To the 'believers' the evidence is always irrefutable.
No, the physical evidence are part of natural phenomena or physical phenomena that are being observed and tested.
What are refutable are the “explanatory” MODELS & “predictive” MODELS of the scientific theories or hypotheses.
It is the MODEL that can always be questioned or challenged.
And you would never just rely on one observation of evidence. Science required multiple evidence, the more evidence you have, the better grasp scientists would have to verify or to refute hypothesis or theory.
Having as many evidence you (scientists) can independently acquired, are part of “verification”.
As both
@Subduction Zone &
@ChristineM have said, one of the “indirect evidence” for Dark Matter is gravitational lensing.
Gravitational lensing have been observed where there are no ordinary matters or objects to create the gravitational field that distort the images of observations.
Gravitational lensing have been observed independently by different astronomers and astrophysicists from different observatories around the world. Plus, for decades, the Hubble have recorded a number of such observations.
So, gravitational lensing have been observed
(A) when there are ordinary matters (eg clouds of hydrogen gas and dust) and objects (eg asteroids, planets, stars, galaxies), are around,
(B) and when not of these ordinary matters and objects are absence in the observations.
For so many observations where there visible ordinary matters and objects around, then something else must have masses that caused gravitational distortion that EM cannot detect.
Ordinary matters (any molecule of atoms in the periodic table) give certain electromagnetic signatures that astrophysicists can recognize.
For instances, the most abundant elements in the universe is hydrogen. Hydrogen can distinguish between cold neutral hydrogen gas and plasma of hydrogen. Both give different EM wavelengths whether they be cold gas form or in plasma form (ionized hydrogen). Astrophysicists can also identify helium, carbon, oxygen, etc, in space, through radio astronomy.
There are matters that are not detected electromagnetically.
Did you know there are some elementary subatomic particles that exhibit the same characteristics as dark matter?
These are groups of neutrinos (there are 3 types).
Neutrinos don’t interact with EM forces and strong nuclear forces, but do interact with gravitational forces and weak nuclear forces.
Meaning, neutrinos have no electrical charge (hence are not affected by EM forces), but do have masses. But the mass is so small, it has even less mass than electron. The point being, radio telescopes relied on EM waves (eg infrared, ultraviolet, microwave, radiowaves, etc) to detect matters and large physical bodies (eg planets, stars, etc), but you cannot use radio astronomy to detect these neutrinos.
Neutrinos are detect underground, using phototubes, and some of medium, like heavy water or solid plastic. Observations are taken underground, because neutrinos are streaming quickly, passing through solid object, like the Earth for instance, without slowly down, so detection are difficult.
Dark Matter are like neutrinos, that can interface with gravitation, but not electromagnetic forces.
Anyway. What we can determine about Dark Matter, is they do have mass, but do not reflect or absorb EM waves.
