4 ms·
I think the simple thought experiment is: Imagine the famous two slit experiment. In this version we will fire electrons at the slits, one at a time. Put a ver
by abainbridge 8y ago
I think the simple thought experiment is:
Imagine the famous two slit experiment. In this version we will fire electrons at the slits, one at a time. Put a very accurate spring balance behind each slit and measure the gravitational attraction of the electron as it goes past.
The author then claims, "The description that General Relativity puts forth ... needs to be augmented to include an uncertain position that has a probability distribution to it."
Does that follow? Wouldn't, say, the Pilot Wave Theory avoid the need for GR to change?
- BlackFly 8y agoYes, this is my thought as well. It simply does not follow that the two alternatives are a probabilistic stress energy tensor or a violation of the uncertainty principle. Since quantum mechanics describes electrons as a field and not as a particle with position and momentum, there is always the possibility that an extension to the field or a function of the field itself can generate a classical stress energy tensor.
- teilo 8y agoYes, but that doesn't solve the problem. That is just another way of rephrasing the problem. A stress-energy tensor is still dependent upon position and strictly speaking is not a thing in itself, but a mathematical description of an thing/effect - in this case a graviton field or equivalent which is associated with the higgs field of a particle in superposition. The result will always be described via a stress-energy tensor, but this is a description of a result, not a cause. However this works out, we still have to deal with the "position problem" when it comes to describing the gravitational field of a particle.
- scotty79 8y agoWhat if particles affect spacetime only when they interact?
- justifier 8y agothere are a couple definitions you would need to elaborate on to realise this question fully by particle physicists usually mean any electromagnetic phenomena that seems to have distinct energy levels and so can refer to any number of things depending on context: photons, electrons, protons, atoms(o) as for interact, what do you mean by this? would you consider entanglement an 'interaction'? the idea of a wavefunction is basically that every particle is 'interacting' with every other particle in existence in every direction with potential of collisions being discernible by the probabilities of the particle's position being spread out ad inifinitum according to relativity light has a constant speed, meaning it is always moving at 'c' since the photon is moving it has energy and though it has a 'rest' mass of 0 it is without a rest frame because it is always moving at that constant speed and so always has some measurable mass because of this even in a universe with only a single photon without anything to interact with the photon would still affect spacetime if you remove the 'only' from your question then the answer is an emphatic yes because you yourself are a collection of 'particles' 'interacting' and you are affecting spacetime (o) https://physics.stackexchange.com/questions/146975/is-a-photon-really-massless https://physics.stackexchange.com/questions/146975/is-a-phot...
- scotty79 8y ago> by particle physicists usually mean .. photons, electrons, protons, atoms(o) I meant pretty much anything that can be described by wave function evolving according to Schrodinger equation. > as for interact, what do you mean by this? Exchange of energy through any of 3 physical forces (not gravity). So not entanglement. Single photon universe would never be observed so it would have wave function but never have specific location so according to my idea it would not affect spacetime.
- konschubert 8y agoAlso, I don't think we will get very far by trying to attach gravity to QM on the level of probabilities. You will want to connect them on a field level obviously. The probabilities are jusy a crutch that link the quantum world to our perceptions.
- codethief 8y agoI don't think the author ruled out a field-theoretic description (whether as a quantum field or as a classical field). But using the language of fields and talking e.g. about the precise coupling between gravity and other quantum fields doesn't add anything to the discussion here. The question is whether the gravitational field behaves in a quantum mechanical fashion (and thus allows for superpositions) or not. To ponder this, you don't need fields. It's a completely separate issue.
- konschubert 8y agoThank you, I may have a bad understanding here.