Ask any question you want about Physics

originally posted by: mbkennel

originally posted by: Phantom423

originally posted by: Bedlam

originally posted by: Arbitrageur
But, Joel wasn't talking about your own personal wave function, he was talking about the wave function of photons. In that case slits can be smaller but I wouldn't say they are like having no slit at all.

It certainly is if the photons are big and mushy. If you have a radio wave, it won't go through an opening that the wave can't fit through. I'm pretty sure that light acts the same way.

If the photon acts like a particle and not a wave, does that make a difference as to the size of the slit? Why does the photon have "size" in the first place if it doesn't have mass (at least in this context)?

Mass doesn't matter here.

Here's the physics. Impinge an electromagnetic wave upon a conducting flat sheet. What is really happening? The electrons in the conducting sheet are accelerated by the incoming EM wave, and themselves create new EM wave which happens to nearly perfectly cancel (except for an exponentially decaying part) what would have been the propagating EM wave going through the sheet. So on the backside of that conducting sheet you see no propagating waves.

Now, add a small slit. If the slit is substantially smaller than the wavelength, then even though there's some restriction in the movement of the electrons on account of the slit, what is still able to move generates a counteracting wave pretty effectively which blocks off most of the incoming wave.

If the slit becomes larger and larger then the ability to generate a counteracting wave is diminished more and more behind the hole, and more of the incoming wave can get through.

All of this is exactly calculable from Maxwell's equations and is a typical problem in an undergraduate electrodynamics class.

Thanks for the reply.

Bedlam originally posted this:

originally posted by: Bedlam It certainly is if the photons are big and mushy. If you have a radio wave, it won't go through an opening that the wave can't fit through. I'm pretty sure that light acts the same way.

What is a "big and mushy" photon? I thought a photon was a function of its energy and its energy is a function of its wavelength. So if the slit is very small and the amplitude of the photon wavelength is large, the scenario you described applies. My question was if the photon can act as a wave and a particle, why can't the particle pass through the slit?

a reply to: Phantom423

I'm thinking, that's because photon as a particle only when 'detected', all other instances photon is a quanta of energy with wave like characteristics.
As it travels it is wave like, when caught (detected/absorbed) it is collapsing to the instance with particle like properties.
According to this logic, photon as a particle won't 'fit' through the slit because it is not a particle yet. If the slit small enough, photon interacts with matter and absorbed (wave contracts to a point like particle).

That's how I see it.

a reply to: Arbitrageur

Physicists use virtual photons to model why two electrons repel, not real photons.

they use those "virtual photons" which by the way are just an invention for mathematical equations, because what they do is describing the observable and not explaining the observable.
and... real photons... there is no such thing as real photons !

photon invention, I'm talking about the so called "real photons' now was not enough so another invention "virtual" one must help out...


why don't someone explains why two like charges repel an opposite charges attract ?
why nobody explain what a charge is instead of only describing what it does ?

all existing theories do just describe what is happening, non of them will tell you why !

so... you can talk a lot and wonder about my extra "a" where it does not belong, knowing "why" you do not !

a reply to: Phantom423

originally posted by: greenreflections
According to this logic, photon as a particle won't 'fit' through the slit because it is not a particle yet.

"Particle" refers to the fact that it's "quantized" meaning it comes in packets. I'm not aware of experiments which show that this quantized nature fails to exist. So I think the quantization is probably always present but whether it's observed in experiment or not depends on how the experiment is conducted. The longer the wavelength the more difficult it is to observe quanta of EM, for example.

If the slit small enough, photon interacts with matter and absorbed (wave contracts to a point like particle).

It depends on what material the slit is made of and the wavelength or frequency of the EM radiation. If you're talking about a sheetrock wall, radio waves can pass through the wall. If you're talking about conductive material like the grid on the door of a microwave oven, it's actually like a partial Faraday cage effect: the EM radiation causes electrons inside the conductor to move and those moving electrons create their own fields which largely (but not completely because of the holes) cancel out the EM radiation striking it.

originally posted by: moebius
Also trying to assign a spatial size to a photon is kinda sketchy imho. There is no slit too small for a photon to pass through, the size only affects transmission probability, which is never zero.

Yes. This is another reason that the "slits" or holes in a microwave oven door aren't "like no slits at all". They don't stop 100% of the radiation, only most of it. They have to meet a standard which is safe for human exposure a certain distance from the door, and generally the amount of radiation at that distance is less than a tenth of this safety limit, which means it's safe, but you're right, it's not zero.

