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Comment by zehaeva | Hacker News Reader

Mostly because no one has found a modified version of gravity that can explain all of the observed data.

https://royalsocietypublishing.org/doi/abs/10.1098/rsta.2011...

Why not both?

Part of why dark matter is such an attractive explanation is because there are no constraints on it. Unfortunately this seems to have relieved pressure to explore and test modified gravity.

What do you mean there are “no constraints” on dark matter. There are plenty of constraints. I think you just have no idea what you are talking about.

For example, how much of it there can be or where it comes from. Contrast with Neutrinos.

But you are correct, I don't know what I am talking about which is why my comments were phrased in the form of a question or literally with the words "I don't understand"

how much of it there can be

Something like this?

https://chandra.harvard.edu/xray_astro/dark_energy/chart.jpg

Is that a chart of how much we think there is (model fitting based on observations) or how much we think there should be based on how it is created?

With Neutrinos we know how they are created and have a very good upper limit on how much there should be and it's not nearly enough to explain the observed effects. Same for the CMBR.

I'm not saying there couldn't be much more Dark matter/energy than neutrinos or photons but it's a bit too convenient to introduce a variable that is allowed to take any value and match it to observations without an explanation of what it is (besides having mass) or how it is created.

Calculations involving dark matter might as well be an experiment in curve fitting.

We won’t find dark matter in your or my lifetime, because it doesn’t exist. It is a convenient, flexible, and inelegant fudge factor.

A "kludge," if you will?

No, not really. We can observe it indirectly and have mapped out its structures. And intuitively, why do you find it implausible there is a massive particle that only interacts via gravitational force?

I think they mean that the theory of dark matter has an infinity of parameters. For every point in space, one can (rather arbitrarily) assign a mass of dark matter to make the theory fit observations.

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