geordief

Certain curved manifolds ? Does that mean different classes of manifolds or just one class of manifold with differing properties? My understanding was that the manifold that modeled spacetime was that with the parameters (correct terminology?) of 3 spatial and one temporal(sign reversed ) components -a hyperbolic manifold. Are there are** ways (manifolds) of modeling spacetime ? ** EDIT: are ="other" ,of course .

Subsequent to the detection of gravitational waves which seemed (to me) extraordinary even if ,apparently it was to have been expected would it be correct to say that the detection of Hawking radiation would be something so difficult that we might even suppose with a huge degree of certainty that it may be that scientists will never,ever actually detect them?

I haven't had time to go into the replies yet but do you stand by that description? I am familiar with the "mass curves spacetime and spacetime tells mass how to move" description but this seems different . Is your word "is" to be taken loosely? " Mass and the curvature of spacetime are intimately related" is what you are saying ? Or "mass" and "curvature of spacetime " describe the same thing"?

Did Newtonian physics predict Black Holes? As I am belatedly understanding it was GR that predicted them but what would Newtonian physics have made of the situation ? Would it have envisaged explosions happening eventually as the mass increased ? How would it have viewed the scenario differently? Were Black Holes something that were theorized and discovered only after Newtonian Physics was "out dated" ? Coming back to GR ,might it be ,as I think I may have heard that we are not talking about a build up of matter but a change in spacetime curvature? Is there any theoretical way such a curvature can be reversed? Is that Hawking radiation? The BH will slowly "empty out" ?

I have given you my first and only "like" in over 20 years on the internet. A cumulative "like" like the way a ref hands out red cards after a long series of fouls. I did ask (and Swansont answered) whether these kinds of questions could serve a purpose. I think they can as they provide a framework for the more bread and butter (or croissants and cream) questions but you are right in that any confusion is as bad as sand in the you know where . I know I said wouldn't contribute ,but it was my OP after all and I am accepting the ticking off

I agree with disarray's last points. Can we start a campaign for the proscription of the use of the term "reality" for the under 18's? If "reality" could be shown to actually exist it might be like a mini black hole and swallow us up.. Incompleteness is far more satisfying (or was that dissatisfying? ..whatever) I also liked his analogy in post#20 of the deity sitting at the pixelated TV screen. Did he then ,mythologically disperse the pixels with a sneeze ,blow away the cobwebs and proclaim ,"hey presto welcome Creation!" ,knocking over the pile of turtles as he did so ?

The tools are just extensions of our biological sensory apparatus. Without this biological sensory apparatus to interpret* the measurements the tools are just so many assemblies of objects.....The biological apparatus is like the gate keeper.,or perhaps the slowest marcher at whose pace the army marches. * and to build the tools

But it does feed into our perception of what is ..."what" and so ,although rudimentary in comparison to our exquisite machines does occupy an extraordinarily "strategic" position .

Is it important for a theoretical scientist to have a grasp of the two concepts ,the "model" and the "modelled" ? Can a confusion of the two cloud the thought process or is this not an important consideration aside from being interesting in its own right? No one has mentioned that the sensory equipment of the body can be considered as a biological measuring machine? Is that a consideration?

So my question makes sense? Will it help me if I use it as a (theoretical ,obviously) example for clarifying my understanding ? To my mind it seems like it might be a way of mentally melding the model with the modeled The paper would bend but would the lines on it bend with respect to the paper? Could the parallel lines be drawn (on the paper) as never meeting but the curvature imposed on the paper itself meant that they did actually meet with respect to the wider environment?

Suppose an observer on the Earth had access to physical graph paper that was large enough to itself be affected by the curvature of spacetime , would the observer / gaph maker need to make that graph paper with curved lines ? Or would the curvature of spacetime do that for him and so he he "attempt" to draw them straight ? Perhaps my actual question makes no sense and I will accept that judgement....

Is that a model of a model ?

Thanks . That is a question that has bugged me for a long time . I will take your explanation on board. (it would help if I had more of a handle on the actual maths ,of course -a shame that it has been too hard for me to crack so far )

I thought I had organized my (basic) appreciation of GR in that the curvature of spacetime refers to the curvature of the GR model(I still don't understand the nuts and bolts of that but it seems to be bound up with tensors , I think) As for the reality and whether it is actually curved , I thought the idea was that we don't actually know . (the model includes a curvature and successfully predicts the dynamics of space time within its area of applicability) But my understanding is being shaken by the language employed by Prof. Brian Cox who is a popular science presenter on the BBC and as far as I can make out is actually a well respected scientist in this area. He seemed to insist on the notion that space (sometimes he referred to it as spacetime) is actually curved by mass,etc. Does this matter.?Is it in large part semantics? Is Prof Brian Cox trying to shock and awe the audience? Is he actually right? If the model is curved does it follow that the reality is also curved? If the universe is actually a hologram is the question academic ? (reality is a model ?)

If you But you do not have the luxury of "taking a breather" . Life moves on.

Because there is no "destination"? It is like a mirage in the desert?

If you are looking purposely for something you will have an idea what it looks like and ,at some point you may say to yourself that you have found it. But you may be mistaken and have found something else. If something comes to you of its own accord there will be no mistake ,no need to compare anything with any prior expectation. It will just be a matter of appraising what you seem to have got and maybe giving it a name.

The "else" is the same thing but achieved in different ways. If it comes of its own accord then that is "else " as compared with what you hope to get by your own work . And vice versa. Perhaps the aim can be achieved by own path alone , perhaps by both (I don't know) but the path that is not taken has a "destination " that is "else" (=other) as compared to that of the other path. It would be easier to make up our minds as to which method is more likely to work (and forget the other one perhaps) Speaking for myself ,I have always had a strong purpose and so lack the insight as to how it might be necessary to find one (except in a theoretical way as I know people who have told me this) On the other hand I think it is fairly common when someone learns they have a terminal illness to be overcome by a sense of meaningless and so that might happen to me then if I do not get lucky with a quick demise (where is the icon for "chin up"?)

You may not recognize it if you are looking for something "else". There is the saying(I think) "Life is what happens to you when you are not looking"

Money can also be a plaything and people who gamble money can come a bad cropper

Well,I think it does. If you are looking for something that finds you then you will never find it (except by accident) and in fact you could be driving it away? And ,if you are waiting for something to fall into the palm of your hands that actually needs to be reeled in then again it will be no cigar. I hope you will tell me if that is just verbiage

You find it or it finds you? Could it be possible to "get it on the National Health" then?

So if you do not have a purpose in life do you think that it is impossible for someone to help you (re) achieve this? Because if this is possible then it is also possible for this to be done in an institutionalized way. For example ,if drug taking has this effect on some people then they can presumably be helped to regain a purpose in life Your purpose is now as an interpreter of obscure posts?

I didn't mean to quote you at all, marieltrokan . It is the multiquote feature that has me stumped.

dimreepr said "Or did you mean; “Consequence” only enters the conversation if one fails to find ones purpose in life, the consequence of that is often depression because the first step on life’s yellow brick road to contentment is a reason to live?" Not what I meant but ,I agree we need a purpose in life -in the same way that a cyclist will fall on the pavement if he doesn't keep peddling. If we feel our lives have no purpose then the consequences can be similar putting a wild animal in captivity. A "purpose in life" could almost be considered a human right if such an entitlement was practical.