(via Vortex loops could untie knotty physics problems | UChicago News)

University of Chicago physicists have succeeded in creating a vortex knot—a feat akin to tying a smoke ring into a knot. Linked and knotted vortex loops have existed in theory for more than a century, but creating them in the laboratory had previously eluded scientists.

Vortex knots should, in principle, be persistent, stable phenomena. “The unexpected thing is that they’re not,” said Dustin Kleckner, a postdoctoral scientist at UChicago’s James Franck Institute. “They seem to break up in a particular way. They stretch themselves, which is a weird behavior.”

This behavior culminates in what the UChicago researchers call “reconnection events.” In these events, the loops elongate, begin to circulate in opposite directions, move toward each other and collide (the reconnection). Parts of the vortices then annihilate other parts, changing their configuration from linked or knotted into one that is unlinked or unknotted.

Kleckner and William Irvine, assistant professor in physics, report their findings on the creation and dynamics of vortex rings in Nature Physics, published online Sunday, March 3. Their work relates to deep questions in a variety of physics subfields, including turbulence, plasma physics, ordinary fluids and the more exotic superfluids. Knotted structures are thought to occur in all these phenomena but are difficult or impossible to observe.

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buffalosouljaboy

chii24:

THE SUN IS ON FIRE, I REPEAT, THE SUN IS ON FIRE.

[Cue Angwe’s pedantic ass music!]

The sun, alas, is not on fire. It’s a plasma. All over. Pretty much everything on the sun is a superheated gas.

Fire, as we usually define it, is the exothermic output of combustion, through physio-chemical processes. Wood burning, for instance, is complex carbons + heat + oxygen, and gives us a sustained reaction of carbons breaking down and releasing more heat energy. Other fires are much the same: thermite burns hotter and so requires a bit more of a reaction to get started (you generally need some magnesium, which burns hotter than your average match), but is still thermite + heat + oxygen = a whole lot of new heat energy + leftover compounds.

A plasma is a little different. The gravity of something the mass of the Sun is not going to stop compressing. And when you compress things, you raise their temperature. Take a box of stuff. Any stuff. Doesn’t matter. Now heat it up. A lot. No I mean really a lot. Keep heating it. As you heat stuff up, it breaks down into simple things. Solids become liquid. Liquids become gases. Eventually, gases become plasmas, which are superheated gases that behave a little differently than your average gas, so much so that plasma physics is its own branch.

So, when you’ve got a giant ball of gas, compressing under its own gravity, heating its core to millions of degrees, starting a continuous chain reaction of nuclear fusion, building hydrogen into deuterium and then helium, everything is so hot its not a gas, its just all a plasma.

Plus, you don’t want to be anywhere near a star that’s “on fire”. The closest thing I can think of is the thermonuclear reactions happening outside the core, which happens each time a star moves through heavier elements at the end of its life, each of which also causes the star to puff up (in the Sun’s case, going through red giant stages) and then eject outer layers. It looks pretty from far away - that’s what planetary nebulae are - but would be distressing up close…and hazardous, as the star grows. Also, if it’s bigger than the sun, there’s the possibility of a supernova of one kind or another. (Type II if it’s just big, but not big enough for gravitational collapse, Type I if it’s small enough to form a white dwarf, but has a nice companion to pull matter from.)

[End Angwe’s pedantic ass music!]

I like science. It’s fun.

(via APOD: 2012 October 11 - Aurorae over Planet Earth)
Holy cow! Thanks to the coronal mass ejection (CME) on the 4th/5th, we got a decent bit of aurorae on the 7th/8th as the charged particles from the Sun impacted the Earth’s magnetosphere, exciting oxygen and nitrogen in the upper atmosphere.
Shown here is a shot of North America (centered, a bit, on Chicago!) with the city lights shining through.
Aurorae over Planet Earth Image Credit : NASA, NOAA, GSFC, Suomi NPP, Earth Observatory, processing by Jesse Allen and Robert Simmon

(via APOD: 2012 October 11 - Aurorae over Planet Earth)

Holy cow! Thanks to the coronal mass ejection (CME) on the 4th/5th, we got a decent bit of aurorae on the 7th/8th as the charged particles from the Sun impacted the Earth’s magnetosphere, exciting oxygen and nitrogen in the upper atmosphere.

