Physics Weekly Newsletter
Physics Weekly Newsletter

Top new questions this week:

What enables protons to give new properties to an atom every time one is added?

How does adding one more particle to the nucleus of an atom give that atom new properties? I can see how it changes it's mass, that's obvious... But how does it give that new atom different properties ...

atoms proton  
asked by Investor 40 votes
answered by BjornW 51 votes

Is there a thermodynamic limit on how efficiently you can solve a Rubik's cube?

Suppose I build a machine which will be given Rubik's cubes that have been scrambled to one of the $\sim 2^{65}$ possible positions of the cube, chosen uniformly at random. Is it possible for the ...

statistical-mechanics entropy information landauers-principle  
asked by Mark Eichenlaub 33 votes
answered by Nathaniel 30 votes

If air cannot conduct electricity, how can lightning happen?

If air cannot conduct electricity, how can lightning happen?

electricity air lightning  
asked by hemazy percy 22 votes
answered by Kieran Hunt 32 votes

If the solar system is a non-inertial frame, why can Newton's Laws predict motion?

Since there is no object in the universe that doesn't move, and the solar system likely accelerates through space, how did Newton's Laws work so well? Didn't he assume that the sun is the ...

newtonian-mechanics reference-frames solar-system inertial-frames approximations  
asked by Haresh 11 votes
answered by MSalters 13 votes

If the Einstein Field Equations are so hard to solve, how did Einstein know they were correct in the first place?

Consider a formula like $y = mx + b$. For instance, $y = 2x + 3$. It is simple to check that $(1,5)$ is a solution, as is $(2,7)$, as is $(3,9)$, etc. So it's easy to see that $y =2x + 3$ is a useful ...

general-relativity  
asked by Stan Shunpike 9 votes
answered by John Rennie 21 votes

What exactly do we mean by symmetry in physics?

I'm referring here to invariance of the Lagrangian under Lorentz transformations. There are two possibilities: Physics does not depend on the way we describe it (passive symmetry). We can choose ...

quantum-field-theory symmetry group-theory lorentz-symmetry  
asked by JakobH 9 votes
answered by Uldreth 2 votes

Gay-Lussac's Law & the Patriots

This may be a question better suited for xkcd what if? section...but here goes: with all the hoopla around the patriots / colts game and allegations of cheating by deflating footballs, I've read/heard ...

pressure temperature ideal-gas  
asked by Bryan Eslinger 8 votes
answered by Kyle Kanos 4 votes

Greatest hits from previous weeks:

Why a glass rod when rubbed with silk cloth aquire positive charge and not negative charge?

I have read many times in the topic of induction that a glass rod when rubbed against a silk cloth acquires a positive charge. Why does it acquire positive charge only, why not negative charge? It ...

electrostatics electricity  
asked by Manisha 6 votes
answered by Lagerbaer 7 votes

I don't understand what we really mean by voltage drop

This post is my best effort to seek assistance on a topic which is quite vague to me, so that I am struggling to formulate my questions. I hope that someone will be able to figure out what it is I'm ...

voltage resistance  
asked by oyvey 14 votes
answered by RedGrittyBrick 15 votes

Can you answer these?

Trilinear term in SUSY soft-breaking

In MSSM soft-SUSY breaking, there are such term called 'A-triliear term'. But, some papers, e.g Riva-Biggio-Pomarol, do not have trilinear term. What is the use of introducing trilinear term?

quantum-field-theory particle-physics supersymmetry symmetry-breaking  
asked by Panuluh 2 votes

Time reversal in classical electrodynamics

It is known that classical electrodynamics is time reversal invariant if one assumes that the transformation laws under such operation are $$\mathbf E(t,\mathbf x)\mapsto\mathbf E(-t,\mathbf x)$$ ...

special-relativity classical-electrodynamics time-reversal  
asked by Phoenix87 5 votes

How can we measure chirality in experiments?

Chirality is a concept quite different from helicity. These two concepts only happen to have the same numerical value for massless particles. I understand that we can measure helicity, but how can we ...

quantum-field-theory spin group-theory chirality helicity  
asked by Tim 2 votes
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