Earth: Planet Designed For Science

"Wilson Heydt" wrote in message
...
....
I've been following this discussion without commenting (until now)....

As understand from what what little bits of string theory I've followed,
one of the problesm that theory faces is that it can describe some 10**120
different universes, and so far the tools to determine *which* solution
to the equtions give our universe don't exist. The suggestion from that
theory is that there as (potentially) 10**120 universes, of which our is
just one. The flip side of this is that the only thing "special" about
this universe is
that we happen to live in it.

On the whole, if the constants that describe our universe were different
enough so
that life could not exist here, we wouldn't be here wondering about it.
This is
an agrument that I have traditionally described as "looking through the
wrong
end of the telescope." It's not that the universe is constructed for us
to be
possible, but rather, out of all possible universes we exist here because
we can.

It is commonly known as the "anthropic principle".

http://en.wikipedia.org/wiki/Anthropic_principle

If there are multiple universes then the weak anthropic
principle applies and tell us little. Have a look at
section 5 of:

http://www.arxiv.org/abs/astro-ph/0301199

If there is only a single universe then the strong
anthropic principle might apply, or the range of
parameters and laws which are possible for a universe
is limited and we were lucky, or the values of the
parameters are fully constrained by the physics of
the event we call the big bang that we have not yet
understood, and those values just happen to allow for
life to evolve.

At this stage, it is certainly nothing more than
speculation to try to rule out any of those, and the
reality may well be none of the above.

George

"George Dishman" wrote in message
...

"Wilson Heydt" wrote in message
...
...
I've been following this discussion without commenting (until now)....

As understand from what what little bits of string theory I've followed,
one of the problesm that theory faces is that it can describe some
10**120
different universes, and so far the tools to determine *which* solution
to the equtions give our universe don't exist. The suggestion from that
theory is that there as (potentially) 10**120 universes, of which our is
just one. The flip side of this is that the only thing "special" about
this universe is
that we happen to live in it.

On the whole, if the constants that describe our universe were different
enough so
that life could not exist here, we wouldn't be here wondering about it.
This is
an agrument that I have traditionally described as "looking through the
wrong
end of the telescope." It's not that the universe is constructed for us
to be
possible, but rather, out of all possible universes we exist here
because
we can.

It is commonly known as the "anthropic principle".

http://en.wikipedia.org/wiki/Anthropic_principle

If there are multiple universes then the weak anthropic
principle applies and tell us little.

Only if the multiple universes have different physical constants. Multiple
universes with the same values wouldn't explain anything.


J/

BOTW: "Barchester Towers" - Antony Trollope

"Westprog" wrote in message
...

"George Dishman" wrote in message
...

"Wilson Heydt" wrote in message
...
...
I've been following this discussion without commenting (until now)....

As understand from what what little bits of string theory I've
followed,
one of the problesm that theory faces is that it can describe some
10**120
different universes, and so far the tools to determine *which* solution
to the equtions give our universe don't exist. The suggestion from
that
theory is that there as (potentially) 10**120 universes, of which our
is
just one. The flip side of this is that the only thing "special" about
this universe is
that we happen to live in it.

On the whole, if the constants that describe our universe were
different enough so
that life could not exist here, we wouldn't be here wondering about it.
This is
an agrument that I have traditionally described as "looking through the
wrong
end of the telescope." It's not that the universe is constructed for
us to be
possible, but rather, out of all possible universes we exist here
because
we can.

It is commonly known as the "anthropic principle".

http://en.wikipedia.org/wiki/Anthropic_principle

If there are multiple universes then the weak anthropic
principle applies and tell us little.

Only if the multiple universes have different physical constants. Multiple
universes with the same values wouldn't explain anything.

True but that is just a trivial extension of the
other possibilities I noted, for "If there is only
a single universe then .." read "If all universes
have the same laws and parameters then ..":

If there is only a single universe then the strong
anthropic principle might apply, or the range of
parameters and laws which are possible for a universe
is limited and we were lucky, or the values of the
parameters are fully constrained by the physics of
the event we call the big bang that we have not yet
understood, and those values just happen to allow for
life to evolve.

George

"George Dishman" wrote in message
...
....
http://en.wikipedia.org/wiki/Anthropic_principle

If there are multiple universes then the weak anthropic
principle applies and tell us little.

Only if the multiple universes have different physical constants.
Multiple
universes with the same values wouldn't explain anything.

True but that is just a trivial extension of the
other possibilities I noted, for "If there is only
a single universe then .." read "If all universes
have the same laws and parameters then ..":

That's certainly true - but the original multiple universe hypothesis was
produced to account for the paradoxes of quantum theory. That supposes that
the alternative paths of a particle all happen - but it doesn't imply that
the constants are different.

That's important because multiple universes with different values for the
fundamental constants only addresses the anthropic problem. A casual reader
might assume that the two theories of multiple universes are the same.

J/

BOTW: "Barchester Towers" - Antony Trollope

"Westprog" wrote in message
...

"George Dishman" wrote in message
...
...
http://en.wikipedia.org/wiki/Anthropic_principle

If there are multiple universes then the weak anthropic
principle applies and tell us little.

Only if the multiple universes have different physical constants.
Multiple
universes with the same values wouldn't explain anything.

True but that is just a trivial extension of the
other possibilities I noted, for "If there is only
a single universe then .." read "If all universes
have the same laws and parameters then ..":

That's certainly true - but the original multiple universe hypothesis was
produced to account for the paradoxes of quantum theory. That supposes
that
the alternative paths of a particle all happen - but it doesn't imply that
the constants are different.

That's important because multiple universes with different values for the
fundamental constants only addresses the anthropic problem. A casual
reader
might assume that the two theories of multiple universes are the same.

Yes, good point. I'm not talking of the "Many Worlds"
interpretation of QM where universes have a common
origin but the possibility of universes which arise
independently, for example as described in Alan Guth's
paper that I quoted earlier:

http://www.arxiv.org/abs/astro-ph/0301199

Thanks for mentioning that.

George