It's been well over 72 hours and ainwood hasn't asked another question, so...
What is photoperiodism?

Does it have something to do with how animals and plants sense the change in time/daylight?

It defines the direction of the movement of this:
http://blog.rac.me.uk/photos/weeble.gif

EDIT: did I win? did I win? I surely must have...Sorry, no. :p

Very basically, it is a measure of the interchangeability of gas - a gas appliance will be rated to take gas with a certain wobbe range. It can burn any gas within this range, without concerns of flame lift-off / sooting / lightback etc.

It's been well over 72 hours and ainwood hasn't asked another question, so...
What is photoperiodism?

Does it have something to do with how animals and plants sense the change in time/daylight?

Yeah, that would be my guess. The reason why we feel sleepy when it's dark.

Photoperiodism: It's a pretty interesting constant, it's a ratio of no. of pictures posted in the net Pn and one's age a. In short

Pn/a=constant

Does it have something to do with how animals and plants sense the change in time/daylight?
No, but your on the right track.

How plant grow towards light? (Complete guess)

How plants regulate their growth and dormant seasons?

The way plants switch from photosynthesising during the day and respiraation at night?

The fact that our waking/sleeping cycles are influenced by the amount of light we experience & that the timing can be changed by long-distance travel/working conditions etc?

Photoperiodism is the response of plants to the length of daylight. In some plants (deciduous trees, for example), decreasing length of day results in the onset abscission - when the leaves start to change color and fall to the ground. Photoperiodism is also responsible for a plant's awakening after the winter and sprouting in the spring. It's essentially the way plants know what time of year it is by registering the changing length of day as the year progresses.

Photoperiodism is the response of plants to the length of daylight. In some plants (deciduous trees, for example), decreasing length of day results in the onset abscission - when the leaves start to change color and fall to the ground. Photoperiodism is also responsible for a plant's awakening after the winter and sprouting in the spring. It's essentially the way plants know what time of year it is by registering the changing length of day as the year progresses.
You got it!:goodjob:

Well, I got it before - but not in as many words :) (check post #508)

Yeah - I thought Aaglo had the essence of it.

I can't think of a question right now, so if Aaglo can think of one before I do, the question is his :)

Okay, this is pretty simple - and maybe a bit on the easy side too :)

What is invar?

a finnish word meaning:

"Nokia is the best brand of cellular!!! There's no Ifone or Hiphone version of the N95!!!"

Its a nickel-zinc alloy thats used for precision due to its good thermal properties.

stickciv got that right :thumbsup:

Whoever wants to can have it.

What are homeotic genes, what do they do, and what is special about them? Name the genes in bithorax and explain what happens when you knock one out (or down) in Drosophila.

Almost certain they are development genes that regulate signal cascades that help the different regions of the embryonic organism develop into the organism proper. Not going to take a wild guess on bithorax, other than the name implies regulation of bisymmetrical development of the thorax (or mid-section of the insect, IIRC). And another guess that messing up a gene there would probably get some weird deformity like a siamese twin effect, or a total lack of symmetry---either longitudal or in cross section.

I lied---I just made a wild guess ;*).

Has it been 72 hours yet? :p

http://sethandemma.squarespace.com/storage/tumbleweed.JPG
Courtesy of some completely random site.

What's a trit?

3 bits? 7890

Nopes! :(

A "trinary digit"? I.e. like a bit, but in base 3?

A supernumary breast?

A "trinary digit"? I.e. like a bit, but in base 3?:goodjob::)

A supernumary breast?
Yeah, I gotta say, if I were going to name a base 3 unit, I'd call it a "tit". Base 4 would be a "quit", 5 would be a "pit", six a "sit", seven... err... Hmm. Well who the hell would want to count in base 7 anyway?!

EDIT: No! 6 would be a "hit", seven a "sit", 8 and "it", and 9 an "nit".

*opens the floor*

*grabs floor*

We all have heard about the presumed origin of base 10 counting: 10 fingers = 10 digits. Seems pretty cut and dry. In fact, our word digit comes directly from the Latin word for finger.

But how did people develop a base 12 system?

This question is on the speculative side, but I feel confident it falls under the Technology umbrella nonetheless. ;)

I'm guessing because it's divisible by 4, 3 and 2? That might be "why is it useful" rather than "how was it developed" though...

Not really what I was looking for... as I said, this one is a little speculative.

Allow me to rephrase:
It's easy for us to count to 10 on our fingers. Why might it be easy for people to count to 12?

Because some people are still used to using dozens?

Is it to do with time? (e.g. 12-hour clocks)

To be honest, I don't know at what point in history the base-12 system was invented (early civilization? or more modern?) so it might be to do with counting eggs or sheep. The number of toes on a sheep! That's got to be it.

ten fingers, two feet.

12 knuckles on each hand (excluding the thumb)?

Actually, there's good reason to believe that our 12-hour counting system, as well as our 360 degree circle, all are derived from the base12 counting system.

And no, it's not from sheep or feet ;)

Edit: xpost w/ Perfection.

Yes! Taking your thumb, you can touch it to the back of each of the three knuckles on your 4 fingers. Do that on both hands, and you have 1-144 :)

Perfection has the floor :hatsoff:

Phlogiston theory, what the hell is it?

Ooh, ooh, I know this one.

Phlogiston was a substance believed to be contained within all materials that was released upon burning. So basically, it was a 5th element in addition to the 4 classical ones from the greeks.

mmmmmmmmmmmhnmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm

yer go

open floor.

If you want to calculate a position (XYZ) with a GPS reciever, how many satellites do you at least need signals from? And why is that?

3, to give you at least 2 intersecting lines in each plane of space.

I was hoping someone would answer that. ;) It's the right way of thinking, but it's not the correct answer.

If you want to calculate a position (XYZ) with a GPS reciever, how many satellites do you at least need signals from? And why is that?

It's a triple integral, does that answer your question. ;):)

4 because it's a (x,y,z,t) calculation that needs to take into account special and general relativity to give a precise reading. x,y,z technically needs two and some trig, although a third would help as would a forth, time needs 2 and position from 2 and some less than obvious maths. So four.

To put it in laymen's terms the measurement needs four variables, dependant and independent and thus 4 satellites to be accurate.

Yes, very good! :goodjob:

One for the mathmos and physics bods/engineers.

What is this equation useful for and how is it possible to get a general or "indefinite" integral from it? Or at least an integral within infinite limits.

http://www.freewebs.com/mypicturesandsht/1688936%2D0.png

And I want all working and the sort of physics it's used in.

Should be quite easy for anyone who's done a degree. :p

This brings me all the way back to A-level maths. It's something like -ax2e^-ax^2.
As for the physics, not a clue.

What is this equation useful for

It's not an equation because it hasn't been set equal to anything. :p

It's not an equation because it hasn't been set equal to anything. :p

It's an integral, it involves relating one value to another, in this case it is equal to the area under the curve of the graph of e^(ax^2). it is also an equation because it is related to something in physics. That's all I can say without giving it away, it's a model thing.

