Carrock

Sorry, not very rigorous like many in this thread but this one's easy to respond to. e.g. The concept of unlimited size means (by analogy with an unlimited but finite set of integers, for example) that however far you walk, you can always take one more step. i.o.w. the concept of a finite or countably infinite universe expanding for unlimited (but not infinite) time is perfectly OK. A universe which has expanded exponentially for infinite time is inconsistent with any current theory as its volume would be uncountably infinite. The 'I can't get to the infinite future from here' argument doesn't work very well since photons, which have infinite range, can get there from here. Models which predict unending expansion are therefor problematic.

Reference? Did you actually read my post? I, and perhaps you, stated the probability of the universe being as it is to be unity; but you say I am wrong because I believe the universe is almost certainly different from what it is(!) Where is an intelligent designer required in this (observationally refuted) universe or any of its more sophisticated successors? BTW I should clarify that Boltmann's assistant's universe and AFIK all similar universes are not fine tuned; they do not require an intelligent designer. I used the human concept of 'fine tuning' which was misleading; the universe is no more 'fine tuned' than a waterfall is 'fine tuned' to be beautiful. Claiming that the universe we exist in (not multiverse in many theories) necessitates the existence of an intelligent designer is just a creationist fantasy. No mention by you of eternal inflation Bayesian probability etc.

I'm guessing you're responding mainly to me. No. I don't know anyone who claims there is any possibility the universe is different from what it is. But given my limited knowledge, the odds against even the earth being the way I expect it to be next week are huge.... A sample of one where one person has won the lottery once (or twice) tells you nothing about fine tuning. IIRC there have been a few people who've won a major lottery in successive weeks. Why are these people special when single winners are not? Actually the chance of a single or double winner winning the lottery again, from just one ticket, is exactly the same as for someone who's never won. (In the real world, the chance of an innocent three times winner being convicted of fraud is significant.) In other words, tossing a fair coin and getting five heads in a row does not change the odds (50%) of getting a head on the next toss. Bayesian probability is calculated on current knowledge. i.e. here the probability of having five heads in a row is 100%; a sixth head is 50% not 1.5625%. As there is not perfect knowledge of the universe, it is possible and useful to predict aspects which have not yet been observed. For example: The original classical fine tuned universe theory (by Boltmann's assistant) postulated that a random low entropy fluctuation in a heat dead universe created the solar system and everything needed for human observers to evolve. It was noted, in a Bayesian way, that the probability of low entropy in so far unobserved parts of the universe must be less than one in a googolplex i.e. the universe must be minimally life friendly.. The discovery of low entropy in previously unobserved parts of the universe showed that fine tuning theories can be falsifiable. Various theories, such as eternal inflation, postulate the creation of an unlimited number of universes with different laws. It seems to me that the existence of observers in such theories is only really possible in intelligent life tolerant universes with tight parameters, much as human beings pretty much require a life tolerant part of earth, even though it's supposedly not impossible for them to exist briefly as Boltzmann brains. A key aspect of many/most anthropic theories is the prediction that the (unobserved) universe will be found to be minimally tolerant of life with human equivalent abstraction since even finer tuning is required for extra 'unnecessary' life friendliness. Note this may be one observable universe of a possible multiverse; already known facts are of limited or no value (Beyes) as in the disproof of Boltmann's assistant's theory. It may be be most other intelligent life communicates with yobba rays or whatever, but 'fine tuning' suggests intelligent life is so rare we may never find any despite improving search techniques. Even if this is the one and only universe, it is still worth producing theories which predict things which may exist but have not yet been observed.

If that was true, the chance of a creator existing without a creator to create it is, essentially, impossible. Plus another creator to create the creator of the creator..... BTW what is an essentially impossible chance?

