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LHC to start up again

Zulu Romeo

Zulu Romeo

World Famous Starship Captain
Admiral
The Large Hadron Collider (LHC) could restart as early as this weekend after more than a year of repairs.

Officials have avoided giving an exact date for sending beams of protons around the 27km (17 mile) circular tunnel which houses the collider.

The LHC was first switched on in 2008, but had to be shut down when a faulty electrical connection caused one tonne of helium to leak into the tunnel.
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http://news.bbc.co.uk/1/hi/sci/tech/8364964.stm

I've been following the LHC's progress with some interest. Its story was what brought me into the SciTech forum in the first place, back in September 2008.

If the news report suggests a return to particle circulations very soon, it looks like we could start seeing collisions by next year. :bolian:
 
Everytime it mysteriously fails is one alternate timeline that bit the dust in a strangelet cascade...
 
CuttingEdge100 said:
Meredith,

I thought the Afshar experiment proves that there aren't alternative universes
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I'm not Meredith but there is no consensus over the interpretation of the results of that experiment, so it has not proved anything at this point. Personally I am not qualified to critique it however, maybe someone else would like a shot.
 
As I'm reading about that it looks like it's challenging complimentarity, the observation that things don't behave as particles and waves simultaneously. But the meaning of simultaneousness seems to be what the argument is over.

A photon is split using double slits where it is behaving as a wave. While in that wave like state, it can be passed through a lens which focuses an image of the two slits onto two separate detectors. If these detect individual photons, Afshar says you've got particle like behaviour at the detectors.

It's not really simultaneous, it's a bit later than, but nevertheless within the same experiment. Does the introduction of the lens allow the photons to become particle-like? Is the physics after the lens essentially a different experiment to what preceeds the lens?
 
It's quite a lot more elaborate than a traditional double slit experiment. The Wikipedia article on Afshar's experiment is pretty good.

http://en.wikipedia.org/wiki/Afshar_experiment

The trouble lies in getting my aging brain to sort between the competing refutations of Afshar's claims.

I fear the many worlds interpretation as it may imply the possibility of quantum immortatlity. Live forever as a increasingly crippled vegetable.
 
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CuttingEdge100 said:
Meredith,

I thought the Afshar experiment proves that there aren't alternative universes
Click to expand...

No expert myself, but I would be shaken to find out that our mastery of quantum physics is so great that we could prove there is no such thing as alternative universes. I am not even saying I necessarily believe the concept either way, but to actually be able to disprove it...
 
Sooner or later a hole in their wall is going to open up and a note is going come flying out saying "Please stop sending your split atoms into our universe."
 
Didn't the Afshar Experiment basically show that they could measure the speed and location of the particle at the same time, which would disprove the Heisenberg principle?


Great Mambo Chicken,

Why would the Many Worlds explanation suggest Quantum Immortality and why would Quantum Immortality mean you'd live forever as a progressively crippled individual?
 
CuttingEdge100 said:
Why would the Many Worlds explanation suggest Quantum Immortality and why would Quantum Immortality mean you'd live forever as a progressively crippled individual?
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It assumes that your consciousness, once formed, would always have a non-zero probability of continuing to exist in an every decreasing fraction of an infinite number of universes. You only experience the universe in which your consciousness continues. However, not every accident kills or doesn't kill you -- many simply leave you maimed, and you still have a non-zero probability of your consciousness surviving to infinity in that state. Not a pleasant prospect, I'm sure you'll agree.

See the following (incomplete) Wiki article:

http://en.wikipedia.org/wiki/Quantum_immortality

and links therein.

Quantum physics has this way of screwing with your mind. :eek:
 
CuttingEdge100 said:
Didn't the Afshar Experiment basically show that they could measure the speed and location of the particle at the same time, which would disprove the Heisenberg principle?
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At most (meaning it's disputed), the Afshar experiment showed that quantum particles can exhibit particle and wave properties at the same time.

That doesn't mean one can measure the location and momentum of a particle as precisely as one wants - meaning the Afshar experiment does nothing to disprove the Heisenberg principle.

