The Ultimate Mystery: What is light?
In the 19th century, scientists began to delve into the basic structure of the universe in an attempt to understand how it was put together. In one very simple experiment they sought to determine the nature of light, but the results were unexpected and created a mystery that the greatest minds have been unable to solve to this day.
To a physicist,
light means an energy that is anywhere along the electromagnetic spectrum, from ELF waves to gamma radiation. Visible light is only a narrow part of the spectrum that is most familiar to us because our eyes can detect it. In the Newtonian model of the universe everything is made of particles, including light. Scientists began to think of light as being made from tiny "balls" of energy called
photons.
In 1803 a physician named Thomas Young had been studying sound waves and thought that light was also a phenomenon involving waves. This contradicted the current theory. Young noticed that light could be slowed as it passed through a prism and the observed spectrum of colors seemed to be more easily explained as wave phenomenon rather than that of light "particles".
Young decided he would conduct an experiment that would finally resolve the conflict. What he could not have known is that this experiment would open up a pandora's box of brain-twisting enigmas that contradict our understanding of the universe and our own reality.
As you will see, the result o this experiment is a glimpse into another dimension where time itself can move backwards or stand still. This mystery has been with us for over 200 years now and we are no closer to solving it today. But when and if it is finally understood, civilization will dramatically change and our reality will have to be reconstructed.
The Double Slit Experiment (1803)
Thomas Young tried to keep things simple. He looked for examples in our everyday experience that revealed if things were solid particles of oscillating waves. I will attempt to explain his experiment using more modern analogies so that it will hopefully be easier to understand.
Let's imagine that you have a wide cement wall with an open, rectangular window cut in it. At some distance beyond the cement wall there is second wall. This second wall is made of thin wallboard and has no window. You're going to stand at some distance in front of the first wall and the window. You have a pistol [represented by the triangle
below] and you begin shooting through the window. As you do this, you notice that the bullets are passing through the open window and hitting the second wall where they make holes.
Because you are at some distance from the window (and presumably not a marksman), your bullets vary in their direction with each shot you take. After you have taken hundreds of shots you notice that the pattern of holes in the wallboard resemble the shape of the rectangular window. This is really not surprising and makes perfect sense.
Now we are going to add a second rectangular window a couple of feet to the left of the first window and begin shooting again [see
below]. Because we are at some distance from the two windows, some of our bullets will randomly go through one or the other window. Some may even hit the wall and not go through either window. Some will hit the edge of the window and their trajectory will be slightly altered. But enough pass through either window so that there is a pattern of holes on the wallboard that now resembles two rectangles. Again, this is not surprising and is what we would expect in the world with which we are familiar.
Bullets are solid objects, all the same size and weight and, although their trajectory through one or the other window is somewhat random, we nonetheless can see a distinct pattern on the wallboard.
Next, Young imagined the same two walls immersed in a pool of water. Instead of bullets, let's imagine we have something that generates a wave in the water. Like the example above we will start with only one open window.
As illustrated below, when the wave reaches the open window it passes through it and begins again on the other side, heading for the wallboard [2]. This time we will not have holes from bullets so we will have to find a way to measure the intensity of the wave. I suggest we imagine floating pin-pong balls that can move up and down against the wallboard so we will know when the wave hits the second wall.
With just the one window we have the strongest part of the wave hitting the area in back of the window with less intensity on each side. Again, there is nothing surprising here.
L
ets go ahead and use a wall with two windows, like we did before (see below illustration). The initial wave approached the windows [1], is stopped by the wall but becomes two new waves as it emerges on the other side of the windows [2]. These two waves continue towards the back wall [3], but something interesting happens. Sometimes the peaks of the two waves combine and become a stronger wave. Sometimes the troughs of both waves combine and become a deeper trough. Sometimes a peak and a trough combine and cancel each other and there is no wave. The resulting waves [4], as measured by our ping-pong balls on the wallboard will show a series of bands where the peaks have combines and no wave activity where they have cancelled each other.
