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What is Mainstream views on...
Discussion in 'The Cesspool' started by The God, Apr 17, 2016.
The God Valued Senior Member
Warning points issued for harassment, trolling and incoherent and aggressive reporting on resulting posts.
In recent postings one of the new members Schneibster has given certain interpretations and asserts that the same are the prevalent mainstream views...since the views expressed by him are not held by many here and objectsions were raised, so it is pertinent that we all understand what is prevalent mainstream position on these points. [Moderator: You don't have the right to demand an answer. The named user has put you, according to recent posts, deservedly on ignore. In every case, you would have been better served writing a simple essay stating in positive terms what you believe and why you believe it rather than trying to tear down the position of another which you may not be fully equipped to understand.]
I had requested Mods to clear the air, even Schneibster urged Rpenner to put forth his views on one of the points, but he is yet to make any comments. [Moderator: You don't have the right to demand an answer.] I would request Rpenner/James R to give their views and also if possible organize some authoritative responses; are we missing Tashja ?
1. Cosmological Redshift is Doppler Shift. [Moderator: Observationally, cosmological redshift is indistinguishable from Doppler shift or gravitational redshift. Theoretically, anything less than full treatment in GR is subject to attack. Rhetorically, anyone starting a new thread to debate someone's breezy pop physics analogy commits an error by not citing the original claim in context. Socially, to start a new thread makes you look like you lack maturity and are engaged in a campaign of harassment.]
2. Spacetime is a thing (in Physical sense), otherwise how will it have curvature etc. [Moderator: What is treated like a real thing in physics is the geometry and curvature of space-time just like the electromagnetic field was treated like a real thing in Maxwellian electrodynamics. But relativity shows what was important in old EM theory was not the description of the E field and M field in any one set of coordinates but the geometric description of the EM field in general coordinates. So provisionally (until a better theory of space, time and electromagnetism comes along) the geometry of space-time is treated like a real thing. Colloquially, this means space-time is real thing. Arguing about if that's true is specious, unimportant and the promotion of form over substance. Creating a new thread to argue about that without citing the original claim in context is a breach of civility and best practices.]
3. Big Bang happened after Inflation. [Moderator: Big Bang cosmology is the observation that the earlier universe was hotter and denser and more uniform without empirical limits. All times when the universe was too hot and uniform to allow stars to form are part of Big Bang cosmology, because such conditions were terribly at odds with the old competitor called Steady State. Inflation is a mechanism proposed to allow the early universe to be super-uniform. To rigorously address any hypothetical first event in Big Bang cosmology one needs a theory of physics which correctly describes such events, which has never been part of the conversation. But many aspects of Big Bang cosmology must have happened long after the period when any hypothetical inflation mechanism was important and therefore after the hypothetical first event. Therefore this sentence makes no sense bereft of original context. Inflation, if it happened, was important during part of the Big Bang early universe. So creating a new thread to argue about it as if it was another's simple claim is a disservice to the forum community and betrays either a misunderstanding of cosmology or a willingness to write nonsense.]
I completely disagree on first two as his views are not the mainstream views, may be these views are held by a minority of Physicists but they do not represent the mainstream. [Moderator: Citation required.] Point # 3 is totally different from what is known to people at large, but this is a Hypothesis over Hypothesis, extremely speculative scenario leading to multiverse etc. So this cannot be termed as mainstream as yet. [Moderator: Nonsense.]
I will take up one by one....not my opinion but the opinion of mainstream guys, educational institutions.....Schneibster has to prove them wrong or outdated....or retract.
1. Cosmological Redshift is not Doppler Shift.....
http://cecelia.physics.indiana.edu/life/redshift.html said:
It is tempting to refer to cosmological redshifts as Doppler shifts. This choice of interpretation has in the years since Hubble's work led to an unfortunate misunderstanding of big bang cosmology, obscurring one of its most mysterious beauties. As noted with a hint of frustration by cosmologists such as Steven Weinberg and Jaylant Narlikar and John Wheeler, "The frequency of light is also affected by the gravitational field of the universe, and it is neither useful nor strictly correct to interpret the frequency shifts of light...in terms of the special relativistic Doppler effect.".
