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Originally Posted by modest
In fact, galactic rotation curves leave 2 possibilities: GR is wrong, there is unaccounted-for mass.
The only way to make galactic rotation curves agree with General Relativity is to add mass because GR itself cannot be tweaked—it cannot be adjusted. This is something you often disagree with for one reason or another, but it isn't open to interpretation. GR is exactly demanding.
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Indeed, this situation seems to require the introduction of non-baryonic matter (a hypothetical form of matter not made of electrons, protons, neutrons, quarks, etc.). It is a well-known that much of the mass in the universe is invisible to our telescopes. Planets, rocks, asteroids, brown dwarfs, often called “massive astrophysical compact halo objects” (MACHOS), objects with very little (or no) surface luminosity. But these objects may be insufficient to appease the necessary constraints.
Only 20% of the dark matter in our galaxy is in the form of MACHOs.
True, then, there appears to be an additional budgetary problem, but I wouldn't count on something nonbaryonic until it can be demonstrably tested experimentally that such a bizarre form of material exists. As you know, I argue that there is no such thing. Like eather of the 19th century, I suppose we'll have to live with it for a while, until an alternative quantitative solution (aside from MOND) emerges that does away with the untenable concept. (There already exists a qualitative scenario
).
Perhaps there will be found a way to adjusted GR (with a slight modification) in such a way that allows for the observed curves without revamping the entire postulate.
It seems logical that such an analytical solution should be sought, rather than accepting unilaterally the
ethereal, the
dark, without palpable empirical evidence.
Quote:
Originally Posted by modest
...The same theory that predicts gravitational effects in our solar system to extraordinary precision also predicts the behavior of the FLRW metric (i.e. a Friedmann universe). Any observation of a homogeneous, isotropic universe that obeys the physics of General Relativity *must* agree with the FLRW metric or General Relativity is proven wrong by example. There is no leeway on this.
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The difference is that there is no need for CDM or DE within solar system dynamics (GR works). The same cannot be said of a Friedmann universe, where GR needs to be supplemented liberally.
That doesn't mean GR is wrong. It could simply be that the FLRW metric is not the metric of choice when it comes to describing the universe. If the latter is the case, then there is your leeway.
Quote:
Originally Posted by modest
Our cosmic observations do indeed agree with the FLRW metric if the makeup of the universe is currently 74% vacuum energy density and 26% mass density as a ratio to the critical density. Either this is not the makeup of our universe, the universe is not homogeneous and isotropic, or FLRW and by extension GR are wrong.
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It would have been a beautiful result had cosmic observations agreed with the FLRW metric without 74% vacuum energy and 26% nonbaryonic cold dark mass density.
Now the beauty is nowhere to be found.
Quote:
Originally Posted by modest
The only Leeway FLRW affords is setting the values (the Omegas) which is the same as declaring what our universe is made of. That's it.
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I know you feel DE and CDM follow naturally from GR or FLRW, but believe me, there is nothing natural about it.
Dangit them
SNe Type Ia.
Quote:
Originally Posted by modest
You seem to be confusing the setting, measuring, and changing of these parameters with a change to the underlying physics.
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Underlying physics has to change.
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High-energy physicists have proposed various candidates for non-baryonic dark matter, all of which would indicate new physics beyond the well tested Standard Model of particle physics. [...]
Another candidate for non-baryonic dark matter is the family of heavier neutral particles known as weakly interacting massive particles or WIMPs. The leading candidate in this class is the neutralino, a particle predicted by the so-called supersymmetric (SUSY) extension to the Standard Model. [...]
Altogether there are now more than a dozen experiments searching for WIMPs, plus several experiments that are looking for axions - very light particles with masses in the range 10-4-10-6 eV c-2 that have been predicted to exist by several theories. Detection of a WIMP particle or an axion would clearly have a major impact on future directions in particle physics. Source: The search for dark matter
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Quote:
Originally Posted by modest
You can set Omega-M and Omega-Vac and get a prediction at a chosen redshift. Pre-1998 cosmology can be solved on this calculator as well as the current Lambda-CDM model, because they use *exactly* the same physics.
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PS. Check this out.
The world's first space resort in orbit by 2012, a good place to ponder the fate of the universe. It's not too late to make your reservations.
CC
