studiot

Well I don't agree with either of you. In my view the opening post itself was clear enough, although I will accept any clarification by exchemist as to what he actually meant. I understood it to mean that: An article was published that declared in exactly these words "all knowledge is..." In my dictionary all knowledge includes scientific knowledge, including established facts such as Pythagoras' theorem. The article further states that political correctness is being applied to a particular course in a scientific subject, to whit Chemistry. exchemist appears to me to be asking if this is sensible (science) and providing his opinion that this situation is 'bonkers' I agree with him. In extending these simple observations to the countries and places where they speak different languages I respectfully suggest that both CharonY and Arete are the ones who have 'missed the point'. In particular the question of those who do not speak English is a red herring. Said person must speak his or her own language and the exam in his or her country will not be in English but in his or her own language. So why should they not pass the exam ? No, I would not expect them to come to an English speaking country and take the exam in English and pass. Would you ? Did you read the words 'perhaps we should' at the beginning of my sentence indicating Swiftesque irony ?

Fly though a cloud ? No, the body was made of balsa wood. The twin engines were made of metal and I presume the fuel tanks and lines.

Forgive me but I thought Mendeleev's original wrtings were in a mixture of Cyrillic for the text and Latin for the symbols as most of then known elements had Latin names.

Please give me strength. Go back to the two correct things you said which were 1) The air density inside the balloon is lower than the air density outside. 2) The air pressure inside the balloon is greater than the air pressure outside. ( But - my comment - this cannot be true at the opening or the higher pressure air would simply exit the balloon. This is why the given analysis sets the pressure at the bottom to be equal inside and outside ). Now consider a Montgolfier design; a ball shape with say the bottom 40% cut away to form the hot air entry part. The remaining of the lower hemisphere wiil be curved in such a way as for the higher pressure at the bottom to push down harder on it than the lower pressure pushes upwards further up. At the equator of course the net force is horizontal inside the balloon.

So you are claiming that a pure tension structure made of flexible fabric can support compression ?

I fail to see the relevancy of this to either of my comments. In particular would I be considered racist if I reported a black precipitate on passing hydrogen sulphide through copper sulphate solution ?

The Montgolfier shape is not the only possibility. Cylindrical hot air balloons work perfectly well too. What, by the way, is the point of pushing up on fabric at the bottom ? It will simply buckle or rumple under even the slightest push. It is vital to maintain tension in the skin of any balloon, open or closed. There is even a discussion of this in the article I posted. What a pity you don't like it because it is a nice piece of uncomplicated mechanics that is not often taught these days.

Make that check out to studiot in sterling please. Did you not read the associated text. Only the Carnot includes adiabats

All the basics necessary to compare the stirling (Ghideon please note correct spellung - sterling refers to money, gold and silver) cycle with the carnot cycle are in this excellent extract. It also provides conventional labelling to aid common discussion.

The most successful warplane of all time was made from wood. I know that's dead, but still it's worth mentioning.

I must say I fail to see what is subjective about the result of adding silver nitrate solution to sodium chloride solution. Perhaps we should ban such experiments since the majority of salts are white so white precipitates (if any at all) will be in the majority.

So what does the 'force of high pressure' act on considering the bottom of the hot air balloon is open oh wise one ? To make it quite plain it has no bottom.

No my decision is final in all cases.

I think the OP should be the judge of what they want or don't want, not you. In fact this text contains nothing more than can be found on the lower secondary school syllabus (GCSE in the UK). The reason that the pressure at the bottom equals atmospheric is that a hot air balloon is not sealed. There is a hole at the bottom so the pressure in the balloon must equal the pressure outside. This restriction is not necessary for a sealed balloon which can be at considerably higher pressure all round and considered as a rigid object for analysis purposes. It does show (without PHD level stuff) that there is a lift force pushing up on the inside of the upper part of the balloon. It doesn't mention this in the article but this force is not applied at the 'centre of bouyancy' , which is where the bouyancy force acts and so is important in considering the stability of the system - something I chose not not mention before. The textbook deals with equilibrium and centre of bouyancy elsewhere and I thought that a subject beyond this thread.

Thank you for bringing S Constructivism to my attention. Looking it up on Wikipedia it certainly does not embrace all scientific knowledge, let alone all other types of knowledge. In fact it seems very limited in its scope, far more so than exchemist's original quote (why did you not acknowledge it ? I had to waste precious time finding it in the thread.) . So I would say it was a fair attempt at noting that human observations tend to be some way from truly objective, despite our best efforts to the contrary. So it is always refreshing to see someone doing his or her best to act objectively.

