Roy Kerr who discovered the metric for real rotating black holes disagrees with Penrose/Hawking on the existence  of singularities in real black holes, 'a foundation built on sand'.

No quantum gravity required

Now mainstream ?

If anyone knows then surely its the person who discovered the Kerr metric? https://arxiv.org/abs/2312.00841

1 hour ago, saac said:

A point often missed by the armchair physics fans beloved of U Tube/Tiky Toc who freely criticize with what must surely be little understanding. 

Jim 

I taught myself the maths and physics of GR to tensor level from the standard grad level books ( beyond what I did at  3rd year BSc specialisation) I don't claim to be an expert but I know my Riemann tensor from my Ricci\Weyl tensor from my Ricci scalar, my covariant from my contravariant  and now that I'm about to be semi retired I'm going back to study for a physics masters to enjoy it with a 'desire' to to do further study afterward if possible (I can afford to self fund  if required) . No need to find a job at the end or get involved in the typical student social activities 😉 

I think criticism (I don't mean flat earth and other mystic woo woo)  is an important part of science because it forces physicists to defend what they preach - they often disagree after all

Do real physicists really have their feelings hurt if they are criticised on youtube?

5 minutes ago, andrew s said:

I know that. I was pointing out an alternative approach based on speed measurement. One way to avoid systematic error, which are very difficult to identify,  is to use very different techniques. 

As you say they oscillate so they should have some mass. There are a  number of unexplained anomalies within the standard model of particle physics,  as there are within the LCDM and come to that any theory you care to mention.

They are still currently the best we have. It's not for lack of effort by theoretical physicist but  no one seems to have made any significant advances in a long time.

Regards Andrew 

Yes I appreciate that, point is that there are still many mysteries to solve, we don't know everything and we may even have got some assumptions wrong? (not picking on anything specific)

42 minutes ago, andrew s said:

An indirect way to approach the mass of a neutrino is to measure its speed. This gives a speed difference from that of light of 2x 10^-9 from the supernova 1987A. Whatever the mass it's very small.

When trying to measure a value you not only have to worry about statistical variations but also systematic errors. The latter are very hard to eliminate. 

As an example this is the history of the speed of light measurements

There looks to be a systematic difference between the early and late results.

Regards Andrew 

In radioactive decay the negative mass square is a consequence of conservation of momentum and energy of the resultant positron and neutrino (since thats its 'job') not a speed measurement.  It isn't even an unusual result, there are some people who take this literally but most state that it is systematic error 'somewhere' since its 'obvious' that it cant be negative and there it must be positive. I make no claim for either viewpoint, my beef is that if there is systematic error then someone should identify where. The most successful standard model says neutrino mass = 0 and therefore must travel at c (but they can't since they oscillate). 

3 hours ago, DarkAntimatter said:

So a confidence interval around the measurement would lie mostly in the negative energy squared region (and therefore imaginary mass)?  Or what am I misunderstanding?

Whats to misunderstand? 

Plenty of articles of varying technicality in google , question is why. I always remember this one because I did a third year project involving this and I also measured a negative value

https://www.google.com/search?q=negative+energy+squared+of+neutrino&oq=negative+energy+squared+of+neutrino&gs_lcrp=EgZjaHJvbWUyBggAEEUYOTIGCAEQRRg80gEMNjI0NTQwNzBqMGo0qAIAsAIA&sourceid=chrome&ie=UTF-8

4 hours ago, Ags said:

Ok, so if I held a bowling ball made of imaginary mass, what would it feel like? Would a few imaginary kilos feel the same as a few real kilos?

The energy squared (which is proportional to mass squared) of the neutrino is often measured to be negative in radioactive decay but within certain error and is taken as positive, it gets measured to be a negative number but there is just enough error in measurement  that mass could be slightly positive by convention since imaginary mass doesn't exist. 

