Via Conor Friedersdorf blogging for Andrew Sullivan, here's a short Bloggingheads TV discussion on the Metaphysics of Quantum Mechanics:
See the whole episode here and more here.
"100 years ago physics began encountering things a little bit on the intelligible side." And: "at a quantum level sometimes reality in a certain sense doesn't take firm shape until its measured." If you're wondering what that means, see our more in-depth discussion with physicist Dylan Casey, here.
Frank Wilczek's rejection of the role of consciousness as "fringe" doesn't seem entirely on point to me (I'm not entirely clear if he's trying to characterize the Copenhagen interpretation, so I'm not sure). The point of the Copenhagen interpretation is not that reality at its most fundamental level is altered by consciousness. It's that at the quantum level the notions of position and velocity are intelligible only in the context of of measurement and the contribution of consciousness a the phenomenal level. This is to say they are something like Kantian phenomena, or Lockean secondary qualities ("red" as opposed to the primary quality of wavelength). We are cut off from the underlying real state of things, a level at which the paradox would, presumably, vanish. The Copenhagen interpretation may not be right, but I think I'm giving the correct account of the position here. See 1:08:30 of the podcast for more on this, including a direct quote from Heisenberg.
By: Wes Alwan
burl says
September 7, 2010 at 5:32 amI followed your second link to Sean Carroll saying *about 9 min +) that we change the overall wave state with an observation, and people should not get so wound up about this. http://bloggingheads.tv/diavlogs/13487
In one of his 12 hours of QM lectures online, Leo Suskind shares the same attitude, showing how the energy of the measurement ‘camera’ needed to accurately specify, say, the location of a photon, closely approaches the same wavelength magnitude as that of the particle itself, and cannot help but interfere with the photon’s behavior. A less accurate probe will affect the proton less, but will provide a less certain location.
We see this in everyday science. Take bridge design/analysis, for instance. You can use structural theory to design and build a bridge to safely support an 18 wheeler that weighs twice the legally permissible weight of such a rig. This means the structure has an inherent factor of safety against collapse of 2. You can only 100% verify the accuracy of your theory ONCE – by putting an actual double-legal-weight 18 wheeler on the existing bridge. You are more likely gonna test with a lesser weight overload (say 1.5 times the legal 18 wheeler weight), observe the tendency towards failure, and make a probabilistic prediction based on theoretical modeling, that within a confidence level of X, the bridge is safe. This is called bridge rating thru Non Destructive load Testing.
Quantum measurements are a form of NDT. Note that by putting a load that approaches the failure load, we will not cause a failure, but we have taken away a hard-to-determine amount of useful bridge life by so over stressing (= more carefully observing) the ‘bridge particle’
burl says
September 7, 2010 at 6:26 amI followed your second link to Sean Carroll saying (~9 min in) that we change the overall wave state with an observation, and people should not get so wound up about this. http://bloggingheads.tv/diavlogs/13487
In one of his 12 hours of QM lectures online, Leo Suskind shares the same attitude, showing how the energy of the measurement ‘camera’ needed to accurately specify, say, the location of a photon, closely approaches the same wavelength or amplitude as that of the particle itself, and cannot help but interfere with the photon’s behavior. A less accurate probe (less wavelength or amplitude) will affect the proton less, but will provide a less certain location.
We see this in everyday science. Take bridge design/analysis, for instance. You can use structural theory to design and build a bridge to safely support an 18 wheeler that weighs twice the legally permissible weight of such a rig. This means the structure has an inherent factor of safety against collapse of 2. You can only 100% verify the accuracy of your theory ONCE – by putting an actual double-legal-weight 18 wheeler on the existing bridge. You are more likely gonna test with a lesser weight overload (say 1.5 times the legal 18 wheeler weight), observe the tendency towards failure, and make a probabilistic prediction based on theoretical modeling, that within a confidence level of X, the bridge is safe for a truck 2 times the legal load. This is called bridge rating thru Non Destructive load Testing.
Quantum measurements are a form of NDT.
burl says
September 7, 2010 at 6:27 amThought I was editing for clarity, sorry for double post.
burl says
September 7, 2010 at 12:31 pm“Quantum measurements are a form of NDT.”
I forgot the important point: quantum measurement to gain certainty – like location or momentum – is a one-off event of Destructive Testing which, like for the bridge, causes a collapse of sorts (the wave function).
This is how I understand it, and am open to being totally discredited!
Wes Alwan says
September 7, 2010 at 1:36 pmHi Burl, it’s not simply a matter of an instrument interfering with what’s being observed (if it were, there would be nothing mysterious about quantum mechanics). While Heisenberg shows that in fact you can derive the same formulas from experiments which have such interference–entirely from the effects of that interference–as those without, there are in fact experimental results which cannot be attributed to such interference. So while it’s true, for instance, that in the dual slit experiment that a narrowing of the slit to pinpoint position while increase wave diffraction and so make more uncertain the velocity, one can’t in any intuitive way explain the fact that the behavior of a single photon going through one slit depends on whether the other is open (interference seemingly without anything interfering).
RE, Bridges: it sounds like you and I do something similar for a living.
burl says
September 7, 2010 at 1:54 pmDoctoral thesis on inelastic analysis of steel bridges.
Wes Alwan says
September 7, 2010 at 2:24 pmI’m a technical writer focusing on engineering related to transportation infrastructure — I read a lot of reports probably very much like your thesis.
burl says
September 7, 2010 at 2:35 pmWhat is today’s projected cost to bring the national infrastructure up to standard? I am wondering how this compares with Obama’s current push for another $50B (in addition to the $150B of the $800B stimulus outlay).
AFAIR, 20 years ago, FHWA reported that 40% of the nation’s bridges were structurally deficient, and I am pretty sure we haven’t done a thing to improve this.