Is Dark matter an optical illusion?

Click For Summary
SUMMARY

The discussion centers on the evidence for dark matter, specifically the flat rotation curves of galaxies and the peculiar velocities of galaxies in clusters. The mass enclosed in a radius R is calculated using the Keplerian equation M(R) = v²R/G. The role of gravitational lensing is critically examined, highlighting how it affects the perceived position and speed of stars, potentially leading to miscalculations of mass. The conclusion is that while gravitational lensing distorts observations, it does not imply that dark matter is merely an optical illusion.

PREREQUISITES
  • Understanding of Keplerian dynamics and the equation M(R) = v²R/G
  • Familiarity with gravitational lensing and its effects on light trajectories
  • Knowledge of galactic rotation curves and their significance in astrophysics
  • Basic concepts of redshift and its implications for measuring stellar velocities
NEXT STEPS
  • Research the implications of gravitational lensing on astronomical observations
  • Study the methods for calculating mass distributions in galaxies
  • Explore the relationship between redshift and angular velocity in astrophysical contexts
  • Investigate alternative theories regarding dark matter and their critiques
USEFUL FOR

Astronomers, astrophysicists, and students of cosmology interested in the complexities of dark matter and gravitational lensing effects on galactic observations.

Zimbler Igor
Messages
1
Reaction score
0
The main evidence for the existence of dark matter is the flat rotation curve of galaxies, and high peculiar velocities of galaxies in galaxy clusters.

GalaxyRotationCurve.png


The mass eclosed in a radius R is derived from the Keplerian equation M(R) = v2R/G .

Also we know about the existence of gravitational lensing.
GravitationalLensingScenario.png

My question is this: was gravitational lensing taken into account when galactic rotation curves were plotted? Because here is an effect of gravitational lensing that I didn`t find mention of:
GL.png


The photon emmited by the star can`t travel directly to the observer because it is gravitationally pulled to the center of the galaxy, so its trajectory is bent. And because of this bending effect the observer will see the star as being farther away from the galactic center. This in turn will push the observer to the conclusion that there is more mass enclosed in the observed radius. If the orbital speed of the star is not calculated from it’s red shift then it will also appear to be bigger then it actually is, since v = w*r, where w – angular velocity, r – observed radius.Consequences:1) All massive celestial objects appear greater then they actually are.2) The farther away the celestial object from the observer the stronger the magnification effect.

GL2.png


3) Most of the distant celestial object that we observe are not actually in the direction that we observe them.

GL3.png


P.S.: The fish is also distorted

Cat_looking_at_fish_in_a_bowl.jpg
 
Astronomy news on Phys.org
No, dark matter is not an optical illusion. Since we don't deal with speculation and personal theories here at PF, thread locked.
 

Similar threads

Replies
8
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 40 ·
2
Replies
40
Views
6K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 11 ·
Replies
11
Views
2K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 65 ·
3
Replies
65
Views
9K
  • · Replies 12 ·
Replies
12
Views
5K
  • · Replies 2 ·
Replies
2
Views
3K