J.C.MacSwell

Let's be blunt. The problem is not really speculation in the true sense.

 

Theoretical research, by its very nature is speculation, informed and responsible speculation. String theory, quantum loop gravity, and Lisi's E8 theory are all speculative. They ae also legitimate research avenues. Without speculation there would be no research, and no progress.

 

What is objectionable are the "relativity is wrong because it violates my intuition", "I don't understand quantum mechanics so it must be wrong" or "Faraday's law is wrong" diatribes which have zero basis in either theory or empirical data. In short "speculative' is being used as a euphemism for "wacko". Everybody understands this, even wackos. Uinderstandably, wackos do not like to be clearly identified. Gee, that's unfortunate.

 

The policy of limiting objectionable theories to the "Speculations" forum is appropriate and necessary. What is important is not what happens in "Speculations", but what, as a result, does not happen elsewhere.

I hope that you and other mods keep up the good work.

All that said, there have been a few interesting threads in Speculations. There are also probably a few that could be good but unfortunately get overlooked due to the junk that gets deposited there and overall it is certainly worthwhile rather than just throw it all out entirely.

But relative to the high-gravity situation she is ascending from, the low-gravity observer's time is literally decelerating relative to those she observes below her. So what is it about lower-gravity that allows her time to elapse slower? It doesn't have to do with the speed of energy at the atomic level or something like that?

Higher gravity, or equivalently greater acceleration. With lower gravity or less acceleration time elapses faster.

Think of a light clock just outside the event horizon of a black hole positioned so that the light bounces radially. Obviously the "up tick" will ensure that this clock runs very slowly compared to a similar one at a safe distance. where gravity is stronger (or acceleration is greater) time runs slower.

We will see the same red shift for all clusters of galaxies that are at the same distance from us. But the farther away these superclusters are, the more red shifted they are. No problem at all with that.

 

Most folks around here will say the universe has no center, according to the balloon analogy. But the analogy requires a leap of imagination into the realm of spatial dimensions. That is what bothers me about it. I liked to think of the universe expanding from a single point in a roughly spherical shell, and that shell is hundreds of Billions of light years thick.

That would assume preferred directions in space, with redshift visible in two dimensions but not in the third, thickness, direction. Where is the evidence of that?

You must be right.

So you say that the other forces stay the way they are? under time reversal.

Not absolutely sure about the weak interaction as I know (am aware of) there is a symmetry violation with it, but I think it would have to be as well, assuming time run backwards would get you back to an earlier starting point. (quantum uncertainty aside)

http://www.lbl.gov/abc/wallchart/chapters/05/2.html (Interesting Feynman quote about meeting an Alien)

But in classical mechanics all forces stay the same.

Yeap. That makes it difficult for the glass that fall out the table to jump back in place under time reversal.

It does under time reversal.

Dissipated energy converges, glass fragments combine into a glass with the combined kinetic energy to leap, still against the force of gravity, to land on the table.

If Gravity was repulsive under time reversal the glass (and table) would be heading for the moon, and if other attractive forces were reversed everything would blow apart.

I had a discussion here some time ago. That was about the effects of turning time backward on gravity. Although the "turning time backward" is a very speculative situation, it appeared from the conversation that gravity does not depend on the arrow of time, IOW that gravity remains attractive under time reversal. That would mean that time reversal does not turn everything inside-out.

I don't know about entropy.

Even in Newtonian mechanics the forces remain the same and do not reverse with time reversal. Attractive forces remain attractive, and repulsive forces remain repulsive.

I joined yesterday -.-

Sorry. Bad joke.... 28 billion is twice 14 billion which is roughly the time from the apparent Big Bang. If your assumption is correct about expansion and entropy increasing being linked, then we could very well be in a contraction stage but not know it as our brains would be in reverse.

That's right. And another opinion of mine is that bigger volume equals bigger entropy - entropy is a statistical law, not an absolute like 1st law of thermodynamics. It is based on huge number of cases of lesser order compared to a single case of higher order. More volume must, IMO, imply more cases of lesser order and that means higher entropy. So if at Bang time space had V₀ and at the point of shrinking _Vmaxit's entropy could be also S₀ and S_max . When it starts collapsing the entropy and volume go from V_max and S_max to V₀ and S₀.

So the whole process could be represented like this: V₀(S₀) --------> V_max(S_max) --------> V₀(S₀)

Maybe I'm wrong but anyways I'm open to critics and new ideas and I'm looking forward to your reply.

Sorry if my English sometimes can't keep up with my thoughts

Didn't we have this discussion 28 billion years ago, except this time we are having it forwards?...or is it backward this time?

It is conserved, And some interactions aren't possible because of this; this gives rise to "selection rules" which tell you what transitions are possible. Since the photon has spin 1, the angular momentum of the atom changes by 1. (a combination of spin and orbital terms)

Thanks... the angular momentum referred to is quantized and also non-classical, correct?