And it certainly doesn't disprove the possibility of parallel universes.
 
Someone please remind me -- provided that you don't attempt to measure complementary wave and particle properties with absolute precision simultaneously, what principle of QM states that quantum objects can't exhibit particle and wave properties at the same time? Even in the two-slit experiment, it is possible to detect individual photons arriving at the detector thereby building up to form the classic interference pattern.

Hugh Everett (originator of the many worlds interpretation) and others, such as Mead, subscribe(d) to the wave-only view where the apparent existence of particles is an artifact of the observing apparatus. Others, such as Bohm and Ballentine, susbscribe(d) to the particle-only view (as in the pilot-wave model). I think the fact that this debate is still going on after many decades without clear experimental evidence one way or another probably signifies something profound, but I just don't have a clue what.
 
Great Mambo Chicken said:
Someone please remind me -- provided that you don't attempt to measure complementary wave and particle properties with absolute precision simultaneously, what principle of QM states that quantum objects can't exhibit particle and wave properties at the same time?
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The Complementarity Principle:

http://en.wikipedia.org/wiki/Complementarity_(physics)

The principle states that a particle can't exhibit at the same time FULL wave and particle properties.
However, a particle can exhibit simultaneously PARTIAL (as in, only parts of) wave and particle characteristics.
 
Great Mambo Chicken said:
ProtoAvatar said:
The Complementarity Principle:

http://en.wikipedia.org/wiki/Complementarity_(physics)

The principle states that a particle can't exhibit at the same time FULL wave and particle properties.
However, a particle can exhibit simultaneously PARTIAL (as in, only parts of) wave and particle characteristics.
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Precisely, full not partial. I don't think the Afshar experiment claims to violate the full case.
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If the Afshar experiment doesn't claim to create simultaneously full particle and wave properties in a quantum particle, then it can't claim to violate complementarity - that's because partial wave and particle properties in a given particle at a given time don't violate complementarity.
 
I think I'm beginning to get my head around this. I think the experiment is designed to show that information about the path of a photon (which pinhole it originated from) and about the interference pattern are observable simultaneously, which is not supposed to be possible. The following is a better description of the experiment, although it is biased towards its validity as support for the transactional interpretation of QM rather than the Copenhagen, many worlds, and other interpretations.

http://www.analogsf.com/0410/altview2.shtml

http://www.npl.washington.edu/npl/int_rep/ti_over/ti_over.html

The jury is still out. I like the ideas behind the transactional interpretation (not that my liking it is worth a damn, of course) but I'm not convinced that this experiment clinches it.
 
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Great Mambo Chicken said:
CuttingEdge100 said:
Why would the Many Worlds explanation suggest Quantum Immortality and why would Quantum Immortality mean you'd live forever as a progressively crippled individual?
Click to expand...

It assumes that your consciousness, once formed, would always have a non-zero probability of continuing to exist in an every decreasing fraction of an infinite number of universes. You only experience the universe in which your consciousness continues. However, not every accident kills or doesn't kill you -- many simply leave you maimed, and you still have a non-zero probability of your consciousness surviving to infinity in that state. Not a pleasant prospect, I'm sure you'll agree.

See the following (incomplete) Wiki article:

http://en.wikipedia.org/wiki/Quantum_immortality

and links therein.

Quantum physics has this way of screwing with your mind. :eek:
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So if I follow this correctly (and I am previously familiar with this territory)... there is a non-zero probabilityi n some alternate reality that I'm a paraplegic, or I'm a millionaire, or I live in a slum, or I'm a survivor of an alien invasion, or I'm Patrick Stewart's boyfriend, and in the tiniest minority of them I never die. Just like in the tiniest of minorities of them the chair I'm sitting on becomes non-cohesive 2 minutes from now and I fall through it.

In other words, why does it even matter what happens to "you" in another universe? Why would one automatically assume that our consciousness (or soul) is a constant across universal boundaries? It's an interesting thought experiment but until we can interact with these other realities (which may forever remain impossible) it's a bit irrelevant.
 
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