Severian

Aardvark: While pcs is a dreadful troll a lot of the time, I think in this case, he has a point. I don't know whether it would hold up in a court of law, but it is a valid point. Which means in this case, you are the one who is trolling.

This would actually make a nice tutorial problem. If you properly take into account length contraction, you will see that you can never make a point on the rim of the wheel go faster than c.

A better analogy would be shouting in public. If someone in a crowed street started shouting out loudly that in his opinion all black people were inferior to white people (but not encouraging any discrimination - just stating it as an opinion), we would all get pretty upset about it. But you could argue that this is freedom of speech.

Oh i see - silly me! - i didn't even notice the typo

Despite what 5614 said, you are correct. It is most probably absorbed and re-emitted. How you define 'the same' is a but subjective though....

You don't need to predict the future in order to be predictive. Evolution for example might predict a evolutionary link between different species, and if new fossil evidence is uncovered which support that claim then it is a successful prediction. However, one of the things that I see often (as a professional scientist) is the different levels of rigour in predictions and evidence which different fields have. In particle physics (my field) we test our models to an extreme. We have quantities which we can predict to 10 significant figures and when we measure them with this accuracy we find they agree. When we make a measurement we perform sophisticated statistical tests (since quantum mechanics is probabilistic) to make sure that what we see is a reasl effect. Before we announce a discovery, we insist on a 5-sigma significance which (as any statistition will tell you) is bordering on obsessively careful. I don't see this sort of rigour in other fields. Cosmology is close enough to particle physics that I understand the field really pretty well, and I already see there a lessoning of these standards. Their data is messy and based on all sorts of assumptions. They perform extrapolations over orders of magnitude. But they never seem to quantify any systematic errors from these assumptions and extrapolations. Then they compare the massaged 'data' with theory and 'rule out' models at the level of 2-sigma significance. 2-sigma is a 95% confidence, so they are saying that they are 95% sure that the data is inconsistant with the theory. However, this means that it will take on average only 20 measurements to rule out a 'true' theory. This seems to get worse as we move away from physics. Evolutionary science doesn't even seem to have significancies in predictions. They have huge extrapolations with very little justification. And while I think evolution is the best theory we have, and probably right on some level, this makes me deeply uneasy. What is worse, imho, is that the scientists studying these things do not see this themselves. They have not been conditioned to a field which demands extreme rigour so they don't see the inherant assumptions they are making. Ocassionaly someone on this forum will state something along the lines that we are as sure of evolution as the origin of species as we are of Quantum ChromoDynamics. That always pisses me off, because it is clear they have no idea what they are talking about.

Predictivity. One of the desirable things in a scientific theory is that it should make predictions. 'Intelligent falling' does not make predictions, whereas Nowtonian gravity does. Of course, this is simply semantics to a certain extent. I could express mathermatically what 'God's will' would be in certain circumstances and make 'IF' as predictive as Newtonian gravity, but then of course it would be Newtonian gravity with another name. Furthermore, the desirablilty of predictivity is a somewhat aesthetic judgement. A theory doesn't have to be predictive to be correct, but it has to be predictive to be a scientific theory.

You don't need to be like Hitler in every way before you can be compared to him. Maybe Chavez is just sporting a new moustache these days....

So can you correctly predict the perhelion of Mercury?

So are you going to participate in this 'fighting' or is it just talk?

I am a bit surprised that more has not been made of this. If this is correct, it would rule out cold dark matter, which previously was the favoured form. This result implies that the dark matter particle has really low mass, such as an axino, and rules out most traditional supersymmetry scenarios.

But you can travel at very very close to the speed of light. And the weird thing is, physics wouldn't look any different. The laws of physics don't change with speed, so they are the same as before. Of course, if something is moving at very high speed relative to you, you will see the effects of length contraction and time dilation. Time will seem to pass more slowly in the system which moves very quickly with respect to you, and distances (in the direction of the relative velocity) will appear much less. So a person, waving while coming towards you at near light speed, will appear to be as flat as a pancake, and will wave agonizingly slowly. In the limit that the relative speed approaches c, he will become completely flat and his wave will become so slow it appears to stop.

The observation that neutrinos have mass is relatively recent (the last decade) and there is now a lot of interest in determining their properties more precisely. http://www.hep.ph.ic.ac.uk/iss/

A kaon is a particular bound state of a quark and anti-quark, one of which must be a 'strange' quark. It is not a fundamental particle. There are different kaons, depending on which quarks are inside. For example K0 is a bound state of a down quark with a strange anti-quark, while K+ is an up quark with a strange anti-quark. They are rather interesting because their interactions do not conserve CP.

I am not Athiest, so I am not sure if I am allowed to respond, but I will anyway. It average velocity is zero. Its average speed is c (not quite true, since there will be a very small delay at the reflection). No one said that light could not change velocity. It cannot change speed. The magnitude of its velocity cannot change but its direction can. So a photon can collide with another particle and gain enough momentum from the collision to change direction (this is in fact the 'force'), but it will leave with speed c again.

Hardly. When I am teaching my course on QED, am I expected to do high energy scattering experiments (e.g. [math]e^+e^- \to \mu^+\mu^-[/math]) and produce evidence for the theory before progressing? Some things need to be taken on trust.

That is presumably a war thing though? Wars are expensive.

Certainly in physics (my subject) this isn't the case. At a low level, eg Newtonian mechanics, the students can't ask a question which the professor can't answer. At high levels, eg Quantum Field Theory, there is no shame in not knowing the answer to a question, so professors usually are happy to admit they don't know. I think a bigger problem is that professors sometimes assume a way of thinking, since that is how they think and how their fellows think. But often the student thinks in a rather different (and quite wrong) way. This assumption means that the student may get completely the wrong end of the stick, and afterwards think they were being told a lot of rubbish when they weren't. I even see this pehnomenon on this site...

I can you know. Light-by-light scattering (a box diagram with a fermion in the loop and photons on the legs).

OK, fair-enough, he is a crackpot then (alternatively termed a 'biologist').

To be fair, the BBC showed an interview today with the leader of the British Muslim Council , Iqbal Sacranie, who called for the arrest of the muslim extremists who were inciting violence. So at least the BBC is presenting the other side. I suppose it just gets lost in amongst the pictures of raging mobs.

If a 12 year old asks if Newtonian gravity is true, should you say 'no it isn't' and try and explain GR to them? Probably not. You have to tailor the information to a level your audience can cope with.