Many other people, inspired by Star Trek to take up careers in STEM fields, adjust their expectations accordingly without losing their sense of wonder or willingness to push at the limits of knowledge. This guy is a bit too old to claim inspiration from Trek, though, as he’d have probably already been working on his doctorate when the original series was on.
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It’s not pedagogical process that sucks enthusiasm out. It’s the realization about how hard it actually is to make any meaningful contribution to major open questions in science. I am speaking from my personal experience. (I dropped “out” only after three years of post-doc).
Also, he would not be able to do any of this stuff without his training in theoretical physics.
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I found this to be a disappointingly poorly thought out article. A healthy dose of skepticism is always warranted when dealing with new unexplained phenomenon – because, for the most part, these turn out to explained not by new hitherto fore unknown science but by experimental error, measurement bias or outright fraud. There are far more cases of that happening than revolutionary results. The total lack of skepticism in this article does nothing to promote scientific literacy - it’s just another case of “ooh, we hope the underdog wins against the big bad establishment.”
I understand that a journalist isn’t expected to have the physics background to question the theory or experimental setup. But how about asking someone who does and including their response? What about mentioning the countless cases of “new results” that turned out to be bad measurement or fraud. For example, anti-gravity (published in PRL, no less), or N-rays.
And as a last comment, even a lay understanding of physics suggests that his proposal wouldn’t work for propulsion, because the charge on the capacitor moves elsewhere in the system and increases the mass there during the time the block is “lighter.”. So that overall, the complete system would not have any change in momentum. How can the author ignore countless results and theory verifying conservation of momentum for a guy whose best argument for his theory is that no one has disputed it?
Bad journalism.
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Exactly. Whatever you may say about the flaws in our system of academic science (and there are many), many of the very parts of the pedagogical system that induce people to drop out are essential to actually understanding science.
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You can’t satisfy conservation by slipping back and forth between reference frames like that, or you would never have any case that violates them. In the frame of the planet, the ship is accelerating toward it and the planet is still; in the the frame of the ship it’s the opposite. Neither satisfies conservation.
That said, you wouldn’t expect Woodward to have gotten even this far without considering momentum at all. His claim is that “local momentum conservation is preserved by the flux of momentum in the gravity field that is chiefly exchanged with the distant matter in the universe.” That’s not something that is inherently impossible; it would be akin to propulsion by firing off gravity waves, which are predicted by general relativity though detecting them has proven difficult.
Incidentally, propulsion by firing off gravity waves sounds absolutely dreadful. Momentum and energy aren’t entirely well-defined for them, but to the extent that they are I would think they follow the same E=pc relationship as electromagnetic radiation. That’s something we understand well; emitting a strong enough beam of light will slightly accelerate a ship. It’s…not actually saving on fuel to do that.
I take it this is hoped to be more efficient, but can’t imagine why. At any rate I think it’s silly to get too excited about spaceship applications until there’s some decently established physics anyway. Here the interesting idea is to do with Mach’s conjecture, which can be formulated in different ways that run the full spectrum from well-established to discredited.
As for this particular version, though, I would say mass fluctuations have not been looking good. It’s nice to see them tested, but Woodward seems to have found support only in very ambiguous situations, and other groups much less so. So I’m with Stumpy on this one; it doesn’t seem like our universe works that way.
I wrote the article. First, I think it contained quite a lot of skepticism. At no point did I state categorically that anything worked, and I left the door open to the possibility that it doesn’t work. I simply reported what I saw, and suggested a couple of thought experiments. Words such as “if” and “might” were used.
Second, we are plagued with journalism where the writer is compelled by the editor to write a “balanced piece” citing “opposing viewpoints.” Usually this means that the journalist calls someone who can be guaranteed to say “No, it won’t work.” The source will not have in-depth prior knowledge of the specific phenomenon. The opinion of the source really doesn’t mean anything. This ritual just creates the illusion of balance.
Third, I think your idea that the “charge on the capacitor” moving “elsewhere” and increasing “the mass there” is simply wrong.
Last, I knew I could count on BoingBoing readers for the missing ingredient of skepticism!
