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**Physics, Astronomy & Cosmology / Re: What happens when both slits are observed by in the double slit experiment?**

« **on:**07/11/2019 13:25:35 »

You really need to abandon the particle/wave duality business to make progress in physics. Photons, atoms, indeed everything, behaves as it does because it is what it is, not what you choose to model it as.

Quantum mechanics gives us an excellent predictive model of the behaviour of very small things, but doesn't say what they "are". Continuum mechanics gives us an adequately predictive model of mesoscopic entities that allows us to build houses and fly to the planets. The important question to ask of quantum mechanics is "does it scale up to the observed behaviour of radio waves and billiard balls?", which it does. Likewise the test of relativity is "does it scale down to Newtonian mechanics if v<<c?", which it does.

The problem with poking a particulate photon through two slits is manifold.

1. Only half the energy can go through each slit, so the wavelength of the emerging "photons" will be twice as long - but it isn't!

2. If we rotate the receiver, we will alter the time at which the two bits of photon reach it, so they can't interfere - but they do!

Equally, however, if we presume a wave passing through both slits, all the interference peaks will occur simultaneously, however weak the source (down to one photon at a time) - but they don't!

It gets even more exciting when we pass "solid" objects like electrons, atoms or buckyballs through a diffraction grating. There's no way they can disintegrate and recombine at the receptor (if we move the receptor further away, where does the recombination happen? If we remove it altogether, have we created partial electrons wandering through space?) but they form the predicted pattern!

The answer: believe what you see, and choose the most appropriate model to predict what you might see next time, but don't be surprised if something else happens - it just means your model was incomplete.

Quantum mechanics gives us an excellent predictive model of the behaviour of very small things, but doesn't say what they "are". Continuum mechanics gives us an adequately predictive model of mesoscopic entities that allows us to build houses and fly to the planets. The important question to ask of quantum mechanics is "does it scale up to the observed behaviour of radio waves and billiard balls?", which it does. Likewise the test of relativity is "does it scale down to Newtonian mechanics if v<<c?", which it does.

The problem with poking a particulate photon through two slits is manifold.

1. Only half the energy can go through each slit, so the wavelength of the emerging "photons" will be twice as long - but it isn't!

2. If we rotate the receiver, we will alter the time at which the two bits of photon reach it, so they can't interfere - but they do!

Equally, however, if we presume a wave passing through both slits, all the interference peaks will occur simultaneously, however weak the source (down to one photon at a time) - but they don't!

It gets even more exciting when we pass "solid" objects like electrons, atoms or buckyballs through a diffraction grating. There's no way they can disintegrate and recombine at the receptor (if we move the receptor further away, where does the recombination happen? If we remove it altogether, have we created partial electrons wandering through space?) but they form the predicted pattern!

The answer: believe what you see, and choose the most appropriate model to predict what you might see next time, but don't be surprised if something else happens - it just means your model was incomplete.

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