Double-Slit-Experiment

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Ok, even though I’ve learned about the double slit experiment before, I still find it really cool!

And yes this video’s a bit corny, but it is so very fascinating!!

(This is the video Hank linked us to in his vlog today)

When Classical Universes Collide, The Result is Quantum Mechanics, Say Physicists

The strange behaviour of the quantum world is direct evidence of the interaction between our universe and many other classical universes, according to a new theory of reality

One of the strangest ideas to emerge from 20th century physics is the many-worlds interpretation of quantum mechanics, which attempts to explain the puzzling, counter-intuitive effects of quantum mechanics.

These puzzling phenomena are things like quantum interference in which a quantum particle passing through a double slit produces an interference pattern, something that can only happen the particle passes through both slits at the same time.

Ref: arxiv.org/abs/1402.6144: Quantum Phenomena Modelled By Interactions Between Many Classical Worlds

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This Will Mindfuck You:

The Double-Slit Experiment

The video above shows scientific proof that there is something NOT quite logical or scientific about this universe. The mere act of observation can completely change the outcome of an event!

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Joe Rogan - What is Reality?

Watched this again this morning… had to repost. Sooo good. 

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Quantum Experiment Shows How “Time” Doesn’t Exist As We Think It Does

The concept of “time” is a weird one, and the world of quantum physics is even weirder. There is no shortage of observed phenomena which defy our understanding of logic, bringing into play thoughts, feelings, emotions – consciousness itself, and a post-materialist view of the universe. This fact is no better illustrated than by the classic double slit experiment, which has been used by physicists (repeatedly) to explore the role of consciousness and its role in shaping/affecting physical reality. (source) The dominant role of a physical material (Newtonian) universe was dropped the second quantum mechanics entered into the equation and shook up the very foundation of science, as it continues to do today.

“I regard consciousness as fundamental. I regard matter as derivative from consciousness. We cannot get behind consciousness. Everything that we talk about, everything that we regard as existing, postulating consciousness.” 

 –  Max Planck, theoretical physicist who originated quantum theory, which won him the Nobel Prize in Physics in 1918

There is another groundbreaking, weird experiment that also has tremendous implications for understanding the nature of our reality, more specifically, the nature of what we call “time.”

It’s known as the “delayed-choice” experiment, or “quantum eraser,” and it can be considered a modified version of the double slit experiment.

To understand the delayed choice experiment, you have to understand the quantum double slit experiment.

 ( see also: animation)

In this experiment, tiny bits of matter (photons, electrons, or any atomic-sized object) are shot towards a screen that has two slits in it. On the other side of the screen, a high tech video camera records where each photon lands. When scientists close one slit, the camera will show us an expected pattern, as seen in the video below. But when both slits are opened, an “interference pattern” emerges – they begin to act like waves. 

This doesn’t mean that atomic objects are observed as a wave (even though it recently has been observed as a wave), they just act that way. It means that each photon individually goes through both slits at the same time and interferes with itself, but it also goes through one slit, and it goes through the other. Furthermore, it goes through neither of them. The single piece of matter becomes a “wave” of potentials, expressing itself in the form of multiple possibilities, and this is why we get the interference pattern.

How can a single piece of matter exist and express itself in multiple states, without any physical properties, until it is “measured” or “observed?” Furthermore, how does it choose which path, out of multiple possibilities, it will take?

Then, when an “observer” decides to measure and look at which slit the piece of matter goes through, the “wave” of potential paths collapses into one single path. The particle goes from becoming, again, a “wave” of potentials into one particle taking a single route. It’s as if the particle knows it’s being watched. The observer has some sort of effect on the behavior of the particle.

(excerpt - click the link for the complete article)

Why Quantize Gravity?

By Sabine Hossenfelder

A good question is one that you know has an answer—if only you could find it. What’s her name again? Where are my keys? How do I quantize gravity? We’ve all been there.

Science is the art of asking questions. Scientists often have questions to which they would like an answer, yet aren’t sure there is one. For instance, why is the mass of the proton 1.67 x 10-27 kilograms? Maybe there is an answer—but then again, maybe the masses of elementary particles are what they are, without deeper explanation. And maybe the four known forces are independent of each other, not aspects of one unified “Theory of Everything.”

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Dr. Quantum explains the Double Slit Experiment.
My PChem professor had our class watch it (it is apparently a department favorite).

