That post was an answer to this post:
I appreciate what you're saying and have said. I agree that in order to critique a subject one needs to have some idea of what it says and why it says it - the foundations of what it says. Otherwise (to use an analogy with building a house that I posted in a different topic) one thinks that other people are proposing that the roof of a house can levitate in the air with no means of support from any lower storeys and foundations. And one naturally mocks them for that proposition because one hasn't bothered to notice the presence of those foundations.Tamminen wrote:To avoid confusion, this is indeed the relativistic Doppler effect, but not time dilation. Time dilation is the same whether those two observers recede or approach if their relative velocity is the same, which can be seen in my geometrical proof a few posts ago. Just turn the triangle upside down. I also suggest that @creation takes a good look at that proof to get an answer to the question of how one can make a 5 year trip in 3 years. Needs some insight into the principle of relativity though. And remember the constancy of light speed.
But my point in that post was to re-iterate, by example, what I said in this post:
A large element of the long, long argument here simply stems from not clearly distinguishing that which is directly observed and that which is logically concluded from those observations. As I said in that post, I suggest it is best to be clear first about simply what is directly observed before discussing possible interpretations of those observations. It is, generally, in the interpretations of those observations that the real philosophy starts. But the raw observations themselves first have to be agreed on and understood by the participants.
I don't understand what you mean by "embarrassing" here. What would look embarrassing to who?But the real twin paradox is that both twins get younger than the other twin whether they are receding or approaching. This may look a bit embarrassing to someone.
When you state "the real twin paradox is that both twins get younger than the other twin whether they are receding or approaching" I'd suggest, in order to avoid people misinterpreting you, that you make it clear how that proposition relates to the observable; i.e. the sense in which it is physically meaningful. This is what I did in the post on the other topic to which I referred in the post to which you have replied. Here's the link again:
As you've said, the interpretation that both observers (e.g. twins) put on their raw observations depends crucially on the experimentally determined fact that they can both regard light as travelling at 3 X 108 ms-1 relative to themselves, despite the fact that they are moving relative to each other; even if their relative velocity is itself close to the speed of light. It is this fact that distinguishes the Relativistic Doppler Effect from the Doppler Effect involving sound with which we're all familiar if we've ever stood near a busy road. The key difference is that sound propagates in a medium (e.g. air) that exists in a reference frame that is independent from any observer. So it travels at different speeds relative to different observers. This has famously been found experimentally to not to be true of light.