michel123456

Yes. Both effects at the same time.

The 2 effects do not cancel each other exactly?

Well I suppose the fire ball appears at much lower speeds. At the moment the air molecules cannot go round the object, something like the link must happen.

Doesn't the link also partly explain what happen in front of a meteorite before hitting the earth?

Oh. That is the answer in SR. The same answer. Fine, very clear, thank you. Does that mean that all the interminable discussions about time dilated orbiting clocks* and other twins should be calculated before getting an answer? *Because it should be obvious that when a clock orbiting the Earth is observed time dilated from us at rest, from the frame of the clock the Earth is time "contracted". It is not a symmetric situation. In a symmetric situation the Earth should be time dilated too, as observed from the clock.

----------------- This is a joke:

Making America great again* *never take me too seriously.

So then, when clocks speed up, what about length? Does that suppose length increase (instead of length contraction)?

Maybe I have to rephrase my question. Aren't length contraction and time dilation always linked together? When time dilation is observed then length contraction must be observed too. And vice versa?

That is not a joke.

So the answer is yes if i understand clearly. Again the answer is yes. So there is more than time dilation, there is also the contrary. In this case, when clocks appear to speed up, is there also a frame that observes the contrary of length contraction? (I had a negative answer on this previously)

Sorry for that. I mean: the contrary of time dilation.

About clocks now. Is there a frame for which, instead of time dilation, time contraction can be observed?

Properties of what? What is the subject of observation? isn't it something there? One single "reality" (how else to describe it). One single tin can with a bunch of properties. Or are there many different "things"? One for each observer. Maybe you don't care. But I do. Then I will go directly to reach the frame of the object, and make the recognition that a tin can is actually a tin can, that a contracted ruler is nothing but a regular ruler, and that reality is pretty much as observed by Newton and Galilei. It is not the projection of anything else, it is not contracted, it is not weird. What some other observer far away may observe as contracted when he looks at me is not part of the things that happen, it is part of the things that appear to happen.

No. See AJB's answer above. post#71 Markus analogy has an object, anyway something is there as the focus point. One object, one single reality. What I see is that different results are obtained from different point of views and that is most natural. None of them describes the object accurately. Maybe GR gives you a mathematical description. 4D. But the world we live in is already 4D. The tin can, the ruler are the way they are. They are not "projections". If they were projections one should imagine that there exist an "expanded tin can" in 4D. There is no such thing. The tin can is already that. Thank you.

So there exist a frame that measures the upper value. The upper bound.

Thank you for the straightforward reply. OK. Is there an upper bound for this length? I mean, we know observers may measure the ruler contracted, but are there observers that will measure the object longer than it is measured in its rest frame?

Thank you. Now, is there another reality than the ruler? I mean, isn't the ruler already a 4D object, that is to say a ruler existing in space-time? Or is it a mystical "projection" of an unimaginable 4D object?

Ah. So the ruler won't change after return. But you believe that length contraction really happens. Don't you?

Thank you for the long post. But then, why does it take so long to make people accept that there is only one reality? Why do scientists insist so much in saying that the oblong rectangle projection or the contracted circular projection are the same "real"? To the point that they believe that they can hold in their hand a can flat as a sheet of paper? This is the weird thing that scientists introduce. Does GR say that? Why do we have to consider what we observe in proper time as "distorted" or as an "illusion". IMHO what we observe in the same frame as the object is the best frame. Undistorted.

Simplicity. It consists in making the statement that reality is a single thing that is observed differently by many observers. It is already the case even without Relativity. And suddenly Relativity is grounded. Relativity is simple. Relativity is comprehensible. I really don't understand the need of the concept of multiple overlapping realities. It makes people think that the observer dictates what reality is (and it is wrong, the observer is passive, not active). It makes people think that weird things do happen when in fact it is only an effect caused by observation. It makes also people think that they can use this effect in order to get a blue cow or a shrinked ruler, as if the ruler had kept inside it a piece of contracted space. As if the internal structure of the ruler had become different from that of a regular ruler. And even worse, the contraction of the ruler depends on the direction of movement as seen by the observer....so guess how will the ruler be contracted. I expected more critical thinking from the physicists.

if C is a frame, it is the best available. And the more you get away from C, the more it gets elusive (bis repetita placent).

So if an ET proclames that Swansont is flat like a piece of paper because his physics say so, it's ok to you? Especially when you go to bed and suddenly the ET measures that you changed format and you are now short like a coin. You yourself Swansont don't know better?

I say there is a better one. For example you want to measure length, proper length is better than anything else. Reality is much much^much more than the sum of all measurements.