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The Home Parallel Universe Test

CowboyNeal posted more than 10 years ago | from the it-is-indeed-a-test-for-something dept.

It's funny.  Laugh. 754

Sam Sachdev writes "David Deutsch, a physcicist at Oxford, has designed a home test for parallel universes. Using a pin, a red laser pointer, a piece of paper, and a relatively dark room, he claims that the results from this experiment confirm the existence of parallel universes." Okay, so it may not really be proof of parallel universes, but it's a fun trick to try with a laser pointer nonetheless.

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FP (-1, Funny)

Anonymous Coward | more than 10 years ago | (#9148598)


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FP

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Jeez (3, Funny)

Anonymous Coward | more than 10 years ago | (#9148602)

...about one and a half meters, or about five feet away for my metrically challenged Americans. At first, this humble journalist...

Man, what an ass. Sounds to me like a pompous buffon [schuminweb.com] .

Hey! (-1, Offtopic)

Anonymous Coward | more than 10 years ago | (#9148605)

Second post!

Re:Hey! (-1, Offtopic)

Anonymous Coward | more than 10 years ago | (#9148689)

Oh Man, mods don't have any sense of humor! No wonder they are not going to get any hot girls!

I'm pretty sure I've seen this before (5, Funny)

Ghostx13 (255828) | more than 10 years ago | (#9148607)

Oh yea, it was that one episode of McGyver.

Re:I'm pretty sure I've seen this before (-1, Offtopic)

Anonymous Coward | more than 10 years ago | (#9148635)

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Since I can't see air it must be another universe! (1)

RobPiano (471698) | more than 10 years ago | (#9148608)

I'll say it for you, 'laser pointers are cool!'

Anyways, there are plenty of ideas that come to mind that don't help this guys hypothesis. Phase, filtering, and the plethora of other particles in the room come to mind.

Re:Since I can't see air it must be another univer (5, Informative)

CyberDruid (201684) | more than 10 years ago | (#9148676)

You have understood nothing. The phenomenon is real and one of the strangest and most spooky things in physics. It shows that it it possible to get a particle (in this case a photon) to interfere with itself.

The only question is how you interpret it. The first interpretation, created by Einstein, Bohr and other dignitaries of the time, was the "Copenhagen Interpretation" which requires an "observer".

The "Many-worlds interpretation", first thought of in the late fifties gets rid of the need for a mystical observer by introducing parallell universes, where entangled particles can still interfere with each other.

This interpretation is championed by many of the leading physicists. For example Deutsch and Murray Gell-Mann.

I believe Feynman has a strange third interpretation involving particles travelling backwards in time, that cancel out the waves of forward travelling particles at specific points in space-time.

Re:Since I can't see air it must be another univer (4, Funny)

citog (206365) | more than 10 years ago | (#9148773)

You have understood nothing. The phenomenon is real and one of the strangest and most spooky things in physics. It shows that it it possible to get a particle (in this case a photon) to interfere with itself.

and so, out of guilt and self-loathing, it hides itself from the observer?

Isn't this just the double-slit experiment? (5, Insightful)

bravehamster (44836) | more than 10 years ago | (#9148610)

Isn't this the same old double-slit experiment, just slightly modified? Perhaps this is new to some people, but anyone who's had the slightest interest in quantum mechanics or parallel universes should have heard of this by now.

Re:Isn't this just the double-slit experiment? (2, Funny)

irokitt (663593) | more than 10 years ago | (#9148658)

Are you kidding, that was the best nap I had that whole semester!

Re:Isn't this just the double-slit experiment? (5, Interesting)

nukey56 (455639) | more than 10 years ago | (#9148668)

I'll save everyone the bother of having to trudge through this whole depressing article:
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?
In other words, they're using the term "parallel universe" to get people to read this. They found a neat effect with photons, yes. Might as well just call it a Terroristic Particle Exploitation, and then maybe the real media will examine it at that point. Nothing to see here, move along.

Re:Isn't this just the double-slit experiment? (5, Informative)

MacroRex (548024) | more than 10 years ago | (#9148669)

Yeah, here [uoregon.edu] is a nice summary with pictures.

I'm not a quantum physicist, but I think I have a idea what this is about; the light waves just interfere differently with four slits. Since this Deutsch guy draws wildly different conclusions about the result, I guess he's either much stupider or much smarter than me. And since he's the university physicist and not me, I feel bad for him if it's the former.

Re:Isn't this just the double-slit experiment? (5, Interesting)

norton_I (64015) | more than 10 years ago | (#9148792)

David Deutsch is a really bright guy, but he has a problem understanding how other people think, including lots of other really smart physicists.

He believes the many-worlds interpretation of quantum mechanics adamantly, and thinks that any other interpretation is, if not outright wrong, not a useful frame of mind to understand QM.

I am also a many-worlds person, as are many other physicsts I know, but I also know many very smart quantum physicicst who are not, and I am not willing to say they are wrong (yet).

