[yor_on (OP)]

'It's all about comparison and definition via one 'inertial frame' relative the frame we observe (think Earth and a rocket). And our definition of that 'inertial frame' is arbitrarily made as we have no 'gold standard' for that either, right?'

"If I understand you correctly, not right. As I've said before, there is an easy test to see if you are in an inertial frame. You drop a stone. If it moves away from you then you are accelerating. On Earth we are not in an inertial frame because stones move away from us. Actually, on Earth we are feeling gravity and SR doesn't like to mention gravity."
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What I was thinking is that when in uniform motion you have no definition of your velocity except when relating it to another frame of reference. So looking at it that way it seems to me that there is no absolute definition of the time dilation you might have in that frame other that relative another frame. Still there will be one, if I understands it right?

[yor_on (OP)]

You can also see it as you have a different time dilation, if so, against all other frames you measure your frame against? Which is a very weird idea. That as I don't see how you can define a uniform motion, except relative another frame of reference? And I know that this falls under SR not GR.

[fontwell]

What I was thinking is that when in uniform motion you have no definition of your velocity except when relating it to another frame of reference.

Yes!

So looking at it that way it seems to me that there is no absolute definition of the time dilation you might have in that frame other that relative another frame. Still there will be one, if I understands it right?

Yes! Relativity! It means observations are relative, not absolute. If you look at one moving object you see one time dilation, if you look at another moving object you see another time dilation, if they look at each other they see something else again.

There is equality between any two observers because they each observe each other to have the same dilation (slowness). But there is no gold standard dilation because other observers see both of them as time dilated to him.

Added

You can also see it as you have a different time dilation, if so, against all other frames you measure your frame against? Which is a very weird idea. That as I don't see how you can define a uniform motion, except relative another frame of reference? And I know that this falls under SR not GR.

You test for acceleration by dropping a stone. If it stays next to you you are in an inertial frame.

This is described as 'constant motion' but only with respect to another inertial frame. You always consider you are stationary. Why would you think you are moving? You drop a stone, it stays near to you - you are stationary.

The only thing is, every inertial frame considers that it is stationary too. This is fine because Relativity only concerns itself with relative motion. Relative motion between inertial frames, each one of which appears to be stationary (or not accelerating anyway).

[yor_on (OP)]

If I now was to compare my uniformly moving frame a against an accelerating one (Earth <-> accelerating rocket) then I understand that there is a generalized idea of how to differ between those two frames, by using the idea that motion isn't defined in relation to individual objects, such as our Earth <-> accelerating rocket system, but instead in relation to the distant stars. And yes, I know this one falls under GR, as I understands it.

But if you don't accept this definition then you could expect Earth to be the one aging relative the the accelerating rocket, again, as I understands it? And looking at it generally this one too brings up the question of how to define that time dilation. It seems easier to use your test to me and then say that acceleration, as shown by that stone moving towards its 'gravity well' is what defines the time dilation.

Which brings me back to my first wondering. How can we define the time dilation for an uniformly moving object like our Earth? And now I've given two examples that I believe to be correct? one under SR and one under GR (acceleration).

It do confuse me It would have been simpler with some 'gold standard' that we could define uniform motion against but not even the CBR can do that for us as I understands it?

[yor_on (OP)]

"This is described as 'constant motion' but only with respect to another inertial frame. You always consider you are stationary. Why would you think you are moving? You drop a stone, it stays near to you - you are stationary."

Well, it's there I don't agree. I can leave earth accelerating, when I then stop this acceleration I will be in a free fall. The stone will stay relative me but I know that I've accelerated first. If I now did this with two rockets that now both are in a free fall (uniform motion - coasting:) but firstly been accelerated at different velocities they should then be seen as equivalent? But their time dilation relative their origin (Earth) will differ although they are of the exact same mass and definition otherwise..