This brings me all the way back to A-level maths. It's something like -ax2e^-ax^2.
As for the physics, not a clue.

That's incorrect, I presume you either tried substitution or by parts, neither of which will yield an answer. Basically this is something you either know or you don't. If you know it it's obvious.

It isn't possible to integrate that function analytically -- it's the normal distribution (or rather the form of the normal distribution), and, IIRC, integrates between -inf and +inf to sqrt(pi/alpha) or something like that.

It's also used in QM, IIRC... Eq'n of a wavefunction or something... don't hold me to that :p

EDIT: It's something like, if the wavefunction is Y=Y(x), then the probability that the particle lies within the region a to b is integral of Y^2 between a and b. The eq'n of a wavefunction is smth like Y=exp(i.lamda.x), where lamda is the wavelength. Y^2 is therefore exp(-lamda^2 . x^2), or exp(-alpha.x^2), where alpha = lamda^2. Again, don't hold me to that.

EDIT2: No, wait, it's not lamda, cos then the units dont match up, it must be the spatial frequency, i.e. 1/lamda -- the wavenumber or something? God I can't remember... But the symbol is k. So it's Y=exp(i.k.x).

EDIT3: Yes, that definitely rings a bell... exp(i.k.x)... And then alpha = k^2

Has it something to do with Fourier-transforms? That's where I remember using e^-ax^2 quite often...

It isn't possible to integrate that function numerically -- it's the normal distribution (or rather the form of the normal distribution), and, IIRC, integrates between -inf and +inf to sqrt(pi/alpha) or something like that.

It's also used in QM somewhere, IIRC... Eq'n of a wavefunction or something... don't hold me to that :p

Kind of it is but you have to do a bit of maths manipulation you're in the right area, it's Maxwell's work and it's used in kinetic theory of gases.


If you have I = e^{ax}dx, then you can effectively get rid of the constant, a, from being inside the integral, by simply substituting for, say, t = ax. Differentiating this, we get dt = a dx. Rearranging, therefore dx = dt/a. Substitute in the integral, for ax, and dx, and we now get,
I = (e^{t}dt)/a .We divide I by the factor a, but a has now come outside the integral of (e^{t}dt) . We can do a similar substitution for pretty well any integral.So in general, if I = f(ax)dx, where f is some function, then I=(f(t)dt)/a .

Given that you should be able to solve it with the double integral to polars method for e^(x^2) with the constant outside the integral and it is equal to1/2*sqrt(pi/a).

Close enough, I wouldn't expect anyone to remember that. :) And you'll only find it in text books. It's not soluble technically with elementary functions, but you can fenagle a "general" solution.

Has it something to do with Fourier-transforms? That's where I remember using e^-ax^2 quite often...

It can do. it's a fairly general equation.

It's an integral, it involves relating one value to another, in this case it is equal to the area under the curve of the graph of e^(ax^2). it is also an equation because it is related to something in physics. That's all I can say without giving it away, it's a model thing.

Yes, alright, I know what an integral is. ;) But there's no equals sign in it, so it isn't an equation. It's an expression, I guess.

It's also used in QM, IIRC... Eq'n of a wavefunction or something... don't hold me to that :p

EDIT: It's something like, if the wavefunction is Y=Y(x), then the probability that the particle lies within the region a to b is integral of Y^2 between a and b. The eq'n of a wavefunction is smth like Y=exp(i.lamda.x), where lamda is the wavelength. Y^2 is therefore exp(-lamda^2 . x^2), or exp(-alpha.x^2), where alpha = lamda^2. Again, don't hold me to that.

EDIT2: No, wait, it's not lamda, cos then the units dont match up, it must be the spatial frequency, i.e. 1/lamda -- the wavenumber or something? God I can't remember... But the symbol is k. So it's Y=exp(i.k.x).

EDIT3: Yes, that definitely rings a bell... exp(i.k.x)... And then alpha = k^2I think it's the abs|psi|^2 of the ground state for a one dimensional SHO. Could be wrong though

I think it's the abs|psi|^2 of the ground state for a one dimensional SHO. Could be wrong though
Yeah, you're right. And for any other energy level "n" you just stick that into the exponent, i.e. Y=exp(i.n.k.x). It pops out of the boundary conditions of the wavefunction (i.e. you have to have a whole number (n) of waves between the boundaries of the potential well).

PS. I'm using Y cos in my head it looks like a psi :p

@Sidhe: I'm fairly certain that the integral cannot be solved analytically. It can be solved numerically though, and the integral between -inf and +inf comes to a "nice" number. It's basically the normal distribution, for which the solutions and integral between any two arbitrary points are well known.

Yes, alright, I know what an integral is. ;) But there's no equals sign in it, so it isn't an equation. It's an expression, I guess.

It models something it is equal to something, I just couldn't tell you what that was without giving it away. :p

Like I said Mise it isn't technically soluble but you can get an answer. And that is the answer given by the text book, I know it's not very satisfying, but then technically the solution is a derivation of the error function anyway. That's physics for you though, even if it isn't technically soluble in elementary functions it is wangleable.

I guess it's my turn...

What does it mean for an operator to commute?

I guess it's my turn...

What does it mean for an operator to commute?

Well I've just done one but that's to do with certain things like charge and other forces in tensors and matrix maths is it neutral or charged, but purely in maths it just means AxB=BxA.

Well I've just done one but that's to do with certain things like charge and other forces in tensors and matrix maths is it neutral or charged, but purely in maths it just means AxB=BxA.
Yup, that's correct. Guess it's one of those things that you either know or don't... silly question I guess :)

Yup, that's correct. Guess it's one of those things that you either know or don't... silly question I guess :)

I shouldn't know it it's degree level stuff really, but I happened to be reading about it recently, it's just like my first question. I leave the field open anyway. :)

What was the Staffelwalze (Stepped Reckoner)?

Its a 17th century mechanical calculator that was the first to be able to do all 4 arithmetic operations (They have a model and a description of it in the nearby Computer Museum)

Yup, designed by Leibniz.

edit for bottle

Easy one: who invented the light bulb. :)

The first glass "enclosed" filament bulb to be more precise I suppose.Oooo. QI - alert !!

(I read on this just a couple of weeks ago and it's not Edison. Can't remember who it was though)

Though shalt not take the name of Stephen Fry in vain.

James watt?

EDIT: just checked, and nope...

I predict that someone will say Edison and make themselves look like a right plum. :)

Although Edison is credited with tons of inventions, most of them were actually developed by people working for him (http://en.wikipedia.org/wiki/Edison#Menlo_Park).

The first invention of the light bulb was nothing to do with Edison IIRC, he just produced the first commercially viable version.

If Mise says Marconi I will kill him!

Marconi ?

:ar15: Mise.

Sorry You know the rules. :rolleyes:

Well I have no idea, so I'm just going to list everyone I know who did stuff with electricity :p

Ampere, Maxwell, Faraday, Telsa, Ohm, Henry, Joule, Volta... k can't think of anyone else :p . It was probably later than these fellows anyway though.

Oi, while I was going to open the floor since I couldnt think of anything, you have to respect the rules Sidhe. it was not your turn.

