Homogeneous is an assumption i find to be overly simplistic. But i understand why… pencils, paper, no calculators. We now have computers that should be capable of dealing with a more chaotic model.
dave
Eric Kaplan, one of the founders of the franchise (Executive Producer/Writer), well I remember him as little Eric, a junior member of the NYC Math Team (when I was a senior). Certainly, some of us were quite eccentric.
A two-hands-clasped-together-middle-fingers-wiggling-above-and-below trick, performed by a character, I had seen in a Laurel and Hardy (as Legionnaires), and was in the habit of doing at the time.
One of my favorite book-chapters is an Issac Asimov piece on the "powers of ten" (Science, Numbers, and I). Space is so vast, two neighboring stars are like two bacteria alone in an otherwise empty room. On the other hand, if Sol were a basketball, the Solar System would be like marbles or grains of sand over a few kilometers (if I remember right).
Forgive me for saying this, but we don't seem to be capable of singing from the same songsheet in this thread, which is ostensibly a look at theories of Gravity.
We have certain contributors debunking everything known about modern Cosmology and Gravitation in favour of crackpot theories about an "Electric Universe":
https://www.youtube.com/@ThunderboltsProject
Guaranteed to turn your brain to mush, I assure you. Not even wrong. Don't even go there!
I think I may be the only person here who has spent an hour on a fairly low level explanation of General Relativity:
And the hour-long very recent NANOGrav presentation relating to Gravitational Waves in the Cosmos seemed to garner no interest at all:
@planet10 If the Universe is not homogenous or isotropic, the whole thing becomes far more difficult to solve mathematically. But you would hope for some sort of symmetry to be preserved.
There is no short cut to the mathematics of Special and General Relativity, which is not too horrendous given a reasonable period to assimilate a very different way of seeing the Spacetime we apparently inhabit:
https://cmb.wintherscoming.no/theory_GR.php#gr
Einstein's equations are terrifically hard to solve except for simple cases even in the present day. Because they are non-linear. Scwarzschild stationary Black Holes were done in about 1916. Kerr solved Rotating Black Holes in the sixties, and Charged ones fell soon after.
https://www.cantorsparadise.com/the-genesis-of-kerr-solution-dd778e6be598
I am currently reading a PDF Sean Carroll paper "A No-Nonsense Introduction to General Relativity" included in the above webpage. It's all about figuring out The Metric for particular examples. And here it is, a mere 17 pages:
https://cmb.wintherscoming.no/pdfs/carroll_gr.pdf
This is good, because most books on this subject are horrendously expensive. 😎
We have certain contributors debunking everything known about modern Cosmology and Gravitation in favour of crackpot theories about an "Electric Universe":
https://www.youtube.com/@ThunderboltsProject
Guaranteed to turn your brain to mush, I assure you. Not even wrong. Don't even go there!
I think I may be the only person here who has spent an hour on a fairly low level explanation of General Relativity:
And the hour-long very recent NANOGrav presentation relating to Gravitational Waves in the Cosmos seemed to garner no interest at all:
@planet10 If the Universe is not homogenous or isotropic, the whole thing becomes far more difficult to solve mathematically. But you would hope for some sort of symmetry to be preserved.
There is no short cut to the mathematics of Special and General Relativity, which is not too horrendous given a reasonable period to assimilate a very different way of seeing the Spacetime we apparently inhabit:
https://cmb.wintherscoming.no/theory_GR.php#gr
Einstein's equations are terrifically hard to solve except for simple cases even in the present day. Because they are non-linear. Scwarzschild stationary Black Holes were done in about 1916. Kerr solved Rotating Black Holes in the sixties, and Charged ones fell soon after.
https://www.cantorsparadise.com/the-genesis-of-kerr-solution-dd778e6be598
I am currently reading a PDF Sean Carroll paper "A No-Nonsense Introduction to General Relativity" included in the above webpage. It's all about figuring out The Metric for particular examples. And here it is, a mere 17 pages:
https://cmb.wintherscoming.no/pdfs/carroll_gr.pdf
This is good, because most books on this subject are horrendously expensive. 😎
There are no proven theory on 'what is gravity'. Nobody understands it. We have only many assumptions.
Just like some talk as if they know well on time travel.
People watch too many Hollywood movies and assume whatever comes out of a theoretical scientist is truth.
Talk to some scientists to realize how foolish they are on many things. (sorry)
Regards.
Just like some talk as if they know well on time travel.
People watch too many Hollywood movies and assume whatever comes out of a theoretical scientist is truth.
Talk to some scientists to realize how foolish they are on many things. (sorry)
Regards.
He's missing the point that gravitational attraction never reaches zero - as far as we are aware. Increasing distances just mean that it takes longer to show an effect. 😉 Things get rather strange when an expanding universe gets thrown in but gravity appear to overcome that.
The term a black hole has swept out is a typical misleading comment. They don't sweep anything out. They attract stuff. Physics as we know them in terms of density and other factors break down and in some cases not just on black holes.
