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Several points: 1) "Foundations of Physics" is closer to a philosophy journal than a physics journal. It's full of fascinating stuff, but it's far more specula

Several points: 1) "Foundations of Physics" is closer to a philosophy journal than a physics journal. It's full of fascinating stuff, but it's far more speculative than any other legitimate journal. When libraries were cutting budgets in the '80's and '90's it was generally the first to go. 2) When highly theoretical phenomena are talked about in engineering terms, the odds of confirmation bias are huge. Who wouldn't want a reactionless-ish thruster? 3) Measuring transient forces of the kind being applied here is extremely hard, and the number of confounding factors is extremely large. The article mentions a mu-metal shield, which will screen some of the Earth's magnetic field from the apparatus but which is useless for screening transient magnetic fields, which get generated by transient electric fields thanks to the magic of Maxwell. Ampere's law tells us CurlB = mu_0epsilon_0dE/dt. So the possibility of residual electro-magnetic forces is non-trivial to say the least, particularly in a room full of conductors and time-varying EM-fields (from the wiring, the pump, etc). Putting the whole apparatus in a Faraday cage would help, but the history of measuring small (and transient) forces in physics in the past couple of decades (the fifth force mess, Joe Weber's coherent neutrino scattering work) argues that we take these experimental measurements with a large grain of salt, unless they can be shown to be in precise numerical agreement with the theory's predictions over an order of magnitude variation in power input and rate of variation. The theory may not be wrong, but it needs a lot more experimental investigation and likely theoretical examination as well. Theorists tend not to spend a lot of time critiquing things that look really likely to be wrong, because proving something that everyone thinks is probably wrong, wrong can be incredibly time-consuming and utterly unrewarding. So the lack of theoretical disproof is not very compelling. So far as I know Joe Weber's coherent scattering theory was never dis-proven in publication, either: it was mostly dismissed by informal but compelling arguments at conferences (the best one was simply that there was nothing special about neutrinos in Weber's theory, so if what he said was correct single crystals would coherently scatter x-rays in exactly the same way, which would have shown up as an anomalous low-energy contribution to EM cross-sections that would have been an obvious problem for decades if anyone had observed it.)

