After rejecting his original idea of a static Universe, Einstein favoured the idea of a Universe locked in a perpetual cycle of Big Bang followed by Big Crunch.
So you are in good company, TNT! 😎
Crucially, in an Oscillating Universe, time is endless and beginningless, so there is no need to consider there to have been a beginning of time!
So you are in good company, TNT! 😎
Crucially, in an Oscillating Universe, time is endless and beginningless, so there is no need to consider there to have been a beginning of time!
Why do people get so interested in all this Big Crunch stuff? It really seems not to be at all likely. It's all just expanding. It doesn't care what Einstein thought. The Universe is as we find it.
Reluctantly continuing Galu's segue into the Weyl Tensor, Penrose's Conformal Cyclic Cosmology and the nature of the Cosmos, I have had a delve into General Relativity currently beyond my ability.
Here goes, and this is doubtless full of mistakes, because I don't know a lot about Tensors beyond them treating SpaceTime as a sort of fluid.
Penrose's current wheeze is to consider a Universe that consists just of Gravitational Waves and no Matter. Even the Protons, Electrons, Black Holes and Dark Matter have evaporated. The Photons have redshifted into nothingness, I suppose.
This is not our Universe by my reckoning, nor will it ever be. No-one has ever seen a Proton decay.
He is looking at a a particular solution to the fiercely difficult Einstein Field Equations. Pure Weyl Tensor. Which is pure Wave Theory of Gravitational Waves, or maybe Gravitons in a bulk or classical sense.
OK. This is just breaking up a Matrix into elements. S is a Scalar, and might be the acceleration of Space. W is the Weyl Tensor, which is Traceless, meaning the sum of the main diagonal elements in a 4X4 is zero,
What is the PLAN?
I suspect he is thinking that with a Symmetry comes a Conservation Law, At which point I am lost. But he is thinking he has discovered something about Cosmology in our Universe, but I can't see how.
I suppose this is like separating electromagnetism into electrostatics and Maxwell's Wave theory. Or separating DC from AC in electrics.
Sabine has the advantage of us in understanding the Einstein Field Equations, so is more qualified to comment, But I think everybody is groping in the dark here.
More down to Earth is a nice Star Map site I have found, which shows the current Night Sky when you go to it, and you can click on objects for more information.
https://in-the-sky.org/skymap.php
I was hoping to get a shot of the two big star clusters in Hercules last night, but the weather let me down. But a useful site for identifying things of interest on a proper computer.
Reluctantly continuing Galu's segue into the Weyl Tensor, Penrose's Conformal Cyclic Cosmology and the nature of the Cosmos, I have had a delve into General Relativity currently beyond my ability.
Here goes, and this is doubtless full of mistakes, because I don't know a lot about Tensors beyond them treating SpaceTime as a sort of fluid.
Penrose's current wheeze is to consider a Universe that consists just of Gravitational Waves and no Matter. Even the Protons, Electrons, Black Holes and Dark Matter have evaporated. The Photons have redshifted into nothingness, I suppose.
This is not our Universe by my reckoning, nor will it ever be. No-one has ever seen a Proton decay.
He is looking at a a particular solution to the fiercely difficult Einstein Field Equations. Pure Weyl Tensor. Which is pure Wave Theory of Gravitational Waves, or maybe Gravitons in a bulk or classical sense.
OK. This is just breaking up a Matrix into elements. S is a Scalar, and might be the acceleration of Space. W is the Weyl Tensor, which is Traceless, meaning the sum of the main diagonal elements in a 4X4 is zero,
What is the PLAN?
I suspect he is thinking that with a Symmetry comes a Conservation Law, At which point I am lost. But he is thinking he has discovered something about Cosmology in our Universe, but I can't see how.
I suppose this is like separating electromagnetism into electrostatics and Maxwell's Wave theory. Or separating DC from AC in electrics.
Sabine has the advantage of us in understanding the Einstein Field Equations, so is more qualified to comment, But I think everybody is groping in the dark here.
More down to Earth is a nice Star Map site I have found, which shows the current Night Sky when you go to it, and you can click on objects for more information.
https://in-the-sky.org/skymap.php
I was hoping to get a shot of the two big star clusters in Hercules last night, but the weather let me down. But a useful site for identifying things of interest on a proper computer.
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Redshift is only an observation effect, not a physical state - right!? Photons are all there - all matter has become photons and universe has become totally dark as if there is noting to reflect against, "light" can't be seen anymore even if it is omnipresent. Then all photons are sucked back to one single point where it gets "quite" hot&dense... and 3,2,1 ... boom.
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TNT, I have NO IDEA what is supposed to be going on in "Conformal Cyclic Cosmology". I am merely trying to grasp if there is any interesting things to learn about the Einstein Field Equations here.