Unexpected Results Baffle Scientists, Even Today
What Thomas Young did was establish two distinct patterns that would happen in the two slit (or two windows in our example) experiment. If the energy directed towards the two slits was a solid particle, it would make two distinct (yet a little fuzzy around the edges) patterns. If the energy was in the form of a wave it would form bands, called an "interference pattern" by experimenters since the two waves from the windows interfere with each other.
What happened next freaked him out and it has freak scientists and theoreticians like Albert Einstein, Steven Hawking, Richard Feynman and many others for over 200 years.
The Unexpected Happens
Many of you may have learned about this experiment in your physics class. But there is a new twist that I will tell you about later that will totally blow your mind...
When a single beam of light was directed at the single slit (or window), the light cast a pattern of a fuzzy rectangle -- the same shape as the window. This is a clear example that light is made of individual particles. We call these particles
photons. In physics a photon is an elementary particle (meaning it is not made up of smaller bits and pieces) and it has a unitary size and charge.
So when a single beam of light is directed at a double slit (or two windows) we would expect it to behave much like the bullets in our imaginary experiment and cast two fuzzy rectangles. But it doesn't. Instead we get the interference pattern, indicative of a wave (see
below).
For an interference pattern to happen, we assume that something went through both slits (windows) at the same time. Scientists first thought that two photons are somehow passing through the two windows at the same time, then interfering with each other after they have passed through their respective window and before they strike the back wallboard.
To eliminate this possibility, they managed to fired a single photon at the windows... then another... then another. The wallboard was designed so that the location of each photon could be marked, much like the bullet holes. They were now certain that only one photon was passing through either window at any time. But after a while they noticed the same interference pattern. The places where the photons had hit the backboard were arranged in a pattern of bands and gaps. How could this be happening?
This was so strange that some theorists suggested the photon had somehow split itself in two, gone through separate windows and then recombined. Since it is an elementary particle, this is not possible. So the next idea was to try and see where each photon was going, one at a time, and try to undersand what was happening to it before it hit the wallboard.
The experimenters decided to place some photo-electric cells on the back sides of the windows so that they cold "see" which window the photon went through, then they would monitor where it landed on the backboard. Since light travels in a straight line they would be able to plot the photon's course and see what was causing the interference pattern.
But that just created more problems (see
below).
As soon as a detector was turned on to see the photon pass by, the arrangement of the photons striking the back wall were indicative of a particle. They tried turning one detector on, then the other, then both -- no matter what combination they tried, if they knew which window the photon passed through the experimental results were always indicative of a particle. As soon as they stopped trying to see which window the photon went through, the wave interference pattern appeared.
It appears that whenever we know which window/slit the proton passed through, the result will always be the characteristic pattern of a particle. If we do not know which slit the proton passed through, the result will alwaysbe characteristic of an interference pattern.
Why Observation Changes The Results
To measure the photon passing through the window, the apparatus used a detector that shot its own photons across the gap and collected it on the opposite side. If this beam of photons encountered the experimental photon that had passed through the window, its trajectory would be changed and this change would be noted. But experimenters knew that the experimental photon would also be changed, ever so slightly.
Apparently there is no way to observe the experimental photon passing through the window without altering its path. They soon learned that any time they could detect through which window (or slit) the experimental photon passed, this detection would somehow make the photon behave as if it were a particle.
At one point they reduced the photons in the detector to the point where the detector sometimes would catch the experimental photon and other times it would pass undetected. They noticed when they did this that if the detector could track the experimental photon it landed inside one of the two fuzzy rectangles but for those that escaped detection they would land in one of the interference bands.
Somehow the act of observation was changing the experimental results. But how?
It gets even stranger!
When does the photon change from one form to the other? Does it happen when the particle is being detected? Could the mere act of detection be enough to collapse the wave and form a particle pattern?
To test his hypothesis a man named John A. Wheeler designed an ingenious way of altering the double slit experiment that would, he thought, prove that the process of detection was not responsible for the change from particle to wave patterns.
First, Wheeler had two powerful telescopes -- one focused on each slit. If a photon went through one or the other slit, the telescopes could see it. The telescopes were placed where the fuzzy rectangles would register a photon hit from a particle pattern. Since the light had to travel to the telescopes, they served as a detector.
