Severian

It is the energy (or to be more precise the stress-energy tensor) inherent in the mass which causes the gravitational attraction. You cannot have negative mass, but that is a slightly deceptive statement. It is not that negative mass is forbidden but there is a symmetry in the equations so that any time you have a negative mass you can fiddle with your conventions (ie. what we call mass) to make it positive. (In most cases this is simply because the mass dependenc in the equations is m2 and m2=(-m)2).

No-one at all uses Sahara?

Once again, I didn't say that she did. Can't you read? But she did say:

Judging from the collection of pictures of yourself that you have been using as avatars recently, I can see where that comment is comming from...

This is wrong. There is no such observation. It is commonly thought that there is matter (albeit a very small amount) everywhere, over all space.

If you do a scan you can see the brain activity. Of course, if you want to get pedantic, I can't tell if a concious person is feeling pain either. They could just be faking it.

It is a bit vague though. It seems to be saying that babies don't feel pain because they have adenosine in their blood stream. But there is no explanation as to why that should make any difference or even an attempt to back that up. I also imagine that a baby takes a wee while to flush the adenosine from its blood stream. Does that mean that babies don't feel pain when they are first born? It all seems very dubious to me. After all, coma patients feel pain and they are not conscious.

Can you prove that?

How do you even define pain? Is pain the triggering of pain receptors in the body, is it only pain when the signals from these receptors get to the brain, or does there need to be some reaction to the stimulus before it is called pain?

That is it I'm afraid. The statement [math]\vec{q} \cdot \vec{\epsilon}=0[/math] is saying that the polarizations are only transverse.

It is not one of these really obvious things unfortunately. Let me try to explain as simply as I can, and you can let me know if you understood. Maxwell's equations are: [math]\begin{array}{ll} \displaystyle \vec{\nabla} \cdot \vec{E} = \rho \hspace*{5cm}& \vec{\nabla} \cdot \vec{B}=0 \\ \displaystyle \vec{\nabla} \times \vec{E} + \frac{\partial \vec{B}}{\partial t} = 0 & \displaystyle \vec{\nabla} \times \vec{B} - \frac{\partial \vec{E}}{\partial t} = \vec{J} \end{array}[/math] These are more nicely written in terms of a 4x4 matrix (a tensor) [math]F^{\mu \nu}[/math] defined by [math]F^{\mu \nu} \equiv \left( \begin{array}{cccc} 0 & -E_1 & -E_2 & -E_3 \\ E_1 & 0 & -B_3 & B_2 \\ E_2 & B_3 & 0 & -B_1 \\ E_3 & -B_2 & B_1 & 0 \end{array} \right)[/math] [math]\mu[/math] and [math]\nu[/math] are numbers which run from 0 to 3, with entry 0 corresponding to the time component, and 1 to3 being the usual space components. Then, the free (no source) Maxwell equations become: [math]\partial_{\mu} F^{\mu \nu} = 0[/math] We can write these equations in terms of the photon field [math]A^{\mu}[/math] instead [math] F^{\mu \nu} = \partial^{\mu} A^{\nu} - \partial^{\nu} A^{\mu} [/math] So [math]\partial_{\mu} F^{\mu \nu} = \partial_{\mu} \partial^{\mu} A^{\nu} - \partial_{\mu} \partial^{\nu} A^{\mu}=0[/math] Notice that I can change the field by an amount without changing F [math]A^{\mu} \to A^{\mu} + \lambda \partial^{\mu} \phi \qquad \Rightarrow \qquad F^{\mu \nu} \to F^{\mu\nu} + \lambda \partial^{\mu} \partial^{\nu} \phi - \lambda \partial^{\nu} \partial^{\mu} \phi = F^{\mu \nu}[/math] This is called a gauge transformation. I can change the photon field without changing the physics. This lets me make an extra equation (called fixing the gauge) to make life simpler. I usually choose: [math]\partial_{\mu} A^{\mu} =0[/math] which is the Lorentz gauge. Then, the (free) maxwell equations become [math]\partial^2 A^{\mu}=0[/math] This has solutions [math]A^\mu = \epsilon^\mu e^{i q \cdot x}[/math] where [math]\epsilon^\mu[/math] is the polarization 4 vector (with 4 degrees of freedom), and [math]q^2=0[/math] (which is the statement that the photon is massless). The Lorentz gauge condition on this solution implies [math]q \cdot \epsilon = 0[/math]. This removes one degree of freedom (the time-like polarization). Also notice that I can change the photon field further [math]A^{\mu} \to A^{\mu} + \partial^{\mu} \chi[/math] and everything remains the same as long as [math]\partial^2 \chi=0[/math]. In other words, I have not completely 'fixed the gauge' yet. This allows me to impose another condition [math]A^0=0[/math] This is called the Coulomb gauge. but, [math]A^{0} = 0 \quad \Rightarrow \quad \epsilon^{0} =0 \quad \Rightarrow \quad\vec{q} \cdot \vec{\epsilon} = 0[/math] The Coulomb gauge has removed another degree of freedom from the polarization vector, removing the longitudinal polarization.

I agree with that. There is of course the question, what is early? I personally think it should be before 8 weeks (or maybe even sooner). It seems to me that this is another case of 'scientists' proving something which was entirely obvious. At 5 months in, the baby is pretty much all there. Why on Earth would anyone think that they didn't feel pain?

