Strange

Part of the problem with the question is the meaning of the words "actual" and "perceived". The former implies something is more "real" (whatever that means) than the other. But relativity is all about what we measure in one frame of reference from another frame of reference. When we measure (or calculate) the energy, length, rate at which clocks tick, etc. of an object in another frame of reference, we get a different value than if it was in our frame of reference. How do we know if that difference is real? Is one measurement more real than the other? Is the difference just a perception, an illusion? Consider perspective, for example. Your friend in the distance looks smaller but you know here isn't "really" smaller, it is just an illusion. You could hold up a ruler and measure him as being 1 inch tall. But if he comes and stands next to you then you can tell he is "really" the same height he has always been. Similarly, you might say that you will only consider time dilation or length contraction to be "real" if you can put your clock or ruler next to the object and measure it. But then you are in the same frame of reference, so the difference has disappeared. (I still haven't decided if perspective is a good analogy or not, precisely because it isn't clear what "real" and "illusion" mean.) I don't think I have helped answer the question (ajb's "it's the space-time interval" is a good answer). But perhaps I have explained why it may be a non-question.

I thought that this post by Mike in another thread was highly relevant to this discussion:

It is more like someone else insisting they know who is at the door and insisting that a key isn't necessary to test their idea. Here is a list, form such a professor, of the basics you need to become a theoretical physicist: http://www.staff.science.uu.nl/~Gadda001/goodtheorist/index.html I'm sorry, I-try, but if you can't demonstrate a really solid grasp of several (ideally, at least the first 10) technical subjects on his list, no one is going to take you seriously. Firstly, it indicates you probably don't have a good understanding of the theories you are attempting to criticise or replace; secondly, it means you probably don't have a sound theoretical basis for your ideas. Note that "logic" or common sense are not not on the list.

Then why say "The challenge is for you to use your mathematical ability to prove that ? backing that statement to be incorrect" ? How can I answer your challenge, if you can't even be bothered to provide the information? But you can't be bothered to answer the simple problems put to you by physica and you can't be bothered to provide your own calculations. Why would anyone take it seriously, then? "I have a new fundamental theory" "Show us!" "Nah, can't be bothered" "OK. Bye."

Of course they are logical; after all, they are mathematical models. What people like the OP mean by "logical" is "it agrees with my preconceptions" or "it makes sense to me". People complain that relativity or quantum mechanics are not "logical"; all they mean is that they don't like the theory. Well, that's tough: they work. What do you think the purpose of science is? (In other words, what do you think "getting to the bottom of things" means?)

I don't think that is a common definition of faith. For most people, I don't think it involves any effort at all. It just is. And I don't why your blood flowing through your veins would require faith. (Or effort, for that matter.) Correct. Art may be valuable but it is not science. They may well do when talking about ideas, belief, philosophy, human nature, ... But that has nothing to do with science. No theory is proven one hundred percent. No theory is proven at all. It just not disproved. Yet. And that is a good first sign that they are crackpots.

Related to that, it is quite possible to have multiple theories to explain some phenomenon. For example, both Newtonian gravity and GR make predictions about the effects of gravity. In many cases, they are equally accurate. In some cases, GR is (significantly) more accurate. That does not mean that GR is "true" and Newton is "false". (Or that one is more "logical" than the other.) One model is more accurate than the other. That's all.

No, not explain why you think it is wrong. You need to actually SHOW that it is wrong. Quantitatively. In appropriate mathematical detail.

As far as I know, one of those explanations corresponds to a scientific theory and the other doesn't.

The theory IS the relationship: the theory says what results to expect from the experiment. Either the experiment matches the experiment or it doesn't. If it doesn't you modify or discard the theory. I don't even understand what you are looking for. (Except, perhaps, that you want the theory to make sense to your intuition.)

My understanding is that plasma, and ion engines generally, can only produce low levels of thrust but do so very efficiently. So they do not produce enough thrust to overcome gravity, but are suited to long duration missions where a small acceleration for a long time is useful.

