Length contraction vs Space time

[Nugatory]

If that were true then the distance to Alpha Centauri (or to the Sun) and the length of Earth's diameter would vary with how you measure it. However, in fact astronomy and Earth science have determined those distances and that length very precisely. The actual distance between stars (astronomically speaking) does not change with all possible varieties of measurement frames, nor does the nearly spherical shape of earth.

Now you are misunderstanding what proper length is. It is the length that would be measured in a frame in which both ends of the object are at rest, but it is no more "actual" or "real" than the length measured in any other frame. It's tempting to to dismiss the contracted lengths as less real or even some sort of illusion - but before you succumb to that temptation you should work carefully through Bell's spaceship paradox and Purcell's derivation of magnetic forces.

 

[ebos]

My 2 cents would add that there are levels of reality (measurement) which are "good enough" for what we are measuring at the moment. I would certainly agree that there is really no such thing as precise measurement. But there is measurement that is 'good enough' for our purposes at the moment we need them. Like I wouldn't need to know anything about quantum distances if I was sending a payload to the ISS. There are measurements available that are good enough. More than good enough, actually, because out standards are usually double or triple what we really need for accuracy or safety. But I wouldn't use my metre-stick (just doesn't sound as good as yard-stick) to measure the wavelength of a red light, or whatever. That's why it's called 'relativity' I guess.
It's also got to do a bit with attitude. For example some of us are just more subjective than we are objective (I find engineers tend to be more objective, but that's me). Then, of course, we start to approach uncomfortable areas like, dare I say it, meta-physics.
Jump in anytime to correct me, folks. Have a good one.

 

[phinds]

My 2 cents would add that there are levels of reality (measurement) which are "good enough" for what we are measuring at the moment. I would certainly agree that there is really no such thing as precise measurement. But there is measurement that is 'good enough' for our purposes at the moment we need them. Like I wouldn't need to know anything about quantum distances if I was sending a payload to the ISS. There are measurements available that are good enough. More than good enough, actually, because out standards are usually double or triple what we really need for accuracy or safety. But I wouldn't use my metre-stick (just doesn't sound as good as yard-stick) to measure the wavelength of a red light, or whatever. That's why it's called 'relativity' I guess.
It's also got to do a bit with attitude. For example some of us are just more subjective than we are objective (I find engineers tend to be more objective, but that's me). Then, of course, we start to approach uncomfortable areas like, dare I say it, meta-physics.
Jump in anytime to correct me, folks. Have a good one.

I think you are misunderstanding the entire topic of this thread, which has nothing to do with the accuracy of measurements but rather the differences in what is seen from different frames of reference.

That is, your post is perfectly reasonable, it's just completely irrelevant to the topic at hand.

 

[ebos]

I think you are misunderstanding the entire topic of this thread, which has nothing to do with the accuracy of measurements but rather the differences in what is seen from different frames of reference.

That is, your post is perfectly reasonable, it's just completely irrelevant to the topic at hand.

Yeah, well I thought it looked pretty easy, peasy. Must be that new BP med.

 

[ebos]

My head always tries to go to the practical end, because that's how I understand stuff, and I think I was trying to give an example to the OP that they might understand too. However, I may have got off track.
Like now: Those damn meds! Hate getting old.
Anyways, thanks for being so 'nice'. Hope that doesn't that make you cringe? Because I do like the 'new' phinds. Don't ever feel you need to modify your replies to me. OK, let's quickly get back to physics and/or football.