There is only one mention of Photons in the Penrose paper I read "The Physics of Conformal Cyclic Cosmology March 31 2025", but I thought an expanding Universe breaks Conservation of Energy?
https://arxiv.org/abs/2503.24263
Penrose may be saying that Black Holes survive to leave an imprint on the next Aeon, maybe rings or such, but this is just a lot of mathematics. I am lost really.
To reiterate:
https://backreaction.blogspot.com/2022/02/will-big-bang-repeat.html
You sort it out. I have more practical projects to do.
There is only one mention of Photons in the Penrose paper I read "The Physics of Conformal Cyclic Cosmology March 31 2025", but I thought an expanding Universe breaks Conservation of Energy?
https://arxiv.org/abs/2503.24263
Penrose may be saying that Black Holes survive to leave an imprint on the next Aeon, maybe rings or such, but this is just a lot of mathematics. I am lost really.
To reiterate:
https://backreaction.blogspot.com/2022/02/will-big-bang-repeat.html
You sort it out. I have more practical projects to do.
'Hawking Points' are bright areas in the CMB that Penrose argues are the results of Hawking radiation from supermassive black holes in a previous aeon.
In response to Penrose's claims of the existence of Hawking points, Stephen Hawking said he could see his own initials in the CMB! 😊
However, there has since been strong observational evidence of numerous previously unobserved anomalous circular spots, of significantly raised temperature, in the cosmic microwave background: https://academic.oup.com/mnras/article/495/3/3403/5838759
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I leave it to you experts. 🤣
My own interest this month in the skies is the Great Globular Cluster in Hercules, M13. Our northern hemisphere version of the extra galactic Magellanic Clouds:
https://en.wikipedia.org/wiki/Messier_13
Now depressing TCrB Nova hunting finds additional interest in the same region... 🙂
My own interest this month in the skies is the Great Globular Cluster in Hercules, M13. Our northern hemisphere version of the extra galactic Magellanic Clouds:
https://en.wikipedia.org/wiki/Messier_13
Now depressing TCrB Nova hunting finds additional interest in the same region... 🙂
I doubt, no, I'm certain (almost) that noting can survive a BB - its such an insane reset - everything has become plasma/gas... and the run for a (short) "while" in the dryer - how could any trace of the "previous" survive that. It just simply can't. No information is transfered from universe n to n+1. Period.
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Again, TNT, you are not alone!
The idea that energy can ‘burst through’ from one universe to the next at what Penrose calls 'Hawking points' has gone down very badly with his peers.
Penrose admits that CCC is "unbelievable on the basis of current cosmology", but adds that cosmology teems with crazy ideas, from the Big Bang to inflation, the theory of exponential expansion of space in the early universe.
https://blog.sciencemuseum.org.uk/sir-roger-penroses-mathematical-art-of-the-cyclic-cosmos/
The idea that energy can ‘burst through’ from one universe to the next at what Penrose calls 'Hawking points' has gone down very badly with his peers.
Penrose admits that CCC is "unbelievable on the basis of current cosmology", but adds that cosmology teems with crazy ideas, from the Big Bang to inflation, the theory of exponential expansion of space in the early universe.
https://blog.sciencemuseum.org.uk/sir-roger-penroses-mathematical-art-of-the-cyclic-cosmos/
That CCC business was a terrific timewaster. Who raised the subject? 🙄
Back to Star Clusters, I have been out in the real world tonight, battling a half Moon and the very indistinct constellation of Hercules in a sky that seemed to be full of white smoke.
I had to drop to my hard-to-focus 35mm lens to have any idea what I was looking at.
The main 4 stars are called the capstone. The brightish triple on the left is as good an identifier as anything.
I will let you share the thrill of discovery with Messier 13 on the right and Messier 92 on the left. These are galactic companions about 25,000 LY away and of about 300,000 stars outside the galactic plane.
https://in-the-sky.org/skymap.php
More smudges! I need a proper telescope... this one is about 5,000 dollars plus the mount and camera, but a useful recce, one feels.
https://astrobackyard.com/m13-globular-cluster/
"Less Opinion, more Astrophysics" is my motto. I wonder what that is in Latin? 🤔
Back to Star Clusters, I have been out in the real world tonight, battling a half Moon and the very indistinct constellation of Hercules in a sky that seemed to be full of white smoke.
I had to drop to my hard-to-focus 35mm lens to have any idea what I was looking at.
The main 4 stars are called the capstone. The brightish triple on the left is as good an identifier as anything.