Well I have no idea, so I'm just going to list everyone I know who did stuff with electricity :p

Ampere, Maxwell, Faraday, Telsa, Ohm, Henry, Joule, Volta... k can't think of anyone else :p . It was probably later than these fellows anyway though.

I'm warning you, you're already due assassination, don't make it worse for yourself! :mad:

If you're going to leave posting a question for 4 hours, then what would you expect? We haven't got all day and in the mean time, not everyone runs on yank time. So while were waiting I thought why not? And besides I thought this one would take 2 seconds, but it's obviously not as well known as I thought.

Rules schmulez anyway, if you aren't going to post a question for ninety seven hours then it should be common courtesy to just yield. In fact it should be one of the rules.
The rules give me 72 hours and I was thinking of one. If you can't play by the rules, dont play at all.

The rules give me 72 hours and I was thinking of one. If you can't play by the rules, dont play at all.

Stop being such a baby. Ok in future I wont play sionara. :rolleyes:

72 hours what fool came up with that?

I didn't read the rules anyway, and frankly if there that stupid then there's no point in me playing.

Honestly 72 hours? Anyway deleting my question so stickciv doesn't have a paddy on me.

Stop being such a baby. Ok in future I wont play sionara, :rolleyes:.

72 hours what fool came up with that?

I didn't read the rules anyway, and frankly if there that stupid then there's no point in me playing.


The OP came up with those rules, and frankly, they're a lot better than letting it be a free-for-all.

Maybe in the future, read the rules. It might just be the smart thing to do if you have no idea whats going on.

Stop being such a baby. Ok in future I wont play sionara. :rolleyes:

72 hours what fool came up with that?

I didn't read the rules anyway, and frankly if there that stupid then there's no point in me playing.

Honestly 72 hours? Anyway deleting my question so stickciv doesn't have a paddy on me.

They are quite clearly written in the OP. It's the same format the History Quiz uses, invented by Knight-Dragon, I think, and it works very well there. It's only fair that if you answer a question correctly, you should get to ask the next question, and as you say, not everyone runs on 'Yank Time', so we have to take timezones into account. Just be patient.

As for the light-bulb, was it Joseph Swan?

They are quite clearly written in the OP. It's the same format the History Quiz uses, invented by Knight-Dragon, I think, and it works very well there. It's only fair that if you answer a question correctly, you should get to ask the next question, and as you say, not everyone runs on 'Yank Time', so we have to take timezones into account. Just be patient.

As for the light-bulb, was it Joseph Swan?

Well I didn't read the rules and they are stupid. So yes it's Swann but I would of also of taken A Scotsman who's name mysteriously eludes me now. Still since I am not allowed to play and that question is redundant I'm going to sulk in my room. :(


72 hours is a joke but no ones forcing me to play so there we go. Like he said if you can't play within the rules don't play. In that case no I can't because they suck. So I wont. :lol:

The OP came up with those rules, and frankly, they're a lot better than letting it be a free-for-all.

Maybe in the future, read the rules. It might just be the smart thing to do if you have no idea whats going on.

They suck. They suck. They are stupid and no one is suggesting a free for all, but on a forum with a high turn around 72 hours is preposterous quite frankly. Whenever I ran comps I just left it for 12 hours or less depending on the situation and then opened it up again. Keeps it moving, otherwise its just a snails crawl.

Like I said though, me not agreeing with the rules shouldn't stop anyone else from playing, but have fun with that and gl, I'll be elesewhere *takes football* and storms off the pitch :cry:

Uhh, alright then, Sidhe, always good to hear from you. :confused:

Let's just get on with a question.

In cosmology, what is Ω, and what effect will its value have on the fate of the universe?

Uhh, alright then, Sidhe, always good to hear from you. :confused:

Let's just get on with a question.

In cosmology, what is Ω, and what effect will its value have on the fate of the universe?

:lol: don't worry I was only joking. ;)

It was just his tone as if I'd stolen his lunch money and punched his gran. :D

I should know that? But I don't. I'll take a guess that it is the point at which the universe becomes too diffuse to support chemical/nuclear reactions.

Or to put it better the point of death, before the final heat death or maximal entropy?

No, my tone was of annoyance at you being ignorant and egoistical about not reading the rules. I dont care if they suck in your opinion, they have worked fine so far.

As for what Omega is in cosmology, it refers to the density of the universe.

No, my tone was of annoyance at you being ignorant and egoistical about not reading the rules. I dont care if they suck in your opinion, they have worked fine so far.

As for what Omega is in cosmology, it refers to the density of the universe.

Egotistical, you mean saying the rules or should I say 1 of 10 are are garbage is egotistical, btw that's the only thing I was being serious about, because that is stupid, but hey it's not my gaff.

Yeah ok. pffft, stop whining at me, Christ I deleted the question didn't I? Is it your time of the month? is that what it is?

Anyway I looked it up on Google and that is essentially correct, you forgot to answer what it means to the eventual fate of the Universe though.

EDIT: Oh and retrospectively I really did know all that off the top of my noggin, I assumed you weren't allowed to use Google as that would be absurd; it's all basic physics, well the satellite thing isn't but it comes up all the time when people ask for proof of SR and GR so I must have said that crap about a hundred times on another forum by now. And that stuff about maths there is all out of an email I got recently from a friend + my own work to some small extent. The bulb thing is from another thread n another forum too, plus it comes up all the time.

Just in case anyone thinks I cheated. :p

Is Ω a measure of topological flatness, with a value on one side of 1 indicating big crunch and the value on the other side indicating ug freeze?

Because I'm an uneducated peon, I don't know what 'topological flatness' or 'ug freeze' are, but Perfection's answer combined with stickciv's seems correct.

Ω is the ratio of the total density of matter in the universe over the 'critical density' needed for a flat universe (which will decelerate but not recede). If Ω<1, there is not enough matter in the universe for gravitation to overcome the expansion, so there will be an 'open universe' which will keep expanding forever. If Ω>1, there is enough matter to cause the universe to stop expanding and then recede, causing the 'Big Crunch'. This is a 'closed universe'. And if Ω=1, that's a flat universe.

Perf and stickciv can now fight to the death for the right to post the next question.

I'll give it to stickybuns, he earned it beforehand, and it was cruelly denied to him.

I'll give it to stickybuns, he earned it beforehand, and it was cruelly denied to him.

Hey don't cast me as the bad guy he was right just not perfectly right. :p

Let him go, seems like an equitable conclusion?

Topology is just a fancy word for shape in this case, or the sacred geometry of space time, ug freeze God knows. ;)

Glad I missed most of this vitriol. :rolleyes:

But I'd say that if Sidhe has such a problem with the stated 72 hour rule, he should start his own Quiz thread with rules that he likes :)

And I don't think anyone made an accusation of cheating. Did I miss something? :hmm:

[/OT]

It's interesting that Omega is the symbol that was chosen to represent a variable that determines the end of our Universe :worship:

Glad I missed most of this vitriol. :rolleyes:

But I'd say that if Sidhe has such a problem with the stated 72 hour rule, he should start his own Quiz thread with rules that he likes :)

And I don't think anyone made an accusation of cheating. Did I miss something? :hmm:

[/OT]

It's interesting that Omega is the symbol that was chosen to represent a variable that determines the end of our Universe :worship:

I see irony is wasted on you. But no that's not what I was trying to say and nm. :p

Well I didn't read the rules, I just assumed them, so to make sure I know the basics of this guff, being as I have a few posts on this forum, and because these days everything I say is over analysed to the point of trolling, I clarified.

