Nov 15, 2022 07:23 PM
Nuclear Fusion Experiment Reveals Unexpected Physics Inside ‘Burning Plasma’
https://www.vice.com/en/article/5d34y5/n...ing-plasma
EXCERPT: . . . Now, a team led by Ed Hartouni, a physicist at LLNL, has revealed that particles inside burning plasmas have unexpectedly high energies that could open new windows into the exotic physics of fusion reactors, which “could be important for achieving robust and reproducible ignition,” according to a study published on Monday in Nature Physics.
“This is a new regime of plasma; NIF diagnostics have made it possible to study these things in ways we couldn't do before,” said Hartouni in a call with Motherboard that also included study authors Alastair Moore, a physicist at LLNL, and Aidan Crilly, a research associate in plasma physics at Imperial College London. “We're able to see things at a level that we hadn't been able to see before, and there are surprises with these plasmas in an actual laboratory.”
“It's a really exciting time for us to finally have an almost-igniting facility and experiments to understand this physics that we haven't really been able to understand before and begin to get to the point where we can think about what a future fusion facility might look like,” added Moore... (MORE - missing details)
How to think about relativity
https://www.quantamagazine.org/how-to-th...-20221114/
EXCERPT: . . . Still, there must be some way in which time is not like space, otherwise we’d just talk about four-dimensional space, rather than singling out time as deserving of its own label. And we’re not thinking of the arrow of time here — for the moment, we’re in a simple world with few moving parts, where entropy and irreversibility aren’t things we have to worry about.
The difference is this: In space, a straight line describes the shortest distance between two points. In space-time, by contrast, a straight path yields the longest elapsed time between two events. It’s that flip from shortest distance to longest time that distinguishes time from space.
By a “straight path” in space-time, we mean both a straight line in space and a constant velocity of travel. In other words, an inertial trajectory, one with no acceleration. Fix two events in space-time — two locations in space and corresponding moments in time. A traveler could make the journey between them in a straight line at constant velocity (whatever that velocity needs to be for them to arrive at the right time), or they could zip back and forth in a non-inertial path. The back-and-forth route will always involve more spatial distance, but less proper time elapsed, than the straight version.
Why is it like that? Because physics says so. Or, if you prefer, because that’s the way the universe is. Maybe we will eventually uncover some deeper reason why it had to be this way, but in our current state of knowledge it’s one of the bedrock assumptions upon which we build physics, not a conclusion we derive from deeper principles. Straight lines in space are the shortest possible distance; straight paths in space-time are the longest possible time... (MORE - missing details)
https://www.vice.com/en/article/5d34y5/n...ing-plasma
EXCERPT: . . . Now, a team led by Ed Hartouni, a physicist at LLNL, has revealed that particles inside burning plasmas have unexpectedly high energies that could open new windows into the exotic physics of fusion reactors, which “could be important for achieving robust and reproducible ignition,” according to a study published on Monday in Nature Physics.
“This is a new regime of plasma; NIF diagnostics have made it possible to study these things in ways we couldn't do before,” said Hartouni in a call with Motherboard that also included study authors Alastair Moore, a physicist at LLNL, and Aidan Crilly, a research associate in plasma physics at Imperial College London. “We're able to see things at a level that we hadn't been able to see before, and there are surprises with these plasmas in an actual laboratory.”
“It's a really exciting time for us to finally have an almost-igniting facility and experiments to understand this physics that we haven't really been able to understand before and begin to get to the point where we can think about what a future fusion facility might look like,” added Moore... (MORE - missing details)
How to think about relativity
https://www.quantamagazine.org/how-to-th...-20221114/
EXCERPT: . . . Still, there must be some way in which time is not like space, otherwise we’d just talk about four-dimensional space, rather than singling out time as deserving of its own label. And we’re not thinking of the arrow of time here — for the moment, we’re in a simple world with few moving parts, where entropy and irreversibility aren’t things we have to worry about.
The difference is this: In space, a straight line describes the shortest distance between two points. In space-time, by contrast, a straight path yields the longest elapsed time between two events. It’s that flip from shortest distance to longest time that distinguishes time from space.
By a “straight path” in space-time, we mean both a straight line in space and a constant velocity of travel. In other words, an inertial trajectory, one with no acceleration. Fix two events in space-time — two locations in space and corresponding moments in time. A traveler could make the journey between them in a straight line at constant velocity (whatever that velocity needs to be for them to arrive at the right time), or they could zip back and forth in a non-inertial path. The back-and-forth route will always involve more spatial distance, but less proper time elapsed, than the straight version.
Why is it like that? Because physics says so. Or, if you prefer, because that’s the way the universe is. Maybe we will eventually uncover some deeper reason why it had to be this way, but in our current state of knowledge it’s one of the bedrock assumptions upon which we build physics, not a conclusion we derive from deeper principles. Straight lines in space are the shortest possible distance; straight paths in space-time are the longest possible time... (MORE - missing details)