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Questions about Nasa's space drive answered

wired.co.uk

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Re: Questions about Nasa's space drive answered

#31

Post by tobinfricke »

madaxe_again wrote: post #16
didgeoridoo wrote: post #2

Deep 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 understand perfectly well how wings work.

What is it with Hacker News and anti-intellectualism?

Re: Questions about Nasa's space drive answered

#32

Post by tobinfricke »

didgeoridoo wrote: post #2

Deep breaths. Probably experimental error. Extraordinary claims require extraordinary proof... God DAMN this is exciting.

I'd say that it's about on par with the faster-than-light neutrinos caper (tiny effect, violates known physics, probably result of experimental error, ...). Both would be very exciting if actually confirmed, but I personally found/find the chances too slim to (yet) get excited.

Re: Questions about Nasa's space drive answered

#33

Post by tobinfricke »

madaxe_again wrote: post #26
ColinWright wrote: post #23

Earlier 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…

No, I've a masters degree in Physics, and did several research projects on turbulent/laminar flow. We have a detailed understanding of a variety of theories which correctly represent the lift effect experienced on a body moving through a flow, yet none of them do it perfectly or completely. We can implement the technology well, but not without the aid of wind-tunnels and brute-force computer simulations in order to v…

Fluid flow is complicated, true - but the basic physical phenomenon of lift is very simple and completely understood: wings redirect air downwards, and the reaction force is what we call lift.

Re: Questions about Nasa's space drive answered

#35

Post by DanBC »

tobinfricke wrote: post #31
madaxe_again wrote: post #16

Earlier quoted context omitted.

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 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 science where we have "useful lies" used to explain things to people, but when you get more in depth things get trickier.

Clifford Stoll uses the question "Why is the sky blue?" as an example. You keep asking "Why?" as a response and see how far someone goes. Most people will say "light scatters"; some might say "Rayleigh scattering".

Of course, there is a difference between "Science knows but the general population hasn't learnt it" and "science doesn't know" but for a surprising amount of stuff science doesn't know, yet.

Re: Questions about Nasa's space drive answered

#36

Post by tobinfricke »

bitL wrote: post #8

So what's the difference between what NASA does, what Chinese did with Em drive and what Russians have orbiting in Yubileiny satellite? More interesting question: can I make one at home? I can do magnetic levitation, both pushing and pulling with high-frequency electromagnets; it would be cool if I could do this as well and having floating objects in my home 8-)

"it would be cool if I could do this as well and having floating objects in my home"

The reported thrust of the device is in the tens of micronewtons. Assuming it weighs 1 kg, you would need approximately a million times more thrust for the device to levitate (i.e. counteract its own weight) at the surface of the earth.

Re: Questions about Nasa's space drive answered

#37

Post by marcosdumay »

madaxe_again wrote: post #26
ColinWright wrote: post #23

Earlier 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…

No, I've a masters degree in Physics, and did several research projects on turbulent/laminar flow. We have a detailed understanding of a variety of theories which correctly represent the lift effect experienced on a body moving through a flow, yet none of them do it perfectly or completely. We can implement the technology well, but not without the aid of wind-tunnels and brute-force computer simulations in order to v…

Well, if brute-force computers simulations correctly represent a wing, then we do know how they work. We may need wind-tunnel tests even if we have a perfectly realistic model, because we may not know if our simulations converge.

Re: Questions about Nasa's space drive answered

#38

Post by lmm »

madaxe_again wrote: post #26
ColinWright wrote: post #23

Earlier 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…

No, I've a masters degree in Physics, and did several research projects on turbulent/laminar flow. We have a detailed understanding of a variety of theories which correctly represent the lift effect experienced on a body moving through a flow, yet none of them do it perfectly or completely. We can implement the technology well, but not without the aid of wind-tunnels and brute-force computer simulations in order to v…

It doesn't imply a deterministic universe any more than vanilla many-worlds. Sure, the pilot wave is deterministic. But when you actually measure the position of the particle? You get one of many possible results, with probability determined by the pilot wave. Big whoop.

We understand QM perfectly well in the only meaningful sense - we can predict the results of any experiment. There's plenty of arguing about "what it means" or "what's really happening", but that's not really physics in my book.

Re: Questions about Nasa's space drive answered

#39

Post by tfgg »

madaxe_again wrote: post #16
didgeoridoo wrote: post #2

Deep 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…

None of the things mentioned so far that we "don't know how they work" are on a par with this. Flying with wings doesn't violate fundamental, and experimentally very well supported, symmetries like conservation of momentum, nor do high temperature superconductors.

Your final sentence is actually nonsense.

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