geordief

Suppose we have a trampoline moving through the vacuum of space At any snapshot in time (so not 4d) the trampoline will look to us in it's normal flat shape Now let us say that a region of the trampoline is subject to an acceleration (for simplicity perpendicular to the surface) so that that region is stretched into the shape all trampoline analogists are familiar with except that there is no heavy metal object producing the "well" but rather the shape is produced "internally " by the local acceleration.** So an observer at a remove from the "flying trampoline" will see a flat surface with a protrusion a bit reminiscent of Sigourney Weaver's belly in Alien. If we now put ourselves in the frame of reference of the flat part of the surface and look around at what we can see from that frame then we will see whatever we will see. But if we similarly look around from the region of the protuberance (if the acceleration has been significant) then the same scenes will be visually distorted and light coming from the same place as was seen by the people on the flat ,unaccelerated region of the trampoline will be coming from a different direction and either sped up or slowed down.(am a little unclear here) Does the trampoline viewed this way provide a good model, not of gravity but of the effect of how light is curved when a frame of reference is accelerated wrt a source of light? Does the trampoline analogy work better for acceleration than gravity? ,**it is just a small,local region of the trampoline that is accelerated and not all of the trampoline.

I seem to remember (in the 70s) that certain regions of France were permitted by the government to add sugar to the grape juice which resulted in a higher alcoholic content. I think regions that could not do this felt hard done by and so I think that too low an alcoholic content must have made the product less saleable. I have no idea if the practice continues. I remember that the grapes used for champagne had a low alcoholic content (possibly necessarily so as I think the whole process is quite different to ordinary wine)

Thanks so much @md65536 and @Markus Hanke That was quite some detail and probing I did "sign off " half way through this (my) thread but am glad I was able to (come back and (re)read it all the way through. Hopefully some of it will sink in. And ,yes the OP was all about GR,in my mind anyway

A joke in a dream. I was watching (as per in the dream) a young precocious Shirley Temple lookalike being interviewed as to where her parents (or similar) were living. She answered "in a cabin"(indicating ,I gathered her humble origins/connections) ,followed immediately by "in space" (indicating the opposite -like it was something really fancy and exclusive) That is some kind of a common joke trope I think but it is the first time I have been so "joked" in my dreams (I think the "audience" was "goshed" by her repartee)

Thanks.I think I am probably done with the thread now.Quite a bit of info for my level.

Is that because mass is a relativistic concept? (I understand that the bonds that hold an object together are calculated as "mass";does relative motion btw objects also contribute to a system's mass?

At the exact point in time *then that the two (relatively moving or relatively at rest) objects' effect on the spacetime curvature is calculated (so hopefully stripping out all dynamic effects**)- are the two effects identical? * when the two objects are as close as possible **if it can be done,maybe finding the number value of the tensor resulting from all its components. Well the masses could be very big even though I was imagining them as small in the OP. Are two two curvatures identical or is the one involving approach speed greater ?

OK ,so from the frame of either of the two objects in scenario A the other approaches and in scenario B the other is at rest and close proximity. So scenario B curves spacetime less than scenario A? Is the momentum of an object one of the elements in the curvature tensor?

Is spacetime curvature frame dependent? (In my second scenario both objects are at rest wrt each other,I think)

Suppose we have two massive spherical objects and they are moving wrt each other. They pass each other at one point . Do their respective momentums (in addition to their mass) combine to curve spacetime at that point? Again (a different scenario) ,if the same two massive objects follow the same trajectory as each other do the pair also curve spacetime ,but differently from the earlier scenario? Ps Am I barking up the wrong tree to try and separate curvature effects due to mass from curvature effects due to momentum and are they perhaps two sides of the same coin?

Ectually she takes after her mother's side of the family (more Rt.Hon than right on) and pronounces that fish as "barse". I flounder when trying to cope with that tomfoolery.

I tried telling that quip to my daughter but just got a deadpan expression.

I am wondering about this supposed spat btw Wagner and the Russian army " Wagner boss Yevgeny Prigozhin has complained of a lack of ammunition, saying it could be "ordinary bureaucracy or a betrayal". https://www.bbc.com/news/world-europe-64859780 Smoke and mirrors or are we looking forward to a Russian retreat quite soon?

It is a faith but an overwhelmingly convincing one. Does it make a point to ask whether "reality" describes something set in stone or something continuously changing ,even if imperceptibly.? Off topic I find it more rewarding and satisfying to weed out what is "unreal" than to home in on what may be considered essentially true.(well I don't have the intellect for the latter ,anyway)

Or My Little Ding-a-Ling (Not sure who was the best American dancer btw his Duck Walk and MJ's MoonWalk

You must mean best Irish poet? Shakespeare is so obviously the most highly considered English poet that it would make little sense to put Spike Milligan in his league. Spike certainly was a wonderful man writing a wonderful epitaph for his tombstone but could never have written the Tombstone Blues.

I think the first line may have come from the title of this book (but don't quote me) https://en.m.wikipedia.org/wiki/Darkness_at_Noon I think that Dylan is dead to the new Dylan .

Have there been any studies on children brought up from birth with no connection to their genetic parents? There must be very many cases where a child is born but the parents and /or other family members die . Would such circumstances shed light on whether there is behaviour that is truly innate and what those behaviours might be?

Hadn't considered that.But some of that stuff will be moving in the opposite direction to him.Can he see that? Some stuff will be orbiting the BH;might he see that as it swings around in his direction?

So the premise in the(my)OP was wrong .A misunderstanding no doubt on my part from a long time ago. Moving on,if we have a spacecraft approaching a black hole activities btw it and the event horizon will seem speeded up,won't they? An observer in the spacecraft will see all the objects which had disappeared into the BH ahead of him ,can record them and send back the recorded pictures of all that happened just outside the event horizon from the inception of the BH. It would need a very powerful slingshot to send back the holiday snaps (and it's own deductions if appropriate)

Would it (the time dilation)slow the speed of the conversation down without affecting the pitch? (Maybe it would affect the pitch too) Would there be a particular relative speed where the doppler speeding effect would exactly counterbalance the relativistic time dilation slowing effect?

Well ,not by later recovering a recording of any conversation (that is obvious ,I suppose) But hopefully using whatever method comes closest to how we listen or watch something in our own frame of reference (there is forcibly a delay ) So in my mind ,for the approaching spacecraft I imagined us sending a laser beam against perhaps a window and capturing a recording of the window's vibrations in the light that was reflected back to the emitter. For the plane travelling just below the speed of sound I had a similar (same) method in mind So ,as "directly "as possible (perhaps there are better methods?)

I have been reliably informed that ,if we could listen in directly to an object like a spacecraft that was approaching us at a relativistic speed then any ongoing conversations would be heard slowed down rather than sped up as my intuition have supposed. Since we also have the relativistic doppler effect (ie in addition to time dilation) am I to think of a conversation that would be both high pitched and slowed down? And what about the same situation but purely with sound? If we had a plane approaching us at just below the speed of sound could we reflect a sonic beam against the cabin window and eavesdrop on the pilots conversation? Would it be high pitched and simultaneously slowed down?

"Meme" is a word whose meaning I cannot fix in my mind no matter how often I learn it. It seems simple enough but each time I see it used it doesn't make sense

Not inherent seemingly as it is a translation. (I know sfa about the man's work...I think he lost his mind in the end)