#particle-wave duality

[wikipediagrams]

[kalyan-gullapalli]

Post # 152

"Stop telling God what to do!"

The years 1900 to 1930 were called The thirty years that shook Physics. Because, with the dawn of the new century (1900), a new stream of physics emerged that threatened to shake the very foundations of science. It was called Quantum Physics.

Till the early 1900s, the most accepted theories of mechanics were called Classical Physics or Classical Mechanics. These theories, very clearly, explained the laws governing everyday objects - objects that we see and deal with in our daily lives, like cars, trains, balls etc, as well as large objects, like the Sun, Moon, planets, galaxies etc.

Sir Issac Newton, the father of Classical Physics, explained gravity, inertia, motion, momentum, speed etc. Einstein proposed the General and the Special Theories of Relativity that explained concepts like space-time for very distant objects. That won him a Nobel Prize and made him the first ever science-rockstar.

So far so good. Classical Mechanics was doing a great job. It was precise and deterministic - means, we could predict the position of Jupiter on its orbit around the Sun, 20 years from today, using the mathematics of Classical Mechanics.

Of course, there were still many unanswered questions. And a whole host of physicists were working on them. But it was Business As Usual (BAU).

Towards the start of the 20th century, a few Europeans - Max Plank, Niels Bohr, Shrodinger, Heisenberg and many others - observed that the laws governing everyday or large objects do not explain the behaviour of sub-atomic particles (particles within an atom). The discovery of the electrons, protons and neutrons led to a spate of experiments, debates and theories, which together were called Quantum Physics or Quantum Mechanics.

Truth be told, Scientists found Quantum Mechanics bizzare! Even till date, scientists still find the theories of Quantum Mechanics hard to grasp. But none of them could or can, dispute the results of Quantum Mechanics. In fact, Quantum Mechanics is universally considered to be the most successful theory propounded by science. It ushered in the Information Age. Lasers, Semiconductors, Computers, Telecommunications, Televisions, Electronics etc, all owe their existence to the application of the concepts of Quantum Mechanics.

Quantum Mechanics works. Its math works. No problem. The only problem is - no one knows how it works or why it works that way! That's why many scientists believe Quantum Mechanics is more a branch of philosophy than of science.

Quantum Mechanics spooked the greatest mind ever believed to have walked this earth - Albert Einstein. He famously said - God doesn't play dice! You will see what he meant as you read on.

Niels Bohr, the Great Dane (he was Danish), worked to defend the theories of Quantum Mechanics. Exasperated by Einstein’s repeated attacks on the Quantum model, he is supposed to have retorted - Einstein, Don't tell God what to do!

This tension between Classical Mechanics and Quantum Mechanics went on for a long time and was also called The thirty years war.

I have been reading up on Quantum Mechanics for some time now. Like layers of an onion, I keep getting clarity on one aspect after another, all in due course. I am still a long way from getting it all, but I find it all so fascinating that I want to share it with you. And I think a good way to understand all of this is by understanding what was called The Double Slit Experiment. Here goes!

Consider a bunch of marble balls, shot through a double-slit barrier (a barrier with two holes on it) onto a board placed behind it. They will create a distinct pattern on the board, hitting it straight where they were allowed to pass through. The remaining part of background board will be untouched. Why? Because particles travel in a straight line. That's their fundamental nature. That's Classical Mechanics. Simple so far?

What if a bunch of electrons were to be shot through the same double-slit arrangement onto the same background board? How would they behave? What pattern would they create on the background board? Since all matter consists of atoms, and electrons are a part of atoms, so electrons should behave like particles, right? But they behaved very strangely. They created the below pattern on the background board.

There were stripes of alternately bright and dark patterns on the background board. Some electrons even hit the board straight behind the opaque parts of the double-slit barrier. How's that possible? The background board looked something like this.

The scientists conducting the experiments knew what this pattern meant. This pattern could only be made by a wave, not by a particle. The below 4-second video explains how a wave creates this pattern. By the way, this pattern is called an Interference pattern.

How's this possible? Was it possible that electrons were waves? But that is absurd. They were particles - sub-atomic particles.

So, scientists reluctantly came to a bizzare conclusion - Electrons were both particles and waves!

Further experiments were even more bizzare. Scientists now decided, not to observe only the pattern on the background board, but to observe the electrons also. What they found made them think they had gone crazy!

The moment their observation apparatus was switched on, electrons reverted to their particle behavior. But when the observation apparatus was switched off, the electrons took on their wave character. Look at the interference pattern on the background board.

Spooky, right? Someone articulated these observations as below.

Observation changed the nature of electrons! An unobserved electron has a wave function. An observed electron has a particle function.

From here on, it gets even more bizzare, if that is possible.

One quantum physicist suggested that the wave function of an electron suggests the probability of finding it at any particular point. If that point is a crest (a wave's highest point), the probability of finding it there is maximum. If the point is a trough (a wave's lowest point), the probability of finding it there is the lowest. But to find it, you have to observe it. And the moment you observe it, the electron takes a particle nature. With particles, life is simple. The electron is either there or not there. No probability. Absolute certainty.

When Einstein heard this, he blew his top. Probability, my foot! This is not Science, he must have thought. "God doesn't play dice!", he asserted out loud. He said this once too often, without offering an alternative explanation.

Niels Bohr, who was also struggling to reconcile with the bizzare conclusions of Quantum theories, but convinced that the consistency of the results of the experiments was proof enough that the theory was right, retorted, "Einstein, Stop telling God what to do and what not to do."

Niels Bohr was awarded the Nobel Prize in 1922 for his work in understanding the theories of Quantum Mechanics.

