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I don’t think that’s quite fair. That approach is exactly how we find planets. Here’s an unexpected variance in the motion of a planet or star. It could be expl
by simonh 2y ago
I don’t think that’s quite fair. That approach is exactly how we find planets. Here’s an unexpected variance in the motion of a planet or star. It could be explained by a planet over there. Oh look, there’s a planet over there.
- russdill 2y agoIt's actually a better example than you think. This exact theory led to long and protracted searches for the planet Vulcan, which would explain Mercury's strange behavior.
- TheOtherHobbes 2y agoPlanets are visible when you look for them. Dark matter - so far - isn't.
- drdeca 2y agoWhat do you mean by “visible when you look for them”? Like, with light? Does gravitational lensing count as “visible” to you?
- MarkusQ 2y agoRight, which is why it quickly led to the detection of dark matter...hmm. I think a better analogy would be "that approach is exactly how we explain failing to find planets like Vulcan; we hypothesize that they are made of as-yet-unknown stuff that you can't see, touch, hear, smell, or in fact detect at all. But we know they're there because our calculations say they are."
- solid_fuel 2y agoHypothesizing that a planet might be over there is a testable hypothesis. Have we found a way to verify the presence of dark matter yet? Or is it still an untestable hypothesis sprinkled around distant galaxies so their acceleration curves look right?
- User23 2y agoI’m particularly amused by the hypothesis that spacetime can be bent without the presence of matter. We can’t detect dark matter because there’s no such thing, it’s just a brute topological fact.
- mr_mitm 2y agoDark matter predicted lensing effect which were successfully tested. Same for the baryonic acoustic oscillations in the CMB.
- MattPalmer1086 2y agoThat's not quite true. General relativity predicts gravitational lensing, not dark matter. Lensing has been used as an experimental probe for the presence of dark matter.
- elashri 2y agoMOND is an alternative theory of gravity competing with GR. People usually forget that while MOND started to present a different explanation for Dark Matter, it is a theory of gravity. Dark Matter is not a theory of gravity and is compatible with GR.
- zeroonetwothree 2y agoDark matter isn’t much of a theory in the first place.
- mr_mitm 2y agoWell of course. What I clearly meant was that DM predicts lensing effects in a magnitude that cannot be explained with ordinary matter. See bullet cluster or weak lensing observations.