A room full of light is ‘bright’ because the light contains so much information. And: it seems amazing that visible light is so faithful (non-noisy) when you think of it as a wave propagating in all directions; only a particle at the moment of observation.
I find that your bright room-observation and an analogy with low-light photography almost helps me grasp how come the world seems classical despite its quantum “underwear”:
Think of a (digital) photograph taken in very low light. Something like this.
Think of being in a pitch black room, and imagine your eyes are perfectly sensitive. You have a flashlight pointed away from you.
Now imagine the flashlight is very dim: it only sends one photon every few seconds, by moving one of its electrons; the electric field propagates at c as a spherical wavefront to “notify the universe” of the change. Whenever this front passes through another electron (say, of the wall before you), it may be absorbed. If it’s not absorbed, the electron does nothing (in a way, it doesn’t care that the first electron changed position). However, if it is absorbed (the two electrons exchanged a photon), then the absorbing electron now changes position to conform to the new information; doing so starts another wave-front communicating this information. Note that this second wave-front is not just going back, it’s still a spherical front starting from the wall electron. Again it starts propagating through space until it hits another electron. Suppose this last electron is used by your eye as a detector. Then you just noticed a tiny “flash” of light somewhere in your vision field.
Note that the two absorptions happen (until now) randomly. If you use just that flashlight you’ll only see random flashes in the room. More precisely, in the many-worlds interpretations, from a single train of emission-absorption-reemission-detection “events”, each you in every world will see the tiny flash in random parts of their vision field. This is both because different wall electrons would have done the absorption-reemission, and because of different electrons in your eyes would do the detection. You can extend this metaphor a bit more: in worlds where the re-emitted photon didn’t hit your eye, but (say) another electron deeper in the wall, that world’s version of you won’t notice anything. (The absorption-reemission chain will just bounce electrons and nuclei randomly throughout the wall, which just means heat.)
OK, here’s the “brightness” part: even though the absorption-reemission electron is randomly chosen by each world, not all of them are equally likely to be chosen. The wave-functions of the particles, and the interactions of those wave-functions as given by QM equations, cause the distribution of “picks” to have a certain “shape”.
Imagine that you take your flash-light and you increase its brightness; say it sends 10, then 100, then a million photons at the same time. You’ll start seeing several flashes, from random positions in your field of vision. (Each of you in the many-worlds will see the flashes coming from different places.) But the wave-function says how likely it is that you’ll see flashes from different places: even if each version of you sees different flashes, each of them will see more flashes coming from bright (white) objects than from dark (black) objects. As a result, you’ll see a grainy image of room in all worlds, even though a different one (that is, with the grain positioned differently) in each. The more photons your flashlight sends, the more “smooth” your image will be, converging on the “shape” of the wave-function. The image above shows a noisy image obtained in low light (although for normal cameras the source of noise is different).
Imagine you take several consecutive photos in those conditions; each image will be very grainy and dim, and the position of grain will vary among your many-world alternates. However, if you combine your successive photos in one, you’ll accumulate a brighter, clearer image (the more so as you add more photos). Each many-world version of you will get a different one, but they’ll converge to the same: the shape of the world’s wave-function. (Of course, the different worlds will eventually diverge in shape, too.)
You can stretch this analogy to visualize all sorts of interactions. For bright objects the re-emission is more likely to occur “towards” the outside of the object (or, inversely, electrons within bright objects tend to not communicate between themselves the news about outside). For dark objects it’s the other way around: photons are more likely to be passed among the object’s electrons rather than towards you.
Or take diffraction: A photon is emitted, passes through a screen with two holes (thus, it’s not absorbed by its electrons), and hits a wall. Even if you send photons one-by-one, they’ll still form a diffraction pattern on the wall. You can imagine it this way: the initial emission (the wave-front carrying the message) is spherical; when it hits the screen, either it’s absorbed (the message was passed to the screen), and you see nothing), or not: the message passed through both holes. But from each hole the message continues to propagate in a sphere centered on that hole. When the “message” hits the detector area, it is both these spheres that hit; depending on the difference in distance of the two paths, in some areas the two “copies” of the message can contradict each other or agree; you’ll have successful detection (a movement of an electron in the detector wall) only where the two copies agree, thus forming the interference pattern—but, for a single photon, exactly what point of the interference pattern will be hit is random.