Shown here is a shot of North America (centered, a bit, on Chicago!) with the city lights shining through.

Aurorae over Planet Earth 
Image Credit : NASANOAAGSFCSuomi NPPEarth Observatory
processing by Jesse Allen and Robert Simmon

(via APOD: 2012 September 7 - IC 4628: The Prawn Nebula)
Image Credit & Copyright: Marco Lorenzi (Glittering Lights)
The world seems intent on putting me on a nebulae and cluster kick of late. Yesterday’s APOD shows the Prawn Nebula (IC 4628), just south of Antares, the heart of Scorpio, an emission nebula being powered the nearby hot, massive, young stars. As the ultraviolet radiation streams out from them, it strips electrons off the gas in the nebular cloud, mostly hydrogen, and ionizes it. As the hydrogen atoms reclaim electrons, they release the energy that was initially absorbed when the UV photon hit the atom and knocked the electron off. The resulting radiation is emitted at the wavelengths in the chemical signature of the atoms. As this gas cloud is mostly hydrogen, and the spectrographic signature of atomic hydrogen is largely red, we see mostly red light being emitted.
This is quite a large nebula, too, 250 light-years across, so that, at its distance of about 6,000 light-years, it appears as big as four full moons across on the sky.

(via APOD: 2012 September 7 - IC 4628: The Prawn Nebula)

Image Credit & Copyright: Marco Lorenzi (Glittering Lights)

The world seems intent on putting me on a nebulae and cluster kick of late. Yesterday’s APOD shows the Prawn Nebula (IC 4628), just south of Antares, the heart of Scorpio, an emission nebula being powered the nearby hot, massive, young stars. As the ultraviolet radiation streams out from them, it strips electrons off the gas in the nebular cloud, mostly hydrogen, and ionizes it. As the hydrogen atoms reclaim electrons, they release the energy that was initially absorbed when the UV photon hit the atom and knocked the electron off. The resulting radiation is emitted at the wavelengths in the chemical signature of the atoms. As this gas cloud is mostly hydrogen, and the spectrographic signature of atomic hydrogen is largely red, we see mostly red light being emitted.

This is quite a large nebula, too, 250 light-years across, so that, at its distance of about 6,000 light-years, it appears as big as four full moons across on the sky.

(via APOD: 2012 August 29 - A Dark Earth with a Red Sprite)
Image Credit: ISS Expedition 31 Crew, NASA
You may be having trouble seeing the phenomenon known as a “red sprite” unless you click all the way through to the full-size photo. It’s worth doing just for the awesome ISS shot of the Earth at night, but there’s also this:

That’s no anomaly of the camera, or the observation window, it’s an actual flash of red light above the lighting in a storm cloud. They’ve been reported before, but they weren’t photographed until 1989…quite by accident.
They’re mysterious phenomena to be sure, and may be related to other atmospheric lighting occurrences like blue jets or terrestrial gamma flashes.

(via APOD: 2012 August 29 - A Dark Earth with a Red Sprite)

Image Credit: ISS Expedition 31 CrewNASA

You may be having trouble seeing the phenomenon known as a “red sprite” unless you click all the way through to the full-size photo. It’s worth doing just for the awesome ISS shot of the Earth at night, but there’s also this:

That’s no anomaly of the camera, or the observation window, it’s an actual flash of red light above the lighting in a storm cloud. They’ve been reported before, but they weren’t photographed until 1989…quite by accident.

They’re mysterious phenomena to be sure, and may be related to other atmospheric lighting occurrences like blue jets or terrestrial gamma flashes.