However if you remove the slits (or the holes in a microwave oven door for example), then a solid conducting sheet or enclosure generally does a fairly good job at blocking EM radiation, with certain caveats.

originally posted by: KrzYma
a reply to: Arbitrageur
... real photons... there is no such thing as real photons !

Light exists, right? And it has a quantized nature, right? The evidence for this is overwhelming. The quanta of em radiation are called photons. To say photons don't exist is to say that light doesn't exhibit quantized behavior, and such a claim disagrees with experiment, and when a claim disagrees with experiment, it's wrong.

photon invention, I'm talking about the so called "real photons' now was not enough so another invention "virtual" one must help out...

This is an improvement over your previous post where you didn't know the difference, since now you at least admit they aren't the same. Before you were lumping them both together in a very confusing manner.

why don't someone explains why two like charges repel an opposite charges attract ?
why nobody explain what a charge is instead of only describing what it does ?

If you can be the first to do it in a convincing way, nobody is stopping you. We know more now than we knew 50 years ago, and then we know more than 50 years before that, and so on for the past four centuries. Maybe some time in the future we will figure it out. Wouldn't life be boring if we had all the answers? Not knowing some things makes life interesting and gives us some things to wonder about and figure out.

a reply to: Arbitrageur

Particle" refers to the fact that it's "quantized" meaning it comes in packets. I'm not aware of experiments which show that this quantized nature fails to exist. So I think the quantization is probably always present but whether it's observed in experiment or not depends on how the experiment is conducted. The longer the wavelength the more difficult it is to observe quanta of EM, for example.

Yes, comes in packets, quantized.

All I know is that GR cannot be quantized. It is a gradient, continuous, meaningless to break into portions.

Each spatial position is infinitely different from the previous when inside gravity effect well.

For a solid physical body being inside gravity affected area means its shape will begin to shift toward gravity source.
It will elongate toward the source dragging QM composure of physical body (the whole) along. To outside observer
physical object will appear' falling. Falling toward gravity source.

Lots of folk on ATS refer to gravity as some sort of magnetism. It does feel like it but read Einstein discovery about
what space-time is.

I have a coffee maker like this:

www.vietnamese-coffee.com...

A strainer on bottom which rests on cup opening; a chamber which goes on top of that which ground coffee is put into; a strainer that slides in the chamber to rest atop the coffee, and then water is poured atop that;

I have semi more recently been making a percentage decaf and a percentage regular for a single cup, usually always more decaf than regular;

Will the resulting cup of coffee be any different if the decaf is poured first, or if the regular is poured first; lets say there was 70% decaf that nearly covered the area of the bottom chamber, and then regular poured on top of that; compared to 30% regular poured first nearly covering bottom surface area, and then decaf on top.

a reply to: ImaFungi

Depends on how hot the liquids are, but as they are of the same density and are comparable (basically they are the same liquid... mostly water). The Decaf and regular should mix very readily, faster so if both liquids are very hot.

The resulting cup should be identical regardless of which is poured first.

Only possibility of a difference is if the two liquids have very different densities and viscosities that they might not mix very well. But in the case of coffee... decaf and regular... they likely mix very very well

a reply to: greenreflections

I like De Broglie's proposition regarding Inertia. Or, at least I think I do. I dunno I like to read a lot, not sure if I
actually understand any of it, but then again i'm not the brightest bulb on the forum and deep thought on causation has never been my strong point.

I always felt that in essence De Broglie believed that inertial mass was essentially caused by vibrational energy of a particle caused by local EM oscillations in a field, or something like that. I probably got that wrong. But you know me, not like that ever stopped my crazy conjecture.

So, De Broglie and his thoughts on energy and mass oscillations got me thinking. Usually a bad thing.

He thought his de broglie wave at the compton frequency came from the particle in question it's self somehow.

(Dave veers hard towards the alfalfa fields here) What if the oscillations are really caused by the particle itself resonating with the high frequency ZPF or something like that. Like what if De Broglie's oscillations are vibrational leakage of energy due to a mismatch between say and electrons Compton Frequency and the ZPF? And that causes a scattering effect which we figure as inertial mass? '

So find the right frequency to match the two and you suppress the scattering effect?

Damn that hurt to write. Probably hurt even more to read.

a reply to: BASSPLYR

Hey BASSPLYR,

Totally agree with "makes my head hurt" reading your post!

If I get this wrong just say so and I will stop!

The frequency mismatch is quantum field cross frequency leakage between the interactions with the quantum foam itself? And like a pair of Bose headphones, you take the opposite frequency to cancel out (phase mismatch) and inertial mass is freed?

