Atoms

Argh! Am I the only person who's never met a big-name scientist?

As far as colour goes, I believe you are correct. My understanding is that "colour" is a meaningless concept at the level of individual atoms, because they are smaller than the wavelengths of light that our eyes interpret as colour. So, if you want to get technical about it, nothing really has colour. What things have are specific properties that reflect the wavelengths of light that we perceive as colour.Now, whether or not these properties are inherent in individual atoms, I don't know. But even if they are, you won't see their "colour" until you have a large enough group of them to reflect the necessary light. In a sense, you might say that a large enough group of atoms has colour, but a single atom does not.Of course, I'm no expert. This is all half-remembered information from years ago. Somebody can correct me if anything I've said here is wrong.

Heh, indeed.I'm starting to see a pattern here. You've met Richard Feynman, who is now dead. Brad has met Carl Sagan, who is now dead. Both of you stay the hell away from Stephen Hawking, you hear me?

Hi Melchior,Thanks for your reply. I'd just like to clarify a few things, if that's ok.As I understand it, when light encounters matter it gets scattered, with some frequencies being absorbed and others being reflected (depending on the properties of the matter in question), thereby determining what colour we see. Is this correct, so far? I always thought that individual atoms were too small to be detectable by any wavelength visible to humans. I'm sure I remember reading something to the effect of: "It would be like trying to take a photograph of a grain of sand by firing cannonballs at it." Something like that, anyway. It's possible, though, that what I read was about something completely different; it was years ago.I seem to recall that "photos" have been taken at the atomic level, using electrons instead of photons (I think it was electrons). Is this correct? Are there any true photographs of atoms (using actual visible light)? It doesn't have to be one single atom; just anything that shows actual atomic structure. If so, do you have a link? I'd love to see. Just to be sure I understand correctly, when you say that atoms "have" colour, do you simply mean that the material properties which cause a given element to reflect the light that my eyes interpret as a certain colour are contained within each of the element's individual atoms?Or are you saying that each of its individual atoms actually reflects light in exactly the same way as does the whole? That if we had an ordinary photographic camera, with an atomic-level magnification, the individual atoms would actually show up on the photographs as having colour? If so, would their colour be the same as that of the macroscopic whole (assuming, for the sake of argument, 100% purity of the element in the overall grouping)?

Greetings Happy! Am I right in understanding that electrons don't so much "shift" orbits as leap orbits, literally jumping, instantaneously, from one orbit to another? Yes, this is what I find confusing. I didn't think an atom could emit a photon with a wavelength in the visible part of the spectrum. If this is correct, then how can a single atom even be directly seen, much less show colour?I understand that each atom possesses the properties that result in what we call "colour," but I'm not sure I understand how an individual atom can actually display colour. I'd have thought it would require a collection of atoms comparable in size to a visible wavelength of light, like (from the aforementioned example) a large clump of sand similar in size to at least one cannonball.Perhaps I'm looking at this the wrong way. Is it possible that I'm getting confused by particle/wave duality?

Hi Coragyps, Ah, so individual atoms are too small to be able to be imaged by any wavelength visible to humans. Ok, thanks for the correction. So, each atom (in a neon light) emits a photon with a wavelength far bigger than the atom itself? I'm having a hard time picturing this. Is this analogous to the grain of sand "emitting" a cannonball? Or are we concerned not so much with the size of the photon itself, but that of its wavelength? And are they the same thing or different?Wave/particle duality still ties me up in knots, I'm afraid. Is the size of a photon equal to the size of its wavelength? This is probably what I was thinking of. Thanks for the link, Coragyps. What I'm having trouble getting my head around is how an atom can reflect/emit a wavelength of light significantly larger than itself.I realize, of course, that my understanding being based on such a simplified view of particle physics as the cannonball analogy probably isn't helping. Perhaps likening the scenario to a grain of sand being bombarded by cannonballs is too limiting, as the cannonballs are too "particle-like" an analogy for light, which is both particle-like and wave-like. Heh, no problem. My questions regarding the properties of "colour" in individual atoms are all based on half-remembered material that I read years ago, so I know the feeling.