By refering to cosmological redshifts as Doppler shifts, we are insisting that our Newtonian intuition about motion still applies without significant change to the cosmological arena. A result of this thinking is that quasars now being detected at redshifts of Z = 4.0 would have to be interpreted as traveling a speeds of more than V = Z x c or 4 times the speed of light. This is, of course, quite absurd, because we all know that no physical object may travel faster than the speed of light.
To avoid such apparently nonsensical speeds, many popularizers use the special relativistic Doppler formula to show that quasars are really not moving faster than light. The argument being that for large velocities, special relativity replaces Newtonian physics as the correct framework for interpreting the world. By using a special relativistic velocity addition formula the quasar we just discussed has a velocity of 92 percent the speed of light. Although we now have a feeling that Reason has returned to our description of the universe, in fact, we have only replaced one incomplete explanation for another. The calculation of the quasar's speed now presupposes that special relativity ( a theory of flat spacetime) is applicable even at cosmological scales where general relativity predicts that spacetime curvature becomes important. This is equivalent to a surveyor making a map of the state of California, and not allowing for the curvature of the earth!
The adoption of the special relativistic Doppler formula by many educators has led to a peculiar 'hybrid' cosmology which attempts to describe big bang cosmology using general relativity, but which is still firmly mired in the ruberik of special relativity. For instance, under the entry 'redshift' in the Cambridge Encyclopedia of Astronomy it is explicitly acknowledged that the redshift is not a Doppler shift, but less than two paragraphs later, the special relativistic Doppler formula is introduced to show how quasars are moving slower than the speed of light! It is also common for popularizers of cosmology to describe how 'space itself stretches' yet continue to describe the expansion of the universe as motion governed by the restrictions of special relativity. What's going on here?
http://astronomy.swin.edu.au/cosmos/c/cosmological+redshift said:
Although cosmological redshift at first appears to be a similar effect to the more familiar Doppler shift, there is a distinction. In Doppler Shift, the wavelength of the emitted radiation depends on the motion of the object at the instant the photons are emitted. If the object is travelling towards us, the wavelength is shifted towards the blue end of the spectrum, if the object is travelling away from us, the wavelength is shifted towards the red end. In cosmological redshift, the wavelength at which the radiation is originally emitted is lengthened as it travels through (expanding) space. Cosmological redshift results from the expansion of space itself and not from the motion of an individual body.
List is endless...either these people are giving incorrect or outdated version of mainstream or Schneibster is pushing an opinion held by a few....He must retract or prove them wrong.
The God, Apr 17, 2016
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paddoboy Valued Senior Member
The God said: ↑
...He must retract or prove them wrong.
[1] You appear ignorant of the application of "proof" with regards to scientific theories, despite having had it explained to you many times in many threads.
[2]And rather hypocritical of you to "demand"anyone retract anything, considering the numbers of errors you have made here including two nonsensical threads moved to pseudoscience.
[3] All issues you mention have been explained to you in the appropriate thread, and as usual you have [a] ignored them, misinterpreted them and [c] just plain not capable of understanding them.
paddoboy, Apr 17, 2016
hansda Valued Senior Member
The God:
My views on spacetime is as below.
2. Spacetime is a thing (in Physical sense), otherwise how will it have curvature etc.
We can consider spacetime as: Spacetime = Space + Time. So, Curvature of spacetime = Curvature of space + Curvature of Time. As, Curvature of Time does not make any sense, we can consider this as Dilation of Time.
So, Curvature of Spacetime = Curvature of Space + Dilation of Time.
hansda, Apr 17, 2016
Q-reeus Valued Senior Member
In recent postings one of the new members Schneibster has given certain interpretations and asserts that the same are the prevalent mainstream views...since the views expressed by him are not held by many here and objectsions were raised, so it is pertinent that we all understand what is prevalent mainstream position on these points.
