Yes, I also see the phrase "emergent behaviour" being used.
"An emergent behavior of a physical system is a qualitative property that can only occur in the limit that the number of microscopic constituents tends to infinity."
It has been theorised that gravity emerges from a three dimensional quantum vacuum and that the curvature of space-time is mathematically linked to the vacuum's variable energy density.
Don't ask me to explain it! 😵
I've been looking further into emergent gravity. Eric Verlinde is behind it all: https://en.wikipedia.org/wiki/Erik_Verlinde
The idea hinges on the existence of a close connection between general relativity and thermodynamics.
Thermodynamics is a framework to describe how very large numbers of individual, constituent particles behave.
Could spacetime is made of small elements whose collective motion gives rise to the force we call gravity?
Emergent gravity has been touted to replace the dark matter hypothesis, but still has a long way to go to outcompete it.
I gleaned the above from Sabine Hossenfelder's article:
https://www.forbes.com/sites/starts...atter-about-to-be-killed-by-emergent-gravity/
Warning! She mentions "holographic" entropy! 😵
The idea hinges on the existence of a close connection between general relativity and thermodynamics.
Thermodynamics is a framework to describe how very large numbers of individual, constituent particles behave.
Could spacetime is made of small elements whose collective motion gives rise to the force we call gravity?
Emergent gravity has been touted to replace the dark matter hypothesis, but still has a long way to go to outcompete it.
I gleaned the above from Sabine Hossenfelder's article:
https://www.forbes.com/sites/starts...atter-about-to-be-killed-by-emergent-gravity/
Warning! She mentions "holographic" entropy! 😵
Attachments
I would think that kind of nomadic star is almost certainly one that originated within our Milky Way galaxy, whereas the extragalactic star would be much rarer to see within the galaxy. A good sign that a star has origins outside our galaxy would be that it's going many times faster (perhaps several orders of magnitude faster!) than other stars in the area. There's certainly a lot of "empty space" between galaxies, but I was quite surprised at the claim that up to 50 percent of stars are outside galaxies.
That's correct, I should have said "galaxy" and not "universe".
Scholz's star passed within one light year of the Sun at the time modern humans were just beginnung to migrate out of Africa.
I didn't know about Scholz's star... a rare gap in system7's General Knowledge.. 🙁
Naturally scientific reference supplied, we are after all, Professional Scientists... we follow the Scientific Method. 😎
https://en.wikipedia.org/wiki/Scholz's_Star
Evidently a Milky Way wanderer, actually a binary of a red dwarf and a brown dwarf, at a mere 82.4 km/s velocity. I doubt it has enough velocity to leave the Milky Way Galaxy. FWIW, our own Sun is heading towards bright Vega (currently 22 ly away) at a good rate. About 20 km/s AFAIK. We shall close the distance to within a light year in the distant future. At which point Vega will be way bright!
https://en.wikipedia.org/wiki/Vega
I don't want to spend much time on Eric Verlinde, considering him the worst sort of crank, even if I appreciate his idea that all is INFORMATION in the Quantum World, in which I believe.
Roger Penrose has produced a sort of Feynman Diagram about Black Holes: I know about analytic continuation. Arises in the problem of evaluating 0^0. 1, FWIW.
More junk science, IMO. Even String Theory is absolutely useess on Quarks and Hadrons, and if i has any hope might advance theories of Gravity. For now we prefer the Standard Model of Hadrons.
Way I am going is that Einstein's semi-classical Theory of General Relativity and Gravity will be superceded by a Quantum Theory of Gravity. It will, of course, approximate to current ideas about Black Holes, but make new predictions. Perhaps that they don't evaporate!
My money is on Gravastars:
https://en.wikipedia.org/wiki/Gravastar
A solution to the extremely difficult General Relattiivity Black Hole solutions, where Spin, Mass, Charge and possibly Magnetization are included, but Quantized!
Fixes all my concerns about Black Hole Entropy and Information.
https://en.wikipedia.org/wiki/Claude_Shannon
My specialist subject! I know this game.
What does it mean, my friends? We considered the possibility that we live inside a Black Hole. I am thinking we might be living inside a Garavastar!
