Thinking about it, either inversion or turning 180 about the 'lengthwise axis causes reversal of the apparent state. Whether considering top and bottom with motion as described or RHS and LHS with motion as described. The point of that is to show the orientation of motion is not inherent to the electron alone but depends son the observation relationship with it.

3 months later

Einstein Field Equations - for beginners! (On You Tube) 35.12 to 37.20 In one frame of reference alpha is 90 degrees. Cos alpha is 0 and work done is 0. You say that has to be so for all reference frames. I know in this presentation you are just using two dimensions. However space-time is taken to be 4 dimensional in Relativity. There is a time component.That means if alpha is varying with time it could be seen to be different in another reference frame. (The observer seeing the system as it was at a different time, because of his/ her/ its different spacial location.) That different observers can see same events differently is a corner stone of Special relativity. This explanation providing the Tensor which is the same for all reference frames seems to contradict that. Anyone want to defend the video argument?

"if the tensor has a value of 0 in one frames of reference, it must have a value of zero in all frames of reference" ...."And that is why tensors are so important in Einstein's field equations." DrPhysicsA

Maybe for 2 dimensional vector space or Euclidean space, where there is no time difference but the (hidden) assumption that the different reference frames refer to the same time. I don't think that can be reconciled with the fact that General relativity is an attempt to model what happens in space-time.

To be more precise I think I should not mention observers, as this is just transformation from one set of co-ordinates to another (as if different observer viewpoints.) The same argument applies. Also to clarify; by "hidden" I just mean not overtly stated. I don't mean deliberately concealed.

5 days later

An Introduction To Tensors for Students of Physics and Engineering

Joseph C. Kolecki National Aeronautics and Space Administration Glenn Research Center NASA/TM-2002-211716

Tensors are typically defined by their coordinate transformation properties. The transformation properties of tensors can be understood by realizing that the physical quantities they represent

must appear in certain ways to different observers with different points of view.Suppose, for example, that I measure the temperature (°C) at a given point P at a given time. You also measure the temperature (°C) at P at the same time but from a different location that is in motion relative to my location. Would it make any sense if you and I acquired different magnitudes; i.e., if my thermometer measured 25°C and yours measured 125°C? No. We must both obtain the same quantity from our respective measurements.Put another way, suppose that I call my point of view (coordinate system or reference frame) K and yours K*. Let T be the temperature (°C) measured at P in K and T* be the temperature (°C)

measured in K*. We then require T = T*."

Re. previously quoted explanation:The different temperatures are very different as if to emphasize the ludicrous suggestion.

If T at P is not constant, it is not ludicrous that different relationships of the observers to P and each other should result in different values for T at P. Assuming both observers are remote from P and are receiving signals from a probe at P . There is a problem with them both measuring T at P at the same time, as they will not necessarily agree on the time's when. Even if they agree on a time value at which the measurement is read. Also there may be different transmission times of the temp. information as it travels from probe to observer (because of different distance of the observers from the source). Given astronomic distances that time delay difference can be significant.

"at the same time" is problematic. The transmission delay is supplementary. If T is changing at a steady rate, that rate will need to be multiplied by transmission time to give how 'out of date' the reading is when read.

If spacetime is taken as the external to observer's reality, should that supposed reality be applied to the mathematics, as it is within space-time OR should it be treated as if belonging to a platonic realm in which those spacetime considerations do not apply? If they do not apply, how does that affect its usefulness in modelling spacetime? What does "at the same time" mean if there is no time (abstract timeless realm)

Correction . That should say- external to observers reality.

General relativity is attempting to model the outside world. How the outside world is known is still tied to how it is observed or iterated with.

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