MigL

Technically protons don't bind to other protons. The quarks making up the protons bind via the strong interaction ( QCD) and some 'residual' interaction binds the quark-containing-protons together. This only happens when a given separation is reached. At greater separation protons repel just like electrons since EM force is dominant.

Not a stupid question at all. Voltage is a potential and the analogy you may be more familiar with is gravitational potential. Think of the potential or voltage as the height of a waterfall. The current would then be the mass of water going over the falls. The potential provides the motive "force" for the current.

You stand on a scale watching a spaceship pass by at a uniform 0.95c and you apply the SR equations to find that the ship's relativistic mass has increased by a significant amount. The pilot of the ship is in an inertial frame and measures your speed to be 0.95c relative to his ship ( which one is actually at 'rest' has no meaning ). He calculates your relativistic mass to have increased substantially. You look down at the scale, What does it say ??? Is it substantially increased from normal ??? Or does it still say your rest mass ???

"You won't learn a great deal of physics on a forum", but you will be steered in the right direction where you may. The rest of us have tried to steer BusaDave in the right direction and even stating that you "won't argue further" and "this is it" for you ( a little condescending ), you do make a very valid point about modern Lagrangian formulation and the outdated use of the term 'force' for the four elementary forces. Gravity may even turn out to be a fictitious 'force' much like centrifugal or coriolis. If you are willing to make further contributions, they will certainly be appreciated by us all. If not, thanks for coming out.

I'm discussing airborne radar, not ground based. No airborne radar uses multiple paths unless two are working in sync through a datalink. I know exactly how LEDs work and semiconductor lasers and they do emit on a single frequency. But note that I was suggesting their use as substitute to camouflage, ie to the human eye's detection. But at 50 mi. separation do you think it matters if the emitted three frquency peaks are separated by microns as on an LED panel when detected by a dish 18" across? And yes I agree all aspect stealth takes ALL emissions into consideration. I did not understand your third line where you worked on radar systems and " For bad reasons, and I'm not available for this". What do you mean by that ? Can you elaborate ?

It is fortunate that for you, machapungo, assertions don't have proof or supporting evidence, otherwise I could assert that you don't know what you are talking about.

No Enthalpy, it can work in all directions, but only against one radar ( unless you have multiple steerable transmitter modules and immense computing power ). It works in all directions because the generated interference beam is electronically steerable and the whole plane doesn't have to be covered with antennae since at a detection range of about 50 mi. the whole target airplane appears as a point source. Radars don't discern features on the target aircraft after all, or there would be no need for IFF. As for LED's frequency not being agile, is your LED TV black and white, or can it produce millions of colours ? Also can laser diodes not produce phase differences ? You are right that single radar engagements ( at least on our side ) don't occurr anymore since there are always multiple aircraft joined by Datalink and possibly even AWACS control.

Historical Notes: In the late 60s/early 70s, the US became interested in low-observables due to their Vietnam experience. DARPA asked major aerospace contractors to submit proposals for a demonstrator program. Lockheed wasn't even asked since they hadn't produced any fighters for the USAF since the 50s. Kelly Johnson had to ask permission of the CIA to declassify their experience with L-O during the U-2/SR-71 programs so that they could make a submission. This is the path they chose. In the late 19th century, James Clerk Maxwell developed equations which describe Electromagnetic behaviour and phenomena. In the early 20th century, the German EM expert, Arnold J. Sommerfeld, refined Maxwell's equations to predict the manner in which a given geometric configuration scatters, or reflects, EM radiation. The Russian physicist Pyotor Ufimtsev, developed an alternate approach to Sommerfeld, by cosidering the EM currents along the edges of geometric shapes. This was still considered much too cumbersome to be applied to anything other than simple geometric shapes and forms. It is at this point that Lockheed comes in. One of their software engineers and a retired mathematician named D. Overholser and B. Shroeder, used finite element analisyss to reduce complex aircraft shapes to a finite set of simple 2D surfaces, using a program developed in five weeks, called ECHO 1. This is the origin of facetting where simplified calculations allowed L-O to be modelled mathematically and predicted. The first design was an unflyable diamond shape. This was modified with wings for HaveBlue, and further modified for the F-117 Nighthawk. The other candidate chosen for a demonstrator was from Northrop/Grumman and was more of a 'best guess' or 'shot in the dark' design. It used no facetting. Its fuselage looked like an upside down bathtub with smoothly chined sides and a dorsal intake, but it provided them with invaluaable experience to build on for their B-2 design. Tchnological notes: Electromagnetic radiation intensity falls off with the square of the distance ( the reason for this has been explaned numerous times in the Physics Forum ). What this means is that the searching radar is always at a disadvantage. It has to deal with twice the separation or a quarter strength return from the target while the target sees the searcher at the original intensity. Radar is, in other words, unuseable in combat. Its like searching for an armed enemy with a gun and a flashlight. You have to see his dim reflected light to shoot at but he only has to see the beacon of your flashlight to shoot at. Most new combat aircraft use passive detection systems like IRST and do not use active like radar in combat. If, however, you are trying to penetrate an area for attack purposes where the defenders don't care that you can 'see' them, it makes sense to be as stealthy as possible. One way of acheiving near invisibility is by using massive computational power to analise the search radar's signal, then using the equivalent of a ray trace program and an electronically scanned transmitter array ( as in current AESA radar sets ), to transmit a signal which is equivalent to the search radar signal but 180 deg. out of phase. This will interfere with the search signal making the return to the search radar zero. This should even work with LED transmitters in the visible light spectrum such that camoflage is no longer required. Note that the analisys of the incoming signal doesn't have to violate special relativity, it just needs to be done faster by the target aircraft than the searching aircraft. This should not be a problem since the target aircraft has a much more intense sighal to work with, while the searching aircraft has, at best, a quarter strength return and is at a disadvantage as was previously discussed. Note that this kind of attenuation system slready exists in inexpensive noise cancelling headphones for sound waves. This technology will eventually migrate to EM waves.

