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Stupid Science Questions 2

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04:03 / 16.03.07

I was just wondering, can a network (in mathematical sense) composed of information 'phase shift' like physical systems? Can someone point me to any literature or arxiv docu around the net?

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13:02 / 16.03.07

Try some of Harrison C. White's stuff. He's a sociologist/solid state physicist who's done a lot of seminal work in network analysis and mathematical modelling of markets, amongst heaps of other interesting stuff. I can't really recommend any starting point as my eyes cloud over when I see the equations he uses.
There are others in the cognitive/information science camp doing this kinda stuff too - have a look at Principia Cybernetica for starters.

10:20 / 23.03.07

/... tumbleweed...

So, um, should I start a new thread entitled "Remedial Thread for REALLY stupid Science Questions" or have I stumbled onto the 21st Century's version of the Ultraviolet Catastrophe? (I hope it's the latter, cos then I'll be rich and famous)

13:52 / 23.03.07

Well, I'm not smart enough to answer questions about the relative existence of photons. I have a feeling if you're talking about things existing in no-time (or without the experience of A first, then B, then C, but just ABC all at once), then you're talking about different perceptions of time-as-dimension, where the viewer is seeing the photon as cross-sections of a string, while the photon is aware of itself in its full stringness, with the past on one end and the future on the other.

But that's just an uninformed hunch.

11:01 / 24.03.07

Okay. I'm going to have to go and do some stringy reading, it seems... Ta!

15:03 / 24.03.07

Sibelian- from the photon's P.O.V. it's acting normally and it's the rest of the universe that is weird. See the twin paradox and http://en.wikipedia.org/wiki/Special_relativity for more details.

15:26 / 24.03.07

Relativity would suggest that time dilation slows down perception of time from the point of view of an observer travelling at relativistic speeds.

I'm not a physics person, and I'm trying to understand how photons could be observers, and now my brain is hurting. According to the same theory you would need an infinite amount of energy to reach light speed also, right? But obviously photons don't have that. I think maybe you're wrongly trying to fit a classicist idea of a photon as a "thing" into a relativistic framework. A photon is light, and so your question "how can the photon happen at all", is really asking "how can light travel at light-speed?", no?

06:59 / 25.03.07

I'm not a physics person, and I'm trying to understand how photons could be observers, and now my brain is hurting.

Mm-hm. So was mine. It doesn't need to have an actual perceptive mechanism for relativity to take effect, though, cos relativity works on clocks moving at high speeds. It just has to be a system going through a series of events.

Unless, grant points out, it's light, which I suppose doesn't need to have an event stream associated with it in its own frame of reference in order for it to "happen", it's a special case. Am I right, grant?

I think maybe you're wrongly trying to fit a classicist idea of a photon as a "thing" into a relativistic framework.

Yes, I was. Photons don't need to experience time, they don't age or change, or if they do change it's only relative to the "observer", I guess...

A photon is light, and so your question "how can the photon happen at all", is really asking "how can light travel at light-speed?", no?,

Not...quite ...

I was getting a bit entangled. I was mulling over it in this sort of way: "Hang on, if photons have no mass and don't exist for any length of *time* then *warg*, what *are* they?" It wan't terribly well analysed thought...

04:01 / 26.03.07

Hmm, if someone would put every possible information in this universe into a single book, what form do you think it would take? It might even be simpler than the universe itself since information can be compressed...

05:53 / 26.03.07

I have the Universe on CD-ROM. It's only about 200Mb...

Kiltartan Cross

13:32 / 26.03.07

Hmm, if someone would put every possible information in this universe into a single book, what form do you think it would take? It might even be simpler than the universe itself since information can be compressed...

The easiest way to represent all information in the universe would be a 1:1 scale model (given that storing the coordinates, momentum and all other gubbins about each particle would take up a hell of a lot more space if it had to be maintained in, say, written or electronic form). Some compression could be achieved, I guess, by removing empty space, and storing a series of large blocks "block one... the Milky Way" "block two... the LMC" and the precise vector between them, so you'd end up with a series of blocks, inside of each of which was a large amount of mass, and a (comparitively) small database of vectors between them.
Of course, "empty" space, intra- and inter- galactic, is far from empty, so it might turn out that you'd need to use a full scale model after all. It depends on whether there are large spaces of truly empty space which could be excised from the model; there probably are some, but the overall gain might be small.

