joigus

OK, but you're drifting away from entropy. I mean, electrons, photons or pi mesons can 'experience' curvature (and there I do accept your term,) but not entropy, as entropy is a property of your level of description. It's to do with lost information, and particles don't lose any information AFAIK. Or the concept of them 'experiencing loss of information' doesn't seem a reasonable physical concept. What entropy growth (or information loss) has to do with is a quite abstract but useful concept that is called 'volume of phase space.' It is a measure of the amount of information that a physical system contains just because of the fact of being in a certain dynamical state. This 'volume of phase space' is neither lost nor gained; it's constant. Just constant. Entropy is the part that is hidden to my description. We could say, \[S=\textrm{constant}\] This is sometimes called 'microscopic entropy' and its conservation is the most fundamental physical principle there is. Now, it just so happens that many things go on without us knowing about it. Only because there is a fiduciary value of a quantity that stays constant and I can associate with the information content of a system, can I speak about loss of information. Otherwise it wouldn't make any sense. I hope that helps to clarify the situation as to the entropy. It's a really confusing concept, and the great mathematician John V Neumann once said that physicists don't know what entropy really is. No longer the situation, I think.

How do you define 'absolute'? For any object moving, you set clocks and systems of laser beams going back and forth to measure positions and time intervals (the latter calculated taking into account how much the signals delay in reaching the observer, it's not 'subjective' time we're talking about; it's not 'when I see the object.') Now, let's call them dt, dx, dy, dz. The so-called proper time of the moving object, in Special Relativity, and with the proper generalization, in General Relativity too, is, \[d\tau^{2}=dt^{2}-dx^{2}-dy^{2}-dz^{2}\] For what observer? For all inertial observers! Now, that's what I would call invariant (I'd never say 'absolute'.) And in order to do that, you need a system of signals, as they're trying to tell you. You need a way to bring it all together, so to speak. For a photon, the proper time is always zero, so photons have no internal clocks. While, seen from the 'outside' in empty space, they always go c.

Sorry, I didn't see the geodesic equation, I didn't see Einstein's equations derived, I didn't see the equivalence principle, I didn't see the Newtonian limit, I didn't see gravitational horizons, FRW or DeSitter universes or any other cosmologies, I didn't see vacuum energy, I didn't see dark matter, or red-shift, I didn't see a thing that even remotely reminded me of gravity, except in the title and Eddington's paper. I suggest you change your mindframe: Try to prove yourself wrong. If you always try to prove yourself right, you're always going to find a way to be right.

I don't know exactly what you mean with 'experience.' Systems of both massive or massless particles contain entropy, a black hole contains entropy of a very different kind, and even for one quantum particle entropy can be defined in terms of its wave function. Entropy, at the most fundamental level, is defined when the distinctions among different dynamical states are lost. Entropy is the opposite of information. The total entropy of the visible universe in cosmology approximately equals the number of photons, about 10^90. A gas of photons contains entropy. So I suppose the answer to both questions is yes. I've just answered the one that Strange passed on, but he was spot on when he said it's about 'systems.'

I was about to tell you about your mistake with the ticking clocks, to do with absorption and re-emission, and elaborating on your messing up red-shift with slowing down. But it would be wasted on you, as there's no one reading at the other end. I close with a quasi self quotation: Gravitational fields do not slow down photons, they just-red shift them and make them bend their trajectories. Read some relativity books. And a literal self-quotation:

I meant, -Today I've learnt about: geons Indebted to MigL

Gravitational fields do not slow down photons, they just-red shift them and make them bend their trajectories. Think again. In no way does that resemble an electron. A bundle of EM field does not have charge, nor does it invert the sign of its probability amplitude under 2pi rotations, which is required. And I've missed the part where you provide a causal mechanism for gravity.

-Today I've learnt about: Einzel lenses and viral load in aerosols. Indebted to: Swansont -Today I've learnt about: colour-entangled W states Indebted to: Studiot -Today I've learnt more details about: quaternary-structure protein dymers and palindromic character of RNA sequences Indebted to: Dagl1 and CharonY -Today I've learnt about: Intricacies related to atmospheric CO_2 absorption by weathering at the Himalayas Indebted to: Area54 and Studiot -Today I've learnt about: phenomenological/heuristic aspects of cosmology in general Indebted to: Mordred -Today I've learnt about: geons Indebted to Strange There's quite a bunch of 'todays' there. And I'm still learning. And counting...

