Time is by definition universal.
Well you use whatever language you want but if you are trying to “prove” anything to anyone - you might want to consider using their language - not yours.
You very obviously have no idea of what is being discussed.
Show me that definition.
They are trying to justify the slowing of physical change (and their clock) as proof that time slows down the faster you travel.
Time does not slow down the faster you travel, the physical process change rate, but that is not time. Time is not a physical process, time is simply duration.
I am not concerned with how much physical change occurred to their watch or body (or cat), I am concerned about the duration of time they traveled. If their clock slows down the faster they go, great, but that does not change the duration of time they were gone.
A light year is measured by the Earth making 1 lap around the Sun while observing the distance light travels during that duration of time. Anyone in the universe is free to observe Earth make a lap while measuring light travel distance during that duration of time. They can call it what they want to, but people of Earth call it “light year.” That distance and time is universal, as the duration of time for Earth to go around the Sun is the same for everyone, and the distance that light traveled during that duration of time is the same for everyone.
It is a universal standard than anyone can measure.
Please show!
Clocks do not move slower. Local time at speed is different from the perspective of the observer on earth, but clocks will appear to go at the same speed as they ever did.
Thus when the astronauts return to earth, and everyone they knew is already dead, they themselves have not felt the time any differently. THey will be as older as the local time they have experienced. But the distance travelled will be the same from their perspective as it is from the observers perspective.
THis is eaxclt where you are wrong.
The earth will be 20 years older but you will not be.
I can’t do that because it would require quite a bit of time from me. Among other things, I’d have to understand what kind of definition you’re looking for. That might take some time. Perhaps you should look into James’s concept of “absolute time”? But I am not sure it matches what I think is the standard concept of time. Some of his concepts (e.g. that of time and existence) deviate from the standard ones (for whatever reasons), so it’s not something I can expect from him.
But even if I provided you with a satisfying definition, I’d still have to prove to you that it’s the standard definition, right?
My age depends on how many laps the Earth has made around the Sun. If I leave on a journey at the age of 57 years old, and the Earth makes 20 laps around the Sun while I am gone, then I am 77 years old when I return, because the Earth made 77 laps since I was born.
If I look 20 years younger when I return, all the better, but I am still 77 years old.
You are confusing the rate at which objects change with the duration of time that change occurs. The same goes for clocks. If a clock reads 57 years when it leaves Earth, and returns when the Earth has made 20 more laps around the Sun, then the clock is 77 years old. If it shows it’s only 65 years old, then it is wrong! It went out of synch with the Earth clock.
_
So MD is saying… regardless of all else, that we can gauge non-conventional travel in relation to our Solar System, so our solar system becomes an intergalactic clock… as opposed to a… clock. The Milky Way could also serve as a universal measure of time for farther-afield traverses.
I said: “Time is an experience”, and any experiences have to be gauged/measured, on a scale on par with the experience, no?
_
Did not Galileo surmise similar?
That is simple math.
It has nothing to do with whether clocks actually slow or not.
IF the clocks slow yet the speed records the same - the math requires that the distance must also shorten.
I’m sure that is not true. The simple obvious thought is that if a clock is traveling at the speed of light - the hands on the clock could not possibly move. So the issue becomes one of how much speed is required to slow those hands down and by how much. And that is what the relative time and velocity equations are about -
(t_1 = \frac{t_0}{\sqrt{1-\frac{v^2}{c^2}}})
The clock hand must move slower (from the perspective of the Earth bound) else the clock hands would be moving faster than light. And what is true for the clock hands - is true for all movement aboard the ship.
I didn’t ask for a “standard definition” (I doubt there is one). I asked for the definition that says that time is universal.
James’ definition is one that I accepted years ago -
[list]Time = the measure of relative change[/list:u]
Because I can’t see when that would ever be wrong and it fits with all of the science discussions about time.
The issue being discussed is that - the measure of relative change (“time”) - itself changes due to acceleration away from a prior position - clocks actually move slower from the perspective of those who did not accelerate away from the origin.
The origin always changes.
Then sculptor writes to me!
Alright man. Answer this fucking post if you’re so smart!
Pretty much.
When the Einstein Online article says that the stay-at-home twin has aged by 30 years, they are using the standard definition of the word “year” and are thereby saying that the stay-at-home twin has aged by 30 revolutions of the Earth.