Not only the alfalfa fields but right back into the quantum foam swimming pool!

The idea is cool but all those Feynman diagrams have to sum back up somehow to the "real world" and wouldn't keeping some interactions from happening mean your missing something "here"? And couldn't the magic QF just create a particle and screw up your carefully tuned frequency setting ("Don't touch my stereo!"). And isn't that EXACTLY what the problem is with quantum gravity? Too many interactions (infinity interaction--and I really mean the whole entire universe worth) to calculate except in the Newtonian sense (F=ma).

It makes more sense to try to block your interactions with the quantum foam itself as much as possible to keep the cryptic graviton away! You know, instead of some ear buds blocking noise you have an arena size PA cancelling out the sound so you can sit and ponder 6 dimensional De Sitter space in a huge cone of silence!

So I guess a question is in order. Is there a way to minimize or block quantum field interactions with the macro world (besides the hover board, I mean)?

a reply to: TEOTWAWKIAIFF

Sadly, in my world view I don't feel at the moment that gravity and inertia are primary forces, but I by product of other stuff.

So, to me, no it wouldn't be robbing paul to pay peter. It would be more like greasing a wheel to reduce friction, or how making a surface matte to reduce glare.

The ZPF makes the electron oscillate at it's Compton Wavelength. That, to me, the De Broglie wavelength is the (to borrow a term from tuning my bass guitar, partly where I got the idea) the beat frequency of that oscillation when framedragged or whatever the term is for in motion.

The way I look at it like this if we can find a resonant frequency between both the Compton Wavelength of a particle and the ZPF that would be your "grease" and you'd get less "friction".

Instead of phase cancelling, matching impedance between the two instead to remove resistance. 367 ohms of resistance.

originally posted by: ImaFungi
Will the resulting cup of coffee be any different if the decaf is poured first

Decaf what? Coffee grounds? Are you layering the coffee grounds one on top of the other? Or pouring pure decaf grounds, making that, then pouring pure regular grounds and making that, then mixing the liquids?

If you're layering the grounds and the regular grounds are on the bottom and if it works anything like my coffee maker, that will probably give you a hair more caffeine than putting the decaf grounds on the bottom since the caffeinated grounds would be on top where they wouldn't get soaked quite as well. This has to do with the fact that there are limited holes where the hot water can drip down on top. That pic you posted is so tiny it's hard to see any detail and I'm not sure I understand your methods.

If you're not layering the grounds I agree with Eros it won't matter which you do first, and even if you are layering the grounds, it depends on how evenly the hot water is distributed when it strikes the top layer of grounds.

BTW if I want less caffeine per cup, I just add water, though that dilutes the flavor too so I guess you need decaf if you care about that. I never drink decaf, but some of my "regular" diluted with water cups of coffee probably have less caffeine in them than the way some people make their stronger decaf (Decaf doesn't mean zero caffeine, just less than regular coffee).

originally posted by: greenreflections
Yes, comes in packets, quantized.

All I know is that GR cannot be quantized.

GR makes predictions of a small particle as if the position and momentum of the particle can be simultaneously known, and we already know this to not be true from quantum mechanics, so we need a better theory which will be harmonious with quantum mechanics. Easier said than done.

Lots of folk on ATS refer to gravity as some sort of magnetism. It does feel like it but read Einstein discovery about
what space-time is.

I don't know why they think that because magnets can repel and I've never seen gravity do that.

a reply to: Arbitrageur

hey I could use some advice. in terms of caffeine.. dark roast or light. or, is there not much difference.

at work we have some Columbian roast via a kurig machine and although it's caffeinated it doesn't seem to have much punch to it. thinking about ordering a darker blend in the hopes it would have more caffeine, but I'm not sure if color makes a difference.


any thoughts? or should I just bite the bullet and pay 4.50 for vpx red line at the local 7-11. that has caffeine up the wazoo but damn nearly five bucks!?!

anyone recommend a Kurig available blend that will whoop my butt with caffeine?

a reply to: BASSPLYR
Actually that question may involve some physics believe it or not, the physics of roasting. I've never seen any measurements but I found a source that claims that roasting burns off some of the caffeine which at least sounds plausible, so this would mean the darker roast might have a little less caffeine because of that.

I'm not aware of problems with caffeine in moderation but if you get too much it's not good for you.