I think a historical analogy might be appropriate: Back in the day. there was substantial scientific contention over whether the sun revolved around the earth or vice versa (I am not considering the religious contention -- for a while the scientific evidence was not sufficiently clear). You see, you could reproduce all the observable motion of the planets in the geo-centric model using finer and finer epicycles. So, planets would revolve the earth, and had wobbles in their orbits that faithfully represented their entire movement patterns. Or, you could adopt a helio-centric model, in which all the retrograde motion and other strange behavior cleanly fell out of the equations. You could do the math either way, but in retrospect, the helio-centric model is a much better "interpretation" of the data than the geo-centric model, because it is useful for figuring out all sorts of other things, like gravity and conservation of momentum.

Deutcsh feels similarly about the many-worlds interpretation. But as I said, among quantum physicsts you will find the whole range of people with different levels of commitment to different theories. or interpretations.

Re:Isn't this just the double-slit experiment? (-1, Redundant)

Anonymous Coward | more than 10 years ago | (#9148795)

Don't worry, he's definitely smarter than you.

Re:Isn't this just the double-slit experiment? (1)

Hittite Creosote (535397) | more than 10 years ago | (#9148813)

the light waves just interfere differently with four slits

Why? Can they count? They get confused if presented with more than two options? 'They just do' isn't much of an explanation.

And don't bother feeling bad about Deutsch, he's definitely smart.

Re:Isn't this just the double-slit experiment? (4, Informative)

DrLudicrous (607375) | more than 10 years ago | (#9148679)

And by old, bravehamster means OLD. Like over 200 years old. See this link [wolfram.com] for more details on Young's double slit experiment.

Basically, light behaves as a wave, and since waves can constructively and destructively interfere with one another (cast two stones simultaneously in a pond and oberve the resulting interference pattern) light will form a funny looking pattern that one would not intuitively expect on a screen some distance from the slit.

Fabric of Reality?? (5, Insightful)

acxr is wasted (653126) | more than 10 years ago | (#9148611)

I thought the double slit experiment was intended to show that light behaved as both a particle and a wave.

Re:Fabric of Reality?? (3, Interesting)

jfern (115937) | more than 10 years ago | (#9148642)

My favorite was the one where you have a light source, and some filters that only let through light polariized in a certain direction.

A horizontally and a vertically polarized filter block out all light.

But put a 45 degree diagonally polarized filter in between, and suddenly 1/8th of your original light source is going through.

Re:Fabric of Reality?? (4, Informative)

DrLudicrous (607375) | more than 10 years ago | (#9148739)

This is because what is reaching the last filter in the second case does not have the same polarization that it had in the first case.

After passing through the first filter the light has been polarized in some direction- all of the perpendicular components have been removed by the filter.

In the first case, there is only one other filter, oriented at 90 to the first one. This will only allow the components of light polarized 90 to the first screen's orientation to pass. But all of those components were removed, so nothing gets thru. In the second case, your filter is not oriented at 90, but at 45 to the first filter. Hence it will only components of light at 45 to the first filter's orientation to pass. But using vector analysis, we can break that orientation up into two vector components (that match up with the orientations of the first and third screens), and see that some light will get thru. How much? Well, cosine of 45 is 1/sqrt[2], and the intensity of the transmitted light goes as the square of that, so 1/2 of the light coming from the first filter gets through the 2nd filter.

Also, 1/2 of the original light went thru the first filter- this assumes a random distribution of polarizations of incoming light, i.e. unpolarized light.

Since the third filter is oriented at 45 to the second, we get another factor of 1/2. Totaling up all 3, we get 1/8 of the original intensity. I hope this makes sense. It probably won't unless you are comfortable with vectors.

Re:Fabric of Reality?? (2, Interesting)

skifreak87 (532830) | more than 10 years ago | (#9148652)

It does show that. But when light is slowed down so only one photon shoots out at a time, this photon cannot interfere with itself, the same pattern occurs. Something else must cause it, hence "multiple universes" theory.

Re:Fabric of Reality?? (5, Informative)

Anonymous Coward | more than 10 years ago | (#9148683)

I hate to break it to you, but that's not a valid interpretation; a single photon can and does interfere with itself. Where you think of a particle, QM sees that a "photon" is a localized wave packet, represented by a probability wave that has useful values in a small volume (because it still looks like a particle) but exists everywhere. This probability wave can and does go through the different holes, and what you get out is effectively an interference of the photon with itself. This is the basic idea behind Feynman's "sum of all histories" (properly, the path integral formulation of QM) approach, that looks at all possible paths - in this case, all the holes.

Re:Fabric of Reality?? (1)

DrLudicrous (607375) | more than 10 years ago | (#9148700)

Mod this up. I was going to say something to the same effect, but I was afraid to use the phrase "wave packet". This is an excellent description of how the overwhelming majority of physicists view this phenomenon.