See it's Quantized! Which is a game changer! I like it. 😀
Naturally scientific reference supplied, we are after all, Professional Scientists... we follow the Scientific Method. 😎
https://en.wikipedia.org/wiki/Scholz's_Star
Evidently a Milky Way wanderer, actually a binary of a red dwarf and a brown dwarf, at a mere 82.4 km/s velocity. I doubt it has enough velocity to leave the Milky Way Galaxy. FWIW, our own Sun is heading towards bright Vega (currently 22 ly away) at a good rate. About 20 km/s AFAIK. We shall close the distance to within a light year in the distant future. At which point Vega will be way bright!
https://en.wikipedia.org/wiki/Vega
I don't want to spend much time on Eric Verlinde, considering him the worst sort of crank, even if I appreciate his idea that all is INFORMATION in the Quantum World, in which I believe.
Roger Penrose has produced a sort of Feynman Diagram about Black Holes: I know about analytic continuation. Arises in the problem of evaluating 0^0. 1, FWIW.
More junk science, IMO. Even String Theory is absolutely useess on Quarks and Hadrons, and if i has any hope might advance theories of Gravity. For now we prefer the Standard Model of Hadrons.
Way I am going is that Einstein's semi-classical Theory of General Relativity and Gravity will be superceded by a Quantum Theory of Gravity. It will, of course, approximate to current ideas about Black Holes, but make new predictions. Perhaps that they don't evaporate!
My money is on Gravastars:
https://en.wikipedia.org/wiki/Gravastar
A solution to the extremely difficult General Relattiivity Black Hole solutions, where Spin, Mass, Charge and possibly Magnetization are included, but Quantized!
Fixes all my concerns about Black Hole Entropy and Information.
https://en.wikipedia.org/wiki/Claude_Shannon
My specialist subject! I know this game.
What does it mean, my friends? We considered the possibility that we live inside a Black Hole. I am thinking we might be living inside a Garavastar!
See it's Quantized! Which is a game changer! I like it. 😀
Last edited:
It is now claimed that the notion of "hairy" black holes bridges the gap between general relativity and quantum mechanics.
https://www.bbc.co.uk/news/science-environment-60708711
New research claims that the information paradox may be resolved by showing that black holes are not only described by mass, spin and charge, but also by an additional property called "hair".
According to the laws of general relativity, what falls into a black hole, stays in a black hole.
However, "hair" is a quantum imprint in the gravitational field outside a black hole which retains a memory of what went into the black hole.
So, information may not be lost inside a black hole after all!
I am cautious on trying to understand General Relativity and Quantum Mechanics. Deeply difficult problems... involving 4 dimensions of SpaceTime which are beyond our everyday experience.
The no-hair theory is something I have encountered, but didn't spend a lot of time considering. On a 2-sphere problems arise, on 2 or 3-torus (aka a doughnut) there is no problem at all! How it is.
Quoting Prof. Ian Stewart, a Mathematician with an interest in Physics, like myself:
"We've got used to the existence of black holes, but they occupy a realm where relativity and quantum theory overlap and clash. We don't really know what physics to use, so cosmologists try their best with what's avaoilable.
The last word on black holes is not yet in, and there is no reason to suppose that our current understanding is complete - or correct."
Nicely put, IMO.
I prefer problems with a reasonable chance of being solved.
Is there LIFE on Europa? It has water...
I was out and about with my telescope the other night:
I definitely identified Ganymede as the brightest Jovian Moon!
We are sending a space probe!
https://www.bbc.co.uk/news/science-environment-64336398
Let's hope it doesn't all blow up at launch! 🙁
The no-hair theory is something I have encountered, but didn't spend a lot of time considering. On a 2-sphere problems arise, on 2 or 3-torus (aka a doughnut) there is no problem at all! How it is.
Quoting Prof. Ian Stewart, a Mathematician with an interest in Physics, like myself:
"We've got used to the existence of black holes, but they occupy a realm where relativity and quantum theory overlap and clash. We don't really know what physics to use, so cosmologists try their best with what's avaoilable.
The last word on black holes is not yet in, and there is no reason to suppose that our current understanding is complete - or correct."
Nicely put, IMO.
I prefer problems with a reasonable chance of being solved.
Is there LIFE on Europa? It has water...
I was out and about with my telescope the other night:
I definitely identified Ganymede as the brightest Jovian Moon!
We are sending a space probe!
https://www.bbc.co.uk/news/science-environment-64336398
Let's hope it doesn't all blow up at launch! 🙁
Nothing generates gravity. It is simply the progression to the ultimate future along curve space time. Resistance is admirable and perfectly useful in solar and planetary life spans, but in cosmological terms... futile. You will end up in a black hole somewhere and that black hole in another until nothing exists but a few distant beyond their own horizon black holes of the end of time. The complete stopping of time. The end of matter and energy and time within. Cold, quiet, dead space between.
