gilly54

If I'm understanding your question correctly, I think science is always discovering why nature works the way it does. I marvel at the intricate, interdependencies and relationships of ecosystems and their organisms which took millennia to develop, (and which we are altering at an alarming rate). I don't think we don't need to "test" things, as in a laboratory setting in order to understand the functional relationships in nature. Keen, laborious observation can work just as well in explaining why systems work.

Why does there have to be an abstract aspect to life anyway?

IMO, science will always have religion on the run. As science explains phenomena attributed to God, theists have to rethink their dogma to keep the god-belief machinery going (and the collection plates full). Being "painted into the corner" by science, abstractions are the only refuge, and of no importance, to me anyway.

Science doesn't try to go beyong explaining the "world". It doesn't have to because there isn't anything else to explain! I guess it is this simple impasse that causes so many of my theist friends to pray for me!

seebs

I dunno. There's lots of things that I think are interesting about the nature of the world, or mathematics, where knowing exactly how it works doesn't answer the question "why not some other way?". That question *can't* be answered in the general case.

gilly54

We can always observe the behaviour of an animal, including ourselves, and wonder "why doesn't it do it another way?" Possibly because its present physical structure prevents it from an alternative. But, it will either mutate/adapt, just like we did from walking on all fours to bi-pedal. Or, it will stay just like it is, having found a survival tactic that works just fine. Who are we to question success?! So, if I'm understanding you, I think the "other ways" can be explained. It's called evolution.

seebs

No, I mean stuff like "Why isn't pi 3.2 exactly". Underlying constants. We may occasionally be able to break one of them down into a relationship between others, but we can never get away from them. So... There's always an outer limit, and we can always point at it and say "coincidence" or "goddidit" or "it couldn't be any other way", whatever makes us happy.

Daydreamer

Supposedly - supposedly mind you - Super String Theory will allow us to pluck these constants from the vacuum before the Big Bang (assuming of course a non-cyclic universe).

I'm not holding my hopes up, and the science involved is leaps and bounds beyond my comprehension, but the Time of the Great Answer (to steal from the late Douglas Adams) may not be too far off.

lpetrich

I'll put together a scenario:

Look back to the Earth of a little over 4 billion years ago, the age of the oldest known rocks.

The Earth and the other inner planets had swept up most of the smaller rocks left in the inner Solar System after their formation -- and had also swept up some comets.

The Earth had had an ocean of water (not a notion of water!), and an atmosphere that was mostly nitrogen and carbon dioxide -- which kept the Earth warm enough to have liquid water, despite the Sun being only 75% or so of its present brightness.

And back then, it had had only small "continents" back then, but it had had a lot of undersea volcanism and hot springs; water would percolate through the ocean crust, get heated by some nearby magma, and flow upward in hot-spring channels.

Though the oceans and the atmosphere alone would not be enough to produce much prebiotic chemistry, because they are not rich enough in hydrogen, the hot springs would be a different story. Hydrogen from the Earth's interior would react with the nitrogen and carbon dioxide in the water, assisted by the heat and the catalytic properties of the rocks' minerals that the water flows past.

Thus, these hot springs would become the cooking pots of the Primordial Soup, though in the ocean itself, the soup would do not much more than accumulate.

The hot springs would be home to lots of interesting chemical reactions, such as organic molecules catalyzing the formation of other organic molecules.

Eventually, one day, some bubble of hydrocarbonlike material would form and surround some such molecules. This bubble would let small molecules through but not large ones. And inside the bubble, some of these mutually-catalyzing molecules would form big molecules that catalyze the production of molecules like themselves.

How the first self-reproducing systems got started and what was doing the self-reproducing are murky questions, I will concede -- I'm listing the first self-reproducing molecules as an unknown because it was likely not a nucleic acid. Nucleic-acid bases can easily be produced in prebiotic-chemistry experiments, but another part, ribose, is much more difficult to produce in such experiments.

However, this self-reproducing system eventually replaced its original self-reproducing molecules with RNA ones, somehow learning how to make ribose.

In this system, the RNA world, RNA molecules served as both information molecules and enzymes; RNA enzymes often got the help of some other molecules, or cofactors. There are some present-day cofactors that still use RNA, like NAD, FAD, Coenzyme A, etc.; to me, this is strong evidence for the existence of a former RNA world.

From the RNA world, DNA evolved as a master-copy specialization of RNA -- it would never get modified to become any enzyme, although DNA enzymes are as feasible as RNA enzymes. Being unmodified makes reproduction much easier, and allows the handling of more genes.

And among the RNA-enzyme cofactors were amino acids. Eventually, some system emerged for constructing multiple-amino-acid cofactors with the help of a RNA template, and this system expanded and expanded until the amino-acid chains were most of the resulting enzymes, as we see in all existing organisms.

Also a problem was running out of food; though the Primordial Soup had plenty of different organic molecules, multiplying early organisms would eat much of the more desirable molecules. This would create selection pressures to either use substitutes or to assemble these molecules from other ones -- and the latter route was often adopted, with biosynthesis pathways becoming constructed backwards to relatively simple organic molecules.

Eventually, an organism would result that needed no organic molecules as food, making them from carbon dioxide, hydrogen, ammonia or nitrates, etc. It still lived in hot springs, extracting energy by combining hydrogen with sulfur or sulfates.

This would become the ancestor of all surviving life on Earth; there are similar sorts of thermophilic bacteria still alive today.

gilly54

Ipetrich, I printed your concise yet well-written, understandable post for my daughter, who will be taking AP biology in her junior year at high school next year. Thank you.

(PS:we lived in Livermore on Hummingbird Lane (1980-86).

