geordief

I answered that in reply to Bufofrog in post #3 https://www.scienceforums.net/topic/119646-who-came-up-with-the-idea-of-relative-time/?do=findComment&comment=1111125 Another reason,I suppose could be that I hadn't been paying attention if I thought it was just him Around that earlier Galilean time you mean? Or or you agreeing with Bufofrog that for Lorentz time was still absolute even though he introduced the idea of "local time"?(I know he was still assuming the existence of an aether)

Thanks. Yes that seems very much to to be what I was looking for. "He discovered that the transition from one to another reference frame could be simplified by using a new time variable that he called local time and which depended on universal time and the location under consideration He discovered that the transition from one to another reference frame could be simplified by using a new time variable that he called local time and which depended on universal time and the location under consideration" and " In 1900 and 1904, Henri Poincaré called local time Lorentz's "most ingenious idea" https://en.wikipedia.org/wiki/Hendrik_Lorentz Seems like Poincare gave Lorentz all the historical credit. I am guessing it may have been Gallileo

Well it would mean there might have been a history of false assumptions ,followed by tentative mathematical attempts ending finally with a mathematical model that worked. More interesting in that sense than a eureka moment .Even a record of Einstein's thought processes leading up to that point might be fascinating. It is not Lorentz who was the man ,was it who unified Space and Time in the sense I am asking about.? Did he give the two relatively moving observers their own clocks effectively? How did Einstein's formulation surpass his?

Is there a record of who it was who introduced the idea of using separate measurements of time as applied in different frames of reference? I mean ,was this idea worked with before the idea that space and time could be connected mathematically into one concept? (I was trying to work this out from scratch and I was trying to imagine using a non moving clock such as a caesium clock as a time keeper that would apply to both reference frames until I realized that this clock would also be viewed according to reference frames.) Who might have been the first person to have realized that you might have to consider "time" separately for each frame of reference? I am hoping it wasn't just Einstein and that others before him had worked with the idea.(which has obviously been shown experimentally to be correct)

Can the same statement be made about a magnetic field (and any other field)? More generally ,can we distinguish between any object and the measurement (=perception?) of it? ** (if we can't ,does Janus' distinction redundant except to perhaps say that we can only perceive one object at a time and only extrapolate subjectively to assume that the "object" has extent in space and time -and also perhaps to guard against some people's wish to re-etablish an ether?) **so that we cannot rigorously avoid conflating the external which we perceive and the internal mechanism with which we seem to interpret.

It seems like it may be a nasty fly in the ointment for GR. I know little about the subject and this is probably a stupid question...Could it be regions of negative spacetime curvature? I have heard it described as perhaps something akin to an anti gravity so would that imply negative spacetime curvature? Apologies for the level of ignorance edit: on reflection isn't Dark Energy everywhere and not confined to regions (unlike Dark Matter)? If so ,it couldn't be negative spacetime curvature,could it?

Yes that is what I was thinking of. A nice simple answer that puts my question to bed.

What does it mean that a source of energy will curve spacetime ? How is the energy measured? Is it relative to a particular frame of reference? Does that mean that 2 different frames of reference will measure the spacetime curvature of an identical region differently? Does "region" have to be understood in spacetime terms?

I am a little unclear about this. If energy is (as I have learned) a property of things rather than a thing in its own right does it follow from your statement that matter also is a property rather than a thing in its own right? I am being too literalist (and OT)?

Is the state of change what qualifies any system as existing? If somehow our own universe were to cease changing might we say it had ceased to exist?

What if the sphere was larger or more massive than the Earth? Would we get fusion then? And can we also increase the density of the objects meeting at the centre (protons?) I am not suggesting anything practical. Are there any testable theories as to what happens inside a BH? Is it possible/impossible that there is a region close to the "centre" and another region closer to the "perimeter"? Is this just an area where nothing is testable or worth speculating about?

What if we increased the mass? "Clearly" we would get nuclear fusion but are there any denser masses that might cause anything different. (are there any denser forms of matter than the elements we know of?) Did the lead accelerate all the way to the centre? Did the acceleration lessen as it approached the centre?

Suppose we convert the Earth (or a similar sphere) into a series of tunnels connecting the surface with the centre (billions of straight tunnels) and build a cavity in the central region to accommodate billions of infalling identical samples of ,say lead ... What would happen at the centre as all these sample met and filled the cavity at the same time? (having been released all at the same time) Can this be modelled as a scenario (a computer or theoretical simulation)? Would the lead rebound to the surface repeatedly until it eventually settled in the cavity? Would a black hole form? Would any mass be lost out of a "plug" in the centre (of the Earth) in a wormhole fashion?

Is it possible (ie not too complicated for me) to ask where the covector space ** fits into the relationship of those 3 vectors? (if only to perhaps light my path a little into this territory I am only now learning a bit about) ** I presume it must be there somewhere...

I have it on authority **that tensors enable one to model the electromagnetic interaction between a " moving "charge and an electric conductor in such a way as to dispense with frames of reference . I wonder if anyone might have anything to say on the subject and whether it can be shown in more detail how this is the case. **https://www.markushanke.net/tensors-for-laypeople/

Would there be any consequences if there was rather than there was not?

No internal structure? Yes I looked at one of his videos. My head hurt succulently!!

Seeing is believing.So what is going on at the deepest part of that beast? Something forceful enough to hold in the contents.. Just nowhere to go ,simple as that -the force of logic? Just like pumping up an inner tube? Gravity is resisted there because there is nothing there for gravity to push against..Is that just Newtonian? Or is the force of gravity zero anyway at the bottom?

The void itself is expanding...? Not the distance between objects in the void?

Is a sphere a mathematical rather than a physical object? (an idealization) The universe (which is what I was thinking of by "space") cannot be spherical even allowing for it being unobservable in places. So can this universe be both finite and expanding? Would the expansion itself have to be bounded for this to be possible?

Can space be both finite and continuously expanding?

https://www.symmetrymagazine.org/article/lhcb-discovers-matter-antimatter-asymmetry-in-charm-quarks "Matter and antimatter cannot coexist in the same physical space because if they come into contact, they annihilate each other. This equal-but-opposite nature of matter and antimatter poses a conundrum for cosmologists, who theorize that the same amount of matter and antimatter should have exploded into existence during the birth of our universe. But if that’s true, all of that matter and antimatter should have annihilated one another, leaving nothing but energy behind." That quote from an article detailing recent findings at the Large Hadron Collider (probably a more interesting story in itself than my query) I thought I had learned that "pure energy" is a misconception but that quote seems to me to be describing it in those terms. The matter /antimatter collision seems to leave behind nothing but energy. Can anyone clear up my misunderstanding?(I thought there was a respectableschool of thought that posited that there was a zero total of energy in the universe even though perhaps this could never be shown experimentally)

Thanks, that will take me some time to learn.

Suppose there are a number of electrons at various locations (at the same energetic level) in the atom,is the probability wave used to determine these likely locations? Also do these electrons interact with each other?

I think I have heard that if there is an energetic input into an atom then a constituent electron (or electrons?) will move to a higher energetic level in the atom. Am I to see this as the same electron (s?) moving from one level to another or should I imagine the first electron disappearing from the first level and the second electron materializing at the different level? Would it be the global state that determines the local state? Also is it correct to see the locations of the electrons in their levels as being determined by probability waves and not waves in space (or should that be spacetime?)