Hi Melchior, So if we could actually photograph individual atoms, they would display colour? Yes, I understand that the properties of colour are inherent in each atom. What I'm not clear on is whether or not those properties actually manifest themselves as colour, in the case of a single atom which is smaller than the wavelength of the colour itself.I realize that the property of colour is there, in the atom. Are you saying, then, that this property, even in a single atom, is exerted in the way that we're familiar with (i.e. as visible colour)?Sorry for being so repetitive. I'm just trying to make sure I understand correctly. You seem to be saying that if we could magnify far enough to look at a single atom, we would actually see its colour. Is this correct?

Hi sidelined, I'm not sure I understand. I thought that "colour" was simply how our eyes interpret a certain range of frequencies within the visible portion of the spectrum; is this what you mean by the photons themselves being coloured? Are you simply referring to the wavelength of the light in question?Something else...I just realized that I'm using the words "frequency" and "wavelength" interchangeably. Are they, in fact, the same thing, in this context?I've never given it a great deal of thought but I've always assumed that "wavelength" refers to...well...the length of a given wave, while "frequency," I would guess, refers to the number of waves. I can see how they may be used in similar contexts, but perhaps there's a subtle difference that's contributing to my confusion. Hmm...so an individual atom won't display colour? Melchior seems to be saying that it will (I think). Or did I misunderstand you? Perhaps you meant that the nucleus, specifically, will not show colour, but the overall atom (nucleus and electron/s) will?What I'm really having trouble with is how a single atom can show colour when the necessary wavelengths are so much larger. I keep falling back (no doubt due to my layman's understanding of particle physics) on the analogy of the cannonballs and the grain of sand. Is this a mistake on my part? Perhaps it's giving me an inaccurate impression.Just to clear it up in my mind, how does a photon compare in size, roughly, to an atom. Is the grain of sand/cannonball analogy (representing atom/photon, respectively) anything close to reality?Or perhaps the particle sizes are comparable and it is specifically the wavelength of the light that is larger than the atom? If this is the case then I may simply be having difficulty with the nature of particle/wave duality. Admittedly, I've never had a particularly firm grasp of it.Thanks for the help, sidelined.

Hi Melchior, Hmm...ok, at this point, I think I must be reading somebody wrong. You seem to be saying, here, that an individual atom will display colour, and sidelined seems to be saying, in post 54, that it won't. I hope I'm not misrepresenting either of your positions. I'm not trying to put words in anyone's mouth; I am genuinely reading these posts that way. You may both be telling me the same thing, but I'm afraid I see a conflict here. My apologies. Oh no, I understand that individual photons, atoms, etc are far too small to discern with the naked eye. I was assuming, for the sake of argument, that we have a way of magnifying far enough to allow us to look directly at the atoms and see if they display colour. Sorry for my lack of clarity. Yes, this is what I assumed for the purpose of my question. That is, hypothetically, if we were able to magnify far enough to see an individual atom, would it display colour?Also, I should clarify specifically what we're magnifying. I'm not talking about magnifying to the point where you can see the individual atoms within a group, I am assuming that we have one single atom isolated somehow (don't ask me how...magnetic field within a vacuum? ) and we are zooming in on that.So, I suppose, in a nutshell...Premise: We have an atom, isolated from all others, in a total vacuum. We have technology capable of magnifying down to the atomic level. We zoom right in and focus on the atom.Question: Do we see its colour? I think I must be getting confused over the particle/wave nature of light. As I said to sidelined, I am proceeding from an amateur's understanding of particle physics. The grain of sand/cannonball analogy may be giving me more grief than assistance.I keep picturing a grain of sand being struck by a cannonball and returning a cannonball. Not only is this a simplified view, but it also fails to take the wave-like nature of light into account. That may be part of my problem; perhaps I'm thinking too much in terms of its particle-like properties.Thanks again, Melchior. I appreciate your help with this.