And Daydreamer, now you have got me searching about the Super String Theory. Damn, this website and (most)of its participants are so knowledgeable and willing to share their expertise. Thank you.

Seebs, I think I understand the questions you are asking. I just don't see why, until we solve them, we need to assign a god to explain them.

lpetrich

I'm flattered by that appreciation. I had to be a bit sketchy, but I could expand on parts of it.

Here's <a href="http://www.superstringtheory.com/" target="_blank">a good superstring-theory site</a>, discussing the superstring question at different levels of technical detail. I'll try to explain more in an upcoming post.

seebs

We don't. I just object to hand-waving claiming that "science" will miraculously answer all the questions people could possibly turn to religion for.

lpetrich

As to how one comes up with superstrings, I'll try to give a simple summary.

We start with the known elementary particles of the Standard Model. "Particles" may be a misleading word, because all of them are really quantized fields, which have a value at every point in space-time, but discussing any further would require discussing some of the murkier aspects of quantum mechanics.

The Standard Model of elementary particles includes the following motley collection of particles:

*** Spin 0:

Higgs particle: mass ~ a few hundred GeV; not detected, nonzero ground-state field value induces masses of several other particles by "symmetry breaking")

*** Spin 1/2: three complete generations known; there are three flavors of same-quantum-number elementary particle:

(These are the leptons; they have no "color" degrees of freedom)
(Weak interaction relates these two sets)

Charge -1:
Electron: mass - 0.0005 GeV
Muon: mass - 0.1 GeV
Tau: mass - 2 GeV

Charge 0:
Electron neutrino
Muon neutrino
Tau neutrino

(These are all quarks, which have three possible states called "color")
(Weak interaction relates these two sets)

Charge -1/3:
Down: mass ~ a few * 0.001 GeV
Strange: mass ~ 0.1 GeV
Bottom: mass ~ 5 GeV

Charge +2/3:
Up: mass ~ a few * 0.001 GeV
Charm: mass ~ 1 GeV
Top: mass ~ 150 GeV

(Note: protons and neutrons are composite, being up-up-down and up-down-down, respectively; they have masses ~ 0.9 GeV)

*** Spin 1: these are all "gauge fields", related to certain elementary-particle symmetries, which are relabelings that keep them looking the same. Some of these symmetries are hidden or "broken" at relatively low energies, however.

Gluon: mass 0, charge 0, "color" degrees of freedom: 8 (they interact with each other and with the "color" degrees of freedom of quarks)

Electroweak:
W's (W+, W0, W-): mass 0
B: mass 0

Their interaction with the Higgs produces these masses:

W+,W-: 80 GeV
Mixtures of W0 and B:
Z: 90 GeV
photon: 0

*** Spin 2:
Quantum of gravitational field, the graviton

And I'm not even listing the weak-interaction cross-generation factors (down, strange, and bottom all can decay into up, for example).

If this seems like a complicated mess, you are not alone; that is why particle physicists have pursued the study of Grand Unified Theories, or GUT's. In such theories, the elementary particles are different degrees of freedom of a few basic kinds of particles that have some big symmetry. A symmetry which gets broken at an energy scale of 10^15 GeV and makes the different degrees of freedom act like separate particles.

But one problem is why are there all these different spins of elementary particles? The favorite solution to that problem has been "supersymmetry", a proposed symmetry between particles of integer and half-odd spin; every integer-spin particle would match some half-odd one and vice versa.

Thus, the elementary spin-0 particles must have spin-1/2 counterparts ("higgsinos"), the elementary spin-1/2 particles must have spin-0 counterparts ("sleptons", "squarks"), the elementary spin-1 particles must have spin-1/2 counterparts ("photino", "wino", "zino", "gluino"), and the graviton must have a spin-3/2 gravitino.

However, unbroken supersymmetry requires them to have the same masses as their counterparts, but that is not observed. Thus supersymmetry must somehow be broken, as the electroweak and GUT ones are, and how that happens is unclear.

Now we turn to how the GUT and gravity might be related. The GUT mass scale, 10^15 GeV, is close to the quantum-gravity mass scale, 10^19 GeV -- which suggests some relationship.

And one effort to construct a gravity-including GUT has been to include supersymmetry in gravity, producing "supergravity". Such theories can produce lots of particles with different spins -- 0, 1/2, 1, 3/2, and 2, but getting a reasonable, SM-including GUT out of supergravity is difficult.

The next step is to go beyond the usual particle theories and try out string theories; these pictures elementary entities with stringlike properties, including an infinite spectrum of vibration-mode energies.

One can get gravity from string theories in a reasonable fashion; this is in direct contrast with the more usual quantum-gravity efforts, which produce infinities that are difficult to subtract away, as can be done with most other sorts of elementary particles.

But can one get the rest of the Standard Model? Let's see.

The Standard Model has spin-1/2 particles, and is expected to be a subset of some supersymmetric theory, meaning that we ought to consider supersymmetric strings or "superstrings".

However, to be quantum-mechanically self-consistent, such entities like to live in a space-time with dimension 10, and we live in a 4-dimensional space-time.

So it is expected that 6 of those dimensions have curled up into a tiny ball with a size in the range of the GUT and quantum-gravity length scales, or 10^-30 to 10^-34 m.

And the topology of that ball will give masses to many of the superstring's massless modes, though some will remain massless.

And a nice thing is that an appropriate ball topology could produce a GUT that contains the Standard Model!

But why does the Universe have the space-time topology that it does, and not some other topology? Why 4 big and 6 small, and not 2 big and 8 small, or 6 big and 4 small, or ...? And why one small-part topology instead of another?

[ May 26, 2002: Message edited by: lpetrich ]</p>