Mordred

Lol sorry I find what you described above even more restrictive on likelyhood. No of course you think restrictive likelyhood isn't an issue. I however feel it does apply and should always be considered. That's one of the reasons I rarely ever join threads involving aliens and UFOs the defenders of UFOs and Aliens always tend to ignore the odds against any likelihood. They also tend to come up with highly imaginative means of justification. I provided a few ideas on plausible means of travel and applied a bit of realistic physics. Take that as you will they are factors regardless of conjecture or opinion.

Absolutely agree on that lol

Yeah good luck with that. The point being simply achieving such a technological advanced state wouldn't be common place event. Hence it's restrictive on likelihood..... The other point being is that in order for one to justify alien visitation has huge restrictions on likelyhood. Yeah great possible sure.. what's the likelyhood of any system near enough to potentially matter ? Doesn't really work to justify that as actually occurring to justify our UFO sitings...

Sure but have you ever noticed is that those requirements are incredibly restrictive on any likelihood of existing in the first place ? Particularly when you start factoring in let's say age of stellar solar systems vs likelihood of achieving sufficient technological development for the scenario you just described. One of many

How about simple practicality ? It makes absolutely no sense to have to wait a century or more get information returned. You are well aware of time dilation for a craft in regards to the at home time frame compared to flight time. You cannot randomly ignore involved factors. Great you can send signals back at c. Yeeha so what ? You still have to get to Earth and factor in the time differentials for time dilation. It would be more practical to build a solar system scale telescope and get data faster.

Really and is that particularly practical unless the aliens live on some nearby star system where it's close enough we could detect chemical and biological signatures via spectography or recieve their signals ? Not very practical in my opinion. Your still looking at years for signals. Yeah that would certainly require some new physics lol. However unlikely still has some plausibility.

Do you want any information resulting from any studies to return to home planet ? It doesn't matter if the occupants are biological or not in that regard. What would be the point of any visitation if you cannot return with any data or resources

If you want turnaround to home planet in any reasonable time frame it's unavoidable even then its too slow for cosmological distances

Muc Much like that. It's a feasible possibility one could gather resources as they go but it would have to be of sufficient size for any manufacturing of those resources. As well as population growth. One could use the Oort cloud to hide in as their are lots of objects in the Oort cloud that escapes detection.

If we're sticking to known physics a feasible possibility being the Alcubierre drive it's feasible if one can solve the solutions for reduced energy requirements and eliminate any need for negative mass. Theoretically this would address the collision scenario as the spacetime bubble would cause deflection. However it also in turn generates a greater problem that the bubble may also cause gamma ray production. One study I'm familiar with showed that even at 50 percent c. That gamma ray production could wipe out life on the planet it's leaving and arriving at. However I've only ever come across the one paper on it. Other than that I can't think of any viable means that isn't a 1 way trip. Which really negates curious visitations. Colonization would be far more likely than visitation in a 1 way trip scenario. Though one other possibility is some species that lives strictly in space however that would require am extremely large craft with a huge infrastructure for resource production

That understanding is correct. The elephant your missing is that their are two categories (primarily) for cosmic rays. Primary and secondary. Primary cosmic rays are those sent from stellar objects like the Sun Secondary cosmic rays are those particles produced by the Primary rays interactions with our atmosphere. Neutrons are part of the secondary group. Part of that process includes mesons decays to that further allows leptons to form. Here is an examination of some of the different processes at different atmospheric levels https://pdg.lbl.gov/2019/reviews/rpp2019-rev-cosmic-rays.pdf

Cyclic universe models is one possible cause for our universe coming into existence. It does nothing to address how the first universe developed but for this thread your not concerned about that. This however doesn't really follow. The conditions of the BB according to mainstream physics was in a thermal equilibrium state. The extreme high temperature wouldn't even allow atoms to form. The four forces were in a state of thermal equilibrium. Once electroweak symmetry breaking occurs the 4 fources could separate. Gravity Em, weak and strong force. Particles could then drop out of thermal equilibrium. That's simply one process where it would be impossible for past information ideas etc would be literally obliterated even assuming such things could even survive the initial collapse of the previous universe.

That would be a causality violation c is the speed limit of information exchange as well.

found it I finally recalled it was a series of Black star research "Irreversible gravitational collapse: black stars or black holes?" https://arxiv.org/abs/1105.3394 I certainly wouldn't argue with this. LOL I know any personal modelling I do I set Planck units as a constraint on anything involving spacetime or other fields. Funny thing is that boundary works well with the FLRW metric for the 10^{-43} second boundary the average estimated temp of 10^19 GeV when you convert is in the same orders of magnitude as Planck temperature. With the temperature scale factor relation. Blackbody temp can be estimated by the inverse of the scale factor. This also corresponds to 1 Planck length. just an interesting tidbit on last.

