[Quantumcat (OP)]

A Home Test for Parallel Universes
by Sam Sachdev
March, 2004

When you think of a parallel universe, do you think of a universe, or a world, similar to ours but different in some fundamental quality. Bill Clinton, for instance, is a happily celibate priest. Or George W. Bush delights his fellow Mensa members, at parties, with his verbal games. Or, perhaps, you only have a science-fiction quality vagueness to what you think of a parallel universe: pointed ears, warp-drive through worm holes, and form fitting Lycra body suits on a thin, well-groomed crew. A parallel universe, it may surprise you to learn, is actually detectable in your own home, office, or almost anywhere indoors. All that’s required is a red laser pointer, a pin, and a piece of paper.

With the aid of David Deutsch, a physicist at Oxford University and his excellent book “The Fabric of Reality”, the experiment, in a step-by-step process, is going to be set-up and, then, it’s going to be explained why this magic-like result from this experiment is indeed proof of a parallel universe.

First, a red laser pointer is needed. I found one at Radio Shack for $19, not including the triple A batteries that were needed. The red color of the laser pointer is important. The red light, unlike the white light of a flashlight, which is a composite of many colors, doesn’t fray as white light does. The red light, specifically, of the laser pointer casts more specific shadows – which is what this experiment does. A flashlight, according to Deutsch, can probably be substituted. A filter, however, is going to have to be placed over the white beam. The filter, can only be red colored glass; paper or any other filter won’t work.

Next, a relatively large, dark room is needed. The room should be large enough to set up the laser pointer on, say, a table, and have it cast its light on a wall about one and a half meters, or about five feet away for my metrically challenged Americans. At first, this humble journalist tried to do the experiment, during the bright light of a Washington, DC winter day, in a walk-in closet and a bathroom. Both weren’t large enough. My dining room, when the sun had set, was.

David Deutsch recommends a room that’s almost totally dark. I found, however, that this was too dark. The experiment requires enough light to manipulate the laser pointer. What I did was have a light on in another room, which provided enough light to see what I was doing but dark enough to see the shadow cast by the laser pointer.

The experiment is best done with done with two people, with one handling the laser pointer and the other observing the pattern on the wall. The positions can then be switched. Be careful, however, not to shine the laser light into the other’s eyes.

If you don’t have two people, this is what I recommend. Fold a piece of paper in half and place it on the table, so that one half is perpendicular to the table. Then, using a book, or anything to set the laser pointer on, aim the pointer at the paper. Mark where the red light hits the paper. Using a pin (and only a pin, not a tack, the holes have to be as small as possible) punch two holes, on the mark, as close to each other as you can. Then, aiming the laser pointer at the two small holes, a shadow of five slits should be cast on the wall. That is, there’s going to be one large red dot cast on the wall. In the dot, there should be five distinct shadows cast by the two holes. If this doesn’t work, the most common problem I found was that there wasn’t enough distance between the paper and the wall. If possible, increase the distance. David Deutsch recommends about five meters, or fifteen feet, but I found about five feet, or a meter and a half, was enough to observe the pattern.

Why, you may be wondering, are there five slits of shadows when there are only two holes? That's because light, as you may have guessed, usually travels in straight lines. We can’t, for instance, see around corners or buildings. When light, however, is forced to go through a small hole, it acts like a thirteen year old forced to go clothes shopping with their parents, it rebels. Specifically, it bends. The smaller the hole is, the more it bends. So, if light traveled in straight lines, there would only be two shadows cast by the holes. Instead, however, the shadow of the five slits, from the two holes, is a result of concentric rings of varying thickness and brightness. There is a bright spot in the center, surrounded by a dark ring and, following this pattern, fainter rings of light and darkness around it. The result is the pattern of the five slits.

Patiently, you’ve read this far and want to know when you’re going to detect a parallel universe. This is the next step.

