Re: The Laws of Intelligence Examined

Zoe <muze10@xxxxxxx> wrote:
On Wed, 22 Mar 2006 21:39:10 +0000 (UTC),
carlip-nospam@xxxxxxxxxxxxxxxxxxx wrote:

Zoe <muze10@xxxxxxx> wrote:

[...]
gravity is fascinating, from what I've been reading. The fact that
two stars appear to exert an instantaneous effect on each other, even
though they are millions of miles apart, would seem to indicate that
there is some force that is faster than light.

There is as yet no direct measurement of the "speed of gravity." But
all observations so far are consistent with general relativity, our
best current theory of gravity. If general relativity is correct,
gravity propagates at the speed of light, not instantaneously.

well, isn't general relativity correct only in its sphere, but when
checked against quantum mechanics, it appears to be not correct? And
vice versa, when quantum mechanics is studied in the context of
general relativity, it, too, encounters problems? Separate, they work
in their fields, but together, both theories cannot be correct?

Roughly. The correct statement is that we do not now have a quantum
theory of gravity, that is, a theory that combines general relativity
and quantum mechanics. But, as you say, each theory works very well
in the regime in which it is currently testable -- one of the main
difficulties in finding a quantum theory of gravity is that we have
no experimental hints, because we have no current experiments that can
probe regimes in which both general relativity and quantum mechanics
are likely to be important.

(The typical scale on which quantum gravity is likely to be needed is about
10^{-35} meters, that is, .00000000000000000000000000000000001 meters, if
I counted my zeros correctly.)

That would leave the door open for gravity to not necessarily
propagate at the speed of light, but to propagate faster than c,
wouldn't it?

Why do you say that? Both general relativity and quantum field theory
have speed-of-light limits. Why should a combination of the two not?

What about superstrings? I've read a little about them and the
question could be asked: What if the entire universe consists of and
is connected by a fabric of superstrings so that what we consider to
be empty space that needs to be traversed by gravitational
attractions, is, in fact, one continuous fabric with hills (i.e.,
stars and planets) and valleys (i.e., space) so that any change in the
positions of the stars would automatically and instantaneously be felt
by the others, without need to wait for gravity to travel from one
point to the next?

That doesn't help. Impulses moving along a superstring can't move
faster than light, either.

(If you want a technical discussion of this -- you probably don't --
see my paper at http://arxiv.org/abs/gr-qc/9909087.)

I printed your paper to read in spare moments during my day. Frankly,
I don't understand the math, but I trust that it proves your point,
which is that the absence of gravitational aberration can be explained
by the fact that the aberration has been canceled by
velocity-dependent interactions.

It certainly is not for me to argue with someone as learned as you
are, but please allow me ask a few befuddled questions.

Van Flandern proposes that gravity propagates at a speed much greater
than c. What if the aberration that you say is canceled by
velocity-dependent interactions really doesn't exist after all? Would
that mean that the lack of aberration makes both you and Van Flandern
potentially correct? It makes you correct via your mathematical proof
and it makes Van Flandern correct via the possible reality that there
really is no aberration after all. If so, how can it be determined
who is really correct?

Most of these questions don't quite make sense -- the words you are using
don't mean what you seem to think they do. But in answer to your last
question, future experiments should be able to measure the speed of
gravity directly -- for example, by comparing arrival time of light and
gravitational waves from a supernova.

The cancellation that you prove through your mathematical equations is
one that is based on such precise conditions that it makes me wonder
about the chances of this kind of precision happening by chance. But
then, that is the forte of evolutionary theory. The lottery is won on
a consistent basis by the same person.

It doesn't happen "by chance." It happens because of basic physical
principles -- conservation of energy and angular momentum -- that are
built into general relativity. You seem far too ready to assume that
because you personally don't understand something, it must be improbable.

Also, back to the idea of travel being faster than light, is it
possible that at speeds nearing the speed of c, that the atoms,
quarks, charms, or whatever the particles are in the speeding mass,
will bounce around so violently, they would behave the way particles
do in a particle smasher, getting to a point where matter and
antimatter would annihilate each other, producing pure energy?

No. Moving rapidly doesn't make things bounce around. Right now,
the Earth is moving around the Sun at a speed of about 65,000 miles
per hour. Are you bouncing around?

[...]
As to your statement that a cloud of hydrogen gas in space is subject
to its own gravity, are you saying that the more atoms or molecules
there are in a gas, the higher the chance is that the gas will become
dense and not spread out?

Yes, definitely.

is this based on Jeans mass, as some posters have mentioned?

Jeans did the original calculations, under some simplified assumptions,
about a century ago. If you make more realistic assumptions, you can
get some differences in the rate of collapse of a cloud of gas, and
the time scale for forming stars. (The change can go in either direction,
depending on details like the purity of the hydrogen, which can affect
radiative cooling.) But the basic conclusions don't change.

