"GD" == George Dishman writes:

GD "Joseph Lazio" wrote in message
GD ...
For the record, dark matter is not a theory. Dark matter is a
hypothesis to account for various discrepancies between theory and
observation.

If one assumes that general relativity is the correct theory to
describe gravity[1], then various observations indicate that there
is far more matter around than we detect via emission of photons.
So one has two options:

1. There is dark matter, matter that is either too faint for us to
detect or in some cases that is hypothesized not to emit photons at
all.

2. General relativity is not an accurate description of gravity.

Of course, there could also be a third option, both of the above are
correct.

GD There has just been a short series of programmes on UK TV on
GD string theory, based on Brian Greene's "Elegant Universe", and
GD discussing the hypothesis that gravity is weaker than other forces
GD because it 'leaks' between branes. Is there consideration given to
GD the apparent discrepancy being due to the converse, a leakage of a
GD gravitational effect into our brane from others?

To the extent that I understand this notion, I don't think so. The
hypothesis is that gravity is weaker than the other forces is based on
the notion that gravity operates on all branes, while the other forces
are confined to our brane. I suppose one might ask whether there is
some "fifth force," similar to gravity that extends across all branes
but is sufficiently weak that we have not yet discovered it. I don't
know enough about string theory to know whether it makes any such
predictions.

--
Lt. Lazio, HTML police | e-mail:
No means no, stop rape. | http://patriot.net/%7Ejlazio/
sci.astro FAQ at http://sciastro.astronomy.net/sci.astro.html