studiot

Here is the back of my envelope for the unaided human eye. The receiving angle or angular field of view is 114o or 2 radians. Light travels at about 3 x 108 metres per second or 3 x 30 x108 metres in 30 seconds approx 1010 m So the arc of your max field of view is 1010 m. This is equal to [math]r\theta [/math] or the radius times the angle. The radius is of course the distance away of the travelling object. 2r = 1010 m r = 5 x 109 m or 5 million kilometers. Now if you will supply details of the illumination of the object, or if the object emits light in concentrated beams eg then the minimum size of object to supply the minimum eye sensitivity over this distance can be estimated.

Not at all. In fact I did say that the block universe model has some merits. I have just been trying to find an alternative way to explain why I assert that the block universe contradicts both determinism and chance. Here is another. Determinism F IFF E IFF D IFF C IFF B IFF A Is an example of a deterministic chain of causation leading from A to F. Chance F OR E OR D OR C OR B IFF A Is an example of a chance chain of events leading from A to F. where A through F are events or points in the block universe. If A leads to F in either route, deleting A will not delete B, C , D, E or F from the block universe, by definition. But the only way B, C, D, E or F can occur is if A occurs. This is a contradiction. Yet another way to put is would be to note that the block universe regards the axis variables as independent and equivalent. They are neither, because there is an additional constraint which reduces the number of degrees of freedom from 4.

Of course I will try to make my points more understandable, but it is a good job I waited as it seems you are getting there by your own efforts, which is always better. I wouldn't describe the block universe as rubbish, it has some merits as a model. But it is definitely not exact. In fact it is arguable that the only perfect model of anything is the thing itself. Back to the issue at hand, Consider just for the moment the possibility of a super being - Maxwellian Daemon or even a God, external to the block universe. Or perhaps a non intelligent agent but still external to the block universe. Such an agent could intervene in the future history of any sort of particle and prevent whatever the laws of physics had projected for it unless it was a block universe where that projection co existed with the past and present. Notice I have not said any such agent exists, just that a block universe would preclude any action by that agent.

It is easy to find counter examples if a proposal is either to narrowly constrained or to general. The trick is to find a happy medium between those two extremes. Your definition of the term model is far too restrictive, yet your comment that the modeled will always be one step ahead of the model is demonstrably false, because it is too general by the use of the word always. A model may be a pattern (in the sense used by pattern makers) or a copy. So it may lead or lag It is, however, instructive to consider the following. It is possible to make a real physical model for that of the abstract characteristics of something else, or something totally abstract. For example analog computers are real physical models of mechanical systems or abstract mathematical constructs.

None of that runs counter to what I said, except the no not really. I quite specifically said that both determinism and chance embody change. But there is no change in the block universe, or even the possibility of change. That is the meaning of the word immutable. A multiblockuniverse possesses the same characteristics. All the blocks must already be lined up.

Why so? Go to the Hydraulics Reasearch Station at Wallingford and look at all the modelling they do for design purposes. Both physical models and theoretical ones are used.

No problem, but you had been arguing so cogently that I thought I'd mention it. Intuition is a double edged sword that can lead one astray. Determinism basically means predictable by a chain of reasoning Now this was fine and dandy and led to many spectacular scientific successes, not least the kinetic theory. So it seemed a reasonable proposition in say 1890 that given enough data about every particle it would in principle be possible to predict the future course of each and every particle and therefore the universe. It was not quantum theory or relativity (special relativity is deterministic) that put the cat amongst the pigeons). It was radioactivity. It is not possible to determine the future course of any radioactive particle, only averages of aggregates of them. I said that the block universe refutes both chance and determinism. Both of these are about the process of arriving at a future course ie a process of change. In order for there to be a future course it is necessary for there to be change. But since everything is already set in the block universe and is immutable, but definition, there is no change. Does this help progress here ?

A model can still be a physical entity. Just because something is a model does not prevent it being an entity.

Well the book talks a lot more around the subject, but it is no picnic. Good reading. If you can't find the book I may be able help with a scan of the relevant pages, there's about a dozen.

Dodson and Poston Tensor Geometry Chapter VII part 3 Bundles and Fields The equations of special relativity are algebraic equations. As such they have algebraic solutions ie the solutions are one or more numbers. The equations of general relativity are differential equations. As such they have functions or equations as solutions. Some of these are equations of motion so it is not surprising that some of these solution equations of motion are a form of wave equation (which is an equation of motion)

I'm sorry but this is a science forum; assertions like "it smells bad" are not adequate reasons for rejection, scientifically speaking. You quoted my comments where I referred to the first and main phenomenon that disproves determinism, but made no reference to it ?? Again you quoted my reference to the Block Universe, without reference to my observation of the logical consequence of its construction, but did pick out the " equal footing" concept from one of the links. In fact the footing is not quite equal since there is a factor of the speed of light needed to modify the time axis to 'equalise'. this footing. Did you also pick this part out?

