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AndrewM

Wed Sept 20 2006, 08:43PM

Registered Member #49 Joined: Thu Feb 09 2006, 04:05AM
Location: Bigass Pile of Penguins
Posts: 362

Lets see some dimensions for this fancy waveguide thinger, and I might be up for building it.

Dr. Slack

Wed Sept 20 2006, 10:06PM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

Now I've read his paper, I'm starting to do all sorts of thought experiments.

Consider a wide cylindrical cavity (simpler than conical). Photons travel pure axially, and bounce losslesly between two plane mirrors. Consider a pair of photons which bounce off the two mirrors at the same instant, producing two equal and opposite impulses. Now shift your frame of reference to observing this arrangement going hurtling by at 3km/s.

In my stationary frame, the photons still travel at 'c'. However the mirrors are doing 3km/s. This means that the photon hitting the back mirror will pick up energy and become blue-shifted, thus carrying more momentum, and when hitting the receding front mirror will become red-shifted and carry less. However, each mirror supplies the same delta (blue-red) or (red-blue) so the force at each end is still the same. So far, so good.

However, one casualty of relativity is simultaneity, and it bites by noticing that the front receding mirror gets hit slightly later than the rear advancing mirror. This phase shift appears to mean that the whole assembly is subject to a rearwards impulse for a small time before getting the frontwards impulse. The result of an impulse is a deltaV. Equal and opposite deltaVs seperated in time integrate to a small displacement. The displacemtnt occurs every photon transit, so that equates to a small net velocity.

Now what the hell's that about? I take a box of photons, and as a result of looking at it at a certain speed, it contrives to go at a different speed. What (if anything) have I done wrong?

It's nothing to do with Lorentz foreshortening. In our frame, the box has shrunk a little, and is the same front to back as well as back to front. In the frame of either photon, the box is zero-length.

I like the idea of reproducing the experiment by the way. In fact in terms of potentially ground-breaking science it's probably one of the most practical experiments to stage, I wouldn't be surprised if most of us haven't already got a magnetron or three lying about in the junk box.

Conundrum

Wed Sept 20 2006, 10:33PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

Still pretty interesting. I did however notice one minor detail in the original article, that the Q may well drop if the chamber is accelerated.

I'd have to do a detailed analysis to be sure but this in itself might be enough to verify CoE, in that acceleration is therefore impossible without moving reaction mass.

-A

AndrewM

Wed Sept 20 2006, 11:51PM

Registered Member #49 Joined: Thu Feb 09 2006, 04:05AM
Location: Bigass Pile of Penguins
Posts: 362

As I pondered the way (judging from the photograph) I might build this thing, and how I might test it, something struck me:

From the original article

Enclosed in an EMC enclosure for safety reasons... The force motor and microwave generator weigh only 9.4kg, the remaining weight is that of the EMC enclosure.

Why do you suppose it requires shielding?

Bjørn

Thu Sept 21 2006, 12:55AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

I believe that a careful engineer should always use shielding when working with invisible radiation that could cause permanent damage and or interfere with instruments.

If he added the shielding because he was cooking the environment then it is a bad sign but it might be completely innocent.

Simon

Thu Sept 21 2006, 02:31AM

Registered Member #32 Joined: Sat Feb 04 2006, 08:58AM
Location: Australia
Posts: 549

wrote ...

Don't get me wrong, I think this is almost certainly bull.
I'm just pointing out that if someone says "I have a toy that breaches the law of conservation of momentum" you can not logically say "That cannot be true because it would breach the law of conservation of momentum" as a refutation. (Of course, you an say that a zillion previous experiments have not shown that effect)
That would be the same argument as saying "I know God exists because it says so in the bible".

That's true but the other statement that goes, "I've used relativity to break the law of momentum conservation," is dodgy.

If you're going to put a prize on constructing a test, you might want to give specific details about what you want. You want a proper test.

wrote ...

Who here is studying EM field theory this semester? If you are, let's here from you!!!

I am. Maybe I'll read your notes later.

This story is relevant here. Remember that the only evidence that this works is a guy who likes this theory and has built this device and who claims it produces some incredibly tiny thrust.

wrote ...

In short, I am suprised that New Scientist published the article without running Shawyer's claims by someone with experience in electrodynamics. His mistake would have flunked him out of my EM theory class!

New Scientist is a pretty good magazine. I read it. In spite of that, New Scientist does jump on the occasional BS bandwagon. ZeoSync, the algorithm that compresses anything (great, I'll compress everything down to nothing...). The latest uncrackable coding scheme (i.e. "Here's a code I'm not smart enough to break!"). Etc, etc, etc. Publication in New Scientist is not a mark of authenticity.

Bored Chemist

Thu Sept 21 2006, 06:00AM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

Would this "work" with a tapered cylinder of gas?
The speeds of typical gas molecules are not close to c so the effect would be small but their mass is huge compared to a Âµwave photon.

