A very good video on quantum mechanics


by Forestman
Tags: mechanics, quantum, video
Jonnyb42
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#2
Apr11-11, 02:55 AM
P: 186
In the fourth video of that series, he says space and time are quantized. I thought that wasn't fully accepted yet? Am I wrong or if not, where is evidence that planck time and distance are really the shortest?
Terrakron
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#3
Nov26-11, 11:12 AM
PF Gold
P: 1
Have a look at the latest B. Greene video (Quantum Leap) in NOVA it is good as well.

Sarik Sadman
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#4
Feb9-12, 05:55 AM
P: 1

A very good video on quantum mechanics


why the wavelength would be perfect multiple, as described in this video?
Naty1
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#5
Feb9-12, 08:52 AM
P: 5,634
In the fourth video of that series, he says space and time are quantized. I thought that wasn't fully accepted yet?
correct.
You can check out "causal dynamic triangulation" as one example of a quantized view of spacetime. That's also been discussed in these forums.

In a recent discussion in these forums, a paper was referenced that presented the idea that "discrete" and "continuuous" spacetime are the same....there is no real distinction!
You can think of this concept in terms of an appropriate digital sample being able to fully replicate an analog information signal. Or even wave particle duality.
Naty1
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#6
Feb9-12, 09:10 AM
P: 5,634
why the wavelength would be perfect multiple, as described in this video?
Think of a violin string as an analogy: the ends are constrained, so it can have only certain tones...certain vibrational patterns and associated energies. it's energy levels are constained to certain values...it's degrees of freedom are limited.

Another helpful analogy is to think of the electron as a wave....when it's in free space the wave is everywhere, it extends all over the place. But when attracted by a proton in a nucleus, for example, that wave is now localized...it's constrained and so its different from the free space case. And the constraint is also modified by the presence of other electrons and additional protons. Since the energy is contained in the wave, changing it's configuration via the presence of nearby particles changes the wave characteristic and likely energy levels. It's very unlikely for the electron to be found between allowed energy levels.

In contrast, a free electron can take on any energy level. But when it is part of an atom or a larger structure, it's constrained...it's degrees of freedom are determined and limited by the whole structure. So an electron's energy levels and degrees of freedom are determined by the numbers of protons in the nucleus as as well as the particular structure of a lattice, as examples. The Schrodinger wave equation describes these.
yuiop
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#7
Feb18-12, 04:56 PM
P: 3,967
Quote Quote by Sarik Sadman View Post
why the wavelength would be perfect multiple, as described in this video?
It has to be a perfect multiple to solve the "Ultraviolet Catastrophy" or blackbody radiation problem. See http://www.physicsforums.com/blog.php?b=584

This problem was solved when Max Planck proposed that that energy came in discrete packets or quanta and is the the basis of Planck units. Although it is not fully accepted that space and time is quantized an alternative solution that solves the black body problem has not been produced. Quantizizing space causes a number of its own problems, but it can be shown that if time is quantized and the speed of light is a constant, that the black body problem (and a few other problems) can be solved by only requiring that time is quantizing. There is no need to quantize space.
patricia96
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#8
Feb26-12, 10:41 PM
P: 1
CK-12 Physics FlexBook has embedded videos on Quantum Mechanics which are simple and interactive. Moreover you will get theoretical detail to enhance the understanding of this concept.


Thanks
ThomasT
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#9
Feb27-12, 03:29 AM
P: 1,414
I don't think this is very good. The best way to learn quantum theory, imo, is to access the early papers on it. That is, learn something of the history of its development. Then get an early textbook, say, Bohm's 1950 "Quantum Theory", then access later textbooks and papers on it. Then, provided one understands all of the math presented, one should have a good grounding in the fundamentals of the quantum theory.
San K
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#10
Feb27-12, 10:17 AM
P: 915
good video. i like the idea...waves....in what?.......existence.....particles going in and out of existence.....the idea is speculative though.....
Trapezoidals
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#11
Mar24-12, 11:08 PM
P: 2
Guys,

This video is really telling us that equilateral triangles that the national institute of standards has produced is the foundation of all mathematics, chemistry, and physics. We ought to study the index of retractions of this plastic equilateral triangle prism and understand that the line spectra is merely from sunlight bending and separating as a result of this plastic prism. However, if we use another material...perhaps we can learn more about atoms and particles... Who knows? Perhaps we can actually understand position and momentum of electrons at the same time!
Piyush Mishra
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#12
Apr6-12, 05:13 AM
P: 1
I like quantum mechanics
mikeph
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#13
Apr10-12, 06:11 AM
P: 1,205
Quote Quote by Naty1 View Post
correct.
You can check out "causal dynamic triangulation" as one example of a quantized view of spacetime. That's also been discussed in these forums.

In a recent discussion in these forums, a paper was referenced that presented the idea that "discrete" and "continuuous" spacetime are the same....there is no real distinction!
You can think of this concept in terms of an appropriate digital sample being able to fully replicate an analog information signal. Or even wave particle duality.
What was this paper? Sounds very interesting
sweet springs
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#14
May3-12, 06:58 AM
P: 449
Hi. I recommend another video

Tonomura's electron double slit experiment without narration
http://www.youtube.com/watch?v=_oWRI-LwyC4
http://www.youtube.com/watch?v=FCoiy...eature=related
Dr. Tonomua passed away yesterday.
Regards.
Chouji12
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#15
May20-12, 07:39 PM
P: 5
It is funny to think that everything in physics is theorized. However, I simply have to say that this was a good video. I don't have enough physics knowledge to make references, just ideas. Funny how they showed a string at the end. If the universe is digital right now, does that make strings analog?
badamann
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#16
Jun28-12, 01:50 PM
P: 12
Okay, quantum physics is very new to me. I'm trying to grasp what's going on here. In the video, the speaker states, "The allowed orbits had to be exact multiples of the wavelengths calculated for the electrons. Other orbits produce destructive interference of the waves, and soon the electrons couldn't exist there."

I understand what's being said, but I don't understand why. What exactly is meant by 'destructive interference,' and why does it occur when the orbit of the electron isn't an exact multiple of the wavelength?
Naty1
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#17
Jul2-12, 05:33 PM
P: 5,634
What exactly is meant by 'destructive interference,' and why does it occur when the orbit of the electron isn't an exact multiple of the wavelength?
see

http://en.wikipedia.org/wiki/Constru...ence#Mechanism

I already described the physical interpretation in a post above.

The mathematics is summarized here and arises from quantum mechanics:

http://en.wikipedia.org/wiki/Atomic_...inty_Principle


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