I have been out and about tonight with my camera and telescope!
22.20 BST, 22 June 2023, Portsmouth, UK looking West after sunset. Venus is a 40% Crescent at the moment and subtends about 30 Arcseconds, whereas the 25% Crescent Moon subtends about 30 Arcminutes or half a degree. Surprisingly I could not discern the crescent of Venus at less than X90 Telescope Magnification, so this crescent is not going to be visible with binoculars IMO. But still a splendid sight.
On the subject of the Torus, raised by cumbb, it is an important geometrical object, but serious physicists use it mainly in string theory. And in a 4 dimensional form:
https://en.wikipedia.org/wiki/Torus#n-dimensional_torus
https://en.wikipedia.org/wiki/AdS/CFT_correspondence
de Sitter Space has positive curvature, Anti de Sitter Space has negative or flat curvature. Cosmologists say we live in de Sitter Space. I should stop there, before I make a fool of myself. My knowledge is limited until I read the Sean Carroll book. It's all quite difficult. 🙁
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I thought you were much farther away enjoying your holidays, Steve! 😉
Pure de Sitter space is a solution to the Einstein equations with a positive cosmological constant and no other matter sources.
However, cosmologists are not interested in pure de Sitter space because they know that there is other matter in the universe.
Modern cosmological theory is based on the Friedmann - Lemaitre - Robertson - Walker (FLRW) metric.
https://phys.libretexts.org/Courses/Skidmore_College/Introduction_to_General_Relativity/07:_Cosmology/7.02:_The_Friedmann-Lemaitre-Robertson-Walker_Metric
That's as far as I have got and probably as far as I will ever get! 🤓
Holiday put on hold due to unexpected developments of a personal nature. I have been poorly. 😢
My alternate immediate plan is to mount an expedition to nearby Worthing or, better still, Winchester, because it is a more interesting day out. To wit, visit the Waterstones bookshop in search of this splendid tome, which they both claim to stock:
I made a mistake on Space Curvature. AdS Space is always negative curvature:
For Flat Space we should be thinking Minkowski Space, which I always think of as a Gaussian Curvature problem, much as I know you hate Gaussian Curvature:
https://www.diyaudio.com/community/...e-expanding-into.258035/page-346#post-6783165
https://en.wikipedia.org/wiki/Anti-de_Sitter_space
But a flat plane will work as well as a cylinder with Gaussian Curvature, IMO. Omega = <1, 1, >1 ends up in the same place as K = -ve, 0, +ve to a mathematician like myself.
Happy with that, as far as I have got. I do appreciate that we must add in an extra factor or two to Spacetime curvature for Mass and Energy in whatever form it lies around us.
"I think I'll stop here", as Andrew Wiles famously said.
My alternate immediate plan is to mount an expedition to nearby Worthing or, better still, Winchester, because it is a more interesting day out. To wit, visit the Waterstones bookshop in search of this splendid tome, which they both claim to stock:
I made a mistake on Space Curvature. AdS Space is always negative curvature:
For Flat Space we should be thinking Minkowski Space, which I always think of as a Gaussian Curvature problem, much as I know you hate Gaussian Curvature:
https://www.diyaudio.com/community/...e-expanding-into.258035/page-346#post-6783165
https://en.wikipedia.org/wiki/Anti-de_Sitter_space
But a flat plane will work as well as a cylinder with Gaussian Curvature, IMO. Omega = <1, 1, >1 ends up in the same place as K = -ve, 0, +ve to a mathematician like myself.
Happy with that, as far as I have got. I do appreciate that we must add in an extra factor or two to Spacetime curvature for Mass and Energy in whatever form it lies around us.
"I think I'll stop here", as Andrew Wiles famously said.
Sorry to hear you've been poorly, Steve, but glad to know you feel able to get out and about.
I believe that Andrew Wiles was quite good at maths, a bit like yourself! 😉
https://plus.maths.org/content/andrew-wiles-what-does-if-feel-do-maths
I believe that Andrew Wiles was quite good at maths, a bit like yourself! 😉
https://plus.maths.org/content/andrew-wiles-what-does-if-feel-do-maths
TBH, I Minor in Mathematics. My Major interest is Atomic Physics.
What has Radioactivity ever done for US? It's a serious Scientific Question...
