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Re: That discussion seems to reduce to "as little new and exotic physics as possible". Dreaded Anomaly Send a noteboard - 17/05/2011 02:09:55 AM
Not a complete lack, but nothing like a professionals, no. A lot of it's outdated, too; a part of me died when I found out quasars are no longer considered possible white holes. I know fusion isn't restricted to hydrogen (else helium would be the heaviest element), but fuzing say, transuranides, seems energy prohibitive. I'm curious how cosmic background radiation has ruled out the possibility of heavy nuclei pockets surrounding galaxies; I'd have thought scattering over such a great distance would make detection of all but the most massive quantity of super heavy nuclei impossible, but presumably that's not the basis on which the exclusion was made.


Measurements of the cosmic microwave background constrain how much normal (baryonic) matter there is in the universe. We can see much of that matter in the form of light elements in stars, and we can make further observations to estimate the amounts of heavier elements that have been produced. The numbers just don't work out.

That last statement doesn't follow from the others. Far away lensing is consistent with exotic dark matter, but no less consistent with MACHOs; MACHOs were ruled out because no nearby gravitational lensing was observed and galactic rotation says dark matter is uniformly distributed within galaxies. That works if there's enough dark matter to significantly affect galactic rotation but not enough to create nearby gravitational lensing, but those two propositions tend to be contradictory unless there's a BIG difference between the amount of dark matter necessary for the former and the latter. If that's the case I have no objection, I just want to be sure that's what you're saying.


Far away lensing is not consistent with MACHOs. Go read Sean Carroll's blog post a few more times.

Lensing happens when there's a concentrated source of matter between the observer and the object; for dark matter that's distributed fairly homogeneously within the galaxy, that's very unlikely to happen. When we look at lensing from entire clusters of far-away galaxies, we get results that match exotic matter expectations, but not ordinary matter expectations.

Hopefully not, but that demonstrates that my concern that kind of thinking didn't end in the 1600s is valid. I don't doubt it's less likely, and significantly, but it's far from impossible, particularly if we allow ourselves the luxury of thinking it impossible; that's actually an EXAMPLE of the kind of erroneous and overconfident thinking that worries me, and further demonstrates it can still occur, because it manifestly has.


You're conflating "simply doesn't occur as often" with "impossible." I did not use the latter term.

It could also be a form of normal matter acting in ways existing theory didn't anticipate, which is not so far fetched since existing theories obviously failed to anticipate SOMETHING or we wouldn't be seeking a way to reconcile them with recent anomalous observations. You've convinced me exotic dark matter is the best candidate, but I'd still like to be certain it's not prematurely designated the ONLY candidate.


That suggestion seems to boil down to MOND or something similar, and as many sources will describe for you, such modified theories do not work well.

