It comes down to an innate sense, I guess. That's the only answer I can give.

It is somewhat a matter of choice whether SR can handle accelerating clocks. Strictly from the postulates of SR, you really can't handle them. But if you assume that accelerating clocks behave just how you would expect them to (instantaneously the same as a clock traveling at that velocity) you can deal handle them in a straightforward manner.

I would say that the experimental tests of relativity are quite robust. Every test of special relativity that we can perform it has passed. General relativity has also been tested in a few different ways and has always passed. Quantum Field theories are the most accurately tested theories we have and they are relativistic so that is a sort of back door test on relativity that it has passed to a much, much greater certainty than the direct tests.

It doesn't seem like you need to understand any science to get what you said craig is saying. He is just saying that all "real" observers in the physical universe will see things one way, but there exists some observer outside the universe who sees things differently. There isn't going to be any way to verify or disprove that (basically by design). I wouldn't think too many scientists spent time writing about that, because you can say anything you want, but maybe a few people did.

What I think you miss is, going along with your last sentence, the sun really does rise from your viewpoint. It's not an illusion. However, from the sun's viewpoint, it isn't moving, and that's not an illusion either.

That's the whole point -- reality is relative.

One can always go the Craig route and say that science reveals merely what we can observe and experience and not necessarily what IS. A more reasonable view on ontology is one similar to Quine's: When forming beliefs about what's really going on, we should look at what our current best theories have to say on this matter.

But I suppose if some of your beliefs rely on time being a certain way and science says that it isn't this way, then you can always claim that ontology is not necessarily determined by epistemology.

is this for real? are you seriously implying that relativity has not been verified experimentally?

ABSOLUTELY........

I did not read the entire thread, but if I understood correctly this statement is completely wrong. There are very robust experimental demonstrations of the effects of special relativity. One very good example is the measured half-life of subatomic particles. If one measures their lifetime at rest and then measures the same value in an accelerator you get exactly the predicted increase as a function of their velocity.

I am definitely saying that the effects are 'real' - the fact subatomic particles live much longer than their halflife predicts when moving very fast is one good confirmation of this in my view. If you assume relativity is true - the time dilation exactly accounts for the apparently extended lifespans. If you think it's just an illusion - how do cosmic rays reach Earth when the particles "should" decay way before they get here? Relativity being real is a neat, simple explanation.
I would disagree mildly with Craig in that I dont think Einstein 'gets rid of absolute time' so much as he restricts his discussion to observers within the universe (ie he excludes God who has no frame of reference - all things are equally accessible to him).

I don't think it's controversial that I think of God as outside of spacetime - as such, the constraints on objects within spacetime do not (necessarily) apply to him. How something outside of time can 'see into' the universe is an unknowable mystery in my view - I certainly wouldn't try and break it down into a physical treatment though, utilising some kind of 'over-arching' frame of reference. To me this is extending science well beyond what it is designed to address.

I meant the kind of thought experiment that I've stated in this thread.

The problem theologically with no absolute time, if God is temporal with creation (He can act in time), is relativity posits a virtually infinite number of inertial frames, so which frame would be associated with God? Any one frame would limit Him to that one, associating Him will all of them would make Him separable. I haven't finished the book yet, and I don't think Craig's position is critical at all for Christian theism, but I think that is a bare outline of his thinking on the issue. Anyway, I do want at least a layman's understanding of both SR and GR eventually as I think it will help in understanding time and its relation to God.

This is nonsense.

Understanding special relativity is not like soaking up the intellectual lolly water you lap up on your Christian "science writer" sites. It is hard. Very hard. You need to realize that your current prejudices - and even the way your brain currently works - are totally inadequate for understanding the topic. You have to realize that every conception you try to create around this topic is flawed. Only when you accept that will you dimly grasp how your brain is "stuck", and be able to do something about it. It is uncomfortable, but if you push hard enough, it becomes rewarding and you gain a deeper understanding. As a side effect, you will be able to apply your newly found plasticity to other beliefs you hold dear.

