15 times the distance separating Earth and the moon, researchers say. But the close approach will still be dramatic for astronomers, who plan to get a good look at 1998 QE2 using two huge radar telescopes — NASA’s 230-foot (70 meters) Goldstone dish in California and the 1,000-foot (305 m) Arecibo Observatory in Puerto Rico. Full Article
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ikenbot:

Huge Asteroid to Fly Past Earth This Month

A big asteroid will cruise by Earth at the end of the month, making its closest approach to our planet for at least the next two centuries.

Image: The asteroid 1998 QE2, which is about 1.7 miles (2.7 kilometers) long, will come within 3.6 million miles (5.8 million km) of Earth on May 31, 2013. Credit: NASA/JPL-Caltech

The May 31 flyby of asteroid 1998 QE2, which is about 1.7 miles (2.7 kilometers) long, poses no threat to Earth. The space rock will come within 3.6 million miles (5.8 million km) of our planet — about 15 times the distance separating Earth and the moon, researchers say.

But the close approach will still be dramatic for astronomers, who plan to get a good look at 1998 QE2 using two huge radar telescopes — NASA’s 230-foot (70 meters) Goldstone dish in California and the 1,000-foot (305 m) Arecibo Observatory in Puerto Rico.

Full Article

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Source: livescience.com