geordief

Is the question here whether a particular system can be considered as having a measurable property in that it contains(spacetime) intervals? (trying to keep up with my own assertions) Well ,those intervals could be evenly spaces (flat space?) or unevenly spaced in regions of the system that contain varying energy densities . Could that system have a measurable property based on the intervals between its events? As an aside is the spacetime interval also called or closely related to the metric?(have heard "metric" used very often with understanding it too well)

Are you saying that events have to be within the "causal window" to be related?** Might my post stand up if i limited the events to that subset? Or would you stilll answer that there was no intrinsic system of events ,but just that we put that construction on them? **perhaps it was a more general observation?

A property of the system? Is the system as (physically) real as the objects (events?) that populate it?

I thought the particular spacetime interval was definitely real whether or not we agree upon it in different accelerated frames or not (I was under the impression that they did agree but perhaps I was mistaken and the agreement only applies between unaccelerated frames I also thought it was possible for an observer X in a frame accelerated wrt observer Y to calculate the spacetime interval as observed by Y if the observations were indeed different. (Perhaps I am mistaken in this also :-( In any event I have been under the (mistaken?) impression these last 10/15 years that the spacetime interval was the one physical quantity that all observers could agree upon.

I think I mean real as in that they exist (not necessarily physically -but possibly physically and at least as a property of something which is physical) Not quite sure what you are asking in your second paragraph but does it boil down to asking ehether what I see as real is equally as real as what you see as real even if we disagree as to what we are seeing? If that is the nub of what are asking then that is a difficult question and perhaps I might say that we would have to look for the intersection of my perception of events and your perception of events and that this intersection would include everything that we can agree on (like perhaps the spacetime interval and perhaps other quantities I am unfamiliar with) That sounds a very limited area of shared realities but perhaps it is a building block and once we know it is there we are free to gaily constuct cities in the sky of assumed realities that are probably true and most usefully so. The alternative of imagining that things aren't real because we can't prove it for definite is too miserable an idea to hold in the head (I am not sure if anyone does-I don't except in a fleeting ,whimsical way from time to time)

Is space time not just the set of intervals between events? If the events are real aren't the intervals a property of those events? Aren't properties as real as the objects themselves?(the events) If the events follow quantum rules then would quantum spacetime reflect the behaviour of the quantum objects?

Was I wrong (or is it irrelevant) to see flat spacetime as a kind of curved spacetime? "Flat spacetime" just being an idealized limit of spacetime which is always curved to one degree or another?

Can't one measure a spacetime interval with two beams of light directed from an observer at two different events? (eg moon rise and moon set)

You would be John Lennon?

...dixit dipstick

Life was simpler back then.They never had to divide by zero.

I don't know.

Still working through your (and @MigL 's ) earlier replies but I just wonder if the "universe creating space as it expands" concept covers this?

I wonder do any physicists use the term "vacuum" in that "old" sense nowadays? It is used ,but as you say I would like to know what it is meant to mean specifically. (Or whether it is perhaps just a portemanteau for something we don't /can't understand whereas we do have models for things pertaining to the old idea) When you suck as much the energy out of a system as possible do you approach one universal configuration or do more than one such configurations open up?

Is that not just a definition for a "vacuum"? (a vacuum as otherwise defined** may not exist by its own definition) **"absence of anything"

Yes,that result is set in stone.The rest of the world will have to put down the tinted spectacles when it comes to dealing with America,whatever comes next. In addition the whole world is changing at an accelerating pace and America will no more keep abreast than any of us. I remember a conversation back in the 60's where I was talking to a friend who happened to be one of the visible disruptors in the local Gilberd school( I was friendly with the son of the headmaster who was really cheesed off about it/him-thought he was a middle class poser) Anyway his words to me were that he would like to destroy the system and "see where the cards fall" (I assumed he was an anarchist) I don't suppose he espouses that view now but these are the times he was wishing for back then.

I don't see how gerrymandering alone would be enough.Maybe,if they play thst game the Dems will come out on top as well - as the natural swing that seems to be there against the Republicans this time around.. A pity there isn't an "open your eyes" pill that would crack open the Maga base but I fear that is just who they are and they are seeing what they want to see. Still ,they are nothing like a majority.

Iowa Democrats win massive upset...Iowa Democrats win massive upset to break GOP supermajorityCatelin Drey's victory may portend more good news for Democrats next yearAn 11 point Republican advantage turned to a 10 point Democrat win by Catelin Drey.. It would be gutwrenching if similar results to this had not occurred but this is a modicum of good news. Whether it will translate to the midterms if indeed the midterms are allowed to reflect voters' wishes in the ballots is another question. I have the suspicion that the Republican strategy is to provoke a national (notional?) emergency so that the midterms can be cancelled or falsified and I don't see how that can be prevented without an "American Spring" or the death of an ogre.(would love to be proved wrong,not in the last eventuality of course )

Hope it is not some kind of a hack.Happened this time and went through very quickly (a second or two)with a refresh(didn't get the "human verification" screen as well unlike previously.

No ,no changes but I could try using the chrome browser instead of what I use now. As usual this is intermittent and so it may not be apparent immediately.(eg no problem getting in this time)

Is this happening to anyone else? I frequently have to wait about a minute to get to this site(to check that I am human) But just recently there is an additional barrier and it is this "invisionsetup" that has seemingly "blocked me" I immediately refresh the page and the page then changes to the "veryifying that you are human" page which opens up to scienceforums dot net after a short time

One step forward ,no step backward :-(

I have an old tin of fibreglass resin that has formed a very thick skin(because I suppose the tin was not air tight) so that very little was left that was liquid and so useable. I have tried an expedient of first air tightening the tin and then adding an amount of acetone that I happened to have. Can I hope that ,in time the resin (which has not been in contact with the hardener but hardened on its own) will combine the the acetone and become useable again? I don't mind waiting up to a year as I can purchase a new tin of resin to use for now...

Would be a lot worse if they were boreless A world of pointless pain.