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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 A lot of it's outdated, too; a part of me died when I found out quasars are no longer considered possible white holes.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 1170 Views
Cool, and true *NM* Stephen - 28/04/2011 11:46:29 AM 356 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 881 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 820 Views
I'm aware of the Bullet Cluster, though admittedly not much more than that. Joel - 29/04/2011 01:52:49 AM 762 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 860 Views
Re: I'm aware of the Bullet Cluster, though admittedly not much more than that. Joel - 30/04/2011 05:02:49 PM 794 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 691 Views
Re: I'm aware of the Bullet Cluster, though admittedly not much more than that. Joel - 02/05/2011 01:28:30 AM 724 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 822 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 898 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 742 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 695 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 774 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 700 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 772 Views
The Pati-Salam model was the one I had in mind. Joel - 24/05/2011 10:34:04 PM 715 Views
Re: The Pati-Salam model was the one I had in mind. Dreaded Anomaly - 24/05/2011 11:08:01 PM 933 Views
Re: The Pati-Salam model was the one I had in mind. Joel - 25/05/2011 01:27:10 AM 742 Views
Re: The Pati-Salam model was the one I had in mind. Dreaded Anomaly - 31/05/2011 09:16:18 AM 809 Views
Apologies for the delay; internet's been spotty and I've been busy lately. Joel - 10/06/2011 12:09:04 AM 1063 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 1057 Views
Also, re: lensing from ordinary matter: Dreaded Anomaly - 29/04/2011 05:18:47 AM 759 Views
This seems like another example of what confuses the issue. Joel - 30/04/2011 05:25:04 PM 880 Views
Re: This seems like another example of what confuses the issue. Dreaded Anomaly - 30/04/2011 08:56:40 PM 844 Views
That discussion seems to reduce to "as little new and exotic physics as possible". Joel - 02/05/2011 01:29:03 AM 843 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 806 Views
Re: That discussion seems to reduce to "as little new and exotic physics as possible". Joel - 07/05/2011 02:05:02 AM 974 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 744 Views
Re: That discussion seems to reduce to "as little new and exotic physics as possible". Joel - 14/05/2011 05:35:56 AM 1035 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 647 Views
Re: That discussion seems to reduce to "as little new and exotic physics as possible". Joel - 19/05/2011 02:47:25 AM 989 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 768 Views
Re: That discussion seems to reduce to "as little new and exotic physics as possible". Joel - 25/05/2011 12:20:10 AM 1064 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 871 Views
Re: That discussion seems to reduce to "as little new and exotic physics as possible". Joel - 10/06/2011 12:04:06 AM 1111 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 882 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 1063 Views
Seems to happen to me a lot; sorry. Joel - 29/04/2011 12:56:14 AM 741 Views
None of this reflects on the actual facts of dark matter. Dreaded Anomaly - 29/04/2011 01:32:52 AM 736 Views
I concede my grasp (or grope) is a somewhat superficial laymans, yes. Joel - 30/04/2011 04:30:28 PM 863 Views
Re: I concede my grasp (or grope) is a somewhat superficial laymans, yes. Dreaded Anomaly - 30/04/2011 08:56:44 PM 688 Views
Re: I concede my grasp (or grope) is a somewhat superficial laymans, yes. Joel - 02/05/2011 01:28:58 AM 1214 Views
Re: I concede my grasp (or grope) is a somewhat superficial laymans, yes. Dreaded Anomaly - 04/05/2011 04:18:27 AM 728 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 937 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 852 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 1035 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 760 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 1017 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 763 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 716 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 676 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 778 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 725 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 898 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 860 Views
Might help if you clarified where your skepticism is at Isaac - 29/04/2011 02:32:07 AM 703 Views
Potentially either, or a combination of the two. Joel - 30/04/2011 02:36:50 PM 774 Views
It's hard to discuss without knowing your objections a bit more clearly Isaac - 30/04/2011 04:58:03 PM 685 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 825 Views
Well, they weren't, not really sure how else to put that Isaac - 10/05/2011 03:19:57 AM 877 Views
Alright then, objection withdrawn (cautious skepticism intact). Joel - 14/05/2011 05:34:17 AM 986 Views
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