Talk:Spacetime/Archive 22

Opinion on figure change?

In figure 3-7, I added little icons illustrating what the observer "sees" in terms of redshift or blueshift. Are these little icons helpful, or do they make the diagram too busy? Prokaryotic Caspase Homolog (talk) 08:21, 28 September 2018 (UTC)

Yes, they are very helpful because they have been stolen from my diagram. I know how to make diagrams clear and simple. However, the icons are too small. Could you please to make it a bit larger? I am going to use your diagram against spacetime concept and relativity in Einstein's incarnation, so that would be fine for my readers to make it easy to understand visually. That will be not a problem to explain them, that observer should move himself and displacement of the source is due to aberration, exactly as in the case of rotation. Could you also please to add the diagram into the section Transverse Doppler Effect in the article Relativistic Doppler effect? It lacks one. Yours most sincerely, Albert Gartinger (talk) 08:49, 28 September 2018 (UTC)

Why do you use such words as "steal"? I told you earlier that that was an aspect of your version of the illustration that I personally thought was rather nice. However, your figure was a JPG figure and did not scale well to different sizes. It looked somewhat "jaggy" to my eyes. You should learn to make SVG images.

I asked about this figure because I do not consider my opinion to be the only opinion, and if the majority indicate that they think that the image is too "busy" and that it should be reverted to the simpler earlier version, then I will do so.

I will have to look at the article Relativistic Doppler effect to see if this diagram fits in with its presentation. I wouldn't want to rewrite the article to accommodate the figure. Rather, I would want any figure I add to enhance what is already there.

Instead of enlarging the icon, I enlarged the entire figure. Does that work? Prokaryotic Caspase Homolog (talk) 09:26, 28 September 2018 (UTC)

Please be sure to check how it looks on mobile devices as well. Around 40% of our viewers are accessing this article on cell phones and tablets. Prokaryotic Caspase Homolog (talk) 09:31, 28 September 2018 (UTC)

I think we can also place a question at https://physics.stackexchange.com/ which diagram is better, yours or mine. It has hundreds, if not thousands readers. They can also have a look at this polemics. Sadly, I am too busy today and must leave Albert Gartinger (talk) 09:38, 28 September 2018 (UTC) SVG! That's good idea, thank you. I have missed it. Albert Gartinger (talk) 09:45, 28 September 2018 (UTC)

My question is not whether the current Fig. 3-7 is better than Olego_18_09.jpg, but whether the current Fig. 3-7 is better than this earlier version. As I indicated before, Olego_18_09.jpg is unacceptable because it implies that the fundamental distinction between the scenarios discussed in the text is between a moving observer versus a moving source. Rather, the distinction between the scenarios is between the source and receiver being at their geometrically closest approach, versus the receiver seeing the source as being at its closest point. Prokaryotic Caspase Homolog (talk) 15:44, 28 September 2018 (UTC)

Fig. 3-7 does not mesh well with the discussion at Relativistic Doppler effect Prokaryotic Caspase Homolog (talk) 21:06, 28 September 2018 (UTC)

Let me put it to you this way: Suppose observers A and B, moving towards each other in uniform inertial motion along non-intersecting paths, are at their closest approach with respect to each other. The events marking A's and B's points of closest approach are independent of frame. Both A and B are carrying identical monochromatic light sources. A and B both see light from the other's source as being blueshifted relative to his/her own.

1. If we consider A as being a moving observer, as in Olego-a, then blueshift [added later: "has a significant component"] due to aberration of light. A sees B as apparently not yet having reached the point of closest approach, and A's motion relative to B has a significant longitudinal component.
2. If we consider A as being a stationary observer, as seemingly depicted in Olego-b, then blueshift [added later: "has a significant component"] due to light-time correction. A receives light from when B had not yet reached the point of closest approach, and B's motion at that time had a significant longitudinal component relative to A.
3. You could say, "No, no, NO!!! Olego-b is supposed to be depicting the situation where A sees B as being closest to it, when it is actually not! That is why I've drawn the perpendicular image of B as a hollow star, and the displaced image of B as solid and to the right! You're being silly and stupid!!!"
4. Well, suppose I'm a naive student seeing your figure for the first time. How am I supposed to figure all of that out?
5. Actually, receiver moving and source stationary versus receiver stationary and source moving have the same effect, although they are analyzed differently, as seen here.

Prokaryotic Caspase Homolog (talk)

Your interpretation of Case 1 is incorrect. If we think in terms of transverse doppler effect, aberration or light time correction cannot have any effect on frequency shift. Only dilation of observer's or source's clock contribute into the frequency shift, if we think in terms of that frame, in which the effect is transverse.

Theoretically, the observer can always know the actual direction to the source, because there is no aberration of forces. http://www.mathpages.com/home/kmath562/kmath562.htm

It's hard for me to understand if you are serious. This is an elementary problem! The result of the measuremen depends on how you conduct it, that is, on what you think about your movement. Let's think within the framework of the transverse effect, it means that YOU move in the frame of the source and at the moment of reception the source is at closest approach to you. If you consider yourself moving, then at this moment you keep your head or telescope forward in the direction of movement. The angle of inclination corresponds to the speed that you attributed to youself (the angle of relativistic aberration). The frequency of the source becomes gamma times more blue. You treat this phenomenon as slowing down your own clock, so the clock at rest is ticking faster. It is the same explanation for the both rotational and inertial motion. This is a purely Transverse effect.

