studiot

Yes I awarded you +1 for staying awake for 48 hours, but had to take it away again for rambling whilst in that condition and particularly because my lotto numbers didn't come up. Sorry. There are several things wrong with your rambles. Here is the shortlist. No I do not think that Mathematics is constructed to explain the universe. There are plenty of things and matters that are outside the boundary of my Venn diagram. So there are plenty of things in the universe that methematics does not address. This, of course, is also true of Logic and Philosophy and indeed every other discipline. Mathematics and Logic do not set goals. That is an important statement because that is why human activity is not constrained by either. As an aside, nor does Physics set goals. That is part of the reason they both address the question of 'how' rather than 'why'. Human activity also includes rational thought, sensible sensible thought (and their opposites). These are not the same as the logic.discussed in this thread. You should perhaps read the scifi novels about A and NullA by AE Van Vogt which explore the boundaries of formal logic. https://en.wikipedia.org/wiki/The_World_of_Null-A It is also instructive to study how electronics engineers have diverged from formal logic. Firstly the customary presentation of formal logic requires two connective 'and' & 'or'. Theoretically this can be cut down to one, 'nor', but this is rarely done. Electronics engineers however have built a huge industry based on the nor gate. (Yes I know that and & or gates are also available but nor gate implementations are usually more efficient.) But they have gone further and implemented a whole family of devices and system of logic known as 'tristate', which extends the formal logic discussed above. I look forward to more accurate predictions for next week's lotto.

Agreed, although rather than say 'true' which opens another can of worms, I prefer to say 'is compatible with the stated axioms of the discourse, along with their derived theorems' For example the fundamental theorem of algebra asserts crudely that every polynomial has a root (and therefore 'the existence' of complex numbers) So [math]\exists z:z = \sqrt { - 1} [/math] Means that the square root of minus 1 is compatible with the rules of algebra when we include the complex numbers.

Perhaps you are not aware that the statement "There exists" has a very precisely defined meaning in Mathematics, as well as its own symbol. And this meaning is different from the definition used in other disciplines, including general English and in Philosophy. Yes it is a separate discipline, but it is nonsense to suppose it has any desire or will or capability to supplant any other discipline. Actually it deals with aspects of chance, not dealt with by Mathematics. I would say that Philosophy does not deal directly with the numbers (probability), that is the province of Mathematics.

Because there are elements of mathematics that are not reflected in philosophy (treatment of chance for example) and elements of philosophy that are not reflected in mathematics (discussion of what is existence? for example)

What % come here to engage in proper discussion and what % come here to preach like this one or the one you closed earlier today. I.E. are there actually any who really want these answers or are we just suffering a procession of closed minds?

OK, we have established that you need a more robust 16 volt DC power supply. Since it seems to be a waste of money getting a Logitech one, you have several options. 1) Some older laptops have 16V DC supplies. More modern ones are in the 19 to 21 volt range. I have PM'd you a link to an IBM 4 amp one for £1.20. Or look in a computer shop. 2) Some Yamaha music equipment uses 16 volt DC 2 -3 amp adapters. So look in a music shop. 3) A universal adapter around 2.25 - 3 amps capacity and set it to the correct voltage. However some cheap versions of these don't last any better than the Logitch variety. A couple of further points. Make sure you have a decent UK mains plug connection, some click together ones are poor to dangerous. Make sure you have the right plug connector on the output unless you are prepared to change the one that is there. This is a disadvantage of the universal type. the click together all purpose connectors can easily become undone or just loose. Cheers

Useful summary Sensei, +1

It is about probabilities, not certainties. There is a possibility that the EM radiation from a cellphone will activate circuitry in an unwanted way. Therefore there is a finite probability of this. Imagine, for a moment, that you are blind and standing by the side of the road to cross. You could simple march across, like small animals do. There is a possibility that you could get across without being hit by traffic and a possibility that you could become roadkill, like many small animals. Would you take that chance? Back to the cellphone. Electronics works on electrical energy, and as the industry has developed the amount of such energy needed to create an electronic action in electronic devices has fallen dramatically. Even the device leads and connections on a circuit can pick up EM (electrical) energy that is passing through. Mostly this pickup falls beneath the threshold to alter circuit action , but as electronic devices uses less and less power, the gap between pickup and that threshold grows ever smaller. However in order to communicate with a cellphone mast, the phone must broadcast a minimum quantity of EM energy. This is not really getting smaller these days. Further many other electronic devices nowadays operate in the same frequencies as cellphones, so pickup will be more efficient. So there is a real possibility that ever more sensitive equipment will pickup a small pulse of EM energy from a cellphone suddenly communicating with a mast, and then malfunction. Again would you like to take the risk of being connected to that most modern piece of medical gadegtry at the time? Incidentally it has always been known that not only EM radiation, but ionising radiation and even neutrinos can affect computer memory by changing the charge on a single memory cell. And the actual charge a memory cell requires to change/ indicate state is incredibly low these days. So, even without cellphones, computers are vulnerable to memory degradation from passing radiation. And medical devices (like many others) routinely incorporate memory these days.