While looking for articles on Black Hole volumes I found this interesting post from Roy Kerr (discoverer of Kerr  Black Hole metric), quite interesting for the science and the human factor, reputation and how untested assumption can become uncontested fact...(maybe?, personally I've seen a lot of that in my line of work 😉 )

profile

'constructed the Kerr black hole metric, 1963. proved that the Penrose and Hawking singularity theorems are invalid, since their assumption that affine parameters cannot be bounded on a light ray is false.'

https://www.quora.com/What-would-a-black-hole-look-like-from-inside-the-event-horizon 

'If the body is stellar sized then it’s density will be roughly similar to that of a neutron star. If it is super duper sized then it is quite possible that the gravity will be earth like and so a ship could actually land on it. It could even take off again but will never be able to cross the inner horizon. incoming objects will be seen as they come in from the real world, no problem!'  

Also, surely all real Black Holes rotate so why do we talk about Schwarzschild BH's and their central singularity, shouldn't they all be Kerr BH's?

16 hours ago, Mr Spock said:

Not really an astronomy topic though is it 

It could be if I/you are a boltzmann brain 😉 

19 minutes ago, Mr Spock said:

Definitions of Fact, Theory, and Law in Scientific Work.
Science uses specialized terms that have different meanings than everyday usage. These definitions correspond to the way scientists typically use these terms in the context of their work. Note, especially, that the meaning of “theory” in science is different than the meaning of “theory” in everyday conversation.

• Fact: In science, an observation that has been repeatedly confirmed and for all practical purposes is accepted as “true.” Truth in science, however, is never final and what is accepted as a fact today may be modified or even discarded tomorrow.
• Hypothesis: A tentative statement about the natural world leading to deductions that can be tested. If the deductions are verified, the hypothesis is provisionally corroborated. If the deductions are incorrect, the original hypothesis is proved false and must be abandoned or modified. Hypotheses can be used to build more complex inferences and explanations.
• Law: A descriptive generalization about how some aspect of the natural world behaves under stated circumstances.
• Theory: In science, a well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses.

Sounds like inconsistent semantics, I'm sure people can find many instances so I don't have to much of a problem

“When I use a word,’ Humpty Dumpty said in rather a scornful tone, ‘it means just what I choose it to mean — neither more nor less.’

I know what you are saying
Yet we do say MOND Theory, String Theory, etc which hardly fit the above definition, yet Second Law of Thermodynamics and Entropy is a sacred cow and incorporated many theorems

1 hour ago, Mr Spock said:

Theories never become facts. It is the other way round - theories are explanations of facts. 

Laws of Thermodynamics, Newtons Laws, etc?

1 hour ago, saac said:

Nope, you hang the mass on the hook, hold it and it registers the weight. Let go, in free fall the pointer indicates 0 N.  You only need to drop it from few m as the slow mo vid of an iphone (120 fps) picks it all up quite nicely.  The iphone is great for these type of demos. 

Jim 

isn't that what I just said?  = "Let go, in free fall the pointer indicates 0 N." I didn't specify a specific height

yes provided you drop it from a height and measure the spring extension via video  as it falls, doesn't work if its hanging

30 minutes ago, saac said:

Yes there is, Newtonian at least. The water is a viscous liquid, a Newtonian liquid indeed. As the bottle falls (follows a straight path (geodesic) through the curvature of spacetime) the currents in the water will experience and exert viscous shear forces. Impart a spin on the bottle before you let go and these shear forces will present a delightful vortex in the water. Now how about we replace the water with supercooled liquid Helium! 

Jim 

Jim 

or you could just use an accelerometer or your mobile phone 😉 

2 minutes ago, andrew s said:

As far as I understand it all interpretations make the same predictions so there is no scientific way to choose.  It is a matter of philosophy not science. 

Regards Andrew 

true, take your pick but the nice thing about many worlds is that there is a phone app for it 😉 

16 minutes ago, vlaiv said:

It is really mind boggling that we still don't have any conclusion regarding that or accepted interpretation of QM

Thats the issue with uni physics, they teach the maths but not "Foundations of QM' - I used to believe in Copenhagen but now switched to Many Worlds, you know it makes sense 😉 

26 minutes ago, saac said:

Hang on don't go dissing Newtonian dynamics here     Can you tell I am a fan boi - stands up and mutters to the group  "I'm Jim and I'm an engineer.  It's been 32 days since picked up a slide rule " 

We came a long way on the back of Newtonian mechanics - heavier than air flight, split the atom, left the planet, built CERN and found more quantum stuff, put JWST in space to see the beginning.   Not so bad for "special cases" - we inhabit that realm.  Let's hear it for Newton.   