Re:Fabric of Reality?? (5, Informative)

tehdaemon (753808) | more than 10 years ago | (#9148776)

In english, The photon is not a point, only when it hits something does it act like a point, as it only hits one point. A photon is a weird fuzzy thing that is mostly here, and partly here and over there, but a little bit everywhere else. It interferes with itself because it squeezed through both holes, and because it squished itself through both holes, it's shape (places where it mostly and partly was) changed, and so there are some places that it is more likely to hit, and some places that it can't hit.

Re:Fabric of Reality?? (1)

txviking (768200) | more than 10 years ago | (#9148685)

Does the hesienberg principle is true as well for shadow protons ? I would think it does. So what can we do with them ? What is the difference of shadow protons and anti-matter?

Re:Fabric of Reality?? (1)

DrLudicrous (607375) | more than 10 years ago | (#9148756)

Anti-matter exists. It can be detected and observed. "Shadow protons" has nothing to do with the article- it was photons, not protons, and those two things cannot possibly be more different. Shadow photons have a much better name- virtual photons, and they are already used in theory. And they are just that- a theoretical convenience. They don't really "exist" in the sense that other matter (or anti-matter, no real difference there) does. In short, this paper doesn't really seem to say anything new, though apparently the author thinks it does.

Re:Fabric of Reality?? (4, Informative)

Ckwop (707653) | more than 10 years ago | (#9148704)

It depends on your Interpretation of the underlying quantum mechanics.

The normal double slit experiment doesn't actually tell you very much. It's when you do the double slit experiment with *single* photons that the truth becomes spooky.

The reason being that even with single photons you get the same pattern on the wall. The question is did the photon interfere with itself or was there a 'ghost' photon that went through the second hole that interfered with our photon but this ghost exists in a Parallel universe?

Well, if you read the Feynman lectures in physics he does a good thought experiment to clear this up a bit. Imagine we have a second single photon beam. The idea is that we measure the photon going through the slits to see which slit it actually goes through. At first the frequency is too high and it destroys the interference pattern.

As we turn the frequency down the pattern begins to reappear but at the precise moment that the pattern does reappear we are unable to view which slit the photon went through. The frequency of the light is too low to clearly resolve the slits and hense which slit the particle went through - they've blurred into one slit.

So the question of which intepretation is correct is more a point of philosophy. We can't decide which one is correct because quantum mechanics wont let us take a measurement.

Simon.

Re:Fabric of Reality?? (1)

geekychic (732496) | more than 10 years ago | (#9148805)

That pesky Heisenberg shows up in the most unwelcome places ;)

So, I'm wondering:
In short, because these events are extremely rare, so is the detection of parallel universes is difficult.

In my understading of the multiverse theory, there are infinitely many parallel universes. This article seems to be talking about probability, which in the face of an infinite number of chances, is moot. It's guaranteed to happen. Obviously, this isn't the case. Someone want to clear this up for me?

too bad (0)

Anonymous Coward | more than 10 years ago | (#9148616)

I read all that (yes I'm new here) and it didnt explain where those 2 other shadows went. Anyone care to explain ?

perpendicular (5, Funny)

theguywhosaid (751709) | more than 10 years ago | (#9148617)

i tried it and the laser turned 90 degress midair

does that mean i have a perpendicular universe?

And in other news... (5, Funny)

nukey56 (455639) | more than 10 years ago | (#9148618)

Detection of tachyons now possible via the usage of duck tape, scissors, a wooden spoon, and a very unhappy hamster.

Re:And in other news... (3, Funny)

Anonymous Coward | more than 10 years ago | (#9148636)

That's nothing. All I need is the duct tape.

Macgyver~

Re:And in other news... (1)

DrLudicrous (607375) | more than 10 years ago | (#9148780)

Man, you ever try to keep up with a tachyon? I swear those things go at least 10,000,000 miles a minute- must be the drugs. They are like "Speed" on crack.

Mirror before it is too late (-1, Redundant)

Anonymous Coward | more than 10 years ago | (#9148619)

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 protons, then, are blocking the tangible protons, causing only three shadow slits.

These shadow protons 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 protons stop the tangible ones? The answer that Deutsch presents is that the shadow atoms, present in the shadow protons, 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.

Re:Mirror before it is too late (0)

Anonymous Coward | more than 10 years ago | (#9148819)

I do not, I repeat, I do NOT understand why this guy is getting funding at all to do this sort of research. My goodness, I'm in control theory and it is nearly impossible to get funding despite its immediate engineering applications! There is something seriously wrong with the world. I'm in a badass parallel universe.

fuck3r (-1, Offtopic)

Anonymous Coward | more than 10 years ago | (#9148620)

ARE LOOKING VERY people's faces is bring yo0r own Appeared...saying fun to be again. BSD managed to make own agenda - give

Where are the pictures? (2, Funny)

foniksonik (573572) | more than 10 years ago | (#9148622)

Dude, I really want to see this parallel universe... doesn't he even have pictures?

Re:Where are the pictures? (2, Funny)

hovercraftSpareWheel (731518) | more than 10 years ago | (#9148799)

They're in the other universe of course.

