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Stupid Science Questions 2

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Henningjohnathan

15:10 / 31.08.06

A cool site for Astrobiology has an entry on this
Silicon-based life

Conceivably, some strange life-forms might be built from silicone-like substances were it not for an apparently fatal flaw in silicon's biological credentials. This is its powerful affinity for oxygen. When carbon is oxidized during the respiratory process of a terrestrial organism (see respiration), it becomes the gas carbon dioxide – a waste material that is easy for a creature to remove from its body. The oxidation of silicon, however, yields a solid because, immediately upon formation, silicon dioxide organizes itself into a lattice in which each silicon atom is surrounded by four oxygens. Disposing of such a substance would pose a major respiratory challenge.

Life-forms must also be able to collect, store, and utilize energy from their environment. In carbon-based biota, the basic energy storage compounds are carbohydrates in which the carbon atoms are linked by single bonds into a chain. A carbohydrate is oxidized to release energy (and the waste products water and carbon dioxide) in a series of controlled steps using enzymes. These enzymes are large, complex molecules (see proteins) which catalyze specific reactions because of their shape and "handedness." A feature of carbon chemistry is that many of its compounds can take right and left forms, and it is this handedness, or chirality, that gives enzymes their ability to recognize and regulate a huge variety of processes in the body. Silicon's failure to give rise to many compounds that display handedness makes it hard to see how it could serve as the basis for the many interconnected chains of reactions needed to support life.

I also like this part:

Even so, it has been pointed out, silicon may have had a part to play in the origin of life on Earth. A curious fact is that terrestrial life-forms utilize exclusively right-handed carbohydrates and left-handed amino acids. One theory to account for this is that the first prebiotic carbon compounds formed in a pool of "primordial soup" on a silica surface having a certain handedness. This handedness of the silicon compound determined the preferred handedness of the carbon compounds now found in terrestrial life.

16:28 / 03.09.06

Hi,
I'm a pharmacology student, but i only have like a working knowledge of physics, and i have a question- but it's vague...

There's this experiment i've heard of. Where you take two atomic clocks, which are keeping the exact same time, you fly one around and space and leave one on earth.
When you get back to earth, the clocks are running at different speeds.

Could anybody explain to me how this works? And perhaps tell me the name of the effect?

thankyou. x.

Kiltartan Cross

18:21 / 03.09.06

It's Relativity.

Essentially the whole thing is a consequence of the speed of light being fixed; every observer sees the speed of light as being the same even if they're moving themself and, to put it very roughly, if the speed of light is fixed then something else - time - has to give.

For the clocks, the effect is very slight - you have to start moving things really, really fast relative to each other before the effect becomes obvious - but measurable.

(anyone who can say it better, please, please do!)

18:50 / 03.09.06

Wow!

So the faster you go the more of a 'time shift' you would get?

This alters my perception of the universe so much. Thank you.

Kiltartan Cross

21:23 / 03.09.06

So the faster you go the more of a 'time shift' you would get?

That's pretty much the size of it; as you approach the speed of light it becomes harder and harder - you have to put in more and more energy - to increase your momentum (mass * speed, roughly). Nothing with mass can ever get to the speed of light, because it would take an infinite amount of energy to get it moving that fast.

If memory serves me right the actual equation is something like τ = √(1 / (v*v)/(c*c)), where v is the speed your object is moving at and c is the speed of light; as v increases, (v*v)/(c*c) tends towards 1, and τ tends towards infinity, which is to say that the dilation becomes infinitely great.

(Once upon a time when I wasn't crap I think I'd've been able to derive you that from first principles, I think the Wiki does it somewhere!)

As it is, I've probably committed several horrible errors there, but the general outline is correct I hope. I know that once you start dealing with General Relativity, with gravity and whatnot, it gets horrendously complicated.

22:54 / 03.09.06

and's why if you left earth at light speed for a year, travelled back, you'd be two years older and the earth would be 10,000 years older, or something ridiculous like that. something on the twin paradox here

Henningjohnathan

18:16 / 05.09.06

Then if you were a ray of light, time would appear to have stopped and you would appear to be everywhere at once?

Many of the books I read that talk about relativity usually mention that Einstein's theory, though it forbids travel AT light speed still leaves room open for objects to travel FASTER than light. How would that work?