WaveRider

Thu Sept 21 2006, 09:25AM

Registered Member #29 Joined: Fri Feb 03 2006, 09:00AM
Location: Hasselt, Belgium
Posts: 500

Bored Chemist: You bring up a very good point. I will add to your suggesttion by saying that sound-waves in a resonator could exhibit a similar effect (altho' the mechanics are slightly different, momentum transfer by wave energy is a fundamental effect). Sound waves in an acoustic waveguide exhibit phase and group velocities, just like EM waves.

SteveC: I'll give some thought to the resonator dimesions. I think Shawyer's resonator was quite large (altho' he gives no specific dimensions, resonant modes at 2.45 GHz are so close together in frequency that minor tweaking of the side wall was all that's needed to achieve resonance in one of the cavity modes).

Using a "dip wavemeter" approach is a convenient way to find resonance. The whole thing may need to be pressurised with dry nitrogen to avoid arcing when resonance is achieved at high power... Also, everything would need to be enclosed on a large balance (energy source, etc.) The desired effect is so small, great care would have to be taken to eliminate air currents, etc. for a fair experiment to be carried out.

Note that an experiment using light should work just as well if you have access to an optical lab and lasers.. A Fabry-Perot resonator with one spherical and a flat reflector will exhibit the same "tapered" field profile....but we don't have those side walls to press against.. Damn! How do those bloody waves stay confined with nothing to "push against" on the sides??!!!

A pertinent thought experiment on specular reflection to consider (hint: assume plane waves inpinging on mirror surface):

Dr. Slack

Thu Sept 21 2006, 01:08PM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

One thing that bugs me having read his v9.3 paper is that he says the thrusts he measures are consistent with his theory. Now his theory looks BS, because it ignores the walls, or rather assumes that the photon pressure is normal to the axis rather than normal to the wall surface - the latter true case generates precsiely the reverse force on the walls to balance the net difference between the flat ends. Early figures in that paper use free space arguments, it appears based on the relativistic idea that regardless of the speed of the engine, light in our frame or the engine's frame travels at 'c', to neglect the rest of the apparatus and consider only the end walls.

I wonder, call me suspcious if you like, whether he has a choke seal at each end isolating the walls, and the ends only are connected to his balance? This would be consistent with his implied assertion that the walls contribute nothing. Can you get a choke seal to maintain that Q? Just a thought. However, that sort of arrangement would be pretty far out when it would be far simpler to make the whole thing in one.

Waverider, your optical resolnator won't work, the light is travelling essentially axially at both ends, group velocity = c, so equal foce at each end. It's confined by being a diffraction limited beam, not by bouncing off those sidewalls which reduce the group velocity.

Bored Chemist

Thu Sept 21 2006, 05:25PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

I had a bit more of a think about the gas idea. I'm the first to admit that my maths is lousy and my understanding of special (or even general) relativity is pretty poor too.
Normally with a gas bottle- even a tapered one- the forces due to the pressure all cancel out- the same ought to be true with radiation pressure but- it is claimed- special relativity ensures this doesn't happen. There's somestrange "leftover" force.
I understand that all motion is "relativistic" rather than Newtonian, but for most things the difference is too small to notice. This guy's "magic" relativistic effect seems to be in addition to the expected Newtonian one (where all the forces cancel out) so how big is it?
If we got a tapered gas bottle of helium at room temperature and 1 bar pressure the atoms would be moving at roughly 1000 m/sec. Roughly 5 orders of magnitude less than C.

Lots of the equations associated with relativity seem to include a term in (v/c) squared.

Comparing Âµwave photons with a velocity of c; against helium atoms with a velocity roughly C/10^5 would sugest to me that the "magic" relativistic effect would be something like 10^10 times smaller for the gas.
Looks like a complete non- starter.

But, what this guy claims to be working with is radiation pressure- that's a very small effect. I can easily fill a gas bottle to 100 bar. On paper I can get 1000 bar with no difficulty.
Also because he is working with a mess of power cables; cooling fans; circulating DC currents in the earth's magnetic field etc. he's pushing it to measure the force acurately (because there are heaps of other forces to deal with). He seems to be strugling to get better than a resolution of 1 in 10^4 (a gram in 10 Kg).
For a gas bottle it's just that- a bottle with gas in it. I can weigh that in the lab to a part in 10^7 resolution easily (accuracy is another matter- but I just need to see if it changes when I put it upside down).
If I can get 10^7 times more pressure (and I think that's possible- do radiation pressures in this bloke's experiment get to a milibar or so?) and if I can get 10^3 fold better weight resolution then I'm on to a winner.

Best of all- this system needs no magnetron or other power source. I can get 2 of them pointing in oposite directions to produce a couple and rotate the shaft of a generator. I can use another pair to keep the stator from spinning.

Can someone who knows about relativity check this idea- if there's no "magic" difference between the effect of a photon and the effect of a helium atom then we have a free energy machine and we can call it a day (I will still cough up Â£100 for the first person to check it experimentally with a reasonable attempt to replicate the original work). It'd also help if someone could let me know what the radiation pressure in that waveguide of his is likely to be.

(yes, I know that variations of the air pressure will cause an apparent change in weight rather bigger than 1 in 10^7- that's why they invented vacuum balances)

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