 |
Allan Amass - Heat
Your contributors did not define the temperature of a body as a measure of its ability to absorb or give out heat. As a consequence a small body at a temperature greater than that of a large body will always transfer heat to the large body when it comes into contact with it. The driving force for this process is that the TOTAL entropy change, q/T for each body, is positive. The body absorbing heat at the lower temperature therefore shows a greater increase in entropy than the loss of entropy from the body emitting heat at the higher temperature. So heat will always flow from the body at high temperature to the one at a lower temperature.
Brian Cowell - Heat
Enjoyed the programme. I suggested to Lord Bragg in 1999 that the 'Development of Thermodynamics' would make a good topic for discussion.James Prescott Joule was born in the City of Salford. A paper to the Royal Society had only a brief summary published. He wrote "I was not surprised, I could imagine those gentlemen in London sitting around a table and saying to each other: 'What good can come out of a town where they dine in the middle of the day?'."Clapeyron, Rankine, Caratheodory deserved a mention (time or my memory?) in my view.Initially, whether heat just flowed through an engine or some was extracted was difficult to determine experimentally. Newcomen's engine was about 0.5% efficient so 99.5% flowed through and would have required great accuracy to see a difference. Watt's engine was about 2% efficient, whilst the high pressure Cornish engines of Jonathan Hornblower the Younger and Richard Trevithick were 8% efficient.Incidentally, Pope's verse on Newton mentioned in a book by Lord Bragg was followed by Squire's on Einstein which I deplore. Better would be:"Merc'ry's path though was an aberration,God decreed, 'Let Einstein solve th'equation.'".
Moore Le May - Heat
Might be interesting to do a program on entropy and in particular the mathematical and probalistic implications leading to information management and the work of Shannon
Hiram Baddeley - Heat
You barely mentioned von Helmholtz, The professor of physiology in Bonn, who published his book 'The Conservation of Energy'( 1st Law of Thermodynamics) which postulated the link between the energies of motion, heat, light, electricity and magnetism 4 years before Thomson(Baron Kelvin)published his cardinal paper on the Laws of Thermodynamics, entropy and absolute zero temperature.There is controversy about who coined 'Heat Death of the Universe'.Helmholtz who treated frozen casuaties when he was a Prussian army surgeon seems the most probable. He finally became Director of the Berlin Institute of Physics; Hertz (radio) and Max Planck (energy quanta) were is students and co-researchers.From 'Human Energy' in Physics and the Human Body' ISBN 9781438917030
Spamlet: Heat
I was quite stunned when I turned on the radio tonight because I had been in the middle of an email dialogue over why in all the years of debate about climate change nobody has ever bothered to point out to the public the difference between heat and temperature. And then there you were!I have tried to raise this subject a number of times with various global warming pundits over the years but never had a reply. My point is that in all the years of programming over climate change, nobody has ever questioned why we are concentrating on measuring tiny changes in air temperature as the 'proof' of global warming, when this is like looking at your speedo to see how much fuel is in the tank (Except that in our case, the 'fuel' is running in rather than out!).I estimate that it taskes about 300 times the energy to melt ice than to heat an equal weight of air 1C. Yet, while ice is disappearing at a rate of knots everywhere, the public attention is diverted on to the false indicator of air temperature, which is being held back by that melting!
Richard Turner - role of Phonons in Heat conductio
I don't know whether there is any opportunity to update In our Time programmes, but this one could with advantage have mentioned Phonons (see Wikipaedia article plus numerous others in Google".
Jim Rait.... Heat
I was intrigued by the interaction of science and technology in the programme and after Melvyn Bragg's comments about technology getting ahead of science. There is a quote by Danny Hillis “My definition of technology is ‘the stuff that doesn't really work yet’”.[Danny Hillis is cochair of Applied Minds, a design and invention company.] The steam engine seems to reflect this... we had fire machines that worked but not that well Then as the thermodynamics began to be discovered and applied we made great strides in moving from "working and just about effective" to "working efficiently and very effective". I am looking at North-West pioneers in aeronautics and we can see the same pattern there, e.g. Cayley-Wright-Roe etc.
D O'Reilly Heat
The concept that heat is exists only as an exchange of energy is current in certain circles. This seems to be taking rejection of the caloric theory rather too far.I was hoping that the distinction made at one point between the measuring of temperature and of thermal energy would avoid this fashionable canard but it wasn't to be!The difficulty is not trivial, temperature as a measure of how energetic the heat in a body is is utterly crucial to thermodynamics and the phenomena it describes.
James Baring - Heat
I felt the team struggling a bit to explain this subject, and that was good because it is very difficult. The discussion was far from fluid but none the worse for that. Entropy is a tougher subject than many suppose and thermodynamics are subject also to the constraints of a universe in which gravity has played an opposing role, the two between them constructing the world we observe and its evolution.The final phrases about the paradox which leaves us a conundrum with respect to determinism were appropriate, but the solution comes only in a dimensionally extended model.Right now TV viewers are being assaulted by dear Tony Robinson struggling with what he sees as a perverse paradox of life rising to complexity and sophistication because of catastrophes. "We are only here by chance!" he exclaims at the opening of each episode. If he tried saying that to himself differently with emphasis first on "We", then on "only", then "here", instead of always on "chance", he might get an insight into the science he presents so clearly but without understanding. That life is in existence is inevitable, that it is here and is us at this time is dealt with in the various anthropic principles. The concept of chance in the universal context of celestial dynamics is very different to our notion of it in our everyday lives.
