studiot

Somewhat dificult to comment without knowing the %s involved.

Thanks a bundle Endy, I will investigate this further. +1 I note that the IP is listed along with some more. Others beware. The IP is a gateway and some ill intentioned users hide behind random letters as in my screenshot.

I don't have another browser.

Don't forget in the realm of thought experiments we are able to escape the chains of an imperfect universe. So all our equipment can be perfect. Further we do not need to specify how a given state could have been arrived at, so long as it satisfies the physical laws invoked.

Still hoping for an answer here from the site heirachy. If I block this IP in internet explorer I can't get to SF at all.

What is not clear is why you don't respond to my comments ?

This is incorrect. t is not squared in the formula final velocity = initial velocity + acceleration times time (V = U +ft) Be careful with your signs as well is g positive or negative? the correct expression for time to vertex is t =( v1sin(a))/2

If the hydrogen bond were covalent, which hydrogen orbitals would the electrons occupy? Is your diagram referring to something specialised like this? http://jolisfukyu.tokai-sc.jaea.go.jp/fukyu/mirai-en/2011/4_11.html And how is this all related to the topic?

A discussion about the relationship between life and thermodynamics can be quite interesting unless only one side in that discussion is allowed to speak.

I am currently reading this fascinating book about the effect on sea levels the last time the icecaps melted about 15000 years ago. It was written by a Californian sailor and discusses now submerged places such as Doggerland in the North Sea and others around the globe in the light of the effect on human history as well as changing landforms and coastlines. Doggerland is interesting because the oil companies have released much North Sea survey data for study by anthropologists, and other scientists. No outlandish claims are made and the book has lots of solid references to modern research results. Below is an extracted map of Doggerland. The main point seems to be that sea levels rose rapidly at the end of the last ice age, but that rate of rise has been slowing down since so most of the 120 metre rise occurred in the first 9,000 years and modern day coastlines appeared 6,000 - 5,000 years ago. Geologically this is really a very short time, but nearly all human development has taken place in this time. Edit, nearly forgot to reference the book The Attacking Ocean Brian Fagan

This is a good example of how a practical physicists can have a feel for the question and use physics to 'prove' the maths rather than the more usual way round. So consider the line L (forget the directrix) as the position of a plane wavefront. By definition of a wavefront the light arrives/leaves at all points along a wavefront at the same time. We know from physical observations that a parabolic reflector brings parallel rays to a common focus F. So this can only happen if rays leaving any point Q on the wavefront L travel the same distance to reach the focus, since they all leave at the same time and travel at the same speed. Note that the line L does not have to be parallel to the x axis as you have drawn it. As a practical chap yourself you might like to read Mark Levi's book The Mathematical Mechanic. Mark sets out to prove many common mathematical theorems using the laws of physics "Using Physical Reasoning to solve problems"

Works for me, if you can take the distance when Q is directly above F V (ie on the y axis) to be (QV + FV). That is a doubling back. As an example if the parabola is (KISS) y=x2 (focus at 0,0.25) and the line L = 1 then the length is 1.25 or 5/4

Another adjustment please. A closed system does not allow mass (matter) to cross its boundaries. Energy, however, may do so. An isolated system bars both mass and energy.

How about an acorn cup falling to the ground, becoming detached from its acorn and becoming fossilised? Did you catch my post#20?

I have tried to avoid discussion about the cup because I think it is a distraction. However there are some points that need adjustment. Actually you can and we do. That is what thermodynamics is all about. You work from (equilibrium) state A to (equilibrium) state B... to (equilibrium) state C and so on. So you can and we do start at any defined state and finish on another defined state and not worry about what comes before or after. Actually it was a cup of tea.

