studiot

Welcome as a practical man. Then you have come to the right place to ask technical questions and get sensible answers. But please remember that some will immediately assume you are a scientist and that you have knowledge of theoretical science. You might also be interested to learn that the Romans used levels to build bridges too. They did not possess our curved modern spirit level vials but had to make do hollowed out channels and water. Their levels were about 10 metres long as a consequence. But using them they were the first to be able to able to establish were to start building the foundations for arches that would eventually meet in the middle and cross a valley. Flat Earth and spinning Earth are two different things. They are only very loosly connected. Flat Earth We can easily observe that we live in a 3 dimensional world. So it is excusable for the ancients to believe you could reach and fall off the edge of a flat Earth. But today we know from experience that you can sail round it in any direction and only ever reach your starting point, never an edge. But even the more intelligent of the ancients realised that a flat earth could not explain why a departing ship gradually 'disappeared over the horizon'. Spinning Earth Look up into the sky. In the day you will see the sun 'moving across the sky'. In the night you will see stars moving across the sky. To explain this either the sun and stars are moving or the earth is moving. But which? Well firstly it is clearly cyclical because the same sequences are repeated over and over again. So something is moving in a circle. But wait. Not all 'stars' follow the same speed round and round. We call these planets, and these do not even follow regular paths like the stars. Indeed one of the planets is named in ancient greek for wanderer. If everything was fixed on or in a giant sphere circling round a stationary Earth, then how and why are these moving faster? If the Earth is spinning then everything a very long way away would seem fixed in place as if on a giant sphere because any local movement they made would be tiny compared to their extreme distance. You can see this same effect on Earth where distant object appear to move very slowly compared to their actual speed. The local movement of those few things closer (planets) would of course be readily observable as a different movement.

I think what jajrussel means by local is the horizon of influince of a phsyical phenomenon. I can't seem to upload this animated gif from Caltech, but it shows how relativity affects the field of a charge when it moves. Local would mean in the expanding circle. http://www.tapir.caltech.edu/~teviet/Waves/empulse.html

If you don't ask questions and dont discuss, how are you ever going to learn from those that went before you? Your first task should be to distinguish between level and straight. They are not the same. A level line is at right angles to the direction of gravity (i.e. at right angles to 'up' and 'down') at any point on the Earth's surface. Obviously a level line will curve as up and down point to the centre of the Earth. But there are other effects that also change this . It is fascinating to learn that the discovery of the Himalays by western men was made because they realised that the plumb bobs in their theodolites were not hanging what they thought was 'down' during the 'great arc' survey of India. The enormous mass of the Himalayas did (and still does) locally change the direction of gravity enough to draw the plumb bobs aside measurably. Light rays travel in straight lines so optical equipment based on light, or these days lasers, will observe in straight lines. For short distances up to about 100 metres there is little difference between a straight line as measured by an optical instrument and a level line, so no one bothers up to that point. Beyond that length the difference starts to become important particularly as the factory example I gave incorporated flow lines several hundred metres long that required to be level, not straight. Bridge decks are often precambered (bent upwards slightly) to offset the sagging in the middle due to gravity when the decks are in place and sometimes have curvature for other structural reasons. Neither a level line nor a straight one are normally the primary consideration. Pipes are manufactured in straight lengths, but pipelines are suprisingly flexible and are normally laid level, In fact the their flexibility is what allows them to be laid on the bottom of the sea bed from a surface laybarge. Finally another mechanism can affect all this, as happened on the Alaska pipeline (and elsewhere). It is called refraction. A light ray will change direction where it encounters a different medium to traverse in its travels. You may have seen the sideways displacement demonstration through a glass block. This can also happen if the air changes significantly aand the ray passes from a warmer to cooler layer or the other way round. So steal a march on your mates and learn a bit about the world around you, rather than just guessing how it works like they are.

I also think Strange was misunderstanding your thinking, perhaps because you are unsure of some of the technical words / technicalities. I am still pondering how to point it in the right direction, because there is something in your local v global idea, but it needs some revision / amplification.

Mr Cuthber, for once we are agreed. It must be Christmas. +1 My points here are not that Mathematics does not employ logic at some stage in a proof by exhaustion, 1) but that in some stages of the proof it does not. I think the last important proof by exhaustion was that of the four colour problem. That proof certainly involved substantial logic to construct, but the testing stage could have been, and in fact was, carried out by a dumb machine or monkey. 2) As far as I am aware there is no such method of proof, as proof by exhaustion, available in the discipline of formal logic. So it does not appear in both disciplines. A final observation is that there is one gaping hole in the disciplines chosen in this thread. Philosophy and Logic are basically silent on the issue of seting goals.M Mathematics, I'm not so sure about. The statements I want to climb that mountain I want to solve the NP hypothesis are neither logical, nor philosophical. The words practical, sensible, rational all come to mind. It is a good job that English can convey ideas and concpts outside of these three disciplines. Enjoy your Sunday lunch.