Almost a century has passed between then and now. In the intervening times, Quantum Mechanics has proposed many more bizzare theories like Heisenberg's uncertainty principle, Quantum Entanglement, Quantum Teleportation etc. Unanswered questions about a Unified theory of everything led modern science to propose strange and stranger theories like String theory, Multiverses (multiple universes) and Cosmic holograms.

I have just begun my journey of understanding the frontiers of modern science. And I cannot help but observe the stark parallels between what modern science is dabbling with today and the timeless tenets of Sanatana Dharma. More on it later!

[nuanimistdatabase]

Article: First image of the shape of a single photon revealed in light study

First image of the shape of a single photon revealed in light study

First image of the shape of a single photon revealed in light study

The first direct visualization of the shape of a photon has been created. These particles of light are impossible to photograph, but physici

[random2908]

The photoelectric effect is not an unequivocal demonstration of the particle nature of light. It can also be explained with entirely wave-based light, but discrete energy levels in materials. (The math is uglier that way, but it can be done.)

I had a professor who hated that that’s always the go-to example of light being particles, and that peeve basically rubbed off on all of his students.

There are, in fact, a couple of phenomena that can only be explained by saying light is particles. If there weren’t then--if everything could be sufficiently explained by waves and invoking particles only made the math easier, as is the case in the photoelectric effect, then we’d say light is just a wave and treating it as a particle is just a mathematical trick. (In fact, as far as has been discovered so far, this is the situation with sound--that there are phenomena where calling it a particle makes the math easier but there aren’t any known phenomena where calling it a particle is absolutely necessary.)

So stop using it as an example.

(Plus it’s also a dumb example for explaining to lay people because how many random people actually know what the photoelectric effect even is.)

[non-existentbandnames]

I was sitting around eating donuts and listening to cassettes with my friend when he told me about this new band out of Copenhagen that sounds like The Slits. I’m always in the market for more Slits-esque post-punk, so he tosses me the s/t tape and I am immediately rolling on the floor dying because the band is called The Double Slits and they are from Copenhagen. My friend (not a scientist) did not get it. That’s all expositional to say, the five piece from Copenhagen seriously knows where their sound fits within the punk schema in addition to knowing their quantum mechanics history and the importance of their home town in the development of such things as atomic bombs and iPhones (listen to their song “iPhones and A-Bombs (Not With a Bang)” for more information).

Recommended for: nerds who like party-cull-rave duality (horrible pun, sorry) and are looking for a new band with a sort of folksy/Slits sound.

[chroniclesofachemist]

confinement of electrons to quantum corrals on a metal surface It both shows the existence of the atoms AND the duality of electrons in one image. That's fantastic. 

[cozydark-blog]

Paths of Photons Are Random -- But Coordinated |

Researchers at the Niels Bohr Institute have demonstrated that photons (light particles) emitted from light sources embedded in a complex and disordered structure are able to mutually coordinate their paths through the medium. This is a consequence of the photons' wave properties, which give rise to the interaction between different possible routes.

The results are published in the scientific journal Physical Review Letters.

The real world is complex and messy. The research field of photonics, which explores and exploits light, is no exception, and in, for example, biological systems the statistical disorder is unavoidable.

Drunken people and photons

"We work with nanophotonic structures in order to control the emission and propagation of photons. We have discovered in the meantime, that inevitable inaccuracies in the structures lead to random scattering. As a consequence, the transport of photons follow a random path -- like a drunken man staggering through the city's labyrinthine streets after an evening in the pub," explains David García, postdoc in Quantum Photonics at the Niels Bohr Institute at the University of Copenhagen.

If we continue with this analogy, then it is not certain that just because one drunken man comes home safely, then a whole crowd of drunken people spreading out from the pub will also find their way through the city's winding streets. There is no relationship between the different random travellers.

But there is when you are talking about photons. They can 'sense' each other and coordinate their travel through a material, according to new research.

"We have inserted a very small light source in a nanophotonic structure, which contains disorder in the form of a random collection of light diffusing holes. The light source is a so-called quantum dot, which is a specially designed nanoscopic light source that can emit photons. The photons are scattered in all directions and are thrown back and forth. But photons are not just light particles, they are also waves, and waves interact with each other. This creates a link between the photons and we can now demonstrate in our experiments that the photons' path through the material is not independent from the other photons," explains David García. continue reading

[cozydark-blog]

Particle and Wave-Like Behavior of Light Measured Simultaneously |

What is light made of: waves or particles? This basic question has fascinated physicists since the early days of science. Quantum mechanics predicts that photons, particles of light, are both particles and waves simultaneously. Reporting in Science, physicists from the University of Bristol give a new demonstration of this wave-particle duality of photons, dubbed the 'one real mystery of quantum mechanics' by Nobel Prize laureate Richard Feynman.

The history of science is marked by an intense debate between the particle and wave theories of light. Isaac Newton was the main advocate of the particle theory, while James Clerk Maxwell and his greatly successful theory of electromagnetism, gave credit to the wave theory. However, things changed dramatically in 1905, when Einstein showed that it was possible to explain the photoelectric effect (which had remained a complete mystery until then) using the idea that light is made of particles: photons. This discovery had a huge impact on physics, as it greatly contributed to the development of quantum mechanics -- the most accurate scientific theory ever developed.

Despite its success, quantum mechanics presents a tremendous challenge to our everyday intuition. Indeed, the theory predicts with a remarkable accuracy the behaviour of small objects such as atoms and photons. However, when taking a closer look at these predictions, we are forced to admit that they are strikingly counter-intuitive. For instance, quantum theory predicts that a particle (for instance a photon) can be in different places at the same time. In fact it can even be in infinitely many places at the same time, exactly as a wave. Hence the notion of wave-particle duality, which is fundamental to all quantum systems. continue reading