studiot

Not convinced, about the HCL, I thought that bleached wood ? But certainly it is a dangerous substance to be treated with respect. Ammonia darkening of wood is a well recognised process on the other hand. You can see this just by using ordinary household ammonia and scrubbing a wooden floor. https://en.wikipedia.org/wiki/Ammonia_fuming http://www.nzdl.org/gsdlmod?e=d-00000-00---off-0cdl--00-0----0-10-0---0---0direct-10---4-------0-1l--11-en-50---20-about---00-0-1-00-0--4----0-0-11-10-0utfZz-8-10&cl=CL2.19&d=HASH0151caf30a244bb2ecd8f91b.5.4&gt=1

Hi again. Thanks for explaining your requirements. Sadly, I'm not an expert on higher order logic and it seems unlikely I'll have time to become familiar with it over the next few months. So I'll be bowing out of this conversation. Sorry I couldn't help. But you did help. 🙂 Thank you for picking out an example of the wider scope of English over Maths. +1 Truth values are not the only values in English and even these are not fixed. For instance the apparantly mathematical question "How many sheep are in that field ?" Say the answer come's back as 13. But I didn't include the information that 5 of these sheep about to lamb. Tristan's self referential question also includes (amongst other values) comic value in English.

#That is an unsound circular argument. The universe is only finite if there is an 'all' to the hydrogen. Note this condition is necessary but not sufficient. So you can't say the universe is finite because there is a finite amount of hydrogen. But also consider this since you wish to quote thermodynamics: Take the numbers 1,2 and 3 ? Do you consider that each of these numbers contain different information ? But the sequence 1,2,3... is infinite so do you consider that there is a finite (ie limited) amount of information in the universe and so must be unable to contain any number larger than some integer ?

Hell yeah! It's a wall against personal demons. +1

Don't worry, the good 'Prof' has only one post left.

I dunno about always, but this is an incredibly profound yet often overlooked statement. +1

Please explain why physical chemistry and what axioms you are proposing. Then it might make some sense to DIm and to others less bright like myself.

I can't see how you can learn much engineering without learning and understanding a good deal of Physics. Simple things like the difference between a Force and a Pressure. Simple things like a fluid going round a corner or bend in a pipeline exerts a force that can be sufficient to need thrustblocks. Failure to understand this and use these can have spectacular results as the engineers who flooded Harrow Hill in London with bentonite found out.

Not sure that either of those two expressions are coordinate free. Just they are true in all coordinate systems. Is dF the divergence of a field ? In any event I was talking about something much simpler than this. 1) It is fashionable to teach euclidian geometery by vectors these days. This adds a coordinate system, only neccessary because of the use. A parallelogram has the same area whether calculated by Euclid or by vectors. 2) Relativity only requires a metric containing linked interval invariants. Yes both of these can be done by theory using coordinate systems but this is surely going against the idea of the simplest possible theory for the job in hand. Here is an example. Speed v velocity. Speed He was driving at 175 mph He was driving along Pendine sands at 175 mph Both are true and contain enough information to make sense. He sailed from Cadiz at 4 knots This could be true perhaps lacks enough information to make proper sense Velocity He was driving west along Pendine sands at 240 mph He sailed S-SW from Cadiz at 4 knots More information makes more sense So English usage appears to conform to Ockham, and need not be scientific. Once again I refer to what William actually said.

Perhaps someone could explain to me why we hang on to Ockham's Razor yet don't apply it to situations in pure Mathematics or Physics such as Relativity where the apparatus we teach and use contains more information and structure than is necessary. I am thinking about the 'automatic' but unneccessary use of coordinate systems in geometry? Ockham was not a scientist. So why confine the razor to something he had never heard of and did not introduce it for ?

Can be significant, not are significant. read this realistic american article. http://daytonthermalinspection.com/2017/09/27/the-tale-of-two-comforts-complexities-of-heat-pumps/ One other point to consider with solar PV is the replacement cost of storage batteries, they are not cheap. But batteries are essential in most PV systems as the panel output is low voltage and thus suffers high relative resistive losses if used for directly for heating as it must be high current. One possible future use of PV that occurs to me which makes a lot of sense, but has received little if any coverage would be charging the family electric car. After all, electric cars are the coming thing.