11:56 / 11.09.06

I'm not sure how to phrase this question.

The universe is expanding.
We can tell this because the planets are moving apart.

So, how do we know the universe is expanding and the planets aren't just moving apart.

And, Even if the universe was expanding why would this move everything else apart?

Also, can we tell which direction the universe is expanding relative to Earth?

Thankyou.

Jawsus-son Starship

13:13 / 11.09.06

If evoloution is still just a theory, what evidence is missing to "prove it"? And what are other theories that are also supported by (at least some) scientific fact?

ORA ORA ORA ORAAAA!!

13:54 / 11.09.06

I'm not sure if the latter has been done, now, but two of the problems with evolution as an explanation for all the life we have on earth are:
1) abiogenesis (that is, the generation of life from non-life). I'm pretty certain we don't have a good, plausible, or better yet testable explanation for this. And it's kind of a big issue.

2) speciation (is that the right word?) with additional genetic material being present. We have observed speciation, but not with the addition of new genetic material which would be prerequisite for any kind of meaningful macro-evolution.

But this is from memory from arguments from years ago.

Also, theory is distinct from 'not proven[1]/widely accepted as true'. See here for some pertinent discussion.
Also also see the Talk.Origins Archive for a fair collection of learned discussion about evolution/creationism/whatever, from the talk.origins newsgroup.

[1]
Not that you can really 'prove' a theory. Under the current scientific method, the best you can do is fail to disprove it, which, while it does not enable you to cry 'proof!', does allow you to be more confident about it. A little bit. A very little bit.

But that's another question.

13:56 / 11.09.06

A theory already means a robust piece of science, not one where there is anything thought to be missing. The only more "proven" thing is a scientific law, but "law" is only used for very simple phenomena: gas laws, Newton's and so on. Things that are more complicated than eg gas laws tend to stay as "Theory" - which means a robust explanation of a complicated set of phenomena, confirmed as the best explanation so far by lots of different independent groups.

From wikipedia: In scientific usage, a theory does not mean an unsubstantiated guess or hunch, as it often does in other contexts. A theory is a logically self-consistent model or framework for describing the behavior of a related set of natural or social phenomena. It originates from and/or is supported by experimental evidence (see scientific method). In this sense, a theory is a systematic and formalized expression of all previous observations that is predictive, logical and testable. In principle, scientific theories are always tentative, and subject to corrections or inclusion in a yet wider theory. Commonly, a large number of more specific hypotheses may be logically bound together by just one or two theories. As a general rule for use of the term, theories tend to deal with much broader sets of universals than do hypotheses, which ordinarily deal with much more specific sets of phenomena or specific applications of a theory.

14:06 / 11.09.06

The universe is expanding.
We can tell this because the planets are moving apart.

So, how do we know the universe is expanding and the planets aren't just moving apart.

And, Even if the universe was expanding why would this move everything else apart?

Also, can we tell which direction the universe is expanding relative to Earth?

You may find wikipedia's "Metric expansion of space: observational evidence" article useful.

Essentially, it's that everything that we can see has increasing amounts of distance between it, which is visible through a subtle shading of light -- things seem redder than they ought to if they weren't moving away from us (the observer) -- but they also seem to be redder than they should be from every other point where we could put our telescopes.

There's no one point from which expansion happens, and the further things are away from the observer, the faster they appear to be moving away -- no matter where the observer is.

One of the things that may help is if you stop thinking about this on the scale of planets and start thinking in terms of galaxies, which are more larger than planets than planets are larger than us.

Kiltartan Cross

14:09 / 11.09.06

I'm not sure how to phrase this question.

The universe is expanding.
We can tell this because the planets are moving apart.

So, how do we know the universe is expanding and the planets aren't just moving apart.

And, Even if the universe was expanding why would this move everything else apart?

Also, can we tell which direction the universe is expanding relative to Earth?

Thankyou.

Righto. Strictly speaking, it's not planets which we can see moving apart, but entire galaxies; the planets (and indeed everything else in the solar system) are expanding, but the effect on such small scales is tiny.

Basically, when we look up into the sky, we see that (nearly) every galaxy is moving away from us. We can tell that they're moving away because of the way that the light from them is shifted to lower frequencies - the "red shift". This is a consequence of the speed of light being fixed; it's pretty much beyond doubt, in other words, that everything else really is moving away from us.