I had requested Mods to clear the air, even Schneibster urged Rpenner to put forth his views on one of the points, but he is yet to make any comments. I would request Rpenner/James R to give their views and also if possible organize some authoritative responses; are we missing Tashja ?
1. Cosmological Redshift is Doppler Shift.
3. Big Bang happened after Inflation.....
1. Cosmological Redshift is Doppler Shift
Subject to interpretation. Taking the expansion of space (more space created - not 'stretching' of space locally) as a given, cosmological redshift can be seen as owing to Doppler shift or time anti-dilation (clock-rates in the past slower relative to now). Pushing one interpretation as 'it' is silly.
Schizophrenic within GR. On the one hand it's considered as simply a mathematical framework allowing accurate predictions. Spacetime curvature real in the mathematical sense. But, given zero Ricci scalar for all vacuum solutions, formally devoid of energy-momentum content, at least on a consistent basis (covered elsewhere). On the other hand, the evident reality of GW's carrying real energy-momentum automatically implies a reality to 'curved spacetime' as having or additionally containing 'ponderable ether' properties of some sort. No way around that.
3. Big Bang happened after Inflation.
Down to inconsistently used convention. Probably a majority divide things into a pre-inflationary phase initial BB, and a post-inflationary phase hot BB. Not an either or thing. I personally like the drift of recent articles by Paul Steinhardt pushing the anamorphic universe idea - it looks promising.
Q-reeus, Apr 17, 2016
What a bunch of nonsense .
river, Apr 17, 2016
...Schneibster has given certain interpretations and asserts that the same are the prevalent mainstream views...
This is a common problem.
It isn't. They're somewhat similar but they aren't the same. See Wikipedia.
"There is a distinction between a redshift in cosmological context as compared to that witnessed when nearby objects exhibit a local Doppler-effect redshift. Rather than cosmological redshifts being a consequence of relative velocities, the photons instead increase in wavelength and redshift because of a feature of the spacetime through which they are traveling that causes space to expand.[27] Due to the expansion increasing as distances increase, the distance between two remote galaxies can increase at more than 3×10\(^8\) m/s, but this does not imply that the galaxies move faster than the speed of light at their present location (which is forbidden by Lorentz covariance)."
This article says spacetime where it should say space, see below.
It isn't. Space is. Spacetime is an abstract mathematical space which models space at all times. We can draw world-lines and light-cones in it, but these are abstract things too. See what relativist Ben Crowell said here:
"Objects don't move through spacetime. Objects move through space."
Big Bang happened after Inflation.
It didn't. Search the internet, it's the other way around. By the by, I'm not a fan of inflation myself. I have no issues with the big bang or the expanding universe, but I think inflation is superfluous and unscientific. See Physicist Slams Cosmic Theory He Helped Conceive.
I completely disagree on first two as his views are not the mainstream views, may be these views are held by a minority of Physicists but they do not represent the mainstream. Point # 3 is totally different from what is known to people at large, but this is a Hypothesis over Hypothesis, extremely speculative scenario leading to multiverse etc. So this cannot be termed as mainstream as yet.
Some people will tell you the multiverse is mainstream.
It is tempting to refer to cosmological redshifts as Doppler shifts. This choice of interpretation has in the years since Hubble's work led to an unfortunate misunderstanding of big bang cosmology, obscurring one of its most mysterious beauties. As noted with a hint of frustration by cosmologists such as Steven Weinberg and Jaylant Narlikar and John Wheeler, "The frequency of light is also affected by the gravitational field of the universe, and it is neither useful nor strictly correct to interpret the frequency shifts of light...in terms of the special relativistic Doppler effect."
One of the problems with all this stuff is that sometimes even authoritative people get it wrong. See this article on Cosmological redshift at Cornell:
"This is a special case of a more general phenomenon known as the "gravitational redshift" which describes how gravity's effect on spacetime changes the wavelength of light moving through that spacetime."