Next to the two holes you’ve punched, make two more. It’s important that they be parallel with the other holes and that they be as close to the other two. Also, keep in mind that the width of the point of the laser is narrow (at least mine was) and that the laser has to go through all four holes simultaneously.

What should happen, or is expected to happen, is that the same pattern as with the two holes appears. Light beams, according to “Fabric of Reality”, normally pass through each other unaffected. So, the same pattern as the two holes, should be repeated, only brighter and slightly blurred.

What happens is nothing like that and is, David Deutsch believes, evidence of parallel universes. Only three shadows are cast. That is, two of the shadows disappear. If you look closely, you’ll see that where there been two red shadows are now dark. So, punching two more holes actually results in two of the shadows going dark.

How does this happen? Something, obviously, is blocking the light from casting the shadow. Or, you might think that the photons, individual units of light, have somehow been bent and recombined to form a pattern of new shadows. The answer, as will be explained, can’t be this but is an usually undetectable world of photons, or, a parallel universe.

First, however, it should be explained that what interferes with the laser light has the properties of light. If, for instance, two of the holes are covered by anything opaque, the five slit shadow reappears, but it, the red laser light, can penetrate anything and behaves as light does, that allows light to pass. If, for instance, a system of mirrors is set-up, which the light bounces off of and eventually reaches the wall, the same patterns appear.

What happens when the red laser light is slowed to one photon at a time (no, this can’t be done in your dining room)? That is, when only one photon is fired through each of the four slits, the same pattern appears. Could it be that, when the photon passes through the slits, they change course and recombine? Nope. When detectors are placed at each of the four slits, and one photon again is passed through them, only one of the detectors goes off, meaning that the photon hasn’t split.

David Deutsch, using an experimentally confirmed prediction from quantum theory, believes that what’s causing the interference are shadow photons. More specifically, interference, as in this experiment, is not only common for photons but for every particle. So, Deutsch writes in “Fabric of Reality”, this is what is causing the interference, “[W]hen a photon passes through one of four slits, some shadow photons pass through the other three slits.” The shadow photons, then, are blocking the tangible photons, causing only three shadow slits.

These shadow photons form a parallel universe. David Deutsch writes that they behave as tangible particles do. They obey the law of physics but with the difference that they’re in a different position.

But how, exactly, do the shadow photons stop the tangible ones? The answer that Deutsch presents is that the shadow atoms, present in the shadow photons, form a barrier. Only a small proportion of the tangible and shadow atoms, however, are interacting with one another. Or, as Deutsch writes, “each shadow atom in the barrier can be interacting with only a small proportion of the other shadow atoms in its vicinity, and the ones it does interact with form a barrier much like a tangible one. And so on. All matter, and all physical processes, have this structure.” To clarify his last point, the parallel universe interacts with the tangible universe in much the same way as particles so in the tangible universe: only a small proportion do. The result is through interference, or weakly, as in the experiment.

Why, you may be wondering, if there’s a detectable parallel universes around us, why don’t we detect, or notice it, more often? David Deutsch writes, the answer, “...can be found in the quantum-mechanical laws that govern them.” Every particle, for instance, has counterparts in other universes and is only interfered with only by those counterparts. Any other universe, therefore, can only be detected when the particle in, say, our universe converges with its counterpart in another universe. The path of the particle and its counterpart have to be exactly right. They have to separate and join together again, as in this experiment, and the timing has to be right. If there’s a delay in the particles or any interference, the particles won’t converge. Also, a parallel universe is only detectable between universes that are very alike. In short, because these events are extremely rare, so is the detection of parallel universes is difficult.

It should be added that most physicists disagree with Deutsch’s conclusion that what is detected in this experiment is another universe. For brevity’s sake, the argument against can be summarized as, there is something interfering with the light in this experiment, why does it have to be a parallel universe? Why can’t it be just be left to something that we don’t yet understand?

If you’re interested in how Deutsch answers his critics, I recommend the “Fabric of Reality” for his answers and reasoning.



Am I dead? Am I alive? I'm both!