Alright, since I was reading about these not long ago:

What is a HEAT round and how does it work? (Oughta be easy enough)

It stands for High Explosive Anti Tank.

I believe that when it hits its target, its explosion is hot enough to liquify metal, that is then propelled through the armour of what it hits.

High Explosive Anti-Tank round. With a shaped charge, the round creates a blast that penetrates the armo(u)r by directing the explosion towards the armo(u)r.

Edit: xpost. I'll leave it up anyways.

It stands for High Explosive Anti Tank.

I believe that when it hits its target, its explosion is hot enough to liquify metal, that is then propelled through the armour of what it hits.

High Explosive Anti-Tank round. With a shaped charge, the round creates a blast that penetrates the armo(u)r by directing the explosion towards the armo(u)r.

Edit: xpost. I'll leave it up anyways.

You're both correct on the name, but not on how it works. Not quite right at least.

Aren't they the missiles that use a high explosive warhead to drive a high density (DU) penetrator through armour?

I thought that HEAT rounds have a rod of solid copper running down the axis, and when the round contacts the target, the temperature is high enough that the copper liquifies and bores through the armor plating. This is in contrast to a depleted uranium round, which remains solid.

But I may be way off - this really isn't my cup of tea, for I'm really a pacifist at heart; I loathe the enormous amounts of effort humans invest in killing eachother :p

Aren't they the missiles that use a high explosive warhead to drive a high density (DU) penetrator through armour?

I think you're the closes we're gonna get.

What happens is the explosive charge detonates a few inches away from the armor and compresses a metal liner into a solid jet of metal. This jet, traveling at around Mach 25 then punches through armor.

You're up brennan

Open floor.

226^32 + 835^26 = 2026^23

Explain why the above can't be true.

Can the sum of two 'powers' never equal a number which has a lower power? (You know what I mean.)

Nope, that's not what I was after. It might have also been true though, so I checked, and after some random guesses, I found a counter-example: 2^4 + 2^7 = 12^2

Ah, hold on, is it because 835^x will always end in 5, and 226^32 and 2026^23 will always end in even numbers, but an even plus an odd will always make an odd, so 2026^23 can't be the answer?

Just as additional point, Cat was alluding to Fermat's Last theorem, however that only holds when all the powers are equal (and greater then 2). Cat has a good method of ruling it out anyways though.

226^32 is an even number
835^26 is an odd number
The sum of an even and odd number is an odd number but
2026^23 is an even number

EDIT: Beaten by a cross post

Yup! even*even*... + odd*odd*... = odd, so the RHS can't equal the LHS. I didn't think of the 835^x ending in 5, but yeah, same thing :)

Catharsis is up.

EDIT: 2x x-post

I have to sleep, so open floor. Ozbenno can take it if he so wishes.

What's this formula more commonly known as...

http://img100.imageshack.us/img100/8840/cfcyf9.png (http://imageshack.us)

Am I allowed to answer, since I asked the last one? I'd open the floor anyway, but if someone else knows I'd rather they answered...

EDIT: I won't bother :p

Hiesenberg's

OPEN FLOOR

You could at least spell Heisenberg correctly. :p

That would require a net search.

Open floor, eh?

:hmm:


We all know that the USA is the only nation to have used nuclear weapons. Hiroshima and Nagasaki were the targets, Fat Man and Little Boy were the gadgets.

Which bomb was detonated over which city, and what is the essential difference between the two?

As stated before, I'm a pacifist - but I can't help be fascinated by humanity's ingenuity in this arena - I suppose it's like a car accident on the highway, where you just can't help but look ;)

Little Boy was over Hiroshima, Fat Man over Nagasaki.

The Little Boy was a gun-type bomb, it fired a subcritical bullet of Uranium at another Uranium target which caused the two to hit critical mass and begin the reaction.

The Fat Man on the other hand was an implosion plutonium bomb. It used shaped charges to compact a chunk of plutonium enough to explode.

Open Floor as well

What are hox genes, and what is so special about the order in which they are activated? (I'm adamant that someone must know this even though it's similar to my last one :p)

Thanks for opening the floor, StickCiv - I thought I was going to be home last night ;)

Hox Genes:

Hox genes control how cells differentiate themselves into different tissue depending on their location. For instance, they control the way a cell in an insect's thorax knows to start growing like a leg as opposed to an antenna or wing.

The activation order is critical to establish the proper gradient for that part of the body; mess around with order, and you may get a leg where there should be an antenna.

Hox Genes:

Hox genes control how cells differentiate themselves into different tissue depending on their location. For instance, they control the way a cell in an insect's thorax knows to start growing like a leg as opposed to an antenna or wing.

The activation order is critical to establish the proper gradient for that part of the body; mess around with order, and you may get a leg where there should be an antenna.

I'm looking for a little more detail on the activation order. Think about the order on the DNA.

If it's not answered by tomorrow then peter grimes can ask the next one.

The answer that I was looking for the second part was that the order that the Hox genes are on the DNA corresponds to where they are expressed in the anterior-posterior axis.

Hox genes define boundaries in animals. Mutants can cause a change in what each segment becomes. For example, in Drosophila, ultrabithorax has 2 sets of wings instead of one, and antennapedia has legs instead of antennae. Pretty nifty, eh?

peter grimes is up next.

This is stolen from a Car-Talk puzzler. I never heard the answer(s), but I'm fairly confident in the one I came up with:

The Moon's force of gravity is 1/6th that of Earth's. So if I weigh 100kg here, I'd only weigh 17kg on the moon. What actually would weigh more on the moon than it does here on Earth?

Something more massive than the Earth itself?

Is this a trick question?

A helium balloon would certainly register more on a set of scales on the Moon than on Earth.

Also kg is not a unit of weight

Is this a trick question?

A helium balloon would certainly register more on a set of scales of the Moon than on Earth.

Also kg is not a unit of weight
Cunning.....!

If something weighs 100 kg and earth and something else on the moon weighs 17 kg on the moon, then the thing on the moon actually has a higher mass. :mischief:

Actually, ainy if something weighs kilograms, then it probably spans liters, and has a lifespan of Hertz. :crazyeye:

Actually, ainy if something weighs kilograms, then it probably spans liters, and has a lifespan of Hertz. :crazyeye:
...Which is kind-of my point.

I just don't see too many bathroom scales measuring Newtons.

I was stating it in a sillier less subtle way.

Okay - I guess I should have left off the units... :blush:

a Helium Balloon is indeed the answer I had in mind. I was really curious to see if there would be any other possible answers!

Truronian has the floor :thumbsup:

Q:

What is the Moho and when will we get there?