Jim 

Is there a Newtonian gravitational force on the bottle & water or is it weightless in free fall ? 

52 minutes ago, saac said:

Our principal theories do seem to attract tall poppy syndrome style critiques.  I think that comes from a fundamental misunderstanding and a lot of misconceptions popularised by pop science. I've never applied GR in anger (would not know how),

Admittedly challenging but you can do a few 'simple' mathematical examples (below) - there are 3 simplified problems at the end

Plus if you understand Python there are a couple of libraries on GR https://docs.einsteinpy.org/en/stable/examples/Symbolically Understanding Christoffel Symbol and Riemann Curvature Tensor using EinsteinPy.html#

Admittedly you need to get your head around relativity concepts and tensors first  which may take several months if you are doing self study (you need proper GR books and read the boring small print about Einstein Summation Convention first 😉 ). I knew maths up to BSc level geodesics but GR is perfectly doable once you realise what you were taught about orthogonal unit vectors at degree level was a simplification and get Newtonian analogies out of your head (I found the forgetting Newtonian gravity ideas the hard part)

Sean Carroll's video's don't shy from maths as he derives Einstein's equations but he gives excellent explanations of the reasoning behind them and the limitations

Pop books while good for generating interest  can equally confuse, but SC's pop GR book is good and a mix of maths starting from Pythagoras to the Riemann tensor  akin to the following video simplified, but he also writes one of the standard text books on the subject if you prefer more maths 

OK less biased, unlike humans it wont say I've spent $50m working on project X and devoted my life to it so I'm going to push model X regardless of whatever evidence is presented that model Y or Z is better.

7 hours ago, saac said:

I gave up on the video half way through, found it a bit annoying as he took too many detours - get to the point for crying out loud. Anyway, I suspect that what the AI would have been used for here would be (as you say) analysing the collision data but specifically looking for patterns. The notion itself that the quark composition of the proton is not static  but fluctuates is an established theory,  not new and not something advanced by an AI programme.  I may well be wrong but I would imagine the use of the AI here is to help to process the massive amount of data to find evidence to support the theory. 

Jim 

The upshot was that there are many models about quark composition , each research team having their favourite based on personal bias. However the machine has no human bias so it compares the observation data with those predicted  by models over the sum of all models. Thus seemingly ruling out what was previously most favoured and suggesting alternative models to 3 sigma so far.

When I did my msc back in 91 my project was on AI machine vision as it was called then. In those days we had to run on transputers and hand code everything in C and assembler to get any speed. AI was just a label

Today as an IT architect I'm still doing interesting things with AI, ontologies, semantics, digital twins etc amongst other things...

There is a concept known as the semantic triangle aka Ogdens triangle that relates labels to concepts and phenomena, provided you agree on concept and phenomena you can give it whatever label you like , eg 'temporal octopus training' since there isn't a standard label that maps label to concept/phenomena   (we actually debated this at the ITU in Geneva several years back)

I think the whole AI debate is semantics, it is a back propagation convolution  which I have no issue calling AI, the architecture is here 

https://docs.nnpdf.science/n3fit/methodology.html#neural-network-architecture

code is opensource

https://nnpdf.mi.infn.it/nnpdf-open-source-code/

Paper here

https://arxiv.org/pdf/2109.02671.pdf

Interesting use of AI, wonder how many of our other assumptions are 'wrong'?

Provided you can afford it, better to find the big problems early on than later,  last thing you want are intermittent faults later on

Are black holes watching you?

https://www.quantamagazine.org/black-holes-will-destroy-all-quantum-states-researchers-argue-20230307/

In this “participatory universe,” as Wheeler called it, the cosmos expanded and cooled around the U, forming structures and eventually creating observers, like humans and measuring apparatus. By looking back to the early universe, these observers somehow made it real.

“He would say things like ‘No phenomenon is a true phenomenon until it’s an observed phenomenon,’” said Robert M. Wald, a theoretical physicist at the University of Chicago who was Wheeler’s doctoral student at the time.

Wheeler is one of the experts who wrote the bible on General Relativity