[tweener]

I don't know whether to laugh or be appalled.  I don't know where to start. ... At the beginning I guess.

This is an interesting experiment, and one that is standard for any physics class.  Only I've never heard the "parallel universes" explanation given by any physics teacher.

"The red color of the laser pointer is important. The red light, unlike the white light of a flashlight, which is a composite of many colors, doesn’t fray as white light does. The red light, specifically, of the laser pointer casts more specific shadows – which is what this experiment does. A flashlight, according to Deutsch, can probably be substituted. A filter, however, is going to have to be placed over the white beam. The filter, can only be red colored glass; paper or any other filter won’t work."

Any color will work.  This experiment is not about "casting shadows", it's about making "interference patterns".  This is easier to see with a single color light, though white light with no filter will work just fine.  Laser is best because the light is coherent and the interference patters are really bright. So, a red laser pointer is good.

I'll accept the part about a large darkened room - a closet won't be big enough.

"Using a pin ... punch two holes, ... as close to each other as you can. ... a shadow of five slits should be cast on the wall. That is, there’s going to be one large red dot cast on the wall. In the dot, there should be five distinct shadows cast by the two holes."

Actually, depending on the strength of the light source, the distance from the paper to the wall, and the size of the holes, you may see more than five or less than five.  The center is the strongest and the bright areas get progressively weaker away from the center. According to a known and well-accepted formula I might add.  This is called interference and it is a well known property of any type of wave.

"Next to the two holes you’ve punched, make two more. It’s important that they be parallel with the other holes and that they be as close to the other two. Also, keep in mind that the width of the point of the laser is narrow (at least mine was) and that the laser has to go through all four holes simultaneously. "

OK.

"What should happen, or is expected to happen, is that the same pattern as with the two holes appears. Light beams, according to “Fabric of Reality”, normally pass through each other unaffected. So, the same pattern as the two holes, should be repeated, only brighter and slightly blurred."

I don't know who expects this, but I doubt they've ever had a real physics class - or at least didn't stay awake through this part.  Light beams do indeed travel through each other "unaffected", however, this is not the situation that is set up.  The light passing through the four holes will make a different interference pattern than what passed through two holes.  I certainly would not expect four holes to make the same pattern as two holes.

"What happens is nothing like that and is, David Deutsch believes, evidence of parallel universes. Only three shadows are cast. That is, two of the shadows disappear. If you look closely, you’ll see that where there been two red shadows are now dark. So, punching two more holes actually results in two of the shadows going dark. "

I have not done this experiment, but I accept that you will get three "shadows" (actually called minima) in the pattern.  Once again, you might see a more or less elaborate pattern depending on the strength of the light etc.  

"How does this happen? Something, obviously, is blocking the light from casting the shadow. Or, you might think that the photons, individual units of light, have somehow been bent and recombined to form a pattern of new shadows. The answer, as will be explained, can’t be this but is an usually undetectable world of photons, or, a parallel universe."

The "something" that is blocking the light is the light itself interfering in such a way that the waves cancel each other.  The bending (aka refraction) is the same.  The can be this, and has been for well over a hundred years!  

"What happens when the red laser light is slowed to one photon at a time (no, this can’t be done in your dining room)? That is, when only one photon is fired through each of the four slits, the same pattern appears. Could it be that, when the photon passes through the slits, they change course and recombine? Nope. When detectors are placed at each of the four slits, and one photon again is passed through them, only one of the detectors goes off, meaning that the photon hasn’t split. "

This is a very common experiment that has been performed for years.  It is a result of the particle nature of light and is "explained" by quantum mechanics.  

"David Deutsch, using an experimentally confirmed prediction from quantum theory, believes that what’s causing the interference are shadow photons. More specifically, interference, as in this experiment, is not only common for photons but for every particle. So, Deutsch writes in “Fabric of Reality”, this is what is causing the interference, “[W]hen a photon passes through one of four slits, some shadow photons pass through the other three slits.” The shadow photons, then, are blocking the tangible photons, causing only three shadow slits.