On a brighter note it will be NH Spring soon!
Have a nice weekend.
On a brighter note it will be NH Spring soon!
Have a nice weekend.
Member
Joined 2009
Paid Member
I prefer the emerging theory that black holes are actually fuzz-balls, a shell that's the thickness of the planck length and made of quantum strings. All the mass is in this shell. There is no singularity, actually there's no inside - the universe ends with the fuzzy shell and there is no spacetime inside it.
I've read that this proposed form for black holes have behaviors that are consistent with the traditional Hawking-Einstein models and that it resolves all the worrying paradoxes.
Given that they were a “hoax” not that many decades ago it is fully expected that we only have a glimmer of what is happening.
dave
Given what we have found out exporing chaos theory in the last 50 years it seems to me that fuzzy is likely in the right direction.
dave
On a brighter note, we are talking of a timescale of hundreds of trillions of years before the "Black Hole Era" of the universe comes into being.
On such a scale the existence of the human race would register as but the briefest spark in the early history of the universe.
Member
Joined 2009
Paid Member
in an extrapolation of the anthropic principle, the universe exists because of us, we are not just a spark
I see this described as a "wild" presumption of string theory.
It supposes that fundamental strings stop working together and become tangled to form a large ball of strings - a fuzzball.
It would appear that, even as a mathematical possibility, fuzzballs are fuzzy!
Perhaps LIGO may be able to tell the difference between black holes and stringy fuzzballs - who knows?
https://en.wikipedia.org/wiki/Fuzzball_(string_theory)
Attachments
I have been busy reading "Calculating the Cosmos" by Professor Ian Stewart:
A most interesting Tome, in which I learnt about the Interplanetary Highway, whereby we launch Space Probes to the furthest planets with little Energy but lots of Time by employing the slingshot effect.
TBH, the whole thing was riddled with mistakes! I ended up marking them in the margin in pencil!
On page 130, Prof. Stewart stated that the Pole Star Polaris is in Ursa Major(?). A child of ten knows it is in Ursa Minor!
On page 157 he gave this dubious illustration of Fusion reactions in stars:
What garbage! You can see that (top index) Baryon number doesn't add up! This is the correct sequence.
On page 245 he states that all Galaxies are moving away from us. More twaddle. We are due to collide with Andromeda, M31 in 2 Billion years. And anything could happen then.
My current plan is to learn Classical Field Theory next. Involving the Lagrangian sum of Kinetic Energy of planetary motion and the Potential Energy Field of Classical Gravity. Quantum Gravity can wait for further studies.
But really, how hard can it be with my sort of clear analytic mind? 😀
A most interesting Tome, in which I learnt about the Interplanetary Highway, whereby we launch Space Probes to the furthest planets with little Energy but lots of Time by employing the slingshot effect.
TBH, the whole thing was riddled with mistakes! I ended up marking them in the margin in pencil!
On page 130, Prof. Stewart stated that the Pole Star Polaris is in Ursa Major(?). A child of ten knows it is in Ursa Minor!
On page 157 he gave this dubious illustration of Fusion reactions in stars:
What garbage! You can see that (top index) Baryon number doesn't add up! This is the correct sequence.
On page 245 he states that all Galaxies are moving away from us. More twaddle. We are due to collide with Andromeda, M31 in 2 Billion years. And anything could happen then.
My current plan is to learn Classical Field Theory next. Involving the Lagrangian sum of Kinetic Energy of planetary motion and the Potential Energy Field of Classical Gravity. Quantum Gravity can wait for further studies.
But really, how hard can it be with my sort of clear analytic mind? 😀
But with a few 'Minor' mistakes? It seems that the Prof. needs to improve his proofreading strategies! 😊
I'll leave it up to Steve to do the mathematical legwork, but feel a little explanatory background may be appropriate.
Whereas Newton's laws of motion are based on the vector quantities force and momentum, Lagrangian mechanics is based on the scalar quantities kinetic energy and potential energy.
Joseph-Louis Lagrange's scalar approach made it easier to analyse the orbits of planets and comets, and is now applied to spacecraft trajectories.
https://www.famousscientists.org/joseph-louis-lagrange/