Barry Charles Shurlock
Apart from refreshing something I learned a long time ago at university, the programme on Heat confirmed what I am sure is true, namely, that learning about science is so much more interesting when it is presented with an historical thread. One of the other subjects I studied was quantum mechanics: the lecturer started by holding up an A4 sheet covered with mathematical equations and commented: 'All you need to know for this 8-week course is on this sheet of paper.' He then proceeded to present the dry essentials of the subject. How much better if he had pursued the ideas that had led to quantum mechanics - the personalities, the wrong turns and the puzzles, as well as the successes. Now, 45 years later, I revile all attempts to present the humanities and the sciences as two cultures. As Melvyn Bragg amply demonstrates, any enquiring person can find great pleasure in grappling with the ideas of thermodynamics - as well as exploring the worlds of Jane Austen, Swift, Pope etc etc. If science educators were to follow his style we might not always having to be sell science to reluctant pupils!
Jane - Heat
I do think this is a wonderful programme and its weekly forty five(ish) minutes are sacrosanct time. I've occasionally seen the question asked "why is the programme called 'In Our Time'"?. I would like to request more programmes on contemporary and also universal subjects. I've noticed these tend to get a good response and give us something to really get our teeth into. 'Heat' today was super. There's a function of heat which has me shaking my head in wonder every time I think about it, the temperature of the physical body held constant by homeostasis - we tend to take it for granted but it's an utterly incredible phenomenon. (Tell that to your dog next time you take him to the vet's!) Really enjoyed today's very clear discussion and the last sentence was brilliant orchestration, deliberate or not: "that there's a direction to the universe and that it will end in fire"......mmm... many thanks as always and very best wishes
Tom Milner-Gulland - HEAT
The notion that heat can only be detected in the form of an exchange is fundamentally at odds with the notion that it can be stored, as energy, in, for example, the form of chemical bonds - a notion which turns out to be a sine qua non for the upholding of the second law of thermodynamics.The issue is one of material properties that fall within the Newtonian ambit - particle collisions, by which, as Newton established, serve to carry a particle's momentum in the general direction of away from its source (rephrasable as one of the many versions of the second law of thermodynamics) - and material properties that do not. In the latter, energy is stored and released (often spontaneously) through processes not hitherto modelled in any physical theory. Thus, with energy sustaining the fabric of material substance - and, therefore, being more a mere metrical term - there is a purely qualitative component to heat which is inherently bound up with the variety of chemical properties in the universe, and the idea of the heat death of the universe is undermined by the universe's being inherently - and mysteriously - regenerative in regard to chemical substance.
John Lamper - Heat
I thought that the programme was thoughtfully put together and gave a comprehensive view of the subject. However, the analogy Joanna Haigh used to introduce the concept of entropy fell into a common trap by not going on to apply the analogy to things that happen to molecules. A neatly-stacked pile of bricks being pushed over does of course lead to an increase in disorder (of the bricks), but there has been no appreciable change in the entropy of the system, as nothing has changed at the molecular level. Perhaps it would have been better for Professor Haigh to have gone back to the discussion of change of state (ice > liquid water > steam) and explored this in terms of the increasing number of degrees of freedom of the water molecules and the ways in which they can 'store' energy. I fear that this is a trap that some teachers of A-level sciences may fall into, as this type of analogy is so commonplace. Although the rules of thermodynamics describe macroscopic properties, I have found that it is much easier(!) to explain entropy starting at the molecular level. One textbook I can recall, in an attempt to bring entropy closer to home for a teenager, gave two illustrations of a bedroom - one tidy, the other in chaos - wrongly claiming that there was a higher entropy resulting from the disorder. Set fire to the bedroom and there definitely would be an increase in entropy!
Sandra Walker. Fire,heat and light
Hasak mentioned that heat ceased to be one of Lavoisiers material chemical substances - apparently as a result of research into fire,heat and work. I have often wondered how/why light also changed from being a material chemical substance
dave souza – Heat
Why was entropy described as a disorder? It's a bad and confusing analogy rooted in 19th century concepts of energy, and the example given shows how confusing it is. If a tower of bricks ("order") collapses ("disorder"), entropy increases. However, if bricks in a chaotic heap ("disorder") are laid neatly in rows on the ground ("order"), entropy increases. The increase in entropy is due to the bricks being lower, and losing the latent energy of gravitational attraction on available height. The appearance of "order" is entirely coincidental.
D O'Reilly Heat
Excellent programme; for 45 min I think it reached the limit of what was possible.What could be added was that the developement of heat theory was based on ideas on mechanical motion originating with Copernicus, Kepler and Newton who laid the theoretical foundations which the 19th century developed to the point of statistical mechanics.The programme might also have mentioned that these 19th century developements were already pointing to quantum mechanics in consequence of anomalous observations in specific heat measurements.Brilliant though 20th century physics was, it did not emerge from nowhere, it is part of a continuous thread stretching back many centuries.
Brian Faulkner - Heat
I have just enjoyed the programme on heat. I was instantly reminded of the song by Flanders & Swann about the first and second law of thermodynamics in which they correctly say that "you can't pass heat from the cooler to the hotter, you can try it if you like, but you'd far better notter"
Mike Bell --- Heat
Melvyn,I have just heard the trailer for your programme giving the credit to James Watt for inventing the steam engine. The first proper reciprocating engine was built by Thams Newcomen - all Watt did was to make it more efficient (by using an external condenser). It was Newcomen, building on the work of Savery, who realised how to use the conversion of water states (from steam back to water) to use convert heat into mechanical work. Watt just did it much better, then Trevithick did better still.
|
|
