Every once in a while I poke my head back in to one of the neverending Zeuzzz threads. Usually I pop right back out, but Zeuzzz has just said something very important:
That post from Tim was a good post. But I feel he is still dodging the elephant in the room. You can use literature in astronomy to imply many different things in the context of which theory you are viewing it through.
This is, in a sense, the purest statement of crackpotty denialism. Sure, Zeuzzz says, you look at The Bullet Cluster and interpret it as evidence of dark matter, but I can look at it and interpret it as evidence of a double-layer Z-pinched plasmoid helix! Pick a different theory and you get a different interpretation, right?
No, you don't. That's what you get if you are an
incompetent dorm-room philosopher. Democritus says matter is atomic! Parmenides says change is an illusion! They disagree! Welp, we don't know any relevant or discriminating details, and I only photocopied the first five pages of the course packet! I guess this will continue to be a topic for meaningless opinionizing! Great!
Here in real life, the Bullet Cluster and MACS J0025.4-1222 (whose discoverers are friends of mine) have
actual, relevant data. There is a hypothesis about them---"they're colliding galaxy clusters containing dark matter, galaxies, and gas"---which actually makes sense in excruciating detail. There are a stack of alternative hypotheses---including "they're galaxy clusters without cold dark matter", "they're not actually colliding", "they're galaxy clusters with interacting warm dark matter", to name a few---which can be studied in detail and
ruled out. This is clear in the data, it's clear in the primary literature, it's clear in the secondary literature, it's clear in the tertiary literature, and it's clear in the literature written by
people actively trying to forge non-dark-matter explanations.
And then there's Zeuzzzology. Zeuzzzology looks at the Bullet Cluster literature, settles deeper into its dorm-room beanbag, and says "Dude, doesn't Parmenides say motion is impossible? Doesn't Democritus say the void is like one hand clapping? Doesn't Alfven say the universe is 99% plasma?
They disagree! Welp, I don't know any relevant or discriminating details, so this will continue to be a topic for meaningless opinionizing! Great!
Or, in another sense, Zeuzzz is right. You can read the literature using different assumptions and reach different conclusions. For example, you can use the "science" paradigm or the "crackpot trolling" paradigm.
Within the paradigm of "let's apply laws of physics and see whether they work", you reach one conclusion, which turns out to include the implication of dark matter or modified gravity. Within the paradigm of "Let's look at a picture, compare it to pictures in Alfven's papers, and seek out confirmatory-sounding Google search summaries" technique, you can conclude that the Bullet Cluster is a coffee stain on Hubble's CCD. Or a voltaic pile. Or ball lightning.
Two paradigms disagree, dude! Whoa! My mind is so blown I can't even get out of this beanbag. Dark matter! Plasma! Woooooo! It's like that Schwarzenegger movie where you still don't know at the end! My Heidigger TA says that ... um, I forget. What if it's like, dark plasma? Or, or, or, or, or, get this, matter plasma?
:
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