These shadow photons form a parallel universe. David Deutsch writes that they behave as tangible particles do. They obey the law of physics but with the difference that they’re in a different position."

I'm not going to touch this one, other than to say that he is free to believe whatever he wants to.  Though it might be simpler just to say that God is swatting some of the photons, thinking they are flies.

"But how, exactly, do the shadow photons stop the tangible ones? The answer that Deutsch presents is that the shadow atoms, present in the shadow photons, form a barrier. Only a small proportion of the tangible and shadow atoms, however, are interacting with one another. Or, as Deutsch writes, “each shadow atom in the barrier can be interacting with only a small proportion of the other shadow atoms in its vicinity, and the ones it does interact with form a barrier much like a tangible one. And so on. All matter, and all physical processes, have this structure.” To clarify his last point, the parallel universe interacts with the tangible universe in much the same way as particles so in the tangible universe: only a small proportion do. The result is through interference, or weakly, as in the experiment."

Shadow atoms?  Present in "Shadow photons"??? Gimme a break!  I've never heard of atoms present in photons.  But, hey this is another universe, so the rules are whatever they need to be, right?

"It should be added that most physicists disagree with Deutsch’s conclusion that what is detected in this experiment is another universe. For brevity’s sake, the argument against can be summarized as, there is something interfering with the light in this experiment, why does it have to be a parallel universe? Why can’t it be just be left to something that we don’t yet understand? "
I'm not surprised that "most physicists disagree" with this.  I'm not a physicist and I disagree.

"If you’re interested in how Deutsch answers his critics, I recommend the “Fabric of Reality” for his answers and reasoning. "

I don't think I want to spend any money on this book.  I would be interested to see what sort of "qualifications this guy has - just to avoid others with similar "training".

I know....I know... I'm being very harsh and very negative here. I just hate to see some rambling like this passed off in the name of "real science".  If someone wants to write science fiction, great.  I love reading science fiction, and I love reading science.  I love it when fiction includes science, but I get annoyed when science starts including fiction.

Hey! that last sentence is a pretty good quote.  Maybe I'll make that my signature.


----
John - The Eternal Pessimist.

[OldMan]

I must have been reading the same page as you yesterday Erin, you just beat me to posting it here.

John I right with you on this and agree it is absolute trollop. When I was reading parts of it I thought it wasn't going into a whole lot of details as to why this was happening and sounded to me like saying "So that is why my finger doesn't reattach when I pass a knife through it!"

-----------------------------
I'm attacking the illusion but the stopping drives me mad!

[Ultima]

WTF??? I did that experiment in A-Level physics? I didn't think that I was viewing parallel universes then; did this guy have any sort of scientific training???

LOL search for "shadow matter" in Google and you get all sorts of tripe coming out about psi and magic...


wOw the world spins?

[Quantumcat (OP)]

Actually, my father emailled it to me. I knew before that this was meant to prove quantum things but never heard before that it proved parallel universes. I thought you guys would be interested, if there was anyone who hadn't heard of the slit experiment before.

Am I dead? Am I alive? I'm both!

[tweener]

I guess I kinda went over the top on my response, but to tae a basic experiment like than and jump off into parallel unverses??  That's just too much.

But, who knows.... Quantum mechanics does not explain anything, just predicts the statistics - maybe quantum effects are due to interactions from other parallel universes.  

Did I just say that???  I need help!


----
John - The Eternal Pessimist.

[gsmollin]

Well, it was a very well written post. A lot of work. I'm not surprised a journalist wrote it. Good job.

The interpretation of quantum-mechanical phenomena is not agreed-upon by scientists. These same scientists can all do the math, work the theory, and perform the experiments, including this classic wave-particle duality experiment. The hitch comes in what we say "caused" this to happen. It's kind of scary how different those same scientists will react to each other when they try to talk sense about what it all means.

