Recent content by Green dwarf

Thank you. That's a new idea to me - some localisation. Going back to my original question about the photon, would the same apply there, so that all directions are not equally probable?

Thanks DrClaude. Presumably all particles interact constantly with gravity. Would that mean that they are always localised?

Let's say a uranium atom floating in space emits an alpha particle. Presumably, the alpha particle travels in a superposition of all possible directions until it is detected. (I'm guessing that a 'detection' can be an interaction with another particle, not just an interaction with a conscious...

Thank you DrChinese. Your answer makes sense. If, instead of emitting a photon, the electron is knocked out, does the electron travel on all directions too? Would the same be true of the proton? What about a larger atom or a molecule or a speck of dust or a pebble?

If a lone hydrogen atom in space emits a photon, is it emitted in a particular direction or in a superposition of all directions?

Thank you everybody for your responses. As I expected, the situation is much more complicated than the simple model I was imagining. I really don't understand general relativity and probably never will. At 70 years of age, I'm probably better suited to growing beans in my vegie patch. I do run...

Thanks Dale. I'm wondering too, would there be any truth in the idea that the matter in a black hole would form a thin shell on the event horizon because matter falling in would stop there (from an outsider's perspective)? One might think that as the black hole grows, matter inside it would then...

I'm wondering is whether it is the gravitational potential (in J/kg) at a point in space that determines the rate of passage of time, or whether it is the gravitational field strength (in m/s2). To clarify, suppose you had a very heavy hollow spherical shell. The gravitational potential would...

Thank you vanhees71. Can I ask a further question? My understanding is that a wave function could in theory be defined for the whole universe and that this function evolves in a deterministic way. Does that mean that the uncertainty in the system doesn't increase over time? The alternative being...

My understanding of quantum theory and information theory is that, given complete information on the state of the universe at present, it is possible to predict its state at all times in the future and past. 3 questions: 1: is this true? 2: how are quantum-probabilistic outcomes accounted for...

Thank you everyone. Being a science teacher and not a physicist, I have been influenced by science textbooks for school kids which tend to classify energy, though I have never been quite comfortable with the classifications offered. Hence my initial question. It's actually quite a novel idea to...

Thanks PeroK. I read through the article, but the only mention of mass energy was this: Finally, associated with the relativity theory, there is a modification of the laws of kinetic energy, or whatever you wish to call it, so that kinetic energy is combined with another thing called mass...

Thanks for your replies. Still not sure of the answer though. Demystifier says: No, you can think of mass as a kind of potential energy. Though I'm not sure of the reasoning behind that. robphy seems to imply that mass is neither KE nor PE. The video suggested by PeroK includes a diagram...

I am planning to teach a school astronomy group about energy. Most people seem to accept that there are two types: kinetic energy, resulting from movement; potential energy, resulting from position in a force field with a potential gradient (convertible to KE if the object is allowed to move...

My understanding is that the repulsion between two electrons is mediated by the exchange of virtual photons – virtual meaning not lasting long enough to be detected. But suppose one of the electrons is in the sun and the other on Earth. There should still be a repulsion because the...