Wheeler then devised a detection screen that could be very quickly placed in front of the telescopes, preventing them from seeing the slits but recording where the photons landed.
The mechanism was constructed so that the distance between the wall with the slits was quite far from both the removable detection wall and the telescopes.
Becase these distances and speed of light were known, it was possible to know when a photon had been released, passed through either or both of the slits and was somewhere between the slits and the detectors. We call this
time =x in the animation below. At this precise moment the detection screen could either be placed in front of the telescopes or removed.
[See animation
below]
The idea was that the photon should have already decided if it was going to react like a particle or a wave after it had passed through the slits. And this decision by the photon should be irreversable.
Wheeler tried to force the photon to be a particle because, at the time it passed through the slits, it was being watched by the telescopes. By putting up the screen after the photon passed the slits, but before the telescopes received the light, he expected the photon would act like a particle. (Is your head spinning yet?)
In the actual experiment, when the photons passed through the slits, if the detector wall was quickly put in place, they displayed the wave pattern on the wall. But, if after the photons passed through the slits, the detector wall was suddenly removed, the telescopes would capture the photons in the area where two fuzzy rectangles would be -- indicative of a particle.
In other words, the decision on which type of detection is used (screen or telescopes) is being made after the photons have passed through the slits -- presumable after they have already decided to be a wave or a particle. Yet, the later decision seems to somehow influence the photon in the past. Huh?
Ordinarily we have "cause--effect" timelines in nature. But this experiment seems to show that the effect can change the cause.
In other experiments, the detectors were used to determine which slit the photon passed BUT the electronics that reported or recorded the result were turned off. This is the so-called Earasure Paradox because, despite being detected, the interference pattern resulted.
It seems that it is not the detection that matter as much as whether a person (human being) is aware of it or not!
More weirdness: Electrons and Buckyballs
Not surprising, when electrons are used in a vacuum environment instead of photons, the results are identical. But what astonished me was that something as large as a 60 atom molecule -- a so-called "buckyball" -- also displayed this mind-bending feat!
Just how big a molecule needs to be before it continually displays the particle pattern is something that is currently being explored.
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What is a buckyball (C60)?
Buckyballs, also called fullerenes, were one of the first nanoparticles discovered. This discovery happened in 1985 by a trio of researchers working out of Rice University named Richard Smalley, Harry Kroto, and Robert Curl.
Buckyballs are composed of carbon atoms linked to three other carbon atoms by covalent bonds. However, the carbon atoms are connected in the same pattern of hexagons and pentagons you find on a soccer ball, giving a buckyball the spherical structure as shown in the following figure.
The most common buckyball contains 60 carbon atoms and is sometimes called C60.Other sizes of buckyballs range from those containing 20 carbon atoms to those containing more than 100 carbon atoms.
The covalent bonds between carbon atoms make buckyballs very strong, and the carbon atoms readily form covalent bonds with a variety of other atoms. Buckyballs are used in composites to strengthen material. Buckyballs have the interesting electrical property of being very good electron acceptors, which means they accept loose electrons from other materials. This feature is useful, for example, in increasing the efficiency of solar cells in transforming sunlight into electricity.
[Excerpt from Nanotechnology For Dummies (2nd edition), from Wiley Publishing]
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Things To Remember...
While you are trying to get your mind around this, it's perhaps time to answer some frequently asked questions about the wave and particle patterns. Remember that even with the wave pattern, the detector wall in the photon experiments is detecting whole, single photons which are all of uniform size and charge. The detector can only detect these uniform particles -- and they are most certainly particles when they are detected -- however it is the pattern which appears over time that forms the distinct interference bands and gaps or the fuzzy rectangles.
So before they are detected, it would seem, they are influenced by something to land randomly in a pattern of either wave or particle. Once they are detected they are particles. Yet, as we saw in the last experiment -- incidentally called the "delayed choice" version of the Double Slit Experiment -- the decision appears to have been made prior to detection yet dependent upon the subsequent choice of the detection method... whew!
Yes, there's more, if you can handle it. That will be in the next installment on light.