"Shockingly inefficient design?" Only if you believe in a rather incompetent intelligent designer. I'll assume a weak anthropic principle i.e. that our universe is constrained by the necessity of having at least one instance of intelligent life capable of wondering if its universe is constrained by an anthropic principle. There's no obvious size or practical time constraint imposed by physics, and if the only 'necessity' is having at least one instance of intelligent life, then the laws are only constrained to allow a minimally intelligent-life-tolerant universe. Earth may have been extraordinarily lucky to have remained intelligent life tolerant for so long; the dinosaurs were around for 100 million years without evolving human equivalent abstraction and technology so that may also be extremely rare. I doubt any anthropic principle will ever become a truly falsifiable theory, but the continuing failure of SETI to find evidence of extraterrestrial life despite improving technology does fit with the idea, dating back to Boltzmann, that the universe is minimally intelligent life tolerant.

I glanced at lyincomey.com and noticed they were referencing FAKE NEWS sites like CNN etc. Surprisingly, neither Trump nor his supporters have realised that Comey must therefor be telling the truth...

If I look at an orange in daylight, or under artificial light with a different spectrum it always looks orange coloured to me because evolution has enabled me to see colours largely independent of the quality of the illuminating source. If I photograph the orange under both these conditions with no colour filtering, the orange in the photos looks to be different colours. Which if any of these colours is 'scientifically' correct?

pt and ps appear to be defined by you as constants. Therefor se is also constant. I presume this isn't what you intend. More clarity required.

Every Windows system I've ever used slows down substantially as 'updates' are added. Unless you're willing to run Windows without protection from recent viruses the only solutions are to buy a newer Windows version or run a free OS such as Linux. (Mint is good for beginners.)

There doesn't seem to be any generally accepted definition of the Copenhagen interpretation. This is as good as any. (From https://en.wikipedia.org/wiki/Heisenberg_cut ) In other words you could have an atom as the observed system and the rest of the universe as the measurement apparatus. Or you could have the solar system as the observed system and the rest of the universe as the measurement apparatus. (Voyager 2 would do as an observer.) This seems to me rubbish but it's the best version of the Copenhagen interpretation I'm aware of. Can anyone clearly describe a better one?

I don't get it. A cushy office job involves putting your jacket on a chair in your office in the morning and collecting it in the evening. Definitely no sitting down.

It is a complete description of rest mass. Momentum etc is not included. As there is no universal equation of everything, every equation is incomplete in that sense. e=mc2 is not a shortcut in finding the equivalent energy of a mass at rest. You could add 0 momentum and 0 unicorns and 0volts/second if you wish.

e=mc2 is dimensionally consistent...

The tables are pretty useless, but a voltage erg(e.s. system) is pretty clearly different from an energy erg. I don't know much about c.g.s., but I'm certain it was dimensionally valid if you use its peculiar conventions. [edit] There seems to be a mixture of three different conventions on p.330 col3.

Why do you claim inductance is a length in CGS. Why do you claim voltage is energy in CGS? Is jumping from 3 metres below ground level to 2 metres below ground level possible only in maths, not in the physical world?

I can't see why not, in principle. A photon (say in the CMB) could continue going through space and missing the hydrogen atoms and stars, which are few and far between. That's the fate of most photons in most cosmological models. It's still possible that yet unknown physics may mean we're in e.g. a cyclic universe where all photons eventually interact in the future so there's no direct evidence that (no second interaction) photons exist. Momentum is transferred from the source to the photon. It doesn't then need to be transferred to something else, does it? I suggested a photon is an instantaneous transient of an interaction between objects separated by a lightlike interval. I'm not convinced that such an instantaneous transient in one object can give rise to a photon which never interacts with another object. I suppose the only way forward is to have a good look at the maths.

I was guilty of anthropomorphising earlier.... I don't think a photon 'experiences' anything. It's just an instantaneous transient of an interaction between objects separated by a lightlike interval. Any valid reference frame infinitely 'stretches' this instantaneous transient into what's called a photon. The photon is just an artefact of any valid frame. I'm just wondering if you can have a photon sourced by one object but with no interaction with a second object. There is no momentum etc transference. I suspect at most only a virtual photon could be created. I can't find any good reference on this (non?) issue.