It's wrong on multiple counts. Light doesn't move through spacetime, it moves through space. And when it moves through space where there's a gravitational field, it doesn't change wavelength. See what Einstein said here.
"An atom absorbs or emits light at a frequency which is dependent on the potential of the gravitational field in which it is situated".
The light is emitted at a lower frequency at a lower elevation. It doesn't reduce in frequency as it ascends. Nor does it increase in frequency as it descends. What actually happens is that you and your clocks go slower when you're lower, so you measure the selfsame photon frequency to be higher. Conservation of energy applies.
Farsight, Apr 17, 2016
hansda said: ↑
We can consider spacetime as: Spacetime = Space + Time. So, Curvature of spacetime = Curvature of space + Curvature of Time. As, Curvature of Time does not make any sense, we can consider this as Dilation of Time. So, Curvature of Spacetime = Curvature of Space + Dilation of Time.
I'm afraid this is wrong hansda. Space isn't curved in a gravitational field. See Baez:
"Similarly, in general relativity gravity is not really a 'force', but just a manifestation of the curvature of spacetime. Note: not the curvature of space, but of spacetime. The distinction is crucial."
See Einstein talking about space as the aether of general relativity here:
"According to this theory the metrical qualities of the continuum of space-time differ in the environment of different points of space-time, and are partly conditioned by the matter existing outside of the territory under consideration. This space-time variability of the reciprocal relations of the standards of space and time, or, perhaps, the recognition of the fact that 'empty space' in its physical relation is neither homogeneous nor isotropic, compelling us to describe its state by ten functions (the gravitation potentials gμν, has, I think, finally disposed of the view that space is physically empty."
Space is inhomogeneous where a gravitational field is, and when you plot this using rods and clocks, your plot is curved.
Farsight said: ↑
Spacetime being mathematical concept ; rather than a substance based concept.
river said: ↑
It's proper netiquette to quote - especially when making such a derogatory statement. Not that it matters - but who or what were you referring to? Because the default assumption is it was to me!
[Cowardice combined with disrespect is unfortunately something endemic to SF, and has newly manifested this thread!!]
Atleast in Gravitational Lensing, space is curved. This is physically confirmed by the bending of light. So, something(some physical thing) is bending to cause gravity.
Even in Newtonian action-at-a-distance gravity, light bends, but by only half the GR value. So it's the amount of deflection that requires curvature of some sort as explanation. Actually, 1911 GR gave the equivalent deflection to Newtonian gravity - based on 'time curvature'. The 1916 GR version added the spatial part.
Q-reeus said: ↑
Even in Newtonian action-at-a-distance gravity, light bends, but by only half the GR value.
Which Newtonian equation of gravity you are considering to calculate the bending of light?
So it's the amount of deflection that requires curvature of some sort as explanation.
In Newtonian model of gravity, is there any concept of curvature?
I must go, but suggest you do a search for 'bending of light in Newtonian gravity'. There will be plenty of hits I'd imagine.
And if this is troubling you, check out "eternal Inflation" and also
Spacetime is seen to be bent, warped, curved, twisted in the presence of mass and recent discoveries have confirmed a reality of spacetime.
https://einstein.stanford.edu/content/relativity/q411.html
https://www.quora.com/Is-spacetime-a-real-thing-or-just-a-mere-concept
Space isn't curved in a a gravitational field. Instead it's inhomogeneous. Light curves in a similar fashion to the way sound waves curve underwater, see this sonar article:
The water isn't curved, instead it's inhomogeneous. The temperature and/or salinity and/or density varies with depth, and so does the speed of sound.
Not really. But Newton did say this in Opticks query 20:
"Doth not this aethereal medium in passing out of water, glass, crystal, and other compact and dense bodies in empty spaces, grow denser and denser by degrees, and by that means refract the rays of light not in a point, but by bending them gradually in curve lines?"
I think this is fairly close to what Einstein said about space being neither homogeneous nor isotropic.
