Five Brilliant Ideas For New Physics That Need To Die, Already

[swansont]

2 hours ago, J.C.MacSwell said:

The size, brightness, and most particularly distances from the galaxy centres are directly related to the distance away and therefore the rotation curves. M33 is in the Local Group (where one would expect some of the more accurate estimates) Velocity measurements from redshift effects based on distance (Hubble effects) would become significant much further away. 

 

But these velocity measurements are based on Doppler shifts, aren't they? Radial distance within the galaxy scales with distance away, so the radial velocity does, too. Meaning the effect of uncertainty in the distance cancels when you plot radial distance and radial velocity. 

And more than one galaxy has been measured, so there's more data out there than one galaxy.

[J.C.MacSwell]

1 hour ago, swansont said:

But these velocity measurements are based on Doppler shifts, aren't they? Radial distance within the galaxy scales with distance away, so the radial velocity does, too. Meaning the effect of uncertainty in the distance cancels when you plot radial distance and radial velocity. 

And more than one galaxy has been measured, so there's more data out there than one galaxy.

Assuming I'm thinking it through correctly:

Not for doppler shift measurements, no (Hubble effects aside). Wouldn't it exacerbate a problem if it did, rather than cancel?

Allowing for Hubble at greater distances would not cancel either. If say you overestimated the distances and you then overestimate the speeds, these both lead to looking for more dark matter.

You should however get some cancelling from overestimating mass (thus looking for less dark matter)

(by radial velocity here you aren't referring to radial velocities within the galaxy, are you, but radial velocities wrt Earth used to calculate the tangential velocities at radial points, thus rotation curves, of the distant galaxy? )

 

[swansont]

1 hour ago, J.C.MacSwell said:

Assuming I'm thinking it through correctly:

Not for doppler shift measurements, no (Hubble effects aside). Wouldn't it exacerbate a problem if it did, rather than cancel?

 

You're right. I had reversed the effect in my head.

But getting the distance wrong stretches or shrinks the graph. It doesn't change the shape.  

1 hour ago, J.C.MacSwell said:

Allowing for Hubble at greater distances would not cancel either. If say you overestimated the distances and you then overestimate the speeds, these both lead to looking for more dark matter.

You should however get some cancelling from overestimating mass (thus looking for less dark matter)

(by radial velocity here you aren't referring to radial velocities within the galaxy, are you, but radial velocities wrt Earth used to calculate the tangential velocities at radial points, thus rotation curves, of the distant galaxy? )

I meant to type angular velocity.

[J.C.MacSwell]

19 minutes ago, swansont said:

 

But getting the distance wrong stretches or shrinks the graph. It doesn't change the shape.  

 

It can effect the amount of dark matter required but obviously not enough to try to explain it otherwise.

My main point was that much of the data is less accurate generally than implied by the error ranges given. Much of it for reasons unique to Cosmology.

[Mordred]

In terms of dark matter, vs baryonic on rotation curves.

The main focus is the mass/luminosity relation including the relevant redshift effects (gravitstional within local group) gravitational bound system so Hubble isn't accurate in this case, which involves Cosmological redshift.. Though M33 will also involve Doppler.

This also correlates to how Zwicky realized DM was required as it involved the mass/luminosity with a large part involving Jeans equation/Euler hydrodynamics. Currently estimates of DM clusters still use this technique though more advanced in treatment. One can apply the above and estimate the affect DM has on temperature. Though not directly via the properties of DM which are largely unknown.

For universe particle number estimates one can apply the Bose-Einstien and Fermi Dirac statistics combined with nucleosynthesis and our current knowledge of particle physics.

Utilitizing known particle degrees of freedom, spin, charge, etc one can apply these attributes to their contribution to temperature. From this we can apply those contributions to get the number density of any particle via the blackbody temperatures. For example one can calculate the number density of photons and neutrinos etc etc from CMB temperature etc. Not to mention the practical application as applied to stars/galaxies/plasma clouds etc.

DM if a distinct particle will also have distinct thermodymanic relations ( unfortunately we can only make assumptions as to what property values to use).

 However one can  still eliminate what is known from the luminosity data.

 

 

[Mordred]

Note to above. Euler Hydrodynamics is described by the Euler equations. Both can be applied, though some limitations. The Euler method is by far easier with less limitations.

Edited October 12, 2017 by Mordred