api 12y ago
"When highly theoretical phenomena are talked about in engineering terms" That may be true, but you also mention that measuring tiny transient forces is incredibly hard. Thus, the only way to actually get an accurate measurement for this thing is to attempt to scale it up until the force is either unambiguous or the confounding culprit can be found. You've got to try to amplify the signal. I also don't get the impression that these folks are dummies. I'd be surprised if they haven't done experiments to attempt to rule out electromagnetic effects. Simple ones would involve moving stuff around, doing this in the presence of various magnetic fields imposed by outside sources to see if the underlying effect is still there, etc. Edit: some more info here: https://en.wikipedia.org/wiki/Woodward_effect#Test_devices https://en.wikipedia.org/wiki/Woodward_effect#Test_devices In particular: "In 2004, Paul March of Lockheed Martin Space Operations, who started working in this research field as of 1998, presented successful replication of Woodward's previous experiments at STAIF." There are a few other less conclusive attempts at replication, but only one claimed negative result. But as you say, measuring forces this tiny is hard.
- tjradcliffe 12y ago
  Check out the comment from dnautics below, which has a link to a really nice description by one of the experimenters, who was a grad student of Woodward's. I agree these people aren't dummies, but when effects scale down in step with the sensitivity of the apparatus there is something fishy going on. The description on the Great Wiki actually made me more suspicious of the device, not less.
baq 12y ago
> Who wouldn't want a reactionless-ish thruster? anyone who understands that it's a device for turning bricks into weapons of mass destruction. not that a conventional nuclear reactor isn't one, it's just that it uses more sophisticated bricks.
- mikeash 12y ago
  You should check out these things called "rockets" that have been doing that for many decades now.
  - baq 12y ago
    i don't know of a rocket that could effortlessly accelerate a rock to a nontrivial percentage of c, which would be within a reactionless drive's capability, given enough time. see also http://www.projectrho.com/public_html/rocket/reactionlessdrive.php http://www.projectrho.com/public_html/rocket/reactionlessdri....
    - mikeash 12y ago
      Reactionless doesn't mean "free." This device requires a vast energy input. I have no idea how efficient it could get if it's developed (assuming the effect is real in the first place), but I doubt it would come anywhere close to "effortlessly."
    - oakwhiz 12y ago
      >effortlessly A reactionless drive, if possible, would still require "effort" to produce thrust in the form of energy. It is not a "free energy" device. The only difference between a reactionless drive and a rocket is that a rocket must carry its own fuel with it, so that it can expel the fuel to generate thrust. The fuel adds additional mass to the whole rocket, so in a way, a rocket requires extra fuel to carry its fuel. Since a reactionless drive does not expel anything, a reactionless drive would not carry any fuel, and therefore could be more efficient by way of lower mass, but it would still need to carry an energy source of some type, such as a nuclear reactor, or a radioisotope thermoelectric generator. Rockets are certainly capable of accelerating a mass to a significant fraction of the speed of light. However it is important to note that it becomes more difficult to accelerate an object as the object gets closer to the speed of light. You need more energy to add a constant amount of velocity as your current velocity increases. This applies regardless of what kind of method you are using to accelerate - doesn't matter if it's a rocket or a reactionless drive. The difference is only in efficiency - it is thought that a reactionless drive might be more efficient. However if a reactionless drive really is possible, it might provide a lot less thrust than you think. So even if reactionless drives are developed, they might be more efficient than rockets, but far less timely. I think you'd be waiting quite a while for the reactionless vehicle to attain any sort of appreciable velocity - perhaps decades. As far as weapons go, humans have not met any aliens yet (to my knowledge) and our species currently only resides on planet Earth, so any weapon would be ballistic in nature, to strike targets on Earth's surface. A reactionless drive would be ill-suited for ballistic propulsion because it doesn't give enough thrust. If it was launched from the ground like an ICBM on a suborbital trajectory, it wouldn't be able to escape Earth's gravity, it would just sit on the launch pad. If it was placed into orbit using a rocket as a first stage, and then activated later, it would take a while to deorbit rather gently. The vehicle's velocity would slow down due to air resistance, and its kinetic energy would not be usable as a mass destructive weapon. This is why large explosions are used as weapons of mass destruction, and not kinetic energy alone. Kinetic energy is simply used for timely delivery of the explosive device from a great distance away. Now, for interstellar warfare, a reactionless drive could be useful if you were extremely angry at another planet in another star system located many light-years away. The large distance between the aggressor and the victim allows the kinetic vehicle a lot of time to accumulate velocity. However the steering of such a kinetic weapon must be very precise in order to hit the target planet, so the vehicle must have the means to estimate its current location/speed/direction, compute the orbits of itself and its target, and apply the necessary course corrections in order to hit that target. It is possible that a reactionless drive might provide vectored thrust, but if it does not, then attitude adjustment thrusters would be needed (either reactionless or conventional.) Accurately steering a vehicle traveling near the speed of light does not seem like an easy task. If the target was missed, the vehicle would be traveling so quickly that it would escape the star system on a hyperbolic escape orbit. Such a weapon would be quite the undertaking and would be a large energy expenditure for a civilization. It might be more worth it to focus that energy into colonization and defense instead.
glomph 12y ago
Speculative articles about technology/science are not philosophy.

api 12y ago

"When highly theoretical phenomena are talked about in engineering terms" That may be true, but you also mention that measuring tiny transient forces is incredibly hard. Thus, the only way to actually get an accurate measurement for this thing is to attempt to scale it up until the force is either unambiguous or the confounding culprit can be found. You've got to try to amplify the signal. I also don't get the impression that these folks are dummies. I'd be surprised if they haven't done experiments to attempt to rule out electromagnetic effects. Simple ones would involve moving stuff around, doing this in the presence of various magnetic fields imposed by outside sources to see if the underlying effect is still there, etc. Edit: some more info here: https://en.wikipedia.org/wiki/Woodward_effect#Test_devices https://en.wikipedia.org/wiki/Woodward_effect#Test_devices In particular: "In 2004, Paul March of Lockheed Martin Space Operations, who started working in this research field as of 1998, presented successful replication of Woodward's previous experiments at STAIF." There are a few other less conclusive attempts at replication, but only one claimed negative result. But as you say, measuring forces this tiny is hard.