Essentially, every part of the universe is moving away from every other part (we think) - what is expanding is the underlying metric of space itself; it's as if distance itself was getting bigger. But very slowly!

Henningjohnathan

14:37 / 11.09.06

However, as noted before, the expansion of the universe is accelerating (which is where the theories of a "dark energy" with some sort of negative gravitational pressure come from) so, from current data, it appears that the universe will never "collapse" - it will simply expand forever (or until it reaches some sort of steady state due to entropic tendencies).

Here's a somewhat stupid question, but based upon a trope you see in science fiction:

At the micro or "quantum" scale it seems like the universe follows different rules than on our experiential level. Also on the Macro or "galactic" scale, similarly, it seems like the rules aren't easily describable in terms we know.

First, is there really a "bottom" scale? Can we say for certain that there isn't a scale even smaller that is to "quantum" what the micro scale is to us?

Second, could there be a gigantic scale where what we consider to be "galactic" is more like "quantum" from that perspective?

Kiltartan Cross

15:01 / 11.09.06

I suspect the answers to both are "yes", closely followed by "but buggered if we'll ever be able to know the answer for the foreseeable future".

My Mom Thinks I'm Cool

15:05 / 11.09.06

sorry, jumping in a bit late...

for one thing, when considering energy use in life (as we know it), respiration is only one half of the picture; photosynthesis is something that has to happen first. The big biochem pathway involved is called the Crebs Cycle (hmm, or at least it was when I was in college...)

As for the problem with silicon life forms and respiration, it seems silly to assume that alternate life will necessarily respire using oxygen, since even on Earth that's not always the case.

As for the scale question, I don't know of any ideas about some larger-than-cosmic scale, but there is some thought about a theoretical smallest-possible-scale: the Planck Length is, possibly, the smallest measurable distance...at least using measuring techniques we understand today. I guess a rough large-scale equivalent would be the Hubble Distance, which is again not a real limit on how big things can get but more of a limit on what we can observe due to the constraint of the speed of light.

As I understand it, the quantum effects you're talking about might not be due to size so much as to numbers; in other words, one particle behaves like X, but when modeling a group of particles you can use probability and statistics to simplify the behavior to type Y, which has easier math. It's not that Newton's simple laws aren't right, but rather that they're a simplification which is only valid in a given subset of the more general case.

You may also be referring to the apparent disconnect between theories on relativity and quantum mechanics, which theories like strings attempt to resolve...

23:19 / 12.09.06

Sorry to cross-post...

If evoloution is still just a theory, what evidence is missing to "prove it"? And what are other theories that are also supported by (at least some) scientific fact?

Like Saturn's Nod said, "theory" isn't 'just' anything, when used is the scientific theory sense. Evolution has been observed in nature, and has been supported by a lot of comparison of genomes between different species.

As to what's missing - well, we can never go back and observe it giving rise to those species, including humans, which exist at present. Strictly speaking, the strictly-defined hypothesis that evolution gave rise to humans diverging from apes (for example) is not falsifiable, and therefore cannot be scientifically tested.

Similarly, you can't disprove that God did it all. Or that God made evolution happen. Which is why there's all the brouhaha - scientists are aware of the huge amount of evidence, creationists know that it's still all down to belief.

By other theories, do you mean in the evolution field, or other sciences? I believe Quantum theory and Relativity are theories.

Essentially, every part of the universe is moving away from every other part (we think) - what is expanding is the underlying metric of space itself; it's as if distance itself was getting bigger. But very slowly!

Ever since I started reading about this (and I'm not physicist or anything), I've wondered if it couldn't be equally well explained by stating that everything is shrinking. Including ourselves, all matter is getting smaller, therefore it appears that the distances inbetween are getting larger. (...?)

Cloned Christ on a HoverDonkey

23:52 / 12.09.06

Like your idea on shrinking, Red.

But like you said above, there's no way of testing it. It's all frame of reference stuff. Each idea - space expanding/matter shrinking - is equally viable and equally unprovable, so does it even matter which viewpoint you take as the observations will always be the same?

