sethoflagos

About what, Michel?

THAT makes a difference! (I'll go and sleep on that one. Good night, and thank you again!)

Hmm, it was the wrong question wasn't it. Just really trying to get a feel for what factors dominate the dynamics of 'fluids' that are unfamiliar to me. I'm having difficulty coming to terms with the concept of 'radiation density' in the Friedmann Equation you posted earlier. My mind was forever corrupted by inaccurate explanations of the Crookes Radiometer at school. I can sort of get my head around waves gaining mass by confinement within a particle, and grasp the concept of mass-energy equivalence at an algebraic level at least. But I'm still unable to visualise 'free' photons having a mass density. If it's by some form of confinement, then what's confining them? EDIT: Your post has grown since I last looked at it! Some wonderful stuff there. Yes, degrees of freedom is very relevant to where my head was going - the development of complexity, or some analogue of the progression from simple streamline flow to fully turbulent (locally chaotic/globally homogeneous).

Thanks for pitching your answers at a level that's accessible to the layman. I'll start to struggle when Riemann manifolds and Hamiltonians start being mentioned. Kreysig's Engineering Mathematics didn't cover that kind of stuff. One impression I've got from these discussions is that as we track back to the earliest history, vectors and tensor quantities tend to disappear in phase transitions leaving simpler (to me!) scalar quantities like temperature, density, and (as I understand it - I don't) the Higgs. Is there some sense that 'direction' ceases to be meaningful, or is this just another figment of my imagination? PS. I'm quite prone to saying 'That's the wrong question' myself, so I won't sulk if that's the best answer!

If I was very small and buried deep inside the mix, I guess the concept of an external crust would be simply speculative.

Much like bread dough or cake mix rising? PS sounds to me that you have a decent understanding of the ideal gas laws and thermodynamics. This is excellent for understanding Cosmology. It places you ahead of many members that ignore those thermodynamics. When you get down to it, statistical mechanics is just as important as relativity and particle physics in cosmology. Small advantage of spending much of my 40 year career designing steam and gas turbine based power generation plant, and natural gas compression and processing facilities. Be a sorry state of affairs if I hadn't picked up some understanding of it Now that I don't work full time, it's good to be able to look at some of the more interesting stuff that never made it into any of my past project engineering scopes of work.

It certainly adds an extra dimension to trumpet practice to know that much the same basic equations that describe the isentropic interchange of internal energy and kinetic energy inside a trumpet can also be used to describe the evolution of the universe (albeit with a slightly different cosmological constant - the trumpet universe needs to expand and collapse indefinitely). Isn't physics wonderful!!

I found the Wiese paper off the links on your signature, Mordred. Very interesting. Thanks!! I may be some time.........

I've read a few wiki articles recently, but can't get a clear fix on when the first fermions appeared. Did they 'wait' for enough space to be available to satisfy the Pauli exclusion principle, or did they just appear anyway and perhaps partially drive inflation via degeneracy pressure?

The picture Mordred's post puts in my mind is more of clumps galaxies condensing under their own gravitational force rather like snowflakes forming and growing due to their own forces of attraction in moist air as it rises and cools. Seems to suggest a phase separation between a dispersed, gravity dominated, mass-rich phase of the universe, within a continuous, expansion dominated, mass-depleted phase. This doesn't necessitate 'The Void' blowing through the galactic clusters in any sense, I think. Maybe more just floating in the breeze. And if inflation/expansion is broadly spherical and into 'new space' as opposed to displacing pre-existing space, then there aren't going to be any 'intersections of impulses'. They're forever diverging aren't they? Of course, in no way am I claiming a full understanding of Mordred's post! Just picturing it from a more mundane gas thermodynamics point of view.

To focus on your original question, since we know so little about the initial Planck epoch is there any point in even attempting to define predecessors? The article previously linked by Strange seems to suggest that there are very few quantities to consider. Just a speck of Bose-Einstein condensate (edit) 'stuff' at the Planck temperature crammed into the infinitesimally tiny Planck volume. There's probably quite a few paradoxes at large here, but one that sparks my interest is what's happening to system entropy. If any physical laws do persist back to such phases, I'm guessing the 2nd Law has as good a chance as any. The old definition dS=dQ/T suggests that under these conditions, though the entropy is 'low' (ie compared to later times) it seems that there's a limiting case where no matter how much energy is added to the system, there's essentially no change to total system entropy. And if entropy is unchanging, haven't we lost our arrow of time? Maybe that 10^-43 second is in some sense an infinitely long asymptotic approach to a time zero singularity that never actually happened since both the singularity and time were imaginary quantities at that point. They just hung around for eternity in GR maths. Just one speculation among many.

It was a throwaway comment, Michel. But since you raise the point, not so many of the photons would be coming directly at me would they? Once their trajectories are sufficiently oblique, the blue shift issue goes away, doesn't it?

Understood. But some interpretations do my head in a little less than others. I have no objective justification for preferring green over orange. Just do

If you can't blow it out of the water on sight, Strange, then I'm considerably more comfortable with it. Maybe even comfortable enough to consider applying Occam's Razor to the Multiverse, which has always seemed a bit too profligate for my taste. Many thanks for your time and consideration.

