timo

In the form SR is usually presented you are limited to Lorentz transformations which the boosts are part of. With a little generalization you can go to arbitrary coordinate transformations. If you extend this to non-flat spacetimes you´re at GR. To really understand what "spacetime is curved" means you´d best read up on differential geometry. Keeping the surface of a sphere in mind as a good example of a curved surface might help. The big key to understanding GR is to realize that there exists a vector space of velocities, momenta, ... at each point of spacetime while spacetime itself (position) is not a vector space. @Halucigenia: The problem is that r is just a parameter with little physical meaning. So by comparing ds with dr you compare a physical quantity (lenght) with an arbitrary parameter. In this case, the parameter is chosen to equal a lenght if no spacetime curvature due to mass was there so one could argue that this comparison makes a bit of sense. I also thought about this example earlier on but in the end you are comparing two different spacetimes which makes argumentation a bit vague, I think.

Yes. See the PM I just sent you for further details and consider my suggestion to make up a seperate thread on this topic if you´re interested in discussing it.

As far as I´m aware, epistomology is a branch of philosophy, not a branch of relativity.

Imho, you´re also highly suspect. Can´t you just make up your "I haven´t understood relativity but I can prove it wrong"-thread like everyone else instead of spamming every thread with your b-theory and waiting for someone to catch the bait?

GR predicts spacetime to bend (space and time, as I allready said). But without the math behind it (and therefore knowing what "bending" means) this statement doesn´t tell you very much. And my point was not only a "what experiment would you do to check it?" but more a "what do you mean by space being contracted?". Perhaps I´ve got an idea how to construct a statement you might like: We have agreed that due to gravity the time measured can differ at different points in space and call it "gravitational time dilatation". What we might want now is an example that the distance between two points in space can change with time. An example for this would be the cosmic expansion. In our current model of the universe the distance between two fixed points increases with time (the picture with the baloon you might have already seen somewhere). Like I said, that analogy is pretty much made up. But as I already tried to say, statements like "time slows down due to gravity" are mainly ones that are made up for laymen to fool them into believing they understood something, anyways.

In the of the 70s there was a group of terrorists that called themselves "Red Army Fraction" (RAF) that frigtened a lot of people with kidnapping actions and bombing (and perhaps a bit because of the lot of attention they got in the press). Believe it or not: Those people weren´t even muslims (sry, I couldn´t resist this statement )! The first time they kidnapped someone (Peter Lorenz, perhaps there were other occasions before, I´m no historian) the german goverment agreed to exchange him for some terrorists that were held captive. The 2nd time the RAF tried to pull this off the german goverment refused to negotiate with terrorists and made this attitude an official one. The hostage (Hanns-Matrin Schleyer) was shot. To my knowledge, no one tried to free fellow terrorists by means of kidnapping since then. Afaik many people regard this change of attitude as a turning point in dealing with the terrorist. The RAF announced its disbandmend in 1998 after not having been recognized for years, anyways. You might guess that I voted "no". If you´re interested in the RAF stuff better read up on it and don´t trust my words too much. In the active time of the RAF I was still a child and all I can remember from then are posters in the post offices showing the most wanted terrorists.

"Time slows down" is one of those quick and easy statement that tell you absolutely nothing if you don´t know what´s meant with it but somehow make you (erroneously) feel you understood something even if you don´t know what´s meant. So what could it mean? Perhaps it means that if you synchronize two clocks, bring one to another place, leave it there long enough so that the time dilatation due to the transfer process becomes irrelevant and finally bring them back together, the two clocks will have measured different times. That´s in fact (sorry for the long sentence) what I´d think of the "time slows down"-statement in the context of gravity. And here comes my point: I wouldn´t spontaneously know how to construct a similar experiment for space so I don´t really know what could be meant with "does gravity contract/expand space". If that was too abstract I also have one of those non-saying statements that´s absolutely correct and might do the job in pretending to be an answer: "Yes it does. Mass affects spacetime which is both: Time and space." Your question isn´t bad but it starts from a very vague point. @Wormholeman: What´s the name of these guys you know ? EDIT: Thx for the link. The HP looks nicely made and some of the articles there actually look interesting.

How does one measure a wall? And I believe he had written "clock" if he had meant a clock. I do not think Blike was up to the question whether there is a difference between 20m and falling down 20m but more up to the question whether time is relative or an absolute and whether it´s an improper measurement that fools us in thinking that time is relative.

Linux at work, Windows at home. So what am I supposed to vote?

There are two different types of time: Coordinate time which is relative (like the coefficient c_x of a vector v = c_x e_x + c_y e_y + c_z e_z in R³ being dependent on the base {e_x,e_y,e_z}) and eigentime which is absolute (to stay in the R³ picture: The length of the line between two point is indepentent of your coordinate system´s orientation). For the difference of "measurement of time" and "time itself": Sounds pretty philosophical to me. You measure something and if it is an invariant then the result is an invariant. If it isn´t, the result isn´t.