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No, not at all. The minor satisfaction of being right and the recognition of seeing the document change is enough. If that could happen in the background without annoying those who don’t care, it would be fine.
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His formal training in physics seems to be more limited than that of most professional physicists. It may or may not have been a very significant factor in his case, but there’s a broader point I’m addressing.
I’m speaking from beyond my personal experience. The statistics show that programs that more carefully engage students are more successful and have lower drop-rates. This is about engineering, but the pure sciences also suffer from the same problems. Hard has nothing to do with it. “Hard” is an easy problem to fix, and it takes for granted the fact that other disciplines are also difficult to master. Ever try writing a novel? In fact, there’s a certain denigration of the difficulties inherent to other disciplines by people in the sciences in large part because they haven’t spent enough time at the higher levels of those fields to understand that it can be just as hard, because unlike the sciences, most other fields start out fairly elementary, based on the pragmatic understanding that skills are built with time, and that they do not necessarily need to be buried in years of pointless grunt work before you even get to design a real experiment (i.e. apply those skills meaningfully.)
Not that I’m against building skills, and there’s an element to that in the sciences that will never go away, but the emphasis on theoretical problem-sets is enough to kill a lot of otherwise capable people’s passion. I’m sorry, but if you’re an aspiring physicist, Atwood machines aren’t that goddamn interesting, especially if you never build any. It doesn’t matter that macrophysical potential energy considerations are critical for doing cutting edge work, students can’t see those particular trees from the forest of what appears to be insignificance. Students come from a place of ignorance, and that ignorance needs to be engaged in a meaningful way. Students are not in a position to understand why what they’re learning is so important. They are merely told from on high that This Is How You Must Learn This. There are people who can look at puzzles on paper and love them simply because they’re puzzles. Good for them, but that’s not how everyone engages the world, or even how everyone solves puzzles.
Hard isn’t why I dropped out. Hard doesn’t bother me now that I’ve dropped back in. I love problems, and difficulty, and work. What I don’t love? The rapidity with which I’m supposed to acquire deep knowledge, and the incentives to spend as little time as possible understanding new concepts. I’ve had lab classes where I can get great grades and learn extremely little. In fact, the best grades come from finishing procedures as quickly as possible, plugging and then chugging. I’m not exactly going to ITT Tech either, I’m going to a highly rated public institution that is by all metrics much better than the institution I attended my first go-around. The deficiencies there mirror the ones I’m encountering here. I’m doing a hell of a lot better though. Why? Because I learned something extremely important: Even the most fascinating material is going to be rendered uninspiring by your instructors.
Actually, this isn’t the absolute rule, but things get a lot easier when this is your default assumption. Fortunately, I’m an adept autodidact, and it’s incredibly sad that I feel like my success comes from that.
There are reasons it’s been called the Math-Science Death March, for some reason though, it gets defended as separating the wheat from the chaff. Yet, that’s not the function it ultimately serves. It separates a small sampling of what could be a more diverse field, from every other kind of scientist that could be contributing to the field. It’s not even as if I believe we need more scientists and engineers, I never bought into that fallacy. I do, however, strongly believe we need more kinds of scientists and engineers.
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This may be nitpicking, but the article seems to use “weight” and “mass” interchangeably. In any other article this would be perfectly excusable, but not here.
I wish (very egotistical of me) to offer an alternative method.
Let us say that what James Woodward has is a box that can become heavier or lighter at command.
Now visualize
a large cylinder floating in space, if we place the box at the inner “forward” end the cylinder and give it a strong push (with a spring to simplify).
The cylinder will accelerate “forward” while the box travels to the rear of the cylinder, the moment the box collides with the inner rear wall of the cylinder, the cylinder comes to a stop because the force now excreted in the backwards hull will be equal to the force that was exerted forward.
This is because the FORCE = MASS of the box X VELOCITY of the box.
BUT, if we really can make the box lighter (less mass) at command then the resulting force in the backward direction will be less and the cylinder will gain velocity every cycle.
And there is another way.
If instead of reducing the boxes mass we reduce its velocity, by the same equation (F=MxV), the resulting force in the backwards direction will also be diminished.