Its funny that your illustrations of stealth aircraft always show F-117s, which is 1970s technology stealth. At that time the EM dispersion equations had to be solved rather simplistically with the available computing power, and the simplistic solutions involved facettung and angles such that the F-117 and its predecessor, HaveBlue, were nearly impossible to fly. With todays massive computing power, facetting and extreme angles are not the only option. The Northrop-Grumman YF-23 and B-2 , Lockheed F-22 and F-35 as well as Boeing's X-32 ( along with numerous UCAV designs ) show very little if any facetting and are among the most maneuverable current fighters. EM waves such as radar are particularily fond of cavities like intake and cockpits. The X-32 used a screen in its large intake for this problem ( and may have used additional means to reduce RCS ) and ALL stealth aircraft have their cockpit glazing coated with a layer of gold to get rid of the cavity effect ( take a look at a picture of an F-22 for the telltale gold sheen ). Radar waves also creep over metallic structures and re-radiate from edges if long enough. Notice that ALL access panels and bays on the F-22 have serrated edges to minimise this effect. There are manythings that have been tried over the years, including part wave reflectors, which reflect incoming radar twice such that the two reflections interfere with each other. Unfortunately this only works at one frequency and would be useless against modern frequency agile radars. The first radar absorbent coating used was composed of ferrite particles embedded in paint and graphite is a variation on this. Stealth is not new and Lockheed's Skunk Works under Clarence ( Kelly ) Johnson was working on it in the 50s with the U-2 program, in the 60s with the A-12/SR-71/YF-12A program and in the 70s with HaveBlue. All of this is documented in any good book detailing the history of the Skunk Works or of the airstrips in the Mohave desert where all the nuclear testing was done and the Lockheed spy planes were developed for the CIA ( otherwise known as Area 51 ). If your company's coating was so effective don't you think everyone would paint their planes with it and have instant stealth? Why are they still spending billions of dollars to develop new stealth designs? The best coatings available, applied to the intake ducts of the F/A-18E and the F-15 Silent Eagle ( they were not developed with serpentine ducts to hide the compressor faces ) only reduce the RCS by less than an order of magnitude, and if you know any physics, this only marginally shrinks detection range.

Consider a torus, studiot, where the two dimensional surface is a simplification of our 4D space-time. We can picture this 2D surface in our 3D space as a doughnut shape. So this 2D surface needs embedding in a higher dimension. We note however that this surface is not simply connected, ie. a loop around a certain section of this space cannot be drawn down to zero radius ( around the inner 'hole' and normal to the outer diameter ). This implies certain directions are favoured. We also note that around the outside of the doughnut the curvature is positive and triangles have more than 180 deg., while on the inner surface the curvature is negative and triangles have less than 180 deg. such that there are also preferred rotations. This means an embedded torus lacks translational as well as rotational symmetry. Now consider a flat torus which we can picture as a map where the top is identified with the bottom and the right side is identified with the left. We note that even in 3D we cannot picture it because its curvature is intrinsic, ie. it doesn't need to be embedded in a higher dimension. We also note that in this case, translational symmetry and rotational symmetry is preserved. This is a good thing because if they were not, according to Amy Noether, we wouldn't have conservation laws for momentum and angular momentum. Keep in mind that I'm certainly no expert in topology, so some of my reasoning may be flawed.

Consider the set of real numbers and place them on an infinitely long yardstick studiot. The set is infinite and is spaced at 1mm intervals between numbers. Notice that this infinite set comfortably fits on the infinite yardstick. We now take each of those numbers and double it such that 1 becomes 2, 2 becomes 4,etc. by removing all odd numbers. Note that we have a one to one correspondence between the original set and the new set ( one might think that the new set is smaller since it only includes even numbers ). Both are infinite and both comfortably fit on the infinite yardstick, however the separation between adjacent numbers has now doubled or 'expanded'. Maybe 'expand' isn't the proper term to use, but your argument doesn't negate the option of an infinite universe. Since you are familiar with Poincare and Reimann, I would assume that you realise a geometric space does not need to be embedded in higher dimension. It may, but it doesn't have to be. So, yes, a finite universe is also an option. In bot of these cases, however, I prefer the unbounded option. Only because I wouldn't want to explain what's on the other side of the boundary.

