exchemist

Do you really think a millenium is the same as forever? You wouldn't be much good at geology.

I don't think your last para is entirely right. HFCs, which have been widely used to substitute for the ozone-depleting CFCs and HCFCs phased out under the Montreal Protocol, are actually very potent greenhouse gases. So now there is a drive to replace these too as refrigerant fluids, with things like ammonia, CO2 and hydrocarbons.

My understanding is that a modern Li ion battery has a charge/discharge efficiency of 80-90%. 75%, let alone 67%, seems low to me.

What sententious garbage. Freedom of speech does not require that you be free to talk crap wherever you like.

I'm terribly out of date I'm afraid, as I have not used a vacuum line since my university research, over 40 years ago. I recall being impressed with the mercury diffusion pump, though it was a bastard if any gas got past the liquid N2 trap and reacted with the mercury. I had some trouble with nitric oxide, if I remember correctly.

If you jerk a rope, you displace a portion of it upward from its lowest energy state, which means you put gravitational potential energy into a section of the medium (the rope). The portion of the medium that is displaced upward then travels, but the energy is still at all times in the medium, just not always in the same part of it. In the case of the photon, the energy is in the travelling disturbance in the electric and magnetic fields. You can certainly say the photon is the energetic occurrence, but the energy is still in the fields. Think what happens when a photon is absorbed by an electron in an atom. The changing electric field of the photon creates a forced oscillation in the electron (using classical language, more properly a "transition dipole moment") that moves it to a higher energy orbital. So it's the oscillating field that gives up energy to the electron. It's essentially the same as happens in the antenna of a radio receiver, but on a smaller scale.

But be careful. Notice Einstein spoke of wave-packets, not energy packets, in line with what I said previously. The light quantum refers to the observation that the energy in light is only transferrable in discrete portions, which he called quanta. That does not mean light is "made of" energy. E=mc² is the simplified version of a longer formula: E² = (mc²)² + p²c², in which p is the momentum of the entity in question. For an entity at rest relative to the observer, p=0 so it reduces to the familiar formula. However for a photon, this does not apply. On the contrary, for a photon, m=0, so the expression reduces to E=pc. (If you apply de Broglie' relation to that, by which p=h/λ, and use the fact that c=νλ, you get E=hν, Planck's well-known formula for the energy of a photon.) I agree "stuff" is not a precise term. What I was trying to say, in colloquial language, is that energy can't exist on its own, any more than momentum can, or electric charge. None of these is something you can isolate. You can't have a jug of momentum or a bottle of electric charge. They can only exist as properties of some physical system, by which I mean one or more material entities (whether QM or classical) or fields. A wave is a system that in general comprises a medium (which is physical, i.e "stuff"), physically disturbed from its equilibrium state, with the result that the disturbance propagates through the medium. To disturb it from its equilibrium state requires an energy input, so yes, a wave has energy in it. An EM wave is a bit of a special case in that the "medium" consists of electric and magnetic fields which oscillate. But fields are physical too: you can get a spark from the stored energy in an electric or magnetic field under the right conditions e.g. the pop you hear when the older type of electric train suddenly cuts off the current in mid-acceleration, due to the collapse of the magnetic field in the windings. The energy is a property of the field, not something in its own right. In summary both entities with mass and waves "have" energy, as a property, but this does not mean either of them "is" energy.

A photon is not, or should not be, described as a packet of energy. Energy is not stuff. It's just a property of a system, like momentum. A photon is not "made of" energy, it "has" energy - along with a number of other properties. A photon is sometimes described as a wave packet, https://en.wikipedia.org/wiki/Wave_packet , but not an energy packet. Systems that move (relative to others) and have energy will naturally carry that energy with them, so yes, that energy moves, but only as a result of belonging to the system that moves. To describe a photon as moving energy is not correct. Similarly a ball is a physical object - a system. It has mass as one property, and that mass is associated with a rest energy by E=mc². But the ball is not "composed of" mass, so it is not "composed of" energy either. It has both mass and energy, along with radius, colour, maybe spin, smell.......etc. All these are just properties of the ball. It is the ball that you toss in the air, not any one of these properties.

Thanks, very helpful. So, if I try to summarise, as it is impossible to evaluate all drug-drug combinations, knowledge of the mode of transport and mode of action of a drug is used to predict what interactions with other drugs might be expected, and priority is given to checking these combinations. And then, after introduction of the drug, there is a catch-up process, to flag any further interactions discovered in clinical practice. What seems still unclear is what requirements there are, if any, to check out potential interactions as part of the regulatory approval process.

More gibberish. I'm out.

What are you suggesting might have been “deep faked”, then?

