Physics Weekly Newsletter
Physics Weekly Newsletter

Top new questions this week:

How can ants carry items much heavier than themselves?

This morning I saw an ant and suddenly a question came to my mind: how do ants actually carry items much heavier than themselves? What's the difference (in physics) between us and them?

asked by Paul 50 votes
answered by altac bori 56 votes

Why isn't length contraction permanent even though time dilation is?

It's my understanding that when something is going near the speed of light in reference to an observer, time dilation occurs and time goes slower for that fast-moving object. However, when that ...

special-relativity time-dilation length-contraction  
asked by theboombody 37 votes
answered by hraish kumar 24 votes

What are galactic speeds measured against?

The Earth moves through space at 67,000 MPH. The Milky Way travels through a local group at 2,237,000 MPH. Wouldn't you need a fixed point to be able to measure velocity against? After all, compared ...

cosmology reference-frames galaxies relative-motion  
asked by Sean Long 27 votes
answered by John Rennie 27 votes

In reverse time, do objects at rest fall upwards?

I want to develop a game where time runs backwards, based on the idea that physical laws are reversible in time. However, when I have objects at rest on the earth, having gravity run backwards would ...

gravity time-reversal  
asked by Konrad Höffner 25 votes
answered by BMS 32 votes

I touched a tree that was touching an electric fence and got an electric shock. How is this possible if wood is an insulator?

I touched a tree that was touching an electric fence and got an electric shock. How was this possible if wood is an insulator? The tree wasn't wet either, and it was a pretty strong shock too.

electricity insulators  
asked by Ray Kay 24 votes
answered by Rob Jeffries 27 votes

How does light speed up after coming out of a glass slab?

As I learned today in School, my teacher told me that when light enters a Glass Slab it slows down due to the change in density and it speeds up as it goes out of the Glass Slab. This causes a lateral ...

optics visible-light speed-of-light energy-conservation refraction  
asked by Amey Shukla 24 votes
answered by WetSavannaAnimal aka Rod Vance 41 votes

Conservation of momentum when rain pours into a wagon

Suppose a wagon is moving at constant velocity on a friction-less surface, and rain begins to fill the wagon. The net force on the wagon is zero, so momentum is conserved; as the mass of the wagon ...

newtonian-mechanics forces momentum conservation-laws  
asked by Joshua Benabou 18 votes
answered by User58220 45 votes

Greatest hits from previous weeks:

Why less temperature at high altitude

Why there is always cold at high altitudes. e.g. at peak of mountains. Also as we go high from sea level, temperature starts decreasing. Why is it?

temperature atmospheric-science  
asked by android developer 10 votes
answered by gerrit 6 votes

Why doesn't matter pass through other matter if atoms are 99.999% empty space?

The ghostly passage of one body through another is obviously out of the question if the continuum assumption were valid, but we know that at the micro, nano, pico levels (and beyond) this is not even ...

particle-physics electrons atomic-physics collision matter  
asked by Bryson S. 69 votes
answered by ACuriousMind 109 votes

Can you answer these?

Does the surface of austenitic steels have an especially "dynamic" phase somewhere between 100 and 200 Celsius?

There is lots of kitchen lore about pans. One popular concept are the "pores" of a steel pan surface, which are the reason why food sticks to the pan when it's not heated properly. I don't know much ...

temperature material-science  
asked by rumtscho 2 votes

temperature of electroweak phase transition

How does one estimate the temperature at which electroweak phase transition (EWPT) occurred? Somewhere I have read it is around 100GeV but the reason was not explained.

cosmology electroweak baryogenesis leptogenesis thermal-field-theory  
asked by SRS 3 votes

Is there a textbook which covers QM via Geometric Algebra (GA)?

There is at least one good book on classical mechanics using Geometric Algebra (GA): New Foundations in Classical Mechanics by David Hestenes. Likewise there is at least one good book on classical ...

quantum-mechanics resource-recommendations clifford-algebra  
asked by got it--thanks 5 votes
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