There is no "logic relationship" - there is only the predictions of theory versus the measurements. You have no predictions (other than "it is yes or no", which is not very helpful) therefore your comments are not useful. Not even science, in fact.

If that were the case, then I would soon find myself on the floor as my chair moved from under me.

I can assure you that my chair is not moving relative to me.

What is?

I'm curious why you think that. If, for example, the particles is stationary relative to you when you measure its mass, then you are measuring its rest mass. No? Then what do you think it is?

Do you need a hand moving those goalposts?

You do know that velocity is relative?

Mass is measured, not calculated. (At least, I can't think of an example where the mass of a particle is calculated. Theory will sometimes give an expected range.)

That has absolutely nothing to do with the topic.

I would think this belongs in the Medical Science or Physiology section. I would assume the heating is simply a result of the physical exercise and, perhaps, changing blood flow to the head. And/or possibly some sort of autonomic response to the disorientation produced (i.e. related to the sickness which results from disturbing the fluids in the vestibular system in your ears). I am fairly certain that this does not need magnetic fields or superconductors to explain it. I would also point out that you are not "rotating" your head (I hope!) but oscillating it back and forth.

I am remarkably unembarrassed about being consistent in trying to get people to understand what science is and how it works. (And ocassionally, pointing out the value of brevity and paragraph breaks.) Yep. Without it you are not doing science. If you attempting to increase your own knowledge, then you can get a very limited, crude and flawed understanding if you only have basic mathematical ability. (That is me, by the way). If you are attempting to increase human knowledge, make breakthroughs in new physics, then to say that mathematics is absolutely essential and indispensable would be an understatement. It would also be essential to have a very solid understanding of current theory. I guess you are thinking of something like Faraday and Maxwell, here? The point about that example is that Faraday was an extremely good experimentalist who collected large quantities of data. He demonstrated a number of phenomena which were then formalised mathematically by Maxwell. I haven't seen you presenting any quantitative data that could form the basis of any such work. Not at all. I have a limited knowledge of physics and math. I rely on people with the appropriate expertise to make the necessary breakthroughs. Would you expect your plumber to do brain surgery, just because he knows a little more basic first-aid than you? And yet you are unable to provide any support for this idea. I have seen the various flaws explained in great detail on various forums, just for you to dismiss them. We have quantitative experimental data and useful predictive theories for our current models. You have some vague qualitative ideas with no reason for anyone to take them seriously. I have skimmed through the thread again and have been unable to see where you derived your value for the acceleration due to gravity. Perhaps you could reproduce it here.

Classically, you can view it as the runner encountering the waves faster because he is running through them. Or, you can think of it in terms of energy. If it were a tennis ball, they would disagree with the kinetic energy the ball has. Similarly, they disagree about the amount of energy the photons have; in other words, different frequency.

I don't see what is differnt. The core contains electrons. (All matter contains electrons.) It does not generate electrons. The movement of electrons in the core generates the magnetic field. I don't understand the details (which is why I just pointed you at the Wikipedia page) but apparently there is a complicated mechanism where the magnetic field causes electric current in the liquid core, those electric currents generate magnetic fields, which generate more currents, ... And it is all driven by the heat and rotation. As people have only recently been able to model this, I think it is going to be more than you can understand (as you struggle with simple things like speed and acceleration). Er, no. They will not penetrate more than a short distance into the Earth (a few tens of centimetres at most, I think). Most will not even get through the atmosphere.

It is a combination of theory and evidence. The structure of the core (molten with a solid inner core) is know from seismology. There are also theoretical models for the structure and composition of the core. There also (as the Wikipedia article says) models of the mechanisms for the generation of the magnetic field. Because there is no mechanism for generating electrons. Vecause the presence of electrons would not turn iron into a magnet. No. There is no mechanism for the mantle to generate a magnetic field. There is no mechanism for the core to generate electrons.