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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 A lot of it's outdated, too; a part of me died when I found out quasars are no longer considered possible white holes.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 1349 Views
Cool, and true *NM* Stephen - 28/04/2011 11:46:29 AM 476 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 1071 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 1007 Views
I'm aware of the Bullet Cluster, though admittedly not much more than that. Joel - 29/04/2011 01:52:49 AM 921 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 1035 Views
Re: I'm aware of the Bullet Cluster, though admittedly not much more than that. Joel - 30/04/2011 05:02:49 PM 967 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 923 Views
Re: I'm aware of the Bullet Cluster, though admittedly not much more than that. Joel - 02/05/2011 01:28:30 AM 897 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 978 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 1075 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 903 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 872 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 944 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 876 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 949 Views
The Pati-Salam model was the one I had in mind. Joel - 24/05/2011 10:34:04 PM 898 Views
Re: The Pati-Salam model was the one I had in mind. Dreaded Anomaly - 24/05/2011 11:08:01 PM 1120 Views
Re: The Pati-Salam model was the one I had in mind. Joel - 25/05/2011 01:27:10 AM 917 Views
Re: The Pati-Salam model was the one I had in mind. Dreaded Anomaly - 31/05/2011 09:16:18 AM 985 Views
Apologies for the delay; internet's been spotty and I've been busy lately. Joel - 10/06/2011 12:09:04 AM 1246 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 1237 Views
Also, re: lensing from ordinary matter: Dreaded Anomaly - 29/04/2011 05:18:47 AM 924 Views
This seems like another example of what confuses the issue. Joel - 30/04/2011 05:25:04 PM 1054 Views
Re: This seems like another example of what confuses the issue. Dreaded Anomaly - 30/04/2011 08:56:40 PM 1019 Views
That discussion seems to reduce to "as little new and exotic physics as possible". Joel - 02/05/2011 01:29:03 AM 1007 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 962 Views
Re: That discussion seems to reduce to "as little new and exotic physics as possible". Joel - 07/05/2011 02:05:02 AM 1154 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 928 Views
Re: That discussion seems to reduce to "as little new and exotic physics as possible". Joel - 14/05/2011 05:35:56 AM 1217 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 813 Views
Re: That discussion seems to reduce to "as little new and exotic physics as possible". Joel - 19/05/2011 02:47:25 AM 1170 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 937 Views
Re: That discussion seems to reduce to "as little new and exotic physics as possible". Joel - 25/05/2011 12:20:10 AM 1251 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 1088 Views
Re: That discussion seems to reduce to "as little new and exotic physics as possible". Joel - 10/06/2011 12:04:06 AM 1308 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 1048 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 1378 Views
Seems to happen to me a lot; sorry. Joel - 29/04/2011 12:56:14 AM 916 Views
None of this reflects on the actual facts of dark matter. Dreaded Anomaly - 29/04/2011 01:32:52 AM 935 Views
I concede my grasp (or grope) is a somewhat superficial laymans, yes. Joel - 30/04/2011 04:30:28 PM 1066 Views
Re: I concede my grasp (or grope) is a somewhat superficial laymans, yes. Dreaded Anomaly - 30/04/2011 08:56:44 PM 879 Views
Re: I concede my grasp (or grope) is a somewhat superficial laymans, yes. Joel - 02/05/2011 01:28:58 AM 1405 Views
Re: I concede my grasp (or grope) is a somewhat superficial laymans, yes. Dreaded Anomaly - 04/05/2011 04:18:27 AM 890 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 1136 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 1017 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 1231 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 942 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 1216 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 937 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 897 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 858 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 955 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 902 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 1089 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 1062 Views
Might help if you clarified where your skepticism is at Isaac - 29/04/2011 02:32:07 AM 879 Views
Potentially either, or a combination of the two. Joel - 30/04/2011 02:36:50 PM 950 Views
It's hard to discuss without knowing your objections a bit more clearly Isaac - 30/04/2011 04:58:03 PM 866 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 1057 Views
Well, they weren't, not really sure how else to put that Isaac - 10/05/2011 03:19:57 AM 1065 Views
Alright then, objection withdrawn (cautious skepticism intact). Joel - 14/05/2011 05:34:17 AM 1188 Views
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