OT- Tonight is the Night- 2:00am
- By PanamaSteve
- Trojan Talk
- 12 Replies
Heads up!
Here's How to Watch the Perseid Meteor Shower This Weekend
By Laura Geggel, Senior Writer | August 10, 2018 06:53am ET
Jason Weingart captures shooting stars during the Persied meteor shower on Aug. 14, 2016 in Big Bend National Park in Terlingua, Texas.
Credit: Jason Weingart/Barcroft Images/Barcroft Media via Getty Images
The Perseid meteor shower is almost here, meaning that it's nearly time to head outside and lift your eyes toward the heavens, where you can gaze upon hundreds of shooting stars lighting up the night sky. The meteor shower is expected to peak this weekend, on Saturday and Sunday (Aug. 11 and 12).
And it doesn't take a rocket scientist to get a good view, or even to wish upon a shooting star (or several dozen of them).
"All you've got to do is go outside, find a nice dark spot, lie flat on your back and look up," Bill Cooke, head of NASA's Meteoroid Environments Office at the Marshall Space Flight Center in Alabama, told Live Science previously. "You don't want binoculars. You don't want a telescope. You just use your eyes." [Perseid Meteor Shower 2018: When, Where & How to See It]
This year's show is expected to be especially stunning, in part, because the moon will be a thin crescent and will set early, leaving a dark night sky for stargazing, reported Space.com, a Live Science sister site. And even though there won't be as many shooting stars as in past years — in 2016, for example, there were as many as 200 visible meteors per hour — there will still be a boatload this weekend, with as many as 60 to 70 meteors per hour during its peak, Cooke told Space.com.
That's way more than on a typical night, when just a handful of meteors per hour whiz by, according to NASA.
So, why are Earthlings treated to such a dazzling display of light during the Perseids? It's all because of the Comet Swift-Tuttle, which zooms close to Earth during its 133-year journey around the sun. When it last passed by in 1992, this comet left a trail of stony grit, NASA reported.
Every summer, Earth ploughs through this thick trail (this year, it entered the trail on July 17, and it will exit on Aug. 24), allowing some of the comet's ancient debris to enter and burn up in our planet's atmosphere. As the space rocks burn, they create a bright streak of light known as meteors, or shooting stars.
Our planet will plough through the densest and dustiest part of the trail this weekend. While the Perseid meteor shower will be visible on Saturday night, the real show comes on Sunday, with peak shooting star activityhappening the night of Aug. 12 to 13.
Here are some tips for star-searchers:
-The meteor shower is more visible from the Northern Hemisphere and some mid-southern latitudes, so people in the United States will have a prime view.
-Escape from city lights and find a nice, dark spot, so you'll be able to see the fainter meteors, Cooke said.
-Give your eyes about 30 minutes to adjust to the dark sky."Don't expect to walk outside and see Perseids," Cooke said.
-The best time to see the Perseids is after 2 a.m. local time, when the Perseus constellation is high in the sky, Space.com reported.
-Ditch the binoculars and telescope. You'll want to see the whole night sky, and that equipment will only reduce your field of view.
-Photographers planning to snap nighttime shots should set up their camera on a tripod. Then, take a long-exposure shot, lasting from a few seconds to a minute. But don't go longer than that, otherwise you'll pick up the rotation of the stars, which could block out streaks from shooting stars, Cooke said.
Here's How to Watch the Perseid Meteor Shower This Weekend
By Laura Geggel, Senior Writer | August 10, 2018 06:53am ET
Jason Weingart captures shooting stars during the Persied meteor shower on Aug. 14, 2016 in Big Bend National Park in Terlingua, Texas.
Credit: Jason Weingart/Barcroft Images/Barcroft Media via Getty Images
The Perseid meteor shower is almost here, meaning that it's nearly time to head outside and lift your eyes toward the heavens, where you can gaze upon hundreds of shooting stars lighting up the night sky. The meteor shower is expected to peak this weekend, on Saturday and Sunday (Aug. 11 and 12).
And it doesn't take a rocket scientist to get a good view, or even to wish upon a shooting star (or several dozen of them).