However, when they say that the travelling twin has aged by 2 years, they are changing the definition of the word “year”, without notifying anyone, to mean something else. This something else is “spaceship year” or 63,115,200 “spaceship seconds” where “spaceship second” means the amount of time it takes for the sweep hand on the spaceship clock (that was previously synchronized with the Earth clock back when it was on Earth) to move 6 degrees.
The problem is that one “spaceship year” is not the same amount of time as one year – precisely because the spaceship clock is operating at a slower rate (in other words, it’s not really synchornized, despite the attempts.)
Thus, what they are doing is using two different units of time (years and “spaceship years”) while acting as if they are using one and the same unit of time.
I’ll articulate my point borrowing and innovating Zeno (who I think is one of the best thinkers ever).
If you’re halfway to 42 light years at c, that halfway is the new origin. Can you dispute that? No you can’t.
So you have to account for an infinite number of origins.
How do you choose one?
This is me getting pissed off at sculptor for calling me shit.
Exactly right.
The real problem arises when they go on to claim that a journey of a distance of 42 light years (Earth years time of light travel), at a speed of .99c (Earth distance/Earth time) only took 6 years (spaceship years).
So the distance of travel is Earth distance, the speed of travel is Earth distance/Earth time, but yet their spaceship clock reads 6 years to make the trip.
It is precisely why I asked pood how many meter sticks laid end to end is that distance, and he didn’t answer. He recognizes the whole thing as total nonsense, but fails to admit it. He knows, that’s why he doesn’t answer the question.
And so the cascade of nonsense continues from MD and now also from Magnus who has already stated, basically, that he won’t learn about special relativity because he doesn’t think it’s necessary for him to learn postulates one and two of SR that form the basis of the whole thing! It’s like saying he wants to learn math but has no use for arithmetic! Incredible!
And then he blames me for not explaining what he refuses to learn. Double incredible!
And yet, dollars to doughnuts, both MD and Magnus own a cellphone with a GPS tracking system.
And do you know what? That GPS system is delicately engineered to work in accord with BOTH the special theory of relativity AND the general theory of relativity! If those theories were wrong, the GPS tracking devices WOULD NOT WORK! But they DO work, and they work BECAUSE they are adapted to both SR and GR!
Their ignorance of their own technology that they take for granted is laughable. And so I do laugh! —> 
The GPS connects to satellites with atomic clocks orbiting the earth. In order to function properly, they must take into account relativistic time dilation — the fact that the satellite clocks tick slower relative to earth clocks.
But wait! There’s more, which this thread had not even addressed yet! The “more” is GENERAL relativity. (Until now we have been “discussing,” if that is how you want to put it, SPECIAL relativity only — i.e. relativity in flat, or non-Minkowski, spacetime, excluding GRAVITY.)
As GENERAL relativity shows, clocks also tick slower in GRAVITY WELLS.
And lo and behold, the time dilation of your cellphone clock in the gravity well of the ground state of the earth more than cancels out the time dilation factor of the satellite moving relative to the earth, such that the satellite clock is actually ticking FASTER than ground clocks by 38 microseconds per day!
For your cellphone GPS to work, it must be delicately engineered to take into account BOTH time dilation on a satellite moving relative to the earth, AND time dilation caused by the gravity well of the earth itself. All of this is done to make sure your GPS tracking device on your cellphone works — just so you can efficiently meet up with a friend to rant and rave at him that relativity theory is false and Einstein is an idiot!
Pood, I agree with you.
Philosophically however, these are not ToE’’s.
Just like Newtonian physics wasn’t a ToE.
They work “well enough”
pood,
You forgot to tell everyone that the GPS system won’t maintain accuracy on its own, it has to be CONSTANTLY UPDATED on a daily basis.
You forgot to tell everyone that if you keep going North you end up going South.
You forgot to tell everyone that a relative velocity of 10 m/s is actually a closing speed.
You forgot to tell everyone that you have no definition for at rest, even though you assume “at rest” all the time.
You forgot to tell everyone that your ship never moves, it’s every other object in the universe that moves, but not your ship!
LOL
Put that theory in the trash where it belongs, before a child gets their hands on it!
“You can lead a mathematician to knowledge but you can’t make him think!”
Alright MD.
The lowest constant we know is the Plank unit.
We’re always trying to find the better constant.
Can you fault us for that? Do these theories make us give up forever on constants? If they do, we give up on the constants that reveal sr and gr.
Then where do we go?
_
The solution is easily solvable…