[trhway]

Also not a physicist. At the galactic scale gravity forces are too weak to take into account any non-Newtonian considerations. At least for myself, most things observed so far at galactic scale, like flat disk star orbital speed for example, can be easily explained by straight 6th grade Newtonian physics.

[titzer]

sigh I wouldn't have replied to this if you hadn't posted half a dozen comments. When I was 16 I thought special relativity was a hoax and I tried to demonstrate this with triangular diagrams scribbled in pencil in my notebooks. I ended up just rediscovering the Doppler effect. I never showed it to anyone, but when I think back, I still cringe a little. Relativity and time dilation are real things with real theory and real experiments.

You'd do well to do a little more research on the topic before posting so many comments on HN.

There is a ton of evidence for dark matter. We still don't know exactly what it is, but we do know lots about it (e.g. it is not baryonic matter because observation differs from theoretical models of how it would interact with ordinary baryonic matter). As for all that other evidence, the first hit on Google is for laymen: https://medium.com/starts-with-a-bang/five-reasons-we-think-...

TLDR: gravitational lensing, missing mass, and three other really good reasons that dark matter is a serious subject of study.

Disclaimer: I am not a physicist. And I'm trying not to represent myself as one on HN.

Talking about this stuff is fun, sure. It's great to learn! But please don't spread ignorance with such high confidence. As for "just" Newtonian physics, there's a whole research field called "Modified Newtonian Dynamics" (MOND). https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics

TLDR; there are lots of problems with MOND, and it doesn't explain gravitational lensing and other effects of dark matter that we see.

[phkahler]

Another fun experiment is to write script to cover a disk with points, then do a full calculation of all N gravitational forces at a point along the radius. Calculate the acceleration of a mass at that point and back-calculate the velocity that would orbit with that inward force. Repeat this for many points along the radius and plot the rotation curve without doing any dynamic simulation. There can be some interesting numerical issues with this but a random set of points to "measure" the curve will still show it.