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String theory has a well documented history. If you are interested then look it up. Initially, string theory was developed as a model for the strong interaction. As we have fermions in nature string theory needed fermionic degrees of freedom and hence superstrings. It was things like the d=10 than made it difficult to apply to the strong force and then QCD took over. What "saved" string theory is the fact that it includes the graviton in it's spectrum. We can say that the biggest prediction of string theory is gravity. If you are interested pick up Barton Zwiebach's book.

Heat is energy. And yes you can convert heat into useful mechanical or electrical energy. That's what all engines and power plants do. They release stored chemical energy convert it to heat and then use that to drive turbines etc. Heat can be converted into electrical energy using a thermocouple.

mateenashraf should be banned for making such a stupid request. Science should push down such religious, ethnic and political barriers not put them up.

I think most of the books recommended (although good books in general) are too advanced based on just having high school physics. You need to start with one of the books intended for first year university level. Reading that will give you the background to start to read more advanced books. Armed with a good grounding in "basic physics" you can then go on a pursue more specific topics. The only book I have used at this level is "Fundamentals of Physics", by Halliday, Resnick and Walker. It contains quite a lot but has a very easy to read style and plenty of exercises. I am sure there are many other similar books out there.

It is a good book, but it is now outdated. We know so much more about observational cosmology now than we did when the book was written. Some things that are speculated are now proven or disproved. So read it, but be careful about exactly what it says.

NO! Multiple dimensions are necessary in string theory. For superstrings you need d = 10 and for the bosonic string you need d = 26. These dimensions are not postulated to make things simpler but are needed. If you quantise a string you will see that in order be be consistent, that is free of anomalies you require d=10 or 26 depending on the theory. In no way are these dimensions put in by hand, the mathematics requires these dimensions. You should not that this does not depend on the quantisation scheme you use, you will always get these dimensions but using slightly different arguments.

Losing support from who and why? What I might accept is that string theory may be losing support from the theoretical physics community as a possible unification scheme, but that does not mean that string theory is useless. Quite the contrary, string theory is getting back to it's roots as a description of strong physics and this makes it very interesting and useful. This new look at the possibility of describing strong physics by a string theory is the AdS/CFT correspondence which relates a gravity theory to a gauge theory. One is able to do gauge theory calculations using gravity! This is one of the great properties of string theory, it allows one to geometrically construct gauge theories. (You can construct gauge theories by stacking branes and conneting them with strings). One issue so far is that the gauge theories are supersymmetric and as of yet do not quite reflect physical gauge theories. This is all work in progress by many people and the out look it good. Other areas of interest include twistor string theory and MHV amplitudes, integrability of N=4 super Yang-Mills and the AdS/CFT corrspondence, D-Brane Dynamics and Gauge Theories and many other things... So string theory is not dead and is far from being useless in phsyics. Woit is wrong!

If you take string theory seriously then you have to believe in extra dimensions, it is a formal requirement of superstring theory that in order to be quantum mechanically consistent then it must be formulated in 10 dimensions. In string theory gravitons, Kalb-Ramonds and Dilatons are states of the closed string and so can propagate in the "bulk", that is they are not restricted to start and finish on branes. I do not know of any other closed string states. I guess they are all of spin higher than 2 and so there low energy effective interactions are inconsistent (Witten-Weinberg theorem). So I guess (but I am no expert in string theory) that it is difficult to imagine other particles propagating in the bulk.

I expect going down these lines will not help you with quantum mechanics. I too am very unhappy with the fact that the way it is formulated relies heavily on the role of the observer. But that is how it is formulated. Quantum mechanics was formulated to answer experimental questions. The notions of an observable and an observer are critical. You will have to be very careful about trying to answer questions in standard quantum mechanics that do not make a clear cut difference between the observer and the system. This makes quantum mechanics of truly closed systems difficult, such as quantising the entire universe. What is the quantum mechanics of the observer? People like Chris Isham and others are trying to build theories that will cope with this by using category theory and topos.

Are you suggesting that we do not pursue the possibility of a cosmological constant because Einstein thought that it should vanish? If so then this is absurd. Two points, i) Einstein died in 1955 well before observational cosmology developed in to the science it is today. ii) Einstein always was unhappy with quantum mechanics and did not actively work on quantum field theory. Having a zero value parameter in quantum field theory is awkward and "unnatural". Einstein although well respected is not held in some kind of awe by practising scientists. Generally, Einstein's ideas need to be re-examined from a modern view point.

I am studying towards my PhD in mathematics. I can tell you that it is a mixture of hard work by yourself as well as talking lots to other people. All papers published will have references and acknowledgements. People are also expected to attend conferences and seminars. I think that very little work these days gets done in isolation. There is just now so much out there already known and you wouldn't want to waste too much time going over old results.