No it isn´t. Otherwise, some babies dying in an early age must have had quite a rapid pulse. If you meant that there´s an individual fixed number: Yes. You live, then you die. And inbetween your heart made a certain finite number of beats.

I still haven´t heard a definition for a gravitational wave in Newtonian Gravity so it´s really hard to give a competent answer. Nevertheless: What does "acceleration of a field" mean? Why? What is "sinosodaly" ? It´s certainly nothing like A*sin(wt). Or else you´d have to explain to me how the gravitational attraction can change its sign. Perhaps. Depends on what a gravitational wave is supposed to be. There is no flaw in it if one just sufficiently stretches your terminology.

I´ve seen a lot of people of whom I simply knew they were going to die soon. I don´t think it comes to much of a surprise that humans can intuitively feel the another person´s condition from signals you don´t recognize wittingly (empathy). Might also work on animals but I haven´t seen any that was dying shortly afte.

I think that your pictures are 2D with the measured intensity plotted as height. So the answer would be "no". As another matter of fact you have to keep in mind that these are not pictures of free atoms but of bound ones. What´s the difference between those two things? On the scale we seem to be talking about there is no such thing as a sharp boundary of an atom as you might guess from the pictures yourself.

The code commented out could make sense if, for example, for some reason you are given a node and want to have the element that´s two levels above it in the list. It´s just a different type of list (doubly linked). It really depends on your application what kind of list you need/want.

You know, I´ve been trying to get some usefull information for 5 posts, now. But I´m getting bored with it. Perhaps you could take over?

But in contrast to Newtonial Gravity, Electromagnetism is a relativistic covariant theory and has wave-equations (d´alambert field = source) as their field equations. Newtonian Gravity´s field equation is a Poisson equation (laplace field = source), if I remember correctly. I can´t see how wave-solutions are to pop out of this. And even though I am risking to be repetitive: I do not think that anyone doubts that moving masses create a change in the gravitational potential in Newtonian gravity. I was just thinking that your were saying more than this, perhaps.

Guess I was wrong ...

I have my doubts that many people here are able to help you. After all, this is a science forum and I think scientists usually tend to use the international standard units (or at least similar systems). Just out of interest: Do you have any CAD application in mind where this relative difference in the order of 1/10,000 would play a role ? A rough guess of mine would be that noone does precision measurements in inches, so the 25.3995 just became accepted as 25.4 because the difference doesn´t matter anyways. Not that I´ve ever used inches in my life, that´s just my two euro-cents.

>> Question, as the 1st code, LinkedList class apears, I dont know exactly what is the >> code within the comment mark does if I un-comment it. Your currently introduced linked list works the following way: There is a master node called head that the class knows itself. Each element (including head) then know the respectively next element in the list. This way, you can find each element by parsing the list. The "prev" entry of the list is obsolete as it isn´t used. If you un-comment the part you mentioned the "prev" property will be set. This is: Each item in the list will not only know the element that´s coming next, but also the element that comes before them. >> Can any one tell me is there a reason for the code that's in comment mark in bold?? Perhaps because it´s a comment? For me, comments are much more important than actual code when I read other people´s code (so from this point of view, the code snippet you presented is crap). >> To my understanding, it [the oucommented part, if it was in] just makes the Node >> head object bigger in size by storing a reference to an object that has a refernce >> to itself. I don´t know Java so I might be wrong here. But what determines the size of an object (and all it´s nodes, then - not only the head) is it´s variables defined, not the variables used. So with or without the commented part, your nodes will have the same size. You´d have to remove the superfluous "prev" variable to reduce your list´s size.

I know I can be a little pedant from time to time but can you be a bit more specific or elaborate more. I understand almost nothing in your last post. Only statement I understand the first paragraph. And considering that one, banging my head against a wall would classify as a gravitational wave because it has a detectable effect and transfers energy (even through a particle exchange if one really wants to treat it with QED). I mean: You want comments on your statement that Newtonian Gravity predicts gravitational waves but you do not say what a gravitational wave is supposed to be - at least not in a way I´d understand.

Ok, I see what you mean. But that´s nothing else than saying the gravitational potential changes because the point of mass generating it moves. Perhaps I could understand your statement better if I knew what a gravitational wave is supposed to be...

I know what a center of mass is, I know what a sphere is and I know that spherical symmetric mass distributions (outside the distribution) have a gravitational field as if the whole mass was in the center of mass. I do not, however, know about a "center of mass theorem" or a "sphere theorem". What is that supposed to be? The thing about spherical symmetric masses I mentioned above? Afaik, that´s no approx. What is a gravitational wave and how is that predicted by these "theorems"? .Newtonian Gravity has is ruled out by a) the light deviation and b) the non-elliptical orbits of planets. Both effects can also be explained with Newtonian Gravity but with incorrect numbers. I can not see how the point that Newtonian Gavity predicts gravitational waves (regardless whether it acutally does or not) affects the implication of their existance for GR.