In the borehole pressure mines 100km beneath Planetsurface, at the Mohorovicic Discontinuity where crust gives way to mantle, temperatures often reach levels well in excess of 1000 degrees Celsius. Exploitation of Planet's resources under such brutal conditions has required quantum advances in robotic and teleoperational technology.

Morgan Industries, Ltd.
"Annual Report"

I will accept that in lieu of a more encompassing answer because SMAX is awesome.

Perfection is up.

OPEN FLOOR

The "when will we get there" was a reference to this (http://en.wikipedia.org/wiki/Chikyu_Hakken) cool sounding project which should be done in 2012.

Give a simple example of how cartesian geometry can't describe the universe. It must involve triangle, sum of it's angles and a sphere...

A triangle on a sphere could have three right angles. For example: you're at the North Pole. You travel one mile south, then one mile east, and finally one mile north, ending up back where you started. So, you've travelled for three straight lines, but because you made a 90 degree turn each time, the sum of the angles is 270 degrees. (Actually, the one at the north pole might not be 90 degrees, but the sum would be more than 180.)

Is that what you wanted?

Probably but that's only because of the 3D nature of a sphere, it's hardly particularly surprising. That said it's obviously true so I can't see why that would be wrong.

I can give you an example without triangles per se, I could do you a spherical object, the curvature of space time and gravitational account incorporating motion and gravity into the theory, with a triangular trajectory. :) Quantum theory and gravity. ;)

Catharsis is up...

Sidhe, I was asking about euclidian geometry (which is Geometry of plan, at least, it's how we explain it in school here in France) and a simple example.
Curvature of space time and gravitational account incorpating motion and gravity into the theory is not a simple exemple.

even simpler than catharsis: Take an orange (a sphere), cut it in halves, then in quarter, finally in 1/8. Take the skin of 1/8 off. It's a triangle with 3 right angles.

I know what he was talking about, but since the curvature of space time is of similar geometry to any curvature, at least at face value, it's another answer. Obviously the answer you were looking for had already been given, so there was no point reiterating that.

Catharsis is up...

Sidhe, I was asking about euclidian geometry (which is Geometry of plan, at least, it's how we explain it in school here in France) and a simple example.
Curvature of space time and gravitational account incorpating motion and gravity into the theory is not a simple exemple.

even simpler than catharsis: Take an orange (a sphere), cut it in halves, then in quarter, finally in 1/8. Take the skin of 1/8 off. It's a triangle with 3 right angles.Well, the issue here is that this sort of relationship can be explained with Euclidian geometry. In doing so we deny that the region of the shpere's surface constructed by the three arcs is in fact a triangle, but we can explain all the angles and can calculate new angles and ac lenghts given sufficient knwoledge about other arc lengths and angle lengths. Certainly using noneuclidian geometry can be better at framing the problem, but the problem can be completely solved using Euclidian geometry.

It's only when we get into relativity does noneuclidian geometry truely stick out as being neccesary to phyisically understand the nature of space and time.

even simpler than catharsis:

Oi. :gripe:

That said, I can't think of a good question, so: OPEN FLOOR

Why isn't the twins paradox a paradox? For those who know nothing about physics it's Einstein's contribution, and has to do with special relativity. Bonus points for any answer involving the maths. :)

Well, the issue here is that this sort of relationship can be explained with Euclidian geometry. In doing so we deny that the region of the shpere's surface constructed by the three arcs is in fact a triangle, but we can explain all the angles and can calculate new angles and ac lenghts given sufficient knwoledge about other arc lengths and angle lengths. Certainly using noneuclidian geometry can be better at framing the problem, but the problem can be completely solved using Euclidian geometry.

It's only when we get into relativity does noneuclidian geometry truely stick out as being neccesary to phyisically understand the nature of space and time.

well, it all depend on how you define triangle in euclidian geometry.
Here in France, euclidian geometry is taught in a way that:
A surface defined by 3 angles is a triangle.
and the sum of a triangle's angle is 180°

the trouble comes from euclidian geometry is geometry of plan and the triangle i defined can't be comprised on an euclidian plan.
Of course you can define the same physical object in euclidian geometry, but it won't be recognize as a triangle.

IIRC, in euclidian geometry, a sphere is just the assembling object of circles in all possible plans. By cutting it with 3 plans, you get the same object, but it's a sum of arcs, not a triangle...and everybody here can see it's a triangle!!!

To Catharsis: a used the term simpler where i should have used easier, because it's easier to cut and unskin an orange than to get to the pole !!!

Soidhe, IIRC it basicly has to do with the Inertial reference frame supplying a common frame )general relativity) to the two twins, so that it is the traveling one that experiences time dilation.

well, it all depend on how you define triangle in euclidian geometry.
Here in France, euclidian geometry is taught in a way that:
A surface defined by 3 angles is a triangle.
and the sum of a triangle's angle is 180°

the trouble comes from euclidian geometry is geometry of plan and the triangle i defined can't be comprised on an euclidian plan.
Of course you can define the same physical object in euclidian geometry, but it won't be recognize as a triangle.Well that just becomes a semantic issue (what you call a triangle), Euclidean geometry can fully explain everything in this situation just as much as noneuclidean can, only the wording and perspective are different. I don't see how not calling something a triangle constitutes a failure of descriptive system.

Soidhe, IIRC it basicly has to do with the Inertial reference frame supplying a common frame )general relativity) to the two twins, so that it is the traveling one that experiences time dilation.

Indeed. It therefore follows that one twin ageing more slowly than another is not a paradox, it's a prerequisite of time dilation in special relativity between frames of reference.

As for the maths question it sounds like me to be the difference between the sort of maths you learn at a college/pre-university level and that which you learn as a University student. In other words there are few things that cannot be described by Euclidian geometry in a pure form, but since the Greeks derived a sort of integral for describing a sphere in terms of 4/3*pi*r^3 long before Newton's calculus I'm sure they were well aware of how to infer distance on global objects, and a triangular path, using as noted arc lengths and radius, since quite patently the circular relationship obviously can be applied to a sphere with some adjustment, which notably is an integral of the surface area of a sphere which in turn is related by some maths to the area of a circle. I forget how the Greeks did it but essentially it was by dividing it up into sections and then deriving the whole from that, which is integration without the formalism.

Well that just becomes a semantic issue (what you call a triangle), Euclidean geometry can fully explain everything in this situation just as much as noneuclidean can, only the wording and perspective are different. I don't see how not calling something a triangle constitutes a failure of descriptive system.

so again, it's a semantic issue...

By using "can't describe the universe", i was refering to the fact that euclidian geometry can't recognize an object as it is (here the triangle).
As I said, here in France, and that's something that can have a lot of impact, a triangle is: the surface defined by 3 angles.

The object i describe is a surface defined by 3 angles, so it's a triangle, but not in euclidian geometry...

You can continue nosepicking, but this little "fight over Euclide" just prove the importance of hypothesis and axioms. the ones from Euclide are good for everyday, but are limited.

so again, it's a semantic issue...

