Feb 4, 2021 02:23 AM
Turbulence trouble
https://cosmosmagazine.com/science/physi...e-trouble/
INTRO: “When I meet God,” physicist Werner Heisenberg allegedly once said, “I’m going to ask him two questions: why relativity? And why turbulence? I really believe he’ll have an answer for the first.”
Although the quote is almost certainly fictional, it captures the sheer frustration many physicists feel about turbulence: the complex, chaotic, unpredictable flows in fluids.
This phenomenon surrounds us: swirling gases in the atmosphere disrupting our flights; the movement of rivers around rocks; the flow of blood through our arteries. We also see it on cosmic scales, explains quantum physicist Warwick Bowen from the University of Queensland (UQ), from gas flowing in galaxy clusters to the Great Red Spot – a massive cyclone on Jupiter.
“You could fit our planet within this one storm, and it’s existed for many hundreds of years – for the whole time that we’ve been able to observe Jupiter,” Bowen says. This long-term stability is typical of turbulent phenomena but is utterly perplexing to physicists like Bowen, who are used to seeing order dissipate into disorder.
“There’s a natural tendency in physics for structures that are large to break down into smaller structures and eventually disappear,” he says. “But it seems that in the Great Red Spot of Jupiter, that doesn’t happen – these large structures are stable over very long periods of time.”
And we still don’t know why. Turbulence has always been too complex to accurately analyse or even measure. Even after centuries of study, physicists have no general theoretical description of it – it’s been described as the last great outstanding problem of classical physics... (MORE)
What is luminosity?
https://www.symmetrymagazine.org/article...luminosity
EXCERPTS: . . . As you may have noticed, when physicists talk about particle collisions, they talk about a measurement called luminosity. It doesn’t tell scientists exactly how many particle collisions are happening inside a collider; rather, luminosity measures how tightly packed the particles are in the beams that cross. The tighter the squeeze, the more likely it is that some of the particles will collide.
In the HL-LHC, 220 billion protons are expected to pass through another 220 billion protons every 25 nanoseconds at the accelerator’s four experimental intersections. But the vast majority of the protons will not actually interact with one another. Even with today’s best beam-focusing technology, the odds of a proton colliding with another proton inside the LHC ring is still significantly less than the odds of winning the Mega Millions Jackpot.
Protons aren’t solid orbs that bounce, break or shatter when they come into contact with each other. Rather, they are messy packages of fields and even smaller particles called quarks.
Two protons could pass right through each other, and there’s a chance all they would do is replay that scene from the movie Ghost in which actor Patrick Swayze, playing the titular phantom, sticks his ethereal head into a moving train—to no effect. You can bring the protons into a head-on collision, but you can’t make them interact.
[...] Collisions are complicated. So physicists talk about luminosity instead. The rate at which particles are brought together to collide is called “instantaneous luminosity.” [...] Considering an average LHC fill lasts between 10 and 20 hours, the number of potential collisions can climb very quickly. So scientists don’t just care about instantaneous luminosity; they also care about “integrated luminosity,” how many potential collisions accumulate over those hours of running.
The difference between instantaneous luminosity and integrated luminosity is the difference between, “Right now I’m driving at 60 miles per hour,” and “Over ten hours, I drove 600 miles.” (MORE - details)
https://cosmosmagazine.com/science/physi...e-trouble/
INTRO: “When I meet God,” physicist Werner Heisenberg allegedly once said, “I’m going to ask him two questions: why relativity? And why turbulence? I really believe he’ll have an answer for the first.”
Although the quote is almost certainly fictional, it captures the sheer frustration many physicists feel about turbulence: the complex, chaotic, unpredictable flows in fluids.
This phenomenon surrounds us: swirling gases in the atmosphere disrupting our flights; the movement of rivers around rocks; the flow of blood through our arteries. We also see it on cosmic scales, explains quantum physicist Warwick Bowen from the University of Queensland (UQ), from gas flowing in galaxy clusters to the Great Red Spot – a massive cyclone on Jupiter.
“You could fit our planet within this one storm, and it’s existed for many hundreds of years – for the whole time that we’ve been able to observe Jupiter,” Bowen says. This long-term stability is typical of turbulent phenomena but is utterly perplexing to physicists like Bowen, who are used to seeing order dissipate into disorder.
“There’s a natural tendency in physics for structures that are large to break down into smaller structures and eventually disappear,” he says. “But it seems that in the Great Red Spot of Jupiter, that doesn’t happen – these large structures are stable over very long periods of time.”
And we still don’t know why. Turbulence has always been too complex to accurately analyse or even measure. Even after centuries of study, physicists have no general theoretical description of it – it’s been described as the last great outstanding problem of classical physics... (MORE)
What is luminosity?
https://www.symmetrymagazine.org/article...luminosity
EXCERPTS: . . . As you may have noticed, when physicists talk about particle collisions, they talk about a measurement called luminosity. It doesn’t tell scientists exactly how many particle collisions are happening inside a collider; rather, luminosity measures how tightly packed the particles are in the beams that cross. The tighter the squeeze, the more likely it is that some of the particles will collide.
In the HL-LHC, 220 billion protons are expected to pass through another 220 billion protons every 25 nanoseconds at the accelerator’s four experimental intersections. But the vast majority of the protons will not actually interact with one another. Even with today’s best beam-focusing technology, the odds of a proton colliding with another proton inside the LHC ring is still significantly less than the odds of winning the Mega Millions Jackpot.
Protons aren’t solid orbs that bounce, break or shatter when they come into contact with each other. Rather, they are messy packages of fields and even smaller particles called quarks.
Two protons could pass right through each other, and there’s a chance all they would do is replay that scene from the movie Ghost in which actor Patrick Swayze, playing the titular phantom, sticks his ethereal head into a moving train—to no effect. You can bring the protons into a head-on collision, but you can’t make them interact.
[...] Collisions are complicated. So physicists talk about luminosity instead. The rate at which particles are brought together to collide is called “instantaneous luminosity.” [...] Considering an average LHC fill lasts between 10 and 20 hours, the number of potential collisions can climb very quickly. So scientists don’t just care about instantaneous luminosity; they also care about “integrated luminosity,” how many potential collisions accumulate over those hours of running.
The difference between instantaneous luminosity and integrated luminosity is the difference between, “Right now I’m driving at 60 miles per hour,” and “Over ten hours, I drove 600 miles.” (MORE - details)