Hi Melchior, Just to clarify (although, I do think you understood my meaning), I was speaking of isolation only from other atoms, not from photons, as I assumed that, in order to see it, you would need a light source. Mmm...ok, I think I'm getting you. So, in essence, all of the properties of the colour are present in the individually emitted photon? Alright, this is what I suspected.I'm still not sure that I'm sufficiently communicating my question, though. I'm not so much concerned with whether or not our eyes are capable of detecting the photon, as whether or not its colour is physically manifested in exactly the same way, even though it is too small for us to see.For instance, if we had a microscope that could take the image and "blow it up" to a size that we could see, would the image show the atom's colour? That is, if we were able to simply magnify an atom as we can, say, a microscopic organism.As I re-read my question, I'm starting to think that I'm overlooking something. I may be running into problems by trying to simply magnify things to a viewable size, without considering what physically happens during optical magnification.I was trying to avoid the necessity of multiplying the photons, by just detecting one and then "blowing the picture up." However, it now occurs to me that multiplying the photons is precisely what "blowing the picture up" does.Any way you cut it, I would have to replicate the photon before I could create any kind of visual representation of it large enough for my eyes to see, wouldn't I? I mean, even if I had a live view of it, magnified millions of times on a monitor, I still wouldn't actually be seeing the photon; I'd be seeing millions of photons, codified by the data received from the single photon, and organized in such a way as to visually represent it on the screen.Incidentally, you said, in your example, that our brain would see a coloured dot if we had a machine that could detect one photon and relay ten of the same type to our eyes. I have to ask; is this just a figure you pulled out of the air for the purpose of describing the machine's function, or did you actually mean to say that our eyes are capable of discerning a point of light comprised of a mere ten photons?I must say, if you meant the latter, I am very surprised; I would never have thought that our eyes were that sensitive. In fact, I would have guessed that it'd take thousands of photons to create light significantly large (and intense) enough for us to see. I'm quite amazed by the idea that we are able to see a group of just ten, if indeed this is what you meant. Ah, I see. Ok, that makes sense. Hmm...alright, so the term "wavelength" isn't actually the measure of the physical length of a wave? Once again, my layman's understanding rears its ugly head, it seems.I wasn't aware that it had anything to do with the shifting of fields, as such. I thought that a "wave" was simply a displacement that travels through a medium. Or are you saying that fields, too, can act as mediums for waves?I'm probably even less familiar with waves than I am with particles. For some reason, I generally find it easier to visualize the transfer of particles than I do of waves. Perhaps it's just because I'm not clear on their specific properties.I keep seeing old diagrams, in my head. They would show wavy lines describing "crests" and "troughs," as I recall. And I thought that frequency and wavelength were illustrated by showing the range of wave configurations; from a few long drawn-out waves, to many compressed waves squeezed tightly together. This, however, may simply be a way of illustrating the concept, and not indicative of their actual physical configuration. Yes, that sounds right (not that I think anything you've said is wrong, it's just that this at least sounds familiar to me). Oh, ok. I didn't know that.Again, I have difficulty with particle/wave duality, so I'm not sure how light's particle-like properties relate to its wave-like properties. Is the size of a light-wave equivalent to that of a photon (which I assume are all the same size, but I may be wrong )? And how does this compare, in size, to an atom (approximately)? Is the grain of sand/cannonball analogy accurate, in terms of the relative sizes of atoms/photons, respectively?By the way, thanks for the tuition, Melchior. This is an interesting topic, and I appreciate your help in understanding.