By using "can't describe the universe", i was refering to the fact that euclidian geometry can't recognize an object as it is (here the triangle).

The object i describe is a surface defined by 3 angles, so it's a triangle, but not in euclidian geometry...

You can continue nosepicking, but this little "fight over Euclide" just prove the importance of hypothesis and axioms. the ones from Euclide are good for everyday, but are limited. But it can describe the entire situation, it just doesn't use your definition.

Also open floor.

I think there's a sort of strange justice here, since the real "non-Euclidian" answers have gained the right to post the questions. Perfection is next.

Even in Euclid's time it was no doubt possible to derive the angles on a sphere from Euclidean geometry but since you asked only about it in terms of triangles, not circles then the first answer was correct, even if such things are easily derivable from basic geometric principles. With the advent of imaginary numbers and spherical polar co-ordinates, it's simple to work out any position and derive any angle from any formula, that is all a part of Euclidean geometry. Still I think we've nitpicked enough. :D

EDIT: anyone is next. :)

ok: current events then ;)

how large is the largest eye of any species ever found - and what species does it belong to :mischief:

The giant squid recently thawed out in NZ? Size of a dinner plate IIRC.

Giant Squid, a foot, open floor.

edit: frick

The giant squid recently thawed out in NZ? Size of a dinner plate IIRC.

Giant Squid, a foot, open floor.

edit: frick

:yup: Ozbenno is up :)

(actually a Colossal Squid which apparently is something else than a Giant Squid ;) and the eye is 27 cm)

http://msnbcmedia1.msn.com/j/ap/nzl80202220630.h2.jpg

Why don't we OPEN FLOOR it again.

What are the two main tests for TB in cattle, which is better, and why?
(from a recent news story)

well, can you give the meaning of TB for non-natural english speaker, please?

TB = Tuberculosis.

Does the answer involve chucking them on a pyre?

Any answer involves chucking them into a pyre, according to the government.
But we're talking science and technology in this thread, not stupidity.

Maybe I'll go with just one of the tests, if it's explained thoroughly. Best to give it some time though.

Chest x-rays?

by burning them, if it's yellow, they are not affected: if it's blue, they are

By drawning them, if they come back to the surface, they are affected, if not, they aren't...

the best being the drawning, because you can still eat the meat and barbecue is carcinogenic !!!

Nope, none of these. Although LAnkou's ideas seem like an improvement.

Extrapolate from humans...

Blood test? Family history? Biopsy? Skin test? Urine test? Saliva test? Breathaliser? MRI? Endoscope? ECG? Pap smear? Ultrasound? Fine needle aspiration?

...k I've run out of stuff Dr House would do. (Or my parents.)

Blood test? Family history? Biopsy? Skin test? Urine test? Saliva test? Breathaliser? MRI? Endoscope? ECG? Pap smear? Ultrasound? Fine needle aspiration?

...k I've run out of stuff Dr House would do. (Or my parents.)

You forgot lumbar puncture.

You forgot lumbar puncture.
That never seems to do anything though :(

Yes, well done Mise. You got both of them. Now for the rest of the question...

If you tell me which two of those were correct I could come up with convincing arguments for both of them :mischief:

Bah. It clearly wasn't as widely read a news story as I had thought it would have been.

The two answers are a skin test and Ig (blood) test.

That's almost 3 days. Let's have a new question.

Why is high altitude dangerous?

You could fall?

That's almost 3 days. Let's have a new question.

Why is high altitude dangerous?

Low pressure=low oxygen density=lack of oxygen. Can cause pulmonary oedema, causes dizzyness, headaches and lethargy. Is this a trick question, is there some clever answer?

And it's cold.

IIRC this is one of those trick questions...

It's not the fact that there's less oxygen, but the fact that there's less air pressure, which raises your blood pressure, and makes you more susceptible to heart attacks. Something like that.

What was the answer to the last question, Brighteye?

IIRC this is one of those trick questions...

It's not the fact that there's less oxygen, but the fact that there's less air pressure, which raises your blood pressure, and makes you more susceptible to heart attacks. Something like that.

What was the answer to the last question, Brighteye?

Actually that's what generally causes pulmonary Oedema, if he wants to be that specific, I have no idea? That's all I know.

Low pressure=low oxygen density=lack of oxygen. Can cause pulmonary oedema, causes dizzyness, headaches and lethargy. Is this a trick question, is there some clever answer?

That's the one. Low oxygen causes pulmonary oedema and possibly death.

The previous one was the skin test and Ig test; skin test is reliable (although not perfect), and the Ig test is decidedly inferior, with a bad number of false positives because it reacts with Ig from other infections. Farmers apparently get an appeal if the skin test gives a positive, but not from the Ig test.

What is the most toxic substance on the planet, weight for weight?

botox .

botox .

Well botulinus toxin yes. Botox is actually a brand name.

Ok what is the most toxic man made substance? :) Since that one was so very easy. Actually nah if you want to ask a question go ahead.

Well botulinus toxin yes. Botox is actually a brand name.

Ok what is the most toxic man made substance? :) Since that one was so very easy. Actually nah if you want to ask a question go ahead.

IIRC VX holds the worldrecord in nastiness

now for some esoteric stuff - describe the life cycle of the
Lancet liver fluke (Dicrocoelium dendriticum)
:evil:
another possibility would be atleast telling me what makes it so interesting :mischief: :devil:

IIRC VX holds the worldrecord in nastiness

It's actually Dioxin which is about 200,000 times less harmful than what nature can do in the from of botulism. :)

Source. (http://english.pravda.ru/science/19/94/377/15574_dioxin.html)

Dioxin is currently reputed to be the most dangerous toxic poison that has ever been made by the hands of man. It follows two poisons of natural origin: the botulism toxin and the diphtheria toxin. Dioxin is 60 thousand times more toxic than cyanide. A dose of only 50 micrograms of dioxin is lethal for a human being: the volume of the dose can be compared to a tiny microscopic piece of a 50-gram pill, cut into 1000 particles.

It's actually Dioxin which is about 200,000 times less harmful than what nature can do in the from of botulism. :)

Source. (http://english.pravda.ru/science/19/94/377/15574_dioxin.html)

reading up on it: dioxin and vx both have ld50 values that rival each other and depending on which one you use either one is the nastiest one...

reading up on it: dioxin and vx both have ld50 values that rival each other and depending on which one you use either one is the nastiest one...

Well I can only go by what I've heard, and the fact that doing a search on the most lethal man made toxin turns up dioxin? Anyway whatever it appears to have the popular vote, if it is equally toxic it seems to be practically unmentioned on the most toxic front?

oral LD50 of dioxin in rat is 20 µg/kg (http://www.ilo.org/public/english/protection/safework/cis/products/safetytm/toxic.htm) - for VX it is 12 (rabbit) to 40 (human - estimated) (http://www.ehponline.org/members/1994/102-1/munrotable2.GIF)

the difference of course is that dioxin is the much more important toxin being an environmental hazard due to the unlimited idiocy of humans while VX as a chemical weapon is not widely in use - in the end: dioxin is a potent toxin AND a problem - VX is as potent a toxin but not really a problem :)

Back to the question at hand: any takers? need a hint ;)

With those wild and crazy flatworms, it's generally something about how they spend some of their sub-adult life in other critters, usually some kind of sea snail, IIRC.