You'd also have to construct the model instantly (which is somewhat unrealistic; the most solidly agreed on figure is more like seven days) and it would instantly become obsolete; it's also a guaranteed fact that any book of the universe would by default contain billions of bookworms...

14:27 / 26.03.07

I was getting a bit entangled. I was mulling over it in this sort of way: "Hang on, if photons have no mass and don't exist for any length of *time* then *warg*, what *are* they?"

I *think* you're venturing into that hazy wave vs. particle thing. In some ways, light acts like it's made of particles, which we call photons. In other ways, it just doesn't -- it acts like a wave. Neither model can tell the whole story.

It's the bedrock of quantum mechanics, and thus a little confusing. Although QM talks about particles with mass as well as weirdy weird photons.

23:10 / 28.03.07

If I roll a six-sided dice six times, what is the probability that I'll roll a 6?

01:12 / 29.03.07

If I roll a six-sided dice six times, what is the probability that I'll roll a 6?

That's equivalent to the probability of not rolling 1-5, and doing that six times in a row, therefore it's 1 - (5/6)^6 or about .665.

07:37 / 29.03.07

The probability that you'll roll one 6, or at least one 6?

08:14 / 29.03.07

Sorry, at least one 6. Although, I now wonder what the probability would be of rolling just one 6 too.

Kiltartan Cross

11:55 / 29.03.07

Being an inherently lazy git, I decided to let QBasic do the hard work for me (and instead of putting any faith in my rusting mathematics). The machine reckons (after a million iterations) that the odds of getting one and only one six are about 40.25%, which seems like a reasonable figure.

12:37 / 29.03.07

Thanks SilconDream and CC. I was just having trouble getting my head around the fact that each roll of the dice is a discrete event (with a 1/6 probability of rolling a 6), but multiple rolls must increase the probability of one of those rolls being a 6. But I couldn’t work out the hows whats and whys.
I should really try not to think about this stuff.

19:28 / 29.03.07

A nice, simple binomial probability calculator

Kiltartan Cross

19:41 / 30.03.07

Would it be possible for a crop of bio-ethanol producing plants to remove carbon from the atmosphere over the course of their lives?

I have the vague impression (garnered from Wikipedia and similar webbage) that plants are net removers of carbon while they're busy grow-ing, but not so when they're grow-n. This sort of implies that a fast growing, frequently harvested crop would be a good thing for removing carbon.

I also have the impression that producing bio-ethanol from crops does itself involve carbon emissions, which could be a drawback (although again trusting W., there's some kind of feedback process being developed which reduces or removes that).

Still - the idea of vast fields of crops, simultaneously providing a fuel and helping save the planet, is very appealing. Anyone know about this kinda thing?

00:50 / 31.03.07

I don't know much, but I imagine (in an extreme example) that if you compare a densely vegetated hardwood jungle to the same area of maize which is burnt and re-planted yearly, it is the latter that will keep more carbon in the atmosphere.

I will try to track down some links in the morning.

Kiltartan Cross

20:46 / 31.03.07

I'm not sure... ...but I guess there's plenty of rapid growth going on in a jungle, and a jungle is probably a lot more efficient (~100%, I suppose) at soaking up incident sunlight than a field of crops. That said, it's not a given (ok, maybe that's a little naïve) that bioethanol crops replace jungle, I hope.

00:12 / 01.04.07

Yes, the jungle was an extreme example. But think about it. The carbon that's in plants is the "sink", right? Whatever about fast/slow growth (and I would say maize is faster than a tree), a jungle will have more biomass per unit area, and so will be a better sink.

Separate to that is the growth and death rate. Growth takes carbon out of the air, death puts it back in (probably via the soil). If you have a field of maize (or a jungle for that matter), and you burn it and re-grow it once a year, then on average over a year, that carbon is effectively in the air maybe half the time, increasing the greenhouse effect.

So it's not only the size of the sink that matters, but whether there's rapid turnover. So it's complicated.... In fact, if you think about it - if there was fast death and fast growth, but a long period of decomposition, then you would see the soil acting as a sink for the carbon. This is how bogs/peat/coal/oil come about, I suppose - when geology overtakes the rate of decomposition.