Hi sidelined, Ok, cool. It appears, then, that I was on the right track, although I didn't know the specific figures.Also, thanks for the link. A couple of the terms went over my head but it was interesting, none the less.I enjoyed the application of "dimensions" in the explanation, even if I didn't entirely understand it. In fact, I think I've read something similar to this before; an article discussing the "dimensionality of colour," or something to that effect. I wish I could remember where. Ok, if I'm reading you correctly, this is what I was thinking.Something I'm not sure I understand, though, is the difference between visible light with a wavelength of a certain colour and visible light with a wavelength stretched or compressed (that is, red-shifted or blue-shifted) to a certain colour. For example, what is the difference, physically, between light-waves that we see as "red" and light-waves that are Doppler-shifted into the red?Am I correct in thinking that "red-shifted" does not actually mean "appears red in colour"? That is, the colour displayed by a given light (at least, as far as our eyes are concerned) is not actually related to its red or blue shift, correct?As I understand it, so called "red-shift" and "blue-shift" are opposite extremes of the Doppler Effect on light. However, these shifts in "colour" don't actually manifest as visible red/blue light; they are determined by separating a light's component colours by diffracting it through a prism, and analysing its spectral lines. Is this correct?If so, then what is it that's different about the wavelengths (or frequencies...sorry, I'm still not sure which one applies) that we see as visible colours? For example, what is the difference between light-waves with a wavelength of 700 nanometres emitted from a stationary source, and light-waves stretched to 700 nanometres emitted from a receding source?Presumably, the former would actually appear red to our eyes, while the latter would not (at least, not necessarily). But why? Physically, what is the difference between the two? So do nuclei actually contribute any of the properties that electrons emit as visible colour, or are said properties a sole product of the electrons?Actually, I think I'm missing something here. I'm pretty sure that the nucleus does indeed have an effect on the overall atom's colour. I think I've applied your statement the wrong way. I realize that you weren't saying the nucleus has nothing to do with an atom's colour (just that it isn't responsible for the actual emission of light). However, if the nucleus doesn't interact with the light being received/released, just how does it contribute to the properties of visible colour in an atom? Indeed. And this is something I've always struggled with. Lam asked me, once, if I understand wave/particle duality, and the short answer is; I understand the principle that it refers to, but I most certainly do not "understand it." Oh, I know. I'm familiar with quite a number of ideas that stretch my mind to its limits (and beyond ). One of my most beloved pastimes is researching concepts that I have little to no chance of ever understanding...*cough*...well, it's worth a try. Yes, I am aware of the degree of empty space within atoms. This is something else that has always interested me; the notion that apparently "solid" matter is nothing of the sort.As I understand it, neutronic matter is the densest substance known. In fact, I've read that it actually contains no empty space. But is this even possible, given that neutrons themselves are composed of quarks? I can understand there being little empty space, but none at all? Or perhaps it simply means that there is no distance between the neutrons; that they are actually pressed together (that is, in physical contact, literally touching each other)?Actually, I recently read of a (possibly) new type of star, composed entirely of quarks. I'm not sure how new (or old) this information is, but if it's true, would it constitute a substance even denser than that of a neutron star? That's cool. Perhaps Melchior will know. Believe me, I know how it feels to stray from your area of expertise. Actually, as I don't have an area of expertise, I guess I don't really know how it feels.Being little more than a curious scientific layman, I come across many things that I don't entirely understand. But I think I manage to get my head around most concepts to at least some degree, providing they don't require any deep familiarity with the mathematical theory behind them. Well, I think you're doing a good job already. Thanks for your help, too. It is much appreciated.

Hi Coragyps, Really? Well, there you go. Another of my misunderstandings corrected.So the reason that distant galaxies don't actually appear red in telescopes and photographs is simply because their red-shift isn't significantly large enough to show up to a degree that we can identify as visibly "red"? And here I was thinking there is something fundamentally different about visible red and red-shift. Thanks for the correction. So the nucleus doesn't have any direct interaction, all it does is balance the atom's overall electrical charge? Is it true, then, to say that as far as electromagnetic interaction goes, there is no difference between an element and any of its isotopes?Something else which occurs to me is that if it is solely the electrons that interact with the light that we see, what are the visual properties of substances which are ionized and have their electrons stripped away?Or perhaps neutronic matter itself is a better example. If it contains only neutrons, does it directly interact with light? So nuclei do have some direct electromagnetic activity (despite x-rays being, of course, invisible to our eyes)? Ok, thanks for clearing that up. Well, I already knew that light has no memory; I meant thanks for the rest of it. Ah, ok. Thanks for the confirmation. Yes, that was one of my first thoughts. As neutrons themselves are comprised of quarks, it could conceivably be very difficult to tell quark and neutron stars apart. I'm sure they'll come up with something, but I can't imagine what. Perhaps we've already observed quark stars which we've unwittingly assumed were neutron stars. Who knows? I certainly don't. Heh, not unless you're the strongest person in the universe...or you just have a very, very small scoop. Oh, and also assuming, of course, that you don't mind having your body gravitationally crushed into a volume the size of a hydrogen atom.