Fair enough if you are only considering linear momentum. I'm sorry if I misunderstood, as Fred keeps reintroducing angular motion even after repeated telling that this is irrelevent. Certainly my thoughts are that if you allow scattering before the impact of the photons ther is no point in using a laser You seemed to imply this when you wrote, perhaps I misunderstood again. Further I don't see that scattering after the impact is relevent since any change to the target's momentum will already have occurred. So why is scattering not a red herring ?

I like to have my own copy of things. But I also thought you would understand more. I don't know where you found that article, but it is part of the Stanford Encyclopedia, which contains many many articles, with a choice of formats. Paid members may download any of these. Like our member with the cigar, I support Wikipedia with a few dollars a year and thought I would like to support the Standford project with a few dollars more. Neither are greedy unlike some sites. yes, I was going to ask about this. But I don't see any conspiracy background, just a member whose first language is not English struggling with a translator. 🙂 Yes that is also my understanding so far.

Thank you for that knowledgable amplification.

How do you address my point about two of these being irrelevant ?

Glad my reply was of some use. How did you get on with my little quizz ? It was designed to demonstrate something very important. Mathematics uses the + and - symbols for two different things. This sign of something which you asked about - which is a property of that something and addition/subtraction - which is an operation or process on that something Many people get confused about this basic point.

It would seem to be that however small the risk might be it is not insignificant since the BBC recently highlighted cases of misdiagnosis and I find on looking for them that there is an american standard on the subject. https://pubmed.ncbi.nlm.nih.gov/25944182/

Still considering basic mechanics. You have correctly distinguished between rotation and spin. Do you understand the difference ? Gaseous atoms do not rotate. But they do spin. They have no internal axis to rotate or tumble about, unlike molecules. They do not rotate about external axes because their motion is random. Gaseous molecules can spin, they can also rotate about non centroidal axes within the molecule, but they do not rotate about external centres as their motion, like that of atoms is random. You should also reconsider your proposal for momentum transfer in slowing things down. The direction of impact in relation to the centre of rotation will determine its ability to affect rotation about internal or external axes and to affect spin. However this is just a coarse classical start. The next step is to realise that with atoms and some extent molecules the mechanics is more subtle because both have structure. Since in a semi classical analysis you have spinning electrons orbiting a massive nucleus, like the Earth and the Sun, you have angular momentum for both spin and rotation combined. This situation becomes at the same time both simpler and more complicated/difficult when you consider photon atom/molecule interaction because the scale of things is such that you need to move to quantum mechanics to obtain correct models of the interactions. It is these interactions you need to consider here. However it is you proposal and your thread so it is up to you to work through the detail, rather than just guess.

What is hyperloop please?

Does it ? Take a ball such as the Earth, which has a spin about its axis and a rotation in the plane of the ecliptic. All rotations are planar motions so adding or subtracting momentum perpendicular to this plane make no difference to the rotation ie no braking effect for 2 of the four possible directions. Also 'tapping' the Earth at the north and south poles, along the line of the spin axis does not affect the spin. That leaves 4 direction out of 6 as I said. Have you not mentioned spin reduction here ?

I suppose that depends upon which presentation you download did you download the HTML version ? I said I downloaded the pdf presentation, which comes in two flavours. US and A4 paper sizes. I chose A4, which is clearly paginated, as are all pdf documents as far as I know. Anyway, since I can't copy and paste without loosing the the symbols from the pdf, here are a couple of screenshots, note the pagination at the bottom corners. Thank you again for the reference excellent and seems bang up to date as practicable.

Lots of combinations work well in milder climates. The real point is that users want/need the heat and power mostly in the winter and also the dark.

You keep mentioning "all 6 directions" as though 6 was some magic number. Do you not realise the basic mechanics that momentum directed along 2 of those 6 directions cannot affect spin? You are just throwing things out without thinking them through.

No one said that it is not a beneficial or desirable process. But this is a technical discussion about technical issues involved in achieved a desired objective.

Rubbish. I doubt we shall ever know what the first human belief was. It may have been "I am going to have roast mammoth for dinner"