As a chemist, I am conscious that a real physicist my pop up and shoot me down, but I think you have to start again with the system as it is after the interaction. Energies, potentials, momenta etc may have changed, so you have a new state, with a new Hamiltonian (a mathematical description of the total i.e. potential plus kinetic, energy of the system) in the Schrödinger equation. In many cases you can work out what this will be from the nature of the interaction, e.g. absorption of a photon by an electron in an atom. But you generally would need to solve the equation again, I think (except I suppose in very simple cases, like an elastic collision or something, where you may get away with just changing the phase.) The relationship between the two wave functions itself won't be probabilistic, since each is a defined mathematical expression. But each expression is a probability-based description of the system.

You can read about it here: https://bletchleypark.org.uk/our-story/bletchley-park-and-d-day/ Though what this has to do with moon landings, or secrets kept by the state. I don't know - unless you mean the Enigma-coded messages sent by the German military.

Is that entirely right? Surely even a single solution to Schrödinger's equation is still a "monochromatic" wave function, describing in effect a probability density over space, rather than a specific location at which the QM entity might be detected. In which case, "collapse" represents detection (or interaction) at a specific location, with a likelihood predicted statistically by the (single) solution (wave function).

Ah yes, the telltale "ya" makes its appearance: in my experience a sign of aggression as a substitute for rigour. Your penultimate paragraph reinforces this impression, being merely a rant against some imagined foes, rather than advancing a coherent argument. But the rest seems close to word salad. This stuff about 3 points on a graph is a clunky pseudo-mathematical way to say something simple, viz. that different parts of your body are at physically distinct locations. You then go on to say something that appears to be simply wrong, namely that sensation is experienced at all three parts of the body simultaneously, when it is a known fact that nerve impulses take time to travel. (By the way, "the proof is in the pudding" is nonsense. The expression is: "The proof of the pudding is in the eating".)

No, you need to present a topic for discussion here, not require readers to click on links to take them elsewhere - and maybe pick up malware in the process. According to my limited understanding of QED, particles are modelled as disturbances in fields. Does your hypothesis relate to how these disturbances arise?

No. And nor do QM entities either, at least in the most prevalent interpretations. The so-called wave function collapse is due to interaction, not necessarily "observation" by a conscious "observer". Observation requires interaction with a detector, but interactions with things other than detectors, i.e. that don't result in observation, have the same effect. According to my understanding at least.

Yes, that's partly what I was getting at: how can energy be orthogonal to space and time? But also, one can speak of two points separated in space or in time, but what can two points separated in energy mean, without reference to the presence of a specified system, for the energy to be a property of? Energy is not free standing: it only exists as an attribute of a physical system.

Yes, Pigliucci and Peter Woit are the people I often go to when I feel I smell bullshit: they are good at cutting through opacity and pretentiousness and seem to have their feet firmly on the ground. Good point about Ryle, though I can't pretend to have studied him.

Plenty of respected thinkers don't consider there to be a "hard problem of consciousness" in the first place: https://philosophynow.org/issues/99/What_Hard_Problem For the little it may be worth, I think Pigliucci is spot-on.

But these have to be independent variables, right? Whereas energy is in general a function of space and time, is it not?

Must admit I can't follow this. Why would a single, seemingly arbitrarily chosen, property of a physical system qualify as a dimension? An event is not a physical system, surely? Distance and time are not properties of physical systems either. And why energy, rather than, say, momentum, or other properties of physical systems? I can't help thinking there is a category mistake here.

From a brief web search on the subject of drug-drug interactions, it looks as if this subject is a real issue in modern medicine and not tremendously well controlled. For instance I found this: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3500158/. While it looks as if quite a lot can be predicted by knowing the modes of action of a given pair of drug on the body, clearly this is not really sufficient. I tried to find out how the regulations for drug approval handle this issue but the relevant pages from the FDA seem not to be readily available, while I could not find anything on the UK's MHRA, apart from the "Yellow Card Scheme", which is for reporting adverse events seen in clinical practice, i.e. after drug approval has already been granted. I'd actually be very interested to see comments from one of our forum experts in this sort of thing. Perhaps @CharonY may know something about this.

Then don't talk gibberish and stick to the topic. What the hell have Siamese twins got to do with either rates of change or the differentiation of planetary bodies? And what the hell do you mean by volcanoes as "retrothrusters"? We're not talking bloody Buck Rogers. Get a grip of your thoughts, for Christ's sake, and stop wasting people's time with this nonsense.

As a singer, my suspicion is that it may have something to do with the vowels involved. I don't think consonants echo very effectively (complex transient waveforms, including a lot of high frequency components). So I think what you hear is mainly the vowels. The sounds that will echo the best will be the open vowel sounds, as these have the simplest waveform (closest to sinusoidal, with fewest high frequency components). The English "I" is a diphthong, consisting of AAA and EEE. The "o" of love is AAAH and the "ou" of you is OOO. AAA and OOO are open, while EEE is not. So in the case of "I", The EEE won't echo very well and the preceding AAA is very short. So you hear mainly the following longer AAA and OOO. At least, that would be my best guess.