So, just to be clear, we all agree that an asymmetrical airfoil of the Clark y type and zero angle of attack will produce lift due to the Bernoulli effect (reduced average pressure above the airfoil due to higher fluid speed above the airfoil ). Whether we invoke Jukowski's circulation or not, Bernoulli is very easy to explain. If we consider a streamline to be a tube, then, in the absence of sinks or sources, continuity dictates that the amount of fluid entering is equal to the amount exiting. If we now introduce a constriction in the pipe, that same continuity condition dictates that the fluid must speed up through the constriction so as to pass the same amount through a smaller area. There is only one force in the tube that can spped up the fluid as it enters the constriction and slow it down again as it exits the constriction, and that is pressure. The pressure in the pipe ahead of the constriction must be higher than the pressure in the constriction to speed up the fluid, and again, after the constriction it must be higher to slow the fluid down again. Through various 'slight of hand' arguments, we can consider a square tube for the streamline, move the opposing side of the tube out to infinity and even get rid of the tube altogether leaving just a D ( on its back ) constrictive element to represent the wing. That is my verbal explanation for Bernoulli lift. If, on the other hand we consider wings, flat plates or even hands sticking out a car window at speed, we note that to produce lift an angle of incidence MUST be used to produce a very inefficient lift with lots of induced drag. That is how planes can fly upside down, and it doesn't involve Bernoulli. And that is the crux of my original discussion with John.

The rotation and resultant pressure difference suggested by Bernoulli's principle are due to differntial curvature or camber of the airfoil. No one would suggest that a flat plate of zero thickness, parallel to the airflow would induce any rotation or pressure difference. Alternatively place an a Clark Y airfoil ( curved top, flat bottom ) in a wind tunnel with flat attitude and notice that there is decreased pressure on the upper curved surface as compared to the bottom. The lift is then up, towards the direction of the ceiling. If we now take the whole apparatus and flip it upside down, wind tunnel and enclosed airfoil, are you suggesting the pressure distribution and the resultant lift is still the same and still in the direction of the ceiling studiot? I'm sorry, I have to side with John on this one ( unless of course, you prove me wrong, I always hedge my bets ).

But it has been discussrd at length that its not just Bernoulli's principle which accounts for the lift. Heck even a flat plate at a certain angle of attack will produce lift. as a matter of fact the most efficient supersonic wing profile has zero thickness and a flat top. The point remains that a plane can fly upside down, although Bernoulli would suggest it can't. due to other lift producing effects.

I assume, since you think aircraft design is a crap shoot, you don't like to travel in planes much then John ? Or are you just playng devil's advocate to explore this 'interesting philosophical point'?

That's like sayng we didn't know how gravity works when all we had was Newton. We still needed to learn Einstein's viewpoint, and as a matter of fact there is and always will be more to learn ( quantum gravity etc ). But we put men on the moon with Newton !!! So we don't have exact solutions for the Navier-Stokes fluid flow equations, but we have approximate computational methods which work just fine for the application. Even though sometimes they need refinement in a wind tunnel.

In GR the equivalence principle applies to inertial mass and gravitational mass, also, gravity is not a force but a space-time curvature. Being in free fall means there are no forces acting on you. The only force is the earth pushing 'up' on your feet when you are NOT in free fall. That's why we measure weight in units of force and acceleration in units of gravity.

No, its most accurate to say inertial mass and gravitational mass are the same. As for acceleration and gravity, if they produce the exact same effect, how are they not equivalent? Is acceleration not measured in Gs?

If no-one knew how lift works, it would be pretty hard to design aircraft that stay up in the air. Last time I checked, airplanes weren't falling out of the sky like rain, so we must know something.

sorry meant to say that a 1 pound difference in pressure would be equal to max take-off weight.

Let's see, a Lockheed F-104 Starfighter, with one of the highest wing loading of military aircraft ( ie. small wing, high weight ) has a wing area of approx. 190 square feet. That comes out to over 27000 square inches. which means that apressure difference between top and bottom of the wing would be equal to its max take-off weight ! I think you may have made a mistake in your math gnerosy.

Well you can't be that sure because you have special and general mixed up.

This is Ernest Mach's idea from the 1880s. GR has a Machian "flavour" since Einstein was familiar with Mach's work.

Mass is not the only thing which will curve space-time. Higg's bosons only manifest themselves when the Higg's field ( as part of the Higg's mechanism ) becomes active. That is at a particular time after t=0 when the available energy is suitable.

How very Machian of you.