If all of the physics we know requires a valid frame of reference, is the description of gravitational redshift, Doppler shift etc of photons without valid reference frames not physics? Indeed, without valid reference frames, are photons completely unknown physics? Length contraction is a function of reference frame; a reference frame can be chosen for no or any desired contraction. I only meant that it is a function of frame choice. As with e.g. photon energy, which has no upper or lower limit, the reference frame is chosen for convenience in calculations involving interactions. I'd be interested in any response you have to this rather informal description. (I don't see how a photon could experience duration without having a valid reference frame. The claims I've seen to that effect violate well established physics.)

"You have a destruction/creation (depending on which way time is running) which does not reflect the actual conditions of the problem." "Photons are created by the blackbody." In what way is the creation in the second sentence different from the first? You can't analyze this from the photon's frame of reference, because it is not a valid frame. We have no physics to apply to it. I was anthropomorphising a bit. I think it's pretty generally accepted photons cannot experience duration, which is implied by there being no valid frame. A lack of a property is still physics. I would say a photon is simply a transient which occurs instantaneously as two objects in the same place at the same time exchange energy, momentum, spin etc. Necessary if a photon doesn't experience duration. This transient is infinitely stretched from the viewpoint of a valid frame and can be inferred to be a photon travelling a frame dependent distance with some frame dependent properties such as energy and at frame independent speed c. This photon is no more or less 'real' than the length contraction of a massive object with relativistic velocity w.r.t. some valid frame. The issue is how does this transient occur if there is only one object - in this instance a black body in an otherwise empty universe. Can't delete this. $^%"%&**(##@ forum software.... If it's just an interpretation it should be easy to solve this problem without assuming antiparticles really travel back in time.

Given that photons are their own antiparticles, whether observed photons go from the future to the past or vice versa is an arbitrary choice. (See earlier post.) The fact that future photon destruction/creation is problematic is not IMO adequate justification for saying photons must go from the past to the future. I offered an alternative with no boundary conditions. Photons do not have a conservation of number law associated with them. And it's trivially observed to be true in any number of reactions. True, but rather ignored my point, which from context was that photons cannot be created or destroyed in empty space without violating conservation laws. Photons have infinite range and do not experience any sort of time or duration. If a photon is created and destroyed elsewhere, those two events are entangled. If a photon is created and never destroyed or vice versa the photon is 'aware' of the asymmetry. I suspect this would prevent such a photon existing as anything but a virtual particle. I've DuckDuckGone quite extensively, and can't find any discussion of this issue. In cosmology there are theories which avoid this possible issue in the real universe.

No gravitation and no cosmic redshift leap to mind in an empty universe.

In the context I was using, space with no particles for photons to interact with. Virtual particles are no good here for photon emission/absorption.

OK. The photon is generally considered to be its own antiparticle. It's not currently a popular idea, but AFIK an antiparticle is mathematically equivalent to a particle travelling backwards in time as in e.g. Feynman diagrams. So a photon travelling forwards in time can alternatively be considered to be an antiphoton (i.e. a photon) travelling backwards in time. So in the universe we're discussing, the photon is created in the future and travels back in time until it interacts with the black body. Energy, momentum and spin (i.e. a photon) is created from nothing, violating three conservation laws, and travels back in time until it interacts with the black body. The alternative, that such photons can be (destroyed but not created/created but not destroyed) is also problematic; I'm not aware of any theoretical basis for that. Some cosmological theories dodge this bullet with a 'future singularity' i.e. hand waving; others avoid it by e.g. postulating a temporally finite universe. A full consideration would require its own thread but it would soon get hijacked.

I'm suggesting there would be no photons in an otherwise matterless universe even near the black body at any time as conservation laws forbid it, assuming time-reversal photon symmetry. The only reason I can see for any photon time-reversal asymmetry is that many (unverified) cosmological theories require such asymmetry.

There is the absorber problem for an empty universe (as well as many popular cosmological models), which has been around for a long time. There is a strong case for claiming photons have time-reversal symmetry. As photons have infinite range, this symmetry implies they have to be destroyed (i.e. the time-reverse of created) as well as as created. There is no way to destroy photons in empty space without violating conservation laws. So it may be the only blackbody in infinite and empty space has no way to lose energy and will forever retain its temperature.