(via APOD: 2012 August 28 - Colorful Clouds Near Rho Ophiuchi)
Image Credit & Copyright: Tom O’Donoghue
Oooh! A lesson in the forms and varieties of nebulae all in one picture. OK, so there are three main kinds of nebulae:
Reflection
Emission
Dark
They’re produced by different processes too, so here’s what’s going on above:
Rho Ophiuchi, the bright blue star in the center of the top blue nebula is emitting regular light that is being scattered off the dust in the nebular clouds. Dust particles tend to scatter blue light more than any other wavelength of light, so the reflected light from the nebula is blue. Hence, reflection nebulae look blue.
To the lower-right, you can see Sigma Scorpii, a bright blue star in the middle of a red nebula. When the ultraviolet radiation from a star hit gas clouds, made mostly from hydrogen, they ionize the gas, stripping the electrons off the atoms. Atoms don’t stay that way forever, though, and they have a tendency to pull an electron back at some point, de-ionizing themselves. When that happens, it releases energy in the form of electromagnetic radiation, usually as red light. We see the light being emitted from the gas as it de-ionizes.
Finally, in all those spots, mostly in the middle of the picture, where you might be worried that the photographer’s camera has some sensing issues, where we’re not seeing any background starlight, or really anything at all, those are areas where there’s too much dust, in the way, making a dark spot in the sky.
Oh, a couple other things:
Big, bright, red supergiant Antares in the lower middle is so red that even it’s reflected light is yellow-red.
M4 is the globular cluster just to right of Antares, an ancient relic of the universe, as are all the globular clusters we’ve ever seen. They orbit the Milky Way and are generally around 12-13 billion years old.
Boy do I love this astronomy stuff.

(via APOD: 2012 August 28 - Colorful Clouds Near Rho Ophiuchi)

Image Credit & Copyright: Tom O’Donoghue

Oooh! A lesson in the forms and varieties of nebulae all in one picture. OK, so there are three main kinds of nebulae:

  • Reflection
  • Emission
  • Dark

They’re produced by different processes too, so here’s what’s going on above:

Rho Ophiuchi, the bright blue star in the center of the top blue nebula is emitting regular light that is being scattered off the dust in the nebular clouds. Dust particles tend to scatter blue light more than any other wavelength of light, so the reflected light from the nebula is blue. Hence, reflection nebulae look blue.

To the lower-right, you can see Sigma Scorpii, a bright blue star in the middle of a red nebula. When the ultraviolet radiation from a star hit gas clouds, made mostly from hydrogen, they ionize the gas, stripping the electrons off the atoms. Atoms don’t stay that way forever, though, and they have a tendency to pull an electron back at some point, de-ionizing themselves. When that happens, it releases energy in the form of electromagnetic radiation, usually as red light. We see the light being emitted from the gas as it de-ionizes.

Finally, in all those spots, mostly in the middle of the picture, where you might be worried that the photographer’s camera has some sensing issues, where we’re not seeing any background starlight, or really anything at all, those are areas where there’s too much dust, in the way, making a dark spot in the sky.

Oh, a couple other things:

  1. Big, bright, red supergiant Antares in the lower middle is so red that even it’s reflected light is yellow-red.
  2. M4 is the globular cluster just to right of Antares, an ancient relic of the universe, as are all the globular clusters we’ve ever seen. They orbit the Milky Way and are generally around 12-13 billion years old.

Boy do I love this astronomy stuff.

mellifiedman
lazarus-taxon:

isolatedvertex:

penswordpress:

“If Satan plays miniature golf, this is his favorite hole. A ball struck at A, in any direction, will never find the hole at B — even if it bounces forever.
The idea arose in the 1950s, when Ernst Straus wondered whether a room lined with mirrors would always be illuminated completely by a single match.
Straus’ question went unanswered until 1995, when George Tokarsky found a 26-sided room with a “dark” spot; two years later D. Castro offered the 24-sided improvement above. If a candle is placed at A, and you’re standing at B, you won’t see its reflection anywhere around you — even though you’re surrounded by mirrors.”

