The trend in relativity today is to make the subject seem as complicated as possible. This complication is nothing more than elaboration on the three principles stated above. Prime examples are the invariant interval, the Lorentz diagram, expression of relativistic quantities in terms of angles (and expressions of various quantities in terms of sin, cos, sec, tangent, etc.). The latest fad is to express Special Relativity in a mathematical notation that mimics General Relativity mathematics. Time is called x0 and the three spatial directions are called x1, x2 and x3. This shows the current tendency in physics to treat Special Relativity as just some kind of tepid prelude to the real science of General Relativity. I don't mean to say that its wrong for people to study these elaborations, but any analysis that can be done using the elaborations can also be made directly with the three principles and get the same results.
Why has complexity taken over relativity? Physicists want to find something to publish but true advances are few and far between. So, they end up just elaborating on things that are already established. Although physicists hope that something good will come from all this analysis, the end result is that students are fed hugh amounts of complicated material that doesn't add much to the science. If you like that kind of study, then by all means pursue it. But I see students getting confused by the complexity. If you visit relativity blogs and chat rooms, you get neverending discussions on the twin paradox and world lines. The real relativity is in danger of being lost.
The goal of this web site is to cover things that have not been covered before. All of the articles on this web site refer constantly to the three principles, but use them to solve new problems (or old problems in new ways). In addition, the Law of Conservation of Momentum and Law of Conservation of Energy are used (these laws are also an embodiment of Newton's laws). These five ideas are all you need to construct anything on this web site and any (valid) idea within relativity.
Let's take these five ideas and jump into the deep end. If you've read this far, you know what a 'wormhole' is. Suppose a mass is at the entrance to a wormhole, moves slowly into the entrance and a short time later appears at the other end, a great distance away. Think about this wormhole as Newton would. To do this, draw a boundary around the wormhole and make it an isolated system (free body), just like you did in high school. What happened to the Law of Conservation of Momentum inside the boundary? Remember, there was no momentum change outside the boundary. A mass has traveled a great distance in a short period of time inside the boundary with no reaction force. Yes, I know that space-time folded back upon itself and the mass really didn't travel that far. You've got to be kidding. You have a choice of analysing this experiment with Newton's Laws (which have been proven to be correct every time they were tested) or that space-time folds back upon itself (which has never been tested). If you believe that wormholes exist in the face of this simple explanation, then you will not get much from this web site.
Let's take on another subject: black holes. Suppose an asteroid is falling into a black hole. Today's physicist will tell you that the asteroid achieves the speed of light just as it gets to the event horizon. The same physicist will tell you that the mass of the asteroid would become infinite when it got to the speed of light. Yet, no black hole is claimed to have an infinite mass. In addition, the asteroid would acquire an infinite amount of energy as it reached the event horizon. Think about that. That's all the energy in the universe and then some...for every asteroid that falls into every black hole in the universe. That's impossible.
I know what you're thinking. You've been told that time slows down as the asteroid approaches the event horizon, so that it never really gets there. But that doesn't explain anything. Really. You have all those near infinite masses from all the fallen asteroids frozen above the event horizon and nobody notices the many superimposed near infinite gravitational fields? You have a planet that once imparted a rational energy to a falling asteroid and now this same planet imparts infinite energy because its density is higher? Infinite!? This web site will offer the simple explanation.
On this site, you will see a lot of examples that you haven't seen before. The reason you haven't seen them before is that they are unsolvable by the more complicated methods currently being taught in universities. A man is standing on the surface of a planet and reaches up to a higher gravitational potential with a pole. A man at the higher level also has hold of the pole. The man on the bottom pushes on the pole. What force does the man at the higher potential feel?
General Relativity cannot answer that question. You have been told that General Relativity is the only way to analyze gravitational experiments, but this simply isn't true. Special Relativity can easily handle gravitational fields and does so in the articles on this web site. Einstein already made Special Relativity handle gravitational fields. General Relativty is an overlay of complex mathematics on a Special Relativity framework. General Relativity doesn't invalidate Special Relativity, it incorporates it.