The delicious Ruby Grapefruit was created as a result of Gamma Ray Radiation.
What has Radioactivity ever done for US? It's a serious Scientific Question...
The delicious Ruby Grapefruit was created as a result of Gamma Ray Radiation.
The Effect of Gamma Rays on Man in the Moon Marigolds
Not many people know that. But, TBH, I can't think of much else good about Radioactivity. 🙁
Well, it has taught me what the first three letters of the Greek alphabet are! 😀
And it has kept Homer in a job:
Many cancer patients have been treated with Cesium irradiation. Some of them survived.
I used to laugh when a " no nuke zone" road sign with the tri-logo appeared at the entrance to Louisville off the Watterson loop. In the 80's. U of L has two hospitals in that zone. Jewish Hospital is in there, too.
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https://www.triumfinnovations.ca/ne...in-niche-market-of-medical-isotope-production
https://en.wikipedia.org/wiki/TRIUMF
Just next door one of the largest radioactive isotope for medicine factories on the planet.
dave
https://en.wikipedia.org/wiki/TRIUMF
Just next door one of the largest radioactive isotope for medicine factories on the planet.
dave
Radioactivity like viruses have always been there.
Fear it or not, it belongs to life on the planet.
Fear it or not, it belongs to life on the planet.
Radioactivity may have set the stage for the origin of life - on Earth and elsewhere - via the radiolysis of water.
https://www.quantamagazine.org/radi...underground-and-inside-other-worlds-20210524/
I don't quite know why I was rambling about Radio-activity lately, but I suppose it was Science anyway,.. 😳
Back on-topic. Exciting Live Stream today about Gravity:
1300 EST (New York), 1800 BST (London, UK):
https://nanograv.org/
It's all about new low frequency measurements of the Gravitational Waves from Colliding Galaxies and the ourageously big Black Holes within:
https://www.theguardian.com/science...s-detect-cosmic-bass-note-gravitational-waves
Previously LIGO detected a much more rapid and accelerating ripple from two merging Black Holes:
https://www.theguardian.com/science...scovery-hailed-as-breakthrough-of-the-century
I think the idea is two huge merging gravity wells must lose energy to balance the sums of Kinetic and Potential Energy (The Lagrangian E = T - V), and this Energy takes the form of spreading ripples of Gravitational Waves carrying enormous Energy through Spacetime. This new phenomenen is much lower frequency however. I am sure trusty Einstein's General Relativity will be shown to work, as ever.
Can't wait! 😎
Back on-topic. Exciting Live Stream today about Gravity:
1300 EST (New York), 1800 BST (London, UK):
https://nanograv.org/
It's all about new low frequency measurements of the Gravitational Waves from Colliding Galaxies and the ourageously big Black Holes within:
https://www.theguardian.com/science...s-detect-cosmic-bass-note-gravitational-waves
Previously LIGO detected a much more rapid and accelerating ripple from two merging Black Holes:
https://www.theguardian.com/science...scovery-hailed-as-breakthrough-of-the-century
I think the idea is two huge merging gravity wells must lose energy to balance the sums of Kinetic and Potential Energy (The Lagrangian E = T - V), and this Energy takes the form of spreading ripples of Gravitational Waves carrying enormous Energy through Spacetime. This new phenomenen is much lower frequency however. I am sure trusty Einstein's General Relativity will be shown to work, as ever.
Can't wait! 😎
Gravity and mass are really weird, I can imagine a double slit experiment for almost any particle but drew a complete blank for graviton and higgs boson.
Everything on space is still theory. Some dominate at one time, fails and another one takes over and fails and never ends....
That would be like saying, "previously scientists thought elephant was like a wall, new research shows that elephants are like stone pillars. And strangely enough, elephants can exhibit properties like a wall or a pillar at the same time." One of the scientist was quoted saying "this research needs more funding and many new things about elephants can be discovered in about ten years time"
Whatever astronomical telescopes show as star and planet is just a mm dia blurred dot. Rest story from the scientists are imaginary.
They have to earn their bread and bring in new things, in theory but told to you as a discovery to continue the funding.
In reality, astronomy has not expanded that much from a thousand year ago. Old wine in new bottle.
Just my view.
Regards.