"All you've got to do is go outside, find a nice dark spot, lie flat on your back and look up," Bill Cooke, head of NASA's Meteoroid Environments Office at the Marshall Space Flight Center in Alabama, told Live Science previously. "You don't want binoculars. You don't want a telescope. You just use your eyes." [Perseid Meteor Shower 2018: When, Where & How to See It]
This year's show is expected to be especially stunning, in part, because the moon will be a thin crescent and will set early, leaving a dark night sky for stargazing, reported Space.com, a Live Science sister site. And even though there won't be as many shooting stars as in past years — in 2016, for example, there were as many as 200 visible meteors per hour — there will still be a boatload this weekend, with as many as 60 to 70 meteors per hour during its peak, Cooke told Space.com.
That's way more than on a typical night, when just a handful of meteors per hour whiz by, according to NASA.
So, why are Earthlings treated to such a dazzling display of light during the Perseids? It's all because of the Comet Swift-Tuttle, which zooms close to Earth during its 133-year journey around the sun. When it last passed by in 1992, this comet left a trail of stony grit, NASA reported.
Every summer, Earth ploughs through this thick trail (this year, it entered the trail on July 17, and it will exit on Aug. 24), allowing some of the comet's ancient debris to enter and burn up in our planet's atmosphere. As the space rocks burn, they create a bright streak of light known as meteors, or shooting stars.
Our planet will plough through the densest and dustiest part of the trail this weekend. While the Perseid meteor shower will be visible on Saturday night, the real show comes on Sunday, with peak shooting star activityhappening the night of Aug. 12 to 13.
Here are some tips for star-searchers:
-The meteor shower is more visible from the Northern Hemisphere and some mid-southern latitudes, so people in the United States will have a prime view.
-Escape from city lights and find a nice, dark spot, so you'll be able to see the fainter meteors, Cooke said.
-Give your eyes about 30 minutes to adjust to the dark sky."Don't expect to walk outside and see Perseids," Cooke said.
-The best time to see the Perseids is after 2 a.m. local time, when the Perseus constellation is high in the sky, Space.com reported.
-Ditch the binoculars and telescope. You'll want to see the whole night sky, and that equipment will only reduce your field of view.
-Photographers planning to snap nighttime shots should set up their camera on a tripod. Then, take a long-exposure shot, lasting from a few seconds to a minute. But don't go longer than that, otherwise you'll pick up the rotation of the stars, which could block out streaks from shooting stars, Cooke said.
OT- Now This is Interesting- Sound has negative gravity.
- By PanamaSteve
- Trojan Talk
- 11 Replies
Researchers Find Source of Strange 'Negative' Gravity
By Rafi Letzter, Staff Writer | August 10, 2018 01:06pm ET
Scientists have long thought of soundwaves as massless, and this image of the sound waves surrounding a supersonic jet sure look that way. But new research suggests that isn't quite the case.
Credit: Shutterstock
Sound has negative mass, and all around you it's drifting up, up and away — albeit very slowly.
That's the conclusion of a paper submitted on July 23 to the preprint journal arXiv, and it shatters the conventional understanding that researchers have long had of sound waves: as massless ripples that zip through matter, giving molecules a shove but ultimately balancing any forward or upward motion with an equal and opposite downward motion. That's a straightforward model that will explain the behavior of sound in most circumstances, but it's not quite true, the new paper argues. [The Mysterious Physics of 7 Everyday Things]
A phonon — a particle-like unit of vibration that can describe sound at very small scales — has a very slight negative mass, and that means sound waves travel upward ever so slightly, said Rafael Krichevsky, a graduate student in physics at Columbia University.
Phonons aren't particles of the sort most people typically imagine, like atoms or molecules, said Krichevsky, who published the paper along with Angelo Esposito, a graduate student in physics at Columbia University, and Alberto Nicolis, an associate physics professor at Columbia.
When sound moves through air it vibrates the molecules around it, but that vibration can't be easily described by the movement of the molecules themselves, Krichevsky told Live Science in an email.
Instead, just as light waves can be described as photons, or a particles of light, phonons are a way to describe sound waves that emerge from the complicated interactions of the fluid molecules, Krichevsky said. No physical particle emerges, but researchers can use the mathematics of particles to describe it.
And it turns out, the researchers showed, these emergent phonons have a tiny mass — meaning that when gravity tugs on them, they move in the opposite direction.
"In a gravitational field phonons slowly accelerate in the opposite direction that you would expect, say, a brick to fall," Krichevsky said.