And that time dilation would then grow under the years of uniform motion - coasting too but unequally for our rockets versus Earth. And it's there I find it easier to see the acceleration in itself to become the 'time dilation' made by those rockets, but that wouldn't explain how uniform motion also have a hand in it. I hope you can see how I think As for being rude, explaining how one think is never rude, as long as one's not condescending of course. And I don't think you are Mr Fontwell

So to me there is a difference and that definition of the stone staying by your side doesn't cover it.
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[Geezer]

However, the real problem lies in the third sentence. We are absolutely not defining the second using the motion of light. What we are doing is defining the second in terms of atomic events. We are merely using the microwave energy released to detect and count the atomic events.

We absolutely are. The atomic event concerned is the hyperfine transition. We aren't counting hyperfine transitions. That's like counting the number of plucks of the guitar string. We are counting the resultant EM wavepeaks going past. See http://en.wikipedia.org/wiki/Hyperfine_structure#Use_in_defining_the_SI_second_and_meter for more information.

Farsight, you fail to grasp the point, even although you actually stated it correctly.

The events are atomic as you say above (hint - do you think perhaps that's why it's called an "atomic" clock?). Only the method of detection of the atomic events is electromagnetic.

Your notion that atomic clocks measure time based on some characteristic of light is fundamentally wrong and liable to lead to lots of misconceptions and circular logic - QED. Atomic clocks measure time based on characteristics of atoms, not light.

Using your logic I could say that the tree outside my window is not really a tree, it's simply light because I use light to detect its presence.

[yor_on (OP)]

It all falls back on how you define your universe naturally. As a physicist/mathematician you might define the universe as being of two properties, one expressed through General relativity (acceleration) and the other being what happens under Special relativity (uniform motion). A little like we say we have a wave/particle duality.

But to me looking at it those definitions goes into each other, and I have severe difficulties defining where one starts and the other one ends, that as the universe in reality are a seamless experience to me, as to the rest of you too if you think about it.

And to my eyes it either have to make sense as one definition or we will have to start look at our definitions again. By that I do not mean that the theory of relativity is wrong in any way, rather that there should be an explanation that even I could understand. And it's trying to make sense of that definition I get stuck on this kind of things And I agree Mr Fontwell, I do blend GR and SR at times but it all goes back to how I see SpaceTime. As a 'whole', and that's why it at times might take some time to make my questions understandable, I guess )
==

To use another mans word, that physicist I talked with. And this is an GR question.
==

Would it make any difference for the time dilation, relative my point of origin (earth), if I took a second to reach 99% of the speed of light relative taking one year to reach that velocity?

He thought it wouldn't, just guessing there of course as we were just talking.
What do you think?

[fontwell]

Geezer, your ideas about defining length belong in another ATM style thread, not this one.

[fontwell]

yor_on, I think maybe you have such a fixed way of understanding what constitutes position in space that you will never be able to drop it. Unless you can do that you will always be looking at SR from a view point where it makes no sense. And it doesn't make much sense to begin with.

One last try.

For example, you do the stone test and see you are accelerating. Are you slowing down? Are you speeding up? when you stop accelerating are you now going really fast? are you stationary? Did you change direction completely?

There is no independent reference in SR, only many other inertial frames. Depending on which frames you look at, all of these answers can be true. Your relation to these frames is determined by the SR equations and is different for every frame. If this wasn't the case it wouldn't be called relativity.

When I say you will consider yourself stationary it might be a small liberty but it is basically true. Most of the time on Earth you consider yourself to be stationary (assuming you sitting at a desk or whatever and not in a car). Although you know you are travelling round the Sun and round the galaxy core and round the local galaxy cluster centre etc, you mostly think you are sitting in one spot.

Similarly, when you are not accelerating your situation is identical to that of being stationary. Since there is no independent frame of positions, you may as well call it stationary. If you decided to call it constant velocity the question arises, how fast? and in which direction? You cannot ever answer these questions. Except you can if you give them with respect to another inertial frame. But for every inertial frame you might use there is a different answer.

BTW, as you know, these 'fixed' stars are mainly rushing away from you in all directions (well, those in other galaxies).