Re:Where are the pictures? (0)

Anonymous Coward | more than 10 years ago | (#9148818)

Well, in this experiment the relevant parallel universe looks otherwise exactly like the one you are in (well, you are in both of them, but bear with me...) and the only difference is the exact path taken by a single photon.

Polarized Lenses (1, Interesting)

Anonymous Coward | more than 10 years ago | (#9148626)

I did something similar for an 8th grade science fair where I had 3 polarized lenses set in 3 different slots in a tube. When one lense is turned to a angle of another lense no light comes through the tube. However, if you then put a third lense in between the two other lenses and turn it light will come through the tube again. It was supposed to show how light has properties of both particles and waves. Beyond that it became Buckaroo Bonzai quantum physics stuff.

Re:Polarized Lenses (1)

skifreak87 (532830) | more than 10 years ago | (#9148697)

This has to do w/ the fact that measuring something in quantum physics changes it. For instance, suppose light has two components for polarization (x and y). If you put a normal lens upright and only let in pure y light, you end up collapsing all the light into it's y portion. The middle lens, collapses this light into it's 45 degree portion and the last takes only the x portion. Without the middle lens you're left taking the x portion of stuff w/ only a y portion (nothing gets through).

Slightly more technical explanation, polarization (and other quantumish properties - I forget if polarization is technically a quantum property) is measured in terms of two basis vectors. When measuring (or filtering in this case), you collapse the wave form (or vector) into the component that's allowed through. By switching basis vectors multiple times, you essentially transform the wave several times. (1x +1y gets filtered into 1y which gets re-written as (1 + 1 ) which when filtered is transformed into 1 which is equivalent to (1x + 1y). assuming the original light was equally polarized between x and y it would get through all three just fine. different polarization combinations yield different results but approx 1/8th of natural light (randomly polarized) will get through the three filters. without the middle filter, you have light in only the y component being collapsed into it's x component (0) and thus no light is seen

Re:Polarized Lenses (1)

jfern (115937) | more than 10 years ago | (#9148728)

Polarization is a 2 dimensional quantum state, just like the spin of an electron or a "qubit" used in a quantum computer.

What you're essentially doing is doing is performing 3 quantum measurements on this state, which each give you one of two results:
the photon passes the filter
or it doesn't.

The thing is these 3 measurements don't commute, which means that once you do a measurement, you're no longer in the state you thought you were for the previous measurements.

Re:Polarized Lenses (0)

Anonymous Coward | more than 10 years ago | (#9148785)

This has to do w/ the fact that measuring something in quantum physics changes it.

Will everybody please stop quoting standard quantum mechanics to explain the behaviour of light.

If you put a normal lens upright and only let in pure y light, you end up collapsing all the light into it's y portion.

The light gets absorbed, this has nothing to do with a quantum mechanical collapse. Please, try to be a bit more informed before you post about physics

Out of phase? (1)

Thinkit4 (745166) | more than 10 years ago | (#9148627)

Couldn't it just be out of phase like those noise-cancelling headphones?

Article Text and freecache.org link (1, Informative)

Anonymous Coward | more than 10 years ago | (#9148628)

http://freecache.org/http://www.allsci.com/paralle l.html

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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 protons, then, are blocking the tangible protons, causing only three shadow slits.

These shadow protons 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 protons stop the tangible ones? The answer that Deutsch presents is that the shadow atoms, present in the shadow protons, 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.

Parallel? (3, Funny)

physicsphairy (720718) | more than 10 years ago | (#9148630)

Why not perpendicular, or skew? I think that differently oriented manifolds are being discriminated against!

Wavicles are fun (2, Insightful)

Probable (515784) | more than 10 years ago | (#9148637)

IANAP, but doesn't this simply demonstrate wave interference? as in:

http://www.cavendishscience.org/phys/tyoung/tyou ng .htm

Re:Wavicles are fun (5, Insightful)

oglueck (235089) | more than 10 years ago | (#9148677)

Absolutely.

He is talking about the classical double slit experiment. The results of that experiment are correctly predicted by quantum physics because you need to treat photons as waves and not as particles here.

The author however wants to explain the results treating the photons as particles only. I must admit I have no idea why this leads him to the parallel universe theory.

In my opinion that theory is not needed here as we already have an excellent model (the quantum physics) that predicts those results extremely exactly. We must not forget that quantum theory (and its application in particle physics) is the most accurate theory / model in the world. No other theory other than quantum theory matches as exactly with the experimental results (up to 10 to the power of -9)!

Re:Wavicles are fun (0)

Anonymous Coward | more than 10 years ago | (#9148798)

"We must not forget that quantum theory (and its application in particle physics) is the most accurate theory / model in the world. No other theory other than quantum theory matches as exactly with the experimental results (up to 10 to the power of -9)!"

Really? you were able to solve relativistic problems with the quantum theory AND obtain that level of precision.

Re:Wavicles are fun (2, Interesting)

steveha (103154) | more than 10 years ago | (#9148809)

We must not forget that quantum theory (and its application in particle physics) is the most accurate theory / model in the world.

