[yor_on]

Ah well, as I'm suddenly back to physics I guess I should write about this too. There is a thought experiment called the 'twin paradox'. In it you have one twin staying at home, another accelerating, turning around, coming home to find that him and his twin no longer are of the same biological age.

There are different explanations to why, although in this situation you need to involve a acceleration no matter which one you prefer. Some define it as it is specifically the acceleration creating it, deceleration around f.ex a planet and then accelerating home again. Myself I'm of the opinion that accelerations doesn't matter for it (gaining a time dilation). You can get to time dilation's in relative motions too.

Here's a take on it. https://siderealobserver.wordpress.com/2020/03/08/twin-paradox-feynman-or-mauldin/

and she asks a question at the end of it. I love questions too :), and this is a good one.    " Relativity calculations are necessary for the global positioning system. I’m sure the people who work in this field know exactly how to do the calculations, since GPS works. I would love to see those calculations. "

Well, I don't have those calculations but I have a answer from stack exchange. In which we will have to assume that this guy actually knows what he is taking about, even though Rob doubt it.

"  We are constantly in communication with GPS satellites, which only work because they take into account time dilation due both to special relativity and general relativity. It turns out that special relativity is the larger effect, so I think this would count as hard evidence.

Edit: GPS devices communicate with GPS satellites via microwave signals. The signals are sent from the GPS satellites with a time stamp, and by knowing how fast the speed of light is along with the current time, the device can determine how far it is from each satellite and thus triangulate its location. In order for this to work, the clocks on the GPS satellites obviously need to be synched with clocks here on earth. Thus, the clocks on the satellites were set to run slightly faster when they were built and launched so that when they got into high speed orbit the satellite clocks would run at the same speed as our own clocks. "

https://physics.stackexchange.com/questions/324125/time-dialation-in-uniform-motion
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Actually, assuming it's no intellectual or corporate property my son should be able to produce those calculations. If someone doubt it and want to check for himself.

[yor_on]

Let's take another example. Everything moves in this universe.So can you define a standard for it? Like some definition of a null speed? You can't, you can only define speeds relative some arbitrarily chosen object, as earth, that you then define as being unmoving. There is no golden standard here.  It leads to some unexpected ideas, as in the possibility of everything in a uniform motion being 'still'. It all depends on what you use for defining standing still, earth or the sun, or something entirely different as the CBR. In relativity you have two different definitions. One is called 'relative motion' or 'uniform motion', the other is accelerations (decelerations included)

The first is to all experimental local evidence not moving at all. The only motion you will find is relative something else (ignoring spin), a very good reason to call it 'relative motion'. you need something more to define it from because it's not noticeable by any locally done experiment, as far as I know.

the second, accelerations, Einstein joined as a specific equivalence to gravity. Accelerating gives you a weight. and the weight is something you can prove locally, standing on a scale. So locally defined you only can prove accelerations. Time dilation's doesn't matter for it as I don't expect you to, under any of those circumstances, be able to prove your local proper time slowing down, or getting faster. Locally defined there are no time dilation's. Only your proper time.


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(and specific meaning that you need a constant uniform acceleration at f.ex one gravity to reach a equivalence to the gravity on earth)

[yor_on]

So what about the twin experiment then? Where they differ in age after one twins journey?

[yor_on]

I call it 'global definitions' versus 'local'. Globally defined there is a difference. Locally defined both followed their proper time, and joining the same frame of reference both their wristwatches are synchronized.

[yor_on]

Globally defined the earth is in motion, locally defined it isn't. You need to ignore spin for this though.

[yor_on]

It becomes a very different universe, doesn't it? From what we once thought.

[yor_on]

It's all based on the experiments we can do. Relativity has been proven for a hundred years now, again and again. The same goes for Quantum mechanics, everything we know must be based on experimental proofs. Both are pretty weird.

[yor_on]

The majority of physics don't interpret it my way. To them a time dilation is something real that happens inside what I call a global description of a universe. So they use the interpretation in where you as a bystander can define both time dilation's and speeds for others. Most do not consider it remarkable that there are no experiments proving a motion locally either.

[yor_on]

You have two contenders for what time is, in main stream physics. One called the arrow of time, the other entropy. Myself I have a third, 'c'. Because 'c' is a equivalence to your proper time.

[yor_on]

The point I'm trying to make is that if you go by those experiments you find, then try to avoid too many preconceptions this universe becomes a lot more weird to you.


syntax

[yor_on]

And why that is, is because there is no way for you to define anything other than that your own proper time (wrist watch) always is invariant, of a same pace and duration. Any time dilation defined will be by another party, relative their own definition of their local clock and time.

[yor_on]

And now you will find yourself in something of a conundrum. Because if you do, you do it in the exact same way as when you think you can set 'speeds' for your universe. You use a 'anchor'. That anchor is your own local definition of a clock, 'time'.

[yor_on]

It becomes a even deeper question. Because it ends in a preconception. That your clock is the one showing the 'correct time'. Or if you like, the correct 'pace'.

[yor_on]

So it becomes what I think of as a pretty good question. Either all local clock have a equivalence, and so you can expect this to be a correct way of defining time dilation's. Or they don't, all clocks being of different paces, durations and 'ticks'.

[yor_on]

'c' is 'c', correct?

[yor_on]

And I use 'c' as yours, and mine, clock.

[yor_on]

We call 'c' a constant. To be more correct we should call it a 'local' constant.

[yor_on]

It has the exact same plasticity as your clock does. Locally defined invariant, of a same pace for you, no matter where or when you make a experiment testing its 'speed'.

[yor_on]

There is this example of a 'light clock' that you can observe as it change speeds, seeing it 'ticking'. It slows down to you.

[yor_on]

So does 'c' slow down?