1

Physics, Astronomy & Cosmology / Re: What happens when both slits are observed by in the double slit experiment?

« on: 11/11/2019 02:55:14 »

I watched as single photons passed through a single slit producing a single bar pattern.

I believe this only happens in simulation, never really happens in actual experiment. The images below show what you'd get from single slit and double slit experiment.

With a normal single slit apperture, you will still get interference pattern due to diffraction effect.

2

Physics, Astronomy & Cosmology / Re: Does information have mass?

« on: 08/11/2019 21:42:03 »

a blank thumb drive still has a big consecutive swath of 0's, which is arguably information.

One of the definitions of information is "what is the most compact way of representing this data?".
- If there is a more compact way of representing the data, then the data is not 100% information.

In this quote, you summed up 64 GBytes of blank USB drive in just 30 bytes: "a big consecutive swath of 0's".
That demonstrates that the visible* information content of a blank USB is pretty low.


*I know a USB drive has some internal content which is not externally visible, like bad block maps, that does convey information to a blank USB drive...

3

Physics, Astronomy & Cosmology / Re: Does information have mass?

« on: 08/11/2019 20:23:07 »

Information has entropy associated with it.
Changing information changes the entropy, and this requires energy.
...
See: https://en.wikipedia.org/wiki/Entropy_in_thermodynamics_and_information_theory#Negentropy

To expand on this, according to the linked page, the energy is not the mass of the information, but the minimum energy required to save/change a bit of information.  Hence a blank terabyte thumb drive (or say one with the first half set to 0 bits and remainder 1) masses the same as the same thumb drive crammed with a library of findings.  But it takes this minimum energy (and creates the resulting entropy) to change it from one state to the other.

In my simplistic understanding: If some object carries information, it carries energy; this energy has an equivalent mass, and an associated gravitational field.

I don't see how this follows from the linked page, but any object has mass, and mass has energy, so it indeed stands that energy is required to store information in an object.  But it doesn't follow that an object with information masses more than the same object without information (all else being equal). That's a thin statement since a blank thumb drive still has a big consecutive swath of 0's, which is arguably information.

4

Physics, Astronomy & Cosmology / Re: Does information have mass?

« on: 08/11/2019 19:50:30 »

The sky is blue. That is information about the sky. Does it have mass? No, it is descriptive. The photons have energy, which has an equivalent relativistic mass. Define your interpretation of information.

5

Physics, Astronomy & Cosmology / Re: Does information have mass?

« on: 08/11/2019 18:46:17 »

I read about entangled atoms/electrons transferring information across vast distances ‘instantaneously’ or ‘near-instantaneously’. I also read that the speed of this information transfer was 'around 3-trillion meters per second – or four orders of magnitude faster than light.                   ( https://futurism.com/chinese-physicists-measure-speed-of-quantum-entanglement-2)

There is no evidence of actual information transfer with entanglement scenarios.  If there was, it would not have a finite speed (a mere 4 orders of magnitude) as this pop-science article suggests.  Certain interpretations of quantum mechanics posit such information transfer, and also transfer of information arbitrarily far into the past, but without a falsification test, such interpretations cannot be verified.
So the rule of thumb is: If you can't send a message with it, it isn't information transfer, and hence no faster than light information transfer has ever been demonstrated.

My understanding is that anything with mass cannot travel at or beyond the speed of light.

Not even things without proper mass can, according to any theory that holds to the principle of locality.  Said interpretations mentioned above of course must deny this principle.

6

Physics, Astronomy & Cosmology / Re: Does information have mass?

« on: 08/11/2019 18:03:27 »

Information has entropy associated with it.
Changing information changes the entropy, and this requires energy.
In my simplistic understanding: If some object carries information, it carries energy; this energy has an equivalent mass, and an associated gravitational field.
See: https://en.wikipedia.org/wiki/Entropy_in_thermodynamics_and_information_theory#Negentropy

This leads to a requirement to revisit the joke about the [idiot/ boss/ whatever]  who is seen deleting files from his laptop to make it lighter.

7

Physics, Astronomy & Cosmology / Re: What happens when both slits are observed by in the double slit experiment?

« on: 08/11/2019 12:28:03 »

I think it's fair to say that I could not get into any meaningful discussion with you guys because of our differing levels of scientific/mathematical understanding on the whole subject.

