Earlier quoted context omitted.
Here's a possible explanation that I'd seen somewhere. Up until very recently, humans had had weak ability to think, especially abstract thoughts, and the phrase common today "just think about it", would be meaningless just a few centuries ago. Perhaps the concept of depth in those times would be similar in complexity to 4-dimensional structures today.
That's completely wrong. Humans were just as smart 3000 years ago as they were today. The difference between today and back then is that people were much poorer and didnt receive an education. Their jobs were farming which didnt require things we consider essential like reading or writing which meant they stay unchallenged for their entire life. When you look at the rich elite or rich cities in the past then you see…
Einstein's description of gravity just got much harder to beat
31–40 of 78 posts
Re: Einstein's description of gravity just got much harder to beat
#32Can some knowledgable person articulate why physicists are so sure that QM and GR are incompatible?
"On spacetimes that are not time orientable we construct a U(1) bundle [model of a particle as an asymptotically flat spacetime manifold with a region of non trivial topology where time is not orientable] to measure the twisting of the time axis. This single assumption, and simple construction, gives rise to Maxwell’s equations of electromagnetism, the Lorentz force law and the Einstein-Maxwell equations for electromagnetism coupled to General relativity. The derivations follow the Kaluza Klein theory, but with the constraints required for connections on a U(1) bundle rather than five spacetime dimensions. The non time orientability is seen to justify and constrain Kaluza Klein theories exactly as required to unify gravitation with electromagnetism. Unlike any other schemes, apparent net electric charges arise naturally because the direction of the electric field reverses along a time reversing path."
"Deriving the U(1) bundle as a measure of the twisting of the time axis is new, as is the application to manifolds that are not time orientable. Like Kaluza Klein theory, it is purely classical, but free of the complications and ad hoc assumptions required by full 5D Kaluza Klein theories. It is remarkable how so much is derived from such a simple construction without additional assumptions."
"The connection with quantum theory is intriguing. Classical structures that are not time orientable have close links with quantum phenomena such as the logical structure [4], particle creation and annihilation [14] and spin half [7] The derivation of Maxwell’s equations and electric charge is just another result from the same premise of non time orientability."
Electric charges are a natural feature of the model, but quantisation only appears naturally for magnetic monopoles (which arise in pairs). However, adding elements of quantum theory to the monopole structures leads to quantisation of electric charge. The simplest such argument uses quantisation of angular momentum, but the argument fails when more than one monopole is introduced. The other approach uses a wavefunction for a charged particle [1, p262]. Uniqueness of the phase of the wavefunction leads to quantisation of charge. This is a tantalising link between the complex phase of the wavefunction and the orientability of spacetime."
[0] https://warwick.ac.uk/fac/sci/physics/staff/academic/mhadley...
Re: Einstein's description of gravity just got much harder to beat
#33> Despite its successes, Einstein's robust theory remains mathematically irreconcilable with quantum mechanics, the scientific understanding of the subatomic world. Testing general relativity is important because the ultimate theory of the universe must encompass both gravity and quantum mechanics. Maybe the universe just has a giant if statement.
Why must the ultimate theory of the universe encompass both? Do we know that there is an ultimate theory of the universe? Could GR and QM be wholly separate with no unifying connection?
What does this mean? Is it mean that Universe have insufficient rules, so there are phenomena which do not follow any rules? Is it possible to devise an experiment whose results would be totally fundamentally irreproducible?
Or you mean that Universe has strict rules, but human's ways to write these rules are flawed and insufficient to grasp in a full a fractal nature of mythical rules of Universe?
Re: Einstein's description of gravity just got much harder to beat
#34Earlier quoted context omitted.
could you give more on that ? i can imagine how religious dogmas can influence a lot of things, but representation of depth ??
Not OP, though mild experience with art history and Christian history, but I suspect OP is talking about the intersection of art and the prevailing religion in Europe at the time (Christianity). Early Christian art was intentionally unrealistic in style specifically because the intent was often symbolism and representation rather than realism (this still holds true today for most Orthodox Christian art[0]). In fact,…
You can see the intent on many religious sculptures in medieval churches around e.g France: the technique is precise, so it’d be really easy for a sculptor to just compare and match to a living and breathing model, therefore they chose not to. Contemplating how churches tell stories through imagery, you can see how they used this style for emphasis on specific physical features to elicit strong emotional response instead, not entirely unlike those TVs in stores cranking up contrast to completely unrealistic levels.
Re: Einstein's description of gravity just got much harder to beat
#35During brainstorming sessions, I often think about why/how medieval artists couldn't quite grasp how to depict depth in their paintings (as a lateral thinking technique). Being humans living in the world, they obviously experienced and understood that depth existed all around them, but had a hard time grasping the concept as a whole. I feel like we're kind of in a "medieval depth" phase of gravity/spacetime understan…
Mimicking reality is rarely the goal that art is optimized for. It's mostly converging to local optimum of one of the current fads.
Re: Einstein's description of gravity just got much harder to beat
#36Earlier quoted context omitted.
Rather it is the belief that they fundamentally must be compatible that is driving this research. Currently we don't know how to answer questions like "what is the gravitational field around a photon?".
Photons have zero mass so we know them to produce zero gravity, no?
Re: Einstein's description of gravity just got much harder to beat
#37Can some knowledgable person articulate why physicists are so sure that QM and GR are incompatible?
The exactly opposite idea of adjusting QM to directly work in geometry of strongly curved space-time is not pursued much. Not sure why. Maybe because it's hard. Maybe because it would just be an extension of business as usual which isn't attractive. Maybe for some other reason.
Re: Einstein's description of gravity just got much harder to beat
#38Earlier quoted context omitted.
Rather it is the belief that they fundamentally must be compatible that is driving this research. Currently we don't know how to answer questions like "what is the gravitational field around a photon?".
Photons have zero mass so we know them to produce zero gravity, no?
Re: Einstein's description of gravity just got much harder to beat
#39Earlier quoted context omitted.
Rather it is the belief that they fundamentally must be compatible that is driving this research. Currently we don't know how to answer questions like "what is the gravitational field around a photon?".
Photons have zero mass so we know them to produce zero gravity, no?
Re: Einstein's description of gravity just got much harder to beat
#40Earlier quoted context omitted.
Rather it is the belief that they fundamentally must be compatible that is driving this research. Currently we don't know how to answer questions like "what is the gravitational field around a photon?".
Photons have zero mass so we know them to produce zero gravity, no?