I await your substantiation for this.

Forgive me for using a standard English word in a standard manner. Let us consider the implications of this. Is a human an entity? If we agree to say yes then Cut off a hand. Is the hapless human still an entity? Yes again I think. Now say I (a human entity) am angry. Anger Is a property, not an entity. I can transfer it to you by shouting names at you so you become angry. I may even become no longer angry as a result. Am I no longer an entity?

But I am addressing the original question, though I would agree that it was not well phrased since the word 'physical' is arguably redundant. This is exactly what I am saying. You need to separate the thing (spacetime) from its properties (qualities or relations) to decide if it is an entity. If this cannot be done then spacetime is not an entity.

Sorry if what I said was not clear. This is in part due to my attempt to use popular language about frames, which was perhaps a mistake. So first a word about frames. Frames are nothing more than a set of reference axes, indeed they come from the phrase 'frame of reference'. Some are more some are less convenient to work in than others. Some are Euclidian or rectangular xyz frames, some have other configurations. Since you can describe the desired properties of any object in any frame, you can either say that the object is in all frames or that all frames are equivalent. Maths is required to effect correspondence between particular frames and effect the transformation to these properties as a result of changing to new reference axes. So really I should not have said (as per popular parlance) an object enters one frame, and by inference leaves another. The object can be described (referenced) in any frame; it is we who are changing the reference, but both the source and target frame are still valid before and after the change. So this was a very good question and picks up my overloose phraseology. I should have said something like Observations of the travelling clock are made in a different frame from those of the stay at home clock. In particular I should have used the word in not into.

I was called away whilst adding to post 121 so Koti didn't see my last comment. I don't know if you did either, but it addressed your question. Put another way I am suggesting that the question (as I understand it) asks if there is a 'container' , separable from the contents, which would still be there if our current version of the equations of relativity were changed again? Don't forget that 1) There is more than one solution to the equations of relativity, we try to pick the most appropriate. 2) The equations themselves have chaged several times over the last century. The equations of relativity have changed m

Your example of what you mean is fine, as is your reasoning about models in general. However your reasoning starts from the premise that spacetime and relativity (general or special) are synonymous. They are not. Relativity provides a (mathematical) model of something (our universe) that would still be there if the model were at some time shown to be incorrect or inadequate. It is a matter of semantics whether we call that something 'the universe', 'spacetime' or my 'backyard'. Edit : added comment. I take the question to mean, Is there a separate fabric (like the grid on my avatar) that everything (matter etc) exists in that we can call spacetime?

Strange is right The 'clockwork universe' idea goes back a long way, and held sway in scientific and philosophical circles from the renaissance right up to the late victorian times. https://en.wikipedia.org/wiki/Clockwork_universe The block universe is a much newer idea https://en.wikipedia.org/wiki/Growing_block_universe The former is falsified by radioactivity as we know it. The latter suggests the intriguing thought that both determinism and chance are false since they both rely on change.

This is where your intelligence and experience come in. Do you have reason to think that the region your light.dark detector is probing is in the light or the dark? Or has your detector simply run out of battery?

Not if you read it in " The Purple Book of Fairy tales" There is no reason why a fictional story may not refer to an imaginary fruit (and some do).

Now the philosophical discussion is beginning to motor. You can say There are tomatoes that are not red. But can you say There are bloob fruit that are not red? or There are bloob fruit that are not real? Edit I don't know about dark, but shadows exist n'est pas?

Yes I agree that there are imaginary things. But look at your double use of the verb to be tying the question up in philosophical knots. There are things that are not....

Sorry to both SJ and Strange, no affront intended. I don't get the impression that is what koti is saying since the extract I quoted asked for confirmation that this was another's position. I think koti means that reality includes more than just what we can sense. The debate is about what additional considerations we admit and I await clarification from the horse's mouth.

Exactly one reason why koti's stance is a very sound one. +1 The problem being that our 5 (or whatever) senses can be tricked (or just plain faulty) and we need interpretation to avoid this. That is we need a combination of observation and interpretation, followed by further testing (observation) and confirmatory observation What, did I just describe the scientific method?