As for evolution - we have managed to observe a life-form evolve from its earliest known stage to its present day manifestation and it matches evolutionary theory to a tee.

The organism is the AIDS virus and it has evolved rapidly (as tiny life forms must) and the unique thing is that we've seen it from (what we think is) its genesis through to its current form.

All that does though is support the theory, not prove it. That's the trouble with theories - they can never be proved, only reinforced.

Which is why these kind of debates will never end.

Henningjohnathan

14:10 / 13.09.06

The shrinking idea makes sense in some ways if you look at "string" theory as matter and energy based on a kind of waveform. If you pluck a guitar string even though it gives off the same tone eventually it runs out of energy (btw, SSQ: if you pluck a string in a vaccuum would it vibrate forever? Does the guitar body take energy from the oscillation?). Therefore, if there is some sort of energetic process at the fundamental level of existence, like a vibrating string, then perhaps it is "shrinking" as it loses energy.

Jawsus-son Starship

16:13 / 13.09.06

cheers guys!

When I said what other theories, I meant about opposing theories to evoloution which have science backing them up. Are there any?

Henningjohnathan

16:37 / 13.09.06

That's a good question.

Essentially, evolution (ver broadly) proposes that all life on earth (whether there is evidence still in existence or not) derives from a single source. That all mammals for example, derive from a single species of proto-mammal, for example.

Would an alternative be that life on earth did NOT derive from a single source? That some mammals, for example, derive from different lines of proto-mammel who did not themselves come from a single source?

Or is that simply an alternative "evolutionary" theory - not an alternative to evolution?

Also, what exactly are the theories that cover the natural development of single celled organisms from a bunch of chemicals to a living creature? And what theories cover the development of multi-cellular orgnanisms?

18:08 / 13.09.06

I don't think that there is any scientific evidence for an alternative to evolution, when you define evolution as "living beings changing in response to their environment".

Then genetics can be used to explain how evolution occurs, and evolution can be used to explain how species arise. To be honest, I think Darwinian evolution, to anyone who understands how it works, and the genetics underlying it, is such a self-evident truth, that no one in scientific circles bothers with trying to come up with another mechanism. Unless very strong evidence for non-evolutionary changes was discovered (e.g. a species suddenly becoming dramatically different literally overnight), that isn't going to change.

Genetics pretty much killed the debate between Lamarckian and Darwinian evolution, in favour of the latter. However, there is evidence that epigenetics can act in a Lamarckian way, so both are good!

Henningjohnathan

22:23 / 13.09.06

I don't think that there is any scientific evidence for an alternative to evolution, when you define evolution as "living beings changing in response to their environment".

Or something like that. Is there an evolutionary that claims that the changes are actual responses to the environment? As I understand it, it is changes in the environment that allows certain traits to be passed on and other less fit traits die out. Therefore, the environment did not cause the change - rather the change or or trait emerged and enabled the animal to survive and procreate. Traits that did not accomplish this function, naturally, became extinct.

An "alternative" to evolution in that sense is the idea that the traits (from feet to flippers in whales, for example) were actual responses to the environment (possibly from more hunting/swimming behavior in the water) rather than random mutation.

22:49 / 13.09.06

Yeah, exactly. I was being too generalist. But you're right.

What Darwin and subsequent genetic discoveries showed was that there's natural variation in the population, due to genes, and so some individuals might have an advantage - e.g. birds with longer beaks can feed off buried insects, and in the absence of other food, they survive and pass their genes on.

What Lamarck thought was that environment caused the differences - like giraffes getting long necks cause they have to stretch for leaves high on trees.

This can happen, though - the most famous (or best studied) case in humans being the Dutch famine of 44-45, where poor diet resulted in a generation of low birth weight babies, who then went on to have low birth-weight babies (despite a themselves having a normal diet during pregnancy). Transmission of an advantageous trait, caused by the environment (epigenetically - through DNA methylation or something).

22:52 / 13.09.06

A good article on this.

Kiltartan Cross

11:03 / 14.09.06

Also, evolution can (and often does) cause traits which are favourable to short term survival but harmful to long term survival to prosper. I expect there's also a significant 'blind chance' effect, particularly with confined populations, where sheer misfortunate splatters an advanced species into extinction just 'cause they happened to live next to Krakatoa, or have a meteor fall on their head, or find the Earth starts to freeze over, or run into the classic "humans with boom-sticks!" OCP.
Nature sucks.

