[Aireal]

Qfwfq
Thanks for pointing out that EM is basicly massless so a lot of energy is used for a given thrust when compaired to a normal reaction drive. That is one of the reasons why I felt it would be impracticle as an engine. Nor do I believe that the conversation momentum is being circumvented by a loophole of wave theory, such loopholes do not exist that I am aware of. Rather I am trying to find out how the thrust is achived without voilating conversation of momentum. This device was created by respectable scientists, so I doubt that the recordings of observed thrust are in error, or that the concept is compleatly crackpot. So the question remains, How this this effect occur?

One of the things I would like to check is to see if the is any red shifting of the EM radiation from this process to account for the lost energy of momentum. Without access to their research notes and a working model to use in testing, all I can do is conjecture as to its cause. I have a couple of ideas, some of them the math will drive me crazy trying to solve, others I can not test without experimentation.

So back to what I said in my first post. I think this might make a good research tool, or a device for grad students to test classroom theory on, but as an engine for space travel, not, it is too inefficent and impracticle.

[wade_b]

Another way to think of the em-drive....

Does a laser exhibit recoil?

Yet, it emits a large amount of directed energy from one side...

So - doesn't it stand to reason, that the emission of nearly massless particles from the magnetron into a tuned cavity, can impart mass to the far wall of the tuned cavity?

Newtonian physics don't apply here - again, does the laser exhibit a force vector in direct opposition to it's directed energy?

[modest]

wade_b said:

Does a laser exhibit recoil?

Yes.

Quote

In stimulated emission an excited state atom emits a photon in the direction of an incident photon and returns to the ground state. The incident photon causes no recoil in the atom but the emitted photon causes a recoil opposite the incident photon. Figure 1.4 shows conservation of momentum in stimulated emission. We can see that although the total momentum of the system is zero the atom has a recoil opposite the incident photon.

Section I: Theoretical Principles

Is this what you were thinking?

~modest

[wade_b]

modest said:

Yes.

Is this what you were thinking?

~modest

That is interesting but expected behavior on the particle level.

The real question: is that recoil measurable in the laser itself, and does it follow the rules of Newtonian physics?

I'm searching really for a good abstraction for the relativistic notion of an "open system" as applied to the emission device in the tuned cavity.

[wade_b]

This really does seem impossible, even when applying the Einstein Elevator and changing the reference frame.

If I understand correctly, the law of conservation of momentum still applies inside the elevator.

The model I studied shows a force vector being applied from outside the elevator; the perception of momentum inside the elevator would be 0.

So I'm not quite seeing how a force generated inside the elevator could translate into momentum measured outside of it?

[modest]

wade_b said:

That is interesting but expected behavior on the particle level.

I think so too.

wade_b said:

The real question: is that recoil measurable in the laser itself, and does it follow the rules of Newtonian physics?

Not sure exactly what you mean by Newtonian physics, but lasers surely follow conservation of momentum. They follow Newton's first law - the law of inertia. They do recoil.

wade_b said:

I'm searching really for a good abstraction for the relativistic notion of an "open system" as applied to the emission device in the tuned cavity.

Once again, I'm a bit confused by what you mean. When you say "open system" do you mean a "relativity drive" that looses photons into open space? If so, that is a perfectly normal thing to consider as a rocket engine. Qfwfq touched on that earlier in post #10. A well-focused laser could essentially work as a rocket engine. The laser does have recoil equal to the momentum of the photons leaving the craft.

wade_b said:

This really does seem impossible, even when applying the Einstein Elevator and changing the reference frame.

That surely seems to be the consensus of the thread.

wade_b said:

If I understand correctly, the law of conservation of momentum still applies inside the elevator.

I think it's a safe bet that conservation laws always apply.

wade_b said:

The model I studied shows a force vector being applied from outside the elevator; the perception of momentum inside the elevator would be 0.

So I'm not quite seeing how a force generated inside the elevator could translate into momentum measured outside of it?

I don't see how it would work either. As Will said, there's nothing you can do inside the elevator to move its center of mass. So, it's not going to accelerate. Unless some mass leaves the craft or some force acts on the craft - it's not going to accelerate.

~modest

[wade_b]

modest said:

I don't see how it would work either. As Will said, there's nothing you can do inside the elevator to move its center of mass. So, it's not going to accelerate. Unless some mass leaves the craft or some force acts on the craft - it's not going to accelerate.
~modest

I'm guessing that some mass is leaving the craft somehow; I don't really doubt that the engine works, I just have doubt that the engine works as he describes it.