The big difference is that while modifying a box’s mass is complex, modifying its velocity is a simple matter, all we need is an air brake or parachute if you will (did I mention that the cylinder is pressurized).
There is an article by David Hambling that explains it more clearly here: http://www.wjetech.cl/law.htm
And a short video here: http://youtu.be/RAuXJ95Dtkc
In short I believe (know) that the effect of propulsion can be better archived by modifying the box´s velocity instead of the box’s mass (unless box’s mass can be modified by a large margin (3% or more) in which case we will remember James Woodward for a lot more than just propulsion.
Assuming you did have some engine that could move by firing off gravity waves, what exactly would this mean? Somehow when these waves hit something they would have to exert an opposite force on anything they hit, so it would be effectively pulling on objects in front of it and pushing on objects behind it? It’s somehow disturbing the vacuum could transmit momentum this way, is that really how GR works?
That’s an idea; using a reactor to power lasers and use the photons as a reaction mass.
…wouldn’t it be more efficient, though, to use the fission fragments from the reactor, though? They have quite high energy…
Yeah, people have been theorizing about photon rockets for a while. The problem with them is it takes 300 Megawatts to get just 1 newton of thrust. On the bright side, though, since your engine is literally a high-powered laser, it would also make one hell of a weapon. As I recall, one of Niven’s stories invovling the Kziniti had a techncially-unarmed ship doing that, cutting a pursuing Kzinti ship in half by just wiggling the ship so the beam from the photon rocket brushed across it.
You’re right, though, fission-fragment rockets would probably be a much more efficient use of your reactor, unless you’re willing to have the photon drive be a stationary self-powered unit, and the craft just be a reflector and the payload.
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This changes everything.
…here goes the plan for tonight…
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If you want a slightly more fun approach to the same kind of topics, check this site out. It’s a resource for writers who want to know how to write more realistic space travel stories.
More or less. The easier way to think of it is that there is energy and momentum associated with the gravitational field itself, just like there is with the electromagnetic field. Light is basically energy and momentum carried through a vacuum by EM fluctuations; a gravity wave would be equivalent.
It’s not fully equivalent because the gravitational field is a curvature tensor and it becomes hard to define conserved quantities in a way that makes sense. But as a general principle, for instance, people do talk about “gravitational radiation recoil” when black holes merge. In less extreme cases it’s just too weak to worry about.
I would say so! That was more or less my point: we know a way to make a reactionless thruster, it’s just that as Drew_G says it’s horribly inefficient. I don’t see why one based on gravity rather than electromagnetic waves should be any better.
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It’s not really a reactionless thruster, though. The reaction is just radiation pressure by emission instead of the equal and opposite force created by throwing things out the back of your rocket as fast as you can.
I’m an electrical engineer, and I don’t understand what he is doing to modify the mass of the moving lump. There is mention of charging a capacitor, which will change its mass. Presumably, this is due to the electrons moving into or out of the plates of the capacitor.
My understanding of the internal workings of a capacitor is that its charge is modified by putting more electrons into one terminal while extracting the same number of electrons from the other terminal. Thus, the mass does not change; the electrons just move the tiniest distance (the plates in a ceramic capacitor are on the order of nanometers thick).
What am I missing?
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Doesn’t work at all. David even acknowledges the problem, that it fails for the same reason that a flying bird in a sealed cage doesn’t make it lighter - only he then holds out the hope that it actually might. Well, if for some reason very straightforward physics telling you that can’t work wasn’t enough, MythBusters actually tested it.
You can’t violate conservation of momentum using interactions that conserve it. Also, just for the record, force isn’t really mass times velocity, though I understand you’re really talking about impulse.
Sorry, I meant reactionless only in the sense of not throwing out matter. I assume that’s how it’s meant here; if you believe in conservation of momentum, a thruster always needs something carrying that away. Massless fields work but have the serious drawback that you need at least E = pc.
All that’s being done is making it absorb energy and accelerate at the same time. The hypothesis is that this causes a change in mass, as unconfirmed physical principle based on an interpretation of Mach’s conjecture. So far there doesn’t seem to be evidence that this actually works, though Woodward has been trying to show it does.
