Physics Weekly Newsletter
Physics Weekly Newsletter

Top new questions this week:

Can a human size object move so fast that it ceases to be observable?

In many anime, comics, movies, etc, we see a lot of super human beings moving and fighting at such high speeds that a regular human being cannot see that they are fighting or moving pass by. In …

speed vision  
asked by user1948847 19 votes
answered by Jim 24 votes

Why should any physicist know, to some degree, experimental physics?

I've been trying to design a list with reasons why a proper theoretical physicist should understand the methods and the difficulty of doing experimental physics. So far I've only thought of two …

experimental-physics soft-question  
asked by PML 15 votes
answered by Danu 35 votes

A force opposing Gravity

Every Action Has An Equal and Opposite Reaction (Newton's Third Law.) If this is the case, does gravity have an equal-opposing force? From asking around I still haven't got a very clear answer; …

newtonian-mechanics newtonian-gravity  
asked by Harry David 13 votes
answered by Emilio Pisanty 16 votes

Is the Standard Model consistent (UV complete)?

This is a question about the self-consistency of the Standard Model - which I believe is the same as asking whether it is UV complete - in other words, can it be used to predict experimental results …

quantum-field-theory standard-model  
asked by akrasia 12 votes
answered by Luboš Motl 11 votes

A Sphere of Black Holes

Imagine a sphere of black holes surrounding a piece of space. Will this piece be separated from the rest of normal spacetime (at least for some time, till these black holes finally attracted …

black-holes spacetime  
asked by draks ... 10 votes
answered by John Rennie 16 votes

How to tell whether photons are entangled?

Suppose you have some sort of a "black box" system - you know nothing of its inner workings. The system has two outputs, let's call them A and B, and it occasionally emits photons - one photon from …

quantum-mechanics photons entanglement polarization  
asked by EigenCat 9 votes
answered by Mr.WorshipMe 1 vote

How do you add temperatures?

This will probably be considered very simple, but I am just a beginner: I'm developing a software application where temperatures need to be added and subtracted. Some temperatures are in Celsius, …

asked by Peter 8 votes
answered by Luboš Motl 19 votes

Greatest hits from previous weeks:

If photons have no mass, how can they have momentum?

As an explanation of why a large gravitational field (such as a black hole) can bend light, I have heard that light has momentum. This is given as a solution to the problem of only massive objects …

special-relativity electromagnetic-radiation photons mass momentum  
asked by david4dev 47 votes
answered by Noldorin 31 votes

If I'm floating in space and I turn on a flashlight, will I accelerate?

Photons have no mass but they can push things, as evidenced by laser propulsion. Can photons push the source which is emitting them? If yes, will a more intense flashlight accelerate me more? Does …

photons energy-conservation acceleration space-travel  
asked by Hello World 42 votes
answered by John Rennie 60 votes

Can you answer these?

How does bulk-boundary correspondence works for various cases of time-invariant system?

I was pondering this question after I read this review: M. Zahid Hasan and Charles L. Kane. “Colloquium: topological insulators.” Reviews of Modern Physics 82, no. 4 (2010): 3045. (arXiv) How do …

asked by Maz 2 votes

Which way to lean when driving a gokart?

Given a car that has two lines of wheels, the center of gravity at constant height above the ground, constant turn angle and given surface and wheel material. What is the maximum speed the car can …

asked by Kuba 2 votes

How to find tension in the cantilever brakes?

In the left side example of cantilever brakes, how do I find the tension in strings DE and DC, in terms of T. According to me applying force balance equations, horizontal and vertical forces should …

homework newtonian-mechanics  
asked by Manish 3 votes
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