tjradcliffe 12y ago
Check out the comment from dnautics below, which has a link to a really nice description by one of the experimenters, who was a grad student of Woodward's. I agree these people aren't dummies, but when effects scale down in step with the sensitivity of the apparatus there is something fishy going on. The description on the Great Wiki actually made me more suspicious of the device, not less.

baq 12y ago

> Who wouldn't want a reactionless-ish thruster? anyone who understands that it's a device for turning bricks into weapons of mass destruction. not that a conventional nuclear reactor isn't one, it's just that it uses more sophisticated bricks.

mikeash 12y ago
You should check out these things called "rockets" that have been doing that for many decades now.
- baq 12y ago
  i don't know of a rocket that could effortlessly accelerate a rock to a nontrivial percentage of c, which would be within a reactionless drive's capability, given enough time. see also http://www.projectrho.com/public_html/rocket/reactionlessdrive.php http://www.projectrho.com/public_html/rocket/reactionlessdri....
  - mikeash 12y ago
    Reactionless doesn't mean "free." This device requires a vast energy input. I have no idea how efficient it could get if it's developed (assuming the effect is real in the first place), but I doubt it would come anywhere close to "effortlessly."
  - oakwhiz 12y ago
    >effortlessly A reactionless drive, if possible, would still require "effort" to produce thrust in the form of energy. It is not a "free energy" device. The only difference between a reactionless drive and a rocket is that a rocket must carry its own fuel with it, so that it can expel the fuel to generate thrust. The fuel adds additional mass to the whole rocket, so in a way, a rocket requires extra fuel to carry its fuel. Since a reactionless drive does not expel anything, a reactionless drive would not carry any fuel, and therefore could be more efficient by way of lower mass, but it would still need to carry an energy source of some type, such as a nuclear reactor, or a radioisotope thermoelectric generator. Rockets are certainly capable of accelerating a mass to a significant fraction of the speed of light. However it is important to note that it becomes more difficult to accelerate an object as the object gets closer to the speed of light. You need more energy to add a constant amount of velocity as your current velocity increases. This applies regardless of what kind of method you are using to accelerate - doesn't matter if it's a rocket or a reactionless drive. The difference is only in efficiency - it is thought that a reactionless drive might be more efficient. However if a reactionless drive really is possible, it might provide a lot less thrust than you think. So even if reactionless drives are developed, they might be more efficient than rockets, but far less timely. I think you'd be waiting quite a while for the reactionless vehicle to attain any sort of appreciable velocity - perhaps decades. As far as weapons go, humans have not met any aliens yet (to my knowledge) and our species currently only resides on planet Earth, so any weapon would be ballistic in nature, to strike targets on Earth's surface. A reactionless drive would be ill-suited for ballistic propulsion because it doesn't give enough thrust. If it was launched from the ground like an ICBM on a suborbital trajectory, it wouldn't be able to escape Earth's gravity, it would just sit on the launch pad. If it was placed into orbit using a rocket as a first stage, and then activated later, it would take a while to deorbit rather gently. The vehicle's velocity would slow down due to air resistance, and its kinetic energy would not be usable as a mass destructive weapon. This is why large explosions are used as weapons of mass destruction, and not kinetic energy alone. Kinetic energy is simply used for timely delivery of the explosive device from a great distance away. Now, for interstellar warfare, a reactionless drive could be useful if you were extremely angry at another planet in another star system located many light-years away. The large distance between the aggressor and the victim allows the kinetic vehicle a lot of time to accumulate velocity. However the steering of such a kinetic weapon must be very precise in order to hit the target planet, so the vehicle must have the means to estimate its current location/speed/direction, compute the orbits of itself and its target, and apply the necessary course corrections in order to hit that target. It is possible that a reactionless drive might provide vectored thrust, but if it does not, then attitude adjustment thrusters would be needed (either reactionless or conventional.) Accurately steering a vehicle traveling near the speed of light does not seem like an easy task. If the target was missed, the vehicle would be traveling so quickly that it would escape the star system on a hyperbolic escape orbit. Such a weapon would be quite the undertaking and would be a large energy expenditure for a civilization. It might be more worth it to focus that energy into colonization and defense instead.

glomph 12y ago

Speculative articles about technology/science are not philosophy.