Why in the world would Einstein suggest....

I've only said it about a hundred times in simple form. Once again, it is a contradiction to make BOTH of these claims, which relativists do:

1. You can never tell who's moving

2. I know that it is the moving twin's clock which runs slower.

If I send a clock into orbit, a la a GPS clock, and note that, when it comes back, it has recorded less passage of time, then MY OWN THEORY (if I'm a relativist) tells me which one was moving.

The question is not "meaningless" and my own theory SAYS it isn't meaningless.

The "you can never tell who's moving" proposition is not, and never was, a part of the mathematics of SR. In fact, the math gives you the formula for determining who is moving, relative to another.

That part is a philosophical add-on implanted by positivists. It is a philosophical claim, not a scientific one. It also contradicts the mathematical tenets of the theory itself.

Time-keeping devices have become so sophisticated and precise that they can now record a time difference between a clock on the ground and one moving in a car at 35 mph.

This is an observable, measurable difference. It also, according to the theory's terms, tells you which clock it moving. It is the one which run slower (as the one in the car does).

So why would anyone who subscribes to SR claim that "you can't tell who's moving?"

Truth be told, Fresco, I'm amazed that someone cannot see an obvious inconsistency when it is repeatedly pointed out to them.

If I first said: "It is the middle of the day where I am right now," and then, in the next instant, said "It is the middle of the night where I am right now," then surely you would say:

"Wait a minute, there's an inconsistency in what you're saying," wouldn't you? Maybe not.

A guy in the car going 35 mph could insist, and scream until doomsday, that it is the ground clock which "must" be running slower. Good luck with that, though.

Scream as he might, his clock will still record a lesser passage of time than the ground clock.

Why? Because, regardless of his ignorant denials, he is the one moving, not the clock on the ground.

Forget about speedos and other visual clues
How does the guy know he is going at 35 mph ?

The whole point about GR as opposed to your SR example is that participants start with a common reference frame, and then one participant accelerates. That common reference frame allows for initially synchronized clocks, All arguments about differential aging stem from that synchronization (captured by the word "twin") If there is no possibility of a common reference frame then time dilation is meaningless.. Clocks that "appear" to be running slower "are" running slower as far as separate SR observers know. If they never meet, appearance is all they can ever expect.

I am no physicist but I suggest your handle "layman" is particularly appropriate.

I said:


But the thing is, Einstein's strict mandates aside, no sensible person would deny that they are moving.

Only relativists try to deny this, but only by way of lip service to their creed. They don't believe it, in practice.

Who tells their kids that when they think they are walking home from school at a steady clip, they are actually motionless and the house is coming to them?

There are whole shelves in the philosophy section dealing with epistemology (theories of knowledge), readers of which would doubled over with laughter at your phrase "sensible person".
.
Don't give up the day job !

Spoken like a true positivist, Fresco.

Clocks don't "appear" to be running slow, to begin with. That is simply an assumption (not an observation) with is mandated by SR. (Spare me the "light clock illustrations," those "appearances" are simply deductions, based on unproven premises, not "observations).

They guy in the car can see both clocks, at least for a while. The clock on the ground "appears" to be running faster (not slower) to guy in the car, because, guess what? It IS running faster.

Whoda thunk.

Heh, now you want to get wise, eh, Fresco.? As if only YOU knows what epistemology is.

Don't give up being a pseudo-intellectual spouting vague phrases and making unsupported assertions of fact. It's kinda cute, ya know?

Completely wrong, sorry.



Then I guess you would conclude that the entire theory of special relativity is "meaningless" (the favorite word of positivists), eh? SR makes predictions about time dilation, among other things, which it says will be true EVEN IF there is no way to directly and empirically verify those predictions. It does NOT say that it's predictions are meaningless without a "common reference frame." The whole point of the theory is make predictions about reference frames which are not "in common."

SR works something like this:

If you spot an object that is moving relative to you, here's what you do:

1. Insist that YOU are not moving---that means he has to be moving.
2. Remember that the Lorentz transformations tell us that moving clocks run slower, so...
3. Conclude that his clock is running slower.

But what if you ARE moving, like the guy on the train. What happens to the whole theory then?

It falls apart, that's what.

If I'm a guy on a train, and I have the audacity (from the relativists viewpoint) to acknowledge that I am moving and you are not (if you happen to be standing by the tracks, on the ground), then suddenly, the speed of light is not isotropic for me. I then agree with you that simultaneity is absolute, not relative, etc.

Good game !If you feel inclined, you might like to read up on my 13-year posting history about "reality" and "facticity".

You are "correct" about scientific models being about prediction and control of what we call "the world". Whether we can say they are about "anything else" is a matter for the "realist/anti-realist" debate, which I conclude with Rorty is futile.

Thank you for the discussion.

A while back I saw a clip on youtube where Hafing and Keating were onboard an airplane, with a digital clock. Throughout their flight, they kept announcing how much slower their clock was then running compared to the clock on earth that they had left. For example, "we are now showing .00003 seconds less time elapsed than the earth clock is showing.."

When they finally ended their trip, and held up their clock to the stationary clock, they were right on the money. Less time had elapsed on their clock by the exact amount they predicted.

Needless to say they did NOT presume that they were motionless and that the earth was moving below them. If they had done that, their predictions would have been entirely wrong. They (correctly) assumed that they were the ones moving, relative to the earth.

You forgot to include a very significant line from that clip...
"Before the trip both clocks were synchronized with a central clock (on the ground)" ...i.e. they started from the same reference frame. After the trip the airborne clock was out of sync as predicted by Einstein but the ground clock was still in sync (since it had not left the central clock reference frame).
...But I realize I am flogging a dead horse. Have fun !

What is so "very significant" about that?

And why is it, I wonder, that you never respond to the substance of what I post?

Kind of a long way to say it (the ground clock) didn't move (while the airborne clock did), isn't it Fresco?

Oh, wait, I forgot. The issue of which clock is moving is irrelevant, totally indiscernible, and "meaningless," right?

My bad.

Given what we've been discussing, the "significant" questions here, as I see it, are these:

1. Why didn't Hafing an Keating "see" the earth's clock as running slower? They were, after all, cruising at a uniform speed.

2. If they had "seen" it this way (as you have insisted they should have) why would the clocks themselves have proven them wrong upon landing?

http://www.einstein-online.info/spotlights/Twins
http://www.einstein-online.info/spotlights/TwinsRoad

http://www.einstein-online.info/spotlights/dialectic

Is there anything in particular in these links that you think is relevant to our discussion, Fresco?

Why do you do this? Why do you post some link, which discusses many things in great detail and at great length, without even indicating what you think is relevant?

If I tell you to read Builder's book, what have I done (other than imply that I am not capable of summarizing any point that I think is significant and succeed in sending you on a "wild goose chase")?

Care to quote one or more excerpts which you think are relevant?