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[The Fish]

Well, I can't answer that question...what exactly is the problem asking for? Can you give any more details?

[Cabsav]

Well basicly i have to make a dihybrid cross like W= wiseness B=big muscle

WwBb x WwBb and im kind of confused on how to apply another trait to G.

Like would i use non glowing as the other trait eg. GgNn N=non glowing?

Sorry if im confusing you im not good with questions.

[The Fish]

Well, if G is glowing, then g is non-glowing, by definition. Sorry, Cabsav, but I'm just not grasping the question. Perhaps someone else understands what's going on?

[chris_uk_83]

So you have a wise, glowing, big muscle? What? I never did get biology

[Cabsav]

Oh right how silly of me! of course i knew that, dw about it i basicly understand it now. Thx for your time cheers.

[The Fish]

So you have a wise, glowing, big muscle? What? I never did get biology

What, are you saying your muscles AREN'T fluorescent and capable of carrying on a scintillating discussion of Kant? That's what you get for being a physicist, I suppose.

[chris_uk_83]

Just out of interest, what is a wise, glowing, big muscle? Or is the answer going to be really long and complex and require an MD to understand?

[The Fish]

It's not an actual trait, it's just an example for the purposes of understanding basic genetic inheritance patterns. In Cabsav's example, he was treating "Wiseness" [sic] as a discrete trait, same for Big, which are phenotypes (i.e. observable traits). So you could, for example, take a wise, small parent and an unwise, big parent parent and figure out the probabilities of their kids being wise or big. Of course, in reality, genes don't work this way (there's no gene for "big muscles" or "wisdom").

A real-world example, though, could be: parent A has a gene that codes for a messed up protein, which could result in cystic fibrosis. If parent B also has a copy of that gene, you can determine the probability that their child will have cystic fibrosis.

[chris_uk_83]

Ah, I see. I did actually learn that in my GCSE biology all those years ago. Thanks anyway

[Seleucus I Nicator]

Do YOU have problems with your physics homework? Is it driving you mad? Do you fail to see precisely why nothing can travel faster than the speed of light?

Actually, I wonder about that very question. I heard nothing can go faster than the speed of light and was provided with an explaination, but I did not understand it. I would appreciate if you explained it as good as you can to me.

[chris_uk_83]

Haha, I dug myself a big hole there didn't I? Any chance I can fend you off with a torrent of Wiki articles?

Try this one for a description of special relativity. This is the theory postulated by Einstein that said nothing can travel faster than light. It gets a bit technical in places, but if you can understand the basic principles you should be ok.

Let me know if you get stuck with it and I'll see what I can do.

It basically boils down to you accepting the mathematical proof of the equations of special relativity and then applying them. There's also an argument that says cause must always preceed effect (seems obvious), but faster than light travel means that it can be the other way around i.e. you can travel back in time. I'm tempted to skip over this argument though because it actually runs much deeper than it appears, and will have people going "ooh, a time machine". Please don't do that .

[Cabsav]

Cant things go faster than light in water tho? While i was looking around on wiki (i no nothing about physics!) But the speed of C is lower in water than a vacuum and they have managed to speed particles faster than C in water though. Again i know nothing its wiki.

[Hephaistos]

Actually, I wonder about that very question. I heard nothing can go faster than the speed of light and was provided with an explaination, but I did not understand it. I would appreciate if you explained it as good as you can to me.

Okay I will give it a try. Please have a look at this formular:



This is the energy of one particle (or an object) in a relativistic view. m0 is the mass of this particle/object (while its speed is zero). c is the speed of the light in vacuum and v is the spped of the object.

Concentrate on the expression after the last equal sign: What happens, if you replace v by c (the particle is flying with light speed)? Think a moment about this, before you continue to read.

The root out of 0 (1-c²/c² = 1-1 = 0) still is 0. But deviding anything by zero will result infinite... But an infinite energy... In physics absolutly nothing can be infinite, so an infinite energy is not possible, too.

There is only one exeption: 0/0 is finite. For c² can never be zero, m0 must be zero, and then you will have and finite solution. (That is actually, why we do believe, that the mass of a photon is zero.)

Of course this formular is no real prove. But this formula was created by Einstein while he was observing the real nature. At the moment we have no evidence, this formular isn't discribing the real nature. And for some people this formular does help to understand.

By the way, to make things a bit more complicated: What happens, if you insert a v > c into this formular? Think a moment about this.

Actually we will get a real solution for this formular. It is a little bit complicated to calculate, and the result is somewhat strange... But it is imaginable and quite easy if we cheat around with m0 a little bit.

This particles with v > c we do call "Tachion". Nobody had ever found any evidence any hind that Tachions do really exist, but they are theoretically possible. If you like scifi you will probably heard about tachions.

[chris_uk_83]

Cant things go faster than light in water tho? While i was looking around on wiki (i no nothing about physics!) But the speed of C is lower in water than a vacuum and they have managed to speed particles faster than C in water though. Again i know nothing its wiki.

c is the speed of light in a vacuum. This value never changes. What can change is the actual speed of light through a particular medium, such as water, glass, crystal, anything that allows light to pass.

