Detecting dark matter

Steve Willner wrote in message
...
In article ,
Joseph Lazio writes:
It's also worth pointing out that we need dark matter to exist because
we've detected some. Both neutrinos and black holes are dark matter.
Neither exist in a sufficient quantity to explain all of the dark
matter required, but both exist. If we have two examples of dark
matter, it is not unreasonable to suggest that there might be a third
example of dark matter.

It's perhaps worth pointing out that planets, white dwarfs, brown
dwarfs, neutron stars, and even low mass stars "count" as dark matter
in the context of galaxy rotation curves and cluster velocity
dispersions. (Not to mention asteroids and cannon balls, and it
wouldn't surprise me if there are others I've omitted.) All that is
required to be "dark matter" is that the ratio of mass to luminosity,
measured in solar units, be much greater than one.

No, they don't "count" as dark matter, because their presence has already
been "counted" in the big bang cosmology as normal matter.

greywolf42
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