Quantum Theory

"depression and desperation" are Leonard Susskind's terms for what some fellow string theorists are now experiencing. The field is ailing and Susskind was one of the earliest people to work in it---one of the initiators of string over 30 years ago. It is very interesting to watch the decline of stringy research, which has been underway since beginning of 2003 (with publication of the KKLT paper) I thought this series of comments was sort of eloquent so I will post it. It shows the decline in morale and shift in attitudes. After a 18 February 2005 (quite recent) informational post by Peter Woit there is some feeling commentary by others. http://www.math.columbia.edu…

What exactly is Quantum Physics? My minor research informs me that it deals with small variations in energy. That the classic model of the atom is wrong. That its very, very hard to understand...lol. Enlighten me with some basic concepts.

Okay, we know that when a small star runs out of nuclear fuel, it compresses to a white dwarf (or brown dwarf >_>) and no more because of the Exclusion Principle. And bigger stars compress all the way down to a black hole because their mass is too large, they overcome the Exlusion Principle due to extreme mass and gravity. Now, God decides to hide the singularity from the rest of the universe via the black hole's powerful suction, so that the singularity can never be seen by human eyes. However, here's my question, I read somewhere that Stephen Hawkings lost a bet because his friends managed to prove that it is in fact possible to see a naked singularity. Can so…

I'm going to explain a few things as I understand them, and I want someone correct me where I'm wrong. I don't know the correct terminology for everything, so bear with me. Assume we have a box with three (for the sake of simplicity) mirrors set up inside of it. There is a mirror right inside the entrance of the box that is coated so that the photon has a 50% chance of reflecting at a specified angle, and a 50% chance of passing through the mirror. There are further mirrors within the box which ensure that the photon will emerge from the box on the other side at the same position no matter which path it takes after encountering the first mirror. From what I under…

Are there any quantum mechanical ideas, where there are 2 points of view that i could write a paper on?

how can 1-D super strings vibrate in 10-11 dimensional universes, and effect all of them at the same time, if something is 1-D, does that make it possible to vibrate in multi-dimensions at the same time?

Hi, Are electrons, nuetrons, and protons actually small spheres or is that just an easy way to understand what's going on (like the bohr model of the atom)? Have scientist seen these sub-atomic partiles under microscopes? When a nuclear explosion happens is this what's going on, (in laymens terms bviously) somehow the atom is split, the protons and nuetrons are split, and the electron energy levels are split, this "strong nuclear force" holding, I guess when u think about, everything together get released and just "messes up" all the surrounding atoms?

Different systems of units give a different perspective or handle on nature. You need experience with more than one system, and with converting. Different specialties in physics and astronomy use their own units of convenience. even the electron volt, which you see everywhere, is not a metric unit. the metric unit of energy is the JOULE and the eevee is equal to 1.602176...x 10-19 joule. physicists are shamelessly uninhibited about using non-officially-sanctioned units. they will measure temperature and even mass in eevee. (instead of in Kelvin and Kilograms). And of course astronomers have their Lightyears and their Megaparsecs. How many kilometers do you su…

http://www.vega.org.uk/series/lectures/feynman/ the basics of light these are for general audience (OK if you have never even heard of complex numbers) they are very intuitive and visual Feynman was a good explainer it is a series of 4 video lectures from around 1968 given in New Zealand each lecture is somewhat over an hour, with questions from audience

Let me start by saying i'm neither a particle physicist nor do i know anything about modern quantum physics but some believe that neutrinos could be tachyons, others are convinced that they can't exist. Tachyons are a putative class of particles which are able to travel faster than the speed of light. Tachyons were first proposed by physicist Arnold Sommerfeld (1961), and named by Gerald Feinberg. The word tachyon derives from the Greek (tachus), meaning "speedy particle" Tachyons have the strange properties that, when they lose energy, they gain speed. Consequently, when tachyons gain energy, they slow down. The slowest speed possible for tachyons is the speed …

I have always heard light discribed as being both energy and matter. if its matter, it has to have mass. but according to E=MC^2, nothing with mass can reach the speed of light. so how can light reach light speed? my understanding of this stuff is limited, so sorry if im missing something important.

