## Top new questions this week:

### Why is it cold on the sea floor if pressure heats things?

I was reading this and it says that Microsoft put a server farm at the bottom of the ocean because it's cooler there. Particularly it seems to imply that it get's colder as you go deeper, "Since ocean ...

thermodynamics geophysics

### Cause for spikes in trinity bomb test

In Richard Rhodes' book, The Making of the Atomic Bomb, I was reading about the Trinity nuclear test. High speed photos were taken and this one is from <1ms after the detonation. The book mentions ...

experimental-physics nuclear-physics nuclear-engineering explosions

### How do stars from far away affect Earth?

I know that we obviously get light (or we wouldn't be able to see them), but are there any other ways that they affect Earth and maybe just our solar system in general?

gravity earth atmospheric-science stars solar-system

### Has Jaynes's argument against Bell's theorem been debunked?

As a student of theoretical physics I'm well acquainted with the multitude of crackpot ideas attempting to circumvent Bell's theorem regarding local hidden variable theories in quantum physics. ...

quantum-mechanics quantum-information bells-inequality epr-experiment

### Why does electric force depend on the medium?

Comparing the equations for the gravitational and electric force $$\vec{F}_g=-\frac{Gm_1m_2}{r^2}$$ and $$\vec{F}_e=\frac{Kq_1q_2}{r^2}$$ I noticed the only major difference between them is that ...

forces electrostatics newtonian-gravity

### Basis independence in Quantum Mechanics

The idea that the state of a system does not depend on the basis that we choose to represent it in, has always puzzled me. Physically I can imagine that the basis ought to just yield an equivalent ...

quantum-mechanics hilbert-space vectors

### Is it known what the necessary and sufficient conditions are for the existence of a "3+1 split" (by means of a foliation) of a (Lorentzian) manifold?

When trying to do physics on a more general pseudo-Riemannian manifold we want to require that there is a foliation of this manifold into three-dimensional subspaces. By this I mean we would like to ...

spacetime differential-geometry field-theory

## Greatest hits from previous weeks:

### Why does ice have a lower density than water?

Can someone explain me why is ice less dense than water? As I know, all solids are usually denser than the liquids (correct me if I am wrong).

water physical-chemistry crystals density ice

### With Newton's third law, why are things capable of moving?

I've got a rather humiliating question considering newton's third law "If an object A exterts a force on object B, then object B exerts an equal but opposite force on object A" -> $F_1=-F_2$ ...

newtonian-mechanics forces free-body-diagram faq

## Can you answer these?

### Reading differential forms

When, usually in text of physics or concerning thermodynamical aspects of chemistry, I find notations such as$$\mathrm{d}f=g\,\mathrm{d}t$$ I always interpretate it as ...

thermodynamics mathematics

### how to construct self-energie diagrams

I am working on self-energie and feynmann diagrams. they are not very easy to get but i think i am starting to understand how it works but of course i am not realy sure.and before going any further i ...

feynman-diagram many-body self-energy