In the meantime, a reader sent me a link to a lecture by Tom Campbell on YouTube. I thought I'd heard almost all of the explanations for the paradox of the Double Split Experiment and Delayed Decision stuff but Campbell surprised me by stating the obvious conclusion that most scientists come to when trying to explain things on the quantum level: it's not real! We are part of a simulation. Reality is either a digital simulation itself, or reality is running on some larger system of things we cannot have knowledge about.
It's cutting edge thinking and it will expand your ideas about reality beyond your imagination. I'll try to get a hold on it and write more. Meanwhile, here is that video. Enjoy.
The Present and The Past: Causality
Perhaps the weirdest things that happen in the quantum world -- the world of very small particles of matter and energy -- is that time often seems to be either meaningless, or it travels in the opposite direction. There are several excellent examples of this, like Schrodinger's Cat (which I will discuss later) but this is one that I think best illustrates the reverse time phenomenon.
The Punch Card Problem
A team of scientist design the Double Split Experiment using singe photons which are eventually collected on a detector screen. Aside each slit there is a detector which can determine which slit the photon went through. The detectors are connected to a computer that makes note of the trial number (0001 to 1000) and the slit (left or right) and immediately creates an old IBM punch card with this information encoded on it. The data is then erased from the computer memory.
When the photon eventually hits the back detector screen, the x,y coordinates are picked up and sent to the computer, along with the trial number, and a different IBM punch card is printed with this information encoded on it. The data is then erased from the computer.
So far, no human has seen the cards or monitored the computer. When 1000 trials are completed the two stacks of 1000 IBM punch cards are locked away for 50 years.
Remember: the photon will always have a wave pattern unless the slit that it went through is known by a conscious mind. Even if detectors are used, if the information is not observed by a conscious mind then it remains in wave form.
After decades the box is opened. The stack of cards containing the trial numbers and the slit that detected the photon are shuffled in the dark, then half of the cards are removed randomly and burned.
When the cards are sorted, those of the same trial numbers are put in one pile and those who do not have a corresponding trial number (because their mate was burned) are in the remaining pile.
We know from the Double Slit Experiment that a particle will create two fuzzy rectangles while a wave form will create several fizzy bands. We can determine the x,y coordinates of these rectangles by letting photons enter through one, then the other slit (one slit at a time). When the IBM punch cards are examined for the x,y coordinates it is possible to say that the coordinates are either within the rectangle (a particle pattern) or fall outside of it (a wave pattern).
We also know from the Double Slit Experiment that if a human mind (consciousness) is aware of which slit the photon went through then the resulting pattern will be that of a particle.
Quantum mechanics therefore predicts that the cards with matching trial numbers will all fall within the two fuzzy rectangles of a particle pattern, since we have now consciously detected which slit the photon passed through. Because the cards that were destroyed no longer contained the information on which slit the photon passed through, the result is that we never observed this information and so the expected pattern will be that of a wave.
What has happened here is that a random decision (which cards to burn) made in the present has caused a photon 50 years in the past to decide to be in the form of a wave or a particle.
Or, from the perspective of the photon, it has seen what will happen in 50 years in the future and has decided to take the form of a wave or a particle. This is the weirdness of the quantum world of light.
I've gone to sleep many mights trying to imagine a way to use this reverse-time phenomenon... if there was a way to send lotto numbers back in time. After all I only need one day of reverse-time communication -- not 50 years. But the logic does not yet allow for such things. Or does it?
In the above example, two events (the slit information and observation 50 years in the future) are entangled. In the famous experiment below, the decay of an atom is entangled with a cat.
Schrodinger's Cat -- Observation By An Animal?
In the standard model of how stuff is made, commonly called the Copenhagen Interpretation, an atom like uranium would be considered as both having decayed and not decayed -- two superimposed states -- until it was actually observed by someone. This is analogous to a photon being both a wave and a particle until observed.
While this dual-state mathematical condition exists in the quantum world, it makes no sense in the larger world where we exist. Schrodinger's Cat is a thought experiment, sometimes described as a paradox, devised by Austrian physicist Erwin Schrodinger in 1935 to illustrate how absurd the quantum world can be.
