Leaderboard

To expand on what I said earlier: some of these explanations are leaning a bit too hard on classical physics in quantum situations. What they are doing is trying to use a classical analogue, that a body in a circular orbit has a KE that is half the magnitude of the PE, so for an orbit close to the nucleus (i.e. using the Bohr theory, which we know isn't correct) an electron in hydrogen, which has an ionization energy of 13.6 eV, has a KE of 13.6 eV and a potential energy of -27.2 eV. Those numbers aren't actually true in the QM solution, but those are the most probable values. The improper extrapolation is to assign 1/2 mv^2 to the KE, since you can't assign a velocity to the electron. When you get to an atom with a large Z, some electrons have a high enough average KE that relativistic corrections are necessary. The incorrect explanation is to say you are correcting the speed, but this doesn't show up anywhere in the equations. You solve the relativistic version of the wave equation, which gives different results than the non-relativistic version (Schrödinger equation) so there is a difference in the energy eigenstates. A relativistic correction of energy, without ever invoking velocity. I recall some years ago reading a pop-sci article on this and they linked to the paper it was based on. The pop-sci article talked about the relativistic correction of the speed, and saying that the mass of the electron increased. When I read the journal paper, none of that was mentioned. It was only the energy that was corrected, as one might expect of a rigorous paper. The pop-sci article had tried to use this classical explanation to make the effect make sense, but it made for incorrect physics.

To put it in layman's terms this is my understanding: Newton (Newtonian gravity) - gravity is a force that causes objects of mass to attract each other. Einstein (General relativity) - gravity is not a force but the curvature of space time caused by the presence of mass (also energy but lets keep it simple in this context) where objects follow this curvature resulting the appearance of attraction. Quantum Mechanics (Quantum gravity) - gravity is a force/field where gravitons are exchanged between masses resulting in interaction causing mutual attraction. The Newtonian model works very well for general predictions and suitable for most applications. The GR gravity model has been confirmed to produce more accurate predictions than the Newtonian gravity model, therefore supersedes as the best model of gravity we have. The GR gravity model predicts absurd results when used at the quantum level, predicting things like singularities... The quantum gravity models (hypothesis) solve this issue, however do not (as yet) consolidate with GR which has been verified as the best model of gravity we have. Maybe we are looking at this from the wrong perspective? Maybe focussing on "what gravity is" is not the answer to solving this dilemma. I think learning the nature of "what space-time is" will reveal what gravity is. Please jump in and correct my understanding! this subject is one that is most intriguing to me, and one I want to learn much more about.

Re-reading myself I realise I didn't explain at least a couple of technical terms, so I'm sorry. Horizons: Surfaces in space-time that separate regions of space-time that are inaccessible to observers on one side of those surfaces Renormalization: Treatment of a physical problem taking into account how it depends on the scale at which you study it Entropy: A variable that measures lost information; physical information that gets scrambled Gravity is peculiar on all of these accounts. Other 'forces' don't have horizons associated with them. They're not scale-dependent, like gravity is. This is the meaning of 'bad-behaved'. Other forces don't have an "intrinsic" entropy. Gravity is not so much a weak force as it is a scale-dependent force. That is, whether it's weak or strong depends a lot on the scale at which you look at it. It's actually the dominant force at scales that approach a Planck's length worth of distance. At stellar distances gravity becomes relevant again, but not because of scale-dependence. Rather, because gravity cannot be screened. Gravity also has a cosmologically-relevant component, which is the vacuum energy. Gravity is peculiar in many senses. So, whatever a force is --I'm with other users here that whether it really is this or that verges on metaphysical--, gravity is very different to the other bunch. It's the odd one out. I really hope that was helpful, but it's a difficult topic. Other users express themselves more eloquently than me. And welcome to the forums.

I have heard recognized physicists stating "Nothing can come from nothing" and if this is accepted as a postulate applying basic logic follows: As something do exist now (for instance we exist) it can be deduced that: _ The absolute nothing never existed. (If it it would have existed before nothing would have come up.) _ Something always has existed. Am I wrong in something? I think this is important in the tries to explain the origins of the Universe. The Universe didn't come from nothing then, it came from something. Something that could have always existed before. Not so easy to grasp may be but seems right... And if the above is right, must we assume that Space and Time are things that just always existed? Seems so...