One factor I have wondered about on black holes is ok their mass means light can not escape but what happens if the mass means that escape velocity reaches 2C yet stuff attracted at the speed of light has some interesting mass aspects.
Of interest
Black holes are not decaying because there's an infalling virtual particle carrying negative energy; that's another fantasy devised by Hawking to "save" his insufficient analogy. Instead, black holes are decaying, and losing mass over time, because the energy emitted by this Hawking radiation is slowly reducing the curvature of space in that region. Once enough time passes, and that duration is enormous for realistic black holes, they will have evaporated entirely.
From
https://www.forbes.com/sites/starts...-about-how-black-holes-decay/?sh=3d6a03414e63
If this idea is true they evaporate once their gravity can't attract "real matter" at a rate that makes up for losses. LOL Otherwise they wouldn't exist.
Thank you for a critical contribution;-)
One problem is the reduction to low-complexity models: a black hole and a star. Without beginning. Without environment. Ideals, without physical reality.
But do not describe the observations;-)-; Ergo: unscientific;-)-;
Last edited:
I don't think there is much point for many people in going there and trying to fully follow the maths. Those provide the "proofs" and predictions that so far hold up where they can be observed. The basic thought experiments are easily understood relating to frames of reference even in a Newtonian sense. Einstein provides more accuracy.
Then comes E=MC^2, matter and energy equivalence and gravity. Also time. We can't see curved space.We can when plots are produced. The words dimension sometime gets used. These do not have directions in a conventional sense other than when they are graphically plotted. Gravity sets the curvature in these and using those as a model fit well with a number of observable factors that Newton can't explain.
I have a book somewhere by an extremely famous bloke. Just looked for it as can't remember which one it was. It goes through earlier theories in great detail and clarity. When it comes to relativity he comments that if he did the same with that the book would be enormous. No one would print or even buy it so switches to maths.🙁 I was really looking forwards to getting to that section.
Who believes that "space" and "time" could be expanded or bent, also believes that points and lines of a coordinate system could be broadened and bent;-) Imaginations of kids;-)
"Space" and "time" are concepts that do not belong in physics. They are everyday terms. Distances and counts would be more appropriate.
Is "space" even a "physical quantity" that could be calculate around with;-? Could one allow a "space-time" "physically" at all;-? Or is that also just mathematician nonsense, for the sake of simplicity;-? Look for Einsteins "mathematicians"-)
Questions, questions, questions;-)
"Space" and "time" are concepts that do not belong in physics. They are everyday terms. Distances and counts would be more appropriate.
Is "space" even a "physical quantity" that could be calculate around with;-? Could one allow a "space-time" "physically" at all;-? Or is that also just mathematician nonsense, for the sake of simplicity;-? Look for Einsteins "mathematicians"-)
Questions, questions, questions;-)
Because no concept in physics and engineering ever used time as a parameter.
It must be nice to be in a position where you have to ignore the laws of physics.
It must be nice to be in a position where you have to ignore the laws of physics.
We do not have any proven theory for gravity yet.
We have proved calculations on the effect of gravity. Nobody knows what is gravity.
We are only able to see the effects of it.
There are always good things in understanding science. But unproven theory is not proven science,
But the current story may be good for some, until a new cinema is released.
We are already witnessing the effects of unproven science pushed upon us now in virus, sex, the gas of life etc.
Just because 93% of noname scientists agreed so, has become a unquestionable science now. No debates allowed, and it is the basis for the agenda
Many of the science as we are told in the past 10 years or so, we even do not know who made these research, or proved it etc. No names at all.
Some feel development in science has stopped some 30 years ago.
Regards.
No short cut indeed! It all hinges on a deep understanding of tensors and differential geometry. 😱
There's a swathe of tensors to get one's head around, including:
- The metric tensor
- The Ricci curvature tensor
- The stress-energy tensor
- The Einstein tensor
The left hand side of the above equation is the Einstein tensor, thus giving this simplifed form:
The Einstein tensor represents how spacetime is warped or curved by matter and energy.
The stress-energy tensor (a measure of the stress on spacetime) has to be extremely large to produce an appreciable amount of warp or curvature.
It takes an object like the Earth (all 6 trillion trillion kilograms of it) to stress spacetime and warp it to the degree with which we are familiar.
That's as far as I am able to go - the mathematics is way above my pay grade!
There is no such thing as a proven theory!
In science, a theory can never be proven to be true beyond any doubt.
Scientific knowledge is subject to revision when new evidence or better explanations come along.
Your premise of "unproven science" smacks of conspiracy theory which I hope can be excluded from this thread.
Of course we don't know what gravity is!
As you say, science can only describe and predict its effects.
;-)
Nonsense in mathematic: Spacetime ist not bendable. It is a concept only;-)
It is kids gimmick;-)
If you already have problems to keep apart object and concept with a low-complex section of "universe", like distance and tact, how do you want to talk about highly complex sections of "universe", like psyche, society, "science"?
And how could one introduce you for example to "science";-?!