[lightarrow]

Basically in a stable atom of say hydrogen, the electron orbits the proton,

They have already answered you that the electron doesn't "orbit" the proton; I would only like to ask you if you believe that the electron in the H atom is a little corpuscle.

Considering that this post is from 2010 and Murchie was last active in 2011, I suspect he might not answer you.  :p

Gasp! I haven't noticed.
Thank you.

[JP]

Bill, the "bra" and "ket" are fancy words for shorthand notation used to express the rather complex mathematics of quantum mechanical models.  The short answer is that you can interpret them in this case as mathematical descriptions of the particle's waviness.  That waviness describes where you're likely to find the particle if you look for it as well as describing how it interacts with other objects.  The difference with the Bohr model is that Bohr thought the wave was basically a sine wave wiggling around a circle about the nucleus, so that you could be certain the particle was somewhere on that circle. (http://en.wikipedia.org/wiki/Bohr_model) That worked out OK for some things, but wasn't very accurate.  Others came along and worked out in detail the physical model that governed the wave's behavior and its much more complicated than a simple sine wave: http://en.wikipedia.org/wiki/Atomic_orbital 

[lightarrow]

For example; what is a "position bra" (under-wired ?  ), or a "state ket", and what is the significance of < | and | >. 

It depends on the level of the answer  []
A ket is a state vector, a bra is a linear functional which associate a complex number to a ket.
But I suspect you would prefer something simpler.

In qm you use "wavefunctions" which are complex valued functions of x, y, z, t and which describe the qm system (for ex. a particle): the wavefunction codify the informations about the state of the system. But you need to make the scalar product of two wavefunctions f(x,y,z,t) and g(x,y,z,t); this is represented with the symbol: <f,g> and it is usually computed as:

<f,g> = Integral[-oo,+oo] f*(x,y,z,t) g(x,y,z,t) dxdydz

where f* indicates the complex coniugated of f.

It turns out that the integral is much better viewed as a function which associate a complex number (the result of the integral) to the function g, given the function f, so it is a "functional", that is something which take a function and returns a scalar (instead a normal function takes a scalar and returns a scalar).

Dirac invented this notation: the scalar product can be viewed as the functional <f| applied to the function |g> and becomes, simply: <f|g>. Since it was formerly represented with a "bracket": (f,g), he said that the firs part is the "bra" and the second the "ket"  [] and so the name.

[syhprum]

It is strange how old topics come back to life and that this should appear when I opened a relevant discussion on the Schrodinger equation

[Pmb]

Maybe Pete, but I would like to think that philosophy also drives science, and choice of experiments, with the science produced from those ideas and experiments in its turn driving philosophy. As science change so do philosophy. Depending on views there was different science produced historically, with those fitting the experiments at the time defining new philosophy. Just look at Stanford.edu, and the wealth of good scientific philosophy it contains.

I'll say this. From one of my favorite texts - Ignoring philosophy in physics means not understanding physics. - Fritz Rohrlich

[Pmb]

Pete, whilst I am happy to accept that the earlier explanations are wrong, they are the sort of explanation that one finds in P S books.  I feel, therefore, it is quite important that counter explanations should be such that the average reader of P S books (hitch-hikers on the journey of scientific understanding) should be able to understand them.

For example; what is a "position bra" (under-wired ?  ), or a "state ket", and what is the significance of < | and | >.

I explain all this on my website at http://home.comcast.net/~peter.m.brown/qm/state_space.htm