Same here, shooting from the hip that is.... I like Professor Lawrence Krauss' educated speculation. Perhaps the quantum foam from which the universe/space/time [as we know them] arose, needs to be redefined as nothing. Perhaps that's as close [to the perceived nothing most of us envisage] that can ever be...it effectively maybe nothing. I see that has far more likley and reasonable then some dynamic, all knowing omnipotent spiritual being. Afterall, didn't we also see at one time "space" as nothing?

I have invited Dr. Don Lincoln, physicist and well-known science author, who works at FermiLab, and who was quoted in this thread here.... ....to join this discussion. If he declines, I will let you all know, so as not to leave you hanging. Mr. Jones suggested I'm a name dropper - I can only add that I have carefully not mentioned my long-ago acquaintance with Isaac Asimov, which I humbly offer as evidence to the contrary.

Something with a certain behavior which we call the top quark was discovered. Generally, discussions about this do not split hairs about whether or not we are searching for reality, though there are some good discussions on the bad habit of reifying these things in physics. Mermin's "What's Bad About This Habit?" is a prominent one. Later on he quotes Bohr

Instead of taking a drug based on a single study, I would think a better option is to get a vaccine that has been fully approved by the FDA. Seems a no brainer to me. That reminds me, it is time to worm my horses...

Seems you have a quibble with one report of one reading of one temperature on one day in one place. So.... How does this change/affect/determine climate change ?

So, have to ask, is string theory physics? Or, because we don't know to what degree it might describe the real world, is it a theoretical framework that lies on the borderlands of metaphysics? String theory seems to describe a landscape of possible universes, most of which intelligent life can never behold. At least, with Davy's long-fingered lemurs, we can go to Madagascar and look at quite a few of them. (careful, they will steal your glasses)

Yes you understand that physics correctly, but things are a bit weirder than you have presented since what you have said is incomplete. Let us call the Earth E, the Traveller T and the Star S. So there is a relative speed between T and S of 0.8c. Which means that they are not in the same frame. So we must convert the 3Ly separation to one frame or the other the T frame or the S frame, it does not matter which. This will give us the 'proper distance' between T and S. The proper distance Lo is always longer than the measured distance between moving objects and is the same in all frames. So we use the formula [math]L = {L_0}\sqrt {1 - \frac{{{v^2}}}{{{c^2}}}} [/math] Substituting the given data [math]3 = {L_0}\sqrt {1 - \frac{{{{\left( {0.8c} \right)}^2}}}{{{c^2}}}} = {L_0}\sqrt {1 - 0.64} = {L_0}\sqrt {0.36} = 0.6{L_0}[/math] [math]{L_0} = \frac{3}{{0.6}} = 5[/math] light-years This is what I mean by your original statement was incomplete. (no criticism intended I am being detailed in order to help) Because you originally stated that S is 5 Ly from Earth. Since this is the 'proper distance' it must already be corrected for any motion between E and S, which you have omitted to say. It is possible, though not generally the case, the S will not be also moving relative to E. Just to add that when you start to combine the effects of two relative velocities the calculation becomes more involved. You can't simply add them up. Note here that it does not matter whether T is travelling towards S or away from it, but T must just be passing E when the measurement is made.

I'm assuming flat spacetime (no mass, SR only), and inertial motion unless specified. Generally yes. Also "when are you talking about?" matters and is more complicated than a Newtonian description. The positions of things on a map are coordinates within a coordinate system, and those are different for different observers. You could have a map where the Milky Way is at a fixed location and Andromeda is moving, or one where Andromeda is fixed and the Milky Way is moving. Those correspond to the coordinate systems of 2 observers at rest in the respective galaxies. Yes, the distance to the star is different in the different frames of reference. There are invariant measures of distance, eg. the "proper length" of a 1 m stick at rest is always 1 m and everyone will agree on that, even if the stick is moving relative to some observer and is length-contracted ie. has a coordinate length less than a meter in that observer's coordinates. We can say that. We can measure the distances to both galaxies using one frame of reference (eg. the one in which we're at rest), and you can measure the motion of objects using the coordinates of that frame. Consider the map analogy. The spatial coordinates can be represented by a grid drawn on the map. The same grid coordinates can be shown by putting a lattice of rulers throughout space. In our own frame of reference, our rulers are not moving and so they don't length-contract. An object light years away can wobble at speeds near c, but yet stay near one place in the grid of rulers. Meanwhile, that distant wobbling object is moving relative to our lattice of rulers, and our rulers do length-contract, in its frame of reference. For simplicity consider two different inertial frames of reference F1 and F2 that the wobbling object switches between. Each of those frames has its own set of rulers making up a lattice throughout space, each at rest and not length-contracted in its own rest frame. Say I'm at 1 LY from Earth, as measured by Earth, and I'm wobbling relative to Earth. I stay near the 1 LY mark on Earth's set of rulers, but those rulers are contracted by different amounts in F1 vs F2. For example, in F1 Earth might be 0.8 LY away from me and the 1 LY mark, and only 0.6 LY away in F2's frame. The reason that the distance as measured by Earth isn't changing much, and the distance measured by me is changing drastically, is that I'm switching between different frames of reference. The distance between Earth and the 1 LY mark, which has a proper distance of 1 LY, is length-contracted by different amounts to different observers, depending on their relative speed.