At least to answer your "What's interesting about 'em"

Most of the flatworms have a larval stage where they develop in some other organism, usually a sea snail, but sometimes I fish, IIRC.



Back to the question at hand: any takers? need a hint ;)

The liver fluke inhabits multiple species of animal depending on lifecycle stage?

oral LD50 of dioxin in rat is 20 µg/kg (http://www.ilo.org/public/english/protection/safework/cis/products/safetytm/toxic.htm) - for VX it is 12 (rabbit) to 40 (human - estimated) (http://www.ehponline.org/members/1994/102-1/munrotable2.GIF)

the difference of course is that dioxin is the much more important toxin being an environmental hazard due to the unlimited idiocy of humans while VX as a chemical weapon is not widely in use - in the end: dioxin is a potent toxin AND a problem - VX is as potent a toxin but not really a problem :)

Back to the question at hand: any takers? need a hint ;)

OK so the whole interweb is wrong on this one, whatever? By the way your second link is not accessible by the plebian.

OK so the whole interweb is wrong on this one, whatever? By the way your second link is not accessible by the plebian.

this is not what I meant - and there is really no need to be offended. Sorry I did not notice the link thing - I just used the first google results for each of them.
Seriously - I was just curious about this coming from a toxicology background and thought I'd share it - but I will stop right here :)



With those wild and crazy flatworms, it's generally something about how they spend some of their sub-adult life in other critters, usually some kind of sea snail, IIRC.

At least to answer your "What's interesting about 'em"

Most of the flatworms have a larval stage where they develop in some other organism, usually a sea snail, but sometimes I fish, IIRC.

The liver fluke inhabits multiple species of animal depending on lifecycle stage?


They do inhabit different species - but that is not really special about them:
they do use two host species (land animals by the way) - with one of them not being a carnivore, yet it eats the other - how do they do that...
Think Futurama :mischief:
http://www.mwctoys.com/images/review_slug_3.jpg

this is not what I meant - and there is really no need to be offended. Sorry I did not notice the link thing - I just used the first google results for each of them.
Seriously - I was just curious about this coming from a toxicology background and thought I'd share it - but I will stop right here :)

I wasn't offended at all, I'm perfectly willing to accept your expertise over the internet, that's what I mean by whatever, otherwise I'd be arguing the toss, I'm just surprised such myths are so widespread on t'interweb. Frankly I know from experience that scientists are more reliable than web sites, unless they are scientific web sites. That's why I was a bit miffed I couldn't read the link to confirm what you were saying. No harm no foul. :)

Oh it's one those that impel its victims to engage in behavior likely to get it eaten.

Oh it's one those that impel its victims to engage in behavior likely to get it eaten.

:yup: - actually I was a tad wrong - they use three species in their life cycle - anyway the bolded part is what I was looking for:


Dicrocoelium dendriticum Life Cycle

The animal in which the adult flukes live is called the definitive host—the host in which the parasite multiplies sexually:

* Adult worms in the liver of the definitive host produce eggs that are washed out in the bile, mixed with the stool, and passed from the body.
* Land snails feed on decaying animal droppings and ingest the eggs, whereupon the eggs hatch, releasing miracidia.
* Miracidia migrate through the gut wall into the snail’s digestive gland, where they multiply asexually. Cercariae are produced. The snail is the first intermediate host for the fluke.
* Cercariae exiting the snail’s tissues are encased in a coating of slime, which is left behind on the vegetation that the snail travels over. Transforming to metacercariaie, the parasites can be very numerous (hundreds in one slime ball) and are protected from drying out by the slime encasing them.
* Foraging ants collect the slime balls and carry them back to the nest, where the slime balls are eaten. Metacercariae encyst in the ant’s body cavity and become infective to the definitive host. One metacercaria travels to the ant’s nervous tissue and encysts there, an event which profoundly influences the ant’s behavior from then on - scientists are still unsure of how this works.
* Infected ants crawl to the tops of blades of grass in the cool evenings and early mornings and cling there. This is the time when herbivores are grazing—the ant’s strange behavior makes the insect much more likely to be eaten by a grazing animal! In the heat of the day, when the dew dries up and animals rest in the shade, the ant that has not been eaten resumes its normal activities, only to ascend again when things cool down.
* Metacercariae in ants that have been eaten migrate up the bile duct into the liver and mature to adult flukes in under two months. At about three months after infection, the worms begin producing eggs.

Is there a (natural) biological urge for an ant to climb to the top of a blade of grass? I.e. is there a reason that an ant would do this naturally?

Indeed I saw it on a Daniel Dennet video, he was using it to emphasise how deadly memes could be. Things that infect people and make them do things they otherwise wouldn't. The ant crawls to the top of the grass and is eaten by the flukes real target or some such I forget how it works exactly.

:smug:PEN FL:smug::smug:R!

Why might breathing 100% O2 be dangerous to patients in intensive care?

Could the sudden surge in O2 put them into shock?

Crap my boss told me why but I've forgotten. :hmm:

It'll make them highly flamable?

Oxidative damage?

The change in pressure causes them to suffocate?

Oxidative damage?

I think it's something to do with high oxidation potentially causing organ failure? Like said some sort of oxidative damage, that rings a bell? Not sure though. :undecide:

Oxidative damage?

Yes, that's certainly one good reason. Other reasons might include a decrease in cerebral perfusion, which is what I was reading about today.

4 days and no question, so I'll make another. What mineral is added to paper to make it smooth?

4 days and no question, so I'll make another. What mineral is added to paper to make it smooth?
Chalk, clay, talc... varying minerals are added for a variety of different finishes.

Alright, you win. I was thinking of chalk though.

OK: What is retrograde condensation?

Ok well condensation is the phase change of gas to liquid, via cooling.
And if retrograde is meant the reverse direction in this case, then it's a code word for vaporization, or else it's condensation by a means other than cooling. Perhaps condensation achieved by decreasing pressure (creating a vacuum) or altering the volume of the container?

OK: What is retrograde condensation?

Yes; its condensation achieved by reducing pressure.

My turn:


What's the name for a ribonucleic acid molecule that exhibits catalytic ability?

For bonuses:
Name a common one.
Why is the molecule in the answer interesting to the discussion of the origins of
life?

I think I know one of the bonuses (unfortunately, I don't know the main answer :lol:)

xRNA could be a molecule that is not only a replicator, but also catalyzes its own formation. Currently these two tasks are divided between DNA and proteins. You can't have one without the other - sort of a chicken and egg dilemma. The more fascinating thing that bears on this is that the mineral mica exhibits just the right sort of electrical and molecular properties to serve as a lattice for the initial formation of RNA. In fact, the architecture of DNA still has an architecture reminiscent of mica's signature.

ribosomes?

Yes and Yes to the bonuses. (Though Mr. Grimes appears to (edit) know way more than I do on the subject :*) ).


