Relativity, a theory of information?

faen

I suppose I am trying to get an idea of what space really is. Assuming that one frame is the "right one" makes it possible to imagine an existing mathematical construct of space. Otherwise I really can't think of any mathematical construct of space which is consistent with that all the relativistic "predictions" are true for all frames of references. At least not if I don't believe in relativity of simultaneity.

No not that alone. I guess it's for the reason mentioned above, and sceptisism towards relativity of simultaneity.

Measurements are evaluated subjectively. Even sight. Thus they are not objective existence. Also the measurements themselves are different events from those measured.

ghwellsjr

In your first post, you said that "Observer A sees two lightening bolts strike the train at both sides simultaneously". I took that literally as an objective truth. Now you are saying that I was misled, that I should have taken it subjectively, but that just makes it impossible for me to have any idea what you meant. If we can't trust our measurements, then there is no hope of making any sense out of anything. With this level of skepticism, I wonder why you even consider such a thing as an absolute frame or why you are even "trying to get an idea of what space really is".

faen

Maybe it was misleading that I said that it is subjective. I do still consider it as information related to the objective caused "somewhere" by objective reality, most likely by determined by the current models/theories we have. Perhaps it's just best to pretend that I didn't say anything about subjective in case it causes any confusion, sorry..

When it comes to the lightening bolts they were measured by the frame of reference to strike simultaneously, but whether they truly did or not is still unknown to me, since perhaps it did not to an absolute/real frame of reference..

Austin0

Here you have it in a nutshell. Because whether they truly did or not is unknown to everybody That was Einsteins brilliant recognition. Just like absolute motion there is simply no means of determination.
The best we get is the purely operational simultaneity of clocks reading the same proper time in a frame, which makes physics work fine, but tells no truth about actual or absolute simultaneity.
I also think there is an objective reality but sadly we can't seem to access it's truth and must make do with only "information". Relative measurements and theories.

ghwellsjr

OK, so let's agree that any observation or any measurement is objective as far as the data collected is concerned but any extrapolation of that data to what is happening at another location and/or time is subjective--at least that's what I think you are saying.

So when you say that "Observer A sees two lightening bolts strike the train at both sides simultaneously" we take that to be an objective truth because the light from those two bolts arrived at his eyes at the same time but that doesn't mean that the bolts actually occurred at the same time at both sides of the train and to draw that conclusion would be subjective--agreed?

Now let's not be concerned about these subjective aspects but only focus on the objective aspects. What we need is a theory to allow us to make predictions about what different observers will objectively see and measure at different times and when they are not all located at the same place. If a theory can do that, even if the subjective aspects vary all over the place, wouldn't that be a valuable theory?

faen

Yes, I agree with these two posts. The theory of relativity is a valuable theory which makes the correct predictions. However as with all theories, it is only a model of the "real" reality.

ghwellsjr

Well, since you agree that only actual observations and measurements are objective, and extrapolations are subjective, then doesn't that make your idea of a "real" reality subjective?

Here are three more quotes of yours that express the same idea:
What objective observation or measurement can you make in support of these ideas?

I would suggest that you carefully re-read and study DaleSpam's post #8 and see if it now makes more sense to you.

bahamagreen

Once you start down the path of comparing observations, models, and reality, you eventually find that all notions of reality are conceptual models.

And if you look closely it gets weird fast. One might believe that the visual image they see is not the reality but some kind of model analogous of that reality, but at least spatially and geometrically it must correspond...
But what happens to that correspondence when you come to notice that the image on the retina is reversed left to right and top to bottom? And that the optic nerve connections to the rods and cones are not made behind the retina, but from the front surface (this is why the retina has a blind spot where the connections pass through it)? And that the part of the brain that processes this information is on the back surface of the brain?
It's even more complicated because the pairs of left and right halves of the two retinae are connected separately and crossed through the optic chiasma serving as the splitting station, then mapped to six layers alternating left and right in a subsequent pair of nuclei to extract spatial information...
And much more... the movement, color, and shape of a single visual object are processed in three different parts of the brain...

This system works very well; we drive cars, play sports, and manage to get around fine, but please rest assured that what you think you see is quite removed from "reality". The dependence of science on instruments and measurements is the history of untangling our naive misconceptions of reality and substituting coherent models, strange as they may seem.

yuiop

Take the classic Einstein train example as mentioned in the OP but this time the lightning strike hits the back (Event B) slightly before the strike at the front (Event F) in the reference frame of A who is at rest with the track. He sees light arrive from the back before light arrives from the front. In the reference frame of B who is on board the train and at the centre, light arrives from the front flash before light arrives from the back (If the train is going fast enough) so he concludes that Event F occurred before Event B. (Opposite sequence of events). That is a clear example that the sequence of events depends on the frame of reference. Note also that the sequence in which data is received is also frame dependent.

ghwellsjr

The OP did not use any frames in his description of his scenario nor did he mention any remote events. He didn't even say any observers were at the centre of anything. He didn't say this was Einstein's classic train example. None of that is relevant to this discussion. He was talking about what each observer actually sees for himself and what each observer sees that the other observer sees. He does not believe in relativity of simultaneity so he isn't concerned about whether remote events are simultaneous in different frames.

But, to address your concern, of course if you change the scenario, then the observers will see something different than what they saw in the original scenario. That's not the question. The question is for any given scenario, do different Frames of Reference change anything about what each observers sees and measures? In your new scenario, you said the ground observer "sees light arrive from the back before light arrives from the front" and for the train observer "light arrives from the front flash before light arrives from the back." Then you concluded by saying, "the sequence in which data is received is also frame dependent" but you have not shown how this is true because it isn't true. All frames will agree with your two quoted statements about the sequence in which each observer receives the light.

yuiop

Your question was not very clear but I see what you are getting at now.
In the scenario I gave:

1)Observer A sees event B before event F.
2)Observer B sees event B after event F.

All (reasonable, intelligent, rational, honest, informed, cogent, sane, sober) observers agree that the above two statements are true.

faen

Yes theories are subjective. However if we were to learn about the reality in more fundamental terms, it could turn out that an absolute frame of reference is a more symmetric describtion with what is "real". At least I was interrested in if it could be a possibility.

I am not disbelieving in any measurements though. I am aware of that all my beliefs about reality are based on some kind of measurement.

ghwellsjr

After more than a century of intense searching, there doesn't appear to be any hope that an absolute frame of reference could be objectively determined.

Now the question is: are you interested in learning Special Relativity or do you already understand it but just don't believe it?

faen

I am interested in the theory in general and learning more about it wherever I can. I believe I understand the basic concepts. I am open for the possibility of relativity of simultaneity, but I am sceptic towards it as well. As of now, if I would have to make a bet, I would put my money on that relativity of simultaneity is not true.

ghwellsjr

Relativity of simultaneity is one of the basic concepts of Special Relativity. Is it one that you believe you understand? Or do you think you need to learn more about it? Either way, can you summarize what you believe it means?

faen

If you have two different frame of references, A and B. Events which are simultanous in A, exists as not simultaneous to B. That's what I'm skeptic about..

However, that they both predict that the events in the other frame are not simultaneous makes sense, and that is true.

ghwellsjr

What is meant by "event"?