studiot

Yes it is exactly zero. By the way How did we move from a discussion about time to a discussion about distance ?

As irrelevant as what ? Or did you really mean soemething else ? Here is a quote from a famous Philosopher Pray tell me what it means Here is a piece from a famous scientist

I think it is very important that you separate numbers , units, symbols and the objects which they refer to. That is you think separately about them, each in their own right. Let us take an example of this: Making bread. Bread has ingredients. The ingredients are flour, yeast and water. There are 3 ingedients. Here the objects referred to are ingredients. The number 3 is called a quantifier or a coeffiecient. There are no units involved or if you prefer the unit i 'number or count of' But there are several types of number and 3, each with their own special features. So we could have said: There are 3 ingredients 1st ingredient,, 2nd ingredient, 3rd ingredient. Or we could have said even more First ingredient flour Second ingredient yeast Third ingredient water. Which tells us even more. First second and third are numbers, just a different kind of number. ~They are cvalled ordinal numbers, as they show order. We could also write a 1 on the jug of water, a 2 on the tub of yeast and a 3 on the bag of flour. Then the instructions might read Mix the contents of 2 with the contents of 3, than add the contents of 1. We are now using the numbers 1, 2 and 3 as symbols (you mentioned symbols) We can make the description even more use full if we add units so Mix 2 of yeast with 400 of flour and then add 250 of water is not very helpful. But Mix 2 teaspoons of yeast with 400 grammes of flour and then add 250 mililitres of water is very helpful. Much more helpful than Mix 2 teaspoons of 2 with 400 grammes of 3 and then add 250 mililitres of 1. Although both are strictly correct and Mathematicians and computer engineers like the last as it is shorter. I have another example to explore but let us see what you make of this one first.

A ROM is a form of truth table.

How w ell do those learning English do with acronyms ? +1 An SMPS is a Switched Mode Power Supply. Switched mode power supplies often also incorporate a voltage change and use an inductor and or transformer for this. Inductive switching generates large reverse voltage spikes known as backswing which can damage semiconductors when they are reverse connected. (see Sensei's graph) Zener diodes are used as protection to limit (called clamping) the size of the backswing voltage to a safe level. A second use is to clamp the voltage created on the storageor reservoir capacitor, which stores the switched pulses, to the desired level.

Not in the least bit suprised. +1 for a proper attempt at evaluation. Chemically basalt is nothing like portland cement concrete, although both are silicates. As a material basalt is more susciptible to chemical weathering attack, enhanced by subsequent detrimental attack on its own structure (HAC, ASR, Ettringite, Carbonation) and on any embedded ferrous reinforcement. This is in direct contrast to Roman lime based concrete, which continues to gain strength and hardness forever on a diminishing curve, from the atmouspheric carbon dioxide.

Since you seem to just want to copy others, rather than answer my questions I will leave you to it.

Did I see that knee jerking before you read and investigated my article ? The ground up basalt is produced anyway. It used to be discarded as slag waste. It can be spread along with fertiliser don't forget that this is reduced, they mentioned a fig of 25% saving of fertiliser. However I do agree with your point about carbon credit trading. I regard it a scandal. So are you saying that new improved technology should not be employed even if it brings environmental benefits ? To all I never said this to be a universal panacea. In the advertising words of one supermarket, "Every Little Helps"

Why not ? you are just dressing up incredulity as something more; I still don't see a problem. I haven't checked your numbers but it is an observed fact that clocks lower in a gravity well run more slowly so Bob will record less elapsed time for the same interval.

Earlier this year I watched the BBC Earth series, presented by Chris Packham. One new theory was presented of many years of almost continuous rain on the early basalt eruption surfaces, leading to chemical weathering of the basalt removing significant quantities of acid greenhouse gases, particularly carbon dioxide, from the atmoushphere and chemically 'fixing' it into the ground. Last Sunday the BBC Countryfile programme had an article about trail replication of this process by spreading the waste products of the aggregate industry (ground up basalt) onto farmland. The greatly increased active surface of such basalt powder not only reacts quite quickly (ie at human timescales) not only fixing the carbon but also releasing new nutrients to the soil, thereby reducing fertiliser demand. It is too early to tell just how good this since trials have been going on for little more than a year but apparantly early results are 'encouraging'. ****************************************************************************************************************************************************************** Then I see that someone has done something about waste plastic from laboratories, formerly just burned (5.5 million tonnes in the annually), to make recycling possible. Well done Helen. Nice to see up and coming graduates succeeding like this.

That was going to be my next question. +1 But the issue here is How do Bob and Alice know when to start their clocks ticking ? Obviously they must have lived 14 thousand million years in order to make the measurement, plus a little bit to build their clocks and synchronise them.

