alt Hacker NewsWe measure the matter distribution by its affect on light (strong/weak lensing). We also measure the matter distribution by the amount of light coming from it. The results are not the same. The simplest explanation is that there is matter which does not produce or reflect light via e/m, i.e. it is dark. Dark Matter.
We know of particles which behave the same way. Neutrinos for example.
You're saying the same thing, we see some anomaly in measured light and we say "the simplest explanation is dark matter".
We are not measuring dark matter, we are measuring something that is not what we expect and we decided it's dark matter.