BhavinB

The whole purpose of moving anything is to make something out of it....like a smiley face. When you can arrange materials into some ordered pattern, then you can make devices like transistors (the whole concept behind microfabrication and lithography). So when you see Don Eigler's "IBM" picture made of copper atoms, the purpose is to research how we can move individual atoms around and make devices out of it. A friend of mine is researching how to move Silica spheres to form complex shapes. They do this using a Scanning Probe which is similar to scanning probe microscopy. By applying a slight feild to the sharp tip, you can change the local electron wavefunction of a particle so that it sticks to the tip. Then you can move the probe and drop the particle. This is insanely slow...which is why this technology will probably not be used in industry (atleast not for a decade). But controlling atoms one by one is like a researchers dream!

I graduated from Canada's first Nanotechnology undergrad program (at the University of Toronto) and was totally surprised by what Nano REALLY is. Most people are blinded into thinking small robots, machines playing with your DNA etc... Sadly, thats just over hype. There is nothing close to that being researched in Nano and actually, micro/nano robots are a smaaaaaallll subset of nano. The biggest aspect of nano is materials. Controlling material properties like crystal size, pore size, solid solution ratios, phases gives amazing macro properties. The next biggest aspect of nano is Micro Electro-Mechanical Systems (MEMS). Again, this is a misnomer cuz many times there is no mechanical aspect. There are nano chemists working on ways to control properties of chemicals such as local redox states etc.... There are nano biologists trying to tag cancer with quantum dots (a term used too often but defined never). But eventually, the coolest things will happen when we start figuring out enzymes and proteins. Those will be our "nanobots". B

you're right, I was talking about Fermats Principle. My bad...I always assumed all other paths cancelled out.

AFAIK? lol...what does that stand for?

The Maxwell-Boltzmann distribution, yes.

Not just that, all the energy associated with the angular momentum would suddenly be converted to some other form of energy...probably heat. Now that would be nuts!

Temperature is actually a property derived from a large number of particles and it has no meaning for individual particles or a very small number of particles. So the answer to your question is no to both your options. In statistical mechanics, the concept of temperature comes about in a very abstract way. It is sort of related to how a large number of particles are distributed in energy. If you think of all the particles as vibrating, you can say that some are vibrating fast and some vibrating slow. And in some way, this distribution gives rise to what we call as temperature. But it is incorrect to say "what is the temperature of one molecule". B

Light Intensity has many units, such as Lumens. However, in research the widely used units are W/m^2 (power density). The intensity of lighting at the earths surface is 1000W/m^2. Though we may be able to reproduce the spectrum of light the sun emits, there is no way we can to some practical degree reproduce that intensity (yet).

I'm surprised noone has said this yet, making me wonder if my answer is correct at all. However, I was taught that the reason our function decays over time has to do with DNA replication. There are these molecules called DNA polymerase which zip along DNA strands creating copies as they go at incredible rates. It is said that there are correction mechanisms as well but every now and then, a cell with improper DNA is created. Over the years, there are more and more of these improperly made DNA cells which leads to decay of body functions in all aspects of the body...leading to death obviously.

The rule of thumb used in fluid mechanics is that the pressure experienced underwater at some depth h, is equal to the weight of the water directly above you. So this formula is correct.

lol...ok. Lets look at the word "predict". 'To state, tell about, or make known in advance, especially on the basis of special knowledge.' Based on everything quantum mechanics derives about spatial and energy relations, it does not in advance predict spin. For example, quantum mechanics predicts the energy levels in a quantum well. Quantum mechanics predicts the spatial distribution of electrons in the hydrogen atom. Quantum mechanics predicts that the H2 molecule will form but the He2 molecule won't. QM also derives the quantization of angular momentum. However, QM cannot in advance predict the existance of spin. Fortunately for us, Spin is a type of angular momentum and scientists have found that appending all spatial functions with spin angular momentum functions is the correct answer. Perhaps you are confusing the fact that we can use our knowledge of spin and angular momentum in quantum mechanics to predict new things like spin transistors. But don't be confused in thinking that it is derived in quantum mechanics...it never was. Saying its not classical doesn't mean it was derived quantum mechanically.

Alright, I'll concede that SE is not all of QM. But the obvious major part of QM is solutions of the quantum mechanical hamiltonian which we can describe for any system. There is in effect no way to derive spin from any hamiltonian...which is exactly why there is no QM derivation of spin shown in ANY quantum mechanics book. The true 'proof' of spin is in experiment, and we correct all our particle wavefunctions accordingly.

I say QM doesn't predict spin in the fact that you can't start with the Schroedinger equation and derive some property of particles that implies it has internal angular momentum (ie spin). However, if you use the not so used, and incorrect Dirac equation, you can derive the concept of spin theoretically. The same goes for any of the proposed string theories...they all must theoretically explain spin. If you look in any quantum mechanics book, they will always say a particle total wavefunction is the multiplication of its spatial distribution and its spin distribution. What they are doing is correcting for the fact that QM cannot derive spin.

Actually spin is a correction of something that quantum mechanics does not predict. You can call it dodgy, but the angular momentum interpretation is complete in that it describes all the properties we have noticed about spin. More interestingly, the Dirac equation DOES predict spin.

I only implied that there is an electromagnetic interaction in what we call absorption (or energy transfer). It has been modeled as a damped harmonic oscillator as you've shown in your link. The damping term 'gamma' and the oscillation frequency 'omega' are descriptions of the electron-nuclear interaction. They basically define the "spring constant" and "damping" of the system. The interesting result is there is interaction with photons that are NEAR the transition frequency "omega_0" (as opposed to exactly "omega_0"). However, the point I wanted to make is that the link you post is a description of the dynamics and not of the interaction mechanism itself. There can essentially be other systems (obviously not free electrons) that react to EM radiation (ex: exciton breakdown...otherwise known as stimulated emission).