andrew s

I don't know not really looked into it. Regards Andrew

Another alternative is the block Universe where all 4d space time exists but we just happen to experience it one moment at a time. Regards Andrew

Of course you are my bright little star. I've miles And miles Of files Pretty files of your forefather's fruit And now to suit our Great computer You're magnetic ink. Regards Andrew

Ok so why do the stars have blue halos? Regards Andrew

Putting aside differences in perceived sharpness I think there is possibly a technical reason for a difference between stars and hydrogen emission nebulae. Stars are wide band and subject to the full force of atmospheric and chromatic aberration . While the nebula is predominantly narrow band in the red and thus less impacted by the atmosphere and chromatic effects. It's noticeable that @ollypenrice original stars have blue halos. I doubt a reconciliation is possible though 😊. Regards Andrew

I'll have to let Olly comment on that. However, what counts to the eye is the detail it can pick out. A bright star will have an obvious impact over many pixels. A chain of dim stars (with the same FWHM as the bright star) might well be visible as a linear feature just a pixel wide. This difference between point and linear resolution was well known to well respected visual observers of the past. It would be easy to assume by looking at the bright star blur seeing the pixel wide feature would be impossible to see. (I am not saying you are doing this.) I feel though this effect may be the root of your different positions. Regards Andrew

I don't think what you say here contradicts what I said. It's a matter of contrast . Obviously, the FWHM gives an estimate of the maximum spacial frequency that can be seen (but it's complex point v edge v gradient etc.) . Your examples seem to confirm what I was saying. I don't think @ollypenrice is disputing the resolution of the RASA. Regards Andrew

@vlaiv and @ollypenrice you are both right. @vlaiv is correct that that abberations are universal and impact both point like and extended sources. However, just as dimmer stars show less pronounced diffraction spikes, extended objects like planets tend not to show them. This is what @ollypenrice observes. Due to differences in contrast they seem for all practical purposes to be absent. A classic example is curved spider vanes compared to straight ones. Both suffer diffraction but the curved blades result in a distributed low contrast result compared to the high contrast focused spikes of the straight ones. Regards Andrew

If you want the one to rule them all go for an 8 or 10 inch f5 Newtonian. Add quality coma corrector, appo reducer plus barlow/power mate and you have it all. 😊 Regards Andrew

If you want the one to rule them all go for an 8 or 10 inch f5 Newtonian. Add quality coma corrector, appo reducer plus barlow/power mate and you have it all. 😊 Regards Andrew

I think this is the key point. The RASA has a higher etendue than the others. It can capture more light than the others for while its capture area is the same it captures it over a wider field. Great if you have limited clear skies. In the end it depends what you want from your system. We are just lucky to have such a wide choice of telescopes and modern CMOS detectors to choose from. Regards Andrew

On reflection, if you add the 10^500 odd multiverse to the 10^***** (I have no idea how many branches) of the Many Worlds of QM no wonder we can find a theory of everything that correlates just two of them. Looking for an atom in a Universe or two. Regards Andrew

Building on @Zermelo post above. Classical and Quantum mechanics are the two simplest examples of what are know as General Probabilistic Theories I.e. theories that describe correlations of detector clicks. Over simplifying the first, classical, probability theory has the sum of the possible outcome amplitudes adding to 1, while the second, QM, has the sum of the squares of the possible outcome amplitudes summing to one. More complex options follow with accompanying new phenomena. Who knows maybe the rip it all down and start again replacements to GR and QM require the next level 😈 Regards Andrew

@vlaiv I am certainly not trying to defend it. If I had to choose I would reject interpretation and side with "shut up and calculate ". After all that's what models are for, however unsatisfied that leaves our need for explanation. Regards Andrew

If your correct I don't understand why serious physicists still consider it a valid interpretation. Personally, I find it unattractive but that's an ascetic perspective. Regards Andrew PS I found this "A popular criticism of the MWI in the past, see Belinfante 1975, which was repeated by Putnam 2005, is based on the naive derivation of the probability of an outcome of a quantum experiment as being proportional to the number of worlds with this outcome. Such a derivation leads to the wrong predictions, but accepting the idea of probability being proportional to the measure of existence of a world resolves this problem. Although this involves adding a postulate, we do not complicate the mathematical part (i) of the theory since we do not change the ontology, namely, the wave function. It is a postulate belonging to part (ii), the connection to our experience, and it is a very natural postulate: differences in the mathematical descriptions of worlds are manifest in our experience, see Saunders 1998." from here which may be of interest .

As far as I understand it all interpretations make the same predictions so there is no scientific way to choose. It is a matter of philosophy not science. Regards Andrew

Is that in one or all of your many worlds? Personally, I would hedge my bets. Regards Andrew

Sadly, I spent years trying to understand how our classical reality emerged from the quantum world. Eventually, I came across environmental dechoherence but even this did not solve the measurement problem. I feel it's more subtle than @vlaiv characterisation but I may be wrong. I am now content with my ignorance in many areas. Regards Andrew

If you want to frighten a quantum physicist ask them about the measurement problem. 🤫😉😊 Regards Andrew

@saac the hot topic area would be quantum computing. Also solid state chip design is hitting the limits set by QM. Regards Andrew

I did until a few weeks ago when I retired from serious observing. Regards Andrew

Absolutely, the classical world is our domain. It is the bumps and bruises of our experience with Newton's insights that forged our world. It is the lack of connection to our experience that make relativity and QM strange and mysterious. Open to our prejudice and fantasies. Regards Andrew

We can't all be perfect 😊 Regards Andrew

A legacy few can aspire to. Regards Andrew

I have spent a life time reading about and trying to understand time. Alas I am none the wiser. I have a bookshelf full of tomes on the topic from psychologist, philosophers and physicist each with there own take on it. It is enigmatic in the extreme, you can only measure it via a clock of some sort, it is not an observable in QM unlike space. However, it is the one continuous parameter that spans GR, SR and QED without modification. I had reached a similar conclusion to you that t = 0 does not exist just as the ends of an open interval on the real line don't include the end points. In GR singularities are outside our space time - you are spot on there. In the end I am left with what Einstein's I said "time is what a clock measures " Regards Andrew