We begin with an atom that is capable of radiation, like uranium. Uranium atoms have so many electrons that the ones in their outer shell, furthest from the pull of the nucleus, tend to escape and fly off in space. A geiger-counter is designed to detect this escaping electron and produce a "click".
While we know about how many "clicks" we will detect with a good size chunk of uranium, we have no idea when a single atom of uranium will shed an electron. It could be the next second or many years from now. But we are confident that, eventually, this will happen.
In Schrodinger's thought experiment a single atom of uranium is placed in a glass jar with a geiger counter. Instead of just making a "click" when it detects the flying electron, the geiger counter also breaks open a tablet of cyanide gas... Oh, yes. We're going to put this whole contraption inside a metal box that also contains a live cat, close it and wait.
After some time has passed we might wonder if the uranium decayed and ultimately killed the cat, or perhaps that has not happened yet and the cat is doing fine. Schrodinger was trying to show that, according to the rules set by the Copenhagen Interpretation, until you open up the box and look, the cat can exist in two states: dead and alive. His argument was that the cat's fate would not be "real" until an observer looked at it, which is of course quite absurd.
In our rational world, the cat is either dead or alive, not both. Of course, the cat knowns if it is dead or alive -- doesn't that count as an observation? It's crazy, but such things exist in the quantum world.
Here's a brief video that explains the paradox.
The Unexpected Happens... Again!
Get ready for another light paradox. This is an experiment you can do yourself. It involves polarizing filters of the type used in sunglasses and on camera lenses to reduce glare.
The polaroid filter is made of long molecules that are arranged in parallel in a specific direction. The filter takes advantage of the fact that a traveling light wave will have an undulating wave that extends perpendicular to the direction of travel. This wave travels at a specific angle of rotation. Actually, light travels in tiny discrete packets of energy and each packet has its own unique rotation angle. Collectively, like in a beam of light, it all seems random.
The parallel cells in the polarizing membrane allow light that is similarly aligned to pass through but blocks all the other rotation angles. So after light passes through a filter it is said to be polarized in a specific direction.
Here is a short video that will explain this better than I can:
So here is the paradox. In the illustration below you can see three different observations being made with three different arrangements of polarizing filters.
I
n the top row you see that a filter has been arranged to allow a vertical rotation angle. The light that passes through is visible and has a vertical orientation. [a]
The second row shows the same light passing through the first filter but being stopped by the second one because it is allowing only horizontal rotation of light to pass. There is no light visible to the observer. [b]
In the bottom row you see what happens when a filter is placed at a 45° angle between the vertical and horizontal filters. [c] Surprisingly, light now passes through all three filters.
If you can explain this, please get ready to collect your prize in Physics. Many have tried. But it remains an enigma.
But there IS a solution!
There is a modern physicist named Dr. Sylvester James Gates who is known for being the top string-theory (M-theory) theoretician. His world is usually immersed in math formulas but he enjoys relating his ideas to ordinary people in venues like the 2011 Issac Asimov discussions [
below]. Dr. Gates is an speaker and used the occasion to announce a new and shocking discovery.
Gates claims that while he was solving a basic equation in the sub-quantum world of the tiniest bits that make up stuff (because they are so tiny -- smaller than quarks -- they aren't even stuff yet...) he came across a basic formula that, when solved with numbers, yielded a long stretch of 1s and 0s.
These were not random 1s and 0s. Gates immediately recognized this unique pattern as being a computer code discovered by Claude Shannon in the 1940s and used to transfer digital signals without errors.
Claude Shannon was the person who decided to send analog voice transmissions by digital means (1s and 0s) for AT&T. This successfully eliminated the noise that plagued telephones in their early days. Shannon eventually really got into digital communication and defined the limits of digital data transmission with formulas that are basic to digital communication today.
CDs, DVD, your cellphone and hard drive -- anything that sends digital information from one point to another sends it in packets. Even voice signals and skype are made up of thousands of packets a second passing through wires or space -- each has it's own "envelope" if you will -- a beginning and an end -- and something the sending device adds to it as it sends it out. This extra piece of data is something that the receiving end of the communication checks after it receives the digital package. It's a thing call an "error check code".
