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In physics, do all particles have a particle-wave duality? And if so, what determines whether they behave as a wave, or become a one-dimensional point in space? I'm familiar with the electron double slit experiment, and it's my understanding that when it's not observed, an electron acts as a wave. But when it's looked at, it acts like a single particle. How about hadrons, like protons and neutrons, that are made of quarks. Even though the are composite objects, can they also behave as waves, while containing their constituents? If the act of being observed has no influence on particle-wave duality, then what causes this property? And how does it ultimately effect our perception of reality?

There's no simple uncontroversial answer to your question, but perhaps a couple of points will be at least somewhat helpful. "Wave-particle duality" is ultimately too narrow a way to think about what you're interested in. The things that get described as illustrating "wave-particle duality" are special cases of the phenomenon of quantum interference, and that, in turn, is a manifestation of the fact that quantum states obey a superposition principle . At the end of the day, there's no substitute for thinking of this mathematically, but I'll do my best to avoid that here. You probably know at least a bit about polarization. If we hold a polarizing filter (e.g., a lens from good sunglasses) up to a light source, the light that gets past it is polarized along a common axis—let's say the vertical axis. In principle, with the right kind of light source, we can turn the intensity down so that only one photon is emitted at a time. If such a photon passes the filter, it will hit a screen in one spot—like a...

I once asked a physics Q&A site, "Is physical reality possible without an observer?" They told me it was to broad of a question, and I got no answer. But from a philosophical or metaphysical stand point, is there an answer? I'm aware of the Copenhagen Interpretation of QM, and it's requirement of observation and measurement for existence of macroscopic structure to be. If, in philosophy, an observer is needed, then how did galaxies, stars, planets, and the Universe itself, come into being? Also, can other organisms other than human beings, make a measurement, and thereby effect their ambient reality? Sun Flowers, for instance, follow the moving sun as it traverses across the sky, via heliotropism. Can this be considered making a measurement?

You're quite right to be skeptical of the idea that physical reality needs observers to exist. But very few people who work in foundations of quantum mechanics would disagree. Bohr never claimed otherwise. What he insisted is that in describing quantum experiments, we have no choice but to appeal to classical concepts. There's room to argue about what that means, but nothing I've ever read by Bohr suggests that measurements are necessary for the very existence of physical systems. The same is even more clearly true of Bohmian "pilot-wave" interpretations. Bohmians claim that there really are particles that really have positions and trajectories---whether or not anyone makes measurements. It's just that the details of these trajectories aren't accessible to us. Everettian ("many-worlds") accounts of quantum theory likewise don't hold that the existence of physical reality depends on measurement. It's true that "branching" in Everettian quantum mechanics has a connection with measurement, but this is...

This is probably a foolish question but I'm bored and I think you get paid for this, a short answer would not offend me nor would none at all. Can you make any kind of judgment about a person by the look in their eyes, I'm not sure judgment is the right word. Iv seen people who I could tell had been through a lot and been right, coincidence maybe but I'm not sure maybe its hormones or something. Perhaps you've spent some time thinking about it if so please share if not please share anyway.PS you guys are amazing and I thank you for all the answered questions, I never thought I'd get an answer to one let alone all of them cept for one but I understand why it wasn't answered. I don't know what you get paid but its not enough

As it turns out, we don't get paid. One reason is that, as you may have noticed, there's no charge to ask a question and there's no tip jar. ;-) On to the question. It's an empirical question; it depends on how our minds and bodies actually work. But it's pretty safe to say that the answer is yes: sometimes you can tell things about a person by the look in their eyes. It's far from perfect and not always reliable, but there's no completely reliable way to know what a person's state of mind is, so that's not a special problem for this case. In fact, there's not much mystery here from the point of view of common sense. Most of us are at least tolerably good at reading facial expressions. And as for the eyes, they're part of the expression. A fake smile won't give you crow's feet; a genuine smile raises the cheeks and makes the corners of the eyes crinkle. We can learn to tell the difference. That's just one example. Of course, it's not always so simple. A person's facial expression (eyes especially) may...

Does our mind alter our perception of taste from the way things look and/or previous experiences?

The answer certainly seems to be yes. One example: learning to like something you didn't like at first. (Olives, beer, strong cheese…) Taste isn't the only sense modality that's subject to these shifts. Most of us, I'd guess, have found that people sometimes come to look different to us as we get to know them well, for example. As we think about our earlier reactions to some musicians and some music, we may be struck by how different the same piece sounds to us now than it once did. Obviously there are lots of interesting questions we could ask here. It seems plausible that sometimes these shifts are a matter of learning to notice things we didn't focus on at first. But as others have pointed out, this phenomenon raises more peculiarly philosophical questions. Daniel Dennett considers a pair of possibilities that seem maddeningly hard to disentangle: one might say: I used to like parsnips, but they taste different to me now. Or one might say: parsnips taste the same to me as they always did, but I...

Are humans capable of feeling extreme physical pleasure as intense as extreme physical pain? If that is the case what ethical beliefs would we have to change if we wanted to maximize the occurrence of extreme physical pleasure in a way that accorded with a utilitarian hedonistic ethical system?

