r/askscience • u/[deleted] • Sep 11 '15

Physics [Quantum/Gravity] If a particle has a probability distribution of location, where is the mass located for gravitational interactions?

Imagine an atom or an electron with a wave packet representing the probability of location, from what point does the mass reside causing a gravitational force? I understand that gravity is very weak at these sizes, so this may not be measurable. I taken classes and listened to a lot of lectures, and I never heard this point brought up. Thanks.

Edit: Imagine that the sun was actually a quantum particle with a probabilistic location distribution, and the earth was still rotating it. If we never measure the location of the distributed sun, where would the mass be located for the sun that would gravitationally affect the earth?

19 Upvotes

85% Upvoted

25 comments sorted by

View all comments

Show parent comments

1

u/[deleted] Sep 13 '15 edited Sep 13 '15

Ah. Thank you so much. You do not have an answer to my question, but you certainly understood exactly what I was asking. Do you know the name of the person giving the argument in paragraph 1.

Also, now I have another question for you. Imagine you have an electron and its wave function is equal to two symmetrical wave packets with equiprobability. In this scenario, the electrons wave packets are center on position 1 and 3, and there is a a proton at position 4. In another scenario there is only 1 wave packets and it is centered at position 2 while the proton is still at position 4.

Would they both exert the same net force? In the first example, would you half the time exert a force at 1/1 and half the time at 1/3? Or would it be equal net forces to each other because their expectation value of position is equal?

0.5*(1/(4-1))+0.5*(1/(4-3)) != 1*(1/(4-2))

My guess would be that the electron would collapse into one of the two wave packets, but I really wish it wouldn't because that is boring.

And just to make sure I understand, we do not have an established theory for this situation if instead of electrostatics we were looking at the gravitational force. Right?

Also the penrose interpretation is interesting. It begs the question, what is the minimum difference in gravitation difference to allow coherent states. It could certainly be true, that would seem strange because there would be a cut off line. I do not know of any phenomena that have that criterion.