It was several peer reviewed article on Arxiv but it was a few years ago that I followed the research and some of the proposed tests. However I'll take a look and if I can find the papers. If I can I'll post it. Point of detail the singularity conditions regarding the EH involve infinite redshifts and subsequent time dilation relations involving the EH. These conditions are the ones directly involved with regards to Hawking radiation. This also involves Unruh radiation https://arxiv.org/abs/0710.5373

so you googled a bunch of answers so tell me google what happened to the mass of the collapsing star then.... can you answer that or did it simply disappear. That is directed at google not you lol . Would you like to see equations that directly relate to the density term in regards to the collapsing star? https://arxiv.org/pdf/2310.17647 see section 4 If Victor Toth stated that then he only looked at the vacuum solutions of the interior and ignored the coordinate assigned for the singularity R=0. Not surprising though most articles tend to ignore that part as no one feels the singularity condition should exist. I have another related article that suggests that the BH may simply be a neutron star that has collapsed just beyond its EH but is still present. As mentioned no one knows beyond the EH. So its really anyone's game until we can find a means of indirect evidence to give us more clues. Gravity waves is a viable possibility others are mentioned here. The article that has some suggestive tests via the accretion disk is here https://arxiv.org/pdf/1104.5499 there is also a section covering Hawking radiation. However one will be quite surprised at all the processes matter undergoes in that accretion disk. I recall years ago I asked my instructor " How can you possibly have infinite density or near infinite density" his answer was that although fermions cannot share the same space with the same state that restriction does not apply to bosons. " you can in fact have extremely high density and still be a vacuum solution with incredibly high temperature and density. Vacuum describes a pressure term. Its not the energy density. You get the energy density by the equations of state for the particles contained within a region. Its one thing that often confuses ppl concerning vacuum. It can be positive or negative and can describe any range of energy density. If you think about that you might consider that a star is simply a condensed matter field it can be equally treated as a field. We know in cosmology we get a similar phenomena due to the BB and its mass density terms. I didnt have time to properly respond to the quoted section earlier as I was at work. Having time now I can provide a better response. just to add the singularity at r=0 is a true singularity it cannot be removed by a change in metric choice. The event horizon itself is often described as a singularity condition however that is a coordinate singularity and not a true singularity. https://en.wikipedia.org/wiki/Kerr_metric "Rotating black holes have surfaces where the metric seems to have apparent singularities; the size and shape of these surfaces depends on the black hole's mass and angular momentum. The outer surface encloses the ergosphere and has a shape similar to a flattened sphere. The inner surface marks the event horizon; objects passing into the interior of this horizon can never again communicate with the world outside that horizon. However, neither surface is a true singularity, since their apparent singularity can be eliminated in a different coordinate system. A similar situation obtains when considering the Schwarzschild metric which also appears to result in a singularity at 𝑟=𝑟s dividing the space above and below rs into two disconnected patches; using a different coordinate transformation one can then relate the extended external patch to the inner patch (see Schwarzschild metric § Singularities and black holes) – such a coordinate transformation eliminates the apparent singularity where the inner and outer surfaces meet. Objects between these two surfaces must co-rotate with the rotating black hole, as noted above; this feature can in principle be used to extract energy from a rotating black hole, up to its invariant mass energy, Mc2." I suspect this is what Victor Toth was referring to hope that helps Mathius Balu has an excellent coverage of this http://www.blau.itp.unibe.ch/newlecturesGR.pdf He will use the BH to help explain: "artifacts of coordinate choice" I would have to dig through it though to relocate the relevant section lol and just to add flames to the proverbial fire. A rotating BH has more than one event horizon..... google is useful but unless your aware of other factors getting good answers can often mislead down the wrong google pathway. For example simply googling BH singularity will more likely than not describe the coordinate singularities regarding the EH rather than the R=0 singularity condition. This wiki has the relevant detail regarding the Gravitational singularity as the link describes it The case r = 0 is different, however. If one asks that the solution be valid for all r one runs into a true physical singularity, or gravitational singularity, at the origin. To see that this is a true singularity one must look at quantities that are independent of the choice of coordinates. One such important quantity is the Kretschmann invariant, which is given by 𝑅𝛼𝛽𝛾𝛿𝑅𝛼𝛽𝛾𝛿=12𝑟s2𝑟6=48𝐺2𝑀2𝑐4𝑟6. At r = 0 the curvature becomes infinite, indicating the presence of a singularity. At this point the metric cannot be extended in a smooth manner (the Kretschmann invariant involves second derivatives of the metric), spacetime itself is then no longer well-defined. Furthermore, Sbierski[21] showed the metric cannot be extended even in a continuous manner. For a long time it was thought that such a solution was non-physical. However, a greater understanding of general relativity led to the realization that such singularities were a generic feature of the theory and not just an exotic special case https://en.wikipedia.org/wiki/Schwarzschild_metric#Singularities_and_black_holes

