studiot

Please note That all velocity is 'relative'. 'Velocity' without a reference point is meaningless. Trains were the fastest transport known in Einstein's day. Maxwell's EM theory actually obeyed the 'principle of relativity'. It was Newtonian mechanics as embodied in the usual statements of his three laws that did not.

Thank you both, the paper in Ghideon's link is worth discussing and we can all help each other understand it. My comments were not adverse criticism. I would just like to comment that the second Law refers to cyclic processes, both equilibrium, reversible and non equilibrium, non reversible. The key is the cyclicity. The integral in the inequality is a cyclic integral. It has long been known that it is possible to pick out situations within a cycle that do not conform.

Don't give up, you have had the same thought as one of the greats of 20th century maths. Kolmogorov So welcome and keep thinking. Basically Kolmogorov is saying that a number is random if the shortest algorithm (read what you meant by describing a number) for arriving at that number is writing down the number itself. So for instance 1234567890 and 0 and 1 are all random numbers.

Hope they are not looking over your shoulder then.

I'm having a little trouble sorting the sheep from the goats in this paper. 1) Can you explain why their Carnot Cycle is in the wrong order ? It should be two expansions followed by two compressions but their diagram a shows the expansions and contractions alternating 2) In the text they refer to work extracted, but I can only find details of work done on their particle. 3) I'm interested to learn how resistance free (= frictionless) adiabatic processes can be done on a charged or charge separated particle in water where surely Van Der Waals forces must operate. 4) What exactly is expanding and contracting in a single particle ? 5) From what I can gather they are saying that whilst a single measurement of their single cycle efficiency parameter can exceed Carnot, the statistical average either of infinite measurements on one particle, or one measurement on infinite number of particles, will equal Carnot. This of course implies that if some measurements are greater than Carnot, some will be less.

Some might find these quotes on the subject of interest. @Tom Booth you might like to reflect on why neither heat nor work can be considered to be properties.

Thank you for pointing me at material I need to brush up on. +1

May I add the word sufficiently ? If the material of the planet is sufficiently fluid, yes. Note also that the pull will always be present, regardless of the state of the planetary material. Ice for instance will flow under quite small pressure. So if an ice planet is large enough the gravitational pull will be large enough to create flow pressure. But there are other mechanisms at work as well. Some of them in conjunction with gravity, some of them opposed. For instance if the planet spins the pull experinced will vary from equator to pole. Also if the planet surface is subject to weathering, eg by heating and cooling causing cracking, then gravity will pull the broken off pieces into the concavities. Good question, @Saber . +1

https://www.bbc.co.uk/news/business-64402524

I am not convinced that the US government really cares about ordinary people any more than our UK one does, or about the damage that could be caused to them. I wonder if they were really wanting the thing to land on water, rather than land so that the bits would be less damaged by the impact. They are certainly scrambling to find them in the nearshore ocean.

Preamble I'm not sure if you have Scottish roots or what, but my experience of Scots abroad is that whilst they are warm and friendly in their homeland, they are more often than not defensive and prickly outside it. So I don't want to upset you by my commenting on this. All credit to Scotland to win (retain) the Calcutta Cup yesterday. I find the English establisment unreasonably big headed about its position in these competitions and so like to see a few tumbles. Now my comment In this very thread I was passing some information to joigus about a very English saying concerning "a bull in a china shop". Contrast this with the contents of your PM exchange (no I don't want to know the details).

Difficult indeed. Yes difficult indeed. Which is why it is such a shame that you threw your toys out of the pram at a critcal moment when I had just posted the diagram showing how Carnot overcame that difficulty. Again a pity that you did not complete the translation of his works, putting that hugely insightful statement into its proper context.

Have you studied baby/mother communication ? And who teaches (most) babies to cry ?

I found this RSC article about comet chemistry (in pdf 15 pages) https://royalsocietypublishing.org/doi/pdf/10.1098/rsta.1988.0064 There is a useful table of compounds expected. and also this newer article about comet spectral analysis. Curiously the attribute acknowledge a green oxygen line. https://www.aanda.org/articles/aa/full_html/2019/04/aa34357-18/aa34357-18.html

You have elephants in your stores in Spain ? We have bulls in ours.

Thank you for that childish personal remark. Although you know next to nothing about me, you have managed to teach me something. Here it is. I thought I would follow up on your Google remark so I typed in "xxyyzz" and should not have been suprised to find that Google will nearly always return some sort of result - just like a working calculator will always display something, even if it is GIGO. https://www.google.co.uk/search?hl=en-GB&gbv=2&q=xxyyzz&oq=xxyyzz&aqs=heirloom-srp..0l5 Apart from the music hots there appears to be a maths course on the subject and it apparantly has applications in Rheumatology. Sleep Well.

