It's probably powered by N-rays.
Questions about Nasa's space drive answered
81–90 of 205 posts
Re: Questions about Nasa's space drive answered
#82Earlier quoted context omitted.
> ... we still can't make up our > minds as to how wings work, ... Interestingly, I recently spoke to an aerodynamicist and mentioned this, and I was severely lectured. In the follow-up he mellowed a little, but I suspect the "we" in your statement refers to laypersons who don't have advanced training in aeronautics, and yet claim to understand about flow pressure, Bernoulli, etc. I've been convinced that the people…
Does Feynman's "if you can't explain it to a laymen in a few paragraphs then you don't truly understand it" no longer hold?
I also generally subscribe to the idea that, if you can't adequately explain something to someone unfamiliar with the idea, then you don't properly understand it yourself. But my inability to explain something to someone says nothing about whether the phenomenon "is understood" in the more general sense.
Re: Questions about Nasa's space drive answered
#83I've read the abstract, but apparently Wired has access to more information. Any idea where the primary source for that information is?
I'm interested to see what magnetic shielding was used and how well they characterized the magnetic field in the experimental volume. There was a mention of shielding against electromagnetic effects, but that could just mean a Faraday cage or Helmholtz coils, neither of which will reduce the B-field to zero.
Because the device is based upon microwaves in a conducting cavity, I would think that the first place to look for a theory of operation would be E&M, not quantum. The level of force involved is the kind that you can see when interacting with the Earth's magnetic field. Normally we ignore the force produced by the interaction of currents with the Earth's field, because they are so small. Was a mu-metal shield used, and if so, what was the remnant field? Was a stronger field induced to see if that increased the force? I hope that the experimenters try this if they have not already.
Re: Questions about Nasa's space drive answered
#84Deep breaths. Probably experimental error. Extraordinary claims require extraordinary proof... God DAMN this is exciting.
Indeed. As to the whole "we don't actually understand how it works" - we still can't make up our minds as to how wings work, so this isn't overly novel. Sure, we can explain the outcome, but whether it's Navier-Stokes or Bernoulli or something else, we can't make up our minds. I suspect this will be similar for a long while - although puts physics hat on I think this is likely a relativistic temporal quantisation eff…
"We still can't make up our minds as to how wings work, so this isn't overly novel. Sure, we can explain the outcome, but whether it's Navier-Stokes or Bernoulli or something else, we can't make up our minds."
Time to trot out my favorite quote about how airplanes fly, from Stick and Rudder by Wolfgang Langewiesche, page 9, published 1944:
»The main fact of all heavier-than-air flight is this: the wing keeps the airplane up by pushing the air down.
It shoves the air down with its bottom surface, and it pulls the air down with its top surface; the latter action is the more important. But the really important thing to understand is that the wing, in whatever fashion, makes the air go down. In exerting a downward force upon the air, the wing receives an upward counterforce--by the same principle, known as Newton's law of action and reaction, which makes a gun recoil as it shoves the bullet out forward; and which makes the nozzle of a fire hose press backward heavily against the fireman as it shoots out a stream of water forward. Air is heavy; sea-level air weights about 2 pounds per cubic yard; thus, as your wings give a downward push to a cubic yard after cubic yard of that heavy stuff, they get upward reactions that are equally hefty.
That's what keeps an airplane up. Newton's law says that, if the wing pushes the air down, the air must push the wing up. It also puts the same thing the other way 'round: if the wing is to hold the airplane up in the fluid, ever-yielding air, it can do so only by pushing the air down. All the fancy physics of Bernoulli's Theorem, all the highbrow math of the circulation theory, all the diagrams showing the airflow on a wing--all that is only an elaboration and more detailed description of just how Newton's law fulfills itself--for instance, the rather interesting but (for the pilot) really quite useless observation that the wing does most of its downwashing work by suction, with its top surface. ...
Thus, if you will forget some of this excessive erudition, a wing becomes much easier to understand; it is in the last analysis nothing but an air deflector. It is an inclined plane, cleverly curved, to be sure, and elaborately streamlined, but still essentially an inclined plane. That's, after all, why that whole fascinating contraption of ours is called an air-plane.«
Re: Questions about Nasa's space drive answered
#85Earlier quoted context omitted.