True.

However, we don't understand how it works. Quantum theory is a bunch of constants and equations, and it all works but we don't understand why. The "many-worlds interpretation" of quantum mechanics suggests that parallel universes have something to do with how quantum mechanics works.

P.S. We also don't understand why quantum mechanics rules apply at very small scales, but very different rules apply at larger scales. (A photon can seem to go through two slits at once, but you won't get a baseball to do that trick, or even a really tiny speck of dust.)

steveha

Re:Wavicles are fun (1, Informative)

Anonymous Coward | more than 10 years ago | (#9148821)

In my opinion that theory is not needed here as we already have an excellent model (the quantum physics)

The many worlds idea is not a new theory, it is a way to explain the laws of quantum mechanics. Some people have problems accepting the idea that things are not what they are until they are measured, which is the idea of the Copenhagen interpretation.

So it's not a matter of wrong predictions, it's people being uncomfortable with the fundamental aspects of the theory.

No other theory other than quantum theory matches as exactly with the experimental results (up to 10 to the power of -9)!

I think might want to add a couple of zero's. I think the most accurate spectroscopic today is on the 1s-2s transition of hydrogen. These currently have an accuracy of a couple of Hz (look for T.W. Hansch on google). Given the fact that the 1s-2s transition sits at a frequency of 2466 THz, you can do the math on the accuracy. All this experimental work has not yielded any errors in quantum mechanics.

Parallel Universes (1)

Anonymous Coward | more than 10 years ago | (#9148638)

Is the point not that such universes exist
"next to each other" with no connection what so ever. If you live inside a parallel universe you can't detect other universes outside.

Shadow Photons? (0)

Anonymous Coward | more than 10 years ago | (#9148639)

Sounds like the Dark Sucker Theory [galactic-guide.com] ...

What's the photon/proton thing about (5, Insightful)

Amiga Lover (708890) | more than 10 years ago | (#9148640)

I'm no physicist, but the article talks about photons and their properties, then mid sentence and afterwards begins referring to them as protons and THEIR properties, then goes on with a description of some photon/proton hybrid logic

Is this a joke article?

Re:What's the photon/proton thing about (1)

ceswiedler (165311) | more than 10 years ago | (#9148653)

I'm wondering if it's a spell-checker thing. Like someone hit 'Change all' with the wrong value selected.

Has anyone else noticed that misspellings in books are almost nonexistent nowadays except when the misspelling is another (correctly spelled) word? It's pretty funny to read sometimes.

Re:What's the photon/proton thing about (1)

PsiPsiStar (95676) | more than 10 years ago | (#9148733)

I had one book full of misspellings and grammatical errors. Ironically it was about common grammatical mistakes made by Chinese students learning English. Some of the examples they used were even incorrect. The guys writing it obviously didn't have English as their first language.

Re:What's the photon/proton thing about (1, Informative)

Anonymous Coward | more than 10 years ago | (#9148696)

No, if you're careful, you see that he starts talking about protons. Protons - and neutrons and electrons and all particles - have wave properties just like photons. Given the proper setup, you can conduct this same experiment with protons, and that's what he's talking about.

Re:What's the photon/proton thing about (1)

That_Guy_Again (713150) | more than 10 years ago | (#9148825)

It's funny. Laugh.

FUCK CANADA (-1, Troll)

Anonymous Coward | more than 10 years ago | (#9148641)

Fucking pussies! Go eat some back bacon and poutine, and drink beer that is really no stronger than ours! [stormpages.com]

Idiots (3, Informative)

Lord Kano (13027) | more than 10 years ago | (#9148655)

Hawking describes this type of thing in A Brief History of Time. This is NOT proof of a paralell universe, it's proof that light travels as a wave as well as a particle.

LK

Re:Idiots (0)

Anonymous Coward | more than 10 years ago | (#9148674)

You are very arrogant. I'm sure Deutch is very intelligent. To call him an idiot because you disagree with his hypothesis about quantumn mechanics makes you sound like an ass wipe.

Re:Idiots (1)

Lord Kano (13027) | more than 10 years ago | (#9148791)

You are very arrogant.

You'll get no argument from me on that point.

I'm sure Deutch is very intelligent.

I know that Stephen Hawking is very intelligent.

To call him an idiot because you disagree with his hypothesis about quantumn mechanics makes you sound like an ass wipe.

I'll side with Hawking over someone who is presenting parlor tricks as "proof" of his theory.

LK

Re:Idiots (4, Funny)

Concerned Onlooker (473481) | more than 10 years ago | (#9148707)

This is NOT proof of a paralell universe, it's proof that light travels as a wave as well as a particle.

Well, whatever. All I know is that when I tried it my cat died....

Re:Idiots (5, Funny)

AvantLegion (595806) | more than 10 years ago | (#9148787)

Well, whatever. All I know is that when I tried it my cat died....

Are you sure?

Crap article, just plain optic diffraction! (4, Informative)

Kjellander (163404) | more than 10 years ago | (#9148657)

This kind of pseudoscientific articles are one of the worst things on the internet!

This is a classic optics experiment to show that light has wave properties, and it has NOTHING to do with parallell universes. It is all explained here:

diffraction [wikipedia.org]

And if you want to show any quantum mechanical effects you need to make sure that only one photon leaves the laser at any given moment, and that is not happening here.

Re:Crap article, just plain optic diffraction! (4, Informative)

BZ (40346) | more than 10 years ago | (#9148738)

The point (briefly and ineptly mentioned in the article) is that if you _do_ have only one photon leaving at a time (such experiments have in fact been performed) you get the same diffraction pattern.

So a single photon somehow passes through all four slits at once and interferes with itself.

Unless you try to detect which slit it's going through -- then the pattern disappears.

Now all this can be explained in terms of wave functions, state superposition, and wave function collapse when a measurement occurs. But the point is, that "wave function collapse when a measurement occurs" and "parallel universe with shadow photons" are about equally bizarre phenomena. And assuming they give the same predictions for results of experiments, neither is more "correct" than the other.

Of course this article doesn't cover the question of whether the two theories give the same predictions... which is where the pseudo-scientific part comes in.

Did you read the last line of the article? (0)

Anonymous Coward | more than 10 years ago | (#9148777)

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

That should pretty much sum up the legitimacy of the article.

Test to confirm the existence of laser pointers (4, Funny)

Anonymous Coward | more than 10 years ago | (#9148659)

Sam Sachdev [mailto] writes "David Deutsch, a physcicist at Oxford, has designed a home test for red laser pointers. Using a pin, a parallel universe, a piece of paper, and a relatively dark room, he claims that the results from this experiment confirm the existence of laser pointers." Okay, so it may not really be proof of laser pointers, but it's a fun trick to try with a parallel universe nonetheless.

Summary (2, Insightful)

Anonymous Coward | more than 10 years ago | (#9148661)

Old experiment, old result, new conclusion. Bad science. Poor writing.

Old conclusion. (1)

rufusdufus (450462) | more than 10 years ago | (#9148753)

This is a version of the Many worlds [deoxy.org] interpretation of quantum mechanics first expressed Hugh Everett in 1957.

The article is very flawed, but don't let that reflect on David Deutsch who is very smart unlike the article.

Parallel universe or just light waves? (1)

LinuxEvangelist (215022) | more than 10 years ago | (#9148664)

This experiment sounds very much like an experiment used to show that light not only acts like a particle but also as a wave. I have not performed this experiment myself but it sounds as if the patterns produced on the wall are produced by the light being bent as it passes through the slits and displaying a wave pattern. Much like the way water would behave if a wave passed through a narrow opening into a broader area - it would spread out. Perhaps what is happening in this experiment is simply two of the waves cancelling each other out completely. That would explain why two of the patterns disappear.

But of course, I'm not a physicist nor have I ever studied particle theory or quantum mechanics. So maybe I'm off-base.

There is no alternet universe (5, Funny)

Felinoid (16872) | more than 10 years ago | (#9148688)

When I tried this experement I ended up with a 3D holographic image of the words "There is no alternet universe"
and a few moments later someone whispered
"If you try that again we'll eat your soul"

So there is no alternet universe...
Ok mister spooky voice you can stop making my walls bleed. And could you remove the chains from the door? I will NOT be entering that hole in the wall ok?

Re:There is no alternet universe (2, Funny)

wadiwood (601205) | more than 10 years ago | (#9148822)

And in this non-existent alternate universe, they can't spell either (or did you make a copying error?)

Or is the "Alternet" a parallel universe Internet?

Not impressed (0, Offtopic)

Bill_Royle (639563) | more than 10 years ago | (#9148691)

If this test was done by an overclocker, you wouldn't have any stinkin' batteries - you'd have a flux capacitor powering it.

These guys are amateurs.

mod article down (0)

Anonymous Coward | more than 10 years ago | (#9148694)

had a couple mod points but it wouldn't let me mod the article down... :(

Anyone read the book? (1)

Black Parrot (19622) | more than 10 years ago | (#9148695)


In the article, "shadow photons" become "shadow protons" between one sentence and the next. Perhaps that's advanced physics, but I suspect the writer got something confused. Can anyone straighten it out?

Why this is suspicious: (4, Insightful)

LoneIguana (681297) | more than 10 years ago | (#9148698)

Why this is suspicious: It seems a little strange that only _one_ source is cited throughout the article, david deutsch. False information by third paragraph: 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. Yes, a laser is needed, but not because it is red, in fact any color laser should work, red is just the cheapest. The reason for a laser is that it provides coherent light, that is all the light that is emited is in phase. This is necsessary for the interference. Sachdev tries to explain the interference soley in terms of particles, when in fact the light is behaving as a wave. He is entirely neglecting the wave-particle dualty, and resorts to parrallel universes to explain it in terms of particles.