Well done you have the right of it. +1 A hot air balloon will only stay inflated of the internal pressure is greater than the external pressure, otherwise it will collapse. I'm sory but this analysis is just plain inadequate. Here is a standard analysis of the subject @Saber please ask if you need anything further.

I still don't see any reply to my comments, which is a pity because you are travelling down the wrong path, pulling everybody with you. The outline scheme of though in analysing the relativity of the light clock runs as follow. The light clock is a self contained unit the output of which is not tracking the light path but a 1 second 'tick'. This tick measures 1 second when compared against the tick used by the stationary observer's ie the two clocks stationary are side by side. When the clock (and it is the whole clock not part of it) is in motion relative to the stationary observer, the observer receives signals of the number of ticks on the moving clock. When he times those ticks using his own clock he finds that they are longer than those of his own clock. This difference is calculated by relativity using distance information derived from the moving clock's motion. This is why others have said the primary observation is time dilation here. Incidentally you have been stridently claiming that the angle of incidence within the clock does not vary. This is not observationally true. The correct analysis, backed up by experiment, is not normally taught in elementary Special Relativity and leads to a formula for transforming between the angles of incidence observed by a stationary observer, θ, and by a moving observer θ', which are different, just as with the time ticks. The invariant in this case is the number of ticks. [math]\cos \theta = \frac{{\cos \theta ' + \frac{v}{c}}}{{1 + \frac{v}{c}\cos \theta '}}[/math] This formula is also associated with observed frequency changes to the light, known as the radia and the transverse doppler effects.

Good question. +1 Think carefully about your definition of bouyancy force.

That's exactly what is shown on the graphs I posted. What I actually said was the The absorbtion coefficient of the big carbon dioxide peak is shown on the first graph is shown to be at least two orders of magnitude, (nearly 3) greater than the 15 micron one.

Not quite, the hot air ballon is a special case that is more complicated. Lorenz' analysis applies to rigid bodies. The hot air balloon is a deformable body. I can explain it fully if you can do high school maths for science ? But it is basically due to the fact that the pressure inside a hot air balloon must be greater than the pressure outside, except at one point. Can you see why this is true ?

Thank you for clarifying that, it wasn't totally clear. However here are two graphs The first shows the clear big carbon dioxide absorbtion peak at 3000 nanometres. The second shows where that falls on the ground emitted radiation spectrum. As you can see at normal temperatures nearly all the absorbable IR energy is of way too long a wavelength. The bottom black line is 0 C and the second one up (red) is 20 C.

@Otto Nomicus I'm sorry you chose not to respond to my offer so I will leave you with these thoughts as some dubious statements have been made on both sides, perhaps you are confusing each other. Firstly if you are going to accept that a light path that measures 1metre between two points in all in the same frame but say 1.3 metres in another frame then you must also accept that the time of transit of that different distance must also be differnt to maintain the principle of constacy of the speed of light in all frames. Secondly the light in a light clock should not be thought of a constant stream of light. There is no way you can observe the time of transit of such a light stream. Light clocks use light pulses which are measured at the source and receiver but not in between.

The problem is that you original sketch is fixed in your mind, but it is a flawed depiction of what happens. Thus your text description is also flawed. I will see if I have the time to produce an improved one. By the way you don't need a laser to show this, in fact it is can be less than helpful. Einstein didn't know about lasers back then so he constructed his light clocks using ordinary sources and light pulses. by which he meant the leading edge of the light 'signal'.

This fits with a worked example I was thinking of posting, if anyone is interested. The thermal efficiency works out at 19% and the last figure , the work ratio at 0.133 This work ratio figure is useful as it tells us exactly how much work we can get out of such a heat engine at maximum compared to tthe total work done during the expansions and contractions. @Tom Booth Do you understand that Carnot conceived his cycle using equilibrium processes which are regarded as maximal. The stirling cycle is of interest because it is one such that can theoretically approach this maximum by arranging parts of the cycle when no work is done (ie at const volume) and parts at equilibrium (the isothermal parts) ?

I sincerely hope it is not too complicated for us since it human input needs to be resolved urgently. I hope you understand the difference between weather and climate. Weather is what happens on a day to day basis at a particular location. Climate is the yearly pattern of weather across large regions of the Earth. You are also correct that human generated pollution has become a major problem in other ways than climate change and also need sorting out. But that is not the topic of this thread and should be discussed in a thread of its own. This also applies to your other geophysical questions, which again merit their own threads. There have been many attempts to explain the Earth's magnetic field and we are getting nearer one that fits all our data as we learn more. Do you have access to library facilities ? If so I can recommend suitable sources from modern researchers. But please start your own thread about this.