Easy. If what the survey says is actually true --see below: Analogy --not to be taken literally: Go to a prison and ask all convicts for murder crimes whether they're guilty or not. You end up with a list of: 10 % say they did; 65 % say didn't and 25 % don't remember. Conclusion: Only 10 % of convicts for murder crimes actually did commit a crime. Explanation: In the words of Daniel Dennett; American Philosopher and scientist, outstanding at exposing many religious (and other) logical fallacies IMO, "they believe in believing in God." I.e.: They live in a social environment in which it would be far more costly for them to declare themselves atheists than to keep on pretending. Dennett, e.g., takes no prisoners when it comes to theologians. They all fall --willingly or not-- in the use/mention fallacy: "A history of God," "God in our society," etc. Religion is absolutely rife with fallacies, half-truths, and conveniently spun arguments and data. Besides, as iNow says, . Excellent point.

It never crossed my mind. Well, it did, but it was a virtual process.

Forgot to say hello. I'm Joss, I teach Physics, Maths, Chemistry and English @ some academy in Spain. They sometimes make me teach Bio and Spanish, because they somehow assume I must know everything. I'm a theoretical physicist. My alter ego is Sisyphus. PD: I love Yogi Berra quotes

Feynman Lectures on Physics, volume 1, chapter 1, Section 1-3. Atomic Motion. Go to your local library and start reading Feynman now. Then start mimicking Feynman in whatever way you can without giving up your principles, and maybe buy a pair of bongos. Just joking. But the key word in all of this is: Feynman.

I see no significant mistake in the enunciation of the principle. I wouldn't include time to it though, nor do I know of any formulation that does. Another hopefully useful observation is that isotropy everywhere implies homogeneity, which is kind of more economic to me, but not really a big deal. As to current limits to its application/validity/solidity, I hope you find interesting my comments below: The whole issue of the universe being homogeneous and isotropic at 'large' scales is, in my opinion, a very suspect hypothesis. It looks kind of reasonable, though, and allows you to gain access to the big picture of what goes on. But 1) from the theoretical perspective we do know that quantum field theory (QFT), when combined with the general theory of relativity (GTR) in inflationary models, predicts a universe that is more like a fractal, meaning a scale-independent series of embedded structures that may look clustering depending on what scale you look at it. And 2) from the observational point of view, the universe does seem to display huge voids in its structure, very strongly resembling that fractal that QFT+GTR predicts. It's more like the caustics in a swimming pool in 3D (this is a numerical simulation): About isotropy, a very recent piece of news from the experimental front is this: https://phys.org/news/2020-04-laws-nature-downright-weird-constant.html?fbclid=IwAR3_NdXDNfcNU05E8khtN1pnshucr-gr7KoJO5OTh6OAuDDX19Z5yUBPD_c The headline reads, "New findings suggest laws of nature 'downright weird,' not as constant as previously thought". UNSW --Sidney-- professor John Webb: "We found a hint that that number of the fine structure constant was different in certain regions of the universe. Not just as a function of time, but actually also in direction in the universe, which is really quite odd if it's correct... but that's what we found." If that's true, not only the universe wouldn't be homogeneous; it wouldn't be isotropic either, and at the deepest level, because what's different is the electromagnetic coupling constant itself. Now this would really be amazing and we should take it with a grain of salt. The statement that the universe is homogeneous in time is tantamount to saying that it looked pretty much the same in the past than now or in the future. It was obviously not the same in the past, as it looked like a singularity, then opaque to radiation and neutrinos (plasma), then radiation dominated, then matter dominated, and today it's considered to be dark-energy dominated. So it doesn't really look like it's going to be the same in the future, as it will exponentially expand.

This may be a silly question, but just in case. Can someone tell me if there is the possibility of using RNA-splicing endonucleases like the ones referred to at, https://www.ncbi.nlm.nih.gov/pubmed/18217203 to target specific sections of a known virus in order to deactivate it inside the cell in a similar way that restriction enzymes in bacteria function against their bacteriophages? Maybe by designing or selecting them to look for very specific viral sequences but long enough so that they have a very low repeat probability? Or maybe by methylating the sensitive areas in the self RNA? I don't even remember if RNA is susceptible to methylation, which DNA is. Or maybe both? Is that even possible? Or maybe too out there. I'm not even sure this is the proper place to pose this question. I'm sorry if that's the case. Thanks a lot in advance.