waves

[Alaskans]

This is perhaps a bit of worthless info. I have heard how in quantum mechanics when you arent looking at something it is in a wave form, when you do, it changes. It could be that this wave form is what some people are seeing; ripples of light across surfaces. Being able to see quantum phenomina with the naked eye (or psychic sense) to me seems to be one bridge linking metaphysics with accepted science.

[MisterJingo]

This is something call wave particle duality. It comes down to something called the double slit experiment, where a detector is used to determine if a wave or particle hits it. If a single photo is fired at a barrier with two slits in it, the detector picks up interference patterns (these occur with waves); this seems to suggest that the particle interacts with itself and goes through both slits at the same time. If we close one slit, the detector shows a single particle hit it.
Why this occurs is still open to debate, but recently there have been ideas which might overturn log held beliefs on this subject:

IT ROCKED quantum theory when it was first proposed in 2004, unleashing a dam-burst of vitriol in the physics community. Now the controversial experiment that questions our understanding of the wave-and-particle nature of light has finally been published, forcing some of its initial opponents to take it seriously.

The experiment, carried out by physicist Shahriar Afshar - then at the private, Boston-based Institute for Radiation-Induced Mass Studies - challenges a principle proposed by Niels Bohr 80 years ago. It relates to subatomic entities such as electrons and photons that seem to behave as if they were particles in some experiments and as waves in others.

According to Bohr, these wave-like and particle-like properties are complementary - no experiment can reveal both at once. Until Afshar's results, no experiment had seemed to contradict this principle.

When Afshar went public with his first findings in New Scientist (24 July 2004, p 30), he raised a storm of criticism. "I even had my religion and ethnicity attacked," says Afshar, an Iranian-American, now at Rowan University in Glassboro, New Jersey.

"This was especially unfortunate," says Antony Valentini of the Perimeter Institute for Theoretical Physics near Toronto, Canada. "One can understand that different people interpret the experiment differently, but that he should have had such trouble is peculiar."

Afshar believes the simplicity of his experiment - which could be done for $20 in a high-school lab - made people feel it could not be right. "Nevertheless, it's hard to understand how anyone could not see that this was an intriguing experiment," says Valentini.

"There were a few times when I felt like giving up because of the emotional intensity of the opposition," says Afshar. However, he persevered and has now refined his experiment so that he can measure the path of photons - the particles of light - while also observing their wave-like interference pattern.

His set-up is based on the classic "double-slit" experiment that first showed the wave-like properties of light. In that experiment, light is shone onto a screen with two pinholes in it. The light that passes through the pinholes fans out from them like ripples from a stone thrown into a pond and produces an interference pattern of light and dark fringes where the spreading waves either reinforce or cancel each other.

Afshar's apparatus is similar, but with a lens on the far side of the pinhole screen (see Diagram). The lens refocuses the spreading beams onto two mirrors, which reflect them onto two photon detectors, allowing Afshar to work out the path taken by the photons. According to Bohr's complementarity principle, that means there should be no evidence of an interference pattern, as Afshar is observing the light as particles, not waves.

However, Afshar observes the interference indirectly, by placing wires in front of the lens at the positions where he would expect the dark, lightless fringes of an interference pattern to be. If the photons do not interfere, Afshar argues, there will be no dark fringes and the wires will block some of the photons hitting the lens, reducing the photon count at the detectors. No such dip in the signal is seen - implying that the light does form an interference pattern, violating the complementarity principle.

The revised experiment is being published in the journal Foundations of Physics (vol 37, p 295), which is currently edited by Nobel laureate physicist Gerard't Hooft, who also believes that there are fundamental problems with quantum theory (New Scientist, 6 May 2006, p . Afshar himself now hopes for a more cool-headed discussion of his work. "I do think he was treated unfairly," says Lucien Hardy, also at the Perimeter Institute, who was initially sceptical about the experiment, but has now been won round.

Neil Gunther, a physicist at Performance Dynamics in Castro Valley, near San Francisco, interprets Afshar's findings in a way that does not violate Bohr, and is now designing an experiment to test that theory. "Afshar may have inadvertently put his finger on some new physics that could have important implications for quantum imaging," he says.

[Alaskans]

Hmm that article is a little hard for me to understand. I read scientific american a lot but still I cant make much sence of it. Is it saying that a single photon registers as though there were multiple photons in this experiment? It sounds like the atom duality and triality (when the dual atoms combine it makes a 3rd one, it's a 3 mode 'switch') used in the experemental quantum computers. I dont see why it would be so contraversial to find light acts the same way..

[MisterJingo]

Hmm that article is a little hard for me to understand. I read scientific american a lot but still I cant make much sence of it. Is it saying that a single photon registers as though there were multiple photons in this experiment? It sounds like the atom duality and triality (when the dual atoms combine it makes a 3rd one, it's a 3 mode 'switch') used in the experemental quantum computers. I dont see why it would be so contraversial to find light acts the same way..

Imagine a board with two slots in it



On the right side of it is a particle emitter which fires a single particle at the board. On the other side of the board is a detector which shows when then particle hits it.
If we close one slot and fire a particle at the board, the detector shows a single hit, if we open both slots and fire a particle at the board, the detector now shows an interference pattern



An interference pattern occurs when two waves hit each other, some of the waves will cancel each other out, and some waves will reinforce each other. This gives the stripy pattern seen above.
The interference pattern occurring from a single particle shows that the particle actually went through both slots at the same time and interfered with itself before hitting the detector.

The reason this is controversial is that a single object can be in multiple places at the same time. There is a lot more theory behind this, but this explains the basics of it.

[Mydral]

Thought about this problem:

Now they are saying that 1 particle of light is at two places at once. I don't see why this is such a huge problem. If the source of the light can shine at both slits at the same time, hence the slits are in the diameter of the light wave, they will also be in diameter of the light particle.
I will try to explain it differantly. Lets say you have two holes in a board 5 cm apart. Now you take a 6cm stick and hold it over the holes so it covers both. The stick is your light particle, its a both holes at the same time. If it would be light it would pass through and interfere with each other.

The thing is what if a light particle is as big as the diameter the light makes and spreads in the same way a light wave would in a repeating pulse?

[Daniel17]

http://www.whatthebleep.com/trailer/doubleslit.wm.low.html
check that video out, very very interesting