In the end, this drive may still prove to be a viable replacement for ion thrusters.

My other comments were I suppose feeble attempts to understand Shawyer's rationale of his device as an open system; he is essentially viewing the emitter as not attached to the mass of the device itself, which SEEMS (to me) to be the basis of his insistence that this device does not break existing laws of physics.

Thanks for your patience with me - I'm still learning....

[wade_b]

But what of the laser gyro?

I mean - if I understand correctly, if the rotation of the laser gyroscope is in the opposite direction to the beam of light contained within, that beam of light takes correspondingly longer to reach the fixed target within the ring.

This seems to somewhat defy the simple Einstein elevator model...

In fact, could it not be deduced that the laser beam is not confined to the elevator?

My head is spinning.

[wade_b]

I think this is what I was grasping for when asking about the recoil as seen by the laser apparatus: (from wikipedia's page "Newton's_laws_of_motion" I'm not allowed to post URL's...)

Quote

Newton used the third law to derive the law of conservation of momentum;[24] however from a deeper perspective, conservation of momentum is the more fundamental idea (derived via Noether's theorem from Galilean invariance), and holds in cases where Newton's third law appears to fail, for instance when force fields as well as particles carry momentum, and in quantum mechanics.

[CraigD]

wade_b said:

Does a laser exhibit recoil?

wade_b said:

The real question: is that recoil measurable in the laser itself, and does it follow the rules of Newtonian physics?

Yes.

The momentum of light, be it from a lightbulb, a laser, a microwave or radio antenna, etc, is easy to describe. It’s energy divided by the speed of light. Force = momentum/time and Power = energy/time, so the force of light is Power/c

A couple of examples:

• A typical laser pointer (I use one of these as a cat toy)
  
  • Power: <0.001 W
  • Force: 0.001 / c = about 3e-12 N
  • Mass: about 0.005 kg
  • Acceleration: Force / Mass = about 6e-10 m/s/s
    
  • Example consequence: Left turned on free-floating in space for about 53 years, if pointed the same direction, my cat-toy laser pointer would increase its velocity in the opposite direction by about 1 m/s, a slow walking speed. (It’s batteries don’t last nearly that long, I can attest )
• A weak old microwave oven (Like nearly every American, I have one of these)
  
  • 100 W (output power, not input)
  • Force: about 3e-6 N
  • Mass: about 10 kg
  • Acceleration: about 6e-7 m/s/s
    
  • Example consequence: If you cut its side off (my microwave emits photons from the side of its interior where the buttons are), it would accelerate itself to 1 m/s in about 19 days. However, when you throw in the necessary hardware to keep it supplied with power for 19 days, the system becomes much more massive

As best I can tell, what Shawyer’s proposing is similar to my microwave oven example, but without cutting the side open. This results in just a microwave oven, which will accelerate slightly in the opposite direction of any leaks in its oven compartment (I understand the window and door edges leak a little on most of them), an unintentional effect which I assume Shawyer’s system wouldn’t have, being sealed better than a microwave oven.

A more mundane example is a person standing on a sled on an frozen lake, propelling himself by pitching softballs. Shawyer’s proposes that you can propel the sled using just one softball that you pitch repeatedly to a friend also standing on the sled, if he has a catcher’s mitt that’s designed a special way.

[wade_b]

What about this (from physorg.com)

Quote

One of the interesting phenomena present in quantum mechanics is the Aharonov-Bohm (AB) effect. The AB effect predicts that a charged particle, usually an electron in experiments, shows effects from electromagnetic fields in regions where the particle is excluded. This leads to the interesting fact that, in electromagnetism, Newton’s Third Law of Motion doesn’t always hold true.

Herman Batelaan explains to PhysOrg.com: “If you want to move anything in the world around you, you need forces. But in the Aharonov-Bohm effect, the electron reacts without any forces. There is no force, but something happens.”

Batelaan, a scientist at the University of Nebraska-Lincoln oversaw an experiment done by graduate student, Adam Caprez, and Brett Barwick to demonstrate the absence of forces in the AB effect. A description of the experiment, and their results, is available in Physical Review Letters: “Macroscopic Test of the Aharonov-Bohm Effect.”