With my inadequately functioning brain, I try to imagine being in a train depot and snapping a picture of a train coming into the station. Prejudiciously, IF the light leaving the caboose hits the photo plate at the same instant as the light leaving the engine AND the light from the caboose has a greater distance to travel due to the train's length AND c is constant, THEN the light from the caboose originated earlier in time than the light from the engine.

I dimly grasp that at that earlier moment in time the caboose was further away and the train will appear (measure) longer in the picture than a picture of a stationary train. Alternatively, if the train begins moving backwards and I snap another picture when the front wheels are in the same place as the first picture, then the train will appear (measure) shorter than the original picture.

Then, I'm divining that the train moving away is an SR example of length contraction, the inverse of which is time dilation and vice-versa, i.e. a clock moving away will appear to click (measure) slower than a clock moving towards me.

Personally, I find it much more difficult to conceptualize Infinite Being or God than I do grasping the idea: the measurement of time slows down at the same rate as the measurement of length decreases.

I would appreciate comments, especially from bunny, RLK and duffe (and anyone else who wants to) about whether Gardner's 2 statements are contradictory.

Well I hesitate to give an opinion as to what he actually meant without having read the book. Let me say that I could imagine making both of these statements, but for clarity I would prefer:

" (Time has) no meaning apart from the relation of an object to a frame of reference".
"(Tme) can be recorded on instruments. (It does) not require a living observer".

With the same qualification that Bunny attached, I do not believe they are contradictory if I make some assumptions about his intent. The second statement is not particularly useful though imo. If you use an recording mechanism to capture an event, it presumably functions the same as a conscious observer. Of course, what does that mean until someone actually looks at the device to see what it recorded?

To me this is much the same as the idea of multiverse. You can perhaps show the validity of MV through math and physics but never do so empirically. Saying an instrument registers something that no one can read is no different.

The difficulty I have is saying two clocks actually register slower than each other. I can grant it as a useful theoretical device but then all kinds of things that aren't real are like that - Hawking's imaginary time, for instance.

I'm not saying I'm right, just that I don't think I'll ever understand how that theory can be actualized.

I don't see how this has anything to do with the multiverse idea. The basic concept of special relativity is that your intuitive sense of time as an absolute across all frames of reference is flawed. There is no absolute overview available to us that allows us to observe two clocks moving relative to each other without getting caught up in the difficulties of transmitting a signal at a finite velocity that is constant in all inertial frames. The statement that each clock is moving slower than the other is just not true. There is no way to make an absolute statement about which clock is moving slower. Any statement is made within a specific frame of reference and is valid only for that frame. No multiverse required.

I meant that it's just a thought experiment which may have validity in math but can't be shown to be actual, like the MV.

Suppose you could instantaneously transport between trains. While on A your clock reads 1:05 and B 1:04. You beam over and now clock B reads ? and A reads ? Assume no time for the transport. If A now reads 1:04 and B 1:05 then either A ran backwards or it's just a question of perspective, not of the A clock actually registering a backwards time.

You have a fundamental flaw in this picture. You cannot instantly transport. If you could instantly transport than the basic concepts of special relativity are flawed and the whole picture collapses. That thought experiment is just not valid.

Also, special relativity is based on experiment very soundly. Start with light. If I measure the speed of light from the sun at rest relative to the sun and you measure the speed of light from the sun while moving towards it, we get the same answer. That problem of the invariance of the speed of light regardless of reference frame is the beginning of sr. To reconcile those two observations leads one to time dilation with relatively simple algebra.

http://en.wikipedia.org/wiki/Introdu...ial_relativity

Then special relativity is not correct. Nobody has no idea what would happen in this situation because there is no theoretical or experimental reason to pick any answer over any other. All experiment and theory we have tells is that what you say is just impossible.

I'm not opposing SR. I think what happens is logically I end up with absolute time (really, an absolute inertial frame) as a metaphysical truth. Newton believed in absolute time. I don't see that SR disproves it though there is no way to prove it either. At any rate, my problem with Gardner appears to be more one of language than science.

Are you sure you're not "starting with" an absolute time frame?

I don't think you understand SR then. Certainly there could be some non physical absolute time (that idea is designed such that it makes no observable difference whether it is true or not) but Newton's reasons for thinking it was correct are no longer valid and have been proved to be incorrect.