Exotic dark matter is the most likely candidate. My statements have all been, explicitly or implicitly, in terms of probabilities which are based on evidence and will be updated when more evidence is available. This is the correct way to reason about empirical issues. Your qualitative, rhetorical style is causing you to blow things out of proportion.
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Exciting video about the universe Camilla - 28/04/2011 10:14:55 AM 1180 Views
Cool, and true *NM* Stephen - 28/04/2011 11:46:29 AM 360 Views
I still think dark matter's just non-luminous matter without a convenient light source to reflect. Joel - 28/04/2011 10:34:21 PM 892 Views
We've just about ruled out the idea that dark matter is just non-luminous "ordinary" matter. Dreaded Anomaly - 28/04/2011 11:44:34 PM 831 Views
I'm aware of the Bullet Cluster, though admittedly not much more than that. Joel - 29/04/2011 01:52:49 AM 771 Views
Re: I'm aware of the Bullet Cluster, though admittedly not much more than that. Dreaded Anomaly - 29/04/2011 02:56:32 AM 870 Views
Re: I'm aware of the Bullet Cluster, though admittedly not much more than that. Joel - 30/04/2011 05:02:49 PM 803 Views
Re: I'm aware of the Bullet Cluster, though admittedly not much more than that. Dreaded Anomaly - 30/04/2011 08:56:35 PM 701 Views
Re: I'm aware of the Bullet Cluster, though admittedly not much more than that. Joel - 02/05/2011 01:28:30 AM 736 Views
Re: I'm aware of the Bullet Cluster, though admittedly not much more than that. Dreaded Anomaly - 04/05/2011 04:18:18 AM 831 Views
There's such a thing as knowing when you're licked, and I believe I am. Joel - 07/05/2011 02:04:53 AM 909 Views
Re: There's such a thing as knowing when you're licked, and I believe I am. Dreaded Anomaly - 09/05/2011 11:28:48 PM 755 Views
Re: There's such a thing as knowing when you're licked, and I believe I am. Joel - 14/05/2011 05:36:45 AM 705 Views
Re: There's such a thing as knowing when you're licked, and I believe I am. Dreaded Anomaly - 17/05/2011 02:09:40 AM 784 Views
Re: There's such a thing as knowing when you're licked, and I believe I am. Joel - 19/05/2011 04:55:21 AM 711 Views
Re: There's such a thing as knowing when you're licked, and I believe I am. Dreaded Anomaly - 24/05/2011 09:32:27 PM 782 Views
The Pati-Salam model was the one I had in mind. Joel - 24/05/2011 10:34:04 PM 724 Views
Re: The Pati-Salam model was the one I had in mind. Dreaded Anomaly - 24/05/2011 11:08:01 PM 942 Views
Re: The Pati-Salam model was the one I had in mind. Joel - 25/05/2011 01:27:10 AM 751 Views
Re: The Pati-Salam model was the one I had in mind. Dreaded Anomaly - 31/05/2011 09:16:18 AM 819 Views
Apologies for the delay; internet's been spotty and I've been busy lately. Joel - 10/06/2011 12:09:04 AM 1072 Views
Re: Apologies for the delay; internet's been spotty and I've been busy lately. Dreaded Anomaly - 14/06/2011 03:38:18 AM 1066 Views
Also, re: lensing from ordinary matter: Dreaded Anomaly - 29/04/2011 05:18:47 AM 771 Views
This seems like another example of what confuses the issue. Joel - 30/04/2011 05:25:04 PM 890 Views
Re: This seems like another example of what confuses the issue. Dreaded Anomaly - 30/04/2011 08:56:40 PM 857 Views
That discussion seems to reduce to "as little new and exotic physics as possible". Joel - 02/05/2011 01:29:03 AM 849 Views
Re: That discussion seems to reduce to "as little new and exotic physics as possible". Dreaded Anomaly - 04/05/2011 04:18:24 AM 815 Views
Re: That discussion seems to reduce to "as little new and exotic physics as possible". Joel - 07/05/2011 02:05:02 AM 984 Views
Re: That discussion seems to reduce to "as little new and exotic physics as possible". Dreaded Anomaly - 09/05/2011 11:29:36 PM 755 Views
Re: That discussion seems to reduce to "as little new and exotic physics as possible". Joel - 14/05/2011 05:35:56 AM 1043 Views
Re: That discussion seems to reduce to "as little new and exotic physics as possible". Dreaded Anomaly - 17/05/2011 02:09:55 AM 654 Views
Re: That discussion seems to reduce to "as little new and exotic physics as possible". Joel - 19/05/2011 02:47:25 AM 1000 Views
Re: That discussion seems to reduce to "as little new and exotic physics as possible". Dreaded Anomaly - 24/05/2011 09:46:30 PM 778 Views
Re: That discussion seems to reduce to "as little new and exotic physics as possible". Joel - 25/05/2011 12:20:10 AM 1076 Views
Re: That discussion seems to reduce to "as little new and exotic physics as possible". Dreaded Anomaly - 31/05/2011 09:16:22 AM 885 Views
Re: That discussion seems to reduce to "as little new and exotic physics as possible". Joel - 10/06/2011 12:04:06 AM 1122 Views
Re: That discussion seems to reduce to "as little new and exotic physics as possible". Dreaded Anomaly - 14/06/2011 03:38:12 AM 893 Views
Re: I still think... (apparently, there is a 100 character limit on subjects, and yours was 99) Tor - 28/04/2011 11:57:15 PM 1074 Views
Seems to happen to me a lot; sorry. Joel - 29/04/2011 12:56:14 AM 750 Views
None of this reflects on the actual facts of dark matter. Dreaded Anomaly - 29/04/2011 01:32:52 AM 749 Views
I concede my grasp (or grope) is a somewhat superficial laymans, yes. Joel - 30/04/2011 04:30:28 PM 877 Views
Re: I concede my grasp (or grope) is a somewhat superficial laymans, yes. Dreaded Anomaly - 30/04/2011 08:56:44 PM 699 Views
Re: I concede my grasp (or grope) is a somewhat superficial laymans, yes. Joel - 02/05/2011 01:28:58 AM 1225 Views
Re: I concede my grasp (or grope) is a somewhat superficial laymans, yes. Dreaded Anomaly - 04/05/2011 04:18:27 AM 737 Views
I don't object to changing my mind, but can take more convincing than I really should. Joel - 07/05/2011 02:05:09 AM 950 Views
Re: I don't object to changing my mind, but can take more convincing than I really should. Dreaded Anomaly - 09/05/2011 11:32:17 PM 861 Views
Re: I don't object to changing my mind, but can take more convincing than I really should. Joel - 14/05/2011 05:36:24 AM 1044 Views
Re: I don't object to changing my mind, but can take more convincing than I really should. Dreaded Anomaly - 17/05/2011 02:10:03 AM 771 Views
Re: I don't object to changing my mind, but can take more convincing than I really should. Joel - 19/05/2011 04:33:06 AM 1027 Views
Re: I don't object to changing my mind, but can take more convincing than I really should. Dreaded Anomaly - 24/05/2011 09:59:38 PM 771 Views
Re: I don't object to changing my mind, but can take more convincing than I really should. Joel - 24/05/2011 11:19:43 PM 726 Views
Re: I don't object to changing my mind, but can take more convincing than I really should. Dreaded Anomaly - 24/05/2011 11:33:58 PM 684 Views
Re: I don't object to changing my mind, but can take more convincing than I really should. Joel - 25/05/2011 12:55:36 AM 787 Views
Re: I don't object to changing my mind, but can take more convincing than I really should. Dreaded Anomaly - 31/05/2011 09:16:24 AM 737 Views
Re: I don't object to changing my mind, but can take more convincing than I really should. Joel - 10/06/2011 12:09:13 AM 909 Views
Re: I don't object to changing my mind, but can take more convincing than I really should. Dreaded Anomaly - 14/06/2011 03:38:05 AM 871 Views
Might help if you clarified where your skepticism is at Isaac - 29/04/2011 02:32:07 AM 714 Views
Potentially either, or a combination of the two. Joel - 30/04/2011 02:36:50 PM 783 Views
It's hard to discuss without knowing your objections a bit more clearly Isaac - 30/04/2011 04:58:03 PM 694 Views
My primary objection is that alternatives to dark matter seem to have been ruled out prematurely. Joel - 02/05/2011 01:29:14 AM 846 Views
Well, they weren't, not really sure how else to put that Isaac - 10/05/2011 03:19:57 AM 891 Views
Alright then, objection withdrawn (cautious skepticism intact). Joel - 14/05/2011 05:34:17 AM 1002 Views
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