In its basic form, the error check code gives the count or number of bytes in the package it just sent. If the count of all the 1s and 0s is wrong, it means something got lost along the way and the receiver usually sends a message back to the sender that says "we didn't get it all, please send it again!" And a new packet is re-sent.
More advanced systems, ones that just send out the digital data and never hear back from the receiver, do something even more remarkable.
Claude Shannon devised a small addition to the packet of data that contained samples of the data in the packet. This way, if a small piece of digital information was lost, the packet from the previous successfully sent data would be used to fill in the missing data. It's all complex and you would have to be Einstein to even begin to understand it... but this whole process was reduced to a specific series of 1s and 0s that give the instruction to make the repair. This is exactly what S.J.Gates found embedded in the basic formula of string theory!
Gates stated what he found and it was confirmed. He has made no further disclosures about how it got there, if he has a clue. In one interview he apologized for being the person to suggest that the movie, The Matrix, was more true than fiction.
Is our reality a digital simulation?
Don't laugh or smirk at this idea. It has been entertained by some of the greatest minds who know the quantum world intimately. The idea that our reality is made up of discrete bits is a fact. You may be surprised to learn that there is a smallest unit of time and smallest unit of space. It's as if reality is made of pixels, which have a refresh rate (the constant velocity of light) and the ability to preserve rendering until it is observed by someone -- the avatar in the game.
Dr. Brian Whitworth has been the most outspoken theorists to "flesh out" this theory. If you have understood any of these light paradox examples in this article, you should be able to understand a little of this important paper. I've included it here so you can read it at your leisure.
Whitworth makes a compelling case for the Matrix! Things like Young's Double-Split paradox and the Delayed Choice phenomenon have a chance of making sense in a simulated world but the simulated world theories pose a threat to things like religion, "God" and free-will. It is perhaps these paradigms (including the
Terror of Death that we anesthetize with religious beliefs) that keep the simulation theories at bey.
The Similarity of Quantum and Simulated worlds
A simulated (digital computer) environment will have a maximum velocity determined by the pixel density and refresh rate of the screen. In the quantum world this frame of time is the time required for the smallest unit (Planck length) to change its position with the smallest bit of energy. Like a video game, continuous time is made up of very small moments that only appear to be continuous.
In a computer game, the velocity will appear uniform in all reference frames and can be computed by dividing the pixel size by the refresh rate. In the quantum world, the same applies:
Planck length / Planck time = velocity of light
(1.616 X10-35)meters / (5.39 X10-44)seconds = C
In video games, objects are only rendered when they are being looked at (observation). The photon exhibits this phenomenon by being a probability wave until observed by a conscious mind.
In a video game, time slows when massive programming is required. Quantum time also slows in the presence of mass.
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The Single Avatar Solution
One interesting simulation theory postulates that the "game" involves only one avatar at a time, to conserve processing. The same consciousness inhabits all of the characters in the universe, sometimes being a homeless man in New York, another time being Vladimir Putin... or YOU... and so on. You are reading this article right now because it was your turn to be who you are right now. There is only one reality for each run of the game.
This would limit the need to code everything in the universe, from every possible perspective and time. And the lifetime of an avatar could be just a small moment of time in some other reality -- where the program is running. The number of avatars is finite, so it is possible.
In the quantum world one learns that if something is possible then it is.
In this simulation example, everything that is behind you and your field of observation is not rendered -- is not "real" yet, until you turn and observe it. This explains why a photon will be a wave probability -- essentially programming variables -- until it is observed and the wave is said to "collapse" and produce a discrete particle.
If you are not familiar with computer games these days, ask your children to show you the state of the art. You will understand that this is not a fantasy.
When I described this to my good friend in Australia, John McGovern, he replied with the following youtube video which appears to say it all:
"Do unto others as you would have done to you," seems to take on new significance in this simulated world. So do things like reincarnation and karma... "We are all one!"
Notes:
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New Scientist: Quantum wonders: Corpuscles and buckyballs, 2010
Nature: Wave-particle duality of C60 molecules, 14 October 1999. Abstract