History UsefulNotes / QuantumPhysics

13th Mar '16 4:09:30 PM FordPrefect
Is there an issue? Send a Message


As with most other quantum phenomena, this is really only true of small particles; you should still expect classical mechanics to apply at the level of every day life. There is a non-zero probability that, for example, that remote control just out of reach might spontaneously fly to your hand without you having to get up. That non-zero probability is '''so''' small that you'll spend hundreds of billions of years waiting for it to happen. There's a non-zero probability that you could walk through the door of your office while it's still in the doorway. You go ahead and try; I'll bring the popcorn.

to:

As with most other quantum phenomena, this is really only true of small particles; you should still expect classical mechanics to apply at the level of every day life. There is a non-zero probability that, for example, that remote control just out of reach might spontaneously fly to your hand without you having to get up. That non-zero probability is '''so''' small that you'll spend hundreds of billions of years waiting for it to happen. There's a non-zero probability that you could walk through the door of your office while it's still in the doorway. You go ahead and try; I'll bring the popcorn.
[[PassThePopcorn popcorn]].



An obvious conclusion might be that each particle in fact had a state prior to the measurement, but this isn't the case. In quantum theory, and this has been born out by experiment, a particle that can occupy multiple states does so until a measurement forces it to only occupy one. This is the explanation behind the double slit experiment (see below). The particles of an entangled pair don't have a particular value until that value is measured and that information is transmitted, perhaps instantaneously, to the entangled partner.

to:

An obvious conclusion might be that each particle in fact had a state prior to the measurement, but this isn't the case. In quantum theory, and this has been born borne out by experiment, a particle that can occupy multiple states does so until a measurement forces it to only occupy one. This is the explanation behind the double slit experiment (see below). The particles of an entangled pair don't have a particular value until that value is measured and that information is transmitted, perhaps instantaneously, to the entangled partner.
13th Mar '16 4:05:11 PM FordPrefect
Is there an issue? Send a Message


* [[http://en.wikipedia.org/wiki/Quantum_superposition Superposition]]: in which subatomic particle can exist in two or more places at once. Well, states. And it's not just a particle that does this, it's a system.\\

to:

* [[http://en.wikipedia.org/wiki/Quantum_superposition Superposition]]: in which a subatomic particle can exist in two or more places at once. Well, states. And it's not just a particle that does this, it's a system.\\
13th Mar '16 4:01:00 PM FordPrefect
Is there an issue? Send a Message


Quantum Physics and Quantum Mechanics and Quantum Chromodynamics are famously difficult to understand. In truth, so long as you go into them with the assumption that everything will be weird and that that's okay, it's really not to difficult to get a handle on. Also, you have to spend half a decade studying math, but that's not a problem, right?

to:

Quantum Physics and Quantum Mechanics and Quantum Chromodynamics are famously difficult to understand. In truth, so long as you go into them with the assumption that everything will be weird and that that's okay, it's really not to too difficult to get a handle on. Also, you have to spend half a decade studying math, but that's not a problem, right?
13th Mar '16 4:00:33 PM FordPrefect
Is there an issue? Send a Message


That was the era of the ''Wunderkinder'' -- "child prodigies" -- in which brilliant young men of twenty-five to thirty-five years of age took the stage. The names of Heisenberg (no, not [[Series/BreakingBad that]] Heisenberg), Schrödinger, Feynman, Dirac, Freeman, and many others impressed themselves on the popular consciousness, and particularly on the scientific establishment. Einstein began the era with a bang in 1905, his ''annus mirabilis'', his Miracle Year, and the world never looked back.

to:

That was the era of the ''Wunderkinder'' -- "child prodigies" -- in which brilliant young men of twenty-five to thirty-five years of age took the stage. The names of Heisenberg (no, not [[Series/BreakingBad that]] Heisenberg), Schrödinger, Feynman, Dirac, Freeman, and many others impressed themselves on the popular consciousness, and particularly on the scientific establishment. Einstein began the era with a bang in 1905, his ''annus mirabilis'', his Miracle Year, mirabilis'' (Miracle Year), and the world never looked back.
30th Nov '15 9:31:29 AM FF32
Is there an issue? Send a Message