[...]
Is there some law of physics that says that
the greater the volume of gas, the more prone are its particles to be
attracted to each other?

Each particle is attracted to *all* of the other particles in the gas.
So the more particles there are, the more attraction there is. There's
no mystery here -- you are attracted to the Earth more strongly than to,
say, your computer terminal because the Earth has "more particles" (more
mass).

if all the other particles in the gas cloud are attracted to all other
particles, then the "big bang" should have produced a single, giant
star, shouldn't it?

No, because the material of the Universe wasn't at rest. To go back to
your original example, if you drop, say, an apple, it falls. If you
throw it up in the air, it eventually turns around and falls back, but
that takes longer. If you could throw it fast enough -- at the Earth's
escape velocity -- it would slow down but never stop. In the same way,
if you have a large enough cloud of hydrogen at rest, or expanding slowly,
its gravity will make it collapse. But if it's expanding faster than
its escape velocity, it will keep expanding.

How does that work, especially if the gas is
spreading out, according to 2LoT (if such a law exists out there)? I
mean, gases on earth do not tend to pack more closely depending on the
quantity, do they?

You're mixing up things that happen on different scales. You need a *lot*
of gas before the gravitational attraction of the gas to itself is strong
enough to be very noticeable.

this seems to be similar to the requirement for evolution -- you need
a LOT of time before mutations will accumulate sufficiently and
fortuitously enough to produce the life forms we see today. Isn't
this all rather vague and unscientific? A lot of time will do it. A
lot of gas will do it. With no step-by-step description of how it is
done.

On the contrary, it's you who are being unscientific here. For the case
of star formation, for example, we have *extremely* well-tested theories.
We know experimentally how gravity behaves from scales of less than a
millimeter to scales far larger than the Solar System. We've tested these
theories to precisions of one part in 1000000000000000. We have enormous
numbers of astronomical observations that look just like what the theory
says gas and stars should look like in various stages of formation. And
you come along and say, "But what if by some unknown means the theories
all suddenly become wrong at scales beyond the current tests, in a way
that magically produces astronomical observations that look just like
star formation should, but are really something else?"

Are there instruments powerful enough to detect fractions of degrees
of difference in gravitation attraction between gas clouds of
different sizes here on earth?

Sure.

And how does a star that starts out consisting of strictly hydrogen
and/or helium become the kind of world that we know today, with
minerals and rocks and dense masses that today are heavier than gases?

Nuclear fusion. Just as hydrogen atoms at high enough temperature and
pressure fuse to form helium, helium atoms at high enough temperature and
pressure fuse to form heavier elements. Fowler won the Nobel Prize in
1983 for his pioneering work on this -- you can read his Nobel Prize
lecture at nobelprize.org/physics/laureates/1983/fowler-lecture.html.
Today we can observe much of the process in the lab.

And does gas always have to go to liquid form before it becomes a
solid?

No.

[...]
Remember, a star like the Sun is hundreds
of thousands of times more massive than the whole Earth.

if the sun is composed of 75% hydrogen and 25% helium, why has it not
coalesced into the kind of happily evolving stars of which you speak?

It has. What do you think it is?

Steve Carlip

.

Relevant Pages

  • Re: The Laws of Intelligence Examined
    ... There is as yet no direct measurement of the "speed of gravity." ... stars and planets) and valleys so that any change in the ... they would behave the way particles ... there are in a gas, the higher the chance is that the gas will become ...
    (talk.origins)
  • Re: The Laws of Intelligence Examined
    ... There is as yet no direct measurement of the "speed of gravity." ... stars and planets) and valleys so that any change in the ... particles seen in particle accelerator experiments, ... there are in a gas, the higher the chance is that the gas will become ...
    (talk.origins)
  • Re: Giant gas planets and how they gathered their gas at formation
    ... Gas by itself does not possess enough gravity. ... You have just "proved" that stars can't be made of mostly hydrogen and ... Get enough hydrogen and helium together and you get plenty of gravity, ...
    (uk.sci.astronomy)
  • Re: PD has questions about science. Can any of you help?
    ... Folks, Timo is way smarter than others who reply, here. ... that my New Science is wrong. ... The gravity results should be ... it was the estimates of the masses of the stars and galaxies that was ...
    (sci.physics)
  • Multi-wavelength images help astronomers study star birth, death (Forwarded)
    ... University of Illinois at Urbana-Champaign ... picture of the birth, life and death of massive stars, and their effect ... on the gas and dust of the interstellar medium surrounding them. ... "We expected significant infrared emission to be generated by dust ...
    (sci.astro)