Hmmm, just thinking about the dark matter problem...

As I understand it, theorists came to think that dark matter must
exist due to calculations that showed the amount of observable "stuff"
wasn't enough to explain the various characteristics they were
measuring.

It takes time for the light to get here, so 10 billion light-years
away, anything younger than 10 billion years is invisible to us.

Could it be that we just cannot see the ordinary "stuff" that is
affecting the universe, because it is too young _and_ too far away?

wrote in message
...
As I understand it, theorists came to think that dark matter must
exist due to calculations that showed the amount of observable "stuff"
wasn't enough to explain the various characteristics they were
measuring.

It takes time for the light to get here, so 10 billion light-years
away, anything younger than 10 billion years is invisible to us.

Could it be that we just cannot see the ordinary "stuff" that is
affecting the universe, because it is too young _and_ too far away?

Nope. First, according to theory gravity propagates at
the speed of light too. Second, a uniform shell of matter
has no net gravitational effect on the inside of it.

On Mon, 26 Feb 2007 17:22:42 GMT, wrote:

As I understand it, theorists came to think that dark matter must
exist due to calculations that showed the amount of observable "stuff"
wasn't enough to explain the various characteristics they were
measuring.

It takes time for the light to get here, so 10 billion light-years
away, anything younger than 10 billion years is invisible to us.

Could it be that we just cannot see the ordinary "stuff" that is
affecting the universe, because it is too young _and_ too far away?

We see it affecting stuff fairly close to us, like nearby galaxies. The
evidence suggests it is all around us.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

"Chris L Peterson" wrote in message
...
On Mon, 26 Feb 2007 17:22:42 GMT, wrote:

As I understand it, theorists came to think that dark matter must
exist due to calculations that showed the amount of observable "stuff"
wasn't enough to explain the various characteristics they were
measuring.

It takes time for the light to get here, so 10 billion light-years
away, anything younger than 10 billion years is invisible to us.

Could it be that we just cannot see the ordinary "stuff" that is
affecting the universe, because it is too young _and_ too far away?

We see it affecting stuff fairly close to us, like nearby galaxies. The
evidence suggests it is all around us.

How about a wacky theory that it coexists in the same spacetime as the
regular matter we can see, but is actually in different dimensions to the
traditional ones we are able to see and measure (perhaps curles up at
sub-Plank lengths), and that gravity is the only force that crosses those
dimensional boundaries - and so the gravitational effects are all we are
able to detect? i.e. dark matter is part of the totality of "regular" matter
but we are in effect only able to measure a subset of what matter is ?

(The other component to my wacky theory is that strings have to exist in all
possible dimensions and their mode of "vibration" in each subset of
dimensions determines what particles they are detected as)

I'll get my coat....