I Is there a relationship between dark matter and anti-matter?

[Dade Murphy]

Hello,
I've been reading articles about the OGLE micro-lensing project, which started out looking to find dark matter as 'massive compact objects,' but now seems to have had more success finding exoplanets. Searching the forums here I couldn't find much recent discussion about theories of this sort, but a lot about the WIMP theory, which I understand is the most popular. Is it safe to say that the MACHOs theory is pretty well abandoned?

Thanks for your time,

 

[rootone]

As far as I know this theory is not as yet completely discounted, however the most recent observations of the contents of the Universe seem to suggest that there simply isn't enough density of invisible 'normal matter', such as neutron stars and brown dwarfs to account for dark matter phenomena.

 

[Chalnoth]

Hello,
I've been reading articles about the OGLE micro-lensing project, which started out looking to find dark matter as 'massive compact objects,' but now seems to have had more success finding exoplanets. Searching the forums here I couldn't find much recent discussion about theories of this sort, but a lot about the WIMP theory, which I understand is the most popular. Is it safe to say that the MACHOs theory is pretty well abandoned?

Thanks for your time,

Yes. CMB observations put the nail in that coffin, as the CMB was emitted before any compact objects would have formed, and the signature of dark matter in the CMB itself is very clear.

 

[rootone]

CMB observations put the nail in that coffin,

Ah, thanks for updating me on that, I didn't know that CMB had finally laid that one to rest.

 

[dirty dan]

isn't dark matter just reflective matter just anti matter?

 

[Nugatory]

isn't dark matter just reflective matter just anti matter?

No, antimatter is something completely different. It would be best to ask any followup questions in a new thread - but only after you've read some of the many dark-matter threads we already have.

 

[Chalnoth]

isn't dark matter just reflective matter just anti matter?

Anti-matter has all of the exact same properties of normal matter, except that its electric charge is opposite*. Dark matter has no electric charge at all, hence why it is dark. There's no reason to believe that normal matter and anti-matter are related in any sort of simple sense. There is surely a relationship between them, but chances are it's pretty complicated. It certainly involves physics we don't yet know.

* There's also a parity difference, but that is rarely relevant, and doesn't change the overall nature of the argument here.