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More than 40 years ago, a leading relativity theorist made a surprising prediction. Whereas empty space should feel immeasurably cold to any observer gliding along at a constant speed, one who is accelerating, say because he's riding a rocket, would find empty space hot. This so-called Unruh effect seemed practically impossible to measure, but now four theorists claim they have devised a doable experiment that could confirm the underlying physics. Skeptics say it will do no such thing—but for contradictory reasons.
"The hope is that this will convince skeptics that the whole thing is coherent," says Stephen Fulling, a theoretical physicist and mathematician at Texas A&M University in College Station who was not involved in the work. But Vladimir Belinski, a theorist at International Network of Centers for Relativistic Astrophysics in Pescara, Italy, says, "The Unruh effect is nonsense, it's based on a mathematical mistake."
[...] The effect is too feeble to measure directly. To see the vacuum heat to 1 K, an observer would have to accelerate 100 quadrillion times faster than the best rocket can. But Daniel Vanzella, a theorist at the University of São Paulo in São Carlos, Brazil, and colleagues argue that it should be possible to detect the key thing—the fog of photons seen by the accelerating observer—by studying light radiated by electrons. [...] Vanzella and colleagues start their analysis in the accelerating frame, where they assume the circulating electrons encounter that fog of photons. The electrons will both absorb photons from and radiate photons into the fog. Weirdly, every event in the accelerated frame in which the electrons absorb or emit a photon corresponds to an event in the lab frame in which the electrons emit a photon. The theorists use relativity theory to predict the spectrum of emitted photons in the lab frame, as they report in a paper in press at Physical Review Letters.
The Unruh effect (or Fulling–Davies–Unruh effect) "is the prediction that an accelerating observer will observe blackbody radiation where an inertial observer would observe none. In other words, the background appears to be warm from an accelerating reference frame; in layman's terms, a thermometer waved around in empty space, subtracting any other contribution to its temperature, will record a non-zero temperature. The ground state for an inertial observer is seen as in thermodynamic equilibrium with a non-zero temperature by the uniformly accelerating observer."
(Score: 2) by kaszz on Tuesday April 18 2017, @11:18PM (2 children)
So to accomplish increased temperature with 1 kelvin, one needs to accelerate to the order of 10^20 m/s².
However there seems to be three upper limits to acceleration:
0) Planck acceleration is a object that goes from zero to speed of light in one Planck time.
1) If the mass of a object is given then Caianiello's maximal acceleration: a=(2mc³)/h
2) If the length of a object is given then another acceleration limit exist: a=c²/L
For example an electron:
0) 5.560815 * 10^51
1) a=(2mc³)/h =(2*9.10938356e-31*299792458³)/1.054571800e-34 = 4.654842 * 10^29
2) c²/(2*2.81794e-15) = 1.594702 * 10^-31
Thus a accelerated electron will only heat up to 4.7 * 10^9 kelvin due to any unruh effect. So there seems to be a upper limit to acceleration induced thermal effects.
If electrons can radiate photons into the fog (of unruh I presume) then it should be possible to exploit that effect to make something accelerate massively by emitting the equivalent of a 1 kelvin temperature increase. Will it work both ways?
Which makes me think of the RF resonant cavity thruster [wikipedia.org] (EMdrive) which uses ~1 kW microwave energy for ~15 seconds before the effect takes place continuously by exerting a ~30 gram "unexplained" thrust. Could this be a engine that transfers power into said fog of unruh (using virtual particles) ? There should be a more efficient path of power transfer where you essentially could beam power directly into unruh fog. Seems the EMdrive is inefficient because it essentially has a gigantic impedance mismatch.
Btw, you can build your own EMdrive right now. Just don't expect to hoover anytime soon.
(Score: 2) by takyon on Tuesday April 18 2017, @11:25PM (1 child)
Or you can just build it vicariously:
https://forum.nasaspaceflight.com/index.php?board=73.0 [nasaspaceflight.com]
https://forum.nasaspaceflight.com/index.php?topic=41732.3520 [nasaspaceflight.com]
It's a lot easier that way.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by kaszz on Tuesday April 18 2017, @11:42PM
Vicariously.. well it's kind of more fun to test it by oneself. Even if the performance so far sucks ;)
Found some interesting comments in the last link though:
establish a "force locked loop", rather than a phase locked loop. The phenomena of interest is the thrust versus input power. If you could train your system to have the microwave source frequency (and, ideally, phase) track the "horizontal" signal to achieve and maintain a maximum horizontal displacement, you'd be home free.
I completely agree with the idea of a "force locked loop" configuration. There have been many ideas raised here such as exploring the relationship of AM vs FM modulation and thrust which could lead to genuine breakthroughs. For instance, it has been mentioned by Shell that she along with TheTraveller and rmfwguy have experienced anomalous high thrust transients. Shell also mentioned in this forum that the accelerator folks also have experienced them.
These aspects should be testable with relative ease provided a controllable power RF source and fast control loop.