Try this one. I can "prove" 1 = 2 [math]a=b[/math] by assumption multipliy by b [math]a^{2} = ab[/math] minus [math]b^{2}[/math] form both sides. [math]a^{2}-b^{2} = b(a-b)[/math] using the difference of two squares identity. [math](a+b)(a-b) = b(a-b)[/math] divide both sides by [math](a-b)[/math] [math]a+b = b[/math] Now use our initial assumption and we get 1= 2. Can you spot my mistake? If you know this trick already don't give it away, let the others have a think about it. I am sure there are many many other similar fallacies out there. Maybe we should start a new thread where people can post them?

You can probably "show" it using what is known as a fallacy. That is some apparently correct derivation which upon closer inspection uses some dubious logic. Most common examples involve division by zero. Indeed using division by zero you can show that any number is equal to any other! But as you know division by zero is not allowed!

For a first course in QM all you will need is some basic calculus and some linear algebra, mostly vector spaces and matrices as operators.

You mean by a Lorentz transformation? If so just have a look at the article I cite. If temperature is Lorentz invariant then no. If temperature is dependent on the intertial reference frame we have two different opinions; 1) Planck [math]T_{u} = T_{o}(1- \beta^{2})^{\frac{1}{2}}[/math] where [math]\beta = \frac{u}{c}[/math], [math]u[/math] being the speed of the moving frame. [math]\beta^{2} = 1[/math] when [math]u = c[/math]. So yes, it could be Lorentz boosted to zero, but only if it moves at the speed of light. 2)Ott [math]T_{u} = T_{o}(1- \beta^{2})^{-\frac{1}{2}}[/math] Now at [math]u = c[/math] we have an infinite temperature! For [math]T_{u}[/math] to be zero we require [math]1- \beta^{2}[/math] to be big but [math]\beta^{2}[/math] is real and less that [math]1 [/math] Of course what I have said does not include quantum mechanics, which gives us the notion of absolute zero.

Who says that? They have finite radius, just small.

It is not something I know much about, but I do know that Planck and the later Ott showed that temperature is not a Lorentz invariant, however they got different transformation laws! What they both assumes (I think) is that Boltzmann's constant is Lorentz invariant. If you allow it to transform then it is possible to get an invariant temperature. You will have to find out the details yourself, it is not something I have looked into myself. This article in the Russian Journal of Physical Chemistry is a good place to start.

What does orthogonal mean in 1-d? What is a vector in 1-d? Maybe thinking about that might shed some light on your problem.

Not that anyone is interested, but I have now added a palette that has all the commands for the package. Also, I have written a further add-on for the package that defines complex conjugation using de Witt's convention. As the definition of complex conjugation relies on conventions I decided not to include it directly in my original package.

I am sure we have a thread on this already. Try a search.

You will have to explain these remarks.

Michael Jackson tried that....

Electromagnetism is explained in terms very similar to general relativity. The notions of a connection and curvature are more general that found in general relativity. It is hard to explain here and requires many notions from modern differential geometry. But the bottom line is that EM (and Yang-Mills theories) is a geometric theory. I have written a little on this subject as part of my PhD. You can find more details on my website.

I am not sure what you mean by this, but never mind. Isn't a singularity defined as a point of infinite curvature? I think the two notions of singularity and infinity are equivalent in this set-up. Examine the Kerr metric (and maybe other solutions) and see what happens.

Particles and light rays follow what are know as geodesics if they are acted on by no forces other than gravity. Geodesics are in effect the "straight-lines" on a curved space; they are the shortest distance between points. What is curvature? That is a hard question to answer exactly without some differential geometry, which I won't give here. But basically if you take a vector [math]X_{0}[/math] at the point [math]p[/math] and parallel transport it along to different paths [math]C[/math] and [math]C'[/math] to the point [math]r[/math] you obtain two (in general) different vectors [math]X_{C}®[/math] and [math]X_{C'}®[/math] The curvature is defined in essence to be the difference of these two vectors. With some differential geometry you can make what I said more meaningful. Try a simple experiment on [math]\mathbb{R}^{2}[/math] i.e. a sheet of paper and [math]S^{1}[/math] i.e. a ball. In these cases parallel transport just means moving a vector along a path such that it keeps pointing in the same direction. So on your sheet draw a loop and trace your vector along it keeping it pointing in the same direction. You will see it returns to your original vector. Thus our sheet is indeed "flat". Now try it on a sphere, a football or something. You will see that the vector does not come back to the same vector, but it is rotated by 90 degrees. This is the "curvature". You can do the same thing on any space-time (or more generally any manifold) provided you define how to parallel transport vectors. This requires some extra structure and this is part of differential geometry. From this curvature you can calculate geodesics, but this is more involved so I won't tell you how.