Coolest thing on the “math” tag today.

super cool!!

While the light issue is true, since light always travels in a straight line (because we’re not anywhere near anything that has enough gravitation to really warp space that much), it’s not necessarily true of a miniature golf ball.
The advantage a golfer might have - or a pool player on a table shaped like this - is that balls roll, and have friction effects, and can be given spin. Which means the ball doesn’t have to roll in a straight line.
Now, to be perfectly honest, I couldn’t do it in mini-golf. I don’t have that kind of control with a golf club. I would, however, love to give it a try on a pool table.
Other incidental: light doesn’t always travel in a straight line. It’s more likely too, as the quantum paths near a straight line contribute most of the probability for the photon, but, quantum-mechanically, it doesn’t have to. Go read QED. Feynman explains it better.

lazarus-taxon:

isolatedvertex:

penswordpress:

“If Satan plays miniature golf, this is his favorite hole. A ball struck at A, in any direction, will never find the hole at B — even if it bounces forever.

The idea arose in the 1950s, when Ernst Straus wondered whether a room lined with mirrors would always be illuminated completely by a single match.

Straus’ question went unanswered until 1995, when George Tokarsky found a 26-sided room with a “dark” spot; two years later D. Castro offered the 24-sided improvement above. If a candle is placed at A, and you’re standing at B, you won’t see its reflection anywhere around you — even though you’re surrounded by mirrors.”

Coolest thing on the “math” tag today.

super cool!!

While the light issue is true, since light always travels in a straight line (because we’re not anywhere near anything that has enough gravitation to really warp space that much), it’s not necessarily true of a miniature golf ball.

The advantage a golfer might have - or a pool player on a table shaped like this - is that balls roll, and have friction effects, and can be given spin. Which means the ball doesn’t have to roll in a straight line.

Now, to be perfectly honest, I couldn’t do it in mini-golf. I don’t have that kind of control with a golf club. I would, however, love to give it a try on a pool table.

Other incidental: light doesn’t always travel in a straight line. It’s more likely too, as the quantum paths near a straight line contribute most of the probability for the photon, but, quantum-mechanically, it doesn’t have to. Go read QED. Feynman explains it better.

the-star-stuff
the-star-stuff:

Einstein was right, neutrino researchers admit
Scientists on Friday said that an experiment which challenged Einstein’s theory on the speed of light had been flawed and that sub-atomic particles — like everything else — are indeed bound by the universe’s speed limit.
Now it’s official: the notion that neutrinos could travel faster than the speed of light really was the result of a “faulty kit”.
Read the full article here.

From the article:

But CERN now says that the earlier results were wrong and faulty kit was to blame.
"Although this result isn’t as exciting as some would have liked, it is what we all expected deep down," said the centre’s research director Sergio Bertolucci.
"The story captured the public imagination, and has given people the opportunity to see the scientific method in action.
"An unexpected result was put up for scrutiny, thoroughly investigated and resolved in part thanks to collaboration between normally competing experiments. That’s how science moves forward."

Amen.

the-star-stuff:

Einstein was right, neutrino researchers admit

Scientists on Friday said that an experiment which challenged Einstein’s theory on the speed of light had been flawed and that sub-atomic particles — like everything else — are indeed bound by the universe’s speed limit.

Now it’s official: the notion that neutrinos could travel faster than the speed of light really was the result of a “faulty kit”.

Read the full article here.


From the article:

But CERN now says that the earlier results were wrong and faulty kit was to blame.

"Although this result isn’t as exciting as some would have liked, it is what we all expected deep down," said the centre’s research director Sergio Bertolucci.

"The story captured the public imagination, and has given people the opportunity to see the scientific method in action.

"An unexpected result was put up for scrutiny, thoroughly investigated and resolved in part thanks to collaboration between normally competing experiments. That’s how science moves forward."

Amen.