I hope we can still have a meaningful discussion, and I’ll try not to be too technical. The maths is only a description of what happens, but sometimes it’s hard to put into words which is why the popsci press opt out and give oversimplified explanations.

seemingly a particle before the double slit and a wave after the double slit ... and reverting back to a particle when 'observed' after the double slit.

The wave or particle is only a description of how the light behaves, not really a description of what it is.
Ok, to keep it simple and stick with light. When light is emitted by an atom it is as a very short burst of electromagnetic oscillation - a short wave. So that burst, which we call a photon travels as a wave, but the way we detect it requires it to interact with another atom. That atom could be in a photographic film or in a camera ccd, but that interaction shows up as a dot, just as if a particle had hit the detector. In other words, when the wave hits the detector it can be modelled as a particle. This is why you often hear physicists say the photon travels as a wave but is detected as a particle.
It is fair to say that most modern physicists consider the wave/particle duality thing a bit ‘old ways thinking’, they are more likely to ask how you are detecting or measuring the result of your experiment.

The point is that the photons travelling through the slits should produce an impact pattern similar to the double slits.

‘Should’, but only if they are travelling and behaving as particles. Electrons are interesting because we tend to think of them as particles - little hard bullets - but when they are moving they clearly behave like waves, if fact when they were first discovered they were called cathode rays (which is where we get the name cathode ray tube).
One thing I should mention here is that the prime objective of physics is not to provide an explanation of why something happens, the objective is to observe, model and predict behaviour; that’s what Newton did, he didn’t explain gravitation he just described what it did - with very useful accuracy. His model was of a force acting at a distance, today we model it as a field through Einstein’s field equations and that’s a little more accurate.
Sometimes we can see clearly how a thing works, eg we start a car and the wheels push against the ground providing a force that moves the car forward. Some other thing are less easy to predict eg we flip a coin, we can’t predict exactly which way up it will land, but we do know that in a large number of flips we will get approximately 50:50 and we can do a lot of predicting with the uncertainty of which way it will land. This same uncertainty works at the quantum level and allows us to use probability to make some very accurate predictions - we might not know the exact position of an electron in an atom, but we can make very accurate predictions about where it will spend the majority of its time.
Probability is worth learning about because it really helps us understand a lot about the world around us. So, I’m going to go a bit technical and hope you will follow us by learning more about probability.
When we fire bullets (particles) at a slit they will, as you said, go through one slit or the other and form the 2 slit shadow we expect. This is because in probability we say the events of a bullet passing through one slit or the other are mutually exclusive (it can’t do both) and more importantly neither action can influence or have any effect on  the other (we say they are uncorrelated). In probability mutually exclusive, uncorrelated evens follow the sum rule, their probabilities add which is what we see with bullets, but with quantum objects which are coherent, it is the square of the sum which gives us the probability of what we see on the screen. There is growing evidence that this is the way the world really works, but at our big world level we lose the coherence between quantum objects and we start to see the probabilities we are used to. However, when we come to modelling the slit experiment we can look at it and say that the electrons going through both slits is one way of modelling it because it works. So when physicists say it goes through both slits and interferes with itself, they are really using a shorthand for ‘that’s the way we can model it’. At the moment we don’t have enough information to know exactly how this works, but we can predict what happens to a very high degree of accuracy.

@jeffreyH  has put up a video of polarisation, this raises another problem which occurs when we view the quantum world. We view polarisation as horizontal/vertical, right/left and electron spin as up/down, just as we would say a coin is heads/tails. But it’s not that simple and the polarisation and spin are best represented as complex numbers (which can also be represented as vectors).

PS Looking back I notice @alancalverd has given a very similar explanation to mine, please read it carefully it’s important. I hope mine has some extra detail you find useful. Remember, 62 is not too old to learn about probability, vectors etc, keeps the grey cells on their toes.

8

Physics, Astronomy & Cosmology / Re: Does information have mass?

« on: 08/11/2019 10:49:45 »

Information has entropy associated with it.
Changing information changes the entropy, and this requires energy.
In my simplistic understanding: If some object carries information, it carries energy; this energy has an equivalent mass, and an associated gravitational field.
See: https://en.wikipedia.org/wiki/Entropy_in_thermodynamics_and_information_theory#Negentropy

9

Physics, Astronomy & Cosmology / Re: What happens when both slits are observed by in the double slit experiment?