Hint: The answer is pure semantics.

Ah...ribozymes?

enzymatic RNA?

Right on!

Your turn.

Ah...ribozymes?

The significance of ribozymes to the origins of life is that it is a solution to the chicken-egg dilemma that Mr. Grimes mentioned, namely genetic material that can chemically act on its own kind.

That subject (chicken or egg) is good for debate, but I'm sure its been handled by the creationists on the relevant thread. Suffice to say though it's not possible to know the answer to that as things stand, so any theory is tenuous at best. What you can say is that obviously at some point chemicals developed the ability to form other chemicals from themselves, what point this became ultimately self replicating, we don't know? But we have some fairly good guesses. Suffice to say comparing modern DNA or cellular processes to primordial chemistry is misleading, something most creationists seem to forget. The precursor stages don't really exist, or at least we have no evidence for them. Unless someone knows of cases I haven't heard about which is highly likely, it's not really my area of expertise? :)

Open floor, mothatruckas!

We have 3 types of cones in our eye: blue, green, & red.

Which cone is causing us to be fooled by this illusion?
(the middle-front and middle-top squares are actually the same colour)

http://www.ukpuzzle.com/puzzles/47.jpg

So basically the question is why is the top-face brown square darker looking than the side-face brown square?

So basically the question is why is the top-face brown square darker looking than the side-face brown square?

:)
I can't see colour, so I don't know what you mean by "brown".
Do those two squares look to be different colours/shades? (center-top and center-front)

edit: yes, why is it darker looking?

Trick question, it's in the brain!

Every perception is in the brain. But we need certain nerve impulses to get to the brain to generate those perceptions.

The answer IS actually one of the three cones.

If it's anything like Same Color Illusion, the rods/cones aren't producing the illusion rather it shows up in the visual perception areas in the brain.

Blue ?

green ?

:lol: I realise I shouldn't give a question with three potential answers!

Anyway, its our blue rods which are picking up (and integrating) the brightness 'vibe' of each facing. Once the lighting has been extrapolated, the specific colour (in the small square) is then analysed and our consciousness is told what the colour is.

If you didn't have blue cones, you'd easily be able to tell that the colours were actually the same.

Just because blue cones are neccesary doesn't make them reponsible. It's not the cones that make the illusion, its the interpretation of what they send that does.

Well, yeah, but you're being too particular. All perception is in the brain, but the brain is trained by its interaction with the environment. "Lighting" is something we learn about, due to changes in lighting. We're fooled by the illusion because we're interpreting a colour due to its supposed lighting, and our ability to interpret lighting is due to our blue cones learning about the environment.

But yes, it's all in the brain.

Not all optical illusions are in the brain! Foir example, afterimages are in rods and cones themselves, caused by fatigue.

What you implied that you were looking for, is where does the signal diverge from the incident light on retina (the point where the signal stops being an ideal relection of reality, but in fact an illusion causing us to be fooled), these sorts of phenomena are much higher up the perceptual chain. The cones are working perfectly and don't in any way cause us to be fooled.

Ok time for a new question, no?

What's air speed of an un-laden.....uh wait...


When water moves in waves, by what two wave forms does the water move?

Bonus: Does a particle of H2O in the middle of a wave tank actually travel around the tank?

It's both transverse and longitudinal waves, so the water just below the surface goes round in circles (up and down circles).

A particle of H2O would probably go round in circles too, but wouldn't move around the tank so much I guess... (Assuming idealised waves.)

Good answer.
http://www.gmi.edu/~drussell/Demos/waves/wavemotion.html

Your turn.

What is the most dense solid in existence?

What is the least dense gas in existence? (at s.t.p.)

Least dense gas: H2 ?

Yup! Now for most dense solid.

Solid hydrogen?

If you're looking for something a little more feasable, iridium

Yup! Now for most dense solid.

Neutron star/ black hole?

Ununoctium?

Solid hydrogen?

Yup!

It's even been hypothesised that metallic hydrogen can be formed, with a separation between atoms less than the Bohr radius.

I don't know whether neutron stars or black holes are more dense than solid hydrogen, but the point of the question was that Hydrogen forms the least dense gas and the most dense solid (of all the elements <-- maybe I should've specified that!).

Stickciv / dutchfire 's up, depending on who asks first I guess.

But the question asked at STP. Is hydrogen solid then?

But the question asked at STP. Is hydrogen solid then?
The least dense gas at s.t.p. is what I meant.

Yup!

It's even been hypothesised that metallic hydrogen can be formed, with a separation between atoms less than the Bohr radius.

I don't know whether neutron stars or black holes are more dense than solid hydrogen, but the point of the question was that Hydrogen forms the least dense gas and the most dense solid (of all the elements <-- maybe I should've specified that!).

Stickciv / dutchfire 's up, depending on who asks first I guess.
I'm very skeptical of this mise.

It seems to me that while yes, hydrogen can be compressed into a solid that is denser then the solids observed at around STP, I see no reason why other elements can't be compressed further too (and I know for a fact they can be)! In fact, it seems to me that elements in the middle of the perioidic table like iron can probably be compressed into much denser solids, because unlike hydrogen they don't undergo energetically favorable fusion reactions under huge pressure.

Perfection is right. I put the Solid Hydrogen in as a joke..never expecting it to be the actual answer. The only reason Hydrogen would form a dense solid is because its a single proton, meaning that Hydrogen can theoretically be compressed down to a very high density. Its not very feseable though, especially considering that one would have to overcome what is basically an almost perfect proton-proton repulsion.

Well, we should keep going (though Mise should comment), I think Stick deserves a whack at asking the next question.

Naw, dutchfire can have it. Im better at answering than thinking up of questions.

Describe how a critical nuclear reactor can be brought to a higher power.

What is the least dense gas in existence? (at s.t.p.)

Not that it actually affects the answer, but standard temperature & pressure is very ambiguous: It is a different set of conditions depending on industry, country etc.

http://en.wikipedia.org/wiki/Standard_temperature_and_pressure#Definitions_in_c urrent_use

I'm very skeptical of this mise.

It seems to me that while yes, hydrogen can be compressed into a solid that is denser then the solids observed at around STP, I see no reason why other elements can't be compressed further too (and I know for a fact they can be)! In fact, it seems to me that elements in the middle of the perioidic table like iron can probably be compressed into much denser solids, because unlike hydrogen they don't undergo energetically favorable fusion reactions under huge pressure.

1. There's two things here, solid Hydrogen, which is just Hydrogen that's frozen (NOT AT STP, obviously...).

2. Metallic Hydrogen, which is an allotrope of Hydrogen that is stable at STP, and whose nuclear separation is less than the Bohr radius (on the same scale as the DeBroglie wavelength of an electron).

Solid Hydrogen is denser than the solid form of any other element, which is what I was getting at...

It's just one of those random facts that I picked up along the way. Thought it would make an interesting question!

I'm skeptical that frozen hydrogen is that dense, where did you get that from?

:wavey:

Describe how a critical nuclear reactor can be brought to a higher power.

Anyone want to answer that question? :)