The Secrets of Quantum Physics

SpeedOfSound · **#441** by **SpeedOfSound** » Dec 19, 2014 11:20 pm

Templeton wrote:Oh please do encourage him...whether you find jamests thoughts right or wrong, at least he thinks...and doesn't just parrot, any idiot can do that...
Without his posts many here would be bored to tears...
Carry on

gee.

thanks.

DavidMcC · **#442** by **DavidMcC** » Dec 20, 2014 12:24 pm

Panderos wrote:
DavidMcC wrote:
Panderos wrote:
Thommo wrote:Particles and quanta cannot exceed the speed of light in free space "c".

I seem to remember Feynman saying this ins't really true in QED...?

Two points:
1. What goes for quanta does not necessarily apply to macroscopic objects.

Sure, I was responding to a point specifically about particles and quanta.
DavidMcC wrote:2. There has never been any evidence even to support Feyman's claim of particles travelling at FTL.

But would that not make the sum over paths calculations wrong? Isn't it necessary to take into account FTL paths to calculate probabilties accurately?

Only if you believe FTL is possible do you include FTL paths in the sum over paths, so it would be a self-fulfilling prophecy to claim that sum over paths proves FTL must occur.

Panderos · **#443** by **Panderos** » Dec 20, 2014 1:31 pm

Presumably including FTL paths would result in different predictions then. Has this been tested? Was Feynman proven wrong?

twistor59 · **#444** by **twistor59** » Dec 20, 2014 1:35 pm

Panderos wrote:Presumably including FTL paths would result in different predictions then. Has this been tested? Was Feynman proven wrong?

You must include FTL paths, Feynman was not wrong!

Panderos · **#445** by **Panderos** » Dec 20, 2014 1:44 pm

Ha!

Edit: So if that is the case, then presumably you can derive an equation which tells you the chance that an individual photon will travel x% faster than light?

DavidMcC · **#446** by **DavidMcC** » Dec 20, 2014 3:59 pm

There may be confusion here between the phase velocity of an EM wave-packet (which can be FTL, but does not transmit any information) and its group velocity (which cannot be FTL).

twistor59 · **#447** by **twistor59** » Dec 20, 2014 5:36 pm

Panderos wrote:Ha!

Edit: So if that is the case, then presumably you can derive an equation which tells you the chance that an individual photon will travel x% faster than light?

Not quite, a real photon in vacuum won't travel faster (or slower) than light. It's just that in the path integral the paths you include in the sum must include all paths, regardless of their speeds. However the individual paths have no significance on their own, only the *result* of the path integral (which is a big summation) has a physical significance. The contributing paths have phase factors attached to them and when you do the summation, these conspire to ensure that the final answer doesn't come out silly!

Panderos · **#448** by **Panderos** » Dec 20, 2014 5:49 pm

But surely they only conspire to make the chance very very low, not zero?

DavidMcC · **#449** by **DavidMcC** » Dec 20, 2014 8:45 pm

Panderos wrote:But surely they only conspire to make the chance very very low, not zero?

In a vacuum, zero.

twistor59 · **#450** by **twistor59** » Dec 20, 2014 9:12 pm

Panderos wrote:But surely they only conspire to make the chance very very low, not zero?

I was looking for an online version of Feynman's "Stange Theory of Light and Matter" - couldn't find one, but this link has a brief summary of some of the material. I strongly recommend that you take a look at that book if you're interested in this stuff.

Panderos · **#451** by **Panderos** » Dec 20, 2014 9:35 pm

I own a copy of QED if thats what you mean. That's where I'm getting what I'm saying from, although I haven't read it in a while and can't pretend I understood it all when I did.

Evolving · **#452** by **Evolving** » Dec 20, 2014 9:39 pm

I got an email from the New Scientist today saying this:

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Saturday 21 February 2015, 10am - 5pm / The British Library, London

Evolving · **#453** by **Evolving** » Dec 20, 2014 9:41 pm

Oh, and this is the link to buy tickets:

http://www.eventbrite.co.uk/e/instant-expert-the-quantum-world-tickets-14843925581?aff=em2

kennyc · **#454** by **kennyc** » Dec 20, 2014 9:54 pm

Certainly jamest will be there ..... right james??

surreptitious57 · **#455** by **surreptitious57** » Dec 21, 2014 10:14 am

I have read 13 Things That Don t Make Sense and I always watch
Jim when he is on BBC 4 too so both of them are perfect for this

kennyc · **#456** by **kennyc** » Dec 21, 2014 11:45 pm

We're still waiting jamest....

kennyc · **#457** by **kennyc** » Dec 22, 2014 12:36 pm

Yes jamest we're STILL waiting on your analysis and evidence as to why you believe QM supports your beliefs.

In the mean time, Ethan has something to say about philosowibble:

http://www.rationalskepticism.org/gener ... 47918.html

hackenslash · **#458** by **hackenslash** » Dec 23, 2014 11:54 am

I have only one question:

Now that you've done a complete U-Turn on the applicability of scientific evidence to metaphysical constructs, James, when can we expect responses to all the thousands of objections to your nonsense that you dismissed on that basis?

I'd respond to this topic, but it seems you have much work ahead of you rescuing your entire posting history after the catastrophic blunder you've committed in admitting all that evidence against your intellectual flatulence.

twistor59 · **#459** by **twistor59** » Dec 23, 2014 3:06 pm

Panderos wrote:I own a copy of QED if thats what you mean. That's where I'm getting what I'm saying from, although I haven't read it in a while and can't pretend I understood it all when I did.

Yeah I just retrieved my copy. He doesn't say as much about it as I thought. Basically, the Feynman propagator, which he refers to as his "amplitude to get from a to b" does have a very small but nonzero value outside the light one, but the whole interpretation of thinking of it in terms of the propagation of point particles doesn't really work in relativistic quantum theory. Relativistic single particle quantum mechanics has problems, which necessitate you going to a field theory which has multiple particles. There you still have the propagator with its nonzero value outside the light cone, but now its interpretation is as a correlation of two field values rather than as propagation of a particle (well you can still think of is as propagation of a virtual particle if you want, but that is not constrained to c). You can't send information using field correlations.
Shit I can't believe I've been posting in the philosophy forum.