What is quantum physics?

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i’m in ninth grade and we were talking a little bit about this in science class; like how with quantum physics it would be possible to open up wormholes and stuff and i was really interested in it. i read a book called called physics of the immpossible which was about the real science behind time travel and faster than light travel and it kept mentioning quantum physics but i didn’t really understand it. if someone could explain it just a little bit i would appreciate it. but i’m in ninth grade, remember, so please don’t use science terms that i probably wouldn’t understand. thanks!

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D.J.

Quantum physics is the study of the behavior of matter and energy at the molecular, atomic, nuclear, and even smaller microscopic levels. In the early 20th century, it was discovered that the laws that govern macroscopic objects do not function the same in such small realms.

sir readalot BOTTOM contributor

Quantum physics deals with the properties and phenomena of the subatomic realm, such as wave/particle duality, entanglement, non-locality, and the Heisenberg Uncertainty Principle. You can learn a lot more if you Google the topic.

Michael G

Quantum physics is the math that best predicts the behavior of tiny particals like atoms, electrons and many other forms of subatomical particals.

sal :o)

quantum physics is essentially the behaviour of the very very small.
like inside an atom – protons, neutrons and electrons (you learnt about them yet? i don’t know how you do things in america…)
it also includes the behaviour of light.
particles of light are ‘quanta’ – more commonly known as photons.
quantum physics also looks at how light behaves.
basically, light is both a particle AND a wave.
photons can interfere with themselves (like how ripples in a pond interfere) to give all sorts of effects. try googling ‘young’s two slit experiment’ and you’ll see what i mean.
there is more quantum physics but it does get rather mind-melting.
i recommend reading ‘quantum theory cannot hurt you’ by marcus chown. it’s a good explanation of it.

Mark L

quantum physics is smaller than physics where as astrophysics is large than physics.

Link

I could seriously write a book on this question. I think to really “get” quantum physics, it helps to understand some of the history behind it. Near the end of the 1800’s, physicists thought they had a pretty good understanding of the natural world. They figured that there were still a few minor unanswered questions, but these wouldn’t be too tough to understand. One of the unanswered questions dealt with temperature. You may have noticed that when you heat up a piece of metal it starts to glow. People realized that all objects with temperature give off some form of light. (it isn’t usually visible light unless the object is really hot) The frequency (color) of the light given off changes when the object’s temperature changes. Physicists, being the gigantic nerds that we are, then naturally wanted to predict theoretically what frequency of light would be emitted when an object is heated to a certain temperature. To simplify the problem, they studied an ideal object called a blackbody. A blackbody is one of those physics idealizations like a massless string that helps to understand the basic physics behind a situation without unecessary complexities. Simply put, a blackbody is an ideal object that doesn’t reflect any light…any light from a blackbody comes only from the light it gives off due to its temperature. The Sun is an example of a natural blackbody. (in fact, now days we use this blackbody stuff to determine the surface temperatures of stars by looking at their color…quantum physics is also useful in understanding something called spectroscopy, which helps us determine what the starts are made of) Anyway, there was a problem, the predictions made by the theory about how the color of the emitted light changed with temperature didn’t match up with experimental observations. In fact, the theory was WAY off for really hot objects glowing with ultraviolet light. Thus this mismatch of theory and experiment was call the ultraviolet catastrophe. Light is given off by charges undergoing acceleration and the light from a blackbody was thought of as being due to a whole bunch of teeny tiny charged oscillators in the blackbody wiggling back and forth. More temperature meant faster wiggling which lead to a shorter frequency of light. A guy named Plank finally managed to explain the experimentally observed frequency/temperature dependence by assuming that the little oscillators could only have certain fixed energies. He assumed that the oscillators couldn’t wiggle with any energy they wanted so it was like the oscillator energy came in little tiny packets called quanta (If I remember correctly, the word quanta is actually due to Einstein). This was a bizarre idea to the people of the early 1900’s. The idea of energy packets didn’t really catch on until Einstein used this quantum idea to explain the photoelectric effect. In the photoelectric effect, you basically shine light on a metal and get an electric current. It was a mystery as to why the energy of ejected electrons was dependent on the color of the incoming light and not the brightness. Einstein showed that this was a consequence of the idea that light energy comes in little packets just like the fixed energies of Plank’s oscillators. Thus Einstein revived the idea that light was made of little tiny particles. Still there are some properties of light that can only be understood by thinking of it as a wave. This led to the idea of complimentarity (wave-particle duality) which says that neither of these two ideas is really accurate but when taken together they can totally describe the behavior of light. Bohr, who came up with the idea of complimentarity, applied this quantum idea to the description of atoms. Eventually it was suggested from experiments with electrons that matter has this wave-particle duality too. Heisenberg suggested his uncertainty principle which says its impossible to know both the position and the momentum with 100% accuracy at the same time. You can know them both very accurately, just not with absolute certainty. If you know one with complete accuracy, you don’t know anything about the other. This raises philosophical questions about whether the object still has a 100% accurately defined position and momentem even though we can never know them. Does something you can never know anything about in principle still exist all the same? I can’t remember who, but someone compared this to the medieval theological question of “How many angels can sit on the head of a pin?” This ultimately led to the modern probabilistic interpretation of quantum physics where particles don’t have well defined properties until you measure them. Personally, I dislike our current view, but quantum physics works to describe experimental observations so there must be some truth to it. The thing I like most about quantum mechanics is the uncertainty principle. I think its probably one of the greatest ideas to come out of 20t

?

Hi, quantum mechanics is basically this:
At a microscopic level ‘particles’ of things like light and matter show the behaviour of both waves and particles. These are two contradictory properties and it would like something being both there and not there at the same time, or all red and all black at the same time. It is just not possible you would think. well it is found that if we test for a ‘red’ property for example, then we would fix the particle as red forever, but if we test for a black property then it will fix it as black. this is odd. It is also odd that this behaviour only occurs in very small things (there is no cut off point given in the equations of how large an object has to be so where do you draw the line?). Bohr suggested that this odd behaviour must cease because the quantum state ‘collapses’ when we measure it. This leads to indeterminacy as we can never know what state it will collapse into (we can only give probabilities). Another idea is that there is no boundary between quantum states and larger states, we all exist in both states at once. This is known as the Everett approach and shows that there must be an infinite amount of parallel universes. I have just done my dissertation on this for a MA in the Philosophy of Physics and have written a number of articles here:
http://www.thestargarden.co.uk/Quantum%20theory.html
http://www.thestargarden.co.uk/Quantum%20mechanics%20and%20tunnelling.html
http://www.thestargarden.co.uk/Quantum%20mechanics%20and%20holism.html
http://www.thestargarden.co.uk/measurement%20problem.html
http://www.thestargarden.co.uk/Everett%20Approach.html

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