In this case, the speed of light in the medium v = c/n where n is the refractive index of the material (which you usually have to look up, it's particular to each material).

Now what you can do is accelerate a particle such as an electron, through this medium, and you can impart a higher velocity to it than the speed of light in that medium. What happens is something similar to what happens when you travel faster than sound, you get a kind of 'luminous boom', which isn't usually visible light but can be detected. This is known as Cherenkov Radiation. This technique is actually used at particle research facilities to detect fast moving particles.

[Mathias]

Cant things go faster than light in water tho? While i was looking around on wiki (i no nothing about physics!) But the speed of C is lower in water than a vacuum and they have managed to speed particles faster than C in water though. Again i know nothing its wiki.

Isn't C a constant? Although the speed of light depends on the medium which it travels trough, C is always 299 792, 458 km/s in physics if I remember correctly. C comes from the latin word celeritas, meaning swiftness btw.

What you are saying goes against the formula I know though, for if the particle has a positive mass (a bradyon) then v must be lower than c. The only things that can go faster are the hypothetical particles called tachyons, which mass is imaginary.

Edit: didn't see Chris' post

[Simetrical]

There is only one exeption: 0/0 is finite.

Not true. 0/0 is undefined. However, a limit that loosely speaking tends toward 0/0 can be finite (for instance, the limit of 17x/x is 17). It can also be infinite (for instance, the limit of −x²/x = −∞), and so it's called an indeterminate form. Calculus students will recall that L'Hospital's Rule is very useful for determining the limit of indeterminate forms. In this case, there is no limit as mass goes to zero and speed goes to infinity, because the result depends on how you approach them (this point requires knowledge of limits of functions of multiple variables). The (correct) result that zero-mass particles may have the speed of light cannot be derived from the equation you posted, but instead presumably comes from the derivation of that equation.

[Hephaistos]

Not true. 0/0 is undefined. However, a limit that loosely speaking tends toward 0/0 can be finite (for instance, the limit of 17x/x is 17). It can also be infinite (for instance, the limit of −x²/x = −∞), and so it's called an indeterminate form. Calculus students will recall that L'Hospital's Rule is very useful for determining the limit of indeterminate forms. In this case, there is no limit as mass goes to zero and speed goes to infinity, because the result depends on how you approach them (this point requires knowledge of limits of functions of multiple variables). The (correct) result that zero-mass particles may have the speed of light cannot be derived from the equation you posted, but instead presumably comes from the derivation of that equation.

I am fully aware of it. But what I wanted to try, was to explain a complicated matter, to somebody you probably newer had any analysis lessons. It isn't needed to be explained this complicated, to understand what is happening.

[Simetrical]

I am fully aware of it. But what I wanted to try, was to explain a complicated matter, to somebody you probably newer had any analysis lessons. It isn't needed to be explained this complicated, to understand what is happening.

Well, no, but you still shouldn't say that 0/0 is finite, because that's misleading. You should have said something like "it can be finite, and in this case it is".

[Pra]

Not true. 0/0 is undefined. However, a limit that loosely speaking tends toward 0/0 can be finite (for instance, the limit of 17x/x is 17). It can also be infinite (for instance, the limit of −x²/x = −∞), and so it's called an indeterminate form. Calculus students will recall that L'Hospital's Rule is very useful for determining the limit of indeterminate forms. In this case, there is no limit as mass goes to zero and speed goes to infinity, because the result depends on how you approach them (this point requires knowledge of limits of functions of multiple variables). The (correct) result that zero-mass particles may have the speed of light cannot be derived from the equation you posted, but instead presumably comes from the derivation of that equation.

Nerd....

Gawd I've not done L'Hopital's in 4 years!

If I remember the determinant forms of something are given by 1/x lim x->0 or x->infinity...there are a few others, but I didn't know that 0/0 is explicitly definite...whoops you said it with L'Hopitals' ignore my musings.

[Simetrical]

An indeterminate form is something that can be reduced to a limit of the form lim_x→a f(x)/g(x), where lim_x→a f(x) = lim_x→a g(x) = 0 or ±∞, for some particular a that may be either a real number or ±∞. (Either both have to go to zero or both to infinity, although one can go to positive and one to negative infinity.) Then you can find the limit by taking the derivative of top and bottom. So for instance. lim_x→0 (sin x)/x fits the criterion, so it equals lim_x→0 (sin x)'/(x)' = lim_x→0 (cos x)/1 = cos 0 = 1.

Indeterminate forms include 0/0, ∞/∞ (= (1/0)/(1/0) = 0/0), 0×∞ (= 0/0), 0⁰ (= e^{0 ln 0} = e^0×∞), and probably some others I've forgotten, but they're generally easy enough to spot. Things like 1/∞ and 1/0 are not indeterminate. They're equal, respectively, to 0 and ±∞, always. (That is, if the limit exists at all, which it may not in the latter case: consider for instance lim_x→0 1/x sin(1/x), which is of the form 1/0 but oscillates between positive and negative infinity. The limit of the reciprocal of a function that goes to ±∞, on the other hand, will always exist and be equal to zero.) Indeterminate forms can always be equal to any real number or ±∞, which is what makes them indeterminate.

Determinants are something entirely different.