A lot of my favorite sci-fi touches on quantum mechanics, and there are these huge discussions about it and I can't help but think that it's not portrayed in a realistic way but I don't know enough on the subject to dispute anything convincingly.

So I'm looking for a smart person to bounce some stuff off in an explain-it-like-I'm-a-freshman sort of way. Bear in mind that I'm a total layman about this stuff. Undergrad level, if that.

1) Quantum superposition. I heard it like this, a photon "knows" when it's being watched, and will change its state depending on whether it's observed.

My understanding is that our methods of observation inherently cause minor disturbances in what's being observed - like using flash photography. Photons aren't being sneaky or anything. Matter isn't actually in multiple configurations at once - it's just that we can't observe them with much precision, so we consider it "blurry" until we get a nice, close look.

2) Many Worlds interpretation. Are there actually multiple universes where things unfold differently? They brought up Schrodinger's Cat but I'm pretty sure that that whole thought experiment was intended to throw shade on Many Worlds - there's no box where a cat's possibly alive and possibly dead, it's either one or the other.

3) Can quantum entanglement lead to FTL communications or travel?

4) Black holes aren't really holes, are they? You can't throw an apple down one and it appear in some other universe, right? My understanding is the "hole" part isn't literally true, just a handy metaphor - stuff goes down, basically nothing* comes back out. But it's more like an extremely compressed star that warps space to such a degree that basically nothing* can escape once it gets close enough - it's less like a hole and more like a pit that no one can climb out of.

(* except hawking radiation)

5) Is our universe predictable from the onset - a person with full knowledge about it could correctly predict how it's going to look a billion years from now (a clockwork universe)? Or does the fuzzy nature of quantum physics allow it to go down unexpected roads to unforeseeable outcomes?

People think I don't know anything. But I am an applied physics major (undergrad) and have studied quantum mechanics post-grad. I am presently studying quantum computers. I hope to make this clear enough ... per Standard Theory (not Strings etc).

1. Quantum phenomena ... happens with a lot of quantum systems (usually tiny things) not just photons (light). There are lots of incorrect popular science explanations of physics in general and quantum mechanics in particular, that are technically wrong. You are one of many victims.

The actual "shut up and calculate" rather than Quantum Mysticism is correct according to experiment. If you have a photon or electron, heading for a slit ... you don't know anything until it is observed (aka measured). This doesn't require consciousness. A solar cell etc will do with a digital counter attached. So you have one particle, and if you have one or two slits between the emitter and the detector, you will record a single click. If your detector is local, you place it in any number of parallel places, and you may or may not get a click. If you send a lot (but not enormous number) of particles, and you set your detector at various places (if you have one slit), you get a regular statistical distribution, one-hump. But as long as the number of particles isn't too great, and if you have two slits, you get an interference pattern, not the statistical distribution you would naively suspect. Underline NAIVE. Ordinary statistics (Kolmogorov, not Bayes, not frequency count) assumes that each event is independent of each other. This assumption is valid, if you have one slit, not if you have two or more.

Now about pre-detection of the particles ... in effect, the second+ slit is acting as a crude detector. If you pre-detect a particle, with a slit, or by bouncing light off of it, you also create an interference pattern, an anti-interference pattern. This adds to the original interference pattern, cancelling it out, and you get the expected multi-slit ordinary statistics (multi-humped). There is no explanation for this, other than the mathematics matches the experiment. Quantum interpretation is like Oija Board stuff (see below). Basically what happens is that the assumption that events are independent, is experimentally wrong in many cases, hence the statistics consistent with the assumption that events are independent, is also wrong (as required by logical consistency).

"Superposition" ... isn't magical, it is trivial. One can have a musical sound, with more than one frequency, even two pure frequencies that are a perfect interval apart (harmony). When you hear this chord, you experience "superposition" in your ear (you have a classical analyzer in your head). Quantum systems can do this too. An atom has electrons around a nucleus. Usually the electrons are in a base state. If you irradiate the electrons with the precise frequency required (resonance), an electron in a base state, can be pushed to an excited state. But ... it is also possible to maintain a continuous irradiation, such that the electron stays in disequilibrium, between the two states. That is a "superposition" too. Think of each state as a tone, then the "superposition" is the adding of two tones into a complex wave to make a chord. But this is very unstable (hence it is hard to make a quantum computer). Moreover, the electron if it is in the excited state, is also unstable, and will re-emit the irradiation and the electron will return to the base state. Think of the excited state as balancing a pencil on your finger tip, with the eraser down. Unstable. Think of the "superposition" as balancing a pencil on your finger tip, with the point down. Very unstable. There are multiple physical realizations of "superposition", not just excited electrons in an atom.

