michel123456

Because some people here firmly believe that the donut will have no hole. If I understand clearly. Then why do some people here believe that time dilation and length contraction "truly" happen?

I have no problem with anything you wrote above. BUT tell me, when observer B that sees no hole in the donut will extend his arm and take the donut at hand, will he get a better information or not? Will he see the hole in the donut or not? Will the donut "truly" lack a hole? That is the question.

No, no. It is ok to appear happening. It is OK to appear an infinity of times differently. But there are no rock "truly" time dilated in different ways at the same time.

When you state that the 3 results are "truly happening" at the same time then there is a problem. If you don't understand it then you may have an issue concerning the relationship between your neurons. It is absurd. It is wrong. You believe that the observer dictates what the height of the Burj al Khalifa is. Is that it? You believe that the tower has multiple heights at the same time because there are multiple observers? It is not science, it is Harry Potter.

You should ask yourself the question when you use this Theory to describe the single birth of this Universe and proclaime that it happened this way because we earthlings are seeing it this way and we are correct. To me, reality is what it is in its own frame. It is not a convention, it corresponds to an origin point in a diagram. You put the origin at the intersection of all viewers, and the intersection is at the event of the observed object. For C, which is observed the same in all frames, there is no issue of ambiguity, there is no need to be in the photon's frame. Anyways all observers agree, no matter the frame. Exactly. You will be time dilated for me, and I will be time dilated for you. We agree. But if you insert a 3rd observer that says I am more time dilated than you think I am, you will realize that it is just a matter of measurement. I cannot be time-dilated and double-time-dilated "truly" because someone decided to turn his telescope on me. That is nonsense.

Yes. (for the bold part) And there is one single reality. As you say, we just have a different view of ....what? of reality. Yes. There are no many overlapping realities. It would be like accepting that events in space-time overlap. The observer has absolutely no power to change the reality. The concept following which the observer dictates what is happening is bogus. Except when he does dictate, in a lab. AND when you get to realize that you may understand that you cannot use a theory that is fundamentally observational, you cannot use this Theory to describe a supposed absolute single event like the Big Bang. But that is another fight.

That is my example of lab A. Even you will recognize that the same event will not appear the same for an observer B in a different frame B traveling nearby the Earth. You have the Theory and the maths to calculate it.

So the photon has a true velocity or a false velocity? The rocket that goes from one galaxy to the other has a true velocity or a false velocity? As seen from Earth, will it be recessed also? (I mean "transported by expanding space" as the galaxies are supposed to be, or will it remain a dumb rocket that must travel like you & me only through regular space?. Sorry for being sarcastic again.

I see. So it must have been something like the below (I have stolen your diagram and add the Earth & the camera) Where the path of the Moon is perpendicular to the diagram's sheet of paper in such a way that the umbra is constantly missing the Earth.

Yes. Think of it this way: you have 10 observers observing the same object, they see it contracted in 10 different ways. Then one of the tens (say observer A) takes the object in its own frame and says, look guys, I was right, the object "truly" was contracted the way I calculated it. But observer B could also do the same and shout : I was right! Then comes observer C and takes the object in his C laboratory and say that the object contracted the way C calculated it I don't know if you follow, but it gets insane. Much worse than Schrodinger's cat. It is not possible for the object to get "truly" contracted billion times differently at the same time because there are billion observers, and all that billion contractions "truly" happen. The observer has absolutely no power upon the observed object. However, it is possible for a single object in a specific state to be observed differently by different observers in different frames. In this case, It is a matter of observation and not a matter of things "truly happening". The only single state of the object on which all observers will agree (I mean all observers will see the same thing) is the state that is observed from the frame of the object. In all other situations the object will be seen in different states (that Relativity tells us the relations), none of which is "true". --------------------------------------------------------- Now, if an observer A in his A laboratory exerts forces upon an object O, of course he will observe that the result of his experiments comply with Relativity, because the lab is still in frame A. There is no ambiguity, it all happens as seen from A. But if you could put lab A in a frame X, then observer X will observe object O differently. Which means that object O didn't "truly" contracted. It contracted only as seen from A. It is not so complicated.

My bet: you are born 1956

You did it again. One sentence says white, the other says black. AND there cannot be 10 "real" different length contractions for a single object. Each observer measures a different length contraction, that's all. and if you go next to the measured object and join the same frame, you will measure no contraction at all.

John Mayall! woaw that is a very ancient memory. Who?

You haven't answer my questions. You have been contaminated. How many length contractions do truly happen when there are 10 different observers in 10 different frames?

So? what is your conclusion of all this? That the wrist watch is time dilated because some observer somewhere in the Universe is measuring it from a different frame? Or that the guy with the wrist watch is really length contracted for the same reason? Because time dilation & length contraction are supposed to truly happen? This is nonsense. If there are ten observers in 10 different frames, how is the watch time dilated? Or length contracted?

Dear Mordred with all my respect I think you are confused this time. Or at least you are confusing me. Half of your arguments i agree with but you use them to say the contrary.

I thought the size of the umbra would be the same as the size of the Moon, taken that ray lights coming from the sun are parallel. And there was no eclipse at this date

Yes I agree, it does not shrink or expand. It is like it is according to your frame. It is not a theory that says how are things, it is a theory that says how one will observe the world according to his frame. It counts also for the way we are observing muons. If a theory describes accurately observation, you will be unable to escape. if the theory predicts that you will observe ions as discs flattened in the direction of travel then you must not be surprised to discover that it happens in your laboratory. But it has been said repeatedly that if a spaceship is observed as length contracted from the Earth, the astronaut will feel no contraction at all. (he will see the Earth contracting). In this sense yes it is in the eye of the beholder.

It is wrong. You admitted before that Relativity is a theory of observation. The world does not expands or shrink because of the observer. What happens is that the observer gets a deformed image of the world. There is no "relationship". The Speed of light depends on nothing. It is invariant. Because it is invariant we see the things we see, not the reverse.

At first I thought it was fake but then I went to the Nasa site and saw this animation of the Moon passing in front of the Earth. http://www.nasa.gov/feature/goddard/from-a-million-miles-away-nasa-camera-shows-moon-crossing-face-of-earth And then i thought, if the satellite is always facing the daylight on Earth, it means the sun is behind. And if the sun is behind, doesn't that mean that this is actually a solar eclipse going on?

You are full of contradictions. Take a rest and rethink your answers.

You are speaking of 2 different things. 1. the speed of light: we call light whatever travels at c. This definition is exactly what GR is telling us: SOL does not depend on the source, SOL depends on the observer. I like to compare it to a kind of horizon. It is our observational limit. 2. the phenomenon of light: of course lots of phenomena are occuring without any need to be observed. I guess even phenomena that remain unknown.

So you mean the rocket will travel through "regular space"? IOW , at exactly half-way, the rocket will not be pushed by the creation of space behind it?

Is the motion of a photon described by velocity?

As observed by the earth? Or do you mean as if there was an absolute state of motion? (sarcastic again) ----------------- BTW you may notice that a new notion has been introduced following which the photons have another speed depending on the state of the observer.