Henningjohnathan

15:39 / 14.09.06

It's an interesting question about the relationship between "random" genetic diversity and direct adaptation. Just like whales and dolphins, the human mammal has the genetic capability to grow flippers.

However, it really strectches credulity to think that there will ever be a race of mermans (mermaids and mermen). Of course, humans seem to be at a genetic dead end, so they aren't necessarily a good example, but lets look at the hypothetical development of the whale.

Supposedly it began as a somewhat very large wolf like predator probably tens of millions of years ago. There is a huge amount of difference between a paw and a flipper.

What I'd like to see, and what I think geneticists and evolutionary theorists should start doing is getting away from the dumb straight line models like those idiotic diagrams showing the progress of man from homo erectus up to a guy in a three-piece suit.

What I'd like to see is a short program explaining in understandable terms the genetics and biology of going from a wolfish paw to a whale's flipper, for example.

20:21 / 14.09.06

Why are humans at a genetic dead end? In fact, I see good prospects, with humans occupying so many different environments and niches that it would be hard to get rid of them... Probably worth a thread of its own.

The straight line models are unfortunately often all that's possible when you're looking at the few surviving species, and ignoring the unknown, never-observed dozens (maybe hundreds) of branches that split off and died out between the last divergence "event". Also, the fossil record is often so sparse, and it's all we have to infer what our direct ancestors looked like, so everything gets "forced" onto this straight line.

10:50 / 15.09.06

I've always thought the end point of evoloution is when a species can fully modify it's own genome. I.e Meme's over genes.

Henningjohnathan

12:40 / 15.09.06

I meant that genetically, humans don't have as much diversity as many other animals so you won't see a lot of variety of physiological options. We depend pretty much on our brains as the primary evolutionary advantage and I see that as a dead end.

16:13 / 15.09.06

I've always thought the end point of evoloution is when a species can fully modify it's own genome. I.e Meme's over genes.

Not the end point of evolution. The end point of evolution by natural selection. In the future, instead of enduring hundreds of generations of survival of the (often slightly) fittest, the Homo sapiens' populations will just genetic engineer themselves and adapt to any given environment (even alien ones) in a single generation. Evolution, as it is (and it is mostly simply adapting), will actually get a lot faster.

Henningjohnathan

16:29 / 15.09.06

Or we'll all be replaced by much sparter and stronger machines we invent rather than give birth to.

In GHOST IN THE SHELL 2: INNOCENCE, a character has a line that says something like, "all our cities, industry and technology is as much an expression of our DNA as our eyes, arms and legs."

Kiltartan Cross

18:27 / 15.09.06

"all our cities, industry and technology is as much an expression of our DNA as our eyes, arms and legs."

I think that's both true and false. In a sense, yes, all that we do is an expression of our DNA; but in another sense, our cities, industry, technology and everything else we do possess an ability to perpetuate themselves: religions are the obvious example, but all of our cultures, our languages, the way we make and build and break things have an inertia of their own, a moment tied up in the physical world, separate from our genetic programming. These things, this culture, have been created by us, but they have something of a life of their own.

Henningjohnathan

19:16 / 15.09.06

Or do they?

There is also the consideration of "superorganisms." the genome as expressed throughout the species. If we look at the human race as a superorganism or collection of superorganisms rather than a collection of individuals, then the cities and technology start to resemble more something like the shell to a snail, separate but dependent upon the organism.

After all, none of our technology has a completely independent existence. Until we develop truly artificial consciousness and life, its purpose is entirely relative to our use of it.

Kiltartan Cross

20:14 / 15.09.06

I'm not sure. One could see humanity and all its works as a superorganism - or part of the Gaia superorganism - or one could see us as a background environment - a culture, even - in which our Culture develops. I think it depends on whether you view humanity as including a time dimension (that is, view humanity as including everything humans have done) or view humanity as including only the present. If the former, everything we've made is part of us; if the latter, everything we've made is sitting around us in the present, influencing us, reproducing itself, and so on. I guess the former is probably more "correct" and certainly more comprehensive, but then, the past is another country, or however it goes, and we're living in the present.

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