Tom Mahood worked with Jim Woodward for over ten years on Mach Effect Propulsion. Tom describes his graduate studies work and the Mach Effect and working with Jim Woodward. (H/T Talk Polywell) 'I eventually ended up working with Jim for quite some time, focusing my graduate work on gravitation and Jim becoming my graduate adviser. Before doing so, I discussed it with the Physics department graduate adviser. I asked him flat out, "Do you think Jim is crazy?" He laughed and said, "No, not at all". He said that at the very least I’d get an excellent education in experimental technique. But as we talked, it became clear to me the adviser didn’t exactly know what Jim was doing and hadn’t read any of Jim’s papers.' 'It would probably be a good idea to go over a little of the theory before getting into the guts of what I got myself involved with. It essentially revolves around what is the cause of inertia. Why, when you push on something, does it resist? Toward the end of the 1800s, a physicist by the name of Ernest Mach (of "Mach number" fame) suggested that inertia was caused by the interaction of all the matter in the universe. Einstein later gave this idea the name of "Mach’s Principle". It’s a tantalizing theory, but it’s never been clearly proven. OK, time for a classic thought experiment! Suppose you take a bucket partially filled with water, and start spinning the water in it. As the water spins around the bucket, it rises up the sides due to centrifugal forces. You see the same thing every time you make a Margarita in a blender. Nothing strange there. Now let’s bring Einstein’s Relativity into play. It says that all motion is relative and you get the same results whether you smash two cars together head on at 30 miles per hour as you would if one car was stationary and you hit it with another car at 60 miles per hour. In either case the cars close at 60 mph. Again, nothing strange there, just common sense. But now lets go back to the water spinning in the bucket. According to Relativity (which has yet to be disproved), you would get the same results (i.e., water rising up the sides) if you held the bucket still and spun the universe in circles around it. Whoaaaa! Now that’s pretty weird! If there’s no link between all the matter in the universe and the bucket’s water, how could that happen? The only possible way the rest of the universe, spinning madly around the bucket of water can possibly affect it is through some sort of gravitational interaction. "Spinning water buckets are one thing, but how does some asteroid around Alpha Centuri affect the inertia of my Toyota?," you might be asking. Fair and interesting question. It turns out that every piece of matter in the universe creates its own little bit of a gravitational field. The value of this field at a distance is called the "gravitational potential". Taken by themselves, these little bits and pieces of matter around us don’t amount to a whole lot, gravitationally speaking. Look how much matter you need in one place (i.e., the Earth) before anything interesting happens. And even then by simply jumping you can temporarily break the Earth’s grip. Furthermore, this gravitational potential diminishes with distance, which is why our much larger Sun doesn’t pull us off the surface of the Earth to a toasty doom. The much closer (though smaller) Earth wins the tug-of-war. There is a similar situation with electrical charges worth mentioning. As you may be aware, things can have certain electrical charges. Materials can be positively charged, negatively charged, or have no charge. Things that end up having a positive charge simply have more positively charged "bits" than negatively charged bits. Things that have no charge, or neutral materials, have essentially the same number of positively charged bits as negative bits. The positive charges cancel out the negative charges. And neutral materials make up the vast majority of stuff in our universe, so when we step way back and look at our whole universe, the overall electrical potential is zero. But this isn’t the case with the gravitational potential, because there isn’t "positive gravity" or "negative gravity" to cancel out each other. There’s just one flavor of gravity and it adds and adds and adds and ….. Well, you get the picture. If every piece of matter in the universe is generating its own little bit of gravitational potential, pretty soon you end up with a huge amount of this gravitational potential everywhere. But why don’t we feel any of this gravitational potential if it’s so great? Well, we do and we don’t. In a sense, it’s like living in a highly pressurized underwater habitat. Even though the occupants of the habitat might be under tremendous pressure, they don’t really notice it because they experience the same pressure everywhere around them, even inside them. It’s the same with gravitational potential. Even though it may have a very large value, as long as it’s pretty much equal everywhere, we don’t notice anything out of the ordinary. When we notice gravitational effects (e.g., falling down the stairs), what we’re actually noticing are differences in the gravitational potential (the "gradient" in nerd-speak). In the case of falling down the stairs, it’s the nearby Earth causing a gradient in the gravitational potential. But when it’s the same potential everywhere, you don’t feel it. But I also said we do feel it. We "feel" it every time we push on something, and that something pushes back. It’s the interaction of this universal gravitational potential with matter that causes inertia! The gravitational potential sort of "oozes" through all matter (because you can’t shield gravity) and gives it that resistance to being shoved around we call inertia. After a lot of years of work, Jim had found a quirky mathematical derivation that suggested by rapidly changing the energy density of an object in a certain way, it might be possible to briefly alter its mass. In most cases, it would time average to zero, in that briefly the mass would increase, then decrease, and it would always just cancel itself out. But it appeared possible, mathematically at least, that one could fool Mother Nature and extract a net force or thrust on the object changing mass by pushing or pulling it at just the right times.' 