However, for biofuels the "decomposition" stage is artificially increased to a maximum. The fermentation tanks, the fuel depots will act a sinks for a little while. But that carbon in the plants is put into the atmosphere at the same rate (over a year) that it is taken out of the atmosphere by plants - it has to be so, for commerical reasons. So these are only part-time sinks. Which is even worse if you've cleared larger carbon-sink vegetation to grow them.

jentacular dreams

08:46 / 01.04.07

Agreed, though the organic carbon in soil is easily oxidised above 25C (which is why cleared tropical forest only yield god crops for a couple of years). Growing forests are the best manageable sink, as they lock up a lot of CO2 and hang onto it for a good period (a good argument for using pine wood instead of synthetic materials when possible).

Obviously, given it's size, the ocean would be the optimum carbon sink, especially given the increasing CO2 content hasn't really affected it's pH yet. However, worryingly this is because sea water has a buffering capacity (7.5-8.4). When the amount of carbonic acid [CO2 in the water] exceeds this capacity, the pH will drop suddenly, causing the majority of organisms to die and begin to decompose, producing more and more carbonic acid. Also, as it is a carbonate-bicarbonate buffer, the introduction of noncarbonic acids causes the release of CO2 from the oceans into the atmosphere. And the amount of CO2 the ocean (and it's buffering system) can hold is also temperature dependant, as the heat rises, the capacity falls.

Kiltartan Cross

14:47 / 01.04.07

Gotcha, RC and the bees; I hadn't thought about it in terms of sinks, and that makes it a lot clearer. Thanks.

18:28 / 03.04.07

What would be the theoretical minimum number of people needed to survive space travel then establish a colony on another suitable planet, if such a thing were to exist?

18:28 / 03.04.07

(I'm aware it's a really odd, 'ballpark' question, so I'll probably appreciate reasoning rather than figures, if that makes sense?)

18:40 / 03.04.07

I don't know how scientific it is, but from a sci-fi standpoint, I've heard around 500-800 people are needed to ensure a viable population. Maybe less, if there's a sperm and egg bank.

11:05 / 05.04.07

What would be the theoretical minimum number of people needed to survive space travel then establish a colony on another suitable planet, if such a thing were to exist?

The Toba Catastrophe Theory reckoned that the human population got knocked down to as little as 1000 breeding pairs during a super-volcanic event about seventy thousand years ago. (However, recent advances in our understanding of our species' genetic history have weakened this theory somewhat).

jentacular dreams

11:25 / 05.04.07

Surely that would result in a large number of small populations (probably well below 50 people per group) spread over a large area?

What kind of timescale are we talking about for a 'viable population'? If new individuals were to arrive sometime within the next hundred or so years, couldn't the initial population be much smaller? If so, then the minimum number of people would be more determined by technical needs (engineers, doctors, teachers) etc. of the colony?

12:45 / 05.04.07

Surely that would result in a large number of small populations (probably well below 50 people per group) spread over a large area?

There may well have been other groups that survived the event, however they were (presumably) below the threshold for a sustainable population and died out after a few generations.

The 1000 odd breeding pairs (and this estimate has been suggested to have been as high as 10,000) would have constituted the largest surviving group after the event.

13:57 / 05.04.07

I have a vague memory of reading an answer to this question, possibly in the form of a science fiction story, in which the limit to how many people could viably colonize depended on how willing/able families would be to tolerate tightly arranged marriages for several generations (a son from this line had to marry a daughter from that line and have two children, that kind of thing) and possibly some other non-traditional arrangements (I think polyamory was part of it, too).

14:19 / 05.04.07

Does poly give the best genetic mix or does it introduce more potential problems into the future generation? I'm wondering in terms of poly gen 3 having to track half siblings and close cousins.

jentacular dreams

14:49 / 05.04.07

Well, in a way, wouldn't poly make everyone related, but faster? It's a faster means to poulation growth (in the absence of other limiting factors), but as for creating more genetic diversity, I'm far from sure.

15:30 / 05.04.07

If a gun was hidden inside a pot of paint containing lead, would it be concelled from x-rays?

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