Wasn't it Erik Max Francis who wrote:
>Mike Williams wrote:
>
>> My crackpot theory is that dark matter is just normal matter that's
>>outside the brane in which our universe resides. Brane theory suggests
>>that gravity is weak because gravitons can travel in all directions,
>>whereas other force carriers can't travel outside the brane. Objects
>>in our universe feel the gravity from massive objects in nearby
>>branes, but don't feel any other forces from them since the other
>>force carriers are trapped in their branes. The dark matter appears
>>fuzzy because the separation between the branes is the equivalent of
>>several thousand light years.
>
>Doesn't seem like this would have worked, anyway. First, such a
>distance would be hard to explain the profound effects we see,
>considering that our estimates are that dark matter is something like
>90% of the matter in our Universe. Second, it wouldn't explain the
>halo distribution of dark matter we've introduced to explain galactic
>rotation curves.
>
>You'd have to explain why the effect is as strong as it is, as well as
>why it has a distribution that correlates with strongly with haloes
>around galaxies. I'm not really seeing how a nearby brane could do that.
Yes. I didn't put all the details in that post.
1. There's more than one nearby brane. The sum of the gravity from
several branes adds up to several times the gravity from the mass in our
own universe.
2. Gravity acts between branes. So matter in one brane is attracted by
matter in an adjacent brane. A galaxy in brane 2 tends to form in the
same place as a galaxy in brane 1 because material is caught in the
gravity well of the brane 1 galaxy. What we consider to be a galaxy in
our universe is just one slice through a collection of material that is
gravitationally bound together across several branes.
3. If the nearest brane is the equivalent of tens of thousands of light
years away, then the pull from the core of its galaxy appears to be
spread out across a region the size of a galactic halo.
4. It's a crackpot theory anyway. I don't really expect it to explain
everything. It does, however, make falsifiable predictions. It predicts
that you'll never be able to observe any small clumps of dark matter,
because of the effect of the previous point. It predicts that dark
matter doesn't interact with the weak nuclear force.
--
Mike Williams
Gentleman of Leisure
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