Spacetime is curved/warped/twisted in the presence of mass, which exhibits the property we call gravity.
Spacetime though certainly not a material entity, is just as certainly real:
or as rpenner so exquistely put it.......
What is treated like a real thing in physics is the geometry and curvature of space-time just like the electromagnetic field was treated like a real thing in Maxwellian electrodynamics. But relativity shows what was important in old EM theory was not the description of the E field and M field in any one set of coordinates but the geometric description of the EM field in general coordinates. So provisionally (until a better theory of space, time and electromagnetism comes along) the geometry of space-time is treated like a real thing. Colloquially, this means space-time is real thing.
paddoboy said: ↑
Actually it's a concentration of energy that causes gravity. A massive star results in gravity because of the energy-content. And spacetime curvature relates to the tidal force whilst spacetime "tilt" relates to gravity. See the tilted light cones here:
Note though that a light-cone is an abstract thing. You can't point up to the clear night sky and say "there's a light cone".
Spacetime though certainly not a material entity, is just as certainly real: https://einstein.stanford.edu/content/relativity/q411.html
See this quote from that article:
"Space-time does not evolve, it simply exists. When we examine a particular object from the stand point of its space-time representation, every particle is located along its world-line. This is a spaghetti-like line that stretches from the past to the future showing the spatial location of the particle at every instant in time. This world-line exists as a complete object which may be sliced here and there so that you can see where the particle is located in space at a particular instant..."
A world-line is an abstract thing too. And we don't live in some static "block universe" world. We live in world of space and motion. It does evolve.
or as rpenner so exquisitely put it....... What is treated like a real thing in physics is the geometry and curvature of space-time just like the electromagnetic field was treated like a real thing in Maxwellian electrodynamics.
An electromagnetic field is a real thing, as is a gravitational field. And there is an underlying reality to curved spacetime.
But relativity shows what was important in old EM theory was not the description of the E field and M field in any one set of coordinates but the geometric description of the EM field in general coordinates. So provisionally (until a better theory of space, time and electromagnetism comes along) the geometry of space-time is treated like a real thing. Colloquially, this means space-time is real thing.
IMHO a better way of saying it is that a gravitational field is most definitely a real thing, that we model it using curved spacetime, and that there is an underlying reality to curved spacetime. But you need to take care about saying spacetime is a real thing, because there's no motion in spacetime. See what relativist Ben Crowell said here: "Objects don't move through spacetime. Objects move through space. If you depict an object in spacetime, you have a world-line. The world-line doesn't move through spacetime, it simply extends across spacetime". You can't see a world-line, but you can see motion. Motion is real. A world-line is an abstract thing. It is in essence a line on a map, and the map is not the territory.
Concentration of energy?? Bit pedantic aren't we? Considering we all know that E=Mc2 and naturally follows that mass/energy causes spacetime to curve which we see as gravity, just as I said.
Yep, an EMF is real, just as a gravity field is reall, which resulting from curved spacetime, follows that spacetime is also real.
Forgetting the pedant, so far we seem to be on the same page.
That's OK, your opinion is your opinion:
I prefer the original though.
Since the red text is of technical in nature, the Moderator should disclose his name as urged in the Open Govt Sub forum and he should remove this text from the OP and create a new post as expert member.
To this Moderator
1. if you feel that cosmological redshift is doppler redshift, then you are declaring both the references given by me in the OP as wrong. What makes you think that I should believe an unnamed and hasty moderator of this site over those two links citing educational institutions and professors ?
2. if you feel that spacetime is real, then you are declaring Prof Geraint F lewis as wrong, whose specific quote and paper I cited. What makes you think that I should believe an unnamed and hasty moderator's colloquial understanding and pure semantic nonsense over that of Prof Views.
3. I don't care about 3rd point......You can decide with Schneibster and declare that BB came after inflation. Although I will ask you to read about the standard mainstream text and look at the time line of expanding universe.
It really helps !!