'If you just set the fruitcake on the table, not much happens. Now some might argue it’s just the nature of fruitcakes, but there’s more to it than just that. Sitting there, motionless, you could say that the fruitcake is "in sync" with the gravitational potential of the rest of the universe. In a loose sense, it is. You would also find this true if you gave it some constant velocity (and some may argue that giving fruitcakes velocity, preferably out a window, is a worthwhile thing). So, just sitting there or moving at a constant speed, what you have is just your plain, ordinary fruitcake. Nothing special going on, unless you have a fruitcake fetish. But let’s look at the case where we accelerate the fruitcake (i.e., you change its speed). Actually, the most interesting effects happen from time-varying acceleration, but we’ll just examine the simplest case. So let’s give our fruitcake a very, VERY rapid burst of acceleration and see what transpires. Skipping all the scary math, what happens is the fruitcake kind of gets "out of sync" with the gravitational potential it’s immersed in. That’s because the gravitational effects from all the stuff in the universe can only spread out at the speed of light and can’t react to our rapidly twitching fruitcake. It’s not like it’s exactly outrunning it, but that’s an image you can hold in your mind if you’d like. What you’re actually doing is inducing a varying change in the fruitcake’s position so quickly that the nice gravitational balance with everything else in the universe gets sort of temporarily mucked up. And since the inertia of the fruitcake is caused by this gravitational potential, if you can make the acceleration really, really large, the "muckiness" gets really, really large, and the fruitcake’s mass slightly decreases for the brief instant of this large acceleration. Now we’ll stop accelerating the fruitcake and let it just coast along for a bit at whatever constant speed it happens to be at. We now find its mass has returned to normal (ignoring any mass increase due simply to relativistic speeds). Finally, we’ll bring our high-speed fruitcake back to a stop via a huge deceleration equal to our initial huge acceleration. We note that the mass of the fruitcake gets slightly heavier during this deceleration, then returns to normal as the fruitcake plops to a stop. Overall, during the whole speed up – slow down cycle the unfortunate but well-traveled fruitcake goes through, the mass change averages exactly to zero, and you end up with the same mass of the fruitcake as if it were sitting still, so it’s pretty hard to notice unless you carefully look for it. But how does this take place? OK, time for an analogy of how this works. It’s not a great analogy, but it’s good enough. Picture yourself outside in an absolutely torrential rainstorm, holding a sponge. Happens all the time, doesn’t it? Now think of the rain as the gravitational potential, and it almost instantly fills your sponge to bulging with a pound of water. The now drowned sponge can’t hold any more water than a pound, so the excess just bounces off or flows through it. Now start walking at a constant speed. A little water squeezes out as you first start off, but essentially the sponge stays fully saturated, and still weighs a pound. Now quit walking and start to move the sponge from side to side, slowly at first, but then faster and faster. What you’re doing is accelerating and decelerating the sponge. You’ll see that when you push on the sponge, it tends to squeeze or compress a little smaller and water squirts out, making the sponge a little lighter. Then when you pull back on the sponge, it elongates a bit and fills up with a little more of the "gravitational rain" and gets a little heavier. By doing this fast enough you can make large, but very temporary changes in the apparent weight of the sponge. Finally, when you get tired of slinging the sponge back and forth, and let it come to a rest, the gravitational rain fills it back to its normal pound. It should be noted that this extremely simple analogy makes use of plain, ordinary accelerations. Significant mass shifts require the use of varying acceleration. It turns out this effect, while odd and interesting, is not terribly useful in itself. To get any really large mass shift, the amount of acceleration required is too huge to be practical. If you tried it with Aunt Edna’s fruitcake, it would end up as fruitcake goo, a thought even more unpleasant than the fruitcake itself. So how the heck can you subject matter to large accelerations without pulverizing it?' 'Time for a little technical detour into the world of capacitors. A capacitor is just a bunch of metallic plates, separated by a small distance, holding a bit of electric charge. While a capacitor can hold a charge without anything between the plates, it turns out that placing an insulating material called a "dielectric" between the plates allows it to hold a great deal more charge. This dielectric has sort of a crystalline structure with the atoms arranged in neat, somewhat cubic cells. When the plates of the capacitor become charged, these atoms actually move a bit, like little weights on tiny springs, in response to the electric field. So when you charge and discharge the capacitor, you are actually moving some of the atoms in the dielectric back and forth very, very quickly. So via this method, the fruitcake, uh I mean accelerated mass, can be replaced by a rapidly charging and discharging capacitor. The faster it charges and discharges, the more "acceleration" the capacitor’s dielectric atomic bits are subjected to and the larger the mass shift. A significant problem with identifying this effect is how do you weigh something that’s changing its weigh by a small percent many thousands of times a second, and just averages out to a zero weight change over a very small time? It turns out to be possible by giving the object rapid pushes against a very sensitive scale just as it gets lighter, and comparing those measurements to the weight when the cycle is exactly the opposite. How that’s done in itself is somewhat interesting, but a variation of it can be exploited (remember that choice of words?) to produce thrust.' 