> ... we still can't make up our > minds as to how wings work, ... Interestingly, I recently spoke to an aerodynamicist and mentioned this, and I was severely lectured. In the follow-up he mellowed a little, but I suspect the "we" in your statement refers to laypersons who don't have advanced training in aeronautics, and yet claim to understand about flow pressure, Bernoulli, etc. I've been convinced that the people…
Does Feynman's "if you can't explain it to a laymen in a few paragraphs then you don't truly understand it" no longer hold?
I have never heard the quote with the middle section you included "to a laymen in a few paragraphs"
I have frequently heard the quote without that section, that section seems flawed in that a layman would need to have all the underlying concepts explained to them also, indicating that application of the quote would not scale, as more underlying concepts were necessary to include.
Re: Questions about Nasa's space drive answered
#86Earlier quoted context omitted.
As the article points out in 8., there have been previous, independent experiences that support the results.
Just because something is able to be replicated multiple times, by different people, you still don't want to jump to conclusions. You just need to look back at polywater, http://www.slate.com/articles/health_and_science/science/201...
And several other effects, like N-rays, filed by some under the category of "pathological science" (http://en.wikipedia.org/wiki/Pathological_science).
There's also that nice graph of measurements of the speed of light versus time, in which experiments tended to reproduce the results of (erroneous) previous measurements, due to confirmation bias.
Re: Questions about Nasa's space drive answered
#87Short version: Unless they believe the machine breaks some of the fundamental physics laws, the device must emit something. With this definition using a red LED Laser powered by a 1.5V battery in the back of the spacecraft is a "no reaction mass" thruster. The problem is that the momentum / energy ratio has theoretical limitations, and they are getting too much momentum. Long version (based on a previous comment http…
While it's true that most reactionless drives break some of the most basic physical laws, that's not the case for all of them. An Alcubierre drive is a good example of a propulsion method that works within the current laws, yet does not emit anything.
The idea that the designs they tested (and EmDrive) would be reactionless is exactly why everybody is so baffled and excited by this. If they are, they must have some way to maintain those basic laws, through a process we don't know about yet. Aside from the practical uses, it could lead to a whole new physics to study.
Re: Questions about Nasa's space drive answered
#88Earlier quoted context omitted.
We understand perfectly well how wings work. What is it with Hacker News and anti-intellectualism?
For various values of "we". http://www.grc.nasa.gov/WWW/K-12/airplane/lift1.html > There are many explanations for the generation of lift found in encyclopedias, in basic physics textbooks, and on Web sites. Unfortunately, many of the explanations are misleading and incorrect. Theories on the generation of lift have become a source of great controversy and a topic for heated arguments. There are lots of bits of scien…
One can go further still and differentiate between "science has a reasonably accurate model" and "science has a standard way of describing and characterizing an effect."
Re: Questions about Nasa's space drive answered
#89Earlier quoted context omitted.
These were other, earlier experiments, which the current experiment is attempting to duplicate. Importantly, while the new experiment has superficially "confirmed" the previous ones, it shows a much smaller effect. When the magnitude of the observed effect scales roughly with the margin of error of the experiment, one has very good reason to be skeptical ...
they found 91 mmN of thrust and they claim their detector is sensitive to about 10mmN. that's almost an order of magnitude. this doesn't mean that it sounds too good to be true. edit: fixed units - dont have easy access to micro, thanks for pointing that out.
"u" is an acceptable replacement for "µ". I've never seen "milimili" (mm) before.
You can spell it out, like "91 micronewtons".
You can also use exponential notation like 91e-6 N or 91x10^(-6) N.
To be fancy you can copy-and-paste unicode characters and write 91×10⁻⁶ N.
Re: Questions about Nasa's space drive answered
#90Why does number 7 say a superconducting version of this drive does not require energy to hold things up? Are they just referring to how superconductors can float in an external magnetic field? That doesn't seem to give general purpose hover boards.
I don't know but wouldn't be awesome if we could finally create a hoverboard? :)