By the close of the nineteenth century, classical physics was beginning to reach the limits of what it could describe. It had mastered what RichardDawkins calls Middle Earth, the realm of the every day, but at the boundaries of the very large, the very small, and the very fast, it was breaking down and reaching insoluble dilemmas. A new model of the universe was needed, and a number of brilliant men and women were waiting to step into the gap with Quantum.

to:

By the close of the nineteenth century, classical physics was beginning to reach the limits of what it could describe. It had mastered what RichardDawkins UsefulNotes/RichardDawkins calls Middle Earth, the realm of the every day, but at the boundaries of the very large, the very small, and the very fast, it was breaking down and reaching insoluble dilemmas. A new model of the universe was needed, and a number of brilliant men and women were waiting to step into the gap with Quantum.
16th Aug '15 3:25:29 AM memetics
Is there an issue? Send a Message


* [[http://en.wikipedia.org/wiki/Wave_function_collapse Wave function collapse]]: Superposition tells us that a particle or system can exist in an indefinite (or definite) number of states. Until we look at a system, it exists in all of those states simultaneously, and to the degree determined by the amount of energy in the system and the energy of the states and the number of states and other factors. This condition is described by the wave function, which defines the states and their energies. Once we look at the system, however, the wave function collapses and the superposition of states is replaced by the system achieving a single defined state. This is known as collapsing the wave function and is part of the explanation behind the double-slit experiment (below).

to:

* [[http://en.wikipedia.org/wiki/Wave_function_collapse Wave function collapse]]: Superposition tells us that a particle or system can exist in an indefinite (or definite) number of states. Until we look at attempt a measurement of a system, it exists in all of those states simultaneously, and to the degree determined by the amount of energy in the system and the energy of the states and the number of states and other factors. This condition is described by the wave function, which defines the states and their energies. Once we look at take a measurement of the system, however, the wave function collapses and the superposition of states is replaced by the system achieving a single defined state. This is known as collapsing the wave function and is part of the explanation behind the double-slit experiment (below).
16th Aug '15 3:19:56 AM memetics
Is there an issue? Send a Message


For quantum particles, position and momentum are thus very different concepts than we're used to seeing on a daily basis. The end result of this is that a particle's location and momentum are not independent of one another and our knowledge of either limits and is limited by our knowledge of the other.

to:

For quantum particles, position and momentum are thus very different concepts than we're used to seeing on a daily basis. The end result of this is that a particle's location and momentum are not independent of one another and our knowledge measurement of either limits and is limited by our knowledge measurement of the other.
16th Aug '15 3:07:37 AM memetics
Is there an issue? Send a Message


The Quantum Leap is a popular and popularly misunderstood phrase. In popular parlance, it means a huge leap forward, i.e. "Physics took a quantum leap forward with the discovery of X, etc." The phrase has its genesis in the behavior of electrons. Recall that electrons can only exist in certain orbits about an atom. An electron at a lower energy level can absorb a photon of light (a quantum of energy) and leap to a higher energy level. Thus the quantum leap, wherein an electron moves from one discrete energy level to another, without crossing the intervening levels of energy. As such, a quantum leap is, by definition, one of the smallest possible leaps that could be made.

to:

The Quantum Leap is a popular and popularly misunderstood phrase. In popular parlance, it means a huge leap forward, i.e. "Physics took a quantum leap forward with the discovery of X, etc." The phrase has its genesis in the behavior of electrons. Recall that electrons can only exist in certain orbits about an atom. An electron at a lower energy level can absorb a photon of light (a quantum of energy) and leap to a higher energy level. Thus the quantum leap, wherein an electron moves from one discrete energy level to another, without crossing the intervening levels of energy. As such, a quantum leap is, by definition, one of the smallest possible leaps that could be made.
made. However, in the sense that the electron jumps practically instantly from one place of stability to a completely different place, across an intervening zone of instability, it can still be considered a tremendous leap, which therefore has the same sense as the popular notion of a "quantum leap."
6th Mar '15 6:53:30 PM TomSFox
Is there an issue? Send a Message