In String theory it would be assumed to be in extra dimensions? Any room for the photon to be hiding in there? (I know the last answer is no, because that is not what we call a photon...but all the little quantized bits and pieces seem to be conserved)

The photon doesn't exist as a stored entity. It doesn't exist after it's been absorbed, and new ones are created when the system releases energy via EM radiation.

So the photon's energy and momentum is absorbed...what happens to it's spin??...is this absorbed as well?...I'm thinking this should be conserved as well...somehow...

This is for science fiction I'm working on. Basically I have a spaceship that transports detachable cargo boxes (which would weigh like 10,000 pounds or so). In deep space the box detaches and one of the crew members goes out on a tether and grabs it. The ship keeps moving and he holds onto the box dragging it through space.

 

Ok so I figure that much is definitely possible, but what if the ship slows and the box keeps drifting towards it. Would he be able stop what little forward momentum the box had by putting himself between it and the ship without being smashed? Would he be able to push the box around a little if he was sort of using the more massive ship as grounding?

Well... I've certainly managed to fend off a 5 ton boat (and much larger in calm conditions), moving at slow speed, from a dock or wharf...

It's all a matter of how hard you push, for how long, and how fast it is moving/converging. a=F/m

Interesting. It tempts me to speculate about ancient Martians using the moon as an interstellar vehicle but I shouldn't indulge my fantasies.

Well, if they're not there now and neither is the former moon, what else can one conclude??

Yes. You would be limited to ~6000 K.

Hardly makes it worth while.

Can virtual photons be described, as having positive momentum (by which "(EM) forces" are exerted), but imaginary rest-mass-energy (being "off-mass-shell"), so that their total energy (& energy density, of the associated virtual photon "cloud" shadowing quantum particles) is zero: E² = E₀² + (pc)² = 0 ?

 

Imaginary rest-mass-energy, would translate into imaginary frequency (E = hf), which would make virtual photons fizzle away, exponentially, in time (e^ift --> e^-ft), explaining why they never venture far from the particles producing them. (This might mean, that the lowest frequency virtual photons, would last the longest, and have the "longest reach" (??).)

from above:

"explaining why they never venture far from the particles producing them"

Doesn't that imply a distance limit to the Coulomb forces?

And if they fizzle away exponentially in time, why is it an inverse square law?

Why are there so many "I've discovered the theory of everything, but it blatantly violates conservation of energy and makes predictions that are counter to observation, because it is simply a convoluted word salad projection of my own lunacy and ignorance of physics" cranks on SFN? And then they all think that the "scientific establishment cabal" is "out to get them" to "protect their own interests".

 

LOL. Mainstream science is not a shadowy government conspiracy or a greedy corporation. It's a bunch of academics trying to figure out what the universe is made of via systematized trial and error.

Doesn't the best theory we have as to how things all started violate conservation of energy in a pretty "blatant" manner?

Over and over we hear that evolution is not part of abiogenesis, that evolution via natural selection did not start until life had already formed. This leads to ideas that life is a very low probability occurrence, a figure 10^-41,000 of how unlikely the formation of life was is often bandied about as though it were the truth. I say that life is a natural occurrence driven by natural selection of the organic chemicals that come about naturally in the conditions of the early Earth.

 

Only got that far, but that's an interesting way of looking at it. It probably falls outside the definition of "natural selection" (just a guess, as I'm not an expert) but in many ways it's the same thing.

 

 

I don't think it is possible to travel against the wind (upwind) faster than the wind.

The proposed device would not differentiate between true wind and air passing over or through it.

Thus, if standing still and headed into the wind, it would start to move and accelerate up to the point where resistance to its movement would stabilise its speed.

If the actual (true ) wind then ceased there would still be air passing over the proposed device.

It would continue to move, indeed it would speed up since the drag component of resistance would be reduced.

We have a perpetual motion machine - or have we?

If the true wind disappears you have no energy source but your momentum (kinetic energy) relative to the ground.

Since you still have drag your device will eventually come to rest.

Also, you certainly can go upwind at faster than windspeed. (been there, done that, as has Sisyphus in iceboats...unless his iceboat was a real beater )

As for the bolded, the device would "know" it is moving over the ground, as the energy source it uses to maintain it's speed or accelerate is the kinetic energy of the wind relative to the ground, and the energy it expends in traction would be vehicle relative to ground. So it would "know" if it was true or apparent wind.

which isn't enough to generate lift. there should be a flat surface as well. since the sail is extremely thin (unlike a wing), it shouldn't be able to generate lift according to bernolli's law, even if it is curved.

 

by the newtainian principle, the sail would move but never faster than the wind.