Sorry, that makes no more sense than the original statement. The first step always produces an isotope of something.

Of course it does. I am not saying that invalid means useless (see hogwash). But my development is to show that it forms an upper bound. Lots of posters here have offered various parts of the thinking development of this, including yourself. Since Tom rejects the whole caboodle, I am trying to offer these parts in a logical step by step order. Sadly everyone but Tom seems to understand that. And if he is genuinely doing all that work over decades then it is a shame for him it will ultimately be to no avail. I have not yet got into state variables, reversibility or the quasi-static concept and their implications for the discussion.

Thank you for the reply. I wonder what you mean by daughter isotope ? Are you using this definition ? or are you meaning that the 'daughter' must be an isotope of the same element as the starter ? That is the only way I can make sense of this absolute claim Because clearly all decay is to an isotope of some element or another.

Would you please explain that statement in the light of this diagram ? (After Semat.)

Actually I did, but you didn't completely read what I said, any more than you did the first time round. I didn't mention 'limit' or 'hogwash' and most importantly I didn't say that the Carnot formula is invalid full stop. I even quoted the exact passage for you and I am not going to do that again if you can't bothered to read that short passage to the end. The standard engineer's formula and analysis for elastic beam deflections is invalid for wide beams. In other words it only applies to narrow beams. That is why engineers use a different analysis and formula for the deflection of wide beams and narrow beams. No the Carnot formula is not hogwash if used for the purpose for which it was intended. I don't like to use the word limit because the word limit has a variety of meanings, some of which would be contradictory if used in the wrong place. A limit may be achievable or unachievable in both mathematics and other sciences. The only place it is used in Thermodynamics that I can think of is in the thermodynamics of chemical reaction rates and is used to define something called 'the limiting rate step'. In this instance it does not indicate the unachievable. So, if we were to call the Carnot formula a limit then would would be using limit in two contradictory ways within one discipline (thermdynamics). And that would require the reader to make the distinction.

Is (the) Carnot efficiency [limit] (formula) valid? No? My impression has been, that as a limit your answer(s) would certainly be "yes". Even perhaps an overly generous approximation. I certainly never imagined it was an exact representation. But certainly as a limit on the actual efficiency of any REAL engine it is considered absolutely valid. If therefore, no engine can exceed that limit, no engine can exist which does not emit "waste heat". I've watched dozens of tutorials and solved dozens of sample problems on how to use the Carnot efficiency equation and what it means in terms of real world applications involving joules of heat in and joules of waste heat out and joules converted to work. So, what do you mean by "invalid". Just a quick answer before I turn in for the night. This is a much better way of arguing your challenge. You are actually asking why someone says something. First we start with the premise that Every real world engine has an efficiency. So the issue becomes "How to calculate that efficiency ?" I have established that the Carnot formula only applies to an imaginary engine. So why would anyone expect it to be valid for any real world one ? What you will calculate if you use the Carnot formula will be incorrect for a real world engine. So I have begun the long process of delving into which leads on to "How should we calculate it instead ?"

Good point, but can I add a thought here ? I used Th and Tc to try to keep the nomenclature simple. I also used them as shorthand for source, reservoir etc, perhaps a bit ckeekily. Most cycle diagrams have more than 2 vertices so are usually numbered 1,2,3,4.... These vertices also correspond to definite states, both in ideal and non ideal machines. So perhaps V1 and V 2 etc would be better ? A couple of other thoughts, @Tom Booth Beware of sign conventions. Chemists treat all forms of energy in a positive and all forms of energy out as negative. Engineers (and most phyicists) treat work done on the system as positive and work done by the system as negative ie (the opposite). Both systems have their uses and roots in history. Although Thermodynamic theory was the first discipline to make full use of the new advanced mathematics in the early 1800s I am trying to avoid this part. It is not needed for our purposes. Thermodynamic theory also pays scant regard to time there is no consideration of how long it takes to reach the mentioned states and most thermodynamic maths in independent of time. I am posting this diagram now as the beginning of the next installment. I will explain it later but I have other things to attend to over the next few hours. Meanwhile I'm sure Seth will recognise it.

There are lots of Gwave detector types and some of the sources are known to be moving away at appreciable speeds so it is not suprising that LIGO offer this