Rootje

Thank you all for the tips! And thanks martin, for putting in all the effort, it was well appreciated This all will get me started pretty well.

I'm a physics enthausiast, but frankly I know nothing of the quantum world. Does anyone have a suggestion what book is a good beginning to start studying Quantum Mechanics? Complicated mathematics is not a problem, i'm more looking for the fundamentals, the predictions, all the assumptions, the effects, of course the mathematics, the history of experiments, etc, that lead to quantum mechanics. Anyone any good ideas?

Now put a piece of transparent material in front of each laser, which is variably semi-transparent so that the gaussian intensity distribution becomes a homogeneus one, and the shape and size of the beam cross-section are modified to create perfect conditions. What if you then incline all beams so that they all come "out of the screen" a bit, with a very tiny interference region as a result?

Yes, that's the idea. Will the interference cause the first to beams to act as a solid barrier?

Suppose i take three equal laserbeams (equal phase, wavelength, etc.). I then put two of these laserbeams next to each other, seperated a distance D less then their common wavelength, and directed in the exact same direction. Next I put the third laserbeam some distance L opposite the other two, and direct it so that the first two laserbeams will meet the third at some point P. Because the beams are in exact phase, there will be a certain L for which the beams will be in exact anti-phase in the region where they meet. In this situation, will the first two beams then act as a sort of wall for the third, and will the portion of the third beam shining through D act as a point source and spread light in other directions then the direction original beam was going in?

Hm no-one seems to bother posting on-topic information here, but instead are preocupied with some real mature and scientific posting. Anyway, Remember the Twin paradox? The twin that's been traveling at lightspeed (rel. to earth) returns years younger then the one that stayed behind. The twin that stayed behind is like any outside observer. So indeed, in the black hole case, before an actual singularity is formed in the centre of the star (for any observer in the neighbourhood of the centre), the entire lifetime of the universe flashes by. And even if you wait far outside the Schwarzchild radius until the end of existence to see a singularity, Hawkings-radiation has already vaporized the black hole again. Simply put black holes do exist, but not in singularity form, just a very very heavy object in a very very small volume, with some characteristics of a singularity but not all. And something else; suppose we have a collapsing Neutron star, electrons have already merged with protons, gravity pulls stronger untill every empty space between the particles is occupied with some sort of matter, however can you compress it further then that? Doesn't matter come across "quark-resistance" or something?

Remember the Twin paradox? The twin that's been traveling at lightspeed (rel. to earth) returns years younger then the one that stayed behind. The one that stayed behind is like any outside observer. So indeed, in the black hole case, before an actual singularity is formed in the centre of the star the entire lifetime of the universe flashes by. And even if you wait until the end of existence to see a singularity, Hawkings-radiation has vaporized the black hole again. I think black holes do exist, but not in singularity form, just a very very heavy object in a very very small volume. The volume of the theoretical event horizon yes, but no smaller. Or .. am i wrong ?

its time w.r.t. the rest of the universe comes to a complete stop. Because of the relativistic time dilation in the presence of a strong gravity field... The time of the rest of the universe would just flow as usual.

Ok, a black hole (presumably) is a star which has collapsed to a single point, a singularity in which all the mass of the star is concentrated. A lot of their properies (like twisted spacetime when they rotate or X-ray energies in the centre of accretion disks, in accordance with their mass and zero diameter) have been theorized and some even observed. But all around the fact that a black hole has almost zero diameter. But when a star collapses beyond the density of neutron stars, it keeps on collapsing till it reaches its event horizon diameter. According to general relativity, its time w.r.t. the rest of the universe comes to a complete stop. How is it then possible for the black hole to collapse further to a singularity, if its time is frozen?

Yes, accoding to Hawkings it can. If you just take enough particles, the total amount of gravity they exert on one another becomes too great for the elektromagnetic forces to repell them, thus letting atoms collaps under the weight of all other atoms, fusing electrons and protons to create neutrons. You just made a neutron-star. Now it's the strong nuclear force creating resistance to further collapse, but just keep on adding mass and eventually even that force is outstronged by gravity, making further collapse possible. Now you made a black hole.

Cool. But how does that work, isn't it the helium that emits the stimulated radiation and the nitrogen serving as a source of spontaneus emission with the right frequency for the helium? Im taking a wild guess here ..

Well, its not exactly my area of expertise either, hence the question I always tought every atom has very specific frequencies of light they emit creating a fingerprint-like fraunhoffer spectrum, because of the limited amount of allowed energy states an electron can be in. Are bands created when you deal with paired atoms like nitrogen?

Hi all! I'm just working on a concept, and i need to know something - is it possible to excite nitrogen atoms in the air by use of a laser (or a pair of lasers) at a specific frequency, so that the atom emits the excess energy in the form of visible light of predefined color? And if so, what direction is that light emitted in or is that random? Thanks!