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! Moderator Note Rule 2.11 Solicitations requiring non-disclosure or confidentiality agreements, or insisting that discussions must take place privately, are not permitted. We are here to discuss science, in the open (and "I have an idea, can someone do the math for me" typically woefully underestimates the amount of effort this involves).

no coordinate choice affects the mass distribution. I could describe the universe in numerous different coordinate choices example Euclidean, spherical cylindrical etc without causing any difference. It is precisely why we use invariance. The mathematics is set up that way so that we do not have any coordinate choice dependency. you know full well GR fully describes time dilation the FLRW metric is a GR solution. We don't arbitrarily choose DM and DE as the full explanation those two terms are simply placeholders until we can determine the cause of each. We still can measure their effects through indirect evidence. I rarely give downvotes so its someone else. As far as sampling range is concerned, redshift is only one of many pieces of evidence of an expanding universe. In point of detail its not even close to the strongest evidence. Its the one most ppl are familiar with but the real evidence comes from our thermodynamic laws in regards to temperature and how it influences the SM model of particles via processes such as BB nucleosynthesis in regards to the CMB. One danger of trying to understand cosmology by rote instead of learning the math is that too often you get incorrect information. I will give an example if I looked up hydrogen and its temperature it could form with stability a google search will state 3000 kelvin. However if one knows how to use the Saha equations that would reveal that value equates to 75 % of the potential hydrogen. Hydrogen can start to form as low as 6000 kelvin=25% 4000 kelvin for 50 %. That is just one example. however knowing this one can study the metallicity of our universe evolution via hydrogen, lithium, deuterium etc. So I just described another piece of evidence for expansion. In other words were not restricted to redshift to determine if our universe is expanding

I don't know the maths at all. But it seems fundamental to me that if you make a choice, you instantiate something. When something is instanced, things are set and other settings are rejected. When you reject other settings, there are fundamental consequences. These consequences are the assumptions. If time coordinates are chosen such that earth-bound clocks are comoving with the cosmological medium, that has consequences. The very choosing of those coordinate forbids a non-relative (non-gravitational) time dilation effect. That is why FLRW metric forbids temporal redshift, because it was chosen to be orientated that way. Am I wrong? The observational evidence in this case is dubious solely because of the narrow range of observation relative to the field of study. We've never made an observation of cosmological redshift from outside of our solar solar system, let alone from a distance where space-expansion or temporal-expansion is significant. We've never made an observation of cosmological redshift from a time in the past or the future, where spatial or temporal expansion is significant. I'm not saying any of this is possible. I'm just saying our sample range of observations is far too narrow to be confident to say our evidence is significant. We've taken a handful of stones from a beach, and assumed all beaches must be stoney. As for where would we get time dilation? Where do we get space-expansion? Dark energy? We can make up anything to fit the narrative. Advantage for what purpose? Simplicity and accuracy to fit other observations are similarly limited in their scope? This again falls foul of confirmation bias. BTW, someone anonymous is downvoting all my threads. Not that I care about reputation, but being anonymous and not saying why I'm wrong feels like im being victimised and rather abusive.

Not sure me or Japan would agree. There is also the trichotomy of pain, suffering and harm to think about. So there is a question of whether or not the existence of nuclear weapons harms us, even if not currently causing us objective pain. Here is a thought experiment; There is a bank called the Gun to your head Bank. Inside the bank is a system of automatic turrets that only the bank manager can control. The policies are that if anyone tries to rob the bank, the manager will initiate the turrets and they will kill everyone in the bank. If a member of staff tries to quit or is otherwise being civilly disobedient, the manager will initiate the turrets. If a customer takes issue with the banks practice or believe the bank manager is stealing money from the account, the manager will initiate the turrets. You get the idea. This bank, is the world under the threat of nuclear weapons. Even if the manager says he is going to get rid of these extreme policies but keeps the turrets in place, the implication that they could be used thusly, anytime, still exists and you cannot guarentee that a new bank manager won't be even worse. So do I think people are banging their heads against the wall? No. Do I think we all have guns to our heads? Yes.

Sure. Whatever. I should have known we're not in Basel anymore. I dunno. Certainly not Nietzsche. When somebody doesn't have an argument, they usually trot out the H card, often apropos of nothing previously mentioned.

Yes I think you have got it. I admit I don’t know how this is presented to students in the US today. My experience with Imperial units dates from schooldays in the UK in the early 1970s, when we transitioned from Imperial to metric. I remember how awful it was, compared to the simplicity of metric, and specifically, the version of metric that later came to be known as Systeme International (SI) units.