How particles scatter, or form new particles etc etc always depends on their cross sections . That uses the Breit Wigner equations along with the Feymann golden rules. It not some case of a photon knowing anything. When it encounters another particle the cross sections and Feymann golden rules are used to determine the end results. Granted we also have a table that is helpful . https://en.m.wikipedia.org/wiki/Table_of_Clebsch–Gordan_coefficients

Not quite destructive interference you can have full annihilation if the two wavefunctions are equal but opposite its realistically no different between matter and antimatter colliding with its opposite. Think of all particles are field excitations under QFT. You can get full annihilation with matter why would photons as a boson be different the antiparticle is asymmetric to the photon. Keep in mind that doesn't apply to probability wavefunctions. You have to look at the creation/annihilation operators specifically for each using QFT. Course you could further consider baryogensesis and leptogenesis which we cannot explain as that also relates.

Correct its best to think of singularity as a point where the math used breaks down.

Vacuum can have an energy density ta da lol. That energy density can easily approach infinity keep in mind my original statement had "as close as possible " that allows a QM interpretation on Planck units for cutoff though Gravity has no effective UV cutoff for the mass term. That's a large part of why gravity isn't renormalizable. The IR cutoff is already established. For the record I've had numerous discussions with some mistakes he has made in other articles of his. Sometimes I'm correct other times he is just didn't explain something accurately enough with regards to Victor Toth. Cool character though he's friendly and easily talked to.

How so no one knows what goes o beyond the EH however the equations do lead to the infinite density singularity which everyone agrees is the issue regarding the singularity condition.

So inertial observers. By the way here's how to do the kissing number problem in four dimensions if your interested. THE KISSING NUMBER IN FOUR DIMENSIONS Oleg R. Musin "In three dimensions the problem was finally solved only in 1953 by Sch¨utte and van der Waerden. In this paper we present a solution of a long-standing problem about the kissing number in four dimensions. Namely, the equality k(4) = 24 is proved. The proof is based on a modification of Delsarte’s method." https://arxiv.org/pdf/math/0309430 you wish to use vectors well you have those relations here. Its rather detailed. as you linked Newton and the kissing number above thought you might find it handy with regards to your spheres

great so I employ full GR for an observer in each case which will get different answers ? Observers affect geometry. length contraction is part of SR. An observer moving at 90 % c won't see a circle. with the equivalence principle inertia has equivalence to gravity with regards to observer effects. Pythagorus theorem doesn't even work without conversions to restore Pythagorus theorem. So your triangles wouldn't work correctly. You do want your equation to be useful in some cosmology based measurements if the answer is yes then you will need to account for geometry changes. Your going to need to include the effects of curvature and observers in those coordinate changes.

precisely my point " its relative to the Observer. How do you define one observer from another ? How is it relative ? If I have an observer a coordinate \(c_1,x_1,y_1,z_1\) living in a gravity well. What effect does it have from an observer moving a 0.99 c etc etc. You have no means of describing one observer from any other observer. How do I know if you are using strictly Galilean relativity or Special relativity ? am I suppose to read your mind ?

gravitons are still a viable possibility you don't need them to describe a BH or the effects of Hawking radiation on a BH but its also not incorrect to do so. here is the thing about Hawking radiation a virtual particle pair must form outside the event horizon. Due to conservation laws all particles pop into existence as particle pairs primarily but not restricted to conservation of charge. (matter , antimatter for example) which Hawking radiation uses. the matter particle escapes to infinity while the antimatter particle falls in. Its a rather simplistic descriptive but the mass loss is due to being the anti particle of the pair. A photon is its own antiparticle. The difference between them isn't charge but rather its polarity. As a wave it obeys constructive and destructive interference. So anti-photons will annihilate with matter photons. Now this may or may not cause interference with other particles as all particles also have wave and particle like characteristics. However that is moot as the only thing needed is the antiparticle of the pair formed to fall into the BH regardless of what particle is involved. you would get a reduced mass through mass energy equivalence regardless if it is anti photons or some other particle type. As far s I know Hawking never did specify which particle was involved. His original paper simply had particle antiparticle pairs. As photons are generally used with blackbody radiation its the most common treatment. However you also have methods using entropy but entropy in particle physics related to effective degrees of freedom ie spin. charge , flavor, color, energy momentum etc. for example see here "Then Hawking’s black hole emission calculation [9, 10] for free fields gives the expected number of particles of the jth species with charge qj emitted in a wave mode labeled by frequency or energy ω, spheroidal harmonic l, axial quantum number or angular momentum m, and polarization or helicity p as Njωlmp = Γjωlmp{exp[2πκ−1 (ω − mΩ − qjΦ)] ∓ 1} −1 . (5) Here the upper sign (minus above) is for bosons, and the lower sign (plus above) is for fermions, and Γjωlmp is the absorption probability for an incoming wave of the mode being considered." https://arxiv.org/pdf/hep-th/0409024