It might be worth starting with a qualifier: for many utilitarians, "pleasure" is too simple a notion to capture what they think we should maximize. "Happiness " might be better, and "well-being" better yet. But set that aside and suppose we can make do with the word "pleasure." On the first question – whether we can feel pleasure as intense as the pain we're capable of – it's hard to say. We're obviously capable of short bursts of intense pleasure, but whether they're as intense as some kinds of pain is hard to judge. More important, perhaps, even if the intensity of our greatest pleasures matches the intensity of our worst pains, pain seems able to go on for a lot longer; if we factor duration into the accounting, the answer seems to be no. But suppose otherwise. Even if we're utilitarians, the goal is to maximize total pleasure; trying to maximize intense pleasure might not be the best way to do that. We might very well get far more bang for our buck by trying to alleviate suffering or...

Would the idea of 3 dimensional space be possible without vision?

The answer seems pretty clearly to be yes. Touch and hearing both convey information about dimension. Think, for example, about the fact that a sound can be above you, or in front, or two the side. Or think of how you could tell that object A is taller than object B, but object B is wider than object A just by using your sense of touch. If you're interested, here's a link to a video about a remarkable Turkish painter, blind from birth but able to convey subtle information about perspective.

If you look at the leaves of a tree, they are seemingly randomly arranged. We call it chaos. If you take 100 pennies and arrange them on a flat surface in rows and columns of 10 it's called order. We assign the label chaos to something that occurs naturally and has done so for billions of years. Wouldn't that occurrence be considered order if it had been there a long, long time and the human species and our perceptions are very new in comparison?

I'm not sure that whether something occurs "naturally" nor whether it's been thus for a long time is the issue here. Nature gives us many examples of things that are very orderly and not "chaotic" or "random" at all. Crystal structure is an obvious example. So is the periodic table. And things with human origins can display a lot of randomness. Spin a roulette wheel a bunch of times and try to predict the outcomes. A bit too simply, there are cases -- old and new, natural and human-made -- where we can make very accurate predictions about what comes next, so to speak, on the basis of what's come before. And there are other cases where our predictions will be (so to speak) no better than tossing a coin. I think that's what lies behind the distinction you're making, and there are branches of science and mathematics that have lots to say about the matter. (One particularly relevant field is information theory.) Of course, there can be hidden order where there is apparent chaos, and there can be...

Is it possible to look at anything without labeling it and to simply look at it as it just Is?

It's pretty clearly possible to look without verbal labeling, since animals and infants do that. But whether we can just look at something 'as it is' isn't so clear. One obvious problem: our sensory systems (brain included) do a lot of processing of the information they take in, and this starts early in the process - long before we get to anything over which we have conscious influence. So if that doesn't fit the "seeing as it is" bill, we're already out of luck. But there's another problem: what would count? My cell phone sits beside me. What would it mean to look at it as it is? Among other things, it is a cell phone. If I don't recognize that, there's an obvious sense in which I don't see it as it is - or at least, not for what it is. But even if we stick to the intrinsic characteristics of the thing apart from its uses, which of the countless many count? There are far more physical facts about my cell phone than my beleaguered brain could ever cope with. Not only that; many of the...

All the empirical objects that I perceive around me are structures of sensations: sensations of color, tactile sensations such as hot and cold, hard and soft, and rough and smooth. But sensations are supposedly manufactured in the brain, out of neural signals delivered from the sense organs. This leads to two questions: how do they get out there, into the real world; and if sensations are unreal --- they exist only as long as they are perceived --- and the real world is composed of sensations, is the real world really real?

I think the best place to begin is with the first sentence: "All the empirical objects that I perceive around me are structures of sensations." I think this confuses two things. The objects we perceive are things like tables, chairs, tin nickels and left-handed paper-hangers. And none of those things are structures of sensations. Now it may be that the way we perceive these things is by having various sensations, and it's also true that in some sense the sensations are manufactured in the brain, brought about with the causal assistance of the paper-hangers and such. But the machinery of perception isn't the same as what's perceived. More generally, it's no surprise that we perceive things by way of stuff going on in our brains. But that stuff isn't what we see; it's what makes seeing possible. So yes: the real world really is real (last time I checked). It's not composed of sensations, though sensations may be among the many things that make up the world entire.

Am I correct in thinking that vibrations in the air are just one cause of sound, and that really sounds are what are experienced? So for example under this definition of sound, ringing in the ears is included. Equally then, that sights can be caused by light bouncing off objects but also by the imagination? Can I draw the conclusion then that there are an equal number of sounds/sights/tastes/smells/feelings that have ever existed, than have ever been seen/heard/tasted/smelled/felt? The tree that falls in the woods with no one in it makes no sound at all (but plenty of vibrations)?

The issue here seems to be verbal. It's not clear that ordinary language has a settled answer to the question whether "sound" refers to the vibration in the air, or to the experience that the vibrations cause. If we fix on the former, then there have been plenty of sounds that never led to any experiences. If we fix on the latter, then sounds and experiences of a certain sort are one and the same thing. But there's no deep fact about which is the "right" way to think of it. Something else worth keeping in mind: language doesn't map onto the world in any simple, direct way, and in particular we need to be careful about letting the fact that we have the noun "sound" fool us into thinking that there is some thing in the world -- a sound -- whose location (in the head? in the landscape?...) needs to be sorted out.