The Power of Observation Part 1

There is a lot about our universe that we can’t explain. Science acts as an opposing force to this fact. Science came into existence and continues to thrive because of the human drive to discover and explain everything in our world that may yet elude us. But sometimes, every so often, science stumbles onto a paradox: some things just cannot be measured and explained. The “why” of this statement may seem a bit esoteric, but stay with me: sometimes, purely through measurement and observation, we actually change what we are trying to observe. How can we conclusively determine anything about an ever-changing experimental subject? In this two part article, I will give you a couple of the most interesting examples of this phenomenon. These subjects are not easy to understand, but they are definitely worth stretching your brain over. First up: quantum physics.
 
Note: I have read numerous explanations of the following experiment (too many) and I have found that any understandable explanation (i.e. those not written by scientists, for scientists) have the annoying tendency to do one of two things. One: explain the experiment as if the reader is too dumb to ever grasp the concept unless they are deliberately talked down to. Two, using too many explanation points, question marks and interjections such as huh, what, or can you even believe it?!  to try and convey the quite obvious fact that this subject is interesting and mind-boggling. I will attempt in the following passage to do neither of these things. You’re welcome.

The Double-Slit Experiment

Before we get into the details of this famous quantum experiment, we will need a brief definition of what quantum physics is: the study of the universe at a subatomic level. This includes of course everything that is smaller than atom, which to us is almost inconceivably tiny. Here’s an example from Bill Bryson’s book A Short History of Nearly Everything, of exactly how small of a scale we are talking about: “Atoms are tiny-very tiny indeed…it is a degree of slenderness way beyond the capacity of our imaginations, but you can get some idea of the proportions if you bear in mind that one atom is to the width of a millimeter line as the thickness of a sheet of paper is to the height of the Empire State Building.” This is roughly what a millimeter line looks like: -. Also, we are talking about subatomic particles: object smaller than one ten-millionth of a millimeter. When we get down to such minuscule proportions, we are entering an almost entirely different world than the one that human beings occupy- which may be the very first in a long line of paradoxes that come with the territory: how can objects that we are literally made of occupy a world in which the rules of reality are entirely different? There is no conclusive explanation for this, but we  know one thing for certain: they definitely do.

The double-slit experiment was first conceived of by physicist Thomas Young, who in 1801 used this experiment to show that light acted as a wave. Here is the set-up: a source of light is pointed at a barrier in which there is a single slit that will allow some of the light to pass through and create an impression on the wall behind the barrier. After observing this scenario, a second slit is added to the barrier; there are now two openings for the light to pass through. It is important here to note the difference between a particle and a wave, because the two behave quite differently in this experiment. Particles are objects: things that can be ascribed mass and volume, however tiny the number may be. Waves, on the other hand, are a disturbance that often transfers energy through a substance such as water or air. So, in the single slit scenario, if light consisted of particles, it would look something like a solid band of light where the most particles hit, with some scattered particles to the left and right. However, if light acted as a wave, the band of light that hits the back of the wall looks a bit different:



The light does not just hit the back wall like particles would; the nature of a wave is to radiate outward from its source. Because of this, the band of light on the back wall appears as a straight line in the middle, with dimmer light at each side where it radiates outwards.

The experiment gets a bit more interesting when the second slit is added. In the particle scenario, we get two bands that hit the back wall in a predictable way: as two separate, solid lines:



However when waves are directed at the two slits, this is what shows up on the wall:



Instead of two separate bands of light that radiate outwards, we get multiple, alternating bands of darkness and light. The reason behind this is a property of waves called interference. When two waves meet, they can either cancel each other out or combine to become a stronger wave, depending on where each wave is in its cycle. When light is beamed through each slit, it creates two separate wave patterns that inevitably collide and interfere with each other.This is what creates the alternating bands of light: the dark bands are where the waves have canceled each other out, and the bands of light are where they have combined.



These are the full results of the original Young experiment, but only the beginning of the usefulness of the double-slit scenario. In the 20th century, Albert Einstein proposed the photoelectric effect, which asserted that light can be viewed as particles, which he called photons. The photoelectric effect is real, and photons have been proven to exist. This may seem contradictory, because its seemed that Young had already proved that light was a wave a full century ago. But when it came down to it, there was evidence for both sides; light seemed to act as a wave in some cases, and as particles in others. With the development of much more precise technology, science turned back to the double slit experiment in an attempt to get a firmer grasp on the nature of light.