No there is no assumptions due to coordinate choice. You already know time dilation is a consequence of spacetime curvature or Relativistic inertia. The math and observational evidence shows us that there is no curvature term k=0. So where would you get time dilation ? This has already previously been mentioned. As massless particles travel at c we can ignore the inertial gamma factor. A higher density past the answer either. To go into greater detail if you take 3 time slices say time now, time at the CMB say z=1100. And a slice at say universe age 7 billion years old. If you describe the geometry of each slice. Each slice has a uniform mass distribution so no slice has a non uniform mass distribution to have a curvature term. Hint this is the real advantage of the scale factor a. No time slice has any change in geometry or curvature it's simply volume change between slices and density changes as a result of the ideal gas laws . In point of detail we do not rely on redshift in cosmology it is too full of other influences such as gravitational redshift, transverse redshift, Integrated Sache-Wolfe effect, Doppler redshift. etc etc. We examine all pieces of possible evidence to confirm the accuracy of cosmological redshift. Nor do we use the generic formula everyone sees on google. https://en.wikipedia.org/wiki/Redshift this formula only works for nearby objects it loses accuracy as near as one MPC. The full formula includes the influence of the evolution history of matter, radiation and Lambda. details can be found here "Distance measures in cosmology" David W. Hogg https://arxiv.org/abs/astro-ph/9905116 side note the paper also applies to luminosity distance we also have a different formula for Luminosity distance than what one would google. \[H_O dl=(1+z)|\Omega_k|^{-1/2}sinn[\Omega_k^{1/2} \int^z_o\frac{d\acute{z}}{\sqrt{(1+\acute{z})^2\Omega_R+(1+\acute{z}\Omega_m-\acute{z})(2+\acute{z})\Omega_\Lambda}}]\]

I realized that the mistake I made was a technical one, and not related to the issue at hand. My assumption of using Newton's second law would only make sense if the pressure unit was in Pa or N/m^2. However, since the pressure value was given in lbf/in2, the value obtained by multiplying the area with P (in lbf/in2) is numerically equal to the mass value. The response was a bit unclear, but it should have been understandable. As you pointed out, the weight of one pound is equivalent to one lbf here on earth. Therefore, if they wanted to clarify this, they could have done a conversion using the conversion factor of 1. However, this conversion should be understood even if it is not explicitly mentioned.

You are muddling metric and old-fashioned Imperial units. g in old units is 32ft/sec squared. g is 9.8 m/sec squared in modern SI units. If you multiply lb by g in old units you get the force in something called poundals, defined as the force needed to give a 1lb mass an acceleration of 1ft/sec squared. So there are 32 poundals in 1 lb-force. A pressure given in units of lb/sq in is implicitly in units of lb-force, not lb mass. lb-force is a force unit already, so no need to multiply by g. It’s a nightmare. If you really want to do your head in, read this: https://en.wikipedia.org/wiki/Poundal

So by choosing such time coordinates, it also inherits the assumption that the cosmological medium of time is moving uniformly, everywhere and always (an Earth bound clock must tick at the same rate as the rest of the universe now and in the past and in the future). And yet, our observations are bounded to a infinitesimally small location of the universe (observations from our solar system compared to the size of the universe), and a very small period of time (150/13billion years). There is a problem here I cant quite put into words, so I will use bad analogies. Its like everyone being colour-blind and believing the universe is shades of grey. You can observe light wavelengths, but you cant observe the colour blue. It has no physical meaning. Its like believing gravity is a force before GR modelled spacetime curvature. Everything must fit what we observe (of course, to be empirically tested), but we don't acknowledge enough how severe our observations are restricted/limited. In many areas of science, where and when you perform an observation has no bearing on what is being tested. In THIS particular case of redshift, when and where you perform an observation is of paramount significance... and we are straight-jacketed into observations from our solar system location (where ever it is in the universe), and observations from our moment in time (a few hundred years). The limitations of our observations are significant relative to the field of study. But space-expansion IS a theory, as is the more absurd temporal-expansion. The premise for the theories is from choice of coordinates. Is this saying there is no transformation that will allow only time to expand and not space? What is the meaningful consequence of this?

Without looking at that link as the material needs to be posted here. The math done in that paper was done by your colleague correct ? By your statement above he refused to describe the mathematics in regards to quantum Strangeness so that paper wouldn't contain that detail with the needed math. Using toroids is nothing new in physics a cyclotron can be described using a toriod geometry. Yes you can mathematically describe any geometry in regards to an earlier comment of yours. Regardless if the person who did the math refused your conjecture then that wouldn't have the math beyond what the two of you were working on.

Thanks.

There is a unit of force called “lb force”, which is the force exerted by the weight, at the Earth’s surface, of a mass of 1lb. So lb x g is what it really means. One of the advantages of metric SI units, now used just about everywhere except the USA, is to avoid the potential confusion of this kind of thing. You would then have mass in kg, force in N and g in m/sec squared and less risk of confusing mass with force.