Thanks, but it isn't the acoustics I'm asking about here.

Did they measure free chlorine levels? My own experience of water disinfection is mainly with hypochlorite and chlorine dioxide systems, and they were certainly active in the more elevated temperature associated with process water systems in the paper industry (where I served my apprenticeship). AFAIK UK water companies tend to run around 1 mg/l active chlorine. Separating the chlorination effect from the temperature sensitivity of the organism would probably require a decent research grant. My impression is that these are in short supply for tropical diseases lacking obvious military potential.

What temperature of tap water were the Leptospires cultivated in? The 10 degrees C typical of British mains water supply? BS 6700 Legionella rules prescribe a maximum 20 degrees for any cold potable water system, and householders will tend to object anyway if its much warmer than 10 degrees.

By using these adjectives (constantly!), your question assumes its own answer. Would experiencing a hellish and distressing live performance of Mendelssohn's violin concerto be worse than dreaming about one? Such a framing of the question is an attempt to deny the existence of anything but the worst possible outcome. You cannot engage meaningfully in a reasonable discussion with such a closed mindset.

After 40 years of not having the time, I've finally got around to writing up a thermodynamic analysis of how a trumpet works. Bear with me. One thing a trumpet doesn't do is support even harmonics in its waveform. Any such acoustic wave emerging from the performer is negated by an equal and opposite reverse wave sent back from the room. Seemingly entering the bell 5 milliseconds before the note commenced. The maths tells me that this seems to be the case, but reconciling it takes a little thought. And that thought drifted to the EPR paradox. I'll not attempt to summarise it, I'll just link to the activities of Alice and Bob at https://en.wikipedia.org/wiki/EPR_paradox. I've thought about this before and often wondered why Alice's +x spin particle doesn't simply (!) send a T-symmetric advanced wave back to it's point of origin, eliminating all potential histories of a +x spin particle reaching Bob by destructive interference. We know that Alice can't manipulate her observation to transmit information so there is no faster than light communication involved, just a reconciliation of the physics. I've never taken this further because most of QM maths is beyond my meagre capabilities. But then I discovered https://en.wikipedia.org/wiki/Wheeler%E2%80%93Feynman_absorber_theory which seems to postulate just this idea for the Maxwell Equations. Which lead to https://en.wikipedia.org/wiki/Transactional_interpretation. On the face of it, it seems such a neat way to resolve so many issues, there has to be a flaw somewhere. Doesn't there?

I don't think many reading this would be in a position to 'help test' anything here unless they happened to be working within an organisation developing this technology. And they're hardly likely to divulge their proprietary secrets to a stranger in an open forum are they? Pressurised hydrogen is not a material you can safely handle in any garden shed development programme. As mentioned above, keeping it contained is particularly difficult and way beyond the capabilities of the inexperienced layman. If you really want to get into the field, probably the only practical way is to get a good mechanical engineering degree with a hefty loading of thermo and materials science, and apply to one of the automotive companies working in this area. Having said that, there's no harm in a bit of theoretical research via google (much more effective than asking questions on an open internet forum). Start with https://en.wikipedia.org/wiki/Hydrogen_internal_combustion_engine_vehicle and follow the linked references where ever they lead. Btw We generally don't produce hydrogen in bulk by electrolysis. Steam reforming of natural gas is far more cost effective. But you don't want to try that in a garden shed either.

Perhaps if we think backwards. There are a few universal clocks. The exact here and now will vary, but every observer in the universe will be able to pinpoint a moment when the average CMB temperature in their observable universe matched the triple point temperature of helium for example. Going back in time there will be a series of similar thermodynamic milestones which one would presume ultimately to converge on a common state at a time of universal causal linkage when all clocks could be synchronised. Even if that synchronisation was at an asymptotic approach to zero. Or maybe I'm just talking cojones. Wouldn't be the first time.

It's conceivable that astronomers all over at least the local area of our observable universe are watching the highly unstable star Eta Carinae and waiting for it to go bang. Which should give us all a really nice fireworks display. (I have a small hope but possibly in vain). Not one of them, whatever their distance and relative speed to Eta Carinae or anything else; whether they're observing from an orbit within an event horizon; whether they have a long garishly coloured scarf and call themselves Doctor; even if they're boldly going where none have gone before; will see this event run backwards. The Second Law will not be denied, and all observers shall see order beget chaos. It all springs from there.

If the object is submerged in brine, you maybe shouldn't be expecting to see the typically scaly orange rust. If it's sufficiently anaerobic, the Schikorr reaction may well be in play which may give a degree of passive protection via a magnetite surface layer. The 'thin black film' you mention is also suggestive of this.

You're going to hate this. I'm sure you meant to type 'homophone' there/their/they're!

Just to show that your advice has yielded concrete results, here's one of the pretty pictures that comes out of it. Which indicates that a simple approximate model deviates from the fully analytic solution (that's taken me maybe a month to derive) by about 1 degree of phase shift here and there. May as well not have bothered! Thanks again anyway! Seth