Re: The Hidden Harmony of the Universe

Joseph Humming <joseph@xxxxxxxxxxxxxxxx> wrote:
On Jan 20, 8:47 pm, carlip-nos...@xxxxxxxxxxxxxxxxxxx wrote:

[...]
If you have a large collection of subatomic particles in a hot, dense
gas (as was the situation in the very early universe), and if they
interact the way subatomic particles in our universe do, the
probability of them combining to form hydrogen, along with some
deuterium, tritium, lithium, and beryllium, is one.  If the resulting
gases are dense enough and spread out unevenly enough (as they
were in the early universe), the probability of some of the dense
areas collapsing to form stars is one.  If stars form, and if the
particles in the stars interact the way they do in our universe,
the probability of heavier elements forming is one.  If the stars
evolve as they do in our universe, the probability of some of these
heavy elements blowing out into space is one.  We can, in fact, do
a pretty good job of predicting the abundances of elements in the
universe from first principles; William Fowler won a Nobel Prize
in physics in 1983 for this.  (You can look at his Prize lecture at
nobelprize.org/nobel_prizes/physics/laureates/1983/fowler-lecture.html.)

Oh, there's lots of "ifs" there. You're really saying: if things were
the way they are things would be the way they are. What is the
probability of achieving 6 desirable ifs?

Well, if the universe is all the dream of a giant green caterpillar, the
probability may depend on what the caterpillar had for dinner last
night...

If you read what I wrote, instead of just counting words, you will see
that there are only two independent "ifs" -- if the universe started
out in something like the standard big bang, and if the laws of physics
are roughly what we observe. Given those, the formation of stable
matter is pretty much certain.

If you are asking for the probability of the existing laws of physics,
or of the initial conditions of standard cosmology, the answer is that
no one has the slightest idea. They may be extremely improbable;
they may be inevitable. As I wrote,
[...]

If you want to change one of the assumptions -- say, the way the
particles interact with each other -- you'll have to tell me what
kinds of changes you will allow; otherwise, the idea of assigning a
probability makes no sense.  

This is fundamental. Assigning a probability to an event only makes
sense if you have a population, a set of possible events. The probability
of getting a 2 when you roll a die is 1/6, but only if the die has six
sides; it would be 1/4 for a four-sided die, 1/100 for a hundred-sided
die. Unless you can tell me the "population" of laws of physics --
the range of laws you will allow -- it is not just impossible to assign
a probability, it's meaningless.

There has been a lot of work on probabilities of various outcomes
given certain choices of populations of laws of physics. See, for
example,

"Stars in Other Universes: Stellar structure with different fundamental
constants," F. Adams, http://arxiv.org/abs/0807.3697

"The Cold Big-Bang Cosmology as a Counter-example to Several Anthropic
Arguments," A. Aguirre, http://arxiv.org/abs/astro-ph/0106143

"A Universe Without Weak Interactions," R. Harnik et al.,
http://arxiv.org/abs/hep-ph/0604027

But each of these requires certain particular choices of how one might
vary the laws of physics. Since we don't know what determines these
laws, we just don't know what can, or should, be allowed to vary.

Probability in this context has no meaning.

[...]
Now, my questions: Do they combine "accidentally" to form the
matter we know?

Yes.

Accidentally, ja? My case is getting larger by the minute.

Why? Do you think accidents are uncommon?

Take a breath. It is an accident that your lungs are getting any oxygen
-- the molecules of air are moving around the room in a pretty nearly
unpredictable manner, colliding with each other "accidentally" and
ricocheting off in one direction or another. It is conceivable that the
next time you take a breath, all of the oxygen molecules will have
been knocked over to the top left corner of the room. It's not very
likely... but that's because of all of the "accidental" collisions.

Or: Does the matter we know almost create itself, actually
creating these particles to fill this or that gap?

No.

Ohhh? How about virtual particles, non-existent bridges to hold
together the existing particles?

What about them? They are convenient ways of visualizing complex
mathematical descriptions of interactions between particles. They
are not "the matter we know," which is what you were asking about.

Or : Does matter, or the particles, have an inherent tendency to
coalesce?

It depends on what you mean by "tendency."  Elementary particles
interact with each other.  These interactions are sometimes attractive
-- they cause particles to combine.

Or; Finally, Does energy transmute to several forms of matter, or
only one?

All.  In the extremely early universe, when the temperature was very
high, the elementary particles all existed in equilibrium.

Is there a fundamental link particle  between energy and the matter
we know?

What's a "link particle"?

Is there one irreducible particle that gives rise to all others?

To the best of our knowledge, no. There have been attempts to build
models in which the 36 or so known particles are made up of a smaller
number of "preons," but so far they have not worked (read that as
"failed miserably"), and there is absolutely no experimental evidence
for such a thing.

Steve Carlip

.

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