It seems you and I don't use the same definition of intelligence... Chance, chaos, they don't exist? I really am unsure why or how you get these ideas. I don't think these ideas hold up to scrutiniy, but I also realise that this is the extent to which you answer, so it might not be a very fruitful discussion. Things like 'be absurd' are... well your opinion. You like to state the way things are, but don't provide evidence or even follow sound logic that makes sure there are no other possibilities. It might be a good idea to focus on explaining your concepts in more steps, explain why things are like this and not in other ways. Thus far you did not seem to answer my question, or those of other people. I asked "Why does intelligence have to have always existed, what evidence is there for this. What evidence can you provide that goes agains the claim 'intelligence has not always existed' or 'there was no intelligence on Earth before life'. " One can only find several extra statements from which to understand that your definition of intelligence is different from that of other peoples. It might be good to give a proper definition of the words you use. Are they different from what some dictionaries propose, if so, you should note this down so we can understand.

Reading online seems like chosen to harmonize for safety purposes and that those particular colors were selected due to color blindness concerns. Could still do it of course. Think UK plugs are already unique with the fuses so may not be that big a deal in terms of cost/Market size.

Why does intelligence have to have always existed, what evidence is there for this. What evidence can you provide that goes agains the claim 'intelligence has not always existed' or 'there was no intelligence on Earth before life'. You keep repeating that your logic is simple, but for those reading this thread it is not, and it seems quite flawed. People in this thread have asked you to clarify things, but you seem to not entirely engage with their arguments. It might be a good idea to go back into the thread and from page 1 check which definitions have not been given, or which comments you have not fully engaged with yet. This will help both the discussion and the will of other people to participate! Good luck

Would it help if we thhrew out the concept of a 'force' in this context, and said that there are four fundamental interactions ? We don't know the exact nature of these nteactions, but we have various ways of modelling them. None of the models tell us what they are, but they make good predictions where they are applicable.

True, but it's not unreasonable to ask. How unsatisfactory would it be to a end a discussion about whether, or at what age, abortion should be legal, or the legal status of various drugs with 'whatever a court says'. AGI is irrelevant to this particular discussion. DABUS is far from AGI yet its legal personhood is still being discussed, and apparently granted, in some courts. With the development of narrow AI like AlphaFold, which vastly improves previous attempts to model protein folding with implications in drug discovery, these legal discussions will likely (and rightly in my opinion) become more frequent regardless of AGI development. Given the glacial speed of politics and law, starting the discussion before it becomes a pressing matter seems prudent. Regarding AGI, that blog was a bit vague. Here, about 350 ML researchers were surveyed regarding the estimated timeline of human level machine intelligence development. Granted, it might be something like fusion power (another 20 years right?), but it's the most thorough guess i've seen kicking around. I found it incredibly hard to find out anything about the actual architecture of this model. This is the closest i could find - short on detail. I very much doubt it's anywhere near GPT-3, AlphaFold or Tesla's self-driving architecture. Sounds more like a gimmick to start a discussion.

It’s not infinite, and the application might dictate the desired geometry.