« on: 07/11/2019 23:12:06 »

Relativity is a classical and deterministic theory. Quantum mechanics introduces probability, which is not deterministic.

I don't think relativity theory says anything about determinism one way or the other.

QM theory also doesn't say. It just says that the outcome of an experiment cannot be predicted regardless of how much information of the system can be measured ahead of time.
There are interpretations that are hard indeterministic (fundamental randomness), soft deterministic (randomness is phenomenally emergent, but not fundamental), and hard deterministic (there is only one possible future which could be computed if all variables were known).

10

Physics, Astronomy & Cosmology / Re: Does information have mass?

« on: 07/11/2019 22:06:56 »

When I read that pairs or groups of particles can act and react in a way that would indicate they share the same information regardless of their distance apart ... even a cosmic distance apart ... or they receive and act upon the same information instantaneously ... then I have to ask, can information do such a thing when we have a speed limit of C , the speed of light?

No evidence of this has ever been demonstrated.  In particular, no message (information) has ever been sent at faster than c.
If it did, I'm not sure that would be a demonstration of it having mass or evidence that it cannot have mass.

11

Physics, Astronomy & Cosmology / Re: Does information have mass?

« on: 07/11/2019 22:05:35 »

I would say that information as a concept doesn't have mass, but anything that can actually store information will have a mass (at least one associated with its energy via E=mc²). That mass-energy, however, can be arbitrarily small (there is no known upper limit to the wavelength of a photon, except, perhaps, the diameter of the Universe).

12

Physics, Astronomy & Cosmology / Re: What happens when both slits are observed by in the double slit experiment?

« on: 07/11/2019 21:40:57 »

Relativity is a classical and deterministic theory. Quantum mechanics introduces probability, which is not deterministic.

13

Physics, Astronomy & Cosmology / Re: Does information have mass?

« on: 07/11/2019 21:20:31 »

Define your interpretation of information.

14

Physics, Astronomy & Cosmology / Re: What happens when both slits are observed by in the double slit experiment?

« on: 07/11/2019 13:25:35 »

You really need to abandon the particle/wave duality business to make progress in physics. Photons, atoms, indeed everything, behaves as it does because it is what it is, not what you choose to model it as.

Quantum mechanics gives us an excellent predictive model of the behaviour of very small things, but doesn't say what they "are". Continuum mechanics gives us an adequately predictive model of mesoscopic entities that allows us to build houses and fly to the planets. The important question to ask of quantum mechanics is "does it scale up to the observed behaviour of radio waves and billiard balls?", which it does. Likewise the test of relativity is "does it scale down to Newtonian mechanics if v<<c?", which it does.

The problem with poking a particulate photon through two slits is manifold.

1. Only half the energy can go through each slit, so the wavelength of the emerging "photons" will be twice as long - but it isn't!   

2. If we rotate the receiver, we will alter the time at which the two bits of photon reach it, so they can't interfere - but they do!

Equally, however, if we presume a wave passing through both slits, all the interference peaks will occur simultaneously, however weak the source (down to one photon at a time) - but they don't!

It gets even more exciting when we pass "solid" objects like electrons, atoms or buckyballs through a diffraction grating. There's no way they can disintegrate and recombine at the receptor (if we move the receptor further away, where does the recombination happen?  If we remove it altogether, have we created partial electrons wandering through space?) but they form the predicted pattern!

The answer: believe what you see, and choose the most appropriate model to predict what you might see next time, but don't be surprised if something else happens - it just means your model was incomplete.

15

Physics, Astronomy & Cosmology / Re: What happens when both slits are observed by in the double slit experiment?

« on: 07/11/2019 12:12:29 »

Lots like when 2 oceans meet.

The pattern is indeed a lot like what you get with water if the water waves on the left are indeed planar and of consistent wavelength.  But water waves are not particles, and in fact no water molecule travels with its wave.

The diagram makes it look like light must be monochromatic and planar, implying that photons going through one slit interferes with different (but synced) photons going through the other.  This is completely false.  Even if one photon at a time is fired (so not planar with other photons in any way), the interference pattern appears.  If the photon went through one slit, it would produce a one-slit pattern (a bell curve distribution).  The only way the interference patter can appear is if each photon behaves as if it goes through both slits. This is what is meant by them saying that the photon is in superposition of going through each of the slits.  Water doesn't behave that way.