“The interesting thing,” Batelaan says, “is that experimentally scientists have detected evidence of this effect, and it is mentioned in textbooks. But nobody had shown that no forces are there.” The experiment performed at the University of Nebraska-Lincoln constitutes the first demonstration of a lack of forces. “We know the effects, and this is expected.” Batelaan continues. “Theoretically, scientist predicted this, but we want to see this. Now we have it.”

Experimental demonstrations of the AB effect usually include carefully controlled electrons using a distant electromagnetic field. “We understand the physics of this, such that we can take electrons and control them so well that we can see quantum mechanics happening,” Batelaan says. In order to perform the current experiment, the team used a pulse laser to hit a metal needle, a method developed at Stanford.

[wade_b]

I'm also currently trying to wrap my head around Minkowski forces; as described by Gary L. Mathis (and no doubt others), the Minkowski force associated with the center of mass of a system does not represent the total force acting on a system.

Perhaps the "impossible drive" is truly possible.

[wade_b]

If the emdrive works as described, I believe it would be a practical application of Einstein's box:

Google: 2005_dissertation_The_Abraham-Minkowski_Controversy.pdf
Google: Einstein's box

Can the emdrive possibly be a real implementation of Einstein's box?

Discuss?

[CraigD]

wade_b said:

What about this (from physorg.com)

Quote

One of the interesting phenomena present in quantum mechanics is the Aharonov-Bohm (AB) effect. The AB effect predicts that a charged particle, usually an electron in experiments, shows effects from electromagnetic fields in regions where the particle is excluded. This leads to the interesting fact that, in electromagnetism, Newton’s Third Law of Motion doesn’t always hold true.

Herman Batelaan explains …

Caprez, Barwick, and Batelaan’s 8/17/07 “A macroscopic test of the Aharonov-Bohm effect” describes an experiment that further confirms that the quantum waves of an electrons in a stream, which are predicted to be affected in the absence of an interaction analogous to classical electromagnetic force, are not actually being affected by an unexpected interaction analogous to a classical electromagnetic force.

What is changed by the AB effect is the phase of electrons’ waves, resulting in a detectable change in the interference pattern produced by passing a stream of electrons through two slits – the famous two-slit experiment. Their masses and velocities are unaffected. Newton’s 3rd Law of Motion describes forces, masses, and velocities, not the wave nature of particles, I think the tagline “in electromagnetism, Newton’s Third Law of Motion doesn’t always hold true”, while catchy, isn’t accurate. It plays on different uses of the word “reaction”: in classical physics, where reactions are changes in momenta, vs. in quantum physics, where “reaction” can be a rarely-used synonym for “interaction”, which can involve changes other than to momenta The word “reaction” appears nowhere in Caprez, Barwick, and Batelaan’s paper.

The AB effect expressly doesn’t change momenta, so I can see no way that it can be used for propulsion.

[wade_b]

CraigD said:

Caprez, Barwick, and Batelaan’s 8/17/07 “A macroscopic test of the Aharonov-Bohm effect” describes an experiment that further confirms that the quantum waves of an electrons in a stream, which are predicted to be affected in the absence of an interaction analogous to classical electromagnetic force, are not actually being affected by an unexpected interaction analogous to a classical electromagnetic force.

What is changed by the AB effect is the phase of electrons’ waves, resulting in a detectable change in the interference pattern produced by passing a stream of electrons through two slits – the famous two-slit experiment. Their masses and velocities are unaffected. Newton’s 3rd Law of Motion describes forces, masses, and velocities, not the wave nature of particles, I think the tagline “in electromagnetism, Newton’s Third Law of Motion doesn’t always hold true”, while catchy, isn’t accurate. It plays on different uses of the word “reaction”: in classical physics, where reactions are changes in momenta, vs. in quantum physics, where “reaction” can be a rarely-used synonym for “interaction”, which can involve changes other than to momenta The word “reaction” appears nowhere in Caprez, Barwick, and Batelaan’s paper.

The AB effect expressly doesn’t change momenta, so I can see no way that it can be used for propulsion.

Thanks for the explanation - I came to a similar conclusion after reading more data on that effect. AB is a phase change then...

What to make of Einstein's box?

I can only understand the first cycle, which shows the "recoil" from the emitted particle being transferred to the cylinder (v = e/Mc); then when the particle hits the far wall the cylinder comes to rest, due to energy to matter conversion: m = E/C(squared). (Feel free to correct me - I'm still learning )

What floors me though is the reference to energy absorption on Wall B and the massless carrier required to return energy to Wall A, and the assertion that such transference will NOT result in a change of position of the cylinder.