The 20th Century Double Slit Experiment

This time around, the source of light is much smaller: the experimenters are using a machine so precise that it can literally beam one light particle, or photon, at a time through the slit. The wall in back of the slit barrier is also different: it is a photographic plate that can effectively record the mark that each photon makes on impact. So, they repeat the single slit scenario, one photon at a time, and after a while the familiar single slit pattern starts to emerge on the back wall: a band of light, thick in the middle where more photons have hit it, and thinner on the sides where fewer photons have hit. Since the results for the single slit scenario are very similar for both waves and particles, this scenario doesn’t yield particularly useful information. So next, the double slit is introduced.

In this case, the photons are shot at random at the two slits. Since these are individual photons at work, it takes quite a long time for a pattern to emerge, but eventually, the experimenters are able to discern this pattern:



It is the alternating bands of dark and light that is consistent with the wave. But for all intents and purposes, this pattern makes absolutely no sense. The photons were passing through the slits one at a time: meaning logically, they have nothing to interfere with, and should simply hit the back wall in a straight line like they did with the single slit. Experimenters were baffled. What was causing this seemingly impossible interference pattern?

The next thing they did was set up detectors on each slit. This way, they could record which slit each particle was passing through and hopefully better understand exactly what was going on in the process. The result of this experiment only served to deepen the mystery ten-fold: the interference pattern completely disappeared. They were left with two distinct bands consistent with particle behavior. No matter how many times the experiment was repeated, or what was used to record the particles behavior, the results were the same. When the photons were not measured, they made a wave interference pattern; when they were measured, the interference disappeared. Somehow, the very act of observing the particles changed the way they behaved.

To explain these results, science had to come up with some very new and radical interpretations. The most widely accepted theory was developed by Neils Bohr and is known as the Copenhagen Interpretation. Bohr proposed that what was being fired out of the light source was not really a particle or a wave, but something called a Y wave, or wavefunction. The wavefunction behaves like a wave, radiating outward and causing interference. However, it is not a true wave, but rather a wave of probabilities. The photon is not in any particular place at this stage. It is everywhere, and nowhere, at the same time. It only exists as a probability-until you measure it. In the first round of experiments with no detectors at the slits, the measurement does not take place until the particle hits the photographic plate and is forced to “choose” a position. Consequently, the wavefunction goes through both slits, colliding with itself on the other side and creating an interference pattern of probabilities that makes itself apparent when the particle actually hits the wall. However, when the measurement is taken at the slits, the particle is forced to “choose” earlier, and therefore only goes through one slit. It is no longer a probability, but a particle. It hits the wall with no interference, and therefore, there is no interference pattern.

It is important to note that there are still many unanswered questions here. For example, no one really knows what the wavefunction actually is. Also, what exactly is it about measuring a particle that makes it behave differently? What counts as “measurement” and what does not? Remember, we are dealing with what is essentially an entirely different universe than ours. Things jump in and out of existence, and an object can seem to be in two different places at once. This may all reek of some crackpot theory or science fiction tale, but this is a real phenomenon that is studied by real scientists- it is just that a full understanding of it still lies beyond our grasp, and may never be fully explainable.

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The Double Slit Experiment – consider my mind officially fucked:

((Observation changes how particles respond…wait, so…. Observation changes the properties of matter. Ok, so that means…Observing something changes what it is. Whoa. Yeah, though. Yeah.

Observation… creates reality? … *mindblown*)).

It’s like we have secret superpowers. Things like this fascinate me–things that are unexplainable without excitement, things that force the mind to think complexly, things that suggest that life is more than just a bunch of random encounters between favorable genes. It’s been ages since my curiosity stretched its legs and wandered around so much.

I’d like to think that consciousness is powerful, and that knowing is creating.  What a beautiful thought. (Tell me I’m overreacting–that I’m too serious or too philosophical. I don’t care. That’s just what it’s like.) I think this is cool, and that really shouldn’t be surprising as science’s unexplained mysteries have always appealed to me. What if we really don’t know much about reality at all?

((Remember that bit about curiosity being incurable? Yeah.))