10 Things You Might Not Know About Caffeine

The naturally-occurring substance with a bitter taste stimulates the central nervous system, making you feel more alert. In moderate doses, it can actually offer health benefits, including boosts to memory, concentration and mental health. And coffee in particular, a major source of caffeine for Americans, has been associated with a host of body perks, including a possible decreased risk of alzheimer's disease and certain cancers.

But in excess amounts, caffeine overuse can trigger a fast heart rate, insomnia, anxiety and restlessness, among other side effects. Abruptly stopping use can lead to symptoms of withdrawal, including headaches and irritability.....

A strong, rich flavor might seem to indicate an extra dose of caffeine, but the truth is that light roasts actually pack more of a jolt than dark roasts. The process of roasting burns off caffeine, NPR reported, meaning those looking for a less intense buzz might want to opt for the dark roast java at the coffee shop.

I've tried lots of different roasts/flavors, and the coffee supplier for our office had lots of flavors we tried out, but I never liked any of the dark roasts. Dark roast seems like a euphemism for partially burnt and that's how it tastes to me.

a reply to: Arbitrageur

Hmmm... So maybe the lighter roasts are a better option then. Interesting link. As far as flavor goes the kurig machine in our office is a home use one that somebody brought in and the poor thing has been making 20-30 cups of coffee a day for a few years now. I thinks its on its way out because the coffee tastes like a blend of diesel and battery acid. I've actually winced and coughed when drinking it because it often hits the taste buds harder than strait up scotch.

Any blends that use beans that have higher amounts of caffeine? Maybe it's not the color of the roast but more like Java vs Colombian and which bean they use naturally have more of the good stuff.

Either way I think I may be partially immune to caffeine. I can drink a red bull and fall right asleep. Hope I'm not thrashing my adrenal glands or something.

a reply to: Arbitrageur

Coffee drinker here!

The lighter the roast the better the flavour and higher caffeine content.

The darker the roast the longer it's been roasted and tends to have a stronger, more bitter flavour and less caffeine.

a reply to: BASSPLYR

Costa Rican is always a good choice! Not sure if it comes in K-cups though.

Also, if you want o try an "extra kick" I use some freeze dried espresso (think it is Mexican--comes in a red-white-green jar) in mine. Also works as an iced coffee on those hot days.

And as a guitar player I now get your idea a bit better! Thanks!

originally posted by: Phantom423
What is a "big and mushy" photon? I thought a photon was a function of its energy and its energy is a function of its wavelength. So if the slit is very small and the amplitude of the photon wavelength is large, the scenario you described applies. My question was if the photon can act as a wave and a particle, why can't the particle pass through the slit?

In a nutshell, because when the wavelength is longer than the slit size the wavelike nature dominates and the influence on induced charge motion in the material making up the slit matters more. Particles in QM are not the same as classical point particles; there is probability for interactions at various locations. (Does it make intuitive sense? No. QM is not intuitive, and if you think you have an intuitive understanding, you're probably making a mistake or being naive or forgetting something!)

If you were shooting gamma rays which have less than atomic size wavelengths, then the photons would in effect pass straight through the slit as you would expect a classical point particle to do so.

At the core, this understanding is an experimentally derived result.

originally posted by: Arbitrageur
a reply to: Phantom423

originally posted by: greenreflections
According to this logic, photon as a particle won't 'fit' through the slit because it is not a particle yet.

"Particle" refers to the fact that it's "quantized" meaning it comes in packets. I'm not aware of experiments which show that this quantized nature fails to exist.

Yes it's there, but there are states which do not have determinate particle number, you could have 60% 0 photons 20% 1 photon and 20% 2 photons. I view photons as the 'basis function expansion' terms for the QFT wavefunction sort of.

a reply to: TEOTWAWKIAIFF

You're a guitar player! right on. And, I already know you have good taste in music....hmmmm...so we got a bass player, a guitarist. Any other members in this thread play anything. We need a drummer maybe a second guitarist or keyboardist. We can be like the in house ATS Ask Me Anything about Physics thread band.




Hey wheres everybody going? It would be a great idea! We could do covers where we change the lyrics to physics jargon.

(Wonderwall - Oasis )
...And maybeeeeeeee youre the Debye that makes meeeeeeeee. Cause after allllll.. I'm your Van Der Waaa-aaallll......

a reply to: BASSPLYR

1 1 2 3 5 8!

I am a physicist! I am an anarchist!
Don’t know what I need, but I know how to measure it!
I want to destroy the passer by
And IIIIIIIIIIIIIIII wanna beeeeeeeeeeeee anarchy!

[ETA: Did we pass the audition?]