Lawrence B. Crowell
- 190
- 2
On the galactic scale there are issues of dark matter and the like. For a mass embedded in a gravitating media with density \rho the gravitation acts as
<br /> {\vec F}~=~-GM\rho{\vec r},<br />
and so its motion is a particle on a spring moving in the plane. This is one reason stars move with about the same orbital frequency across a galaxy. The "stuff" which does this is labelled dark matter. Einstein lensing have pretty much indicated it exists, in particular with the recent Bullet galaxy measurements. So how a Brans-Dicke type of modified gravity fits into this is hard to cypher.
Lawrence B. Crowell
<br /> {\vec F}~=~-GM\rho{\vec r},<br />
and so its motion is a particle on a spring moving in the plane. This is one reason stars move with about the same orbital frequency across a galaxy. The "stuff" which does this is labelled dark matter. Einstein lensing have pretty much indicated it exists, in particular with the recent Bullet galaxy measurements. So how a Brans-Dicke type of modified gravity fits into this is hard to cypher.
Lawrence B. Crowell
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