To understand how this might work, imagine a normal fluid in which gravity acts downward. Fluid particles will compress the particles below it, so that it's slightly denser lower down. Physicists already know that sound typically moves faster through denser media than through less-dense media — so the speed of sound above a phonon will be slower than the speed of sound through the slightly denser particles below it. That causes the phonon to "deflect" upward, Krichevsky said.
This process happens with large-scale sound waves, too, Krichevsky said. That includes every bit of sound that comes out of your mouth — albeit only very slightly. Over a long-enough distance, the sound of you saying "hello" would bend upward into the sky.
The effect is too tiny to measure with existing technology, the researchers wrote in the new paper, which has not been peer-reviewed.
But it's not impossible that, down the road, a very precise measurement could be made using super-precise clocks that would detect the slight curvature of a phonon's path. (The New Scientist suggested heavy-metal music would be a fun candidate for such an experiment in their original report on the subject.)
And there are real consequences to this discovery, the researcher wrote. In the dense cores of neutron stars, where sound waves move at nearly the speed of light, an anti-gravitational sound wave should have real effects on the whole star's behavior.
For now, though, this is entirely theoretical — something to ponder as sound falls upward all around us.
By Rafi Letzter, Staff Writer | August 10, 2018 01:06pm ET
Scientists have long thought of soundwaves as massless, and this image of the sound waves surrounding a supersonic jet sure look that way. But new research suggests that isn't quite the case.
Credit: Shutterstock
Sound has negative mass, and all around you it's drifting up, up and away — albeit very slowly.
That's the conclusion of a paper submitted on July 23 to the preprint journal arXiv, and it shatters the conventional understanding that researchers have long had of sound waves: as massless ripples that zip through matter, giving molecules a shove but ultimately balancing any forward or upward motion with an equal and opposite downward motion. That's a straightforward model that will explain the behavior of sound in most circumstances, but it's not quite true, the new paper argues. [The Mysterious Physics of 7 Everyday Things]
A phonon — a particle-like unit of vibration that can describe sound at very small scales — has a very slight negative mass, and that means sound waves travel upward ever so slightly, said Rafael Krichevsky, a graduate student in physics at Columbia University.
Phonons aren't particles of the sort most people typically imagine, like atoms or molecules, said Krichevsky, who published the paper along with Angelo Esposito, a graduate student in physics at Columbia University, and Alberto Nicolis, an associate physics professor at Columbia.
When sound moves through air it vibrates the molecules around it, but that vibration can't be easily described by the movement of the molecules themselves, Krichevsky told Live Science in an email.
Instead, just as light waves can be described as photons, or a particles of light, phonons are a way to describe sound waves that emerge from the complicated interactions of the fluid molecules, Krichevsky said. No physical particle emerges, but researchers can use the mathematics of particles to describe it.
And it turns out, the researchers showed, these emergent phonons have a tiny mass — meaning that when gravity tugs on them, they move in the opposite direction.
"In a gravitational field phonons slowly accelerate in the opposite direction that you would expect, say, a brick to fall," Krichevsky said.
To understand how this might work, imagine a normal fluid in which gravity acts downward. Fluid particles will compress the particles below it, so that it's slightly denser lower down. Physicists already know that sound typically moves faster through denser media than through less-dense media — so the speed of sound above a phonon will be slower than the speed of sound through the slightly denser particles below it. That causes the phonon to "deflect" upward, Krichevsky said.
This process happens with large-scale sound waves, too, Krichevsky said. That includes every bit of sound that comes out of your mouth — albeit only very slightly. Over a long-enough distance, the sound of you saying "hello" would bend upward into the sky.
The effect is too tiny to measure with existing technology, the researchers wrote in the new paper, which has not been peer-reviewed.
But it's not impossible that, down the road, a very precise measurement could be made using super-precise clocks that would detect the slight curvature of a phonon's path. (The New Scientist suggested heavy-metal music would be a fun candidate for such an experiment in their original report on the subject.)
And there are real consequences to this discovery, the researcher wrote. In the dense cores of neutron stars, where sound waves move at nearly the speed of light, an anti-gravitational sound wave should have real effects on the whole star's behavior.
For now, though, this is entirely theoretical — something to ponder as sound falls upward all around us.
