Collision between the Milky Way and Andromeda and Redshift

[MartinG]

Hi ! My question is the following:

If there is a redshift in astronomical observations with other galaxies, as our Milky Way galaxy is approaching with the Andromeda galaxy, they must surely be in an accelerated approach due to the force of gravity between the two galaxies, and as our galaxy Vía Milky already be in a accelerated movement, it can influence the redshift that occurs in the observations with the other galaxies.

In other words, it could happen that the redshift that is observed with the other galaxies and that would lead to the conclusion that the universe is expanding in an accelerated way, cannot be confused with this accelerated movement that our galaxy would already have in his approach to the Andromeda galaxy.

I ask just in case. Perhaps this situation is already contemplated in the conclusion that is drawn from the accelerated expansion of the universe when the redshift is observed in the observations with the other galaxies, but I ask this question to remove this doubt.

I thank you for the answers and send you greetings.

 

[Vanadium 50]

I don't understand a thing you wrote. It sounds like a personal theory, though.

One fact you may be unaware of: M31 is blueshifted.

 

[phyzguy]

I think what you are saying is that the speed of the Milky Way galaxy as it approaches Andromeda could be confusing our measurements of the redshifts of other galaxies. There are several reasons why this is not the case, including these:

(1) We see distant galaxies receding in all directions. There is no way for motion of the Milky Way to cause distant galaxies to appear to be receding from us no matter which direction we look.

(2) Distant galaxies are receding from us at speeds of 50,000 km/sec and greater. The speed with which the Milky Way is approaching Andromeda is only about 100 km/sec.

 

[Keith_McClary]

Are you thinking of the "particular motion" (or "peculiar motion") as described in the NASA page How Fast Are You Moving When You Are Sitting Still?

 

[PeroK]

I don't understand a thing you wrote.

The question is whether cosmologists have forgotten to include the local velocity of the Milky Way relative to comoving coordinates in their calculations? Is it possible that this subtlely could have been overlooked by generations of cosmologists?

Or, has the OP overlooked the fact that the local velocity of the MIlky Way would lead to anisotropic redshift/blueshift depending on direction, rather than redshift in all directions depending only on distance and not on direction?

 

[Vanadium 50]

The question is

Got it.

While I agree that the hypothesis that generations of cosmologists (and the astronomers before them) are idiots is a difficult one to support, there is also evidence against it. There is evidence that the Earth is moving with respect to the uniform CMBR, it does not point in the direction of M31, and it is 6x larger.

 

[MartinG]

If it has already been explained to me that this effect of accelerated approach between the Milky Way and Andromeda is taken into account to explain the accelerated expansion that our universe has at this time.

Thanks.