Yes, I looked up the Mandelbrot reference for you and I didn't realise how long ago his famous book (in English) came out. 1982. You really ought to read The Fractal Geometry of Nature. It is not too mathematical and I don't think there is even any calculus in it. However the book is a masterpiece. It answers many of your questions about fractional dimensions, the nature of dimensions, and even (if I remember correctly) discussues the Peano space filling curves I referred to. It has lots of pictures and diagrams , which should keep Mike Smith Cosmos happy as well. Be aware the the word point as used in set theory is just another name for an element or member of a particular set. So in the set of all numbers, each number is called a point, even though there are are an infinite number of them in any interval. Finally your thinking about points is perhaps closer to the ancient Greek thinking Euclid definition: A Point : That which hath no part. A Line: A breadthless length. Note that Euclid regards lines as starting and finishing so had at least two points (each end). Modern maths regards a line as going on forever, without end points. Further there was a religious dimension (aspect) to ancient Greek mathematics. They regarded geometric figures, points, lines etc a somehow 'perfect' or embodiments of perfection as achieved in whatever heaven they believed in. Our real physical world was regarded as just a pale shadow or copy of the 'real' thing.

Quickly since you are still online. I think you have misunderstood my comment about limits (though ajb did not) I mean the formal mathematical limit the we use [math]\mathop {\lim }\limits_{\delta x \to 0} f(x)[/math]

Exactly. So it depnds upon which set, which was the essence of my post. So by choosing an appropriate set you can endow your point with any number of dimensions you care to, according to any definition you choose to use.

I think there is rather more to it than this. We are again talking about the difference between the value zero and nothing (= no thing). So let us consider density = mass /volume. What sense does it make to state "the density at a point is"? A point has zero volume so you are dividing by zero. Yet the applied maths world happily uses density every day. We get around this conundrum by taking a limit. Of course the same issue applies to other properties besides density, pressure for instance. Pressue is Force/Area and we need the use the same limiting process when we consider pressure at a point. So should I consider a point as a line with zero length, a square of zero area or a cube of zero volume? These have 1, 2 or 3 dimensions respectively. To make matter worse we can also consider the reverse situation. How many dimensions has a cube? Am I bid 3? What about (1 dimensional) Peano curves then? At this point (pun intended) you need to ask the Hausdorf/Mandelbrot question What is a dimension?

36grit, You might like to know that the Logitech Z320 speakers we are discussing in this thread http://www.scienceforums.net/topic/92308-trouble-with-ohms-law-and-some-advice-please/ include a pair of back to back mounted speakers to create their so called omnidirectional response.

Yes there you are the earliest reference I have is The Acoustic Labyrinth B Olney Journal of the Acoustical Society of America Vol 8 , No2 1936 So at least 80 years ago.

Right at the beginning of your link. 'transmission line' A La Bailey et al. Bose are very late at the gate.

Thirty years, ago, sixty years ago these were called labyrinths not waveguides.

Do you offer full time courses?

The 'waveguide' (advertiser's version, not a physicist's) only works at one frequency (or a very small range of frequencies)

Loudspeaker magnets are big and heavy and do not vibrate. Yes the cones will still be driven I asume you mean on axis cancellation (along the axis between the two speakers)? A good variation of this experiment is to first test along the axis and then try again with different speaker separations. Surely you can do this from a mono source? Note that depending upon the speaker mounting/enclosure there will also be a backward wave so you will never achieve perfect cancellation. Result for Experiment B will depend upon what you mean by back to back and the same comment about mounting/enclosures apply. One other comment about experimental technique. There will be a lot of reflections in an enclosed space. This is why speakers are tested in the open air or an anechoic chamber. Final comment. There are noise cancelling devices based on doing exactly this for quietening heavy machinery (eg generators). That is, a loudspeaker outputs an antiphase sound to that produced by the machine which cancels out the machine noise. They are very effective but rely on being set up exactly right for the machine and its housing.

Hear! Hear! +1

What I don't understand is why you don't respond directly to material I post, specifically designed to help you. For instance you responded to my post #39 by copying tables of standard integrals and derivatives. I have no idea what that achieved. I repeat my conviction that you need to connect mathematics to its applications to progress, particularly in numical methods for they are all about applications. So why don't you try the question in my post#39? A very good series of books at your level for your purposes is the Edward Arnold Modular Mathematics series. In particular the book by Berry and Houston " Mathematical Modelling" Is all about connecting mathematics to its applications.

The non creationists are fighting back. http://www.bbc.co.uk/news/education-34921857

I see lots of reports of expensive replacements for the Logitech 16v airplay power supply. http://www.amazon.co.uk/gp/customer-reviews/R1T6H6BFR7IQN5/ref=cm_cr_pr_viewpnt?ie=UTF8&ASIN=B005LNS6WK#R1T6H6BFR7IQN5 Can you please confirm the model number of the speaker and power supply. Also is this 16volts DC or AC (some Logitech devices use an AC supply)? I caution care in replacement because the word seems to be that they are not man enough for the job. If we can tie down the exact requirements we can devise a better alternative.

sciwiz Are you saying that you believe two distinct objects cannot possess the same property? Or perhaps that one object cannot possess more than one property? With all that typing you skillfully avoided responding to my post#83.

Seems to contain all the standard stuff. But before you start to calculate some values in mathematics you need to know some maths to want to have the results. This is where you seem to need strengthening.