Anyway, happy pondering. ;)

Gravitational Lensing, Refraction & Diffraction: Three Sides to the Same Coin?

Here, we thought we would explain the difference between the terms and how they interact with light (from both a wave and particle point of view): http://www.fromquarkstoquasars.com/gravitational-lensing-refraction-diffraction-three-sides-to-the-same-coin/

Original Image Credit: Unknown (But if you do, please let us know)

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Double Slit Experiment

Recap: When a camera observed the electrons, they acted as particles. However, when the no equipment was used to observe the electrons, they acted as waves and particles simultaneously.

So what’s the reason for this? Does the electron somehow know that it is being watched? That was the only “logical” reason that scientists could come up with so much skepticism and controversy followed.

Want even further proof?

Then in 2002, a group of researchers set up the experiment in a way that the electron could not possibly receive information about the existence of an observing instrument. The setup was on a much smaller scale: a single photon was emitted and an interferometer that observed the wave-or-particle behavior was either inserted or not inserted. (Click here to download the full report)

Here’s the kicker: The insertion of the interferometer took only 40 nanoseconds (ns) while it would take 160 ns  for the information about the configuration to travel from the interferometer to reach the photon before it entered the slits. This means in order for the photon to “know” if it was being watched, that information would have to travel at 4 times the speed of light, which isimpossible (the speed of light is the universal speed limit).

The Results: The photons acted like particles 93% of the time that they were observed. Even if the photon “guessed” the configuration each time, statistically speaking it would never have more than 52% accuracy. In scientific experiments, a 93% success rate is as conclusive as they come.

What are the implications of this?

1. Matter can act as both a wave and a particle depending on whether or not it is being observed (Wave-Duality Theory)

This is the least meaningful implication for you as a macroscopic organism, but nonetheless it’s a pretty crazy concept.

2. Observation can (possibly) affect the outcome of macroscopic events

After all, you and everything you know are composed of these microscopic particles, so why couldn’t something large be influenced as well? It would be the sum of a seemingly infinite amount of pieces of matter acting as either waves or particles. Scientists have very mixed opinions on this topic so I’ll just say it makes sense to me that this could happen on a larger scale.

3. We don’t know very much about this universe (Science is not yet an ‘exact science’)

There are a couple things out there that science still cannot explain like the characteristics of gravity, but this blows Newton’s discovery out of the water. As we study smaller and smaller particles in order to understand more about what we’re made, we seem to find more things that just don’t make sense. Point being that nothing should be ruled out completely because we simply cannot know anything for certain at this point.

What other implications did you get out of these experiments?

Sources:
1. http://www.colorado.edu/physics/2000/schroedinger/two-slit2.html
2. http://arxiv.org/abs/0710.2597
3.http://en.wikipedia.org/wiki/Quantum_mind
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This is also mindblowing. The double slit experiment in quantum physics. You have to watch this.

So, the boy and I were discussing quantum mechanics today (we do that surprisingly often) and this happened. 

If you’re not familiar with the double slit experiment, it goes kind of like this:

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The double slit experiment demonstrates the particle-wave duality of matter. Photons are fired at two slits and the result is an interference pattern. So it looks like light acts as a wave interfering as it passes through the slits resulting in enhanced and cancelled bands on the screen behind (the same thing you would see when you drop two pebbles in a pond). So far your mind is intact.

Now fire individual photons, one at a time. You would expect to see them pass through one or the other slit and hit the screen behind creating two bands. And when it is calculated to see which slit a particular photon has passed through, this is indeed what happens. Now fire photons one at a time without detection, and watch as they hit the screen one at a time and build up an interference pattern! (this experiment has also been done with electrons, and even molecules!). This means that each particle passes through both slits at the same time and interferes with itselfThis is the stuff we are made of. Lol wut? Yeah.

It’s one of the many ways in which physics says fuck you to common sense. 

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The double slit experiment. Why Physics just doesn’t make sense.

Ok, so finally I was able to get my Double slit experiment right. After looking in every fucking store in Mexicali I finally got myself a real laser and I was able to put my experiment in practice. And guess what! 

IT FREAKING WORKED AND I FEEL SO ACCOMPLISHED WITH MYSELF! 

LOOK, I GOT MY LASER.

MY PAPER WITH A DOUBLE SLIT.

AND MY BEAUTIFUL INTERFERENCE PATTERN UwU