Physics Weekly Newsletter
Physics Weekly Newsletter

Top new questions this week:

Does time move slower at the equator?

While answering the question GPS Satellite - Special Relativity it occurred to me that time would run more slowly at the equator than at the North Pole, because the surface of the Earth is moving at …

special-relativity time-dilation  
asked by John Rennie 33 votes
answered by Luboš Motl 25 votes

If there were fundamental forces weaker than gravity, would we know about it?

We know that gravity is a very weak force compared to electromagnetic forces and the nuclear forces. We know about the other forces because they're necessary to explain atoms, and we can detect …

asked by Nathaniel 26 votes
answered by Luboš Motl 14 votes

Why isn't the sunset/sunrise rainbow-colored

When the sun is rising/setting, it goes through a phase where the light is bending from the atmosphere. I believe this image will explain much better than I ever could. Now, if light goes through …

visible-light everyday-life sun refraction  
asked by David Starkey 22 votes
answered by Joshua 15 votes

The physical definition of work seems paradoxical

So this is possibly a misunderstanding of the meaning of work, but all the Physics texts, sites, and wiki that I've read don't clear this up for me: In the simplest case with the simplest statement, …

newtonian-mechanics forces work definition biophysics  
asked by Addem 20 votes
answered by Luboš Motl 32 votes

Why is the pressure inside a soap bubble higher than outside?

Apparently, the air inside a soap bubble is under higher pressure than the surrounding air. This is for instance apparent in the sound bubbles make when they burst. Why is the pressure inside the …

pressure air surface-tension  
asked by David Zwicker 15 votes
answered by David 22 votes

How would an X-ray scanner identify a mirror?

A mirror is normally used to reflect Electromagnetic radiation also known as photons (light) and in airport security or medical facilities, they use X-rays to detect anomalies inside objects or bodies …

electromagnetic-radiation everyday-life x-rays  
asked by Rohan Vijjhalwar 15 votes
answered by dmckee 28 votes

Why do bubbles make a sound?

I have an understanding of how bubbles work. They encapsulate air (or other fluids) in a membrane caused by surface tension. When they pop, there is often a sound. Sound is a type of energy, kinetic …

everyday-life acoustics pressure air  
asked by Thoth19 14 votes
answered by David Zwicker 16 votes

Greatest hits from previous weeks:

Does centrifugal force exist?

Currently in my last year of high school, and I have always been told that centrifugal force does not exist by my physics teachers. Today my girlfriend in the year below asked me what centrifugal …

newtonian-mechanics reference-frames centrifugal-force centripetal-force  
asked by Dylan Cleaver 44 votes
answered by Venemo 44 votes

Why can Hiroshima be inhabited when Chernobyl cannot?

There was an atomic bomb dropped in Hiroshima, but today there are residents in Hiroshima. However, in Chernobyl, where there was a nuclear reactor meltdown, there are no residents living today (or …

nuclear-physics radiation biophysics isotope  
asked by user14154 43 votes
answered by Jim 30 votes

Can you answer these?

Why is Silver-108 unstable

Why is Silver-108 unstable if silver-107 and silver-109 are stable? I found it on crash course but no answer was given.

asked by user43087 3 votes

Is Romer's letter on our search for the elementary proof of the spin-statics theorem out of date today?

The following link provides a letter to the editor by Robert H. Romer who writes, In a 1994 "question" in this journal, Neuenschwander asked whether anyone had yet met Feynman’s challenge of …

quantum-field-theory spin-statistics  
asked by linuxfreebird 5 votes

Instantons in Witten's supersymmetry and Morse theory

I'm reading Witten's paper on supersymmetry and Morse theory and am confused about the details of the instanton calculation which he uses to define a Morse complex (beginning at page 11 of the pdf) . …

quantum-mechanics mathematical-physics differential-geometry supersymmetry instantons  
asked by user247679 2 votes
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