'You can actually get useful thrust using this effect when you sandwich the capacitor between two piezoelectric crystals. Piezoelectric crystals (piezos, for short) are a neat type of material that rapidly expands or contracts a small amount when subjected to a voltage and happens to be very similar to capacitor dielectric material. Most everyone’s been exposed to them without being aware of it. Piezos are used in push button igniters for barbecues and other gas appliances (even cigarette lighters), in which case they work in reverse. By giving the piezo a swift whack with a spring-loaded plunger, the piezo generates a several thousand volt spark. Zap! What we’ve done in the lab is taken discs made of piezo material, and placed them on each side of some capacitors. They’re wired up to a voltage source that’s changing around 28 thousand times a second, with one piezo wired in reverse of the other. This means that as one expands, the other contracts, and the capacitor sitting in between getting shuttled back and forth. The charging and discharging of the capacitor is synchronized with the motion of the piezos, so that the capacitor gets thrown one way as it gets slightly lighter, and then slammed back the other way as it gets slightly heavier. To illustrate how that produces thrust, let’s drag out another analogy. Picture yourself standing on a skateboard with a 10 pound brick attached to you via a bungee cord. If you throw the brick away from you, you and the skateboard will move in one direction and the brick will head in the opposite direction. Eventually the bungee cord will stretch to its limit, and you and the brick will stop, then come careening back together. If you note exactly where you and the brick smash back together (ouch!), you’ll find it’s exactly where you began. There was no net motion; it all balanced out. You didn’t get anywhere and you got smacked by a brick, to boot. Now let’s say you replace your old fashioned brick with a new, high tech brick from Mach Industries. This is one great brick! As you hold it in your hand, it weighs 10 pounds. But then as you throw the brick away from you, its inertial mass drops to 5 pounds! When it stretches the full extension of the bungee cord, its mass has increased to 15 pounds. Finally, as the brick smashes back into you (sorry, we can’t fix everything!), it’s now back to 5 pounds. After you recover consciousness, you discover to your amazement you’ve moved some distance in the direction you first tossed the brick away from you. In this case, the forces don’t balance out and there is net motion in one direction. That’s pretty much how we get thrust using capacitors and piezos. The capacitor is the brick, and the piezos are bungee cords. By doing it over and over many thousands of times a second, a net force (or thrust) can be produced.' 'It seems to be. The theory that says it should occur is pretty straightforward and is derived fairly simply from Special Relativity. When viewed in its entirety, it fits in with all other laws of physics. There’s no new, strange physics required. In fact, some of the components are in published scientific papers going back to the 1940’s and 50’s. It’s been demonstrated in the lab in a number of different devices, and they all are fairly consistent. When subjected to rigorous checking, the effect is present when it should be and goes away when it’s not supposed to be there. While this is very encouraging, the effect is still quite small, and the possibility does exist that this is all some bizarre quirk of the experimental setup. At the present, the possibility of it being a quirk appears fairly small and it looks to be the real deal. It has not, as of yet, been definitely replicated by other experimenters. An experimenter named Robert L. Talley, doing research for the government in 1990, appears to have stumbled across evidence of this effect, but did not recognize it for what it could be, and didn’t pursue it to any large degree. There have also been a few "informal" attempts at replication, with null results. This isn’t surprising, as it turns out there are a host of subtleties and complications that make it a difficult experiment to do properly. If the necessary precautions and safeguards are not taken, a null result is almost guaranteed. Better understanding of the effect and its workings has grown to the point where it’s now possible to actually make a device visually move on a pendulum arrangement. This has been done with several test devices in two very differently designed pendulum setups. Both of these have produced consistent, positive results.' '“Wait just a stinkin’ minute!” some of you are hollering by now. "This is bullshit that violates both conservation of momentum and energy!" And so it would appear, at least superficially. But there’s a way out of the weeds and it has to do with Mach’s Principle. If it’s true that the inertia (and thus the mass) of an object is created by the action of all the other matter in the universe, then something strange is going on. When you push on something it "pushes back" instantly. How could the rest of the universe respond instantaneously? Aren’t things limited by the speed of light? Not necessarily. There is something called "Absorber Theory" developed by John Wheeler and Richard Feynman in the 1940s which deals with certain odd effects of electromagnetic waves. In a Machian interpretation of Absorber Theory, pushing an object sends off incredibly minuscule gravitational waves at the speed of light, essentially into the future. As they eventually interact with everything else in the universe, those interactions sent equal gravitational waves back in time, to the object the instant you push against it. Bingo, bango, everything cancels and the object has inertia. Now I know how wacky that might seem, but it’s theoretically sound. And Jim appeared to have found a mathematical way around the cancellation. When the equation is fully derived, several strange terms appear in the equation (The final equation is shown below, but for a full derivation and understanding of the variables, see [Tom Mahood’s thesis].' [Equation referenced: Final derived equation showing the impulse and wormhole terms]