That would be like saying, "previously scientists thought elephant was like a wall, new research shows that elephants are like stone pillars. And strangely enough, elephants can exhibit properties like a wall or a pillar at the same time." One of the scientist was quoted saying "this research needs more funding and many new things about elephants can be discovered in about ten years time"
Whatever astronomical telescopes show as star and planet is just a mm dia blurred dot. Rest story from the scientists are imaginary.
They have to earn their bread and bring in new things, in theory but told to you as a discovery to continue the funding.
In reality, astronomy has not expanded that much from a thousand year ago. Old wine in new bottle.
Just my view.
Regards.
Basically, it's very simple: most can't distinguish "space" from "room". They cannot imagine that space is a idea. Because they probably have no idea of imagination;-) It must be an intellectual feat;-) That's why they always come up with "borders", "walls", in whatever form and arrangement: balloons, donuts, loops;-)
If English native language is: synonyms for "space" are also gap, blanc, hole, deficiency, omission, vacancy...-)
Aside(-:
If English native language is: synonyms for "space" are also gap, blanc, hole, deficiency, omission, vacancy...-)
Aside(-:
There is some truth in that if you knock a zero off and make it 100years. Some ideas that are hard to prove are still around such as cephied variables and star evolution etc.
Astro physics is often observe and find a theory to fit. The most recent finding that didn't fit that I am aware of occurred when long term movement of various things was studied. Mass and the degree of movement didn't fit so along comes dark matter. Detect that or assume the sums are correct and calculate this missing mass?
Fashion can figure as well. There was an astronomer who spent his time observing things that do not fit in with an expanding universe. His funding was withdrawn some years ago. That doesn't mean these do not exist. Anyone having different ideas about the subject would have great difficulty getting them accepted. There has been other similar areas.
Gravity and gravity waves etc. Good run down on the best approximation of testing if gravity travels at the speed of light.
https://www.nobelprize.org/prizes/physics/1993/press-release/
The whole thing is based on theoretical objects. Only 4 free reads on this one which details other methods
https://www.forbes.com/sites/starts...y-move-at-the-speed-of-light/?sh=9fb63762110f
Black holes - some one did some sums. Escape velocity with mass. Ideas grow from that to make thing fit. If the idea of galaxies containing one is correct all will finish up in one. Galaxy shapes are interesting but need to be seen. SO is a spiral's disk shape with no arms
https://www.austincc.edu/jheath/Stellar/Hand/spvsel.htm
Metals etc - well they came from super nova etc. An explanation for the energy needed to create them.
😉 The universe can't be infinite any more even if it is. The big bang has a lot to answer for. LOL I wonder due to too much reading but modern street lighting has removed my interest in astronomy, Sodium lighting has more or less gone.
It should be stressed that dark matter is not yet a fact, but is still hypothetical.
Responsible scientists require to examine the implications and consequences of this particular hypothesis for the rest of the Universe and this is where dark matter shows promise.
By introducing dark matter, scientists can arrive at an entirely new picture of how structure formed in the Universe.
Modern data sets from large-scale universe structure surveys show remarkable agreement between observations and the dark matter hypothesis.
Pity we don't have a laughing face graphic to tag mandu's post 674.
npr.org has covered the pulsar timing gravity wave story for those outside the UK that find stories cut off after a few lines by the Guardian. https://www.npr.org/2023/06/28/1183878163/new-gravitational-wave-supermassive-black-hole
npr also doesn't lock my op system up as inevitably as cnn cbsnews msnnews ect.
npr.org has covered the pulsar timing gravity wave story for those outside the UK that find stories cut off after a few lines by the Guardian. https://www.npr.org/2023/06/28/1183878163/new-gravitational-wave-supermassive-black-hole
npr also doesn't lock my op system up as inevitably as cnn cbsnews msnnews ect.
Galactic collisions are very common as the distances between galaxies are only approximately equal to 20 times the diameter of a galaxy.
Imagine a model in which the diameters of the Milky Way galaxy and the Andromeda galaxy are represented by table tennis balls. On this scale the galaxies would only be 1 metre apart.
By comparison, collisions between stars within galaxies are extremely rare.
Imagine a model in which the diameters of the Sun and Proxima Centauri are represented by table tennis balls. On this scale the distance between the two stars would be 1100 kilometres.