I'm not going to expound on my own interpretation, which is not in agreement with the parallel universe, simply because I can't prove it's any closer to the truth than the parallel universe explanation. But I will say that going all the way back to Einstein, Bohr, and Heisenberg, nobody can agree on what quantum mechanics means. One thing is clear- we won't solve it here.

[neilep]

After reading the above I made a phone call to one of my other selves in one of the parallel universes (cos he's a physicist and I'm not) and he agrees that its a load of dogs doo dahs !![]

Why oh why am I allowed on this site ?..I'm sooo full of bullsh*it !![)]


'Men are the same as women...just inside out !'  

[gsmollin]

I'm surprised that everybody here didn't just yawn at this. The "many universes" theory is invoked commonly by physicists. Many others think like most of all of you that it is animal scat. I'm also surprised that more people haven't jumped on this and turned it into a flame war. Ho hum, I suppose it's all to esoteric.

Just for the record, however, this experiment "proves" wave-particle duality, and nothing about other universes.

[qpan]

I would have yawned at this, except for the fact i did this experiment in A-Level physics. Its called Young's slits and the red bands are called fringes. This effect has been well known for quite some time now, so either the journalist completely misinterpreted the physicist or the physicist missed a couple of lectures during A-Level physics.

see http://www.northallertoncoll.org.uk/physics/Module%204/Young's%20Slits/Young's%20slits.htm

quote:What happens when the red laser light is slowed to one photon at a time (no, this can’t be done in your dining room)? That is, when only one photon is fired through each of the four slits, the same pattern appears. Could it be that, when the photon passes through the slits, they change course and recombine? Nope. When detectors are placed at each of the four slits, and one photon again is passed through them, only one of the detectors goes off, meaning that the photon hasn’t split.

What? If he is really a physicist he should know that the photon would travel through every single possible path (a quantum superposition of paths) before reaching its destination. If you measure the damn thing, the system crystallises out of the superposition. Measuring proves nothing in quantum mechanics - thats the whole basis of quantum mechanics. Due to the single photon travelling through every single path, it interferes with itself, causing it to deflect. Where the photon finally lands is completely due to probability, with the highest probabilities being the bright areas.

Its also a bit of a big leap to invent shadow photons and shadow doo dahs when its simply a case of constructive or deconstructive interference of electromagnetic waves. Is he also going to invent shadow sounds to explain constructive and deconstructive interference of sound waves?

"I have great faith in fools; self-confidence my friends call it."
-Edgar Allan Poe

[gsmollin]

Hia, qpan. Yes, yes, you are right. But lets examine, in a nutshell how one leaps from photons to universes. Label the slits A and B. The photon goes through slit A or B. But QM tells us the photon also has a superposed state aA + bB, where a and b are numbers. This state has properties of its own, which prove its existence. One of those properties is the interference patterns it causes, which proves wave-particle duality.

Now for the leaps. The photon goes through the slits. States A, B, aA+bB are generated. If I measure the position of the photon, the superposed state resolves into A or B with some probability of having gone through A or B. Before I measure it, however, the superposition remains. I will soon measure it, and see A or B, but before I do, I am not in either a state of having measuring A or B, but am in a superposition of measuring A, B, or aA+bB. If that is true, then is there not also another earth, another galaxy, another universe? This school of thought is called "conventional quantum cosmology". It resolves the superposition problem by positing multiple universes to cover the superposition of states that QM requires. This approach has a real following in the cosmology community, and some of those followers are quite convinced they will prove it is true.

Ordinary QM does not answer the universe question. The photon and double slits are in one part, and the observer and all his equipment is separate. Cosmology does not have that luxury, since it involves the whole universe, and the observer cannot be outside the universe. So physicists are trying to construct a theory of QM that extends to universal proportions. It isn't easy, and there are other approaches to this besides the multiple universes method.

I belong to a different camp, that believes that the quantum world does not extend to macrosocopic proportions. There is a range of mass, space, and time, over which it extends, and after that, the superposed state resolves.