Hello. My name is Michael Panetta and I'm a science fiction writer. (If you read Analog Science Fiction And Fact, you may have seen my work in the current issue.) Anyway, I've created a fictitious virus that will act as a backdrop to a story, and I and am seeking someone to look over my notes about this virus and to tell me if there are any egregious errors. I would also like suggestions on a realistic name for the virus. I prefer to have this discussion over private message, so please message if you are interested in helping. I can't offer monetary compensation for your time because magazines don't really pay well, but if / when this story is published in a magazine, I will be sure to credit you. Kindly appreciated.

My colleague said that if you know how many square inches there are, you can determine how many pounds are up there based on how many pounds are in each square inch, and it can be obtained by multiplying: area*p But again, for me, the value obtained is in force unit and not in massa unit. What am I not understanding?

You're missing my point, not everyone is equal doesn't mean they're not capable; the great man only needs to exist when most people can't see the light. *sigh!!!* You sigh, but again point missed so I'll raise you a MEH... But you can't be arsed to be more specific, it's not like I forced you to participate in this topic, jeez... 🙄 Indeed, but who said science is the only path?

The thing is, the only people that has suffered since Japan are the people banging their heads against a brick wall. The Greenham Common Women's Peace Camp, for instance, I guess the 'peace camp' aspect was ironic, since no-one can fire the bloody thing's and plenty of cops got a knee in the balls defending an otherwise peaceful base.

Material needs to be posted here. What’s the electric dipole moment of a charged ring?

Thank you so much.

No, it is not possible to coordinate-transform a metric of the form: (ds)² = c² (dt)² – a(t)² ((dx)² + (dy)² + (dz)²) to a metric of the form: (ds)² = α(t)² c² (dt)² – ((dx)² + (dy)² + (dz)²) In general, a metric of the form: (ds)² = c² (dt)² – a(t)² ((dx)² + (dy)² + (dz)²) has non-zero Ricci curvature, whereas a metric of the form: (ds)² = α(t)² c² (dt)² – ((dx)² + (dy)² + (dz)²) describes flat spacetime. Note that this metric can be transformed to the Minkowskian metric by the coordinate transformation: t' = t'(t) ; x' = x ; y' = y ; z' = z where t'(t) is a solution to the differential equation: dt'(t)/dt = α(t)

This quantizes the Toroid without the travelling wave. David Bergman was a NASA engineer. I learned Quantum Physics from him, so I could program his math in a simulation. We stopped working together when I realized his Toroid needed the travelling wave to explain Quantum Strangeness and he refused. Now you can't say there isn't any math. https://www.semanticscholar.org/paper/Spinning-Charged-Ring-Model-of-Electron-Yielding-Bergman-Wesley/0f73035756eb139e4b3afa2aaa6c75ce814b2cfb

To give the twin scenario more “twist”, you can allow spacetime to not be flat (GR twin scenario). For even more twist, allow spacetimes that are topologically non-trivial

As KJW has pointed out, the equivalence principle is a purely local statement, meaning it applies only to small spacetime regions - meaning small volumes over short periods of time. Within such regions, there’s no purely local experiment you can perform to distinguish between the two. For the twin scenario, the twin can at every individual instant (or short enough time period) be considered to be subject to a uniform gravitational field, where the gravitational potential may vary from instant to instant. This kind of foliation procedure produces the correct results - though I still don’t think it’s necessarily the best way to analyse the twin scenario.

You are of course always free to pick different coordinates to describe the same spacetime - which is one of the central insights in GR. However, when you do this you also change the physical meaning of those coordinates. In the standard FLRW metric, the time coordinate is chosen such that it corresponds to a clock that is co-moving with the cosmological medium, meaning it fits well with our own physical clocks here on Earth, and thus the “phenomenology” of the metric corresponds to what we actually observe, without any need for complicated transformations. You are free to choose a coordinate system where eg tick rates aren’t constant, but then you need to be very careful how you relate the metric to real-world observations, since the t-coordinate no longer corresponds to Earth-bound clocks. Ultimately it is best to describe the spacetime in terms of geometric properties that are independent of coordinate choice; in the case of FLRW for example, we can say the spacetime is conformally flat, meaning during free fall angles are preserved, but not volumes. These aren’t different “theories”, but simply coordinate choices. You’re describing the same spacetime in different coordinates. KJW has given an example how a “time-only” expansion metric could look like. Ultimately you want to choose coordinates that make your calculations as simple as possible, and that’s often ones based on the cosmological medium. But in principle, the choice is yours, so long as they’re related by valid transformations.

If you can't be arsed to improve the clarity and coherence of your own argument then why should anybody else do it for you? It isn't as if it's a position worth defending.