studiot

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?

I think, Robin, that this is the beginning of your difficulty. Yes the travelling clock accelerates into a different frame, whose origin (for time at least) is not the same as the origin for the stay at home clock So the t0 and t1 etc for the travelling clock are not the same t0 t1 etc as for the stay at home clock. That is why I used different letters for these frames. Why is this? Well suppose instead of being twins, B was already travelling in the travelling frame and just happened to be passing A at t0 in the stay at home frame. B then makes the two way journey. Can you tell what would be the difference between their clocks on B's return?

Good Morning, Rodrigo and welcome. OK so you are studying Lennard-Jones potentials, but your question is in relation to forces. So I take it you understand the process (maths) of going from forces to potentials? And also why we think there are two opposing forces in action? If we think of the molecule (this includes atoms) as having a concentrated positive centre surrounded by a negative electron cloud, this is a good start. Now (considering atoms for simplicity) consider what happens as the electrically neutral atoms are brought closer and closer together. At first there is an attraction (ie the attractive forces outweigh the repulsive ones) Too close and there is a repulsion. At the magic distance a0 the forces balance and we have equilibrium. We regard a0 a measure of the size of an atom, but really we are talking about the effective size of the electron cloud of that atom. If the centres of two interacting atoms are closer than a0 then there is overlap of their respective clouds. This is the source of the repulsive force, which increases rapidly as the overlap increases (ie distance decreases) If the centres of two interacting atoms are more widely separated than a0 then the repulsive force falls away rapidly with increasing distance, leaving the attractive force to predominate. The interaction between the electron clouds is also responsible for the attractive force, in a slightly different way. Again imagine two clouds approaching each other. The repulsion is stronger on the near side of the cloud than the repulsion on the far side. This pushes or distorts the clouds so that they are stronger (the electrons spend more time) on the far side of each nuclei. The thinning of the clouds also weakens the shielding of the nuclei in that direction. This slightly polarises the atom, leading to the Van der Waals type bonding you note. Note that the usual graphs of the LJ potential or the forces are like a free body diagram. That is you need to draw a (mental) dotted line around the atom as a cut line and add in the interaction force (potential) with the second atom that is not shown on the graph. Without the second atom these forces could not act. Does this help?

Yes that is what I said. I also asked what causes the ball to roll if there is no friction?

This looks like homework. What methods for establishing truth tables have you been taught and which ones have you tried here?

Many labs (and particular lab techs) are bound by standard procedures, both in the testing and the calculations. So all you can do is follow your National Standards so that whatever tests you are running conform for certification purposes. Secondly different disciplines tend to follow different statistical paths and I'm not sure what you are a lab tech in. But (I'm glad to) see you want to generalise and expand your education more widely +1 So here are some books in different fields. All are good in their own way with basic stats but each puts its own specialist bent on the subject. The first one, intuitive biostatistics is medically oriented but is a briallaint book for understanding and goes up to quite high level, despite the write up. It just avoids a lot of fancy maths. http://www.intuitivebiostatistics.com/ Then we have Statistics for Analytical Chemistry Miller and Miller Statistical Methods in Biology Bailey

Many thanks for your explanation. I had understood that the integration was with respect to x. I think I missed the first y.

Very glad to hear it, welcome. (your) Post#1 contained three sentences. Sentence 2 seemed against determinism, sentence 3 seemed against one of the alternatives. Confusing in a logical discussion. Hence the next question. Thank you. Is chance the only possibility? This is where it gets difficult, philosophically. We have had several thread discussing these difficulties. I will try to find them for you. But you need to be sure what you mean by 'chance'. (Also determinism but that is more readily) defined.

OK so I am going to do you the courtesy of assuming you are not another preacher (we have had too many just lately). So I will ask what you mean by your first post as it seems to me to have a contradiction. (second sentence v the third) Are you for or against determinism? What do you you think are the alternatives?

OK, glad you liked it. If you want to move on to examine the formulae Mordred and Elfmotat referred to then please tell us if you are familiar with the following The difference between a function and the value of a function These symbols [math]\frac{{dy}}{{dx}}[/math] and [math]\sum\limits_{}^{} {} [/math] Matrices Column vectors Row vectors If need be I can include enough explanation with the next post.

Really pertinent comments, strange, +1 Fred, I don't know if you have done any digital electronics (back in the dim and distant I did a college project to design and construct a remote pc keyboard) but real world signals look nothing like your sketches. One of the biggest issues is telling the receiver when the signal starts or stops, ie when a data pulse begins or ends. What coding you use is far easier to deal with.