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The proposed radio frequency (RF) resonant cavity thruster is unlike conventional thrusters and uses no reaction mass and emits no directional radiation. Designed using principles that are not supported by prevailing scientific theories, it apparently violates the law of conservation of momentum. The EmDrive, has roiled the aerospace world for the several years now, ever since it was proposed by British aerospace engineer Robert Shawyer. The essence of the claim is that by bouncing microwaves in a truncated cone, thrust will be produced out the open end. Most scientists have snorted at the idea, noting correctly that such a thing would violate physical laws. However, prestigious organizations like NASA have replicated the results showing thrusts.
MIT Technology Review has some reasoning on the subject, (possibly pay-walled) with a picture of the device. It's supposedly the so called unruh effect at play. When NASA tested the device, they measured with input of 17 W an average thrust of 91 µN (5.4 µN/W). A Chinese team used 2500 W and measured a thrust of 720 mN (288 µN/W). The expected radiation pressure is closer to 0.003 µN/W.
(Score: 1, Interesting) by Anonymous Coward on Friday April 22 2016, @09:23AM
Most scientists have snorted at the idea, noting correctly that such a thing would violate physical laws.
What kind of BS is that?
a. They certainly didn't note anything "correctly". That's akin to say, in 1915, "Newton's fanbois snorted at the idea of relativity noting correctly that such a thing would violate physical laws".
b. There is no such things as "violating physical laws". An experiment can only ever agree with or contradict a physical theory, for the latter we either find what's wrong with the experiment or adjust the theory (or we dump it altogether and write a new one). The former just shows "alright, for this experiment the theory applies fine" but it doesn't prove the theory globally.
(Score: 3, Insightful) by maxwell demon on Friday April 22 2016, @01:05PM
Of course there is. If such a violation is found and confirmed, you know that the law has only a limited range of applicability, and you've found a phenomenon beyond that range.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by bitstream on Friday April 22 2016, @02:40PM
The validity of laws seems to also depend on scale. Or rather their influence only have significant impact at a certain scale.
(Score: 2) by Capt. Obvious on Friday April 22 2016, @10:12PM
To use your 1915 example. It would be correctly noted that relatively violated [implictly implied: our codification of] physical laws (which it did, which is why they added that Newton's laws start breaking down when you go really fast. It would incorrectly noted that it violated physical laws because light moved at infinite speed. That is, it was already known to move at a finite speed.