Physics Weekly Newsletter
Physics Weekly Newsletter

Top new questions this week:

Do all the conservation laws of Physics take no time to propagate?

For instance, conservation of momentum, does it take time to propagate between two or more objects? If it does, then there would be some moment that the momentum is not conserved. If it doesn't take ...

conservation-laws faster-than-light  
asked by ayuanx 27 votes
answered by ACuriousMind 43 votes

Are Hubble Telescope Images in true color?

Like many others, I have marveled at the images made available from the Hubble Space Telescope over the years. But, I have always had a curiosity about the color shown in these images. An example is ...

astronomy telescopes  
asked by K7PEH 23 votes
answered by HDE 226868 24 votes

What is the smallest distance possible between two stars?

If two stars of any type were to form near each other, how closely can they form before something prevents them from being two distinct stars?

asked by Alex 23 votes
answered by Floris 15 votes

Conical train wheels

I've been reading about how the conical shape of train wheels helps trains round turns without a differential. For those who are unfamiliar with the idea, the conical shape allows the wheels to shift ...

homework-and-exercises newtonian-mechanics friction rotational-kinematics free-body-diagram  
asked by Rations 19 votes
answered by David Richerby 13 votes

Is an electron a superconductor?

A superconductor has zero resistance. What about an electron in a vacuum? Could this simple system be considered superconducting?

asked by Alex 16 votes
answered by sintetico 23 votes

Earth still exists - does this fact tell us anything about LHC safety?

When LHC was about to be launched there were many fears that it would destroy the world. To counter them scientists tried to carefully examine all possibilities and concluded that there is nothing ...

earth probability large-hadron-collider anthropic-principle  
asked by Simon 13 votes
answered by Chris White 28 votes

Can two colliding photons create a Higgs Boson?

The LHC discovered the Higgs using the following decay mode: $$ H^0 \rightarrow \gamma \gamma $$ This got me thinking: if we reverse this mode, will it be valid? In some annihilation/decay pairs, ...

particle-physics photons standard-model higgs  
asked by Joe Michail 6 votes
answered by David Z 11 votes

Greatest hits from previous weeks:

Relation between pressure, velocity and area

In a nozzle, the exit velocity increases as per continuity equation $Av=const$ as given by Bernoulli equation (incompressible fluid). Pressure is inversely proportional to velocity, so we have lower ...

fluid-dynamics aerodynamics  
asked by user38421 3 votes
answered by André Neves 6 votes

Does gravity exist in a vacuum?

My understanding has always been that it does from conventional science courses, but really thinking about it, I was wondering if this is really the case. To my limited understanding there is a ...

quantum-gravity vacuum  
asked by user4779 55 votes
answered by Geoff Ryan 74 votes

Can you answer these?

Is it degeneracy pressure rather than electrostatic repulsion that stops us falling through the floor?

From Wikipedia: Degeneracy Pressure Freeman Dyson showed that the imperviousness of solid matter is due to quantum degeneracy pressure rather than electrostatic repulsion as had been previously ...

electromagnetism atomic-physics pauli-exclusion-principle  
asked by Acid Jazz 4 votes

General proof of formulas of geometric optics?

In most lf textbooks formulas of geometric optics like lens maker formula and base formula for that are proven (or rather verified from my point of view) by taking specific case (ray diagram) and ...

optics conventions geometric-optics lenses  
asked by Vaibhav Patel 2 votes

Lorentz factor correction for luminosity

I am looking at the physics behind gamma ray bursts, working through a comprehensive review Kumar & Zhang (2014) (arXiv link). On page 92, Eq (111) the luminosity or a relativistically expanding ...

astrophysics gamma-rays luminosity  
asked by Tom 1 vote
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