 

as for benolli's, let me get this right.

bernolli states that as the velocity of a fluid increases its pressure decreases.

a fluid will move and "push" from the high pressure area to the low pressure one.

by applying that to a wing to generate "lift", we'd want the air under the wing to push towards the air over the wing to generate "lift".

that'll translate to making the air over the wing go faster than the air under it, hence making the air above it with lower pressure than the one under it, hence lift. [something like this but horizontal: l) ]

that is acheived through curving the upper side of the wing ")" and keeping the lower one straight "l" , while my common sense said that the air travelling at the longer curved surface ")" will be slower than the one travelling by the straight short surface "l" because of friction for the former, our teacher said that no, if point A and B were absolutly next to each other before the wing sliced them apart, and point A went through the "l" route and point B went through the ")" route; it is assumed they will be next to each other after the wing seperates them, and hence one would've travelled faster than the other because one route is longer than the other and we assumed the time they took through them was the same, and so, one side faster than the other, one side with higher presser than the other, sooooo, lift, ta-da.

a curved sail with uniform negligiblw thickness wouldn't have that apply to it. i don't see how it can generate lift using bernolli's concept.

 

i never bought it anyway, i think it's simply newtainian. the engine scoops the air from the front to the back, the wing flaps tilt the plane and engine up, and that's it.

 

of course the fact that scientists and engineers are debating the issue of which concept is more relative gave me a hint of how much the design of stuff is mainly chance and luck, with little brushs here and there of intentional calculations or knowldge. it's more trial and error than prediction, more of it happening then speculating why and how, than knowing the why and how and then making it happen.

The old "paired molecules splitting and meeting back together after traveling different paths" explanation leads to problems. It has erroneous assumptions leaving it only partially correct. Most sails can be made to work quite well.

There really is no debate outside of how best to explain things. Newtonian explanations are correct if the right assumptions are in place. Bernoulli's Principle is based on certain idealized assumptions and is in agreement with and based on Newton's laws.

I've sailed on iceboats also. They're lots of fun.

 

 

 

And yet it seems you can!

Well, we know we have done it in iceboats...sailed with the downwind velocity vector greater than the wind velocity...and two iceboats on opposite tacks can maintain their combined c.g going straight downwind at greater than windspeed...

Are the turbine blades accomplishing essentially the same thing?

' Have to think about it...

Can't view this ATM, but when I saw one of these videos, the controversy stemmed from the makers not doing a decent job of explaining how their device worked. I (and others) had assumed the propellers drove the wheels, in which case it won't go faster than the wind — the driving force vanishes at that point. But when the wheels drive the propeller, that restriction goes away.

Now this makes sense. The propeller must be variable pitch. It must be maintained by dynamic braking on the wheels, which drive the propeller which seemingly gathers energy...even though at windspeed the "relative to vehicle" energy source is the road, not the wind.

The blades simply push with more net force than the force of the dynamic braking, using the energy of the wind relative to the road, even when the vehicle speed matches the wind and there is no available wind energy relative to the vehicle.

Actually it wouldn't have to be variable pitch either, even at the start, though it would be more effective.

Energy is a very relative thing.

This is about going downwind faster than the wind, though. Or are you talking about sailboats?

 

No. I meant upwind. Is there something unique about sailboats? I have an iceboat, fairly common design, that will go faster than the windspeed. In light air it will go upwind much faster than downwind. While it will not go directly upwind, it gets there by tacking, and the speed made good to windward is greater than the true windspeed in many conditions.

I can't see how you could maintain downwind faster than the wind though.

I don't see anything controversial. It has to be fairly efficient to go upwind faster than the wind, but it certainly can be done. At some point the drag increases too fast for the increase in available wind energy, but this does not necessarily happen at the same speed (while opposite direction) as the wind.

"Impossible" would be having it work in no wind, even after pushing it to get started.

Also, a flat plate can generate lift, though it is not very efficient.

Worse case scenario is we calculate the trajectory to be on path to hit us, we come up with some wonderful plan to get it off course, execute it perfectly through a heroic international effort just in time, then realize it would have missed us... just prior to our compete and utter demise.

(dibs on any movie rights and royalties)

Hello everyone,

 

 

Ok so I read that the reason they are in free fall is because they are going in a circle like this , and the earth curves away from them at the same time or something, could anyone explain it to me simply. Also why don't astraunauts get pushed to the periphery of the space ship by the centrifugal force?They are not wearing belts right, do they I don't know? Thanks

Just think about this for a second. Why does the space ship not get pushed up against the astronaut in his orbit? (Same reason as explained by the previous replies, they are in free fall together)

Assume the typical co-location of origins and a light pulse at the co-location with two frames in relative motion.

 

The Relativity of Simultaneity contends if two points are simultaneous in the rest frame, then these points will not be simultaneous in the moving frame.

 

Both postulates of SR contend light is always spherical from the light emission point in the moving frame and any point with the associated time value can be translated into the coordinates of the rest frame.

 

So, here is the question. Just consider the x-axis.

 

Say two points R1 and R2 are simultaneous in the rest frame. What two points in the moving frame when translated to the rest frame coordinates are simultaneous to the moving frame when R1 and R2 are simultaneous in the rest frame?

If any two separated points, R1 and R2, are on the x axis and are simultaneous in the rest frame, they will be simultaneous in the moving frame if and only if the relative movement is orthogonal to the x axis.

(ill worded, see Swantsont below)

Events on the x axis would not be simultaneous in both frames unless the relative movement is orthogonal to it.