I suspect it is a borderline case. Again we are reaching into fuzzy territory, where the boundaries are not crystal sharp. A further thought. I wonder if modern technical and engineering mathematics isn't leaving Logic and Philosophy far behind? Formal logic involves creating 'chains' of reasoning akin to but often much grander than the one about my quadrilateral. But every link is connected; there are no disconnected or isolated links that cannot affect the chain. These days, with FE analysis, Event Horizons, and whatnot we are often dealing with many chains that may be separate in one part of the analysis and not in another.

Of course. All I have ever asserted is that there are things in Mathematics that are not part of Logic and things in Logic that are not part of Mathematics. I have never asserted that those things are disconnected in some way from those that are in both (of which there are legion). Of course you can't get very far in mathematics without logic. Thinking again about my Turing machine, If I take the definition of a quadrilateral as a closed line drawing with four sides, do I need any logic to look at a line drawing to decide if it is a quadrilateral?

Good morning, ajb, (and Ms Shelagh are you not talking to me?) The is a minimum capabilty that is required in order to apply a process belonging to any form of logic. For instance a Turing Machine has the capability to make a decision. You do not have to have this in order to perform some mathematical tasks (i.e. perform some mathematics) For instance my Austalian Aboriginal Surveyor's Assistant cannot count, does not know what number he has counted, indeed does not even have the concept of number. Yet he has achieved the mathematical task of accurately counting the number of chains laid using the stones. A trained monkey or machine could have done the same. Yes others can apply logic or its fruits or to the result but counting the chains is nevertheless a piece of mathematics. Here is another more vivid example. Take a die and roll it. Copy or photograph the symbols on the upturned face. You have achieved the mathematical task of the selection of a random number. Did it take logic? No. Could a Turing Machine have performed this task? No. Why not? Because the Turing Machine has to make a decision before it can move on and complete a task. But no decision is required in this example since you copy whatever is there. It may be that a small mathematical task is part of a larger mathematical task, which does require logic, but there remain some sub tasks that do not.

Have you given up on this one?

Have we changed the subject? This bout of thinking by you is not perfect but it is much better than some (ofyour) other stuff so keep on questioning.

Simply repeating the question doesn't show that you take any notice of what you are told. Molecules translate translate (move) randomly not chaotically the without a controlling influence. Chaotic vibration is inherent in Euler's laws of motion, otherwise the vibrations are precisely defined.

Having built all these things in my day I can assure you that civil engineers and even builders of large buildings have to make allowance for the curvature of the Earth. As I recall the new engine factory for the Ford Motor Company required a correction of around 10mm between its ends. You will find the calculation details in any surveying book.

The short answer is greater thermal motion in some other body. In other words heat flows from hot to cold. Did you look at my last post in your other thread?

Of course they are. But it is possible to carry out (some) mathematics without logic and I think , some logic without mathematics (though I fully admit to being less expert here) As a for instance there is no logic involved in proof by the method of exhaustion or the old surveyors' method of counting by transferring stones from left pocket to right pocket. As an example of the difference i spoke of, proof by induction in mathematics refers to quite a different process from induction in formal logic.

Neither Mathematics nor Logic is a branch of the other. They possess common processess. It would not be fair to ascribe a common process as belonging to one or the other and simply applied by the second. You cannot say that a ball belongs to cricket and is applied by soccer or vice versa. But they also both posess process not available in the other.