The funny thing is, that when you do meet the person you will truely love, you will realise that every other girl in your life has been a mere infatuation. The ironic thing is that you will never know that until you meet them, so with each girl you will always be asking yourself 'is this the one?'. It is only when you finally meet the one that you will have no need to ask that question. I also think you are being a bit harsh on the girl. Imagine yourself having a friend who you were not physically attracted to. Now imagine them telling you that they love you. How would you react? It is perfectly natural that she should feel uncomfortable and withdraw.

I didn't say there was anything wrong with her advice. (She took a very general statement as a personal attack.) But since you ask... The problem was not that Red Alert has a crush on the girl. The problem was that he told her. He put her in a difficult, uncomfortable situation simply because he had a crush. That doesn't sound like friendship to me. There is absolutely no way that you should say something like that unless you are pretty sure of the response or are in a circumstance where it will not ruin the friendship. To suggest that people should be honest with their feelings is just plain bad advice. Most people are not even sure what their feelings are, so to go and tell someone that you 'love' them, when you don't know how they will respond, is just asking for confusion and problems. (Of course, sometimes you need to, but this wasn't one of those times.) RedAlert's friend was clearly taken by surprise. She does not reciprocate these feelings and now feels uncomfortable with the idea that her percieved friend was in fact something else. She will find it hard to look him in the eye again, and I understand why. If he wants her back as a friend there are only two ways to do it. One way is to wait until she feels a long enough time has passed that he can't possibly still have feelings for her (but we are taking years here). The second way is to tell her that he really didn't mean what he said. This sounds dishonest, but I am sure it is not. I am fairly sure that, if RedAlert were honest with himself, we would find his feelings pretty confused at the moment. He needed to go to her, apologise for the bad behaviour, and tell her that he was confused and naive and simply didn't know what he was feeling. Tell her that he has thought over it, and realised that he was just being silly, and of course they are just friends. Of course, what he did instead, with the advice of people on this thread, was go back and reinforce how much he did mean everything he said. So I think only option 1 is available now....

Strangely enough, I think I agree with you, at least on a scientific basis, but not quite in the way you mean. Both a theistic creation and the big bang as creation are essentially untestable scientifically. The theistic creation is obviously untestable. The big bang creation event is also untestable because one cannot probe a singularity. Therefore, as far as science is concerned, it is meaningless to ask if there was a big bang singularity. (Of course, one can still ask what happened at t+1 billionth of a second, but this is a different question.)

Some of you "naive" people do more harm than good when trying to 'help'. Oh no? And what if it is bullshit? Should I not point it out?

I think the crux to this is the statement: Is it really that surprising that a "molecule heated up to 8,000 degrees Fahrenheit (4,427 Celsius)" should locally behave like it is in a gas, rather than a liquid?

OK - fair enough. Maybe I am being too much of a theorist. Let me withdraw the word 'implies' and say instead: The new WMAP data is consistant with a flat universe. Notice that I still don't say 'nearly flat'. I admit it is also consistant with a 'nearly flat' universe, but you must also admit that it is consistant with a perfectly flat one too.

This was pretty obviously going to happen. Wouldn't you react in the same way? Imagine you had a friend who was a girl' date=' who you were not attracted to, but who suddenly declared undying love for you. What would you do? You would run a mile, because you would feel deeply uncomfortable with not being able to reciprocate those feelings. The email simply reinforced that. You made her feel small by your insistance of superiority - even willing to sacrifice your love for your frienship. I hope this has been a lesson to you - quit navel gazing. Stop looking at things only from your point of view. Ask how you would react if put in [b']their[/b] position and try and have some empathy for the people around you. I think the thing I find most disturbing, is all the bullshit people have been saying in this thread....

The Economist is most certainly regarded as a right-wing magazine in the UK. I used to buy it, but I found myself getting too upset with some of their more outrageously right-wing articles, so I stopped.

Don't get me wrong, I have no problem with a scientist having an opinion on religious matters, or indeed having religious beliefs. After all, I am 'religious' and a scientist myself. But I do take issue with scientists presenting non-scientific arguments in their scientific work, and this is what Ellis is doing. His position, which he expounds in his papers, is that there may not be any scientifically observable explanation of 'why' the universe is the way it is. So for example, there may be no problem with having fine tuning in the physical world because it simply 'is'. He interprets this as some sort of divine fixing of the parameters; God simply set up the universe to behave in the way he wants. I have no problem with this idea (and even have some sympathy for it), but it is not a scientific notion. Science makes the initial assumption that the laws of physics exhist absolutely and are testable, and furthermore that they stem from some central principle. In other words, once we have this principle, we should be able to derive all the laws of physics from it. Of course, this may not be true - it could be that the universe has no central principal and so we can never find out what it is, but science should not be asking this question. Science should be asking how do we find out what this principle is, assuming it exists. If science does not do this then it stops being science because it stops trying to explain the phenomena we see by physical laws. I am actually writing a paper on fine tuning at the moment (I have a PhD student working on it) and the attitute which a scientist must take is that fine tuning is not coincidental. The cosmological constant appears to be fine-tuned to one part in 10120, and if this is true it must have a reason. It may be that that reason is 'God', but science can never test that, and it is the responsibility of science to come up with some alternate explanation.