I have already written, that this is a question of interpretation. Of course, the same effect can be attributed to the presence of the longitudinal component, should you think that you are at rest. But we are talking about the transverse effect and the chapter is about transverse effect. https://www.researchgate.net/publication/304792446_The_Problem_of_Slow-witted_Aliens_or_The_Transverse_Doppler_Effect_Simply_Explained Albert Gartinger (talk) 12:35, 29 September 2018 (UTC)

It is no wonder that your drawing is so confusing! Anyway, Talk pages are not for general discussion of a subject, but are specifically for discussing matters having to do with improvement of the associated article. Your drawing will not appear in this article. Prokaryotic Caspase Homolog (talk) 12:56, 29 September 2018 (UTC)

I note that I did not quite express myself properly, so I added [added later: "has a significant component"] to my original remarks. If one wants to work things out from the standpoint of the receiver, then whether the receiver considers himself to be moving or stationary, he/she has to take into account a component of longitudinal motion. That makes the analysis more difficult than analysis from the frame of the source. Prokaryotic Caspase Homolog (talk) 13:14, 29 September 2018 (UTC)

B, as the light source, has a trivially simple view of the system compared with A, considered as the receiver.

1. B knows, from the conditions of the problem, that A is at its closest point to him.
2. That means that A has no longitudinal component of motion to complicate the analysis.
3. A's clocks are time-dilated relative to B.
4. The light that A receives is therefore blue-shifted by a factor of gamma. End of story.

Prokaryotic Caspase Homolog (talk) 03:46, 30 September 2018 (UTC)

This is exactly what I have pictured on my diagram. This is a purely transverse effect, as it should be. My diagram shows a transverse effect for both cases, frames of the receiver and frame of the source. Your diagram depicts transverse effect in the frame of the receiver and longitudinal in the frame of the receiver. It is not good, to say the least.

The existing in the article explanation in frame B is nowhere suitable. One might think that the change in frequency measured by the spectroscope is due to what B observes. It is very confusing, that the source highlights the receiver by green monochromatic light and in the meantime by violet radiation . It's unclear how an electric light bulb can observe something. It simply shines. Well, and if the source went to sleep?

Everything is simple. Detector's clock slows down, so processes around him run faster, radiation turns violet. Albert Gartinger (talk) 06:28, 30 September 2018 (UTC)

According to the receiver, there is no longitudinal component either, if the receiver considers himself moving. The co-moving with the receiver observer understands, that actually path of the photon is perpendicular to his path. He understands, that displacement of the source is apparent effect, a.k.a aberration of light. Albert Gartinger (talk) 08:01, 30 September 2018 (UTC)

Think about transversely moving mirror. The mirror is a moving observer. A source (laser pointer) in the origin emits green monochromatic light straight up. The light approaches the mirror at relativistic aberration angle. At the reception, when the source crosses Y axis, the light blueshifts, since mirror’s clock runs slower. The mirror reflects the light backward at the same angle as It had once arrived, it travels back into the origin.

Now the mirror turns into is moving source. Since it move in the frame of the laser pointer, its clock dilates, so the light redshifts again and comes back into the origin at the same green color.

There is no even smell of "A is slower than B, B is slower than A" Albert Gartinger (talk) 08:11, 30 September 2018 (UTC)

Another important point about your diagram A. Why did you draw a slanted beam? The ray, as constructed from individual photons, does not undergo aberration. It remains perpendicular in any frame, either "moving" or "stationary". The moving detector crosses the ray and a single light pulse appears coming from the front. But the whole RAY remains at right angle direction of motion of the receiver or the source.

Albert Gartinger (talk) 13:23, 30 September 2018 (UTC)

The beam is drawn slanted because that is the direction from which in which the receiver views the light as coming from. In other words, the arrow is coming from the apparent position of the source.

The scenario where source and receiver are geometrically at their closest approach to each other, as depicted in your Olego-a, is confusing because

1. You illustrate, correctly, that from the viewpoint of the moving observer, the source appears in an abberated position in the sky.
2. On the other hand, you illustrate that from the viewpoint of source, its light travels on a direct perpendicular path towards the observer.
3. You illustrate two different frames in a single scenario. This is confusing.
4. A consistent illustration from the frame of the would be the "Moving Observer" of this figure.
5. Analysis of the "Moving Observer" of this figure is more complicated than it should be.

a. It doesn't matter who is considered as being "actually" in motion, the source is time-dilated relative to the observer. This would result in a redshift.

b. On the other hand, since there is a longitudinal component of the observer's motions with respect to the aberrated (apparent) position of the source, the light that the observer receives from this apparent source would be blueshifted.

c. The overall effect (redshift? blueshift?) depends on the relative magnitude of (1) time dilation in the source versus (2) blueshift as the observer approaches the apparent source.

Does it make sense why I consider your Olego-a unsatisfactory? Prokaryotic Caspase Homolog (talk) 14:16, 30 September 2018 (UTC)