I will let you share the thrill of discovery with Messier 13 on the right and Messier 92 on the left. These are galactic companions about 25,000 LY away and of about 300,000 stars outside the galactic plane.
https://in-the-sky.org/skymap.php
More smudges! I need a proper telescope... this one is about 5,000 dollars plus the mount and camera, but a useful recce, one feels.
https://astrobackyard.com/m13-globular-cluster/
"Less Opinion, more Astrophysics" is my motto. I wonder what that is in Latin? 🤔
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I had a dig in the 75mm photographs and found what I was looking for now I am more familiar with the constellation of Hercules.
M13 Globular Cluster, 25,000 LY:
And this is M31 Andromeda Galaxy, 2M LY, on the 35mm lens from the other morning's 3.30AM twilight:
Enough to see that these are not stars.
M13 Globular Cluster, 25,000 LY:
And this is M31 Andromeda Galaxy, 2M LY, on the 35mm lens from the other morning's 3.30AM twilight:
Enough to see that these are not stars.
It looks like the failed Soviet Venus probe has a chance of crash landing on Portsmouth, so watch out Steve!
Ground track map showing where the Kosmos 482 Venus probe could fall to Earth
The 495 kg craft is likely to reach the Earth's surface as a single object.
The good news is that, while the risk is nonzero, any one individual on Earth is far likelier to be struck by lightning than to be injured by Kosmos 482.
The updated expected time of entry is 0626 GMT (2.26 a.m. ET) on May 10 (+/- 4.35 hours). https://www.space.com/space-explora...h-today-but-when-and-where-heres-what-we-know
Ground track map showing where the Kosmos 482 Venus probe could fall to Earth
The 495 kg craft is likely to reach the Earth's surface as a single object.
The good news is that, while the risk is nonzero, any one individual on Earth is far likelier to be struck by lightning than to be injured by Kosmos 482.
The updated expected time of entry is 0626 GMT (2.26 a.m. ET) on May 10 (+/- 4.35 hours). https://www.space.com/space-explora...h-today-but-when-and-where-heres-what-we-know
Are you suggesting that Steve have a hearty last meal? ;-)
A sandwich store is the only type of Subway® he'll find in Portsmouth!
A sandwich store is the only type of Subway® he'll find in Portsmouth!
Scientists have calculated that the Universe is going to end sooner than expected! 
That end is postulated to occur when all matter collapses into black holes which, due to the Hawking radiation effect, slowly evaporate until they too disappear without a trace.
To put it into numbers, the Universe is now calculated to end 10 to the power 78 years from now - that is a 1 followed by 78 zeros.
Compare this with the previous prediction of 10 to the power 1,100 years and you can appreciate how much nearer the end is!
However, I wouldn't take this breaking news as a cue to rush out and stock up on bottled water and toilet paper!
https://www.space.com/astronomy/sci...he-universe-will-end-its-sooner-than-expected
That end is postulated to occur when all matter collapses into black holes which, due to the Hawking radiation effect, slowly evaporate until they too disappear without a trace.
To put it into numbers, the Universe is now calculated to end 10 to the power 78 years from now - that is a 1 followed by 78 zeros.
Compare this with the previous prediction of 10 to the power 1,100 years and you can appreciate how much nearer the end is!
However, I wouldn't take this breaking news as a cue to rush out and stock up on bottled water and toilet paper!
https://www.space.com/astronomy/sci...he-universe-will-end-its-sooner-than-expected
The wildest of speculation IMO. Nobody knows if the Universe is heading for the Big Rip as Dark Energy increases, the Big Freeze as everything cools or your beloved Big Crunch if Dark Energy decreases!
I picked up Astronomy Now magazine for the May skies. Lot of discussion of Globular Clusters, and I snapped the bright Messier 5 tonight in Serpens below Arcturus, which I leave you to spot:
But MOST INTERESTINGLY I have snapped Asteroid Vesta, which is the second biggest asteroid after darker Ceres and 200 miles across between Mars and Jupiter:
It's as bright as Uranus at opposition at magnitude 6, which is now. By tomorrow night it will have moved appreciably. I think this is rather cool.
Unless you have a proper PC display, this post just won't really work. Mobile Phones will not give you the full experience.
I picked up Astronomy Now magazine for the May skies. Lot of discussion of Globular Clusters, and I snapped the bright Messier 5 tonight in Serpens below Arcturus, which I leave you to spot:
But MOST INTERESTINGLY I have snapped Asteroid Vesta, which is the second biggest asteroid after darker Ceres and 200 miles across between Mars and Jupiter:
It's as bright as Uranus at opposition at magnitude 6, which is now. By tomorrow night it will have moved appreciably. I think this is rather cool.
Unless you have a proper PC display, this post just won't really work. Mobile Phones will not give you the full experience.