[ExI] Dark matter

Anders Sandberg anders at aleph.se
Wed Feb 20 00:07:04 UTC 2013

On 20/02/2013 00:54, Adrian Tymes wrote:
> Right, but all these strange explanations keep getting offered and 
> talked about, and the simple solution does not seem to be getting much 
> consideration.

It was, way back in the 90s. Check out any astrophysics textbook that 
has some historical detail.

Rotation curves are pretty good evidence. They reveal not just the 
presence of dark matter inside the galaxy, but around it in a halo (as 
evidenced by velocities of orbiting satellite galaxies and clusters). 
Now if that had been opaque stuff you would not have seen the galaxy. If 
it had been pointlike objects (like loads of of brown dwarves) you would 
have seen occultations and gravity lensing - but the MACHO searches 
turned up nothing.

Remember that explanations on a list for the educated public is not the 
same thing as a proper review paper.

Anders Sandberg,
Future of Humanity Institute
Philosophy Faculty of Oxford University

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