puppypower you may like to look at Mollier diagrams. They plot the relationship between enthalpy and entropy. https://www.google.co.uk/search?hl=en-GB&source=hp&biw=&bih=&q=mollier+diagram&gbv=2&oq=mollier&gs_l=heirloom-hp.1.0.0j0i10j0j0i10l3j0j0i10l2j0.1593.4156.0.6875.7.7.0.0.0.0.219.985.0j6j1.7.0....0...1ac.1.34.heirloom-hp..0.7.985.aV-4v27-bBE It is not often explained, but the relationship between entropy and the 'arrow of time' is classical and arises thus. Most equations (note I said equations, there are a few laws but lots of equations) in thermodynamics do not contain time. Time is not a (thermodynamic) state variable. This is also true of the second law that leads to the arrow statement. However thermodynamics is about (thermodynamic) processes and processes are loosely about changes of (thermodynamic) state. Underlying the arrow of time is the assumption that a system cannot be in two (thermodynamic) states at once. So a variable is required that can be used as the independent variable in charting progress of a process. This variable is chosen to be time. So in changing from one defined state to another the second law suggests that entropy is a state variable that can never decrease in value at the end of any such change of state. A (thermodynamic) state is defined as complete set of values of all (thermodynamic) variables, so whatever happens the other variables must adjust to meet this requirement on entropy. So the only permitted changes are those which produce a compatible set of values of state variables for the second state in the process. This is colloquially known as the arrow of time. When you break it down there are several indirect steps to lead to the result.

Hear! Hear! +1

You asked for an equation. I do not have a suitable definition of disorder (or order for that matter) to offer one so I did the next best thing and gave you an answer specifying the conditions (as well as I could) to obtain an equation.

Need I say more?

Entropy can be quantified by definition, but you would need a quantifying definition of disorder, using connecting variables, to achieve an equation. Do you have one?

Example of what please?

puppypower you have obviously studied some thermodynamics. Unfortunately you have some misconceptions mixed in there. No, internal energy and enthalpy are different properties. Enthalpy is sometimes called the heat content. Yes entropy is a state variable, but states are defined as equilibrium states. What if the system is not in an equilibrium state? Most of the time, most of the universe is not in an equilibrium state.

You claim to have had philosophy training in logical thinking. But this and this are prime examples of this I believe the phrase is 'Hoist your your own petard'. Whilst you steadfastly ignore my actual point, You are the one who introduced probability in relation to both the Monty Hall problem and quantum mechanics. But the problem is you do not understand probability so your reasononing is flawed. I said your example was a poor one to use but you insisted on using it so I am trying to make do with it. The above analysis make no sense. Here is my version and I make no claims that it is perfect, I may have forgotten something vital. Your traveller approaches the junction for the first time in history. As a result you have no information about the probabilities as to which way she will turn. So your best estimate is equal probabilities. But you also know that people drop dead and let us say the probability is 0.2. So your probabilities are now 0.4 + 0.4 + 0.2 = 1 This is very important because these are known as prior or anterior probabilities. In this case they are subjective prior probabilities. There are also objective prior probabilities. Prior probabilities are assigned before the beginning of the event and are set on the basis of the best known information at that time. Thus they may not be 'truth' , whatever that means. The crux of the Monty Hall problem is what happens next. The traveller turns say left and the probabilities are now changed as a result of better infomation. This is also the key theorem that Bayes introduced in the early 1700s and Laplace developed in the late 1700s. The probabilities are now P(turn left) = 1 P(turn right) = 0 P(drop dead) = 0 But this cannot occur until after the event. But there is still more about probability. What does the probability P(event) = 1 mean particular in the case of future events, which is after all the reason for doing all this? Well there are several cases and each has a different meaning. If we can take our prior probabilities to be correct then we call them a priori probabilities (Laplace was french) and P(E) = 1 means that the event will (=must always )occur. If our prior probabilities are objectively acquired P(E) = 1 says that the event has always occurred in the past but does not mean that it will always (or ever) occur in the future. If our prior probabilities are subjective then P(E)=1 then it means that we think the event will occur in the future, but again does not imply that it will. As I said probability gets complicated as you go deeper. Finally if there is any more mud slinging you will need to find a new discussion partner.

You need first to understand the word observing in this context means 'interacting'. Any interaction with the outside world, animate or inanimate is classed as an observation.

Rudeness does not improve the validity of your claim. Probabilities cannot be imposed. They are what they are. And yes your analysis is flawed. No, of course you did not say that, I did. Your analysis is flawed because there exist possibilities you cannot exclude. For instance your traveller may drop dead at the junction and simply not proceed. There is always a finite possibility of this, and therefore a finite 'a priori' probability (do you know what this means?)