The most beautiful equation is… Einstein's field equation

[josephpalazzo]

It's one equation until you have to write FORTRAN code for it. Then it becomes this hairy piece of shit that's a pain to document, like I had to do one summer for my friendly neighborhood GR department. Next time, you can document your own code, fellas!

I guess you were never asked to program a Feynman diagram, which can contain literally thousands of terms, and that would be only for one single diagram, and there a gazillion of those diagrams for a single calculation such as the decay of a muon. Yes, GR is a lot simpler than you think...;-)

[Baruch]

I am told, by people who know, that in practical terms, only the first five loops of Feynman diagrams can usually be calculated, except for toy problems like the Lamb Shift ;-)  What use is a theory that can't calculate real situations?  GR is simple, because it usually is used to deal with toy situations in a toy-like way (the square terms added to the linear terms are usually enough).  QFT is as you describe, where you have to go well past the square terms of the perturbation.  Linear/square terms are exercises for the college students.  GR that is used for GPS ... is not something you give to college students either ... just the Schwartzchild or other highly symmetric analytic solutions.  All analytic solutions are toy solutions ... real problems require asymptotic analysis (Feynman diagrams) or (unstable) numerical calculation.

Most people's view of science/math is like Ohm's Law of electricity plus Kirchhoff's Laws of circuits.  Very simple stuff, but it can easily be calculated.  The legitimately intransigent maths of real science, is only accessible to experts, but then they can be mystagogues like Bohr and Einstein.

[josephpalazzo]

  What use is a theory that can't calculate real situations? 

FYI, in QCD, people can calculate jet streams, their intensity, the angles at which these jets come out of collisions, decay rates, the mass of the particles involved in those jets. Considering that at the LHC, you are colliding gazillions of protons coming one way, against gazillions of protons coming from the opposite ways, such collisions would be unpredictable as to what the fallout could be, yet, people can do amazing calculations that are then verifiable.

[Baruch]

Fortunately the pseudo-random behavior of quantum systems isn't so pernicious as to defy calculation to at least a few significant digits.  If things were as random as raw Heisenberg Uncertainly principle would allow, you could get a couch cushion coming out of the LHC ;-)  Like dice ... you can get a 1 ... 6, on a single dice role, but you can't get a 0 or a 7.

[josephpalazzo]

Fortunately the pseudo-random behavior of quantum systems isn't so pernicious as to defy calculation to at least a few significant digits.  If things were as random as raw Heisenberg Uncertainly principle would allow, you could get a couch cushion coming out of the LHC ;-)  Like dice ... you can get a 1 ... 6, on a single dice role, but you can't get a 0 or a 7.

You see, only someone like you, and unfortunately many others, who don't understand the HUP would say that kind of stuff. Though QM is a probability theory, besides that mathematical framework, it has little to do with the randomness of rolling a pair of dice. I say "unfortunately" because there is a smorgasbord of websites perpetuating this false notion.

[Baruch]

You see, only someone like you, and unfortunately many others, who don't understand the HUP would say that kind of stuff. Though QM is a probability theory, besides that mathematical framework, it has little to do with the randomness of rolling a pair of dice. I say "unfortunately" because there is a smorgasbord of websites perpetuating this false notion.

Yes, you are right, I have simplified.  With a polarized photon, in some arrangements, the only possibility is up/down or right/left ... and in those circumstances you get exactly half one way and half the other.  That is analogized to a coin toss.  But QM isn't just applied statistics ... there is a framework (Hilbert space operators etc).  And there is a difference between intrinsic and extrinsic probability ... QM having both, classical physics only the latter.  Intrinsic probability is ... because how things are ... not because of experimental error.

[Hakurei Reimu]

I guess you were never asked to program a Feynman diagram, which can contain literally thousands of terms, and that would be only for one single diagram, and there a gazillion of those diagrams for a single calculation such as the decay of a muon. Yes, GR is a lot simpler than you think...;-)

But apparently not the code I documented. Thousands of little fiddly bits, easy.

[josephpalazzo]

But apparently not the code I documented. Thousands of little fiddly bits, easy.

In the case of QFT, make that millions "little fiddly bits"...

[josephpalazzo]

Yes, you are right, I have simplified.  With a polarized photon, in some arrangements, the only possibility is up/down or right/left ... and in those circumstances you get exactly half one way and half the other.  That is analogized to a coin toss.  But QM isn't just applied statistics ... there is a framework (Hilbert space operators etc).  And there is a difference between intrinsic and extrinsic probability ... QM having both, classical physics only the latter.  Intrinsic probability is ... because how things are ... not because of experimental error.

More internet clichés. On a side note: Rolling a die and say you can get any number, say the number 5, is one chance out of 6 is not an experimental error.

QM has nothing to do with any of that, it has to do with measurement. Any time you measure at the atomic scale you disturb the system so that what you measure is a result from your act of measurement. Case 1: you have a car moving along a trajectory, you want to measure its velocity. You need to observe the car at position x1, t1 and at least another point x2,t2. However, substitute the car for an electron, and everything changes. Why, because the photon is strong enough to send the electron on a different trajectory. You'll know where the photon was (x1, t1) but now you don't know where it's going (momentum is undetermined). Case 2: you want to measure the spin of an electron, so you need to pass it into a magnetic field. But the electron is a tiny magnet, so when it enters the magnetic field, it will tilt in such a way that its component along the magnetic field will either align with the field or anti-align. What was its initial spin, you won't know as the other two components are unknown. Plus, your act of making a measurement changed its initial orientation. That's at the heart of the HUP: whenever you want to measure at those scales, you will disturb the system, hence you only get some partial knowledge of the system, but never all of the information, what was the initial quantum state before the act measurement is totally unknown, and there is nothing you can - that is, come up with some other experiment - to circumvent the HUP.

[aitm]

I still have problems with "Pies are squared"…….

[stromboli]

I still have problems with "Pies are squared"…….

The only fields I am familiar with have cow shit and daisies growing in them.

(edit) I felt compelled to share that, btw.

[josephpalazzo]

I still have problems with "Pies are squared"…….

Most sources of energy spread out spherically. So "spheres" means "circles", and "circles" means pi.


OTOH, a piece of pie always tastes better with a scoop of ice scream. Ha! it's just God working in mysterious ways...

[Baruch]

With relativistic rotation, the circumference is contracted ... so Pi is the maximum, not the minimum value of the circumference to the radius ... empirically.  There is no world of forms of Pythagoras/Plato.  Everything is empirical, except when it is only semi-empirical.

[josephpalazzo]

so Pi is the maximum, not the minimum value of the circumference to the radius ...

Which part of "pi is a number, hence a constant" don't you understand???

[josephpalazzo]

The only fields I am familiar with have cow shit and daisies growing in them.

(edit) I felt compelled to share that, btw.

I thought the thread "Topic: Post your funny pictures here!!! part Deux" was where you post silly stuff... :021: