Question about results of double slit experiment

[weller2]

…]

You are confusing two things here.

First off, the interference pattern will only emerge on the detector after many photons are fired at it. Each one will hit a particular pixel on the detector. If you connect your detector to the screen, so that brightness of each pixel on the screen corresponds to the amount of photons which hit each detector pixel, ONLY THEN you will see the interference pattern. This is because the wave function describes probability that the photon will hit pixel (x,y), but when it actually hits the detector, it will hit a particular pixel.

The Copenhagen interpretation says that the wave function collapses when the photon hits the detector – it is in all possible places when in motion, but only one place is chosen randomly when it hits the detector.

Another interpretation of QM (de Broglie - Bohm interpretation) says that photons are actually point particles, and the wave function just describes how they move through space in statistical terms. So when under Copenhagen, each photon is everywhere, under Bohm, each photon has perfectly defined position all the time, you just can’t tell where it is until it hits the detector.

Now, if you put detectors at the slits, the intereference pattern disappears. This is actually quite simple: in order to be detected, the photon must interact with the detector, and this interaction changes (collapses) the wave function at the slit. Since the wave function is already collapsed, it will remain collapsed when it hits the screen. In mathematical terms, the new wave function is a convolution of the photon’s wave function and detector’s wave function – and this resulting function, for a correctly working detector, is fully deterministic (left slit / right slit). Consequently, if your detector is malfunctioning (i.e. only works half of the time), you will get a combination of the interference pattern and slit image – because half of photons will have collapsed wavefunction, and the other half will have original, uncollapsed wave function.

Now the fun part: it turns out that it if you destroy the “which-path” information, you will get the interference pattern back (i.e. un-collapse the wave function). If you want to learn something mind blowing, look up “quantum eraser”, “delayed choice experiment” and “delayed choice quantum eraser”.

 

[Aloysium]

. . . (complex physics stuff) . . .

Thanks, that was very interesting/fun.

 

[KyrieEleison17]

Thats exactly it, almost, according to Paddy’s theory of everything. Except that the speed of light is not infinite.
Think about it. Light, photons, travel like waves but not exactly. Waves need something to propagate through. They cannot travel through absolutely nothing, but they can travel through space.
So what is it that these waves propagate through or along? To understand, you can imagine a piece of absolutely non-elastic string stretched tightly from one particle on the sun to every particle on one hemisphere of the earths surface simultaneously. This string is the something that photon waves propagate along. So when the particle on the sun vibrates with enough energy to emit a photon the string connecting to all the particles on the earths surface also vibrates the particles on earth at the very same instantaneous time. This means that theoretically a photon emitted from the sun arrives on earth instantly but because of the distance between them the photon wave actually takes some time to reach earth.
If there was no connection between the sun and earth for the photon wave to move along then light could never reach us. And this something that connects us is not elastic, it has no physical properties that we can recognize. In theory the photon travels distances instantly but because of distance there is a delay before the particle on earth in turn emits a photon to the observer.

That sounds a heck of a lot like the theory of ether.

 

[KyrieEleison17]

Light was one of many things Thomas got wrong. He thought it was instantaneous:

newadvent.org/summa/1067.htm (I, 67, 2)

His sentence “For if light were a body, it would follow that whenever the air is darkened by the absence of the luminary, the body of light would be corrupted” is reminiscent of this April Fool’s paper about “darkons”:

wearcam.org/theory_of_darkness.html

If you actually cared about arriving at truth and agreement, you wouldn’t, firstly, attempt to ridicule a blameless man (Saint Thomas). As a rule when dealing with great thinkers, you should give them the benefit of a doubt that their opinions are founded on at least good reasons, even if they ultimately turn out to be erroneous or even completely incorrect.

You shouldn’t just mine Saint Thomas’s words and works looking for something that on a passing reading from a layman might look bad or silly as it just looks like an attempt at character assassination. He remains a saint for Catholics and you are on a Catholic forum. Naturally, Catholics are likely to be provoked by such an approach and moved to defend even the undoubtedly antiquated aspects of his thought or philosophy as a consequence. If, however, you proceed charitably you might receive a warmer hearing.

That being said, let’s actually bother to consider Saint Thomas’s points as a thinker on this subject, because they are closer than you think to the same questions and problems that plague quantum mechanics today.

Saint Thomas notes certain difficulties in positing light as a body.

1. If light were a body being propagated or generated from a source (a luminary), then we would expect a continual accumulation of those bodies as, e.g., pumping oxygen into a room will result in increasing levels of oxygen, at least to a point. However, we do not experience overwhelming intensity when a flashlight is used in, say, the bathroom or in a closet and neither does the bathroom or closet continually grow brighter while the light is on. This requires explanation if light is a body.
2. He notes that if light were a body, it would displace other bodies, such as the air. How come, then, at sunrise there is no noticeable displacement of the air by the Sun’s light, for instance? How does the whole air become lit without any air being displaced?
3. The “darkons” problem: if light is a body, then a room once lit and suddenly made dark (e.g. by shutting a door in the room that was adjacent to and connected it with the source of light in the adjacent room) then it follows that immediately all the luminescent bodies in the now dark room have lost their quality of being luminescent or, in other words, underwent immediately some sort of corruption. But it is not apparent why they would, as presumably they were “launched” as bodies from the luminary and remained lit but immediately lost this quality the second some door happened to be closed. What, then, happened to the luminescent bodies or what actually caused them to lose their luminescent quality? Are we seriously to believe that closing a door causes a photon to become dark? Are we to believe that light is a continuum and something more like a single, massive body extending from its source and if disconnected physically from that source by certain physical objects (like a solid door, but not glass) that the luminescent bodies thus lose their luminescent quality?

Therefore I can see how a perfectly reasonable person, absent any evidence to the contrary, might have problems with imagining light as being a body of some kind. Arguably it raises as many questions as it might answer.

Saint Thomas also brings up other considerations. Personally I don’t know exactly how modern physics addresses all of these questions. I do know, however, that the actual nature and behaviour of photons is what is responsible for all the curiosities and even eccentric theories that come out of modern quantum mechanics, including questions about whether or not photons should be conceived of as particles or waves, some combination of the two or changing or alternating depending on circumstances between the two, or even possibly something else besides.

 

[KyrieEleison17]

Another interpretation of QM (de Broglie - Bohm interpretation) says that photons are actually point particles,

Point particles? Eeek

A point has no dimensions: that would destroy the point of points. A point is perhaps better thought of as a division and, hence, begs the question: a division (a point) of what ?

Point particles would mean that you would reach “a point” where you couldn’t posit any further points (divisions), e.g., of a line. But a line can be constantly divided. Aristotle is right that in any division of this kind you always produce a new whole that can always be again divided: that division always produces something that can be divided in other words. I’m not saying that this precludes the possibility that bodies, in reality, do not reach an absolute minimum size beyond which it is possibly impossible for them to be any smaller; but this is not true in the abstract.

“Point particles” are really just evasions of the problem. They’re basically positing a physical entity that has no dimensions; trying to make something somehow both bodily and not-bodily. Given what we understand by particles, it’s necessarily a contradiction. That, or it means something which can’t be divided even in the abstract. A particle, being bodily, would be divisible, even if only in the abstract.

 

[Aloysium]

That sounds a heck of a lot like the theory of ether.

Ether would be a medium like water.
Paddy is saying that there are strings. Space would be filled with something like a radiating super-cable of strings, from the sun to the earth, and all over. The string would vibrate with the emission of electromagnetic energy. Interesting idea. I suppose that light would travel at a fixed speed because that’s how fast change happens. The farther down the string, the longer for the effect to be felt. It is actually then a string in 4D, I suppose, altho’ in 3D it is a particle. Not sure what this implies, but I like it.

 

[KyrieEleison17]

Ether would be a medium like water.
Paddy is saying that there are strings. Space would be filled with something like a radiating super-cable of strings, from the sun to the earth, and all over. The string would vibrate with the emission of electromagnetic energy. Interesting idea. I suppose that light would travel at a fixed speed because that’s how fast change happens. The farther down the string, the longer for the effect to be felt. It is actually then a string in 4D, I suppose, altho’ in 3D it is a particle. Not sure what this implies, but I like it.

What is the point of this vibration though? What explanatory purpose does that serve? I imagine there is a reason for positing this vibration.

Obviously the ‘string’ concept is meant only as an analogy, but I’m not sure how far it can be taken. I’m thinking that if the universe was filled with these strings, their vibration might cause tensions and presumably necessarily movement at any extremities that could, possibly, be detected.

It is also begs certain questions, like where these things came from or how they got there or what generated them or generates them, can they be altered or manipulated, destroyed or produced, etc. Obviously this has peaked my interest and it deserves further study on my part of the source materials.

 

[KyrieEleison17]

Einstein’s theory of relativity implies that when matter travels at the speed of light, it becomes pure energy.

Couldn’t this be understood as a kind of semantics? I.e., we will simply define as “pure energy” “that which moves at the speed light”? Wouldn’t they just become convertible? Likewise by matter Einstein obviously just means any bodily thing. Is energy then, as understood as being distinct from matter / the bodily, thus necessarily not-bodily and “immaterial”? That seems extravagant. I’m pretty sure what we call “energy” is in some sense material as it certainly is sensible. That or at least is has sensible effects.

Photons are material radiated out of fusion explosions in stars, and travel at the speed of light.

Well I think you mean to say that in the case of the Sun and the stars, photons are radiated as a consequence of fusion explosions in them. I don’t think laser pointers require fusion explosions.

The purpose of the experiment is to determine whether the photon behaved as a particle or a wave in its trip from its source to the screen. This experiment ushered in our understanding of wave-particle duality, or that matter traveling at the speed of light behaves both as matter and energy(wave).

Couldn’t we just say that matter can be energized? Doesn’t that make more sense? And when so energized behaves differently? Wouldn’t a photon just be matter energized in a certain way, then?

I find it amazing that Einstein’s theories are having such tests of strength as a consequence of some rather simple and very down to earth experiments.

 

[cornbread_r2]

MIT’s New High-Speed Camera Shoots 1 Trillion Frames Per Second

That’s fast enough to record a stream of photons. This camera is so fast that if it recorded a bullet passing through a bottle end-to-end it would take a year to record the passage.

 

[Aloysium]

MIT’s New High-Speed Camera Shoots 1 Trillion Frames Per Second

That’s fast enough to record a stream of photons. This camera is so fast that if it recorded a bullet passing through a bottle end-to-end it would take a year to record the passage.

I played it over a few times, but I could not understand what “record a stream of photons” means. My iPhone can be said to do that every time it takes a picture.
There is a lot of talk about recording the scene, and how the technique could be used in the future.
Are they just being fanciful, that the camera is just that fast?
How would they detect, record the motion of a photon passing by?

 

[cornbread_r2]

Here’s another link with a video of the recording of the stream passing through the bottle. I understated something in my previous post. According to the linked article above: “If they tracked the flight of a bullet in this way, that movie wouldn’t last 2 minutes like the one above. It would last 3 years.”

 

[inocente]

If you actually cared about arriving at truth and agreement, you wouldn’t, firstly, attempt to ridicule a blameless man (Saint Thomas). As a rule when dealing with great thinkers, you should give them the benefit of a doubt that their opinions are founded on at least good reasons, even if they ultimately turn out to be erroneous or even completely incorrect.

I don’t understand why some people try to make out that Thomas never made any mistakes. Thomas is not God, Thomas was not perfect, he made mistakes like every other person throughout history. He would readily accept his mistakes, we should too. Accept them and move on.

Saint Thomas also brings up other considerations. Personally I don’t know exactly how modern physics addresses all of these questions. I do know, however, that the actual nature and behaviour of photons is what is responsible for all the curiosities and even eccentric theories that come out of modern quantum mechanics, including questions about whether or not photons should be conceived of as particles or waves, some combination of the two or changing or alternating depending on circumstances between the two, or even possibly something else besides.

Elementary particles are so tiny that their behavior is completely outside our normal experience. There are trillions in the tip of your finger alone. There’s nothing in our common sense we can compare them with. As a result we can’t picture them, we can only make loose analogies, none of which are much good. So it is best to think of them as neither waves nor particles, they are what they are, not what we might want them to be.

This was a major part of the problem that Thomas faced: elementary particles were totally outside his common sense, and he had no means of understanding what is really going on.

They are outside our common sense too, and always will be, but we now have hundreds of years of experiments by which to understand them. Thomas would have been excited to read all that knowledge. Most of the wrong ideas rattling around on this thread would be fixed by reading a high school physics book.

 

[inocente]

Point particles? Eeek

A point has no dimensions: that would destroy the point of points. A point is perhaps better thought of as a division and, hence, begs the question: a division (a point) of what ?

Point particles would mean that you would reach “a point” where you couldn’t posit any further points (divisions), e.g., of a line. But a line can be constantly divided. Aristotle is right that in any division of this kind you always produce a new whole that can always be again divided: that division always produces something that can be divided in other words. I’m not saying that this precludes the possibility that bodies, in reality, do not reach an absolute minimum size beyond which it is possibly impossible for them to be any smaller; but this is not true in the abstract.

“Point particles” are really just evasions of the problem. They’re basically positing a physical entity that has no dimensions; trying to make something somehow both bodily and not-bodily. Given what we understand by particles, it’s necessarily a contradiction. That, or it means something which can’t be divided even in the abstract. A particle, being bodily, would be divisible, even if only in the abstract.

When you were at school and worked out the position of the Earth around the Sun in physics class, you would have treated the Earth and Sun as point particles, because all you need to know are their centers of gravity for most calculations.

It’s more difficult to get with an elementary particle because the world at that tiny scale is outside our everyday experience. But the chips in your computer and mobile phone could not be designed, and certainly wouldn’t work, if the knowledge didn’t work so it’s a bit freaky to see you using a computer to say it’s an evasion.

This knowledge has been around for a long time now (and the original double slit experiment is over 200 years old), there are lots of books in the library.

 

[Paddy_Walker]

That sounds a heck of a lot like the theory of ether.

a bit. ether was seen as a type of substance though, but Paddy’s theory sees it as the vehicle for all substances and substance itself.

 

[weller2]

Point particles? Eeek

en.wikipedia.org/wiki/Point_particle

Point particles are an idealization. People usually think about them as small billard balls. That’s not quite true, but communicates the concept The analogy works well enough until you start smashing particles together to break them, which is not what we are doing here.

My point was that under the Bohm interpretation particles are just particles (small billard balls) and the wave function describes statistics how they behave as groups. Whereas under Copenhagen the wave function describes the particle itself, which means that particles are normally fuzzy blobs which collapse to billard balls when observed.

 

[weller2]

weller2:
(continued)

So under Copenhagen you say that the (actual) particle interferes with itself which produces the interference pattern on the screen – but since each particle can only land in a definite point on the screen (the wave function must collapse at the detector), then you need to shoot many particles to actually see the pattern. Under Bohm you say that it’s the abstract wavefunction which interferes with itself, but since that wave function dictates how particles move, the particles will then produce an interference pattern as they hit the detector.

A variation of that is the ensemble (or Born) interepretation which basically says that applying wavefunction to a single particle is largely meaningless, because the wave function describes behavior of groups of particles. You don’t care what path the photon #1234 took, because you need to shoot 10k photons at the detector to see anything anyway. This also neatly avoids the Schroedinger’s cat paradox. It simply says that you should not think about one cat in one box, but about (say) 1000 cats in 1000 boxes. The probability dictates that you have 500 alive cats and 500 dead cats, you just can’t tell which is which until you start opening the boxes. Of course you may be interested to know if cat #456 is alive or dead, but why should you care, if the cats are all the same?

 

[Paddy_Walker]

What is the point of this vibration though? What explanatory purpose does that serve? I imagine there is a reason for positing this vibration.

Yes there was a reason. I was trying to explain, to myself, why something happens the way it does. Which was Everything.
The vibrating string explains einsteins ‘spooky effect at a distance’. Because the string is ‘non-elastic’ it provides the vehicle to produce the spooky effect. The photons are separated by a distance, say from the sun to the earth, but the characteristics of the photon on the sun are transferred to the photon on earth instantly. No time is required for the two photons to communicate with each other.
So the string provides that instant communication between them. Tap one end of the string and the other end instantly responds, no time passes. And the string goes on to provide the vehicle for the traveling photon energy packets and their wave-like property.
The vibrating string also explains why there is light at all. As light is now just the result of the imparting of extra energy into a system of subparticles connected by strings. The extra, un-needed, energy vibrates continually between all particles.

Obviously the ‘string’ concept is meant only as an analogy, but I’m not sure how far it can be taken. I’m thinking that if the universe was filled with these strings, their vibration might cause tensions and presumably necessarily movement at any extremities that could, possibly, be detected.

The strings, annoyingly are both analogy and a real part of the mechanics of the idea. But it would be a mistake to see them as substance. And a mistake to see them as a metaphor because they have a real effect.
I think the idea of detecting vibrating tensions at the extremities of the strings is valid. It might be that you’d find that photons and other ranges in the electromagnetic spectrum are the detectable results of the vibrating tensions at the extremities.

It is also begs certain questions, like 1. where these things came from or 2. how they got there or 3. what generated them or generates them, 4. can they be altered or manipulated, destroyed or produced, etc. Obviously this has peaked my interest and it deserves further study on my part of the source materials.

1. Where they came from is answered by saying they are the mechanical reason for sub-particles. If you can imagine two strings directly opposite each other, then, where they have joined there is a sub-particle.
2. The question of how they got there is the same question as why does the universe expand, the strings extend to the edge of the universe and are rushed along away from their opposite number by the expanding universe.
3. what generates them is the rate of acceleration of the expansion of the universe. As well as the fact of the geometric expansion of the universe itself, as in, its surface increases with distance.
4. Some of these questions have received on and off attention for some time. Destroying them would be problematic as its in their very nature to exist. But I think that sticking a particle to the surface of the universe, though that sounds strange, I think that that might result in those related strings collapsing and ceasing to exist.
   Can the strings be altered, you ask? Every time you add energy to a system of atoms, as in if you hit something with a hammer, you are in effect speeding up the expansion of the universe for those particular strings because they are now vibrating with extra energy which means that technically they are longer because the vibration moves the string while the atoms must remain in the same place. So to get rid of this potential anomaly of increasing the speed of the expanding universe the imparted extra energy is pushed throughout the wider system instantly first as the spooky effect at a distance and a little later the actual extra energy wave manifests itself as, lets say, a photon of light emitted from the nearest particle to be excited by the wave.
   Incidentally this also explains how a photon can be detected through a slit screen by passing through the slits to the side of the screen when the direct and shortest route for the photon through the center slit is blocked. The photon apparently has to turn at the offset slit and search for the detector.
   But in Paddy’s theory all particles are always connected by strings so that even when the direct shortest line of sight path for the photon is blocked it, the wave packet traveling along the string between the particle, will then choose the next shortest route to the detector. This is because the particles are still connected by strings even though there is a screen between them. The photon travels on strings between particles.
   Paddy’s Theory of Everything goes on and on to explain Everything, including; What is gravity?; What is the electroweak and electrostrong force?; What is an electron? What is the electrons magnetic moment? and, What is the Grand Theory that explains Everything, altogether? plus any questions relating to the above.

 

[weller2]

MIT’s New High-Speed Camera Shoots 1 Trillion Frames Per Second

That’s fast enough to record a stream of photons. This camera is so fast that if it recorded a bullet passing through a bottle end-to-end it would take a year to record the passage.

Any camera can only record photons which hit the camera. If the photons are flying parallel to the detector, it will not see anything.

A laser beam in air is not really visible, unless you have really dusty / foggy air, which causes some of the laser photons to be scattered in your direction.

The way they filmed light passing through the bottle was that the light impulse was scattering off the air in the bottle, which means that some photons bounced off the air particles, flew to the side, and hit the camera, which recorded them.

This is a bit like the light echo effect which can be sometimes observed in astronomy:

Hubble Images - NASA Science

Hubble images of the universe. The page includes science images, Hubble Friday images, mission operations images, and servicing mission images

hubblesite.org

All the light here comes from the red star in the center, and was initially flying in the plane of the image, but some of it bounced off the dust particles and flew in our direction (out of the screen) so it could be recorded.

 

[KyrieEleison17]

I don’t understand why some people try to make out that Thomas never made any mistakes. Thomas is not God, Thomas was not perfect, he made mistakes like every other person throughout history. He would readily accept his mistakes, we should too. Accept them and move on.

Did I say he never made mistakes? Who are you talking to in your post? Certainly it’s not me. People can’t have a conversation with you if you are just talking to yourself the whole time. Please actually read the substance of my post. I actually criticized you for a superficial reading of Saint Thomas and then you prove your habit in your response right here by doing the same thing to me.

Elementary particles are so tiny that their behavior is completely outside our normal experience.

Okay. But ultimately they have to be responsible for the macro level of evidence or else there would be no point in studying them if they had no bearing on daily life or reality. Scientific theories are supposed to provide explanations for how the world works and the phenomena we experience.

There are trillions in the tip of your finger alone. There’s nothing in our common sense we can compare them with.

This is like saying that because something is super, super, super big … like bigger than Texas, then you can’t think of how big it is, conceptualize it or even visualize it. But we can visualize or imagine objects on any scale. It’s quite easy actually. I can’t visualize something that is infinite as that would immediately mean giving it some finite form; but it is possible to grasp the concept and implications of the infinite or something’s being infinite.

As a result we can’t picture them,

We can mentally picture or represent any bodily thing on any scale.

we can only make loose analogies, none of which are much good. So it is best to think of them as neither waves nor particles, they are what they are, not what we might want them to be.

That’s nice inocente but I will leave it to the scientists actually studying the phenomena to determine how they should be properly conceived based on their behaviour as demonstrated in experiments and based on evidence. Presently photons are seen to sometimes act like waves and other times like particles.

This is one of my concerns about modern dogmatic science. It will attack the Church for frustrating scientific development but then they will turn around and dictate how you must think about any scientific problem when the evidence is open and inconclusive because it makes them uncomfortable to draw conclusions or speculate outside their box.

This was a major part of the problem that Thomas faced: elementary particles were totally outside his common sense, and he had no means of understanding what is really going on.

Thomas could understand the basics of elementary particles, atoms or corpuscules. He was a trained philosopher and familiar with the concepts at least from the history of philosophy. Maybe if you bothered to know a thing or two about Saint Thomas rather than making caricatures of his thinking or arguments you wouldn’t utter such patent nonsense.

They are outside our common sense too, and always will be,

More dogma and now you’re even on the verge of superstition. But I suppose it depends on what you understand by common sense. I understand rational and logical by it. I understand that however the microscopic layers of physical reality work, they have to conform to and explain what we actually see and experience, otherwise they would have no connection to reality and couldn’t possibly serve any practical use or purpose. But I can’t keep you from thinking reality is magical and illogical but I certainly don’t have to personally accept it. This is not a Disney movie.

 

[KyrieEleison17]

Any camera can only record photons which hit the camera. If the photons are flying parallel to the detector, it will not see anything.

A laser beam in air is not really visible, unless you have really dusty / foggy air, which causes some of the laser photons to be scattered in your direction.

The way they filmed light passing through the bottle was that the light impulse was scattering off the air in the bottle, which means that some photons bounced off the air particles, flew to the side, and hit the camera, which recorded them.

I was wondering how this was supposed to work also. I was a little worried that it was like another machine purporting to detect or take pictures of individual atoms - like the machine that presupposes a sharp tip that is a single atom at its end and that enables us to detect single atoms. I wondered how they managed to confirm their instrument’s tip was filed down to a single atom when admittedly they hadn’t any way yet of determining that was actually the case. I always get a bit nervous when these things are admitted to be “reconstructions” based on “mathematical equations”.