I find that your bright room-observation and an analogy with low-light photography almost helps me grasp how come the world seems classical despite its quantum “underwear”:
Think of a (digital) photograph taken in very low light. Something like this.
Think of being in a pitch black room, and imagine your eyes are perfectly sensitive. You have a flashlight pointed away from you.
Now imagine the flashlight is very dim: it only sends one photon every few seconds, by moving one of its electrons; the electric field propagates at c as a spherical wavefront to “notify the universe” of the change. Whenever this front passes through another electron (say, of the wall before you), it may be absorbed. If it’s not absorbed, the electron does nothing (in a way, it doesn’t care that the first electron changed position). However, if it is absorbed (the two electrons exchanged a photon), then the absorbing electron now changes position to conform to the new information; doing so starts another wave-front communicating this information. Note that this second wave-front is not just going back, it’s still a spherical front starting from the wall electron. Again it starts propagating through space until it hits another electron. Suppose this last electron is used by your eye as a detector. Then you just noticed a tiny “flash” of light somewhere in your vision field.
Note that the two absorptions happen (until now) randomly. If you use just that flashlight you’ll only see random flashes in the room. More precisely, in the many-worlds interpretations, from a single train of emission-absorption-reemission-detection “events”, each you in every world will see the tiny flash in random parts of their vision field. This is both because different wall electrons would have done the absorption-reemission, and because of different electrons in your eyes would do the detection. You can extend this metaphor a bit more: in worlds where the re-emitted photon didn’t hit your eye, but (say) another electron deeper in the wall, that world’s version of you won’t notice anything. (The absorption-reemission chain will just bounce electrons and nuclei randomly throughout the wall, which just means heat.)
OK, here’s the “brightness” part: even though the absorption-reemission electron is randomly chosen by each world, not all of them are equally likely to be chosen. The wave-functions of the particles, and the interactions of those wave-functions as given by QM equations, cause the distribution of “picks” to have a certain “shape”.
Imagine that you take your flash-light and you increase its brightness; say it sends 10, then 100, then a million photons at the same time. You’ll start seeing several flashes, from random positions in your field of vision. (Each of you in the many-worlds will see the flashes coming from different places.) But the wave-function says how likely it is that you’ll see flashes from different places: even if each version of you sees different flashes, each of them will see more flashes coming from bright (white) objects than from dark (black) objects. As a result, you’ll see a grainy image of room in all worlds, even though a different one (that is, with the grain positioned differently) in each. The more photons your flashlight sends, the more “smooth” your image will be, converging on the “shape” of the wave-function. The image above shows a noisy image obtained in low light (although for normal cameras the source of noise is different).
Imagine you take several consecutive photos in those conditions; each image will be very grainy and dim, and the position of grain will vary among your many-world alternates. However, if you combine your successive photos in one, you’ll accumulate a brighter, clearer image (the more so as you add more photos). Each many-world version of you will get a different one, but they’ll converge to the same: the shape of the world’s wave-function. (Of course, the different worlds will eventually diverge in shape, too.)
You can stretch this analogy to visualize all sorts of interactions. For bright objects the re-emission is more likely to occur “towards” the outside of the object (or, inversely, electrons within bright objects tend to not communicate between themselves the news about outside). For dark objects it’s the other way around: photons are more likely to be passed among the object’s electrons rather than towards you.
Or take diffraction: A photon is emitted, passes through a screen with two holes (thus, it’s not absorbed by its electrons), and hits a wall. Even if you send photons one-by-one, they’ll still form a diffraction pattern on the wall. You can imagine it this way: the initial emission (the wave-front carrying the message) is spherical; when it hits the screen, either it’s absorbed (the message was passed to the screen), and you see nothing), or not: the message passed through both holes. But from each hole the message continues to propagate in a sphere centered on that hole. When the “message” hits the detector area, it is both these spheres that hit; depending on the difference in distance of the two paths, in some areas the two “copies” of the message can contradict each other or agree; you’ll have successful detection (a movement of an electron in the detector wall) only where the two copies agree, thus forming the interference pattern—but, for a single photon, exactly what point of the interference pattern will be hit is random.