So why is that a problem ? Bob is at the bottom of a gravity well, compared to Alice, so expects his clock to run more slowly. But you haven't demonstrated that your figures are correct for the time of flight and height difference.

Thanks, Joigus. +1 I think you may well be right, although I try to avoid these more exotic non mainstream symbols. You have done better than the author who had the opportunity to this is what he meant, but chose not to for some reason. If nabla squared is meant then in my opinion that is what should be said. The square is often called the box operator but it suffers from the disadvantage that I have seen it confused (used for in lecturres) with the Hodge star operator and also is presented by some parsers as a general symbol when they come across something not in their vocablulary. Word is bad in this respect. Also remaining is the mathematical demonstration that the second order differential equation obeys the Lorenz transformation, using the speed of sound as an invariant. The simple fact is that to an inertial observer moving differently from the air, the speed of sound appears different.

Or set the problem out correctly, filling in the missing lines telling us where your figures come from and showing us how exactly the two photons can have followed exactly the same path (world line ?)

Guiding would be better than telling. You still haven't answered my questions. Since you are doing this in preparation for a real exam it is no good just looking up formulae on the net (especially as I suspect it is wrong but I can't see the rest of what you found). You need to understand what you are doing. And that is exactly what both Seth and I are trying to help you with. So let us go back to first principles and answer my simple questions. Do you have to derive your equations or have you been given them in lectures ? Using your knowledge of Physics is the internal ressure greater than or less than the external ? Why did I suggest you will have a circular blob ? You new picture is wrong because the vertical meniscus is not a complete semicircle. Why do you think this is the case ?

How's that ? We all have trouble with the TEX of one sort or another. I have a ridiculously expensive commercial generator called Mathtype. Alternatively you can use free sites Codecogs or Sciweavers to have a TEX editor and copy paste from it. Another possibility (though limited by the inability to produce almost any sort of fraction) is to combine this SF super and subscript and use windows charmap to pick out special characters such as greek letters. You can actually achieve quite a lot this way.

I was going to examine your 'mathematics'. I can't make head not tail of this equation unless you have nabla the wrong way up ? If you have written Δp then the equation is nonsense. You seem to have corrected this few posts further on but a recognisable wave equation is stated and is indeed the equation you seem to have copied from Wikipedia. Unfortunately you seem not to have read the text where Wikipedia clearly states that this is the equation of a standing wave. My example involves a travelling wave and Wiki refers you to a simpler first order differential equation, which it call a one way wave equation in its own style. Note Wiki clearly states these 'preferred frames' to be hypothetical for the purposes of exploring what if there were such a frame. It makes no guarantees that there is one and indeed states there is not such a frame in an inertial set of frames (as we all know).

Love it to bits.

Is that incompatible with what I said ? Glad to hear it. We need We need philosophers to ruminate, but it is better if they chew on what we know rather than guessing, of if and when they do guess then they cary out testing of their guesses.

Part 1 You are working in the right direction, but if r = h/2cosθ (which is correct) then how is 1/r = 1/(h/2) in your first line ?

What makes you think this sort of thing hasn't been done before ? Apart from a 200km transmission path across the atmousphere (It's much easier for satellites up throught he atmousphere) beig far from isotropic or homogenous, What is the effect of a 1m, 10m, 100m, 1000m error in the placement of your helicopters on your calculations? Before we had all the satellite stuff, (and swansont is far better placed than I to discuss them) folks did this sort of thing by an instrument called the Tellurometer. This was invented / developed for the surveys of South Africa, Australia and Canada. Mountain tops, rather than helicopters were used as they do not move about and their positions can be independently verified. My experience of lasers is that they do not have the range, across the atmousphere, most have a range of a few km at best and the Wild Distomat was really up to a km. They had corner reflectors rather than independent clocks aand there is now such a reflector on the Moon using up through the atmosphere techniques. You still haven't told me how you are goung to create your pulse for 1000gHz signals.

Appreciation for the plus marks, but answers to our questions are even more appreciated. We can't tell you the answers, just help you find them for yourself. So what about R ? And what about the other questions, What for instance did you get for Seth's suggestion?

Is this homework ? Then it belongs in the homework section. Hints 1) is the liquid pressure greater than or less than the outside pressure ? - Why ? Then do a force balance between the pressures and the surface tension along the curved interface. It is usual for the liquid to be considered as a circular blob so you can calculate the area Over to you to put the values into your formulae.

Only one hundred years, gosh that's nothing. Pythagoras lived a lot more than two thousand years ago yet his theorem has yet to go out of fashion. So much so that I probably used most every day of my working life.

Two methods spring to mind. In the analog world electrometers and potentiometers measure voltage directly. In the digital world the digital version of the potentiometer also measures voltage directly, hence my comment about digital multimeters.