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I think you misread. Sabine is arguing that maybe dark matter is just the error term in our approximations of real matter, and pointing out that no one yet has

I think you misread. Sabine is arguing that maybe dark matter is just the error term in our approximations of real matter, and pointing out that no one yet has actually taken the time to disprove that Occam's Razor theory.

philwelch 7y ago
I wouldn't presume to argue against her, because she's a physicist and I'm not. I'm mostly making the case to the peanut gallery here to maintain a state of epistemic noncommittal. It's a very popular intuition to think that "dark matter" is just a weird consequence of modeling things improperly, kind of like how we used to think there was another planet between Mercury and the sun because that was the only way to make Mercury's orbit consistent with Newtonian dynamics. If we are modeling things improperly, I suspect it would have to be a pretty weird bug--and I think the one she's suggesting qualifies as such.
mirimir 7y ago
Yes, and she says it quite clearly: > Now, what we do when we want to explain what a galaxy does, or a galaxy cluster, or even the whole universe, is not to plug the matter and energy of every single planet and star into the equations. This would be computationally unfeasible. Instead, we use an average of matter and energy, and use that as the source for gravity. > Needless to say, taking an average on one side of the equation requires that you also take an average on the other side. But since the gravitational part is non-linear, this will not give you the same equations that we use for the solar system: The average of a function of a variable is not the same as the function of the average of the variable. We know it’s not. But whenever we use general relativity on large scales, we assume that this is the case. > So, we know that strictly speaking the equations we use are wrong. The big question is, then, just how wrong are they? [emphasis added] It's not a "hunch". It's just how the math works. average of 0-9 = 4.5 4.5^2 = 20.25 average of squares of 0-9 = 28.5
andbberger 7y ago
Thanks for this, that is the best summary I have seen yet in this thread.

philwelch 7y ago

I wouldn't presume to argue against her, because she's a physicist and I'm not. I'm mostly making the case to the peanut gallery here to maintain a state of epistemic noncommittal. It's a very popular intuition to think that "dark matter" is just a weird consequence of modeling things improperly, kind of like how we used to think there was another planet between Mercury and the sun because that was the only way to make Mercury's orbit consistent with Newtonian dynamics. If we are modeling things improperly, I suspect it would have to be a pretty weird bug--and I think the one she's suggesting qualifies as such.

mirimir 7y ago

Yes, and she says it quite clearly: > Now, what we do when we want to explain what a galaxy does, or a galaxy cluster, or even the whole universe, is not to plug the matter and energy of every single planet and star into the equations. This would be computationally unfeasible. Instead, we use an average of matter and energy, and use that as the source for gravity. > Needless to say, taking an average on one side of the equation requires that you also take an average on the other side. But since the gravitational part is non-linear, this will not give you the same equations that we use for the solar system: The average of a function of a variable is not the same as the function of the average of the variable. We know it’s not. But whenever we use general relativity on large scales, we assume that this is the case. > So, we know that strictly speaking the equations we use are wrong. The big question is, then, just how wrong are they? [emphasis added] It's not a "hunch". It's just how the math works. average of 0-9 = 4.5 4.5^2 = 20.25 average of squares of 0-9 = 28.5

andbberger 7y ago

Thanks for this, that is the best summary I have seen yet in this thread.