And if you peek through the little holes... (2, Funny)

Black Parrot (19622) | more than 10 years ago | (#9148701)


...you can see ladies taking their clothes off.

Re:And if you peek through the little holes... (1)

TWooster (696270) | more than 10 years ago | (#9148760)

That, or the pretty red light of your retinas being burned to bits.

Have fun!

Shadow Protons? (1)

Chrispy1000000 the 2 (624021) | more than 10 years ago | (#9148710)

Shadow Protons?
\\snort\\
As, from what I know, protons are mearly balls/waveforms of energy, which activate receptors in our eyes, showing us the light, so to speak. So if a so called shadow proton hit one of these receptors, what would we see? Darkness? Gotta love this home-brew science.

Re:Shadow Protons? (2, Insightful)

bprime (734645) | more than 10 years ago | (#9148748)

Actually, protons are subatomic particles usually found in the nuclei of atoms. Maybe you mean photons?

proof? (1)

gunix (547717) | more than 10 years ago | (#9148711)

Dear CowboyNeal, I strongly object to your writing "Okay, so it may not really be proof of parallel universes,.."

You make it sound like there is a chance that there will be a proof sometime for something in physics. Per definition, it can never be a proof for anything in phyciscs. There can only be modells and experiments that contradicts the modell or that "confirms" the modell.

Incompetent drivel (5, Interesting)

physicsphairy (720718) | more than 10 years ago | (#9148712)

First off, the author can't keep straight the difference between a photon (a boson) and a proton (fermion).

Second of all, he credits David Deutsch with an idea that most certainly is not his. Both the notion of wave functions (what this article is talking about) and the idea that this somehow relates to parallel universes are older than I am.

This is not a revolutionary idea, and it is not really a controversial one either, as the author of the article seems to indicate. This is just one explanation of a curious quantum mechanical effect. There are other explanations, and they all describe what happens quite accurately. They may each have their own proponents, but really none of them is wrong--they are just different interpretations.

I generally do not like griping, but this write up is positively abysmal. It is no offense to David Deutsch--I am sure he is a quite competent individual. But I do not think the author of this paper actually read his book. It sounds too much like the BS I would string together from reading the first few chapters and the epilogue when I had a book assignment in schoool.

Go here [higgo.com] for a decent, intuitive, layman's introduction to various quantum mechanical oddities.

Re:Incompetent drivel (1)

DrLudicrous (607375) | more than 10 years ago | (#9148796)

Here Here! Glad to see the physicists bitching about this thing. Heh, I didn't notice the photon/proton mixup, but that explains why the slashdotters keep mentioning shadow protons. Sigh. Just last week someone asked me if the world is all subjective because of physics- she was thinking of relativity. The state of science education in this country is abysmal.

The moral of the story is... (2, Insightful)

Asmotheque (553149) | more than 10 years ago | (#9148717)

Junk science is everywhere. This, though, is the first time I've ever seen something along the lines of string theory's extra dimensions being "proven" by interference of waves.

Is there any way to mod down the fool who wrote the article?

Re:The moral of the story is... (1)

DrLudicrous (607375) | more than 10 years ago | (#9148769)

Where did you get string theory out of that article? It never mentioned it at all. And interference patterns don't need string theory to be explained. String theory is more useful to explain things like what the universe was like close to the Big Bang, why gravity is weak, why the universe is expanding at an accelerating rate, yada yada.

You bastards! (4, Funny)

Merovign (557032) | more than 10 years ago | (#9148722)

I tried this, and everything changed! I'm fat! My beautiful wife is gone! My beautiful aircar is gone! All of my stuff is crammed into this stupid apartment!

I can't even find a link to the nearest spaceport on Google!

How do I get back home?!?!?!?!?!

I RTFA and it SUCKs (3, Insightful)

PingXao (153057) | more than 10 years ago | (#9148734)

What a bunch of unintelligible nonsense. I'm sure David Deutsch would explain this differently. Whatever he told the author of the article has been lost somewhere. Probably in the vacuous head of the author. He doesn't mention how light behaves as particles AND waves at the same time. He talks about "shadows" going dark. In fact, when I was done reading the article I wasn't sure what he meant by his use of the word "shadow" at all. The writer did a terrible job of explaining what's going on in this experiment and what it's supposed to represent.

Time, I guess, to DTFE.

Re:I RTFA and it SUCKs (2, Insightful)

DrLudicrous (607375) | more than 10 years ago | (#9148804)

I think by shadow particle he meant what physicists call a virtual particle. But the 'article' still sucks donkey balls.

Problem. (3, Funny)

PsiPsiStar (95676) | more than 10 years ago | (#9148746)

My parallel self tried it and said that it didn't work.

It works! (5, Funny)

Yeechang Lee (3429) | more than 10 years ago | (#9148750)

I tried the experiment myself, and Dr. Deutsch is right! Through the holes, I saw images from many parallel universes, worlds in which Columbus discovered Europe, Lincoln shot President Booth, and Germany and Japan saved the world from Nazi America and Fascist Britain in WWII. (However, Michael Jackson is a disfigured weirdo pervert in every parallel world. Must be a fundamental physical law, like the speed of light.)