Added
You mention about SR and GR and how the universe is really one thing so it gets difficult. But as I see it, even though they are related SR and GR explain different effects. When you sail on the sea you are blown by the wind and moved by the tide. These two things both affect you but you probably find it easier to calculate each one separately. SR covers issues purely down to relative velocities, GR covers issues related to mass/gravity.

[fontwell]

Would it make any difference for the time dilation, relative my point of origin (earth), if I took a second to reach 99% of the speed of light relative taking one year to reach that velocity?

Yes. The time dilation depends on how far you have travelled and at what relative velocity. Assume you define the journey as being to a fixed location relative to Earth. If you travel along this path slowly there will be low dilation, if you travel fast there will be a lot. The total dilation will be a function of how much time was spent at every velocity during the journey. Since the quick acceleration means most of the journey is at the highest speed, this will cause the most dilation.


(comment removed - JB)

[Geezer]

Geezer, your ideas about defining length belong in another ATM style thread, not this one.

What do you mean by "length"?

What do you mean by "ATM Style"?

Stylish ATM machines? Asynchronous Transfer Mode? (although I don't think it's too stylish these days.)

[fontwell]

Your posts to

What do you mean by "length"?

What do you mean by "ATM Style"?

Your posts to Farsight in this thread about how to define local time/distance. ATM = Against The Mainstream.

Although, apparently according to mods "Telling people where things belong is a moderator function" , not my function.

What with this and another mod message, I'm outta here.

Bye bye everybody.

[Geezer]

Yikes! Please watch the door doesn't slam your ass on the way out.

BTW - ATM refers to Anything but The Mainstream.

[yor_on (OP)]

Seems I missed something here?
What was it??

As for the the way you see it Mr Fontwell, I do see it.
But to me it doesn't explain the seamlessness. And I'm naturally inquisitive I'm afraid, never stops wondering, and I'm stubborn to a bone I admit. Don't worry though, it's just my nature to have that low imaginative threshold.

It always make me see to many positions to present an idea from. Not always the best thing, makes it hard to trust my own ideas too at times, And then I will argue. But I'm always learning, as we all are here, until I realize why my idea won't work. So me arguing from my position doesn't mean I can't see yours.
But I need to see where I go wrong to know why.
And .

And you're welcome back any time you like, we're not really that bad.
We're not actually, maybe a smite argumentative, some of us.
(Yep, that should be me.)

And we care about all that are here, no matter their level of physics.
I've been on sites where the decision was made that if you couldn't do the math you shouldn't open your mouth. No, they didn't throw me out, crazy as it was?
I threw myself out instead )

So when the mods react, it's because they are good mods, and try to set a good mode for all here. It's not 'personal', and it have nothing to do with your level of knowledge. We being here are quite cool with each other hopefully, just want all to feel that they have something to contribute with, as they do have, no matter where they are in their physics levels:)

Even stubborn, blind, ah, ** like me ) And I will study your loedel-diagram and try to wrap my mind around it, it was a lovely presentation Mr Fontwell. And risking repeating myself, you're welcome back. We all are I hope, the mods are actually the best mods I've seen anywhere.

[yor_on (OP)]

You wrote "BTW, as you know, these 'fixed' stars are mainly rushing away from you in all directions (well, those in other galaxies)."
==

I quite agree Mr Fontwell. The reason I used it in my example was that it is a proposition from serious physicists (I hope?  LSU professor resolves Einstein's twin paradox. 2007 As for my position on this thread Well, I'm learning, nothing more. And I kind'a love that, as I think you might too? And I still think my arguments were good ones?

[yor_on (OP)]

There's another thing confusing me too. I assume that when going near lights speed we will see the universe as 'contracted' any which way we look? Am I right there, that those 'distances' measured will, relative us traveling, shrink equivalently in all directions?

But light will behave differently depending on its vector relative us, won't it? The light 'catching up' to us will be redshifted and the infalling light meeting us as we travel towards it, will be blueshifted. Am I correct there?

So, although I could, if I now f.ex assumed that I was traveling at a constant one G uniformly, and therefore assume that it was equivalent to being on a planet, still observe a unequal distribution of energy, relative my frame of reference?

I know, that's peeking, but it still makes me wonder