05 Sep 10
1 edit
Originally posted by twhiteheadBefore the advent of quantum theory, light was regarded by most as waves (and not particles) - electromagnetic radiation follows from Maxwell's equations, derived in the 19th century. It was Planck in the early 20th century who showed that light must be quantized in order to explain the black body radiation spectrum.
Am I mistaken, or is the wave nature of light (and other electromagnetic radiation) a direct consequence of quantum physics? ie without quantum physics, light should act like particles only.
05 Sep 10
Originally posted by Andrew HamiltonThanks! It really seems like a fascinating field. And no, I had no idea quantum physics played such real life roles modern technology.
If quantum physics was just pie-in-the-sky then the semiconductors in your computer would not work nor the lasers that send signals for your message down fibre-optic cables and you would not be able to post the message: “…The impression my uneducated mind gets from watching the science channel is that quantum physics is a bunch of pie-in-the-sky - a ...[text shortened]... be dead! Much of chemistry can only be fully explained by taking into account quantum effects.
So what distinguishes quantum physical from plain vanilla physics?
06 Sep 10
Originally posted by USArmyParatrooperQuantum physics revolves around the idea that certain physical properties (energy, angular momentum, charge, etc.) only come in discrete chunks, rather than have all possible values.
Thanks! It really seems like a fascinating field. And no, I had no idea quantum physics played such real life roles modern technology.
So what distinguishes quantum physical from plain vanilla physics?
06 Sep 10
Originally posted by USArmyParatrooperWhat you refer by “plain vanilla physics” 🙂 can be taken to mean Newtonian physics.
Thanks! It really seems like a fascinating field. And no, I had no idea quantum physics played such real life roles modern technology.
So what distinguishes quantum physical from plain vanilla physics?
Newtonian physics is generally fine for just giving accurate enough predictions of physical behaviour of most things around us excluding the very small and excluding certain extreme conditions such as what happens when something travels close to the speed of light.
But Newtonian physics completely fails to take into account or predict the weird behaviour of the very small. For that you really need quantum physics because quantum physics is about describing that strange behaviour of the very small that simply does not behave in a “Newtonian “ way. Without quantum physics you cannot explain nor predict, amongst numerous other things, that light is made of “photons” that have both particle-like behaviour and wave-like behaviour nor would you be able to explain the unpredictability of the motion of electrons and atoms.
06 Sep 10
Originally posted by USArmyParatrooperThat's another weird physics thing, that the universe as a whole can be bubbling up faster than the speed of light but stuff inside is not. The universe expanding and a galaxy are two different animals.
Is that a contradiction? If that's the case then we're all moving faster than the speed of light.
The gravity of galaxies, dark matter and regular matter, holds stuff together gravitationally so we won't be expanding due to self gravitational attraction. The universe as a whole has no such constriction.
You could visualize the expansion as if each point in the universe was populated by reproducing paramecium, if you ever see them reproduce, they just fission apart, so the universe as a whole has this feature too, its like 'space' and 'time' gets pumped in point by point, a new point popping up between the old points crowding the old points apart, thus expanding.
That effect, however, has no connection on Earth, we are not expanding the same way, we are not getting bigger along with the galaxy or the Earth unknowingly getting to huge proportions, it doesn't work like that.
The universe has its thing, we have ours and it doesn't include getting forever larger all together so we don't notice. We stay the same size while the universe as a whole gets its little points pumped in continuously.
07 Sep 10
Originally posted by USArmyParatrooperBroadly speaking, relativity theory permits "things" to move faster than light provided they do not carry "information" (e.g. a force) faster than light. This is how it is possible for quantum entanglement to (judging by measurements) instantaneously react to the other entangled particle to be "measured".
Is that a contradiction? If that's the case then we're all moving faster than the speed of light.
08 Sep 10
Newtons laws of motion help us understand the movement of solid objects. They are quite intuitive and fairly easy to visualize. But they do nothing to help us understand things like magnetism and electromagnetic radiation. Although those too can be visualized and things like Maxwell's equations can help us understand them, it always remains rather mysterious to see magnetism pass right through things.
I have a toy, where you spin a magnetic top over another magnet and it hovers in the air. You can pass a piece of paper between them and even a finger and they seem unaffected. Sure you can know the science, but it just seems weird that there is this invisible force that you can pass your hand right through without feeling it at all.
08 Sep 10
Originally posted by KazetNagorraIs reaction possible without any new information?
Broadly speaking, relativity theory permits "things" to move faster than light provided they do not carry "information" (e.g. a force) faster than light. This is how it is possible for quantum entanglement to (judging by measurements) instantaneously react to the other entangled particle to be "measured".