QM and single photons (4, Informative)

steveha (103154) | more than 10 years ago | (#9148761)

This demonstrates that light can act like a wave, and have a diffraction pattern.

The "parallel universe" part comes in to explain why it still works if you fire single photons, but since you can't fire single photons (or easily check the results if you could), this isn't really a "home test" of any use.

The fact that single photons can make a diffraction pattern, seemingly interfering with themselves, is a truly weird feature of quantum mechanics (but then, I repeat myself -- quantum mechanics is always truly weird!). And one of the explanations proposed is that light in parallel universes is somehow causing the interference with the single photons in this universe.

Another explanation is that light sometimes acts as a particle, and sometimes as a wave, and when you detect a single photon coming through a slit, you are forcing that photon to act like a particle, and it will not throw a diffraction pattern; but if there is no measurement to decide which slit the photon passed through, the light can act as a wave instead of a particle, and can have an interference pattern.

http://www.starlight-pub.com/UnitNatureofMatter/Pa rtIII/III2QuantumEnergy.html [starlight-pub.com]

This page lists various explanations of why the single-photon two-slit experiment behaves as it does. One of the explanations is the parallel-universes one.

http://members.aol.com/jmtsgibbs/TwoSlit.htm [aol.com]

Here's just the part with the "Many-Worlds Interpretation":

There are two sets of universes, each containing a version of our photon, one set in which the photon passes through the left slit and one set in which it passes through the right. (Actually there are an even greater number of universes in which the experiment is never carried out in the first place, but we are ignoring those.) The photons are particles that carry a property called "quantum phase" which oscillates as they travel. Two universes which are identical except for the photon arriving at a certain point on the film with opposite phases, cancel each other out. Neither one is "real". Maybe it is more correct to say that the multiverse cannot contain two such contradictory universes in the first place, rather than to imagine them existing, and then meeting and going "poof".


steveha

Interesting way to test for the MWI (5, Funny)

physicsphairy (720718) | more than 10 years ago | (#9148764)

In the Many Worlds Interpretation of quantum mechanics, each possibility is represented is represented by a branching universe. So if you flip a coin, there is a universe in which it goes heads, and one in which it goes tales. (that is oversimplifying a bit--there would in fact be infinitely many of each)

Well, how do you know if you live in such a "multiverse"? The answer was proposed by Max Tegmark just a few years back:
Take a gun, put it to your head, and pull the trigger. Repeat several times. If the multiverse model is correct, then your "self" will continue to exist only in those universes where the gun does not fire. So if you try and pull it a bunch of times and nothing happens, you must be one of the many parallel yous who happens to live in a universe where, in spite of probability, the gun did not fire.

Of course, I would not recommend trying it. If the MWI is correct, well, then in another universe you already have tried.

I have a feeling there are at least four of them. (0)

Anonymous Coward | more than 10 years ago | (#9148766)

I think that if you take to the time, and scroll down to about the 15 paragraph you can find an excellent description of what's taking place. Essentially we've all been educated wrong, and http://www.timecube.com/ can be the best way to start all over again.

There is nothing new here (2, Insightful)

Jason1729 (561790) | more than 10 years ago | (#9148778)

This is a very old experiment, and a well-known phenomenon. It was even one of the answers on slashdot's poll for favourite physics experiment (and my personal favourite).

Even the idea that it is proof of parallel universes is not original. Michael Crichton made that claim in his book Timeline. It's an excellent book (despite the horrible movie loosely based on it), but it is fiction.

Jason
ProfQuotes [profquotes.com]

Looking For These Parallel Universes... (0, Troll)

pandrijeczko (588093) | more than 10 years ago | (#9148782)

Assuming that a parallel universe exists for every conbination of every event that has occurred within our own universe, then if anybody manages to find these parallel universes and a way to get across to them, then please give me a call:

1. The universe here Bill Gates' computer science tutor at university said "That's a crap piece of code, Bill. I'm putting you in the law degree class."

2. The universe where Jon Bon Jovi hijacked Stevie Ray Vaughan's plane and got killed instead.

3. The universe where Darl McBride wasn't dropped on his head as an infant.

4. The universe where whenever you post something off-topic to Slashdot you get disconnected and...

[CLICK]

this is sooo lame (-1, Offtopic)

Anonymous Coward | more than 10 years ago | (#9148801)

slashdot is going down the drain

Two people.....in a dark room? (1)

MrIrwin (761231) | more than 10 years ago | (#9148807)

Hey honey, come back to my place and we can make paralell universes together.

The Author's Background (2, Insightful)

DrLudicrous (607375) | more than 10 years ago | (#9148811)

"Sam Sachdev, a graduate of the University of Iowa, is also a freelance science journalist. In addition, for between three and four hours a day, he writes fiction. Presently, he's writing a play about the relationship between gay-rights and marriage, in the U.S., and Christianity."

Keyword- freelance

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