2. There are multiple interpretations of quantum mechanics (including the simple experiment above) that all produce the same math. There is no means of telling which one is better (given Standard Theory). One of these is the Copenhagen Interpretation. Another is the Multiverse Interpretation. I will outline the Multiverse Interpretation for you. Consider our excited atom. When irradiated, there is a certain probability, that the electron will jump to a higher state. With the Multiverse ... if it was 50/50 odds, then in an environment where this is possible, half of the atoms will have excited electrons and half will not. You can't predict individually, if a given atom will be excited or not, you just have statistics on the total population. Going on, this interpretation says, that one half of the atoms exist in a universe where the electrons are in a base state, and one half of the atoms exist in a (different parallel)universe where the electrons are in an excited state. And of course these two universes interact (because statistical independence can't be assumed). This interaction is an "entanglement" which can happen to whatever degree in a large population, but even between too individual atoms under proper conditions. For example, in a hydrogen molecule, two protons share two electrons. Electrons are identical to each other, as are the protons to each other. No experiment can tell which is which proton, and which original electron (prior to molecular bonding) belongs to which proton. We lose information about which proton is which, and which paired electron is which, when the bond forms (quantum information theory). Of course if we heat the hydrogen molecule so it break apart, the resulting to hydrogen atoms are as before, but we don't know which proton is which, or if it got the same electron it started with. Any atom to atom bonding involves "entanglement", water molecules for instance. With water the two hydrogen electrons are shared with the oxygen atom, and the outermost electrons of the oxygen atoms are shared with the hydrogen atoms.

3. How does "entanglement" effect statistics? Even more weird than "superposition". In "entanglement" there can be certain required logical relationships between the states. For example, if you have a pair of photons, created from the same event, then they are "entangled". If you keep the isolated (unmeasured) they retain their "entanglement" no matter how far apart you put them, even many miles apart). When you measure one of these photons, it will be in state A or state B. If the logical relationship at creation was that they have to be in the same state, then upon measuring either photon at either location, both will be state A or both will be state B. Which is to say, the events are not independent (see first paragraph).

The logical relationship is constant, no matter where you go, or how long you wait before measuring. Say you have a pair of magical loaded dice. Such that no matter which dot pattern comes up on one die, the same pattern must come up on the other die. But you don't have CONTROL over the outcome of an individual die. This lack of control is crucial. If you could control the outcome, then you could use this (per quantum "entanglement") to do FLC. The unavoidable statistical nature of quantum mechanics (and nature) prevents this.

There is another phenomena, quantum teleportation. Basically you can clone, but not copy, a quantum bit. A qubit (quantum bit) is the simplest form of a quantum system (say an electron that has spin up or spin down and in-between). A given electron is in state A. Can I make a copy of that electron (using another electron) in the same state A? The answer is no, because the act of doing that would change the state of the original electron (see first paragraph). It is possible for something as simple a a qubit to be cloned. I can electronically (or photogenically if using photons instead) cause an electron/photon at the far end, assume state A ... but in effect this randomizes the original state of the electron/photon. This of course is possible precisely because aside from state, all electrons are just alike, all photons are just alike. So unless you can become an elementary particle, you can't teleport. And even if you could, it wouldn't be you, it would be a clone (you would be like the mess that a Star Trek transporter makes of a person if malfunctioning).

4. Black Holes ... are predicted by General Relativity, and are now widely detected from a few solar masses in size up to billions of solar masses. They are a space-time anomaly (space and time are very warped), they aren't holes. Nobody knows experimentally what happens inside of one. It seems to be impossible even in theory (see speculative White Holes). If you are a hydrogen atom, in orbit around a Black Hole, you gradually are drawn closer and closer. In observer time, it takes forever for the hydrogen atom to reach the even horizon (the dividing line between what can be observed and what cannot be observed). In local time, per theory, it takes a finite time to reach the even horizon (so don't try this yourself). As the hydrogen atom gets closer and closer to the event horizon, the spectrum of an excited atom gets more and more distorted. The gravitational read shift. The spectrum of the excited hydrogen atom is like a clock. As it gets closer, time is slower (relative to a distant observer aka observer time) ... so the spectrum gets longer and longer (redder for visible light). Not much is known about the event horizon, and nothing is known about the interior. Per reasonable theory (Hawking Radiation), at the event horizon you get a multiverse thing happening. The vacuum of empty space isn't empty, it is teaming with virtual particles (mostly electron/positron pairs, positrons are anti-electrons) that appear and disappear spontaneously (see Casimir Effect). Imagine an electron/positron pair appearing, but one of the two particles, slips across the event horizon, never to be seen again. What we would detect (if we were crazy enough to get that close) would be a sparse radiation of electrons/positrons emitting toward us. The greater the distortion (closer to the event horizon) the spectrum of emitted matter/anti-matter gets heavier. You start detecting protons/anti-protons etc. Over a very long time, this Hawking Radiation will steal mass from the Black Hole and it will shrink until it disappears entirely. What then of the interior? Why call it a Black Hole ... because any light falling into it disappears (a perfect absorber). Ironically, the classical equivalent, a "black body" is what led to the discovery of quantum mechanics in the first place.

5. Classical mechanics says, perfect initial knowledge, absent "chaos" aka turbulence, will lead to perfect prediction. But most states of matter in the universe are turbulent. Non-chaotic situations arise only in carefully controlled experiments. Logically, if something is perfectly controlled, then it is perfectly predictable. So prediction is a mirage, even in classical mechanics. In quantum mechanics, which is more real than classical mechanics (which arises from quantum mechanics when there is too much mutual interference) you can't predict the state of an individual electron or photon or atom, let alone a macroscopic mass-energy.

6. It is possible to observe actual quantum phenomena with simple polarizing films/camera filters.

I love to do this myself. Different arrangements are non-logical (to the naive view).