It is a question of speed. The electrons in an ordinary vacuum tube are not moving fast enough to warrant more advanced mechanics such as relativistic dynamics. Sub atomic particles in particle accelerators, and natural particles cosmic rays in nature achieve speeds such that relativistic calculations need to be employed. For most normal interactions the electrons 'orbiting' the nucleus in atoms are not moving fast enough for relativistic calculations to be needed. So the Schrodinger theory of wave mechanics uses classical (newtonian) evaluations of the dynamics. There is a more advanced theory making relativistic corrections due to Dirac.

This is a very interesting question and much like you Davy-Jones the nature of what gravity is, rather than how it is modelled, is one that I often ponder. Interestingly in QM gravity is modelled as a force; "In theories of quantum gravity, the graviton is the hypothetical quantum of gravity, an elementary particle that mediates the force of gravitational interaction. There is no complete quantum field theory of gravitons due to an outstanding mathematical problem with renormalization in general relativity" So which is it, the curvature of space time or the exchange of particles between masses, or a field in which mass interacts?

No, it would be true for a finite universe as well.

There seems to be a presumtion in the last few posts that the solar system formed from the product of a single supernova explosion. This is not the case. Multiple supernovae would have contributed to the molecular cloud whose collapse led to the formation of the solar system. What is thought to be practical is to identify sister stars to the sun, from their spectroscopic signature. These would have formed as neigbours in the same cloud (compare with the Pleiades) then drifted apart. I don't recall whether such siblings have yet been idenitifed, but a literature search should turn up the answer. Here are a couple of papers on the subject: The evolution of the Sun's birth cluster and the search for the solar siblings with Gaia The authors "use self-consistent numerical simulations of the evolution and disruption of the Sun's birth cluster in the Milky Way potential to investigate the present-day phase-space distribution of the Sun's siblings." Searching for solar siblings among the HARPS data The authors note "At present, there are four plausible candidatesreported in the literature: HIP21158, HIP87382, HIP47399, and HIP92831. In this study weconduct a search for solar siblings amongthe HARPS high-resolution FGK dwarfs sample, which includes precise chemical abundances and kinematics for 1111 stars. Usinga new approach based on chemical abundance trends with condensation temperature, kinematics, and ages we found one (additional)potential solar sibling candidate: HIP97507."

..what is minimum velocity of dust from a supernova explosion? (i.e. which won't get back to it due to gravity and being sucked by the newly forming black hole)... ..what is maximum velocity of dust from a supernova explosion? (can it exceed escape velocity of the entire galaxy? analyze per galaxy size and mass).. In the case of Crab Nebula velocity measurements x time, can give the moment in which supernova exploded. According to Wikipedia it might be 1054 year A.D. https://en.wikipedia.org/wiki/SN_1054 Enjoy Betelgeuse until you have it! The same extrapolation can be done with any other supernova, or supernova-to-be. i.e. when (and in what quantity) remnants of Betelgeuse will reach Earth in the future (and any other close to the Solar System supernova-explosion-to-be) The same extrapolation can be done with the Solar System. I think the best is to write a computer simulation which calculates, estimates, predicts where and when it happened (or predicts where any other historical supernova was in the past billions of years ago). Where is remaining black hole after supernova explosion, which created the all heavier elements which you have here on the Earth, and in the Solar System?

+1. This is a very interesting re-focusing of the question. Maybe the OP is interested in it? I don't think it can be done with our solar system because AFAIK remains of supernova explosions are seen as halos of dust (e.g., Crab Nebula). I surmise that our Solar System is much older than the Crab Nebula...

..it would be a much more interesting discussion if you would stop a few words earlier.. It would be discussion about location of supernova explosion which gave birth to the all heavier elements in the Solar System..

Totally concur with @Janus & @Endy0816. I'd like to know who said that too, @Strange. (+1)3 Let me offer you a complementary picture of why everything running away from one point doesn't work. If everything in the universe were running away from one point, we would look at the night sky and see something very special at that point. That would be the point we're running away from. Instead, what we see is a series of spherical layers older and older in every direction the farther away from us we look. Until we hit the very feeble, very dilute image of a primeval plasma state of the universe (this is called the surface of last scattering). A picture of the universe when it was opaque to radiation, because all the particles were ionized (plasma) so it didn't let radiation through. That's a picture of a pretty early universe. And it appears more or less the same in every direction. So, where is the original point? I hope that helps.

A black hole Energy can’t be destroyed Works both ways