[Sephiroth]

Originally Posted by idi banashapan

Correct, there is no certainty it exists. It is just the best explanation (that dark matter does not interact with light, but does have mass, as something is holding things together) that fits the driven theories used in physics (Newton’s laws of motion and Einstein’s theory of relativity). Keep in mind dark matter has not been show horned into the theories, more the observations in relation to the theories show that something is missing. It’s the most logical answer to what is being seen.

The other option is that physics needs a new theory, such as Modified Newtonian Dynamics.

First, I thank Joglynne for the kind words! The "depth of knowledge" does, however, stretch into sheer speculation.

@Idi suggests that the non-shoe-horning of dark matter into theories is the "most logical answer".

Obviously, this is where I contend otherwise. Logic says that you can't delve back to the beginning of the formation of matter because that's happened and we (our galaxy) must have happened much later. Or did it? Maybe it was always there in which case all sorts of light from everywhere that is not shifted outside our detection ranges can be observed.

The bit that's teasing the people who appear in money earners such as How the Universe Works, is why is the universe, according to their measurements, expanding at an increasing rate (acceleration)? So, "dark matter" and "dark energy" are invented (coefficient K) that balances the equations.

If they can see events from 13.5 billion years ago with the latest space telescopes, why isn't the so-called "dark matter" visible? Presumably because it's been conveniently named "dark" and thus we cannot see it. So, might it not be there? But it has to be there because something must account for the expanding universe. And so we go round in circles looking for the coefficient K - which cannot be found.

But some on this thread and various scientists say that galaxies that are receding from us at greater than the speed of light will always be invisible to us. So why do all the scientists say that nothing can travel faster than light because of Einstein's E=MC^2? Does the receding galaxy "know" it's travelling faster than the speed of light relative to something that cannot see it?