Hi Melchior, To be honest, I suspected this might be the case. From what I understand, things at this level tend to be kind of "fuzzy," and I had a feeling that the unique properties of light wouldn't make clear, precise definitions any easier. No size at all? I didn't know that. I knew that photons were massless (hence their ability to travel at the speed of light) but I had no idea they had no volume.This is a concept I have trouble getting my mind around. Not zero size, in and of itself, but how any extant body can be said to have zero size. Doesn't this, in some sense, negate its very existence? I've always wondered how point-like particles can truly be "point-like" (in that they have no volume, whatsoever) and still be said to "exist" in any meaningful way.When you say "zero volume," do you actually mean zero in the strict, mathematical sense, or are you talking about the universe's lower limits of quantized space? Perhaps you mean that a photon's size is on the level of the Planck scale? I'm not trying to put words in your mouth, by the way; I'm just trying to clarify your meaning. So is a light-wave not actually a "wave" in the classical sense (that is, in the way that sound, for instance, is a wave)? I've always wondered exactly how it is that waves of light can travel through empty space.For the most part, I just assumed that it's because light also has a particle-like nature that allows it to do this. Unfortunately, though, this never really made it any clearer to me, as I still can't see how the word "wave" can have any real meaning without a medium through which to propagate. That's ok. I'm learning plenty. I understand this better now than I did before, so I'm heading in the right direction. Thanks again for your help. Yes, which is a whole new problem altogether. Fields are another concept that I've never completely grasped. Oh I know what fields are, but I don't really know what they are...if you get my meaning.I'm not even sure if all "fields" are the same type of physical phenomenon. I understand a "gravitational field," for example, to be a curvature of space-time. But are all fields the same? Is a magnetic field, for instance, also a warpage of space-time geometry? I've only ever seen this explanation related to gravity. I've always likened the concept of a field to that of a "force," but that still doesn't explain what a field actually is, if that makes sense.

Hi Loudmouth, Yes, I understand this. But just to clarify (as I've already uncovered several misunderstandings that I had), am I right in thinking that, in reality, there is really only the electromagnetic spectrum, and what we call "light" is simply a thin strip of wavelengths somewhere near the centre, between both extremes? Am I also right in thinking that the entire spectrum shares the dual particle/wave nature of visible light? Now, there's an interesting thought; I'd never considered that. I assume you mean the visible light coming from outside the ship? That is, the light that is massively blue-shifted from all approaching sources? It determines the electrons' excited states as well? Ah, I knew there had to be more to it than determining the number of electrons. Thank you; I understand. Heh, it's ok. It basically just confirms what I already thought.I realize that, technically, we don't actually see anything we look at; only the light it emits/reflects. I was just wondering if it was possible (at least, in principle) to "see" an atom in the same sense that we "see" regular, macroscopic bodies.My thinking was that if we could somehow isolate a single atom (say, in a magnetic field, in a perfect vacuum), perhaps it would be possible to simply shine a light source on it as we do to "see" any regular object.Of course, I have my doubts as to whether or not it's quite that simple in the case of a single atom. For one thing, an atom is obviously far too small to see with the unaided eye, and as I said in another post, we would still require some means of "enlarging the image," which rather defeats the purpose of trying to see what the atom "actually looks like," doesn't it?

Hi sidelined, Yes, I understand that. What I was asking was, in a nutshell, is there a difference between red (visibly red) light and red-shifted light?For example, is there any difference between the light received from, say, a red giant sitting stationary, relative to the Earth, and a star receding from the Earth, and hence heavily red-shifted? If we assume that both are seen from Earth to have a similar wavelength (say, the red giant actually emits light at close to 700nm, while the receding star emits light of a shorter wavelength which is, however, measured as almost 700 nm on the Earth, due to its recession), is there any physical difference between them? Will they both "look red" from the Earth?Or to put it another way, would there be any way to determine which was which, or if there was indeed any difference at all, based purely of their wavelengths? Would there be any way to tell which was actually emitted at 700 nm and which was merely shifted to 700 nm?Thanks for the link, too. I've been there before but not since discussing this. I might try the "Light and Vision" section and see what I can find. Thanks again, sidelined.