Hey, I'm new to the forum- decided to ask a question that wasn't answered in school! I get the idea that electromagnetic waves are released from photons, but I don't understand how the waves interact with anything if they don't have a mass. Also how do photons emit energy if they don't have a mass? Maybe it's a lack of detail in my syllabus, but it seems that I kind of missed something. Just a few weeks ago our teacher explained E=mc² to us. So there I am under the impression that only something with a mass has any energy (and can therefore give out energy). So how do photons first of all give off the energy (EM waves), and then how do the waves themselves int…

This should be impossible; but if a Neutron can decay into a proton and vice-versa, what am i missing; P -> e N N -> e+ P P -> e N When a N/P goes under beta decay; does it turn into a slightly lighter version of the differebt particle?

...the use of light in observations?

Hey, folks. An interesting article describing how quantum entanglement works, from first principles, using lots of pictures and no math. Quite good! http://www.joot.com/dave/writings/articles/entanglement/ Ciao! T

Spurred by other posts I was thinking the doesn't quantum entanglement, the links between the electron and the positron, defy relivity. Because can't entanglement provide an instaneous form of communication across the whole universe.

Right beta decay is when a neutron decays into a Positron/ Electron and netrion/ anti neutrino; my question is are there any laws regarding this or is it totally random of one of the 4 eventualities occuring; v, +e v, -e anti v, +e anti v, -e also if Beta and alpha decay occur at the same time, is just loads of helium made say, 1/1000th of an inch from the material when the particles are atracted to each other?

today Tuesday 4 January NYT --quote-- Philip W. Anderson Physicist and Nobel laureate, Princeton Is string theory a futile exercise as physics, as I believe it to be? It is an interesting mathematical specialty and has produced and will produce mathematics useful in other contexts, but it seems no more vital as mathematics than other areas of very abstract or specialized math, and doesn't on that basis justify the incredible amount of effort expended on it. My belief is based on the fact that string theory is the first science in hundreds of years to be pursued in pre-Baconian fashion, without any adequate experimental guidance. It proposes that Nature is t…

I have a question about how the wave function of particles collapses. I've heard that the wave function collapses when a particle interacts with another particle, but in the context of quantum mechanics, I'm not sure what "interact" or "collapsing of the wave function means". My understanding is as follows: The "wave function" is the perpetual propagation of the probability wave of a fundamental particle - a field of probability where the particle is most likely to be, and grows larger so long as no other particle interacts with it. Interaction in this case is kind of a fuzzy term since their positions are only probablistic. Is this understanding correct? Also, what w…

If the many worlds interpretation of quantum mechanics is true, then when did it start? when were the first two branches of reality created? the first mili-mili-mili-mili-mili-mili-mili-mili-mili second after the burst of energy that created the first matter and anti-matter right? so then wouldnt some branches of reality have a totally different universe resulting from even the slightest change in during the big bang? even one where you could do things liek...travel to other branches of reality?

Once again, I'm reading interesting info that's abou 11 years old. This came up: http://www.fourmilab.ch/documents/ohmygodpart.html That was in -94. Wikipedia tells me that at least 15 similar phenomenons have been detected since the first detection. Has there been any recent research of origin of the so-called Oh-My-God-particle(s)?

Okay, I've caught the first installment, and it taught me a great deal about string theory and the like, but I've got one question. Regarding dimensions, I'm aware of the aspect of this, but if it is true other dimensions exist, why is it we haven't seen any objects that are zero, one, or two dimensions? Is it because all objects are multidimensional and we can only observe what our senses, which are geared for three, see ? It's a fascinating series, but I'm trying to wrap my feeble brain around some big concepts here, and would appreciate some help here.

I've heard of the theory that states that object in a given dimension cast shadows of the dimension below them. Like how we cast two-dimensional shadows, and so on. But I'm having trouble understanding how it works. For instance, since we exist in time, we'd be fourth dimensional objects. And since shadows also have an area of displaced light between the visible shadow and the object casting the shadow, wouldn't they be three-dimensional? If someone could explain this to me in an understandable way, I'd appreciate it. Edit: Sorry, posted this in the wrong forum.

Many science fiction writers like the idea of anti-gravity. I was wondering how this would be possible. I know it is, because white holes have it. Scince mass bends space-time inwards, then apperently negative mass would bend space-time outwards. How could this be done?

Ok, I was reading through a few other threads, and I wondered...does a true vacuum exist in the universe? Something completely void of matter, and filled with absolute nothingness? Im sure if such a thing did exist, matter would rush in and out, trying to fill the vacuum. Another factor I figured on is the expanding universe. With the law of conservation of matter/energy, doesnt a vacuum have to be formed at some point? What I was initially thinking was this- I have just moved something (anything) to another dimension or universe (thus defying the law of conservation of matter/energy) What space that object has just occupied is now void of anything. What are the …