Why do we believe dark matter exists?

[badseed]

He didn't regret it because it was "wrong". He regretted it because, if he hadn't postulated it, but had taken the simplest cosmological model based on his original field equation (without the CC), he might have predicted the expansion of the universe more than ten years before it was discovered. That has nothing to do with whether or not the CC is a "natural" part of the field equation; it's simple to show that it is by deriving the EFE from a Lagrangian.

(It's also worth nothing that the implicit argument you are making here is an argument from authority, i.e., not a valid argument. Even if the authority is Einstein. Einstein made mistakes, just like all humans do.)

EFE - Euler Fluid Equations? lol

I see, "his original field equation (without the CC), might have predicted the expansion of the universe" but the CC " is a natural part of the field equation"

This cool thing?

Models which attribute the redshift to anything other than expansion of the universe don't fit the data.

Yet redshift has been demonstrated in experiments independent of expansion - could be a problem.

OK, I give up ( I have work to do) - Dark matter and dark energy are real, they where discovered in 1933 or something; gravity is the only fundamental force that effects galaxy scale motion and redshift is only caused by expansion (someone should tell Chen, he thinks it was a result of electron density in his experiments).

 

[badseed]

Maybe it is an invisible Pink Unicorn pulling the galaxies together. Would that be "simpler" for you?

lol... You should know that in the order of likeliness, I put pink unicorns just below dark matter.

 

[Drakkith]

This is silly. Dark matter is simply the explanation that best fits the available data at this time. You don't have to like it, but you cannot fault science for coming to this conclusion and try to hand-wave away decades of work by thousands of people trained to answer these very questions. In any case, PF does not exist to argue what in science is right or to convince people of anything. It exists to teach people about mainstream science, including dark matter, expansion, and a thousand other theories that sometimes seem ludicrous to people. Thread locked.