That was the era of the ''Wunderkinder'' -- the "wonder children" -- in which brilliant young men of twenty-five to thirty-five years of age took the stage. The names of Heisenberg (no, not [[Series/BreakingBad that]] Heisenberg), Schrödinger, Feynman, Dirac, Freeman, and many others impressed themselves on the popular consciousness, and particularly on the scientific establishment. Einstein began the era with a bang in 1905, his ''annus mirabilis'', his Miracle Year, and the world never looked back.

to:

That was the era of the ''Wunderkinder'' -- the "wonder children" "child prodigies" -- in which brilliant young men of twenty-five to thirty-five years of age took the stage. The names of Heisenberg (no, not [[Series/BreakingBad that]] Heisenberg), Schrödinger, Feynman, Dirac, Freeman, and many others impressed themselves on the popular consciousness, and particularly on the scientific establishment. Einstein began the era with a bang in 1905, his ''annus mirabilis'', his Miracle Year, and the world never looked back.
23rd Aug '14 2:42:46 PM Pigeon_
Is there an issue? Send a Message


* [[http://en.wikipedia.org/wiki/Uncertainty_principle Uncertainty Principle]]: If you want to measure the particle's position accurately, you must sacrifice the accuracy of its velocity, and vice versa. On a practical level, this can be understood as trying to find the position of a baseball by hitting it with another baseball. You cannot ''see'' a subatomic particle in any real sense; we see by interacting with light that bounces off of something, and light has roughly the same size and shape as a subatomic particle, definitely about the same wavelength. Therefore the interaction of a particle and a photon of light is like two baseballs colliding. You'll learn where it ''was'', but not where it was going, or vice versa.\\

to:

* [[http://en.wikipedia.org/wiki/Uncertainty_principle Uncertainty Principle]]: If you want to measure the particle's position accurately, you must sacrifice the accuracy of its velocity, and vice versa. On a practical level, All too often, this can be understood as is explained in terms of trying to find the position of a baseball by hitting it with another baseball. You baseball: "you cannot ''see'' a subatomic particle in any real sense; we see by interacting with light that bounces off of something, and light has roughly the same size and shape as a subatomic particle, definitely about the same wavelength. Therefore the interaction of a particle and a photon of light is like two baseballs colliding. You'll learn where it ''was'', but not where it was going, or vice versa.\\"\\



However, this isn't just a matter of pragmatism. It's a fundamental truth of reality. Thanks to wave-particle duality, a particle doesn't exist at a single defined location. Rather, they're smeared across a volume, existing more at some places than at others. The electron of a hydrogen atom is mostly inside the nucleus, but somewhat outside it, with the amount of the electron existing at any location decreasing with distance from the nucleus. This is sometimes called the 'electron cloud'.\\

to:

However, this isn't just That explanation is wrong, and misses the real point: even if we ''did'' have "perfect" measurement techniques that avoided the "baseball problem", they ''still wouldn't work''. It is not a matter case of pragmatism. It's simply being unable, for practical reasons, to measure position and momentum accurately at the same time; it is a fundamental truth case of reality.such a measurement being ''fundamentally impossible'' to make, because the two properties ''do not exist'' as accurately defined quantities at the same time. Thanks to wave-particle duality, a particle doesn't exist at a single defined location. Rather, they're smeared across a volume, existing more at some places than at others. The electron of a hydrogen atom is mostly inside the nucleus, but somewhat outside it, with the amount of the electron existing at any location decreasing with distance from the nucleus. This is sometimes called the 'electron cloud'.\\
This list shows the last 10 events of 76. Show all.
http://tvtropes.org/pmwiki/article_history.php?article=UsefulNotes.QuantumPhysics