16

Physics, Astronomy & Cosmology / Re: What happens when both slits are observed by in the double slit experiment?

« on: 07/11/2019 09:20:36 »

If you instead of that want to think about it as fields of different energy density interacting it becomes one more interpretation :)
In that case most of what we take for granted disappear. A hole isn't a hole, it's something of a 'energy density' or maybe lack of, looking as a hole to us. and a 'particle' is not a projectile, instead it becomes a emanation of either ' one field's ' interaction with itself or fields interacting. I think that suits my own taste better than the other approaches. As you wrote light has a wave particle duality, and I see that as absolutely correct.
==

there is one big hurdle with the field idea, to me then. And that is how to make it fit relativity. What that means is that our universe is 'observer dependent' looked at from relativity. You can 'shrink' this universe through mass f.ex or by speeds. And those effects are no artifacts but physical laws. So if we define a universe as a field interacting with itself, or fields, we still need to incorporate relativity in it. And that is where it becomes really weird.

What it means is that everything might be said to have different 'speeds' versus your observation/platform. Which means that every object you observe will have its own definition of a size and time of/in this universe. Scaling it down we meet particles and passing that 'breaking it up' fields.  That's also where it starts to hurt my head.

there is one more dimension we need to add to fields and that is time. Depending on how you look at it it becomes a arrow pointing one way, or a ocean. If you think of it as a ocean then that can contain a lot of possibilities, and also catch the way Einstein defined SpaceTime, consisting of four dimensions. three double ended and one with only one direction. And if you set that together with observer dependencies you get not only one universe but a multitude, one each for each 'observer'.

If you conclude that neither Relativity, nor QM (and fields) are satisfied with what we naively think of as our reality and universe, I would agree :)

==

you could also think of it as an 'ocean' consisting of probabilities in where 'time' is directly connected to decoherence giving us outcomes which then becomes our arrow. But 'probabilities' is also a snake biting its own tail in that it comes from us collecting statistics. so defining it as probabilities doesn't lead us any further as I think, but that may be where I'm wrong?

It may depend on how we define time.

17

Physics, Astronomy & Cosmology / Re: What happens when both slits are observed by in the double slit experiment?

« on: 07/11/2019 09:05:11 »

Don't need mathematics to think about it Lloyd. Only if you have another interpretation and then want to have it published. Most of the stuff at the QM level is probabilistic, everything is thought to be a result of that and decoherence. Decoherence can be seen as this small probabilistic level reaching some sort of threshold of interactions and scale leaving the world as we experience it normally.

So in a two slit experiment there is a probability of either one or both slits being 'engaged' by one particle. And the way it unfolds will be defined through your setup. The idea of indirect evidence is increasingly popular in those situations as every time you probe a particle you also force it into a set behavior aka  a 'wave collapse'. Whether one want to think about it first as waves or as particles is more of a question of what you believe than what is right here. I've read physicists stating the particle view while other state the wave view.

18

Physics, Astronomy & Cosmology / Re: What happens when both slits are observed by in the double slit experiment?

« on: 07/11/2019 03:09:55 »

The point of the double slit experiment is that one or two slits, the transmission medium behave the same.  Its the wave effect, if you put waves through two slits you get destructive and constructive interferance, leading to high and low points along a wave crest. Ie a wave crest now has peaks and troughs along it aswll as a trough between the following and preceeding waves. Lots like when 2 oceans meet. Point is that light is behaving with these wave characteristics.

19

Physics, Astronomy & Cosmology / Re: What happens when both slits are observed by in the double slit experiment?

« on: 06/11/2019 23:32:06 »

Also worth viewing

20

Physics, Astronomy & Cosmology / Re: What happens when both slits are observed by in the double slit experiment?

« on: 06/11/2019 23:19:07 »

@Lloyd Quantum mechanics is just weird. That's the way it is. Probability is the key. It wasn't chosen to be that way by physicists. Look into polarised light and filters.
https://www.khanacademy.org/science/physics/light-waves/introduction-to-light-waves/v/polarization-of-light-linear-and-circular

This is where we eventually get to Bell's inequality. Go read up on it!