Checking through your posts, I think you are suffering under a misunderstanding of some of the basics of Thermodynamics. In popular writing entropy is often portrayed as energy that is somehow unavailable. Nothing could be further from the truth. Entropy is not a form of energy. Entropy is heat energy divided by temperature. To suggest that they are the same you might as well suggest that mass is the same as force. After all, mass is force divided by acceleration! Or that specific heat is a form of energy, since it is also heat energy divided by temperature. Note carefully that heat is only one form of energy; there are many forms that may be gained, lost or possessed by a system, one being converted to another by thermodynamic or other processes. Now in order to model such processes we have to be able to specify the system and most importantly define the boundary around the system. I cannot stress how important the boundary is. The boundary is important because we have two laws that describe what happens when energy crosses that boundary and enters or leaves the system. The First and Second Laws of Thermodynamics. Neither apply directly within the system alone, which bring me to your next misunderstanding. Adiabatic does not mean no energy crosses the boundary. It means no heat energy crosses the boundary. This heat energy appears as a variable in both the First and Second Laws, but does not include any non heat energy. You wish to discuss energy, entropy and perpetual motion. Firstly let us be clear that perpetual motion is not forbidden by the Laws of Physics. On the contrary it is expressly required in appropriate circumstances. For example. Newton’s First Law An undisturbed body continues in its state of motion forever. Earnshaw’s Theorem (abbreviated as appropriate) A system containing more than one charge cannot remain at rest. So perpetual motion would be the natural state of every material thing in the universe if left undisturbed. What about you idea of powered perpetual motion? Engines (and you are describing an engine) must work in cycles to continue operation. Something that can only work for one cycle or part thereof cannot sustain perpetual motion against opposing forces. The first law requires that Net Work Transfer = Net Heat Transfer W = Q In other words if there is no heat input the system will eventually run out of energy to drive the perpetual motion so it will stop. But the second law requires that in order to transfer heat there must be a temperature difference. Finally where does entropy come into this? Well the original heat engines were steam engines and they had a mechanism that could draw a chart of the pressure v volume of the system. These primitive chart recorders were called ‘indicators’ and the diagram they traced out were called ‘indicator diagrams’. The area traced out on these diagrams directly represented the mechanical work done (i.e. the mechanical non heat energy transferred). It was realised that a similar energy diagram for heat energy was desirable and so a suitable variable to pair with temperature was devised. This variable became known as entropy (symbol S) and T- S indicator diagram have attained great importance in mechanical engineering. Indicator diagrams have come to mean the chart of any pair of variables whose product is energy. A look at some engine cycles shows a comparison of P - V and T – S diagrams where it can be immediately seen that entropy for the whole system decreases during parts of the cycles. This is common to many types of working machinery and the cycle for a compressor is displayed below. So what you are asking for is already done, but it has to be done in cycles.

The problem of defining what is meant by 'straight' is not as easy or straightforward { } as you might think. Newton, of course, didn't actually say straight. His words were "In its right line"

Yes logic and mathematics are separate but overlapping disciplines. Unfortunately my nice tidy venn diagram cannot do this full justice since certain processes, different in each, have the same name.

Oh did I spell it incorrectly? Sorry. Drakensberg. https://www.google.co.uk/search?hl=en-GB&source=hp&biw=&bih=&q=drakensberg+mountains&gbv=2&oq=drakensberg&gs_l=heirloom-hp.1.1.0l10.219.2313.0.4485.11.8.0.3.3.0.172.938.0j7.7.0....0...1ac.1.34.heirloom-hp..1.10.1062.bOsIYhwhXyA

The following pages may help. They are for the design of a self oscillating switching regulator. Pulse driven ones are also possible.

Note that surface area is proportional to the square of the radius Volume is proportional to the cube of the radius. So do 1000 small drops have more surface area or less surface area than 1 large drop? Surface energy, is proportional to the surface area, that is Surface energy = Constant x Surface area And that constant is called the surface tension. As a matter of interest where are all these varied questions coming from?

The problem comes with the earthing arrangements. The conventional arrangement is to use a collector follower not an emitter follower as shown in my Fig1. This leads to a PNP drive drive transistor but allows through earthing as shown in the negative rail. If you use an NPN drive transistor you have to place it in the negative rail so you have an earthing issue between the battery negative and the output negative and cannot use through earthing as shown in Fig2. So long as you usage can accomodate this then ther is no reason for not using an NPN driver transistor. MosFETS are used the days and the same thing P-channel (as Fig1) v N-channel (as Fig2) applies. Note also that the collector follower is inherently short circuit proof, unlike the emitter follower. Edit please note the mistake in fig1 as the transistor is the wrong way round. I will correct this later.

The compost story is somewhat more complicated than you have presented it, since there is no ideal or one-size-fits-all, but I suggest you start by looking into humic acids and then posting further. Here you will find chemical formulae and explanations galore. https://www.google.co.uk/search?hl=en-GB&source=hp&biw=&bih=&q=humic+acids&gbv=2&oq=humic+acids&gs_l=heirloom-hp.3..0j0i22i30l9.953.3922.0.10234.11.7.0.4.4.0.188.969.0j7.7.0....0...1ac.1.34.heirloom-hp..0.11.1171.-upd4UbOnKA One thing to bear in mind is that organic fertilising material is more acid than soil. This should be a good start, but do come back and expand your discussion, this is a good subject to talk about.

That's the way to discuss things +1

That was pretty meaningless, and certainly little to do with thermodynamics. Would you like to say that again in English? Note I put some substantial effort into supporting your proposal and I don't like being taken for a fool.