I don't really want to re-hash all my arguments against dark matter, but I don't think physics and astronomy have really dealt with the questions raised regarding the use of general relativity, rather than classical mechanics, for such issues as galactic formation and rotation.
Dark matter is remarkable for its invisibility--it neither absorbs nor emits light of any wavelength. We know about it through its gravitational action, the way it shaped galaxies, organized the largest objects in the Universe, and affected the spectrum of light from the early days of the cosmos. Based on the structure of galaxies, astronomers suspect it is made of particles. But how massive those particles are, how many types might exist, and how they interact are still matters of some conjecture.They don't know a damned thing about it, in other words. There are no candidates for it in the Standard Model and no place where it can possibly fit.
I've said it before: if you calculate the motion of a galaxy using relativity, everything lines up rather neatly and you don't need any exotic matter to explain it. The amazing thing about all this is that we've understood the mass-energy equivalence for over a hundred years, and people are still ignoring it because it makes the sums harder.
Look: a million tons of matter moving at a thousand kilometers a second, you don't really need relativity for that, because the relativistic mass of the thing is negligible compared to its classical mass. You're going way down into the decimals. But our galaxy is one and a half trillion solar masses. A solar mass is 2.2x10e27 tons, so our galaxy is about 3.3x10e39 tons of rest mass. What is the relativistic mass of 3.3x10e39 tons of mass moving at an average speed of 250 km/s around the center? How does that premium over the rest mass figure into the motion of stars around the galactic center?
I get that it's difficult to do the math. You have to track the orbits of over a hundred billion stars, plus an uncounted amount of dust and gas, and then do the sums for each star seperately. But if you do that, the result is unmistakable: the relativistic mass of the rest of the galaxy is enough to keep that particular star in the orbit it's in, around the galactic center, without handwavium.
The other issue here is that having dark matter then makes the universe too heavy. The expansion of the universe appears to be accelerating, so, they need dark energy to explain that. You can get dark energy from the standard model, but when you run those numbers the force comes out something like a hundred and thirty orders of magnitude too strong.
An error of that magnitude is like intending to put one molecule of salt on your dinner, and instead dropping Saturn on it. I'm not exaggerating; a difference of some hundred and thirty orders of magnitude is so large that when my starting point was "one grain of salt" I couldn't find an object large enough. Our sun only masses something like 10e27 tons. Multiply a 0.3 mg grain of salt by 10e130 and you end up with 10e121 tons of salt, which is much more than enough mass to form a black hole. About 10e90 times as much!
(And I may be misremembering. It might be 180 orders of magnitude. This does not help.)
Given that, it ought to be understood why I am slightly skeptical about dark anything.
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So, today is labor day.
I spent a lot of yesterday laying down. Not quite sleeping, just laying in bed and dozing. No big surprise, then, that I found myself unable to sleep at bedtime. I didn't end up going to bed until 4.
Today I need to--at a bare minimum--change the oil in Mrs. Fungus' car. I had planned to use the holiday weekend to do a lot more, but our trip to the mother-in-law's house on Saturday--combined with generalized fatigue and laziness--put paid to those plans.
Well, that's how it is, sometimes, and to be honest I'm not really all that upset with myself.
The thing that does annoy me, though, is that I've been intending to head over to a nearby used car lot to look over what they've got for pickups. When I drive past there I see some likely-looking vehicles which--if they are in as good a shape as they look from the road--might do just fine.
I keep thinking that if I were to replace the Jeep, there are three basic things I want: four-wheel drive, the ability to tow trailers, and some reasonable cargo capacity. I've got all that with the Jeep, and those are the things I do not care to be without. I've also got a strong preference for a vehicle which is not front wheel drive when in 2WD mode, though to be honest that's not really as important; it's a matter of taste. I'd give that up for the right vehicle at the right price.
One reason that pickup trucks cost so much stems from the fact that they're durable. They just go, much longer than cars do, because of how they're built. I got my Jeep with 81k on the clock and it's now at 220k, and the only reason I'm considering replacement stems from all the damned rust that's cropped up. A rust-free Chevy or Ford pickup, even with 100k on the clock, would not be a bad investment; the small block V8s endemic to those trucks don't fail, unless they're sorely abused.
I happened to see--at the place from which I bought the Jeep--a nice possibility. It's one I was really interested in, at least until I saw the price. Excellent condition, an older Ranger pickup, 4WD, extended cab, about 70k on it...and it's eleven thousand dollars. Looks like it's in pristine shape but it's older than the Jeep is. And, the 4-liter V6 that Ford put into just about everything, but which was problematic, at least in its front wheel drive configuration.
But a full-size pickup with a crew cab wouldn't be too much, I don't think. Again, it's a question of finding the right one. I don't think I can score anything like the Cherokee a second time (where I pay a relative pittance for the thing and then drive it for more than a decade) not the least because no one makes anything with that bulletproof straight six any longer.
Nonetheless, I am confident that at the right time, the right vehicle will come along, so I'm not very worried about it.
* * *
Anyway, late to bed, and I'm still sleepy, and Mrs. Fungus is still in bed. Guess what that means for me?